1/16 Scale RC Truck parts

[ddmckee54]

I am fascinated with RC construction equipment.  Being a cheapskate somewhat frugal, I cannot justify paying way more for something I can play with, than I paid for my first car/s.  I don 't have the skills/talent to be able scratch-build, but I can kit-bash pretty well. (And I've got a couple of 3D printers.)  With that in mind I set about collecting Bruder construction toys for RC conversion, as retirement projects.  Why Bruder toys?  They're all 1/16 scale, reasonably accurate to scale, almost indestructible, and sorta cheap - at least when compared to their 1/14 scale cousins.  I have a set of shelves in the basement that would be the envy of many a kid.  Retirement arrived at the end of last month, so it's time to set things in motion.

In true MadModder tradition I decided to see what I could Frankenstein together from cheap Chinese clones of other RC car/truck parts.  I have 4-5 Bruder trucks, that will ALL require front axles, center differentials, rear differentials, wheels and tires.  I knew that the differentials would be a major road block.  I looked at what was available, drooled all over my chin because of the detail, then said - no flippin way am I paying $200 per axle.  I found a 1/12 scale Kong rear diff that looked like it MIGHT work.  Ebay to the rescue and for $40 I had one in my hands.  It would work, but only as the rear axle, as a center diff they are un-obtainium.  Thusly the Frankendiff was born.  I decided to start with a 1/10 scale crawler rear axle from WPL.  Why that axle?  Well they're cheap, about $20, and "mick thebass" used them in his RC conversion of Bruder's Ausa dumper.  I started 3D modeling an axle housing for the WPL axle that would at least sorta resemble the Kong axle.  This was the first working version, it only took 9-10 tries to get to this point.


Yeah, I know, it sorta looks like something you could build with Tinker-toys.  That led to this version:

At least it looks less like a Tinker-toy construction and more like the Kong axle - doesn't actually work though.  Although, neither do the WPL axles when you first get them.

This is the first version that actually works, almost correctly.  It still binds a little at one point, but I think that's in the spider gears.  The next image shows the metal Kong axle, my axle, and SOME of the various failures.  I took the rear cover off my axle to show a correction I had to make to the housing.  I had to create a place to add 2 more screws to hold the housing halves together.  The actual rear cover is the one with the shiny bit in the second row, (the shiny bit is the drain plug.)  Up in the upper RH corner is my first, and last, attempt at a 3 part front wheel - hub, wheel, and hub cover.  Those M2 screws are just too fiddly to install while trying to line up those itty-bitty holes in 3 parts.  You need a lot less hands when the wheel and hub are 1 piece.

This takes care of the differentials.  The center diff is the same as the rear diff, it's just got a pinion housing on both the front and rear halves of the diff.  I still need to shorten the axle shafts, re-dill for the drive  pins, and re-thread the ends M4.

I've already shown you the front wheels, on to the rear wheels.

The doo-dad on the right is the locknut cover, the screws that hold it on will simulate the lug nuts.  On each side of the wheel are parts that failed for one reason or another.  This wheel is actually also a failure, the gap between the tires was too wide.  The wheels in the next picture are also failures.  These measure 200mm from outside to outside.  I need to be at around 185mm, so I need to find a place where I can take 7-8mm out of each side.  I can take another 2mm out of the gap between the tires, and change the wheel offset by 5mm-ish and that should get me close enough.


The tires are Lesu 1/16 scale "narrow" tires, they're fairly cheap - about $15 a pair.  They are also close to the OD of the Bruder tires, about 2-3mm smaller and I can live with that.  The 1/14 scale tires are about 10-15mm larger, and cost significantly more.  I've only got 2 of the "narrow" tires now.  I've got 2 of the Lesu "wide" tires too, but they are only about 1-2mm wider, cost about $5 more a pair, and take a different wheel profile.  Nope, gonna stick with the the narrow tires for now, thank-you-very-much.

Don

[RussellT]

I admire your persistence Don. With patience and persistence everything is achievable.

Wouldn't it be nice if it was easy to recycle failed prints into usable filament.

Russell

[BillTodd]

Nice work 

I wonder if you could use cheap angle grinder bevel gears ? 

[Brass_Machine]

Very cool...

dont I love 3D printing...

[ddmckee54]

Bill:

I think those gears would probably be too big.  The ring gear in my diff has got a 25mm OD, the pinion gear is 10.5mm, and the spider gears are even smaller.  I suspect that when I do tear the diff apart to shorten the axles I'll find the jagged ends of the sprue on one or more of those gears.

I redesigned the rear wheel last night.  Between reducing the gap between the tires and changing the wheel offset I took a total of 14mm off the overall width of the rear axles.  Unfortunately that means I probably won't have enough room to hang the springs off the side of the frame rails. They'll have to go under the rails, right about where the angled transition starts.  So, I guess I'll be moving that too.

Don

[tom osselton]

Have you tried the hobby shops for the crown and pinion? The one in Calgary has all different sizes.

[ddmckee54]

Tom:

I used to try the LHS first.  In my area though they have gone the way of the Dodo.  All that's left is Hobby Lobby and Michael's.  Aside from the fact they're 45 miles away, they are more suited to crafters.  If I want something I have to go on-line.

Don

[ddmckee54]

Progress HAS been made!  This is a family photo of the gang - so far.


From back to front on the left side are:
1)  The Kong axle with the modified rear wheels.  I got my order of tires, so I can actually put tires on everything now.
2)  The modified Frankendiff, still haven't shortened the axles though.
3)  The prototype of the front axle - it still needs work.  It's only got one wheel mounted because I don't have any more 5x9x3mm ball bearings.  They are on order, should be here this week?
4)  The other front wheel, with hub cover just laying in place. 

On the right side are the next donor diff, and the left-overs from the donor front axle.

I've redesigned the rear axle's front and rear halves, making some minor tweaks. 
1)  I moved all the case mounting screw locations away from the axle bore,  They were close enough to the bore that when the screws were threaded in, the inner wall would expand into the axle bore and bind on the axle.
2)  I changed the angled transition to allow a convenient spot to bolt the springs to the axle.
3)  I took the donor diff apart to see if the binding that I feel was coming from the spider gears - it was/is.  There's no clearance in the gears.  In fact if the screws that hold the spider gears cover in place are tightened down, you can completely lock-up the differential.  When I shorten the axles I'll take a little off the back side of the gears.  That should make things work a little better. 

The front axle needs a little help yet - it's 10mm too narrow.  When I initially designed the front axle the plan was to use the steering arms, spindles and king-pins from the donor axle, which measured 205mm outside to outside.  I need 175mm-ish, so I had to take 30mm out of the axle.  The donor axle had spring perches that are spaced 80mm apart, which is right where I need them, but I need to lose 30mm somewhere.  So I played with the design a while.  This looked kinda OK on screen, so I printed it out.  When I started to install the spindle assembly into the axle the spindle would flop around in the steering arm, they allowed PLENTY of clearance in this one Clarence!  So, I am NOT going to use the original steering arms.  While designing the new arms I came up with the idea of changing the front wheel offset by 5mm, to tuck the steering knuckle into the back of the wheel - so I did that too.  And that my friends is why the front axle is 10mm too narrow.  It's a simple fix and the axle only takes about 1/2 hour to print.

