The Craftmans Shop > Radio Control Models

Another Bruder conversion

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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 70C, which I believe is the pain threshold (140F).  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.


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,

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!


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!



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