Lean Mean Stock Machine

[MotoObscura]

In the words of Colin Chapman, "Adding power makes you faster on straights, reducing weight makes you faster everywhere."

So the purpose of this build is to turn my second hand b4.2 from eBay into a killer stock racer by minimizing rotating and unsprung mass and by experimenting with a few oddball ideas I have.

Here is the starting point:

First issue to address are those ridiculous arms. There is a set of stock, non carbon arms on the way.

And this front end took a lot of big hits.
This buggy has had a tough life, so these first few posts will be a restoration of sorts.

[RC104ever]

Are those Traxxas wheels and tires on the back end?

[MotoObscura]

Why yes, yes they are. Did the b4.2 rs come with 12mm hex's in the back? If so, they're gone. All that is left are the pins to fit the traxxas wheels. Well I should say one pin. The right side wheel was totally stripped out and the pin is gone

[MotoObscura]

Well, I got most of that garbage scraped and ground off of the chassis. It appears to be a redneck composite of saw dust and ca...

[Coelacanth]

I'm not sure what's ridiculous about those arms...as you said, the front end took a lot of hits. The arms look to have survived the abuse.

[MotoObscura]

The arms don't look damaged at all. Or even scratched for that matter. I wouldn't be surprised if the arms were added after the horrific crash that broke the front chassis brace screws and (possibly) broke the stock arms.

[Coelacanth]

Maybe that's why he chose them...

I just wondered why you thought they were ridiculous? Obviously they're not stock, but aluminum is definitely stronger than stock. Heavier too, but I guess it depends what you're going for. Light weight vs. durability.

[MotoObscura]

This one is gonna be light weight. Besides, I'm not a fan of aluminum arms anyway. I prefer rpm if I need a strong part. It springs back, aluminum just bends.

Anyway, a few parts came in!

[kaiser]

i've never had and issue with the carbon arms. cabon everything except the chassis.

[Bottom Feeder]

Jeez, that thing is rough! Kudos for rescuing it!

I read something in a bike magazine years ago that sorta fits: "It's not that you really want it, it's that you don't want the current owner to have it any more."

[MotoObscura]

I've heard the carbon rear arms are fine, but I've heard that the fronts are quite fragile, and I'm not the best driver in the world so I'd probably go through quite a few.

[MotoObscura]

The mip top shaft weighs 4 grams. For now at least.
I know I want my spur gear to be the weakest link in the drivetrain, but still, if it is this thick:

My internal gears don't need to be this thick:

So I threw it on the lathe...

And here is the finished product

It won't even register on my scale anymore

[Sixtysixdeuce]

Hmmmm.......That's not a place I'd choose to shave .2 grams, but let us know how it works out!

[GoMachV]

I got a stealth from eBay not long ago and after opening it i found a cut down top shaft and the diff gear is just as thin. They left the idler alone. Pretty cool old school mods. Kind of a lost art now with the uber powerful batteries and motors

[MotoObscura]

Well I'm bringing it back!

Hmmmm.......That's not a place I'd choose to shave .2 grams, but let us know how it works out!

Honestly I would be very surprised if I got 2 grams from the entire gear train. I guess we will find out once I cut down the idler and differential. I'm keeping the gear diff, though it is probably quite a bit heavier than a ball diff. I'm going to replace the steel shafts inside the differential with something like carbon fiber rod. Perhaps the idler shaft too.

Anyway, what to hack up next? How about the motor plate. There is a lot of unnecessary material used behind the spur gear to prevent dirt from getting into the gears behind the cover. But I usually don't use the gear cover anyway, and that's a lot of thick aluminum way up high.

So I cut it up.

Here is the result, all smoothed up.