spidercrank

I needed to buy new cranks which is fairly daunting because cranks are fairly specific things. To give you a taster this was the title of my mental wanted ad on retrobike: 175mm 110BCD Shimano XTR FC-M952 JIS taper, crank arms only. Obviously this was an impossible ask as the FC-M952 crank only came with Shimanos proprietry (take a shot) octolink spline, but you already knew that. 

A different pair of cranks then, and after multiple messages back and forth to an ebay seller to make sure I wasn't paying for something I couldn't use, and being confidently reassured that I was in fact getting what I needed...

haha, every cloud has an alminum lining!

So i needed a new blue bit, and on these RS7? middlburn cranks it's a seperate piece held onto the crank arm with a combination of proprietry (shot) spline and proprietry (shot) lockring. They're also about £70 new, and impossible to find used. Talking to Odin my predicament came up and he suggested we mill something on his 5 axis (3 functioning) cnc machine. Although for Odin the problem is a secondary concern to the solution, which is always, mill something on the cnc machine. As far as I know, he's never been wrong.

Doing the bare minimum, my specialty!

Autodesk just released Generative software as part of a Fusion360's subscription. This basically takes force input on a part, in this case, rotational force on the chainring bolt holes and spline interface, and then uses a machine learning algorithim to optimise material placement accounting for those force inputs. The pictures show this iterative process as it goes from viable to tenuous to laughable. This had me pretty worried  

that we'd underestimated the load and where it would be applied as some of the outcomes seemed to be held together by faith alone, but this is a happy story with a happy ending so no worries.

I overnighted some 6061 aluminum stock and watched Brodin setting up the tool paths for his machine. This is some nerd shit and tbh it's pretty boring to watch and I can't imagine it's that fun to do either so thanks again man. 

These tool paths are translated into a language the machine can understand, essentially loads of XYZ coordinates, called gcode and then it's the future and the machine does all the work. Except it's not and you're Odin and you're constantly worried the machine will decide to start milling your part out of itself instead of your stock. But it still is a little bit the future as the part gradually emerges from the seminal coolant. 

all the tool paths for the front side

 

HAAS Super Mini Mill if you're in the market

 

Thanks for watching!

I do all of these posts on my computer and i've realised that the formatting is a bit funky on phones which I imagine is what most people will use to read these so i'll work on that in future.