*** Krazed Builds KR4 Rear MOA Axle ***

[Robbob]

Looking for a Lighter and Smaller rear axle for your Bully2?

We are excited to finally release our KR4 Rear Axle designed around the RC4WD Bully2 internals.

What is it?

CNC Machined Delrin center case
12mm Carbon Fiber Tubes
Carbon Fiber Side Enclosure
4mm Carbon Fiber Motor Plate
Matching Lower Link Triangulation
15* Kick Up For Better Clearance
Optimized Upper Link Geometry

What do I need?

All the stock gears from your existing Bully2 axle
Stock Bully2 axle shafts
All the stock bearings from your existing Bully2


Do I need to custom make anything?

Yes - the only thing you will need to make new is upper links.
With our optimized upper geometry you will need longer links.
Or just simply putting longer rod ends on your existing links.


What if I dont have a Bully2 axle?

Thats no problem at all! You can buy the parts separately from RC4wd and put them together that way.

Stock Bully 2 Gears
Stock Bully2 Rear Axle Shafts
The necessary bearings for the axle (10 total)
KR4 Axle

Where do I get one of these?

KR4 Rear Axle

KR4 Axle - 180.00$ plus shipping - International Orders Are Welcome

Its that simple!

[Robbob]

Heres a little write up from our store about what we put into these.

First we wanted to give existing Bully2 owners the biggest gain. We designed everything around stock internal parts. You use the stock gears, the stock axle shafts and the stock bearings. Theres no buying anything extra or having to order different parts to make this work. We also took out that smaller bearing drivers tend to worry more about and replaced it with one of the normal bearings. Designing this way also leaves it open for drivers to just buy Bully2 gears, axle stubs and bearings to complete the axle and save money.

Second we wanted to centralize everything as much as possible. Working the gears together in the tightest configuration we were able to design the case around them. This let us bring the motor back closer to the axle. It also made it possible for us to shift the motor in/over towards the center allowing for a better weight balance left to right.

The third item on our list of wants was optimized geometry and tuning ability. Sitting down with our notes, calculator, and dial calipers we looked at link and shock locations and what we have always felt was ideal. We understand there is no real right way to set up a truck. There tends to be many variables in chassis designs and terrains that effect the trucks. We do believe our theories and tuning works in those instances.

The center gear housing and lower link holders all run on the same angular plane keeping the motor up for clearance. Doing this allows us to lock the lower links inplace and out of the way. We also never liked how rolling an axle up caused a change in link setups and raised our motor above axle center too far.

The upper links follow vertically true with the axle tube centers. Changes to the upper link at the axle create minor effects to squat/anti and leave more to the chassis side for major changes in squat/anti effects. We have found the axle to be our middle ground where the chassis is more of the wider range of change in tuning. We were able to better our feeling of getting 'just a little more' of a change in any direction.

We also worked in triangulation tuning on our upper link. Allowing for adjustments in this area we found drivers can better dial in their articulation and balance. Single point mounting like other axles tend to be a weak spot for tuning and strength so we did away with it. With 4mm's of adjustment in each direction from center helping you to stop the 'peeing dog' effect of tire lift.

One last thing we looked after was shock mounting. We didnt need a bunch of holes so drivers could over tune and we didnt want holes that changed things like chassis heights or axle roll. We wanted something that we could alter a shock angle and vitrually notice nothing else being effected. We found it and have believed in this tuning for quite some time, when you make one adjustment it shouldnt effect others.

So after we covered our notes and accomplished our major goals we looked at weight loss. This was the easy part due to the materials we knew we would be using, Delrin and Carbon Fiber.

[Robbob]

Helpful building info:

What gears do I need?

All the stock gears except that tiny little idler and the small bearings that tend to fail.

First add locker bearing and two bearings to the case and motor plate.
Add bearings to the carbon fiber side
Arrange the gears on the carbon fiber side enclosure as show - add in the locker gear - and slide into the case.
Slide the cluster into the case.
Attach side with included screws, spacers and bearing retainer




Can I use aftermarket Ti axles?

