I’ve been thinking recently about the idea of multiholed cranks. They’re fairly expensive to get made as a one-off but I’m wondering if they could be done as a batch to reduce the unit cost. The cost estimates I’ve heard are around 40 quid to do one pair - anybody heard of anything better?
I was tentatively wondering if there would be any interest in clubbing together to get a batch of double holed cranks made. Prowheel alloy cranks look to me like they might be a good base to start from… 150/125mm or 170/150 seem like they might be good spacings to think about.
My ideal wish would be that UDC UK would take this up and get a batch machined for sale. Now that ISIS users can get the KH double holed cranks it seems a shame for the large cotterless market not to have this available too. If not, maybe we UK riders could just work out something as a group.
I think it’s a good idea. Stay away from the Prowheels, I was on a ride a couple weeks ago with someone who broke one at the beginning of the ride. He said it was the second Prowheel crank he’s broken.
Do the prowheels have thread inserts or do they just thread in to the metal? Assuming there’s a flat area to do it on adding a thread hole would only require a pillar drill and a tap, I would certianly be up for trying this over the summer (even tho I don’t ride cotterless cranks).
The idea of multi-hole cranks has been discussed many times in this forum. If you search, you will find links to tandem websites and things like that, and some standard items are available.
If you try to get some made, they must be the sort that are parallel to the plane of the wheel (rather than angled out for extra Q factor) or when you have the pedals in the “short” holes, the ends of the cranks may knock your ankle bones.
I’m currently running ProWheels on my 36er and find them OK. I believe Rob Northcott also uses these, so I wondered if he might be interested.
They just thread into the alloy; possibly not the strongest way of doing things, but it works fine for me. Prowheels have a fair amount of Q, but in response to mike’s comment the outmost section (where the extra hole would go) flattens out a bit so that the pedals shouldn’t bang your ankles.
My main problem is that I don’t have free access to the pillar-drill and tap (nor, arguably, the experience required to make a good job of it although I could probably muddle through). My go-to guy for Cambridge’s engineering department has moved onto other things, sadly.
If you were interested in trying this technique out, maybe you’d consider doing some for me for a suitable fee?
Would be interesting to have shot at it, I have only a very rudimentary pillar drill at home and would need to but the tap and probably a suitable drill bit. I might well be able to use the staff-student workshop over the summer to do the work to a much higher quality, and for free. Could knock up a jig with a sqaure taper the crank installs on to to ensure the axle and pedal holes are parallel.
just looking at the prowheels, they have a recess in the back of them, would have to be close enough to the end to avoid this.
I don’t have a tap, but if someone is up for getting me the right size tap and sending/telling me which crank to get and pay for it. I would do it for ya
I’ve not measured them, but I reckon there’s about enough space on the 150s to also fit a 125mm hole in just before the recessed part starts.
Alternatively, if cranks without a recessed back were available I guess three hole cranks would do OK; the cranks pdc modified like this were Kookas, I think.
I don’t really know which would work best; I’m not really a metals expert. Steel would probably have the advantage of failing less suddenly if the weakness introduced by the second hole proves too much. You’d need left and right handed taps to get both pedals threaded correctly.
I think I might rock on down to my LBS and see if they’ve ever tapped cranks before; I’m betting they haven’t but I might be pleasantly surprised.
I have used helicoils, you still need to tap the metal first, but the appropriate tap is included in the kit, but the kits are about £40.
Incidentally, you don’t need a reverse thread tap, you just tap the hole from the other side, if you don’t believe me try screwing a right pedal in to the back of a left crank.
I’m sure that’s not true. The thread is the same whichever side you’re looking from (otherwise nuts would only fit on bolts one way up).
^^Edit… sorry if that was a joke… I was convinced you were being serious :o
As for ProWheel cranks, yes I’ve got a pair on my muni. I’ve had no problems with them, but I’m not a heavy jumper or dropper, just miles and miles of xc. They don’t have any steel thread inserts for the pedals (but then I can’t say I’ve ever seen any cranks with inserts, apart from carbon ones - perhaps they do it on mtb cranks).
FISH? In the KH cranks? Your comment about the taps had me scratching my head for a moment too I get very confused about threads - especially on pedals - at the best of times!
