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The HPI Project

OSRC

I wanna be Dave
Joined
Sep 1, 2011
Messages
4,334
Location
Douglassville, PA
A while ago (was it really 2 years ago??) I posted this in the Cmaxx thread... wondering if I should build an HPI based IS crawler. I started bending the chassis to give it a raised center and ended up snapping it in 1/2. Well hell, that was the end of that.
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Nothing really goes away in the OSRC shop, it just goes on the shelf to maybe rise another day. Well, today's the day! Sort of. I had in mind some kind of funky rock buggy and turns out by flipping the rear arms the wheelbase was pretty close to the stock MT chassis length. So I did some mixing and matching and ended up with this. With the stock chassis, it'll be a belly dragger but that's ok. CG will be pretty low, so it's a good tradeoff. Stock chassis isn't ideal, but I'm out of metal and it's what I've got. Cut down the shock towers and played around a bit to get the shocks to lay down. I get as much travel as the arms will allow, and the springs are hard enough to keep it all supported.
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Mocking up some parts at the moment, though the R2 trans is going to stay - I need the clearance. I hate the long shaft output, but the short shaft conversion is long out of stock. I might have one here somewhere, I have a vague recollection of buying one... I think it's here somewhere. Or I'll just eventually cut down the long shaft - it'll work as is for now. Tamiya M06 dogbone out back and a long associated up front fit perfectly. Gear cases are filled with Axial OD gears up front and stock out back both with Axial lockers.
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Like the Telly and Pede crawlers, this chassis gives lots of options. 3 different widths and 2 different chassis lengths with 4 WB options.. OR unlimited really as making a new one isn't too difficult (unless you try to bend it!!)
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Got the trans and servo mounted, and a body cut up and fitted. I like the idea of a rock buggy (just for something different) and this old Parma body has been here for ages. Had to cut off the nose, but it tucks down nicely. With the wide MT arms, 2.2's are the only thing that looks right. I set the body on the other chassis and with the super nitro arms and 1.9's it looks pretty good too. It's good to have options! I had to move the trans back a little further than I would like to tuck under the body, but it's definitely got a front weight bias as is. I think it's off to a good start.
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This project has been festering on my workbench for years. I just keep moving it around to get to other stuff. Decided to bite the bullet and get it finished.

Where it stands... Some old cut up Flat Iron 2.2's seemed to fit the best, and the beadlocks have the perfect offset. Wheels will stay, not sold on the tires yet but the overall size is good.
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I never really warmed to the RC4WD transmission setup - that extended output just didn't look like it was going to last long. I tried out an Axial trans hoping it would fit under the body, and it *just* clears once I flipped it to put the motor on the other side.
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The stock chassis was drilled more times than Lily Phillips, and didn't quite fit the body so I cut up my last piece of aluminum stock. 3mm 6061 for strength. Haven't bought aluminum in a while, I was checking out prices and looks like the sheets went up about 150% (!!) since I last bought. Ridiculous. I used another 3MM SNRS4R chassis as a template, clamped them together and started drilling.
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Got the axle assemblies mocked up - Fits the body perfectly!
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I had to swap the diff outputs over to pinned outputs... found some upgraded 13/38 HD gears and some metal lockers in my stash, so in they went front and rear.
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Trans and servo mocked up, and threw in my homebrew battery tray. Crammed all the heavy parts up front as much as possible. Weight balance is way more forward - not bad for an old nitro truck. Have to do a bit of filing on the chassis to get the diffs to sit level, but it's getting closer to reality.
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I feel like the only guy here not building an Optic. I know VP got pissed and while ago and abandoned this site, but right now it's basically an VP builders site! Maybe they want to come back and take a second look.

Anyhow, on to my regularly scheduled old junk pile...

Did some parts mining, I know I have aluminum diff cases here somewhere. I found one, the other is still in the nether somewhere. I managed to dig out a huge pile of parts -I have a spare SNR chassis and after some digging I've got a ton of suspension options. 4 different track widths and 4 different WB options. There's another build in here somewhere, though I only plan to build a crawler out of one of them.
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Love the adaptability of this platform... I've got 2 drag cars currently built with it - electric conversions on a RS43 and SNR. I don't drag race anymore, but both of these were seriously quick drag cars - especially the RS43. I may mine some parts off later.
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In any case, there's plenty to keep busy messing with this winter.

Back to the current build, I went back through the mockup and finished up a bunch of details. Did some more trimming on the chassis so the diff would sit flush and countersunk all the holes - it's all nice and flat on the bottom now. I tore apart the trans and diffs and cleaned, lubed and shimmed everything so it's nice and smooth. Front gears are a little crunchy still but they should wear in.

I found the HPI drive cups didn't like the solid spools - one side fit in fine, the other wouldn't slide in all the way. After a few attempts to make it fit I gave up and just threw an Axial locker in both stock diff cases. Much better fit and I used some small Tamiya foams in the cups to keep the diff outputs from walking out. Feels solid enough, we'll see how it holds up. I put the new found aluminum diff case in the rear - I figured it would take more abuse back there. When I find the other one I'll put it in front.
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Swapped tires over to some old Losi tires that are a bit taller for more GC and started working on bumpers. Not sure what I'm doing here yet, but I like the way this looks. I really need to get some steel rod and my brazing tools out one of these days - metal fab work is not my forte. I have all the stuff, I just suck at it. :)
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