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My New Build
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redshift
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My New Build - 07.30.2010, 09:58 PM

Maxx Mutation, meet your replacement.

This one was started the end of 2009, and was originally going to be a twin inline outrunner chassis. I ended up deciding against that for numerous reasons. Simplicity was still a design priority however, so that meant it would not have a transmission. But being a pure basher, and not a racer, a center diff was not that appealing to me. I briefly considered a belt drive, specifically SDP-SI's new Conidrive series, but the available ratios would not have been easy to design around (driven pulley diameter and belt length). My next choice was Mod 1 gears, and the LST2's 63T spur fit the bill. Enough diameter to the keep the stress radius to a minimum. And keep it plastic hopefully, knowing I could switch to steel if needed. So my next move was drawing up the motor mount, which is a stressed member in this case. It is made of 1/2" aluminum, and I knew I wanted a centerdrive with an 8mm shaft. Having 1/2" to play with I went ahead and used two 8x16 bearings, where one would have been more than adequate.
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redshift
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07.30.2010, 10:04 PM

Next was the centershaft, no question this would be stainless, and I cut this out of a 5 or 6 pound chunk of 2.5" 304. If you were wondering, ten hours were spent on this part alone. I had made 8mm drive cups out of air-hardening for use with the outrunner (Mike was out of them at the time) so those are now being used on the centershaft.

Lots of photos to come... keep watching
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redshift
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07.31.2010, 04:25 PM

The motor mount was done knowing what I wanted to do for a chassis, obviously. :) And at that point I had a CC 1520 in mind. The idea of that motor hanging on two 3mm screws didn't sit well with me, so all four holes would be used. That's why the screw slots in the motor mount are so long.

I found where the pinion (RCM of course!) would sit on the shaft and made a ball divit with a diamond ball burr. I consider this a must to not have issues with the pinion. A tiny amount of red Loctite on the pinion setcrew, and it's trouble-free.
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redshift
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07.31.2010, 04:32 PM

On to the chassis...

Square tube is the simplest and strongest backbone, and after finding my dimensions I welded some chunks of aluminum onto the tubes. Four on each end, that would have gaps subsequently milled out, then end-drilled. The welds were then rough-cleaned-up using both inner and outer radius mills, and the setscrew pin retainers drilled and tapped. Next up was the joiner plate holes, the joiner plates themselves, and the provisions for the motor mount and aft bearing block were then done. As you'll imagine, this was a ton of work... and I still have finish work, mostly on the A-arm pivots.
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redshift
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07.31.2010, 04:36 PM

More...
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redshift
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07.31.2010, 04:41 PM

The main tube is 1.75" outside, 1.5" inside, 1/8" wall. Joiner plates are 1/8" thick as well.
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redshift
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07.31.2010, 04:48 PM

Coming together now
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redshift
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07.31.2010, 04:54 PM

I then made 'cartridges' for the diffs, these were milled out of plastic. The square end blocks with the hole for the diff input stays intact and serves as a stop for the two side pieces when installing the diff. I am using 10-32 blind nuts in the side pieces, because the end chassis holes will also be bumper mounts. Those will take far more torque than the 1/8" aluminum tapped out, and are replaceable. Bumpers have yet to be made, too many ideas and I can't settle on one, kinda frustrating!
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redshift
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07.31.2010, 05:04 PM

Then I had to come up with some half-ass battery holders. These will likely be changed, still a ways to go on finishing this one up. More to come!
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07.31.2010, 05:10 PM

....
   
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Bondonutz
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07.31.2010, 05:34 PM

Very Impressive work so far Bro, Looking great !


I retired from RC, now life is all about guns and long range shooting.
   
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magman
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07.31.2010, 06:57 PM

Holy shiz that is nice work. Curious to see what your ride weighs when done


1. MBX-6 T8 1900KV, RX8 ON 4S
2. MBX-5T 1520, MMM ON 5S
3. MBX-5 ONROAD CONVERSION 1515, MMM ON 5S
4. MRX-3 ON ROAD CONVERSION 1512, MMM ON 6S
5. TEN T 2650 T8, MMP ON 3S
   
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redshift
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07.31.2010, 09:23 PM

Thanks guys :)

I took a fair amount of time looking at various manufacturer's suspension parts, and settled on the LST2/Muggy bits. Prices are better than what I was used to seeing with Traxxas parts, by a lot. And I definitely wanted away from the Traxxas knuckle setup, so next up, suspension. I knew I wanted a laydown shock angle to keep the towers short. Experimenting a little, I figured out I didn't need towers at all. Yes, some Maxx parts found new life here. And already having the heavy Trinity springs made this work. I actually changed nothing other than preload spacers, they still have 45wt silicone, and single hole pistons. Only 4 of them vs. 8 on the Maxx. Delrin spacers were made to take up the clearance on the 4mm pin on top, and I made the lower shock mounts to get my ride height, those still need some finish work. The suspension is very Revo-ish feeling now, very compliant without being undersprung. In fact I liken it to Revo suspension without the cantilever linkages. The results here were far better than expected! No towers means I have unlimited options for body layouts, so that's a huge plus.
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redshift
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07.31.2010, 09:29 PM

Few more...
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redshift
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07.31.2010, 09:38 PM

And the steering. I bought the Muggy bellcrank setup on linc's advice, but I could not make it work on this chassis without the bellcrank lower pivots ending up over 1/4" below the bottom of the chassis. So then I got experimenting some more (this was actually a long process) and finally landed on a fully independent servo setup. The huge advantage of this is significantly reduced slop, because there are four fewer joints to create play. The downside is the servo horn becomes the sacrificial part. I tried running twin Ofna HD servo savers and that had the tendency to pull the front wheels into excessive toe-in on throttle, and toe-out on braking. So no go, had to be servo-saverless. Muggy owners will know at a certain point the end of the bellcrank contacts the upper A-arm. The Hitec horns I'm using are about 10mm further back from the diff center, which did not change bumpsteer, and no contact!

Wheels are next...
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