Unfortunately the "Bag of Misfit Parts" continues to grow.

Don

[ddmckee54]

My 5mm ball bearing order arrived, so I put both front wheels on the axle.  Here's a shot that shows a comparison of the overall widths of the axles.


Well....  The rear axle is pretty close, and there's less than 1mm difference between my red axle and the silver Kong axle.  But the front axle - not so much, the front axle didn't work exactly as planned.  You know the old joke about cutting something off twice and it's still too short?  Well, I printed the axle twice and IT'S still too short!  Only this time I don't think that it's all my fault.  I noticed that the display on my 8" caliper will periodically jump 5-10mm.  All of the outside to outside measurements on the wheels are over 150mm, so I've got to use the 8" caliper.  It's a Harbor Freight special, so we'll see how good the lifetime warrantee actually is.

Here's a shot that shows the size of the Lesu tires compared to the Bruder tires. 


This will probably be the first conversion victim.  This will be one of the simplest, as in addition to forward/reverse and left/right, it will only require the drum to turn.(And maybe lights?)

Don

[ddmckee54]

Well HF would have replaced the 8" caliper, but they didn't have any, none within 100 miles.  Soooo...  I ordered an 8" Mitutoyo. 

I added another 10mm to the width of the front axle, but it's about as far as I can go with it until some more little doo-dads get here.

While I'm waiting on more bits and pieces too arrive, I've started working on the rear suspension.  I'm planning on making something like a Hendrickson Walking Beam suspension.  I downloaded some of their tech info, and it's got enough illustrations that I think I've got a pretty good handle on how things should go together - time will tell.  I've had to make some minor changes to my differential housings, to add locations for the equalizer beam brackets and the torque rod bracket.  When I'm far enough along to start printing out pieces I'll show you what I came up with.

Don

[Rester]

Love the ingenuity with the Frankendiff, definitely beats dropping $200 per axle. Those Bruder conversions are looking great.

[ddmckee54]

Rester:

Thanks, but the conversion hasn't really started yet.  Right now I'm just designing the parts that I will be using during the conversions.

For the last couple of days I've been playing with assemblies in Alibre.  So far I'm batting 1000, I've managed to break every one of them that I've tried - but I'm learning from my mistakes.  That doesn't mean I'm making less mistakes, it just means that when they happen now they are WAY more impressive.  This is my latest test assembly, I'm still trying to figure out how to save the current view.


I hope I didn't screw up the previous posts, when I previewed my post I noticed that I hadn't scaled the image for posting.  Somehow instead of deleting just the unscaled image, I managed to delete the entire Frankendiff album.  I put it back, reloaded the photos, and shared it again - hopefully all is well.  Where's the EASY button when you really need it?

Now all I've got to do is figure out how to get my spring hangers, springs, and equalizer beam center pivot to fit into a 32x65x10mm volume.

Don

[ddmckee54]

OK, as promised we'll open up the picture page.  (Who besides me still remembers the jingle for Picture Pages?)

What you're looking at is the view from the passenger side, standing in front of the center axle looking to the rear. 

I've temporarily hidden the passenger side frame rail, and just about every part of the suspension is in place now.  I don't know how many leaves I will need for support, that's why there's a gap between the springs and the equalizer beam pivot bracket.  I've got the springs drawn as three 0.5mm thick leaves, that may, or may not be overkill.  I'll adjust the amount of leaves to suit the load, for now I'll probably just make a spacer block.

I'm still waiting for the donor axle order, according to the tracking it should be here within the next week.  I sounds like the O-rings, the brass tubing, my 8" caliper, and the other odds and ends that I ordered should all get here about the same time.

Don

[ddmckee54]

While I'm waiting for things to arrive, I need to figure out how to make some miniature squared-off U-bolts.  The bolts will be M2, the legs of the U will be 7.5mm on centers, and the legs will be about 13-14mm long.  Oh, and I'll need 4 of them - for EACH axle.  I'm thinking I need some sort of die that I easily, and consistently, press the U-bolts.  I started working on this a few days ago.  So far I've tried and failed - twice.

This is the parts of the first die. 

The movable top die is on the left and the base die is on the right.  That V-for-victory shaped thing in the middle is the result of the first pressing - IT won.  I'm using a Harbor Freight 1/2 ton arbor press to do all the pressing.

This just shows how things went together for the first press.


I modified the base die and the top die for the second attempt.  The first dies' only had 3 bottom layers, 3 top layers, 3 perimeter walls, and 30% infill - I doubled all of those for the second attempt.  The areas that had the most damage on the first dies were where the 2mm rod contacted them as the rod was being forced into a staple shape.  The bottom of the top die took a real beating, but the radii at the top of the U-bolt slot in the base die also took a hit.  I can't get a decent close-up picture of those areas so you're just gonna have to trust me on that one.  Other than upping the wall count and infill, I couldn't think of an easy way to beef up the top die.  The bottom die on the other hand was easy.  I used steel, in the form of a pair of 1/4"-20 bolts.  I punched a pair of holes through the base die, so that the outside of the bolt's shank replaced the radius in the slot for the U-bolt.

This is the parts of the second die, and the results of the second press.


I have the beginning of a squared off U-bolt going on there.  The top die still took a beating, but not nearly as bad as the first time.  If I make the top die out of steel I should be just about there.  It's a simple piece of 5mm flat stock with a 2mm slot cut part of the way across it - eazee-peasee.

The is the second die set up to press.


Don

[ddmckee54]

Well, my shipment of donor axles failed to arrive.  Apparently the US Postal Service lost my order, they were the last to touch it on October 29th - after that the order apparently disappeared into La-La land.  I got a refund on that order and placed another order, this time from a US shipper.  That order is supposed to get here Friday.

I did re-make the top die for the U-bolt bending contraption, milled it out of a chunk of 1/4"x3/4" hot-rolled flat stock that I had laying around.  There was some improvement, but not as much as I would have liked.  However, squeezing the legs of the U-bolt while it's still in the top die closes things up nicely.  I haven't threaded the legs of the U-bolt yet, I've just been trying to get as close to a 90 degree bend as I can.  Now I'm thinking that the way I'm forming the legs of the U-bolt will just smear those little M2 threads out of existence.  I think if I slip some brass tubing over the threaded sections before I bend the legs, that should keep the M2 threads for being destroyed.  I'll need to modify the lower die to accommodate the tubing though.

