Review: cranks and thanks

Ages ago, Roger at Unicycle.uk.com advertised a new product: aluminium alloy cranks cut down from left hand bicycle cranks. They were to be available in a number of sizes, down to 89mm. he also introduced cheap steel 89mm cranks around the same time.

I ordered a pair of the aluminium alloy cranks. In a brain storm, I put the left pedal in the left crank, right pedal in the right crank, and then put the cranks on the wrong side of the uni. D’oh!

Within a couple of hundred yards, the left pedal worked loose and damaged the thread. Totally my fault, although a little surprising that the damage should be so quick.

Roger had asked me for an opinion on the cranks. I e-mailed him glumly to say that I had ‘totalled’ one of them in the first five minutes. he offered to fit a helicoil (thread insert) and I returned the crank to him. It took him some time to source a left hand Helicoil, but today I got the crank back repaired - and Roger refused payment for the repair. Service second to none. Thanks, Roger.

So the product: Roger has taken good quality aluminium alloy cranks and cut them down to various lengths. 89, 102 and 110 are available, as well as the longer sizes some of you prefer.

The cranks are pleasingly solid looking, nicely sculpted, and have a polished surface. No doubt about it, they look better than the basic steel ones.

The cranks are cut in one direction only, so that they have an ‘arched’ end rather than a ‘domed’ end, if you see what I mean. This isn’t unsightly as this part is partly ubscured by the pedal much of the time anyway. Finishing a 3 dimensional curve evenly, neatly and consistently would be disproportionately difficult and expensive.

They look like a ‘workshop made’ custom part rather than a factory made part, which I see as a styling plus - it makes the uni look more like an enthusiast’s machine than ‘just a toy’. This is subjective, of course.

The cranks appear to have a slightly higher Q factor than the cheap steel ones. That is, they angle out from the axle a little bit further (only a few mm) which might reduce the chance of your ankles or shoes scuffing on the cranks if you position your feet badly.

Fitted correctly, I have no reason to expect the softer aluminium threads to be a problem. I expect many happy miles of use out of them.

Weight? I haven’t the facilities to weigh them accurately. In general, I know that aluminium alloy is less dense than steel, so that a given shape is lighter in the aluminium alloy than the steel. However, steel is stronger for any given weight, which means that the aluminium alloy ones have to be thicker. So you get more of the light weight stuff, cancelling some if not all of the weight advantage.

Are they worth 3 - 4 times the price of the cheap steel ones? Only you can decide. They only do the same job. They look better. I’m still not sure whether custom sizes are available, as Roger hasn’t given me a clear answer. I might be looking for some 75s one day soon, Roger…

So, a recommended product, smart and effective, and the price is a fair reflection of the cost of production. Thanks again to Roger for the excellent service.

Mke

I agree. Two questions, how do you stop with 89mm cranks, and what size wheel are you putting them on?

Thanks,
Andrew

Re: Review: cranks and thanks

Cor blimey… if it were anyone else I’d think they were joking…

Phil

89 mm = 3.5 inches

I have them on my 24.
3.5 into 24 = 14.6

Compare that to 110 mm (4.3 inch) cranks on a 28 = 15.4
Compare to 125 mm (4.9 inch) cranks on a Coker (36) = 13.6

OK so let’s not get deeply into ‘gear ratios’, but you have more torque and less weight with the 89s on a 24 than you would with 125s on a Coker.

In practice, the 24 with 89s is reasonably easy to idle, but requires a much slower idling cadence. It’s almost like riding forwards and backwards a half turn, rather than doing a pendulum swing. Mounting is easy with care, but you have to get the pedal position just right - too high and the uni scoots away from you. Stopping requires planning, and from full speed (around 15mph for me) it might take 2 or 3 complete wheel revolutions before coming to a controlled stop.

It’s challenging on horizontal but non-smooth surfaces, climbs hills like a jellyfish, and descends hills in an amusingly alarming fashion. It’s all good fun, and fine practice for riding more sensible wheel/rank combinations. 102mm cranks on a 24 are loads more practical though.

But don’t forget this started as a product review, and the cut down cranks are available in a range of larger sizes.