The Craftmans Shop => Radio Control Models => Topic started by: ddmckee54 on November 12, 2020, 01:13:36 PM

Title: Another Bruder conversion
Post by: ddmckee54 on November 12, 2020, 01:13:36 PM
Christmas presents for the kids in several families this year will be something a little different.  A couple of years ago I armed the kids with rubber band guns.  They have to be able to defend themselves during the zombie apocalypse don't they?  Think about it, in ANY of the zombie movie you've ever seen have you ever seen one touch a rubber band?  What I am doing this year is making an RC conversion of the Bruder cross country Jeep.  I've attached the stock Bruder picture of the toy.  My goal is 2 channel RC control with minimal changes to the appearance of the Jeep.

This will be a quick and dirty easy conversion.  It better be, because I've got a Christmas deadline and I'm on the clock here.  I'm making 3 copies of this Jeep, well 4 if you count the prototype.  I've got to make sure it works don't I?  That require rigorous testing, right?  Besides it's just not right to give a kid a used Christmas present - is it.  Properly tested is one thing, but used is quite another.  Anyway, that's my story and I'm sticking to it.

I'm presently gathering the Jeeps, I've got 3 and I should be able to get the 4th tonight.  Radios, ESC's. battery packs, and other miscellaneous stuff ordered from Ebay and other friendly sources has started arriving.

I've got the 3D printed parts designed, and some have been printed.  In some cases the 1st of probably WAY too many parts destined for the "Well that ain't gonna work" box, have already found their new home.

Title: Re: Another Bruder conversion
Post by: Brass_Machine on November 12, 2020, 01:24:47 PM
Cool project!
Title: Re: Another Bruder conversion
Post by: WeldingRod on November 12, 2020, 02:11:35 PM
Could you put thrm back on the box and pack the controls separately?

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Title: Re: Another Bruder conversion
Post by: ddmckee54 on November 12, 2020, 03:43:05 PM

The original box, that's a really good idea - in an evil sort of way.  Some of the kids that one of these Jeeps will be going to are in the 12-13 year old range.  Too bad that Jeep is being shipped to West Virginia, it would be interesting to watch the look on their faces when they open a gift rated for a 3+ year old. (Probably think Uncle Don has finally gone around the bend.) Maybe a little collaboration with their parents and I can get a video of the opening.  Just have to label the boxes with which one gets opened first.  A couple of the kids are only 3-ishThat's a really good idea, in an evil sort of way.  Some of the kids that one of these Jeeps are going to are in the 12-13 year range.  Too bad that Jeep is being shipped to West Virginia, it would be interesting to watch the look on their faces when they open a gift rated for 3+.  Maybe a little collaboration with the parents and I can get a video of the opening.  Just have to label the boxes with which one gets opened first.  A couple of the kids are only 3+ so I figure their Dad will have to show them how to run it, maybe show them a lot - just to be sure they know how to run it.

I should be able to fit it back in the box, which I still have.  I had to increase the wheel track 2-4mm to get the clearance for the gearmotors, it's gotta be 4WD donchyaknow. (MY 3D cad software thinks in millimeters, so you metrically challenged people just deal wit it.)  But other than that I haven't made any major external changes on the Jeep.  So with minor modifications to the interior packing, it SHOULD fit back in the original box.  There will also be four M3 SS button head screws that attach each wheel to the gearmotor via a steel hub.  The wheel rims are a silver plastic so the SS button heads shouldn't be painfully obvious.

I've attached a picture of the radio that I going to use.  It's a 3 channel 2.4GHz radio with a 1S Lipo battery for the transmitter, a USB charger is included.  I got a 1400mA 2S Lipo for the Jeep, it's going to live under the hood where the fake engine used to be and it's also got a USB charger.  I didn't want anybody to have to feed these things a steady diet of AA batteries.  The fake engine had to go to make room for the steering linkage and for the top of the servo.  I had plenty of room above the steering arm, and below the hood, for the battery and a platform to hold the battery. 

The gearmotors that I'm using are 360 RPM @ 6V, and have an 80mA stall current.  I figure that at 7.4V they should be about 400RPM-ish?  This thing should scoot right along, but that's what a throttle is for, you're never too young to learn that lesson.  One 20A ESC will have NO problem with all 4 motors.  The ESC that I got will live under the floor of the Jeep, there's about 10mm-ish of clearance between the bottom of the floor and the top of the frame/belly pan.  The ESC is maybe 6-7mm thick.  The receiver is going to live in the gas tank , I think.  I'll know more tonight when I get home, as I just got an e-mail telling me that the radios, at least 3 of them, were delivered today.  Then I'll know if the receiver will fit in the tank or not.