My order of 6mm OD O-rings arrived yesterday.  Those are for the equalizer beam pivot brackets, to allow things to flex a little.  I don't think I've ever received a package that was as well protected as that one was.  The O-rings, all 100 of the little suckers, were in a small zip-lock bag.  This bag, and a thank you for your order note, were then put in a slightly larger zip-lock bag and wrapped in a double layer of bubble-wrap.  All of the above was stuffed into a bubble-wrap lined shipping envelope, which the US Postal Service actually delivered to me this time.

Since I had to modify both the front and rear differential housings, to give me a fixed location for the equalizer beam and torque rod pivot brackets, I need to re-print the diff housings.  Soooo... I might as well change the filament in the plastic-pooping-robot over to black.  That way I "shouldn't" have to paint the suspension parts black.  I might as well print out enough parts for both axles while I'm at it.

Don

[ddmckee54]

It's been a bit since I last updated this....

I "WAS" going to print out a new lower die for the U-bolt bender, so I could try my idea of using the brass tubing to protect the threads when bending the legs.  My printer had other ideas though, I got a plugged nozzle on the 2nd or 3rd layer of the part. 

I changed the nozzle and started another print, though about half way through it jammed again.  This time it took out the PTFE liner.  This is the second time in about a month that I've had to change that liner, and I didn't have any more spares.  I ordered some more liners, and some new nozzles, and they have arrived.  I had something similar happen a few years ago, only that was a brand new spool.  When I changed the filament all the problems went away.

I've used old filament before, usually with no problems.  I normally store any left-over filament in a zip-lock bag, and I'll throw a couple of desiccant pouches in with the filament.  I usually don't have any problems doing this.  However I have noticed that if the filament is a year or two old or more - it does tend to break in the feed tube to the extruder.  Especially towards the end of the roll.  It won't break while printing, but if the printer sits for a couple of days there's apparently enough stresses built up in the filament to cause it to break.

Bottom line - the plugged nozzle, the bad PTFE liner, AND the rest of that roll of filament are going to be introduced to the trash can when I put in the new parts.

Don

[ddmckee54]

Been a while since I updated this thread, but I've been keeping busy.

The printer has been repaired and put back into operation printing out rear axle and suspension parts.  I've ordered and received a bunch of parts and materials that will be needed for the axle modifications.  Two days before Christmas my long lost axles finally showed up, turns out Customs had opened them for inspection and apparently misplaced them.  I contacted the seller, who had already refunded my money, offering to pay for the axles that I had finally received.  On Christmas Eve he told me to forget about it and have a nice Christmas. 

I found out that I am much too digitally inclined to be able to keep track of where the tool bit is on the Sherline, as opposed to where I THINK it is.  So I installed a pair of remote digital readouts on the Sherline.  Hopefully that problem is solved.

Rather than my original fairly complicated plan for shortening the axle shafts, I came up with a simpler one that should give a wannabee machinist like me a better chance of success.  I got some 5mm OD brass tubing with a 1mm wall thickness, which arrived on Saturday.  I'm going to cut a chunk out of the existing axle shafts, turn a 3mm OD stub on the pieces I'm going to reuse, use the brass tubing as a sleeve, and Loctite the parts together.  Now to get back to the axle modifications.
 
Yesterday I cleaned all of the god-awful smelling factory grease off the donor axle parts. I need to make several modifications to the axle shafts and I don't want to be smelling that crap all the time.

I know I need to find some clearance for the spider gears, but how much do I need? I knew that if I backed off the screws holding the ring gear to the spider housing the diff worked as advertised, but how to measure it? My idea was to use the M2 screws that held the spider housing to the ring gear as my indicator. If I count the number of flats as I loosen each screw until I find the sweet spot, that will tell me how far I moved the screw. Turns out that sweet spot is 1-1/2 turns out from tight. An M2 thread has a 0.4mm pitch, so 1-1/2 turns means the head of the bolt moved 0.6mm. I need to take 0.3mm off the back side of the bevel gear on each axle shaft to make things fit right. I think that's right, gonna need to try it and find out.

I also need to shorten each axle by 29-30mm. I'm not sure if that number will be affected by my fix to the spider gear clearance problem. I don't think it will but I need to try it and find out before I start whacking chunks out of the axles.

[ddmckee54]

I cut the existing axles with a hacksaw and took 0.3mm off the backside of the diff gears on the axles.  I haven't spliced the axles back together yet, but I reassembled the differential to see if I have gained enough clearance.  The differential now works correctly when the differential cover screws are completely tight, but it works better in one direction than the other.  It turns in both directions, but in one direction it is definitely harder to turn.  I also noticed that there is no noticeable end-play in the axle shafts.  There is no grease in the gears right now and it is entirely possible that with proper lubrication and a little run-in time this clear up 

I'm using the Kong axle that I purchased as my benchmark so I checked to see if it had any end-play in the axles - it does.  So maybe I still need to take an extra 0.1mm off the back of the gears on the axles.

[ddmckee54]

WELLLLL... things did NOT go exactly to plan, the best laid plans of mice and men  - and all that crap.  My very first plan was to remove the gear from the end of the axle shaft, shorten that end, cut new flats on the axle to match the gear, and cut new threads to match the screw that holds, the gear on.  The only problem with that plan was that I could not get the screw to break free, I even tried heating the screw to try get whatever thread locker they had used to break free.  The only thing I managed to do was to round out the hex socket in the screw.  The next plan WAS that I would cut the steel axles in two, turn a stub about 10mm long on the cut ends to a 3mm OD, cut a piece of 5mm OD x 3mm ID brass tube to use as a splice, then Loctite everything back together.  Easee-Peezee, right?

