[Thylacine]

If you look at the design and it's manufactured to close tolerance, it should equalize. Tightening the clamps forces the spindle forward into the front lobes.

Hey Warwick, on the EE stuff, did they get the rights to Sweet Wings or is it the same guy?

Same guy I think - Craig Edwards. Just swapped a few emails with him regarding the brakes for a customer and found out about the cranks through the fairwheel website.

I'm completely into crank pron. In fact, I'm still trying to find a replacement for the Syncros Revos I destroyed but loved to bits. BMX has far more interesting cranks than the MTB world (See: Odyssey Wombolt, Fly Bikes, Demolition....)

 

[DWF]

Same guy I think - Craig Edwards.

Yep, same guy. Good to know.

 

[scooter916]

I have a weird or maybe even stupid question. What is the "standard" width for MTB Q-Factor, or more importantly the width inside-to-inside. Only asking because recently I tried to install a set of compact road cranks on my single speed and the crank ends didn't clear the chain stays.

 

[Ecyclist]

Machining the square interface will require a 5-axis mill. You may be able to do it on a nice 3 axis if you have some decent CAM software.
The interface is pretty sensitive to tolerance. If you get the taper wrong or sloppy, things won't fit for long.
The ISIS is actually much easier to manufacture, but it requires the purchase of a wicked expensive broach.
Sorry I can't offer much help on how to do it, but you should know that it is hard. I year of 5 axis programming experience and I would consider the square interface difficult. Good luck.

You don't need 5-axis to cut a square interface. You can broach it on Bridgeport with a tilted corner broach and a rotary table.
It will be much harder to broach ISIS drive, but it can be done. You will need to make custom tool based on this specs. http://my-sport.spb.ru/manual_1/ISIS Drive Complete Rev D.pdf
With a custom broach and a rotary table you can cut it on 3-axis CNC mill.
Once you have everything set up this shouldn't take more than 5 minutes.
You can also broach it by using a rotary table and Bridgeport. In that case you will need to tilt a head of a mill or tilt a rotary table by 1 deg.
The second option will take much longer.
Disclaimer: I'm an old fart with over 40 years experience in mechanical engineering.

 

[JackOfDiamonds]

I make cranks. Mine are pinchbolt style with square "spline". This is a long and glorious tradition in BMX cranks like the legendary Primo Powerbite cranks, and easy to make on a manual mill. I never understood why pinchbolt cranks, square or otherwise, aren't more popular on "regular" bikes... it's just like a threadless stem, you preload the bearings and tighten it up.... easy to add spacers here and there for chainline...

To make a square taper with manual machines your best bet would be buy a tapered end mill, but I never tried it.

 

[Joe Nation]

I make cranks

I can't tell if those pedal threads are massive or the arms are tiny! Or is it just my wonky eyes? Nice work though.

IIRC, Powerbites had the pinch bolt slot cut on a corner, not on a flat - any opinion or evidence on whether one is better over the other? I would think having it on the corner would be better as you are clamping all 4 sides of the square, but then again the clamping force will work to try and split the arm across the perpendicular axis of the square.

And FWIW, Hollowtech 2 cranks use a pinch bolt so there are literally bajillions of them out there!

 

[JackOfDiamonds]

I agree with you and I usually have them clamp on a corner. I have done both and it seems to work fine either way. Actually, the only creaking problems I've had have been the corner ones, go figure. I think those ones were 110mm long. Total crankset weight about 275g...with bearings. Heres a corner one before final machining.

 

[marco529]

if you're building cranks in 4130, you can buy the bits from Solid Bikes

http://solidbikes.bigcartel.com/

I found out that tidbit by checking out Chapman Bikes' instagram.