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….Best laid plans….:

Ok, so my previous RC10 runner a.k.a. “The Mutant” was done, had to check every nut and bolt after every run and it had already worn out it’s second chassis. But it was build in…well… ehhmmm... 2009, that explaines a lot;-)

Anyway, so it was economically unviable to resurrect it. Since it basically needed all new parts.
But since the recent Re-Re drops by AE, it was possible to build a new runner.

So the cool hip thing to do is a long-arm, bigbore shocks, GT midmotor beast. But I wanted something a bit more basic/boring. So short-arm, small-bore shocks.

I did want to give the ability to run a geardiff since our track was converted to astro. So my main “cheat” was a JC transmission case to run more modern internals. While on their site I also got RPM cups and an extra set of arms. (It said “add to your basket”. So I thought it was an order to do so, not a suggestion. Sounds plausible….right…. ? Ok, moving on)

….Soft spine….:

Whohoo, building time.

So ‘1st step, do a quick mockup of the nose, rear hangers and transmission. I knew the chassis was quite thin/soft. So I wanted to give it a 1mm stainless steel spine. I had some gauge stainless steel strips that I normally use to make battery weights. So I cut a piece to fit the middle of the chassis, and to fit between the rear suspension hangers. I used some thin double sides tape to secure it to the tub.
Actually worked amazingly well. And the servo battery brace and rear bulkhead also make sure it’s not going anywhere.


….Driven….:

So the biggest change on the car is obviously the JC-racing transmission housing. The quality of the plastic looked quite decent, to had some confidence in it’s use. A B6 balldiff dropped right in. But had to do a bit of shaving to get a geardiff in without light binding issues installed. I pulled the diff from another car, and it was filled with 7K-2G. Seemed ok, so good to go. Since I want to transmission to be as “install and forget” as possible I also dropped an Exotek steel topshaft in the casing.


….well that’s just low…:

It started the the idea that I wanted to alter the front kick-up of the arms. To achieve this I simply put a few shims in the back of the front bulkhead. Also cut a bit of the inside of the front arms so the e-clip is placed more inside the arms, so I don’t loose them all the time. Also dremeled the front shocktower a bit since it was now rubbing on the chassis tubes.
Since the front suspension was now raised on the chassis I did the same for the rear. Made some room in the bulkhead so I could also raise the suspension mounts.
Also dropped the rear spoiler by about 5mm


….Bits and bobs…:

Lot’s of small things were carried over from “the Mutant” like the Fibre-lyte shocktower en transmission brace. The battery mount was also carried over (I think it was TLR…) as was the ball bearing steering rack, Lunsford tie-rods, modified B2 front axles and the front shocktower protector (not pretty, but I does it’s job well)
FanRC CVA’s, rear hubs, 0 deg. casterblocks and slipperplates were used. And I was lucky enough to find a couple of old crushtubes for the rear hubs to protect the rear wheel bearings.

I used the black shock caps for another car. So I used gold caps that were left.

Pistons are old black and red 3-hole pistons from Losi

Last but not least RPM ballcups, as any self respecting vintage runner should have

…. unforeseen consequences….:

Now to put all the parts together and job done.

…… Drats….. a couple of issues.

Misalignment of motorplate: the motorplate was about 1,5mm off the mounting holes for the chassis. Should have checked extra in hindsight since the thread of the motorplate screws where protruding a lot. But I just figured the JC-racing hardware was just on the “safe side”. So disassembled the transmission added some shims, and problem solved. But still a small knock on an otherwise really nice looking product.

before: after:
Rear shocks were a bit long for this chassis setup, when fully compressed the chassis was not hitting the floor. So I wanted to use a bit shorter shockbodies. Looked in the parts bin I found an old set of shocks that were pulled from a B4. Even with the shorter body’s and shafts the travel was more than enough.
Last on the “list of annoyance” was steering rub at full-lock. This because I installed 0 deg. casterblocks since I already reduced the kick-up and caster on the front suspension mounts. Solution was simple enough just cut a bit of material from the casterblocks, so the turnbuckle is placed slightly more forward.