Title: Re: Another Bruder conversion
Post by: vtsteam on November 12, 2020, 09:43:09 PM
Sounds like a cool project. I do hope you mean LiFe cells for the jeeps and not Lipos, and that you have  suitable safe chargers to go with these, and that they will only be available to sub teens while adults supervise. And of course that the adults understand the risks and charging and storage requirements involved.

Please see:
Title: Re: Another Bruder conversion
Post by: ddmckee54 on November 13, 2020, 10:30:52 AM

They are LiPo's, at least I know the Jeep packs are LiPo's, I'm not sure about the transmitter batteries. 

The chargers for the Jeep packs have a built in cutoff, so I'm not too worried about them.  The charger did get a little warm during the charge.  I could easily touch the charger so it was well below 70°C, which I believe is the pain threshold (140°F).  The battery pack never got warm so I didn't have any worries about it.

The transmitter batteries on the other hand you need to monitor and manually stop the charge, at least that's what the Chinglish manual suggests.  When it's fully charged, the charging LED on the transmitter will go out.  I need to find out if it actually stops charging or just turns out the LED.  It could be that the transmitter charging circuit is shut off when the charging LED goes out

I planned on giving the parents written instructions for charging these batteries.  Maybe suggesting that they also get a charging sack wouldn't hurt anything.

Title: Re: Another Bruder conversion
Post by: ddmckee54 on November 16, 2020, 12:49:21 PM
Well I made some progress over the weekend, I ALMOST have a rolling chassis.  When the motors that I ordered arrived, sometime in the next 2 weeks, I will have a rolling chassis.  I have a couple of spare N20 gearmotors that I'm using to verify the fit, but they are not the correct gear ratio, 100 RPM vs the desired 360 RPM.

I am accumulating a fairly impressive pile of printed parts that didn't QUITE cut the mustard for one reason or another.  Mostly having to do with guesstimated measurements, said guesstimates being made when the tools I had on hand were not suited for the required task.

The greatest aggravation occurred  when I was making/using the wheel drilling jig.  This jig is used to drill the 4 mounting holes required by the hubs that I have for the N20 gearmotors.  When I designed the jig I measured the outside to outside dimension of the holes on the hub, this measured 19mm.  No problem, I laid out a 19mm circle on my model and put four 3.5mm holes at the appropriate locations on that circle.  This 19mm was really convenient because that also happened to be the apparent bolt circle diameter that Bruder used for the 8 fake lug nuts.  I just lined up my jig so that I was putting my holes where 4 of the fake lug nuts are located.  I printed out the drilling jig, it took about 4 tries before I was happy with the fit of the jig and the way the holes lined up with the fake lug nuts.  I then proceeded to drill all 4 holes in all 4 wheels - in the wrong spot.  My 19mm measurement was outside to outside, but I laid the hole CENTERS out on a 19mm circle - should have been a 16mm circle.  Many bad words were uttered as I re-designed the jig, re-printed the jig, and re-drilled the holes using the jig.  It was a royal pain in the gluteus maximus to get the hubs installed.  The fake locking hubs that Bruder molded into the wheels have a 13mm OD, the bolt circle is 16mm, and the M3 button head cap screws that I'm using have a 5.5mm OD.  Can you say it ain't gonna fit without a fight?  I got it to work - for the prototype.  I re-designed the drill jig, AGAIN, and moved the bolt circle out to a 17mm diameter.  By drilling the bolt holes in the hubs out to 4mm the M3 bolts JUST line up.

Thus endth the RANT for the day,
Title: Re: Another Bruder conversion
Post by: ddmckee54 on November 18, 2020, 04:58:13 PM
Good news, the slow boat from China came in, and my gearmotors were on it.  I now have enough gearmotors to do 3 of the 4 Jeeps, the rest of the motors are on another slow boat.

I also now have a rolling chassis.  I couldn't resist and had to pop the body on to check it out, it looks just like the original Jeep - which was kind of the idea.

The way I see it this is what I've got left to do before I've got a runner:
Make and install the steering linkage from the servo to the spindle.
Make and install the tie-rod.
Make and install the 4 motor leads.
Make and install the splitter from the ESC to the motor leads.
Install the ESC under the floorboards.
Install the receiver in the gas tank.
Plug in steering servo and ESC.
Snap the body back in place.
Install the battery pack in the engine bay.
Turn this sucker on and try it out!

Title: Re: Another Bruder conversion
Post by: ddmckee54 on November 19, 2020, 05:40:43 PM
It's sorta Show-N-Tell time, 'cause I gots pictures!