Things did not go well from the beginning, then went downhill rapidly after that. 
Problem 1 - How do I hold these little turds to cut them?  My first thought was to use my metric ER16 collets.  Something like this IS after-all why I bought them, and the collet chucks for the Unimat and the Sherline.  So I blissfully cut the axles apart with a hacksaw, figuring that I could easily clean up the ragged ends with the lathe.  Heck I could even chamfer the ends, 'cause chamfers are what separate us from the savages - right?
Problem 2 - I knew that the collet chuck for my Unimat registered on the shoulder on the spindle nose, I ASSUMED that the collet chuck for the Sherline did something similar.  Imagine my surprise when I opened the box to find that the collet chuck for the Sherline registered in the spindle taper, AND uses a 1/4" bolt as a drawbar to hold it in the spindle.  OK, that means that if I need to work on a longer part I'll need to work on the end hanging out in the breeze, and not work next to the chuck where there's less flex.  That procedure actually worked fine on the ends that were threaded for the wheel attachment.
Problem 3 - The other two pieces of the original axles still have the gears FIRMLY attached to them, and I need to work on the OTHER end.  NO Problemo, I'll just slide the gear into the spindle bore, the bore on the Sherline is HUGE compared to the Unimat.  AAWWW CRAP, there's already a drawbar there.  The gear fits inside the collet chuck, maybe there will be enough room to put the part in from the back - THEN tighten the collet down?  Nope, there may be a mm or two of clearance there, but there's just not ENOUGH extra mm's.  OK, lets swap out to the 3 jaw.  Then the gear can just slide into the spindle bore.
Problem 4 - I got out the 3 jaw, cleaned everything up, and installed it.  It has been sitting in a box for years - remember?  I opened up the jaws, slid that part in, and...  IT DON'T FIT!!!!  WHADDAYAMEAN, it don't fit?  That bore is huge, it's 10mm, and the gear is only... 10.6mm.   OH Crap! 
Problem 5 - I can't work on the area of the shaft I want to - at least not where I want to work on it.  But, I've got a lot of the brass tubing, I can make the splice as long as I want.  I can pull the part out until it bottoms out on the back of the 3 jaw, I want to eliminate that cross drilled hole if possible.  Pulling the part to the  back of the 3 jaw puts the existing cross drilled hole inside the sleeve, but not by much.  But, it IS inside the sleeve, so MAYBE it'll be OK?
Problem 6 - I needed to turn a 3mm OD stub on the cut end of the axle - Easee-Peezee.  I figured I'd take off 1.1mm then sneak up on it - no problem.  So, I made several passes taking a few tenths of a mm at a time and didn't stop to measure until I hit 1.1mm of movement.  WTF, whaddayamean 2.82mm OD??  I only took off 1.1mm.  But I took it off of each side now didn't I.  I was much more careful on the second axle.  That gap is way more gap than any of the Loctite that I have is good for, but I can always use JB Weld.  So that's what I did, This is what the axles looked like at this point.

Problem 7 - I needed to shorten the brass sleeve to length.  Since the gear's OD is larger than the spindle bore I had a LOT of stick-out, about 25-30mm's worth.  It did not end well.
It snapped off right at the cross-drilled hole location.  I think the axle would have been strong enough for the loads it will see, if only I would have just put the splice in a spot that's not close to an existing cross-drilled hole.  I also found out that I need to make any axle shaft modifications starting on the outboard end, rather than the inboard end like I did this time.

The good news is that because I ordered complete extra axles, instead of just the extra pinion that I needed to make a center drive axle, I've already got spare axle shafts to work with.  The extra bearings are the same size as what I would need for the front wheels if I decide to make a powered front axle.

Don

[ddmckee54]

If I decide to also build a powered steer axle, I'll need to be able to take the gear off the end of the axle shaft.
 The screw holding the gear is apparently locked on there with some type of schmoo, because all I've been able to do so far is strip out the hex socket on the screw in the shaft that snapped.  Last night before I went to bed I decided that I was going to throw my remaining shortened axle into the oven for a while.  After 10 minutes at 300 degrees F, I gave it a try annddd...

We have a winner!  This should make Future Me's life a little easier.

[ddmckee54]

Seems like I've just been talking to myself for a while, but there has been a little progress made. 


I cut down the partial axle that was shown previously, and took a little more care with the diameter this time.  I glued the turned stub into the brass tube using a Vee-block to align the parts as the Loctite cured.  The original axle shafts were about 101.8mm, I rounded this up to 102mm.  I had calculated that I needed to take 28mm out of each axle shaft.  But I wanted this "practice" axle to be too long, so I added another 4mm onto my target length.  I then cut the 5mm diameter end of the outboard axle stub to length and turned a 3mm OD stub 10mm long on that end.  I then slipped the axle shaft together and checked the length with my trusty HF 4" caliper.  After deciding it was good enough for "gubmint" work I glued the parts together, again using the Vee-block for alignment

After things had cured for a few hours I couldn't wait anymore and decided to test fit the axle in my 3D printed Frankendiff housing.  I had added another 4mm onto my calculated axle length, and there's a 4mm gap between the 12mm hex driver and the outer bearing.  So I've got a working procedure for narrowing my WLToys rear axles for use on my Bruder truck RC conversions.

Now I only have to do this at least 4 more times and I'll be able to move on to actually building the truck.  I said at least 4, but it will probably be 6 times since I'm 99.44% sure that I'm gonna swipe a very good idea from Blender on another forum and also build a powered steer axle.

Don

[BillTodd]

I'm still quietly following along ;-)

[ddmckee54]

Thanks Bill, now at least I KNOW that I'm not just talking to myself.

[BillTodd]

Unless... I'm just a figment of your imagination! 


(In which case  would you be so kind, as to imagine me in a slightly less damp , cold country, with two working knees)

[ozzie46]

another following

ron

[tom osselton]

  I’m watching too.

[ddmckee54]

A little more progress has been made.  I was able to find the broken stub that was shown in Post #18.  I thought that I had pitched it, turns out I'd just misplaced it.  I found it when I went to use the toaster oven to remove the gears from the next donor axle.  I have enough bits and pieces that I now have the fixin's for 2 complete differentials, if I can get that M2 screw with the rounded out hex removed.  While the toaster oven was hot I also took apart the axle shown in Post #20 that was 4mm too long.  At some point over the last several years I had purchased the smallest Easy-Out I've ever seen.  I was able to get enough purchase with it that I could back the screw out enough to grab on to it with a pair of pliers and remove it.

Today I modified the stub axles that I already had cut apart.  The axle shaft from Post #20 was 74.27mm over-all in length, so I'm aiming for a 70.25mm length in my completed axles.  I modified the first axle, Loctited it together, and left it clamped in the Vee-block while I modified the other axle. 

One measures 70.14mm, and the other is 70.38mm.  Not bad for a beginner, but I plan on doing better next time.  And, the only thing that I had to scrap was that bent length of brass tubing shown in Post #18.

[ddmckee54]

The axle looks good, but when I transferred the duals from the Kong axle onto my axle... the wheels sorta fell off the bus.  When I tightened them down they wouldn't turn.    I took things back apart and started measuring bits and pieces.

The 12mm hex driver from the Kong axles is 6.5mm thick and uses a drive pin with a 1.5mm OD.  The WLToys hex driver is 5.5mm thick and uses a drive pin with a 1mm OD.  I backed things off enough that the wheels turned freely and did a sanity check against the Bruder tires.

From this angle things look OK, however...

From this angle you can see they're too narrow by a couple of mm.

If I make the driver pockets 5.5mm deep instead of their current 6.5mm depth then things should be just about right.  I think I'll make the pockets 5mm deep though, because a little clearance nerver hurts Clarance.

[ddmckee54]

Progress in the last couple of days has been a lot like doing the Hokey-Pokey, one step forward, two steps back, and three steps forward.

I modified the existing 3D model for the dual wheels to correct the hex pocket that was too deep.  To do that I  had to roll back through the history tree and modify the step that formed the pocket, changing the pocket depth from 6.5mm to 5 mm.  At this point it was almost bed-time, so I did what any sane person does and spent the next couple of hours watching YouTube videos - THEN I went to bed.  The next day I saved and sliced the STL file and started the wheels printing. 

