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