I can take one thing off the to-do list, but I have to add another.  I got the tie rod made last night.  It's not much, but it's something accomplished.  However I realized that I need to change the battery connector on the ESC.  It's currently a 2 pin Dupont type connector on the ESC and the battery has the Dean's T style connector. 

Pictures, I've got a few and some of them are kind of crappy.  That could be the camera's fault, could be mine - I'm gonna blame the camera.

The first attachment is the side view of the Jeep with the body snapped on.  Like I said I couldn't resist once I had a "rolling" chassis.  As you can see it looks almost the same as the standard Bruder Cross-country Jeep.  The only really noticeable difference is that my jeep as 4 M3 button head SS cap screws in each wheel.

The second attachment is a close up view of the wheel.  The button head cap screws aren't that noticeable, they ALMOST look like lug nuts.  (Well that's my story and I'm sticking to it.)

The third attachment is a picture of the underside of the Jeep, showing the front axle and steering arrangement.  I had to move the spring placement inboard from the original location, but the front axle does still articulate.  Everything that's white was 3D printed.  I had a spool of white PLA in the printer and that's good enough for the prototype.  For the Christmas present Jeeps, everything that's 3D printed will be printed in black.  There was a QUITE a bit of surgery required to get room for the 3D printed axle.  The axle isn't much bigger than the original axle, but the original was not designed to allow the wheels to turn, nor to articulate.  It basically just allowed the axle to go up and down a few millimeters.  It didn't really have that much travel either.

The fourth attachment is a crappy picture of the tie rod.  It turns out it was my ONLY picture of the tie rod so we'll have to live with it.

The fifth attachment is another crappy picture, only this time it's of the printed servo mount.

The last attachment is a picture of the rear axle.  Just like the front axle, everything that's white is 3D printed.  Here though I was able to keep the original spring locations.  There was still a fair amount of surgery required to get a decent amount of axle articulation and travel.  Like the front axle the rear axle only moved a couple of millimeters.  I'm not building this to be a rock-crawler, but still, it IS a Jeep!

Title: Re: Another Bruder conversion
Post by: WeldingRod on November 19, 2020, 05:54:08 PM

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Title: Re: Another Bruder conversion
Post by: ddmckee54 on November 23, 2020, 01:25:18 PM
I wasn't completely happy with the way that the parts of the front and rear axles fit together.  The axles are split to allow the gearmotors to be installed and then capture the gearmotors when the axle halves are bolted together.  I thought that the ends of the axles got a little flimsy and I designed a locking ring to slide over the ends of the axles and keep the halves from splitting apart under load.  There are 3D printed parts and while you can design practically any shape, just due to the way a filament type printer builds the part you don't always get the repeatability that you need for a precise fit.  I have to design in some tolerance, and while a little tolerance never hurt, after a while it stacks up.  My locking rings, while they fit, do not stay where I want them to.  This is most noticeable in the picture of the rear axle, on one side the gears are not covered by the locking ring.  The locking ring is supposed to be covering the gears to keep the crap out of them.  This is even more important for the front wheels since those locking rings also have the steering pivots printed on them.

The bottom line is that I have redesigned the ends of the axles and the locking rings.  Instead of trying to fight the tolerance stack-up, I'm going to take advantage of it.  I have designed a detent into the end of the axle and the locking ring.  The ring SHOULD snap into place and then not move - until you WANT to move it.  At least that's the plan.

I've got to print out a new gearmotor carrier and locking ring for a front wheel and see if things actually go to plan.  I'll test it on the front wheel since those parts are smaller and take less time to print.  If it works there it should also work for the rear axle, where I have to print the entire axle to test this, that takes a couple of hours.

3D printers are a lot like shapers in machine shops, you can use them to make just about anything except money.

Title: Re: Another Bruder conversion
Post by: ddmckee54 on November 24, 2020, 11:30:16 AM
I had printer issues last night, I kept getting the "Temperature Error" contact - but I don't need no stinkin' instructions, I are an Enginere, Injunear, I'm good with math!

After about an hour, I actually when to the website and checked out the FAQ's.  They pointed me to the 2 pin connector for the thermistor, which wasn't the problem.  Actually the connector for the ribbon cable that runs from the print-head to the motherboard had come loose.  I plugged it back in and the error message went away.

Consequently I was only able to print out the gearmotor carriers and locking rings for the front axle.  The DO work as intended though, the locking ring now snaps into the detent and doesn't want to move after that.  I CAN still get the locking ring back off if needed, so I can still service/change the gearmotor.  I'll take some pictures after I get the rear axle printed.