….notes/rants/excuses ? …:

Not really, I wanted to keep it sort of simple. Was contemplating to cut the motorplate and chassis edges. But since the chassis is kinda weak as is, I left it alone.

The FanRC stuff…. Meh… the plastic for the hubs and casterblocks are fine. Not 100% on the slipperplates and driveshafs. We’ll see how they last. But now it will deal.

Performance wise a slipper weight would help to keep the nose in check when accelerating, and different rear toe would help rotation a bit. But now it’s able to drive in both wet en dry conditions without changing the setup. Time will tell when it hits other circuits than my home track.
I know it's not "pretty", but in the words of Freiburger "Don't make it right, just get it running"


Now all I need is a new name for this car……….

For reference, this was the previous runner:

"The Mutant"
https://www.rc10talk.com/viewtopic.php?p=99900#p99900

Very nice runner build Janus. To help with the front turnbuckles rubbing at full lock with rpm style ballcups, do you have the black "short neck" ballstuds? They are about 1-1.5mm shorter than the regular silver ball studs and help the upper camber link clear the lower steering rod at full lock. The links may still rub but it will now only be when the arm is near full compression. AE makes them in both standard (#3983) and metric (#31281) thread, but the standard thread are discontinued and its really the only place on the entire car that needs them.

carloco8 wrote: ↑Tue Apr 22, 2025 4:09 pm Very nice runner build Janus. To help with the front turnbuckles rubbing at full lock with rpm style ballcups, do you have the black "short neck" ballstuds?

Hi Carloco,

Thanks for the suggestion.

I have some but they were "well used".
(Why am I keeping them around anyway? Sure I'm the only one on this forum with that problem......)

So "when in doubt use a Dremel".
I just thinned out the ballstud mount hole on the casterblocks by 2mm. Now it's just fine.
Picture before the cut. Black line is now removed


Picture after the cut

Can you explain the castor again please? I didn't follow. Why shim the bulkhead/chassis vs just using different castor blocks? Is the effect on performance different when adjusting at the chassis vs at the wheel? I ask because the Cougar had the castor adjustment at the chassis BITD when everyone else was doing it at the wheel. I assumed it was just a clever low cost alternative (remove a shim vs buying castor blocks), but maybe they had another reason.

1911Colt wrote: ↑Wed Apr 23, 2025 8:53 am Can you explain the castor again please? I didn't follow. Why shim the bulkhead/chassis vs just using different castor blocks? Is the effect on performance different when adjusting at the chassis vs at the wheel? I ask because the Cougar had the castor adjustment at the chassis BITD when everyone else was doing it at the wheel. I assumed it was just a clever low cost alternative (remove a shim vs buying castor blocks), but maybe they had another reason.

Caster and Kick up are related but don't do exactly the same thing.

Caster (changing the caster blocks) affects camber gain when turning the steering. More of it generally makes the car more stable in a straight line, and is smoother on bumpy tracks but kills off power steering. Less is the opposite

Kick up (changing the bulkhead angle) also changes the angle of the arms so this has different effects added: More kick up increases how much the nose dives during braking and improves handling in bumpy sections this makes the steering a but less reactive though. Decreasing kick up, like what he's doing here with the washers, decreases dive on braking and makes the car more reactive to steering inputs. This comes at a cost for bumpy sections as the car can get unpredictable in them.

Both things should be treated as different tuning features. if you adjust the kick up it's going to affect the total caster as well, but not vise versa and changing caster blocks won't change kick up, only tilting the bulkhead/inner arm mounts does this. To maintain current caster while reducing kick up means you need to change the caster blocks to make up for the lost angle. This is a bit less viable on vintage stuff as we have far less tuning features than modern buggies with there pil and insert setups.

RogueIV is pretty much spot on.

The kick-up angle on the RC10 is from a time when tracks were generally way more bumpy/blown-out than most current tracks.

So now its possible to reduce it a bit, so the suspension is more predictable/precise. Plus the added bonus is, if combined with the raised rear suspension mounts it lowers the total CG of the car. Not by a lot, but pretty much "free performance" is never a bad thing

(*you will need to adjust your bumpsteer accordingly)