I had an idea yesterday from PDC’s tri drilled kookas. Would it be possible to get a set of koxx splined cranks(140mm) and also have them drilled for 125 or 127 so that you could switch from having a trials setup to a street setup in about a minute? would this work seeing as the cranks are solid aluminum, or would it weakon the cranks considerably?
I don’t really think it would work on splined cranks. You need that pinch bolt to keep everything snug. If you had another hole - well, it would be more like a star kindof hole - bored into the crank, it would lack the pinch bolt.
Say you overcame that issue, and you have a way to keep everything tight. I’d imagine that after a couple of drops, the cranks would start to bend.
It would be really hard to do that on koxx cranks because of their design. It has this metal, splined pedal insert that crimps down into the alu crank so you would have to dupicate that whole thing for another hole. It would be hard.
two pedel holes would bash your ankle up pretty bad in the shorter crank setting (I think) because the q factor would still go outwards into your ankle. plus after a switching X amount of times it would ware out
I think you could drill and tap the Koxx cranks. The Kookas are aluminum and are quite hard enough to accept pedals without inserts. I guess finding out what type of aluminum the Koxx ones are made of.
In summary: You want to make sure your Koxx is hard enough before you start drilling.
Sorry i didn’t think of that till i finished typing the first part and couldn’t help myself.
You could weld a tubular insert into the KH cranks and thread it to accept a pedal, but this would be some serious machine work and it would taker a skilled machinist to make a good job of it. Also the cranks are I believe CrMo not steel so more difficult to weld, harder on cutting tools etc. which all adds up to more cost. It would probably be better just to get different cranks, with their self extracting system KH cranks are as easy to remove as pedals, although would take longer unless you had 2 sets of pedals, becaue you’d have to swap them over aswell. That fact that KH cranks stick out (Im not going anywhere near the whole Q-factor debate) means that the protruding ends might hit your foot/ankle when it is between the 9 and 3 positions
People seem to have had a lot of problems with the koxx pedal threads, I certainly wouldn’t thread the aluminium directly, a pressed steel insert would be needed. Drilling a hole would weaken the cranks, but as it is near the pedal end the moment is less so this effect would be diminished so it might be workable. Also I understand people genreally bust cranks more doing street than trials, and for street the pedal will be in the nearer hole, decreasing the moment so done properly this setup would actually be stronger than your current cranks. However with the pedal in the outer hole there would be a significant weakening, just a case of how much force you put on them doing trials. Also you’re probably going to need some milling work done to get a flat for the pedal nut to butt up to get a solid fit.
Having said all this, there’s only one way to find out, just make sure you used a skilled machinist who understands the aim of the project and is familiar with the materials used, for goodness sake don’t try it yourself at home with a power drill! Good luck.