Tonight I'll print the revised rear axle, and also print out the jig I designed to allow me to get the bends correct in the 1/16" music wire drag-link for the steering.  The drag-line is 1/16" music wire with a Z bend to keep it in the servo arm, a 110° degree bend then a 123° bend and finally a modified 1/16"x2-56 solder connector for the ball link.  I've got enough parts to make the drag-link for the prototype, but the stuff I ordered is for the rest of the Jeeps is SUPPOSED to be here by Saturday.

I've still got the ESC cables and mounting to take care of, but I should have a running prototype within a week or so.

Title: Re: Another Bruder conversion
Post by: ddmckee54 on November 30, 2020, 06:10:33 PM
I printed out the various modified parts and found out that I need to re-print the battery support, I didn't leave a good path to get the battery lead to the ESC.  I also got the servo steering linkage built up, so once I get the ESC installed I should be able to run this Jeep.

I was ALMOST able to had a running chassis by the end of the Thanksgiving weekend.  If I was trying for 3 wheel drive on a Jeep I would have had a running chassis.  Unfortunately, one of my gearmotors was DOA.  I had to make a One into Four power splitter which involved both solder connections and 2 pin Dupont connectors, and that was my first suspect.  These are teeny-tiny motors so a Dupont connector is more than capable of carrying the individual motor load, 0.8A stalled.

I verified that my power to the motor through the splitter was OK by swapping the DOA motor around with one that was working.  The problem stayed with the DOA motor.  I tried spinning the gearbox over by hand and couldn't turn the output shaft.  I then split the gear reducer and motor apart.  I COULD then turn the reducer, but I COULD NOT turn the motor over.

Tonight I'll try swapping out the DOA gearmotor with one of the other 300 RPM motors - I've got 12-15 more motors for the other Jeeps.  I just hope that the ratio of DOA motors to good motors favors the good motors for the rest of my 300 RPM gearmotors -  time will tell.

Title: Re: Another Bruder conversion
Post by: ddmckee54 on December 02, 2020, 04:36:53 PM
OK, everybody...  Hold your thumb and index-finger as close together as you possibly can without them actually touching.  Now in your very best Maxwell Smart voice say "Missed it by THAT much!"  That's how close I came to actually being able to run the prototype last night.

I got the DOA motor replaced and rotation verified - it actually does turn now when I tell it to.

I got all the motors installed and verified that they were all turning in the proper direction.  When I give it the giddyap signal, they all giddyap in the same direction with nobody marching to a different drummer.

When I turn the wheel on the transmitter the front wheels turn in the expected direction.  I don't have as much steering travel as I'd like, but without carving great big hunks out of the body more travel is just not possible.  Besides, this isn't really a rock-crawler, it's just drawn that way.

I got the wiring completed and the body reinstalled, everything is now residing in its' new permanent home.

I got the new battery support plate printed and installed.  The battery is hiding under the hood, bonnet if you're from
THAT side of the pond.  And the hood still snaps shut, just like it's supposed to do.

From the outside the only difference that is noticeable between my prototype and the original toy, is the four M3 button head bolts in each wheel - and they aren't THAT obvious.

The only thing I didn't get done before I went to bed last night was putting the wheels back on.  I'll do that tonight, then we'll see how the dog reacts to an invader on his turf.

Title: Re: Another Bruder conversion
Post by: ddmckee54 on December 03, 2020, 11:30:49 AM

I was able to get the beast running last night and it survived - at least for a while.  We were testing it at the office this morning and everybody decided that it will be a definite hit at Christmas.  It will climb over a fairly good sized obstacle, we laid a manufacturer's catalog about 1" thick on the floor and the Jeep had no problem going up and over it - so it lives up to its' Jeep heritage.

There are a couple of issues that I need to deal with yet:

1) I've got to do something about the M3 grub screws in the wheel hubs - the wheels fall off which is not a good thing for a Christmas present.  Remember the scene from the Santa Claus movie in 1985 with Dudley Moore?  Where the wheels fell off the toys while they were being used - not gonna happen on MY watch.  I'm not sure if the M3 grub screws originally supplied with the hubs were made out of peanut butter or cheese-whiz, but I'm pretty sure it wasn't steel.  I've got some new M3 grub screws ordered, we'll see if that helps.  I may just have to get some M3 socket head cap screws of the right length, 'cause you sure can't put any torque on the original M3 grub screws.

2) My printed detent on the locking rings for the gearmotors were not very durable, the rings will still slide around.  I've modified the locking ring/axle designs to allow me to use an M2x4mm self tapping screw to lock the parts in place.  I should have the self-tappers in about a week.  I'm going to print out the replacement prototype parts in white, then I'm going to switch the filament in the printer to black and start printing the parts for the other 3 Jeeps.  While I'm waiting for parts I can be printing the replacement parts, and performing the various required surgeries on the other Jeeps.

