It’s an unknown as to whether kooka cranks break, because they’ve only ever been on normal square taper hubs previously, which seem to be less strong than a lot of cranks and definately are less strong than the kookas.
I’d be really worried about loosening, because the cranks aren’t user put-on-able. Although presumably that’s one of the things that muniac’s modifications are supposed to avoid.
Interestingly, according to unicycle.co.nz, the shipping weight of an onza crankset is 2.0kg or 4.4lb, which probably means the crankset weighs 3 or 4 lbs, compared to 2.6lbs for the drastic one. Which means you’re saving about 1.4lbs, whilst losing entirely all maintenance possibility.
The other thing to worry about if you ride much is bearings. Even with proper sealed bearings, they do die. Given you’d still need to send the crankset off and rebuild the wheel you’d be talking nearly $100 for a bearing change.
The other thing to think about is that if you decided you wanted fast cross country length cranks (like the KH 145 or the onza 140s) as well as hard muni cranks for this lightweight unicycle, you’ve got all the hassle again and you can’t swap them around at all.
It’s not just the modifications that make the joint more reliable, but the fact that the cranks are put on with a press by someone with experience. That’s the whole idea. According to Scott square taper cranks in a high-stress application should not be installed with a hammer by someone who lacks the knowledge to do it right. Makes sense to me.
Scott has been riding square tapers for about 4 years now as well as a bunch of agressive riders our riding group. Also, Scott has been riding the Lightfoot hub with Kookas for the past year. I’ve never seen a loosening problem or a breakage problem. I’m not worried about this. I was mostly just curious as to whether anyone had actually broken a Kooka.
I believe you may be talking about the whole crankset which I assume means hub and cranks. Scott’s hub alone is 0.86 pounds. I think you need to compare hub to hub, cranks to cranks etc. I don’t know yet what the Kookas weigh but I’ll be finding out.
I’m planning to assemble the lightest possible, strong urban trials 24" Uni. I expect it will weigh around 12 lbs, possibly slightly under 12 lbs. If it doesn’t, I’ll be thinking twice about spending the money. I’m in the process of getting specific weights of all the components and taking the guesswork out. So I’m basically spending over a grand on Scott’s “package” (hub/frame/seatpost peripherals and support) to save 3-4 lbs. I’m not losing maintenance possibility at all. The way I see it I’m gaining a second, kick ass urban trials Uni. If something breaks, I’ll deal with it and I’ll ride my Vortex while the Wilder is getting fixed.
Not worried. Sh**t happens to equipment. If my bearings go, I’ll be prepared to deal with it. My bearings on my current Muni are 3 years old, have been exposed to lots of water and abuse. If I get a bum set on my next Muni, that’s life, but unlikely.
Thanks for all the feedback. It’s all definitely good food for thought. I’m not interested in swapping cranks. I’ve been riding 170s for 3 years now and no interest in anything else.
Merrill: First, you were correct in your analasys of my post. I should’ve mentioned that that was just my own opinion. I don’t have more than about $700 to blow on unicycling over the course of about a year, so I can’t afford breakages. Profile and splined work well for me, and I don’t mind the weight. According to the DH shop’s scale, my Onza trials uni weighs about 12lbs, which is almost nil. When going from my 11lb first uni (united), to tha Muni, I barely noticed a difference. Then, going from my 14lb muni (nonsplined, I’ll get to it later), to my Onza, everything got easier. Right out of the box I noticed a change. I could hop with more precision, and everything just got easier. (Then I went back to my muni and noticed how I’d bent the taper on my suzue hub:( ). So, for me, my way of getting a real deal on a unicycle is to get a job at a b*ke shop and buy a set of profiles for wholesale, which is about $200. My muni I breaking, and it will need fixing sometime.If you want a truly light muni, more power to ya. In my case, I’d rather spend a bit less and get a heavier muni with a better setup, than a light, crappy one. Scott’s hub isn’t low quality, just for me it isn’t cost effective.
One thing you might want to consider is if you want to build a 24" trials uni. You could save weight by making a 19" wheel, and getting Scott to remachine your Kookas to 140mm.
As for splined vs. square taper, I think the best would be splined taper, but that is insanely difficult to machine. My experience is that splined is the only way to go if you’re an aggressive rider, with the only exception seeming to be the lightfoot hub with some kookas. I know that something on my muni is very bent, and I’m 99% sre it insn’t the Monty cranks.
I like to be able to quickly cruise around the city to various spots, and a 20" is too slow, and not much fun to when getting from A to B. I like the idea of a having a spare, light, urban 24. By using a 24" for urban trials, my technique on a 24 will continue to get a workout.
Both my Kookas and Peter Bier’s Kookas have a habit of coming loose on our Suzue hubs. As a result I always ride with a crank/pedal tool in my camelback. I have stopped using my 170mm Kookas in favour of 152mm Vertigo aluminium cranks [http://www.unicycle.co.nz/shop/shopdisplayproduct.asp?catalogid=51] which are in my opinion a much better size for a 24" MUni.
