drilling multi-hole cranks for easy pedal length options

drill and tap

I’ve begun thinking of having my 150s drilled and tapped for 125 or 110s. I bet there is a machine shop in the area that could do it.

Tapping is not easy and requires specific tools for pedals (9/16"-20TPI), left and right are different … I got mine from WWW.RDGTOOLS.CO.UK (reference 1214 for right side, reference 1789 for left side)

Local bike shop

I talked to today while picking up some tire levers said, “No way, wouldn’t do it.” He went it to how the cranks are reinforced where the holes are drilled and that they’re not made to have an additional set of holes. :thinking: :thinking:

While it is true that many cranks aren’t suitable for extra holes, it is not without exception. There are at least a couple of machine shops that custom drill and cut cranks to fit smaller riders on bikes. I had a set of cranks that were cut down to 140mm that i used on my Nightrider.

Spirit crank forging tool is unique for all Spirit lengths, this means you can drill a 127/150 Spirit and add a hole at 110 as 110 Spirit is existing

Kris knows about my Spirit custom with 110/127/150 positions, he said this is great but market is not enought for him to add an additionnal variant

Venture 2

I just have the Venture 2 cranks that came with my 24 Nimbus. Will have to research whether these are doable for extra holes.

interesting thread w/ pics

I had idea at least 7 years ago for “ratcheting” cranks, or something similar that could change length on the fly without tools or removing the pedals or cranks. I’ve seen many variations suggested since then but so far I haven’t seen anything commercially available for unicycles. The multi-hole cranks do the trick for me and takes all of maybe 60 seconds to switch pedal holes. But it would be very cool to have something like this:


not interesting because cotterless …

Still cool…

… I like the pics. :sunglasses: :sunglasses:

Found a local machine shop (school) that will add a new set of holes to my Venture 2 - 150s — at no charge. I guess they use it as a learning tool…he promises a quality job.

When making multi hole cranks I would try to make the space between the holes as wide enough so that you can use quick release pedals on it. For the QRD II System you’ll need about 18mm of material between the holes.

In 2013 I wrote with Kris Holm about this. He had samples of both systems (QRD and QRD II) at this time and was testing them. The problem was, that on the existing dual hole cranks there is not enugh space between the holes to install two QRD adapters at the same time. He also sent me 2 photos, but I don’t know if I’m allowed to upload them here.
But if you drill new holes in the cranks, than I would choose lengths which allow to mount a QRD II adapter in every hole.

Hey Eric,

Thanks for the info and that looks like a reasonably priced option of something I had been thinking about. Looks like the pedals can be had for around €60 and an extra set of adaptors for less than €20.

So I have unfortunately been busy with way too many non-unicycling things (moving).

But I am probably going to drill the Spirits instead of the Moments. I’m not sure if 2 holes are possible and/or worth it.

So is there something special in the crank that only allows drilling at 110?
But then how does this translate to the 150/165 lengths?
Spirit Duals come in 150/127, 165/137, 137/117 and 127/110.
Does this mean there are two forging patterns?

  1. 165/137/117
  2. 150/127/100

Meaning that then I can only drill at 117 on the 165/137/117? What is the problem if you drill somewhere else, like at 118 and 100? Are there hollow spots?

So drilling options:
one hole at estimated “forging spot” per bouin-bouin:
165/137/117 (20/20)
165/137/110 (20/27)
or maybe still 2 extra holes:
165/137/118/100 (20/19/18)

(all these would work with QRD as at least 18mm distance)

I think something between 110 and 118 would be my ideal commuter crank length, as I’m getting really good with the 127s and I have great control and can definitely go shorter (today I had my fastest time of 52 minutes for 16km with 127s). Actually, I’m thinking 110s sound best, but it’s so hard to know without trying. I think I’ll put the 100s on again end of the week and try them for a few days.

The space between the holes is too narrow to install a QRD adapter in each hole at the same time when you use original two hole spirits.

OK, yeah, you said that but I missed it. Thanks for the clarification.

Although I don’t think that’s so bad, as with triple of quadruple holes, you can definitely do QRDs at 2 non-adjacent holes. In particular, I use 165 for Muni and something between 100-127 for my commute.