3) I wasn't happy with the way I made the 1 into 4 ESC power splitter.  It involved too much soldering and crimping of Dupont terminals, and took TOO DAMNED LONG to make.  It just took too much fiddling around to construct, and there were so many places it could break.  I dug through my stash of perf boards/experimenters' boards and other electronic odd and sods, and came up with an experimenters' board that I could easily modify.  I've got some PCB header pins that I can solder to that board, and quickly build the same type of splitter.  I whacked a chunk off the board last night and started modifying it to suit its' new purpose.

Other than making a BONEHEAD blunder and drilling through the floorboard while making an opening in the firewall for the battery connector to fit through, I'm pretty happy with how the prototype turned out.  And it STILL looks like this attachment.

Title: Re: Another Bruder conversion
Post by: ddmckee54 on December 04, 2020, 05:45:53 PM
The wheel hubs are threaded M3.  I don't have any M3 socket head cap screws in stock, but I DO have a plethora of M3 SS button head cap screws....  So I tried a couple of them to see if they'd work any better than the M3 grub screws.  They seem to eliminate the Jeep's annoying habit of letting the wheels fall off.  I wasn't sure if I wanted to use the 6mm length, or the 10mm length, so I ordered a bunch of each.  I've got a LOT of Bruder stuff sitting on the shelf waiting for RC conversion, so I'll probably use both lengths somewhere/sometime in the future.

And another thing... 
While I was looking at the wheel hub attachment I noticed that one of my solder connections to one of the front axle N20 gearmotors had come loose, those connections always had been kind of shaky because of the way I routed the wires.  I need to come up with some kind of a strain relief for those connections, so that'll mean another re-design of the front axle and spindles.  The rear axle gearmotors I'm not worried about since those motors do not move in relation to the axle.

This is why I build and test the prototype.  It's not all just fun and games, I promise!!
Title: Re: Another Bruder conversion
Post by: ddmckee54 on December 08, 2020, 11:55:42 AM
M2 self tappers and the M3 socket head cap screws are supposed to arrive in the next few days.

Over the weekend I re-designed the front axle gearmotor mounts to include a strain relief for the motor wires.  The way I had them originally routed, I knew the wires would probably break from the flexing, I just didn't think they would break that fast.  I design industrial electrical control systems for a living so I SHOULD have known better, I just wanted to see it move under it's own power.  I designed a wire strain relief that is printed into the gearmotor mount and had to redesign the front axle to provide a little more clearance to give the wires a few millimeters of airspace to move around in.  I had to do this TWICE.  The first iteration I only allowed a 1mm slot for wires to fit into.  The 26AWG red/black pair that I am using IS 1mm thick so it should work, right?  Ummmm…. not so much, the wires could be forced into the slot but when they were removed there was visible damage to the insulation.  So on the second iteration of the design I opened the slot up to 1.25mm and I get a nice firm fit in the slot with no damage to the insulation.

I'm going to need to make the front motor leads at least an inch longer than they currently are and the rear motor leads will also need to be longer, I moved the position of the ESC, and I found a good home for the new 4 way splitter that will clean up the wiring mess a little.  I also started work on the 4 way splitters to the motors last night, and I am REALLY liking the way they are going to look.  It doesn't look like something a Mad Scientist cobbled together anymore. 

When I get the screws that I ordered I'll take a couple of pictures of the final installation on the prototype.  The white 3D printed parts that I'm using on the prototype will show up much better in the pictures than the black that I'm going to use on the gift Jeeps.

I have a very impressive pile of 3D printed parts that DIDN'T quite cut the mustard, but the STL files that I have now I KNOW will work for the gift Jeeps.  It takes about 6 hours to print out the required parts for the front and rear axles and the other miscellaneous parts. 

Title: Re: Another Bruder conversion
Post by: ddmckee54 on December 22, 2020, 10:35:53 AM
It's gonna be a late Christmas this year, I still haven't got my M3 Socket head cap screws.  I got some M3 grub screws, but they were only a slightly better grade of cheese-whiz than the original set screws.  My socket heads have cleared customs and are "In Transit", I expect them within the next couple of days.  I've got the 4 way splitters built and I made 3D printed brackets to hold them in place.  I don't cringe anymore whenever I look at the wiring, so that's a good sign.  I'll take some pictures when I get the wheels back on.  It looks kind of pathetic right now just sitting on the frame rails, I suppose I could 3D print some jack stands?