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Micro R/C Trux! Anything smaller than 1/12 scale. VMGs, Mini Z's etc!


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  #61  
Old 05-15-2019, 06:31 AM
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Awesome thanks for that, I'll check it out as soon I have a chance. Been going cross-eyed on the tig at work lol
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  #62  
Old 05-17-2019, 06:59 AM
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Yay... It fell apart......... sort of

That was a real mission to get it apart. If you ever try this, the hardest thing to get undone was the "pods" on the sides. They hide a couple of tabs inside and the only way I could get them apart was to basically force them off and sort of sacrifice a tag or two. The problem is you can't easily get to the tab holding the grey steps in.

Overall I didn't break too much and once I get the wheels off I can start to figure things out.
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  #63  
Old 05-18-2019, 09:30 PM
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The wheels on these are ridiculously difficult to remove. I made a quick spreader to wind pressure in as I warmed up the plastic with the heat gun to get the front axle apart. That didn't work for the back axle, not enough room and didn't want to mess up the plastic chassis with heat. So brainwave.. Grip the wheel in the lathe and pull the other while it spins. Worked great. Chewed the plastic a little where the knurling on the steel axle came out but not fussed.

I'm hoping to use the original wheels with probably a hub of some kind to hook up to a losi micro axle or similar, depends what I've got that fits.
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  #64  
Old 05-20-2019, 09:13 PM
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Does the rollout between your front/rear look like you can gear around it to get 4wd, or just keeping it Rwd?

I like the accessory hubs some of the places selling gearmotors carry. If you're going losi micro, probably scrap a set of those rims to make adapters

My fork was able to get by with an epoxy putty 'bushing' that was formed in place between the output shaft and hub. Then it was pulled out and CA back into the wheel. But that's with 150rpm motor on little tiny wheels, so it won't amplify runout as much..
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  #65  
Old 05-21-2019, 06:32 AM
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I haven't measured that up yet, was wondering the same thing. If it doesn't add up nicely I think it's fine being only Rwd. Guess it depends how much traction it can muster like that.

I'll have a look around for those, might make it easier as I was thinking of doing something to fill the open backs of the wheels. Maybe some extra weight would be good for it too. Epoxy putty could help there too.
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  #66  
Old 05-21-2019, 08:21 PM
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I measured it out but I don't know what to do with the answer.

Back wheel 230mm roll-out
Front wheel 170mm
Gives 1:1.35 ratio

If I used the losi transmission, what would I need to do to the output to make the same rotation speed?
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  #67  
Old 05-22-2019, 07:42 PM
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The butchery has begun..

I've worked out how to adapt the wheels, shave away the excess plastic of the original axle support but leave enough to act as a key into the recess on the standard losi wheel. With the beadlock ring removed I can use the screws to mount the modified bruder to the rim. I need some longer screws but calling that a win for now.

Began trying to fit the axle in the rear.

It's fitting in there, the width is almost perfect but could maybe do with a shim between the bruder and losi hubs to gain a little breathing space, it's very close to rubbing the inner edge of the tyre.

Partial win.. I'm dopey though and didn't account for the relative thickness of the losi putting the axle center higher than it should be. I really should have cut from the bottom up rather than top down but I was trying to retain the moulded "diff" in the bruder shell. Might have to rebuild the top slot and start again from the bottom to get the axle low enough. Not the end of the world.
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  #68  
Old 06-19-2019, 01:11 AM
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I got a chance to sit down and butcher a bit more plastic, the rear axle now sits as low as I can make it. Way more plastic got cut away than I really wanted to but after starting from the top I had no choice but to keep going. As I said before, if I could start over I would cut away from underneath and sacrifice the original moldings.


Had to open up some "windows" to clear the screws and things on the axle.

Now I'll have to figure out what to cut from the middle... Probably everything.
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  #69  
Old 06-20-2019, 10:27 PM
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Thats a small nut!
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Buying lots of parts, but haven't built a rig in years
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  #70  
Old 06-20-2019, 10:36 PM
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More cutting, trial and error... Thankfully so far not too much error. I've got the losi front axle sitting in the space nicely now, not mounted or anything yet but rests neatly in place for mocking up. I cut away from underneath for the front because the axle sits under the frame anyway.

I cut away a lot of the central casting in an attempt to use the losi transmission as well. I thought it was going well with modified antenna tube for drive shafts, until..

I realised how much higher the trans is above the frame and I don't think (or want) to cut into the floor of the cab area. Might have to hunt around for a more low profile motor option.

Arrow indicates the top of the trans above the hull line.
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  #71  
Old 06-20-2019, 10:49 PM
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Quote:
Originally Posted by GULA View Post
Thats a small nut!
Those losi axles are tiny! I used the ink tube from a ballpoint pen as a spacer shim to make the front wheels slip on to them. Ink tube pressed into the bruder wheel hub then that pressed onto the losi.
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  #72  
Old 06-20-2019, 11:12 PM
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Quote:
Originally Posted by 2redrovers View Post
I measured it out but I don't know what to do with the answer.

Back wheel 230mm roll-out
Front wheel 170mm
Gives 1:1.35 ratio

If I used the losi transmission, what would I need to do to the output to make the same rotation speed?
You'd need to scratch build a reduction box around some gears giving a 1.35:1 ratio, find room to mount it, and keep drivelines happy... it's just that easy!

If you ditch the losi trans and went straight gearmotors to the axle like n20 or clones
https://www.pololu.com/product/997

75 and 100 are close to 1.35... 75x1.35=101.25 front overdrive slightly
150 and 210 are close to 1.35... 150.58x1.35=203 rear overdrive some

Bruder bulldozers, skidsteers, an WPL crawler conversion often run this size motor around the 150 ratio, so it should be about right.

That's some nice carnage ya got going on.
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  #73  
Old 06-21-2019, 08:15 PM
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It's awesome carnage isn't it? Thanks for figuring out the maths on the gear motors for me. Right at the moment 1+1 is complex algebra to me. (currently sitting in a hospital room with Mrs and a rather stubborn and reluctant young miss that is too comfortable and doesn't want to give up her bedwomb like she's supposed to)

OK so if I look at the 150/210 combo it should work with the losi axles reduction for a reasonable result. I'm not sure how I'll work the steering yet as I think I have conflicts, might need some thinner links. After trialing the trans I was thinking about the gear motors but hadn't thought anything beyond general concept.

I've shaved a lot of plastic but so far I don't think i've stuffed it up yet. I'm going to rebuild around the axles when I'm happy to lock it in place for good.
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  #74  
Old 06-22-2019, 12:07 AM
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Well when young Miss Rover is ready to leave her Womb with a View, i believe 1=1 may become too complicated for a while.

I'd probably mount the rear axle solid, so it's a more stable base for backhoe, and it should help keep the bucket tracking better. Wonder if you could punch some long screws through the side walls and into the axle top plate to tie it together?

Maybe some collars with setscrews to couple the motor to axles, maybe a driveshaft to front if you don't perfectly center suspension arc?
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  #75  
Old 06-22-2019, 01:55 AM
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Yeah was going to mount the rear solid, probably like you said with screws through the sides. Pack gaps with epoxy or hot glue maybe...

Front for now is probably going to be solid too or very minor wiggle. I'm not going to be too adventurous with it because it will just make steering more complicated.

Young Miss Rover has decided to finally pack her bags and take a ride on the water slide. So some time tonight our time, there should be another addition to the garage
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