About 3 hours into a 4 hour print I noticed a alarming lack of features in the print and promptly aborted it.  There  SHOULD hove been 8 holes for the M2 screws that hold the hub cover on, and there were also supposed to be 8 slots in the rim that were suspiciously absent.  When I saved the STL file I hadn't rolled the history tree back to the end, so the STL just included the 3D model up to that point in  the history.  It skipped a couple of important steps. like the screw holes, the slots, and most importantly - scaling the model for printing.

Once I corrected the operator blunders, I really gotta hire better help around here, I reprinted the wheels.  This time things worked out like the should have the first time.
 

Other than black wheels instead of red, it doesn't look that much different than it did in the last post.

[vtsteam]

It was the YouTube videos. 

[ddmckee54]

Yeah, about Plan B....

It turns out that when I reduced the depth of the hex pocket in the rear wheels I reduced the wheel track at the same time.  This would have caused problems down the road because it also reduced my already minimal tire clearance to the frame rails.  The "Bag of Misfit Parts" continues to grow.

For the last couple of days - ish, I have been working on adapting an idea for a powered steer axle that I stole from Blender on another forum.  I've now got it to the point where I'm putting a front diff  assembly together in Alibre to check the fits.  It looks like about the only modifications I'll have to make to the diff housing models is to turn off the step that forms the pads on the outboard ends of the housing halves.  I think I found some Nylon flanged bushings and shoulder bolts on Ebay that I can use for the pivots on the knuckles.  I'll have to verify sizes, get some ordered, and modify the 3D models to suit.  I've got a lot of clean-up work to do on the models before they'll be printable.  When I can remember, or figure out again, what I did/need to do to show the suspension assembly I'll post what that assembly looks like.  I got a 3D model of what would probably be the shortest 1/16 scale 6x6 truck frame and a Hendrickson style walking beam rear suspension.  So far it LOOKS like everything will clear without major issues.  I've just been working on the driver's side of the front axle, but once I'm happy with that, mirroring the parts to the other side is simple.

Speaking  of printing, Ebay made me a offer on a certified re-furbished Creality Mage S printer that I couldn't refuse.  So I am now jumping down to resin printing rabbit hole - wish me luck.

[kayzed1]

  me too!

[ddmckee54]

I mentioned in an earlier post that the ER16 chuck I got for the Sherline mounts in the spindle's Morse taper and uses a 1/4-20 bolt for the drawbar.  I know that this will give me better concentricity, but the work I'll be doing in the foreseeable future doesn't require that level of accuracy.  Besides, I really like to be able shove a long-ish part through into the spindle bore; like a 102mm long donor axle that needs to be shortened.  So today I went searching for another ER16 collet chuck for the Sherline's 3/4-16 spindle threads - I didn't find any.

I DID find one for a Taig lathe though, and I also found out that since they both use the same 3/4-16 threads on their spindles it will work just fine on the Sherline.  Since the price seemed reasonable I arranged to get one headed my way.  I also ordered some other little doo-dads that I'll be needing in the near future.

Getting the suspension assembly into a format useable on here was easier than I remembered.  Alibre allowed me to export the assembly as a JPG file.  I then used Gimp to scale the image to a 640x480 format that most forums will accept.  Then it was saved to Google Photos since a lot of forums require you to use 3rd party storage if images/videos.  Annndd... you get something like this.
 

I know it's missing a lot of stuff, a couple of wheels, ALL the tires, drive shafts, fasteners, tie rod, not to mention the great gaping hole on the passenger's side where the pivots, steering knuckle, and CV joint should be.  Cut me some slack, this is a Proof-of-Concept model, not a for-realsies highly detailed 3D model.

[ddmckee54]

I just finished modifying the second set of donor axles.  They look remarkably like the first set, just a little more consistent.  One measures 69.95mm and the other is 69.97mm, I was aiming for 70.00mm - so I'm about 2 thou under with both of them.

I've still got some issues with the Sherline, the headstock bearings are stiff and kind of rough.  They have been since I first started working on it.  I suspect that the original grease in the shielded bearings has dried out.  I've been dousing them with light oil in hopes of reconstituting the original grease but so far no luck.  I'm thinking it's probably going to need new bearings.

The other issue is with the carriage lead screw, it binds up.  However I only notice this when moving the carriage towards the headstock, and it only binds up when the handle is between about the 2:00 and 5:00 positions; the rest of the time it's OK.  I'm thinking that when the Sherline did the nose-dive off the bench onto the drive dog for the threading attachment it left a boo-boo that I didn't find during the initial repair, which happened about a month before I started this thread.  The ham-handed retired engineer that managed to knock it off the bench should have had his wages docked for the repairs, but since he doesn't get any wages docking them is kind of an empty threat.

[vtsteam]

Sorry to hear about the lathe accident!  Sounds like a bent lead screw. Maybe up near the handle. Any chance of taking it off and straightening? 

[ddmckee54]

Hmmmm...guess I didn't show what the modified axles look like.


Regarding the Sherline carriage lead-screw issue, when I started taking it apart last night I discovered that the issue went away when I took the hand-wheel off.  Upon closer examination of the hand-wheel and the lead-screw shaft I found a nick on the face of the hand-wheel and a burr on the lead-screw.  The burr on the lead-screw was caused by the grub screw, but I've got no idea what could have caused the nick on the hand-wheel.  I stoned off the raised areas and when I reassembled things that particular problem was gone.

I've been plottin' & conivin' for a while as to how I can adapt the Frankendiff into a powered steer axle.  Blender's build of a 1/14 scale TH407C telehandler on another forum gave me the idea I needed. He used Losi CVD front axles to build his steer axles.  Since I've already got a butt-load of the WLToys 12428 replacement rear axles I decided to get a set of replacement front axles to see if they'd be usable.  After doing a little (very rough) 3D modeling, it looks like things will work out.  They both use a ball and socket joint in the knuckle, but the Losi uses a CVD joint while WLToys uses a CVA joint.  A CVD joint has the ball on the axle with the socket on the half-shaft.  A CVA joint flips that around and has the ball on the half-shaft with the socket on the axle.  Here's a picture of the WLToys CVA joints.


At the top is the assembled CVA joint, in the middle is the axle with the socket, and on the bottom is the half-shaft.  At the left is the dog-bone that would normally attach to the front diff.  This 14mm section on the left is totally useless to me, I only need about the last 25mm on the right.  The center section of the half-shaft currently has a 3.18mm OD.  My current plan is to turn part of the center section and part of the tapered area just to the right of it down to a 3mm OD.  This will then be Loctited into the outboard end of the modified donor axle, just like I did when shortening the donor axles for the rear diffs.