Well installed cranks? Well the first time I put em on I had to use stone age crank tools…
However, these aluminium cranks also work their way loose. I do not think my experience of aluminium cranks gradually creeping up the taper is an isolated case - its just two metals of different hardness being forced together - the aluminium is deformed by the steel. I’ve pointed out this crank problem to various cyclists and bike mechanics and they’ve seen it before, albeit on bicycles. So, no, I don’t feel that the NZ experience of Kookas is an isolated case.
Having said all this, my Kookas are the best square taper 170s I’ve ever owned and my Vertigos are likewise the best 152s I’ve ever owned.
Yes, Suzue hubs tend to snap before Kookas break. Peter Bier snapped his Suzue hub by going off an inocuous looking 2-footer. Jeff Prosser snapped off his hub clean at the UNICON trials comp - I think he was jumping off the roof of the car. His Kookas were fine.
this thresd has been fascinating. my question then is - what is the proper way to install square tapers? kooka’s or otherwise? when you don’t have access to a 20 ton press. and how much of a difference does the press make?
I used to pound away on cranks with a rubber mallet to mount them. Then I realised that the mallet treatment is quite unnecessary 99% of the time. Just push the crank on the taper as far as you can by hand, then honk on that crank nut. A crank/pedal tool makes this nut easier than yr crank puller + wrench.
Another way is to heat your cranks up in the oven for an hour, then slide them on. The hole should have expanded, allowing the crank to be mounted further up the taper. You might need oven mitts for this one. I’ve been told about this by a bike builder, but not tried it myself.
I agree with Tony. I’ve seen hubs damaged from the mallet approach. I’d replace “honk on that crank nut” with “use a torque wrench to torque the nut on to 40 ft-lbs”. It’s worth the extra care when you see the cost of replacing/repairing a hub and doing another wheel build.
I don’t know if the 20-ton press approach is better, especially for all cranks; however it is pretty tempting after Joe Merrill’s comments. For most people and most riding, however, the torque wrench approach is plenty and you still know that you’re doing a consistent, precision job.
For the press with appropriate attachments (and calibrating gauges?) you are talking several hundred dollars at least. Not all will fit even a 24" wheel, I’m told. The torque wrench approach is eminently portable and costs $90 for a nice one at Sears Roebuck.
How well do those Vertigo cranks fit on the Suzue hub? Some aluminum cranks fit so far on the Suzue hub that you cannot put a dust cap on. The threaded part of the Suzue hub sticks out beyond the crank and makes it difficult to put a dust cap on.
I’ve been using a heavy duty bar clamp made by Bessey. Much cheaper than a 20 ton press. The bar clamp does a good job of getting the crank seated on the hub.
I don’t like the idea of using the retaining nut and Suzue hub threads to draw the crank onto the hub. The retaining nut is serrated which digs into the crank (especially aluminum cranks). The Suzue hub threads are not that strong and the retaining nut only engages a handful of threads. That’s not ideal. I feel much better getting the crank first seated using a bar clamp or a press and then tightening the nut.
With the Unicycle.com CrMo hub and other hubs with internal threads you could probably use the retaining bolt to squeeze the cranks on to the hub. There are more threads engaging so you’re not likely to strip out the threads. The bottom of the retaining bolt is not serrated so it shouldn’t dig in to aluminum cranks.
For hubs with the outie threads and a retaining nut I like the following procedure:
Grease the tapers
Use a bar clamp to press the cranks on
Put red Loctite on the retaining nut threads
Tighten the retaining nut
For hubs with internal threads you might be able to skip the bar clamp. I don’t have a unicycle with the unicycle.com CrMo hub so I have not been able to experiment with crank installation using that hub.
On Mon, 9 Feb 2004 18:43:48 -0600, TonyMelton wrote:
>Another way is to heat your cranks up in the oven for an hour, then
>slide them on. The hole should have expanded, allowing the crank to be
>mounted further up the taper. You might need oven mitts for this one.
>I’ve been told about this by a bike builder, but not tried it myself.
At what temperature would you start interfering with the crank’s heat
treatment? (I guess more than a household oven can muster.)
Klaas Bil - Newsgroup Addict
I have a feeling you might need two points of contact with the ground for such a thing to work? Or at least training wheels on the front and rear. - John Foss commenting on a picture of a one-wheeled vehicle he saw on RSU.
> At what temperature would you start interfering with the crank’s heat
> treatment? (I guess more than a household oven can muster.)
Your oven will do just fine. We used toaster ovens to heat treat
steel in college and aluminum alloy requires lower temperatures.
Figure on half the melting point (what, around 500K, 450F?). But
equally important is the time the metal remains hot - the shorter the
exposure the less you’ll mess with the tempering.
So, go ahead and heat the crank arm to 350F, but only for a short
time. My metalurgist says cooling it with water after tightening
might help and reminds you to cool the hub to shrink it as well.
Also, pressing or clamping the arms is much preferred over pounding on
them. You never get a completely accurate hit when using a mallet and
are just as likely to deform the crank as press it on tighter. I just
saw this when I tried hammering the cranks on my new Unicycle.com hub.
One week later both cranks were loose.