Yes! Nothing special about them, you just need normal stock length Ti axles from any of our great vendors on here.


What screws does it use?

We chose to use 3mm for the axle tube mounts and upper link. For the strength of them this was needed.
In all the other areas we chose 4-40 for the weight savings.


What if I dont have a Bully2 axle, where do I get the parts?

You will need the following:

Bully2 Gear set - Bully 2 Gear Set
Bully2 Stock axle shafts - Bully 2 Competition Straight Axle Shafts

Bearings:
You can use the RC4wd bearing kit and have extras - RC4WD Bearing Upgrade kit for Bully II Competition Axles

Or buy them individually from your favorite supplier:
Locker bearings (2 total) 10x15x4mm
Gear and axle bearings (8 total) 5x10x4mm

Recommended suppliers:
FastEddyBearings Ball bearings & RC Bearing kits
Avid RC Bearings and Accessories for radio controlled vehicles, your one stop shop for RC bearings, RC wheels, RC accessories, RC springs, and much more.

KR4 Axle Case
KR4 Rear Axle

[mammoth]

Are these already out of stock? Or they haven't been released yet?
Website says out of stock?

[travis c.]

They are selling like hotcakes!

[Jslick]

I got the last one in the store today. More are on the way.

[Robbob]

Im doing batches of 9 .... thats how many I get out of a sheet of Delrin.

The first batch sold fast

I already have more delrin coming (praying its here soon) so will have inventory up in a few days.

Incredible Thank you to everyone!

[84yoda]

I got mine ordered!! Woo hoo.

More on the way, keep watching his site.

[travis c.]

USPS tracking says mine should be here tomorrow, WOOHOO!

[84yoda]

Originally Posted by travis c.

USPS tracking says mine should be here tomorrow, WOOHOO!

Me too!

Now just waiting for my Ti shafts from creeperbob to get shipped.

[84yoda]

Got mine today, it is CRAZY how light just the housing is. Its a work of art. Awesome job and thanks again!

Now onto the front housing...

[Almighty Malach]

That epoxy will never hold!

Very impressive thought process and execution

[travis c.]

Beautiful........................., just beautiful, it shows that you take great pride in your products. Looking forward to the next crafty idea you have brewing in your head!
Thank you very much Mr. Robbob!

[Robbob]

Originally Posted by Almighty Malach

That epoxy will never hold!

Very impressive thought process and execution

Set screws for the win

Thanks Casey - been beating on mine through all 5 revisions, now I just have to figure out a front eventually lol.

Originally Posted by travis c.

Beautiful........................., just beautiful, it shows that you take great pride in your products. Looking forward to the next crafty idea you have brewing in your head!
Thank you very much Mr. Robbob!

Thanks Travis

[chevotafun]

How long till you have some in stock again?

[travis c.]

Easiest axle to assemble ever, tolerances are perfect, excellent work!

[Robbob]

Originally Posted by chevotafun

How long till you have some in stock again?

Tracking on the delrin for the case says i should have it friday, im gunning for the following friday to have them back in stock.

Originally Posted by travis c.

Easiest axle to assemble ever, tolerances are perfect, excellent work!

Thank you sir

[travis c.]

Since receiving this axle I have been debating weather or not to take the flapdisk to the housing. I have done it with every other rear axle I have owned but I don't know if I can do it to this one.

[ElChupacabra]

No Pre-orders for the next run? Can't really sit at a computer all day Friday.

[Robbob]

Originally Posted by travis c.

Since receiving this axle I have been debating weather or not to take the flapdisk to the housing. I have done it with every other rear axle I have owned but I don't know if I can do it to this one.

Wait ..... do it

Originally Posted by ElChupacabra

No Pre-orders for the next run? Can't really sit at a computer all day Friday.

I cant ..... my biggest fear doing that stuff is something gos wrong with the machine, material takes to long to arrive or just some freak thing holds them up. Im sitting here with peoples money and expectations that I cant deliver on. Ive seen to many vendors burn good people that way.