[ddmckee54]

The Sherline bearings are supposed to be lubricated for life, but they are shielded bearings - not sealed.  If they sit for several years without being used, the grease will dry out and harden.  According to the part number they are standard precision bearings, not high precision.  Once upon a time in the west I used to repair machine tools for a living, so swapping spindle bearings is not outside my comfort zone.  At least now the parts are a LOT lighter, and they're not covered in congealed nasty smelling coolant.

Yesterday I modified  the first CVA half-shaft.

The modified half-shaft is just slipped into the brass tube for now, I'm just getting started on the working 3D model that will be used to print the parts.  I've got bushings and shoulder bolts on order for the knuckle pivots, so I can accurately model things now.  I model things in mm because that's how most 3D printers think.  I really wonder sometimes when reverse engineering this stuff, because some of the measurements make no sense.  Like why is part of the half-shaft turned to 3.18mm, and why is the socket bored to 7.62mm.  Earlier today it finally dawned on me, 3.18mm is 0.125", and that odd 7.62mm bore is 0.3".  When I convert all the oddball Metric measurements to Imperial units they come out nice and neat.

[vtsteam]

I hear you, dd, on the tediousness of units conversions, but that .3" seems unusual even for imperial, where you'd expect .3125". Wonder where that came from? 

[ddmckee54]

I hear you, dd, on the tediousness of units conversions, but that .3" seems unusual even for imperial, where you'd expect .3125". Wonder where that came from? 

Who knows, maybe it's just a coincidence.

I'm brain-fried right now, for the last 5-6 hours I've been fighting with Alibre locking up.  I'm trying to do the final 3D design for the powered steer diff parts.  The design I showed a couple of posts ago was thrown together to see if I could even make it work.  NOW I need to cross the I's and dot the T's so that it will all work together, and that means modeling all the individual parts.  That's actually a good thing as I found a couple of gotchya's while doing it. 

One of those gotchya's was determining how much I needed to shrink/stretch the ends of the diff front and rear housings to accommodate the single front wheel instead of the dual rear wheels, and still maintain the same wheel track.  It turns out I needed to take 13.5mm off each side.  I know that doesn't make sense that I need to move the end of the diff housing inboard when going from duals to singles, but I spent a couple hours convincing myself that moving things 13.5mm inboard was actually right.

The second gotchya was when I realized that the screws holding what I'm calling the diff pivot in place would be hitting the outboard bearing - that would not be good.  So I had to change the design of the diff pivot, it's now about 6mm longer.  THIS change interfered with the outboard screws holding the front and rear diff halves together.  Since the diff pivot slides over the ends of the front and rear diff halves holding them together, those screws aren't really needed any more.  Problem solved, but I did have to change the 3D models for both halves to reflect this.

The third gotchya is what does the length of the brass tubing splice need to be?  My modified rear axle measures 147mm from end to end.  My modified axles were 70mm nominal length, so that means the spider gears were occupying 7mm of space in the middle.  My 3D printed non-powered front axle is 172mm from end to end.  If I subtract the 7mm for the spider gears, and divide be 2, the stack-up for my front axle length should be 82.5mm?  (Why do I feel like Rodney Dangerfield in "Back to School" right now?)

While typing this I just realized that there's nothing keeping the outboard bearing of the front axle from sliding outwards.  On the rear axles the hex driver holds the bearing in place, on the front axle there's nothing but air in that location.  Oh well, that's a problem for future me, right now it's time to call it a day.

Don

[RussellT]

It's always puzzled me  (well since I found out about it) why Nato standard ammunition is referred to as 7.62mm when it is 0.3 inches.

Russell

[vtsteam]

I suppose if you want to finish off 5/16" hot rolled stock, .300" might be a convenient figure to shoot for.

[ddmckee54]

I'm still fighting with Alibre Design Pro, I just purchased a perpetual off-line license about 6-8 months ago.  I was using Designspark 3D Mechanical until they went subscription.  I know they still have a "Free" version, but that version is a dumbed down copy of what was current before they went subscription.  I haven't used Alibre enough to become proficient with it yet, especially when using an "assembly".  I can put the parts where I want them, but when I try to animate the parts things start to go hay-wire.  Also, with the suspension assembly shown below I'm trying to build it out of various sub-assemblies.

The suspension assembly contains sub-assemblies for the rear axle, the center axle, and the front axle.  When working directly with the front axle assembly I can make the CVA axle pivot like it's supposed to.  When I add the front axle sub-assembly to the suspension assembly I can no longer make the CVA axles pivot, there's probably check-box somewhere that I need to check/un-check - but I haven't found it yet.  When I get the spindles/axle bearing housings/steering arms, and the tie-rod, designed it will be interesting to see if it will act the way it's supposed to. 

[ddmckee54]

I think that I just might be starting to get a handle on this Alibre assembly crap. 


You are looking at a functional 3D assembly model.  I can spin the wheel on the axle.  When I turn the steering knuckle the wheel moves with it, and the tie-rod brings the knuckle on the other side along for the ride.

I did have to give up on the idea of putting the tie-rod above the drive shaft though, there just wasn't enough room.  Where it is currently located the tie-rod is about 4-5mm below the driveshaft and won't touch any thing trough its' full range of travel.  The bottom of the tie-rod is still above the bottom of the differential though so the tie-rod shouldn't get caught on any thing.

[ddmckee54]

I've been working on the Sherline again for the last week.  I'm replacing the cheap Chinese scales that I put on it a couple of months ago, they were just an experiment anyway.  I didn't know if I like the scales, and I didn't know if a Noob like me could get them installed without destroying something.  I got them installed, and that was a game changer for me.  I REALLY like the idea of scales on the lathe, just not those scales - for several reasons. 1) They're battery powered, and there's no provision for an AC adapter.  My scales have no Auto-Off feature, I don't know how many times I've come down to the shop only to discover I'd left the scales on the night before.  2) My carriage scale periodically resets to 0.  I've found that this glitching is not an uncommon problem with these scales.  One one the ways they can make them so cheap is by eliminating all the shielding.  3) I really don't like the way I installed them.  I used the brackets provided with the scales which meant the scales wound with the scale facing up, as a shelf for chips and dirt.

I'm replacing the cheap scales with Igaging EZ-View Plus scales, they've got better resolution, they're shielded, and they have an available AC adapter.  I was having trouble wrapping my head around what the brackets for the new scales should look like, and if the way I wanted to install them would even work.  I spent the last week building a 3D model of my lathe, the base it sits on, the carriage with its' dovetails, the cross-slide with its' dovetails, the new scales, and the new read heads.  I then put all those parts together as an assembly drawing and got the carriage and cross-slide working together and set the limits for their normal range of motion.  I initially had the scales and read heads just hanging out in mid-air.  Once I got things dancing around together I started designing the brackets that would hold things together holding the various bits and pieces in place.  The 3D model looks like this, all the pinkish bits are 3D printed parts.


