Walker Evans Rock Spider RC Crawler

[jsudar]

Many of you will remember Walker Evans’ IFS/IRS Rock Spider S10 buggy. It was built around 2003. It was short lived— I don’t know if he even drove it the whole season before going back to solid axles. Turning radius wasn’t great, among other undisclosed issues.
It had a very unique leading/trailing arm suspension system that looked sooooo cool. Easily one of my favorite buggies.
Fell in love with it back then, made a feeble attempt to build a baby one out of TMaxx parts and shelved the project.
Now that it’s been twenty years, I’m taking another crack at building a baby Rock Spider.

Here’s the plan:
1/8 scale buggy differentials, dog bones and knuckles.
Axial SCX10 tranny with Super Shafty 8mm outputs (to work with the 1/8 scale buggy shafts)
Holmes Hobbies stubby Puller 1200kv with a Castle ESC on 4s LiPo
Proline Cliffhanger body
Motoworx beadlocks
Dual Hitec 945MG servos on a Y harness
Billet chassis

 

[jsudar]

This is the main chassis plate. Most everything will attach to it. Started life as a 300 gram chunk of 3/8” aluminum bar. Hopefully it will be half that weight when I’m finished machining out my “speed pockets” Can’t do speed holes on a skid plate, I’d get hung up on ALL the rocks. And look at those cute little M4 rod ends!!!

Two 2s LiPo packs. They will be wired to function and charge as one 4s pack, but splitting the pack up gives better weight distribution and placement.

Helical cut 4.3:1 R&P on some custom machined 1/8 scale buggy spools I bought back in 2010.

That’s what 8mm outputs look like on an Axial tranny. No, I’m not compensating. Case is a Vanquish aluminum unit with stock plastic gears I got from @Corban_White when he upgraded his Wraith. Can’t wait to blow them up.

Obligatory kitchen table planning photo. Wheelbase will be 350mm. Width is 270mm hex to hex.

 

[I Lean]

Watching! I remember that rig very well from when it debuted. 🙂

 

[jsudar]

Got a set of four of these Motoworx beadlock wheels on eBay. Two of them have broken off M2 screws in them. Sadness. Why they used stainless hardware I’ll never know… it’s only 70k psi tensile and freaking 2mm! The black oxide coated stuff is good for 170k psi. So I’ll be changing out the hardware. They are some of the few wheels that fit a 2.2 tire and have a 17mm hex. And they are way expensive. That’s why I had to go with used ones and deal with broken hardware (the seller disclosed this)


A 1/16” end mill with lots of pecking and patience is how you remove broken M2 screws.

 

[Gravy]

I remember seeing that thing. It's like vw trailing arms in front and rear. Like a utv Before they were a thing. Spaceship!

 

[James K]

Very cool

 

[Agility Customs]

That rig is still competing in the promod class currently. Kind of cool its been around so long.

 

[jsudar]

I read somewhere Walker said the Rock Spider worked excellent on 9 out of 10 obstacles. However, on the tenth obstacle it was so bad, they lost whatever advantage they had gained in the first nine.
I never saw the real one in action, so I figured it was probably worth a few hundred dollars and 50 or 60 hours of my time to find out what the “tenth” obstacle was. Oh the mystery!!
Also this forum needed a little life breathed into it— one of the more recent posts was from me back in 2021 last time I had an itch to work on an RC project.

 

[jsudar]

That rig is still competing in the promod class currently. Kind of cool it’s been around so long.

Really? I heard they tore it down and destroyed their fancy CV axles so none of the other kids could play with them. Interwebs rumors…
That’s awesome it’s still in action.

 

[jsudar]

Finished the rest of the slots of the suspension arms. Still need to drill and tap a few set screw holes to retain the repurposed 1/8 scale buggy A arm pivot pins that the rods ends ride on.



Milled out another speed pocket to maximize acceleration. The one on the other side of the chassis will be trickier— two of the tranny mount bolts go through there so it won’t just be a rectangular pocket. It will be a Utah shaped pocket. It’s only tricky because I don’t have a DRO on my mill so there is lots of counting handle turns involved. Which is fine until someone wants to have conversation with me about polynomials while I’m trying to count….

 

[jsudar]

Got the other pocket milled out and the set screw holes drilled and tapped. Trans is located and mounted.



Still need to countersink two of the trans bolts. However, I’m using metric bolts and they require a 90* countersink. SAE bolts require an 82* countersink which is the standard variety you’ll find at the local hardware store. I have a half dozen of those, so now I’m waiting on a 0 flute 90* countersink from McMaster Carr.