Last night I started the 3D printer pooping out the parts before I went to bed.  This morning these were waiting on the printer for me.

Unfortunately the part in the upper RH corner, and part in the lower LH corner do not fit.  Operator error, what can I say.  I fixed the model and re-printed those parts.  The installation is ongoing and should be complete tomorrow?

[vtsteam]

Don with those scales you might like to check this site out:

https://www.yuriystoys.com/

I use the bluetooth DRO on my mill, as detailed here.

https://www.madmodder.net/index.php/topic,13501

VERY happy with it. Also I could use the same box with my lathe if I did add scales, and just unplug it from the mill and plug it in there. 

[ddmckee54]

I've been keeping an eye on Yuri's work for a number of years now.  The last time I checked, he'd found out that the Igaging EZ-View Plus scales use a different protocol than their Digi-Mag scales did.  He was working on an interface but it wasn't ready yet.

[ddmckee54]

Further development on the is on hold for a week or so.  The motor/2-speed gearbox, that I initially wanted to power the model with, uses a single 370 sized motor and has 3mm output shafts.  While the 370 sized motor MIGHT have been up to the task, I don't think the 3mm output shafts would have been - since all of the differentials have 5mm input shafts.

I've got an LDRC LD1201 Unimog replacement motor/gearbox ordered.  It uses a pair of 370 size motors driving a 2-speed gearbox with 5mm output shafts.  One of the outputs looks to be centered, and the other appears to be offset to the side.  If it is offset then I'll have to slide the pumpkin to one side on the front and rear housings for my steer axle.  Unless I can find some drawings on-line, I won't be able to do any more work on the steer axle until I can get some measurements from the gearbox.

[ddmckee54]

The motors/gearbox/transfer case arrived today, now I'll start 3D modeling it.  That way I can use that model to design the offset I'll need for the pumpkin in my steer axle.  I'll also have that model for use in designing the parts for the future conversions.  The output shafts are 4mm, not the 5mm I had hoped for, but they can easily be bushed up to the 5mm needed by the differentials. 

I was worried that there wouldn't be enough room for the Universal joint to the front axle.  The dimensions for the drive shafts I'm looking at say they're 12mm in diameter.  The only way I could get a measurement to the obstruction was by measuring across the shaft to the obstruction, and that distance was 8,55mm.  Since it's a 4mm shaft, that means the obstruction is 6.55mm away from the center.  The drive shaft needs 6mm, so I SHOULD have at least a half mm of clearance.  And clearance is clearance Clarence.

It also looks like I'll need to make custom drive pins/set screws for the drive shafts, but that'll be nothing more than turning down some 4mm set screws to fit.  I'd better get some 4mm set screws on order so I've got something to work with.  It's real IFFY that the local hardware store would have any.  I have trouble finding anything smaller than 6-32 in Imperial and 5mm in Metric.

Don

[ddmckee54]

Between a late night last night and some more time this morning I got the motors/gearbox/transfer case modeled.  I measured the wheelbase between the front axle and the center axle in the MAN mixer and extended my frame rails accordingly.  I dropped the motor unit into the assembly model and got it positioned about where it will live.  The assembly model now looks like this.


This thing is starting to look more like a truck, and less like a clown car.  The frame rails are 335mm long now which is probably about right for a 1/16 scale cab-over.

I COULD move the front diff's pumpkin 18.5mm to the passenger's side, which would get the  transfer case output shaft and the differential's input shaft lined up side to side.  But, if I do that then the pumpkin is going to be crowding into the area that the knuckle pivot needs to live.  So I'm only going to slide it over 10mm.  The drive shaft angles will be a little harsher, but it's not like I trying to design these for thousands of miles of useful life.

[ddmckee54]

OK, a couple of minor speed-bumps, but nothing that Ebay and a credit card can't handle.

Speed-bump #1 - Most of the drive shafts I've found have 5mm bores or 6.2mm bores. The WLToys axles have 5mm input shafts and the shafts with a 5mm bore are a better fit to the LD1201 transfer case. But the LD1201 has 4mm output shafts. No problem, I'll just cut a piece of 4x5mm tubing and glue that into one end of the drive shaft. "Cept that I ain't got no 4x5 tubing, I've got 3x4 and 3x5 - but no 4x5.

Speed-bump #2 - Drive shaft lengths. I can't really find the drive shaft lengths I need. My last revision of the 3D model for the suspension/chassis put all the axle spacing's in their correct positions for the upcoming cement mixer conversion. I also centered the gearbox so that the front and rear drive shafts can be interchangeable. This leaves me with a nominal drive shaft length of 46-ish mm. Since the transfer case output shafts are 2 different lengths, 6mm and 7mm, I'm using the 7mm length to determine the minimum and maximum drive shaft lengths. I need to collapse my 46mm nominal drive shaft about 7mm in order to be able to remove the drive shaft - without needing to remove other bits of the truck anyway. I also need to allow for suspension droop, which won't be much since this is a cement mixer - not a rock crawler. But I need to allow for some, so I'll use 7mm there too. Bottom line - I need the front and rear drive shafts to be from 39-53-ish mm in length. It can be more than 53mm, but no less. The drive shaft from the center axle to the rear axle is worse, it needs to be from 33-44mm in length. These are the drive shafts that I like the best.  https://www.ebay.com/itm/375169557748

But....The shortest length is 60-77mm, I've got 3 of them on order. On the plus side, they use an internal/external spline for the extension instead if a square drive or a pin in slot setup. The external splines are full length, they are easier to cut so that makes sense. The internal splines are not easy to do at this size. That difficulty goes up as the spline length increases, there's not that much room in the hole to begin with and the chips HAVE to go somewhere. My guess is that the splines are only a few mm in length, the rest of the hole will be counter-bored to the major diameter of the splines - if not larger. My current plan is to cut a big enough chunk out of the middle of the female half that the length of the stack-up equals my minimum drive shaft length. I've got some 3/8" OD aluminum tubing that I'll use as a reinforcing sleeve and glue the cut parts into it. Then I cut the male splines off just enough to allow the drive shaft to fully collapse. And Bob's you uncle - I hope. It worked for the axle shafts, should work here too. We'll find out. I also ordered 2 of these. https://www.ebay.com/itm/314228515981 To see if I can cut them shorter than the others for the center to rear axle shaft.

If I get REALLY lucky, and the internal splines go full depth, then all I have to do is cut things to length. (And if you believe that's gonna happen... Well, I got some bottom land in Florida I'll sell you - it's REAL close to the river.)

Don

[vtsteam]

Still following...

[ddmckee54]

Thanks, I was beginning to think I was just talking to myself again.  But since I'm the only one in the house, I guess at least I'm always talking to the smartest person in the room?

[vtsteam]

I don't really know much about big trucks, or model trucks for that matter, so I look at your renderings with admiration, but not a lot of comprehension about what's needed or important in the mechanics. I'm glad you do explain, and post these things and your progress, and I'm sure I'll learn more in reading about it. 

[ddmckee54]

OK, I've found out that I'm going to have to revisit my chassis design a little.  So far I've been sticking to the measurements taken off the Bruder MAN mixer, but that's gonna have to change a little.  I'm going to have to modify the axle spacing/locations a little.  I cannot find an off the shelf axle that will fit the existing center axle to rear axle spacing.  I currently have an absolute minimum drive shaft length of 42mm.  When you add in the 7mm I need to be able collapse the drive shaft to take it out. then I need a drive shaft that has a minimum length of 35mm.  I was able to find drive shafts in the 30-36mm range, but they only had a 2mm ID with a 6mm OD.  Nope, that ain't happenin'.  I did find a Lesu drive shaft with a 5mm bore in the 45-50mm range, and have one headed my way.  It costs 3 times as much as any of the other drive shafts, but none of them can be made to fit.

My current plan is to add 5mm to the  spacing between the center and rear axle, and play with their locations a little so I don't mess up the drive shafts coming off the transfer case.  By adding the 5mm to the axle to axle spacing, I SHOULD get into the middle of the range of motion for the Lesu drive shaft.  Unfortunately it also means that the drive shaft and the axle have to be installed/removed as a unit.

[ddmckee54]

More parts arrived today, the 60-70mm drive shafts showed up.  I DO believe that they will work for the drive shafts from the transfer case to the front and center axles.  According to the tracking info, the Lesu axles should be here on Saturday - we'll see if they'll work out then.  I still have to modify the drive pins for the drive shafts.  I need to turn the pins down from 3mm to 2mm.  I'll need to make bushings to support the unthreaded end of the drive pins in the drive shaft knuckles since those holes are currently 3mm.I'll also need to make bushings for the transfer case end of both the drive shafts, which needs 4mm bores but currently have 5mm bores.  I'll probably have to modify the drive pins, and make bushings for the the Lesu drive shafts too. 

Pretty soon I'm going to have to quit thinking of this as a generic design project. and make it an actual Work In Progress.  We are getting dangerously close to the point where this work will only be applicable to one truck.

[ddmckee54]

I have found out that I needed to slightly modify my Frankendiff pinion housing design.  The hole for the drive shaft's drive pin wouldn't line up with the hole in the pinion shaft.  I must have fat-fingered a dimension because the outer bearing needed to be moved 1mm toward the axle shaft.  I just had to decrease the extrusion that formed the nose of the pinion housing from 9mm to 8mm.  While I was at it, I went back thru the design and removed anything that I'd done to optimize the design for FDM printing. 

I've got a resin printer now and one of these days I gonna hafta put on my Big Boy pants and actually USE it.

[vtsteam]

What could go wrong?   

[ddmckee54]

What could go wrong?   

Hopefully nothing, but then again Murphy shows up uninvited WAY too often.

[ddmckee54]

Sometimes I think Quality Control is a totally unknown concept in certain parts of the far-east.  Some of the stuff is high quality, but there are a LOT of times when what you actually get is a kit of mostly usable parts.  ALL of the SCX10 rear axles I ordered came from different vendors, but the same supplier, and none of them were really usable when the arrived.  All of them are almost impossible to turn.  I chased that problem back to the fact that they arrived with an interference fit between the spider gears in the differential.  I had to remove 0.3mm from the backside of each axle gear before things started to work properly.  BUT, they are fixable. 

I ordered some plastic bushings for the knuckle pivots on the powered steer axle I'm building.  They were SUPPOSED to have a 3mm ID, it's under 2.8mm.  Fortunately the OD is correct so they also are fixable.

I ordered drive shafts from 3 different manufacturers, 2 out of the 3 suppliers have the knuckles properly phased to minimize vibration.  The third supplier... not so much.  The knuckles are are least 10 degrees out of phase, and I'm not sure if there's going to be any fixing it.

And then, I've got a gotcha that's kinda my own creation.  ALL of the drive shafts that I ordered are SUPPOSED to fit an SCX10, come with a 5mm bore  and have drive pins that are threaded M4 on one end with the other end turned down to 2.5mm.  My axles are SUPPOSED to be SCX10 replacement axles, but they all have holes for 2mm drive pins in the 5mm OD pinion shaft.   I could bore the pinion shafts out to 2.5mm, since the Kong axle that I have has a 5mm pinion shaft with a 2.5mm drive pin hole.  The Unimog replacement twin motor/2-speed gearbox that I got as a power unit has 4mm OD output shafts that are threaded M2.

So, here's my first dilemma, do I modify the pinion shafts?  Or, do I modify the drive pins?  Initially I was leaning towards modifying the drive pins, now I'm not so sure.  If I modify the pinion shafts, I just punch the drive pin holes out to 2.5mm and call it a day.  If I modify the drive pins by turning them down to 2mm, then I also have bush the hole in the drive shaft down to 2mm.  Otherwise they'd be, to quote Wes from Watch Wes Work, "floppin' around like a hot dog in a hallway."  Metal fatigue would probably cause the 2mm pin to break off in a short time.  I think I just talked myself into modifying the pinion shafts.

My second dilemma is that the output shafts on the Unimog transfer case have a 4mm OD.  Bushing the transfer case end of the drive shaft down to 4mm is no problem.  They also have a pre-machined flat that is threaded M2.  My first thought was to bore the M2 threads out to 2mm, since they are effectively that size now.  I was planning on just having one drive pin that would work on either end, but that's just gonna make a lot of extra work for myself.  I think what I'll do for the transfer case drive pins is cut a chunk off the 2.5mm end of the pin and turn the stub down to about 1.5mm - or whatever will fit in the M2 threads.  The set screw on the flat will be the actual clamping/driving force, the little stub is just extra insurance if the set screw comes loose.

Don

[vtsteam]

No idea what you're talking about, Don, without pics anyway, but I trust that you do! As far as overseas purchases go, I always assume a kit of parts, but enjoy the low prices for them, and basically I'm a DIY guy anyway, so if I could just buy everything, and it all arrived in perfect working order, well, what would I have to do for fun? 

[ddmckee54]

what would I have to do for fun? 

Steve, you could always do what I do and complain about the quality of the parts you're getting. 

As far as having a better idea of what I talking about, when I modify the pinion shafts and drive shafts I'll take some pictures and things should become a little more clear.

Don

[vtsteam]

cool! 

[ddmckee54]

I found that Lesu makes a driveshaft with a 40-45mm range.  I initially had 37mm between the center axle and the rear axle.  If I add 5mm to my center/rear axle spacing that will put me in the middle of the Lesu driveshaft's range.  I did some checking, and the only 3D printed part that I really need to modify to do this is the equalizer beam.

Eventually I will have to determine the hole sizes/locations for the frame rails, but that's a problem for future me.

Don