Although apparently Florian Schlumpf has expressed worries regarding the risk of injury when going at 36" Schlumpf speeds I do rather agree with what somebody said in that thread: the main advantage of it wouldn’t be the ability to go ridiculously fast. Rather it’d just be good for folks (like me) who don’t like riding with really short cranks but would still like to maintain a decent cruising speed (and, as always, to have a low gear for muni stuff).
Presumably the KH Schlumpf hub will be wider than the original hub? And therefore more suitable for 36ers? That’d be cool; and could be combined with the dual length KH cranks to give a ridiculous range of configurations!
Exactly. I do think that my average speed would increase a little bit on flat ground with a geared 36 though. The main goal wouldn’t be to go ridiculously fast, it would be to slightly increase my average speed and lower my cadence at the same time. A coker with 150 cranks in low gear would be able to climb most mountain roads, I usually stick with 125s, but 150s seem like they get the job done a lot easier for longer steeper sections.
Also, as you pointed out…the dual length cranks would allow for even more options. If the ride is going to be rolling hills everywhere you can just screw the pedals into the 125mm spot and keep it in low gear.
Depending on build, the main difference in a 36" guni over a Coker would be the hub change. You would also have to make some modifications to the frame as well which would probably net at least a little more additional weight. Otherwise, the answer to that question depends entirely on the components used; aluminum vs. steel for example.
Yes, a 36" wheel is going to be more stable than a 29". There is probably a physics word for this, but I don’t know what it would be. Inertia? Even assuming a rim and tire of the exact same type (only bigger) the size and weight would still make the larger wheel roll more smoothly. I’ve always found it much easier to ride long distances without dismounts on bigger wheels.
This is theoretically true at any speed, though at very slow speeds the extra weight and size of the bigger wheel makes it harder to control. So I’d say not for very slow speeds, but for anything from “comfortable” speeds on up.
Speaking as a guy with a broken collar bone, I can fully understand Florian Schlumpf’s reason for avoiding high speeds on his unicycles. Anything over your ability to run carries the possibility of danger in even a basic dismount, and the potential for much worse to happen if you wrap up a shoelace or similar (according to my speedo I was going about 15 mph when this happened to me).
FWIW, I was on a ride yesterday with tholub and mscalisi. Tom was on a 29" Schlumpf, and Mike and I were on (non-geared) 36ers. Tom looked quite comfortable on the fast downhills where Mike and I were spinning like crazy to keep up. Based on that, I’m still planning to stick with the 29" wheel for my first geared unicycle once the KH-Schlumpf comes out.
As Mike put it, courage is the limiting factor when it comes to speed on a geared 36. I believe a geared 36 has too much speed on the high end and not enough climb-ability on the low end. Whereas a geared 29er should be a better balance, and it’s more suited for rougher offroad.
Something else I learned yesterday is that the hill climbs around my house are abnormally steep, so perhaps my assessment of “climb-ability” is a bit skewed.
I think that the low gear on a 29er is way too low. the low gear on a geared 36 is perfect. Now when you are talking about high gears…the high gear on a geared 36 is probably too high, and the high gear on a 29 is a little better. My perfect geared 36 would be 1:1 on low gear and 1:1.35-1.4 or something on high gear, so it has a little bigger virtual wheel than the virtual wheel of a schlumpf 29er, but with the stability of a bigger wheel.
A coker with 150s is pretty good at climbing most mountain roads I have been on. A 29er with 125s is definitely great at climbing too though and will be easier to climb steeper sections of road(>10%) since it is so light. It will definitely depend on your riding technique and the frequency of steep sections of road near you, as you stated. It is all preference of the rider. I used to hate climbing with my coker, but now I love it. I usually keep 125s on my coker and I can climb most things with them, including a ride I did with Aspen Mike at the Colorado National Monument.
Ken Looi was using 114mm cranks on his Coker to climb 12% grades (I think some sections were at least that for Arthurs Pass), but he is also insane and a really strong rider.
It all comes down to preference, and for me when I tried out the 29er on low gear I just felt so limited and wanted a higher gear even when climbing (but I couldn’t climb on high gear and feel stable). The low gear really comes into play when you want to do some light off road trails or single track, but I just feel like on the road I would feel limited. A schlumpf 29er definitely outshines a schlumpf 36 for light muni though.
I think one of the sections has a 16% average grade. I got up it all on 150s on the 29er, but I know everyone except Ken and maybe Roger walked up much of it even on 150mm. I’ve at least once ridden up a 10% grade with 110mm cranks on a coker, but I think I might well have been faster up it on a 29er.
I’m on 125s on the Schlumpf 29er at the moment, which is kind of nice, on the flat it’s comfortable to go 10-12mph in low gear, 15-17 in high gear.
Tom was kind enough to swap cycles with me for an extended downhill section. I was amazed how easy it was to go faster than a coker with much less effort.
Anyways, my thoughts are that a 29er has a more usable top gear while a 36er has a more usable low gear. The 29er geared up is fast enough, but an easier gear to push.My travels have proven to me that 99.9% of the roads you’re likely to encounter while touring are climbable on a 36er with 150s or shorter.
I’ll attest that Phlegm is an efficient rider that can certainly climb. (He was ahead of me on most of yesterdays hills). The hills near where he lives are the .1 percent I mentioned above.
Combine steep with gravel or dirt, and a 29er certainly starts to make sense.
I think still think that the 36er is more stable, although the 29er also seemed stable. I personally like that the 36er is higher up. That means if you UPD, you have a tiny smidgen more time to prepare for your fall.
…although a 29er is more useful in that its more transportable, and you can ride more aggressive MUni with it.
I don’t think I’m a strong rider, I just climb well cos I’m light. I recall you leaving us all in the dust when you were ploughing into that headwind on the Otago Rail Trail. A Coker with 125mm or 140mm cranks would have climbed Arthurs Pass a lot more efficiently, but been quite slow on the ride getting there. I couldn’t be bothered changing cranks at the bottom. 114’s are my general road riding cranks.
A larger wheel has a higher inertia - it’s a heavier thing to accelerate in a straight line, without rotating it. Same effect as it being hard to push a car along due to its large inertia. Inertia is just to do with mass - how much stuff is there is the only important factor.
But it also has higher /moment of intertia/. Moment of inertia is different because it has to do with where the mass is distributed as well as how much mass there is. Moment of inertia determines how difficult it is to change the rotation of an object; this is rather similar to the way plain old mass determines how difficult it is to change the motion of an object.
Moment of inertia is higher if the mass is greater. It’s also higher if the mass is distributed further away from the centre of rotation. In a 36er, there’s both more mass outright due to the larger rim and heavy tyre - plus it’s further away from the centre. Given there are two factors at play here, the increased moment of inertia should be quite significantly bigger (as opposed to just “stretching” the mass of a 29er out to a larger diameter, or putting a really heavy tyre on a 29er).
Since we can say “moment of inertia” = “resistance to changes in rotation” it’s clear we should expect a 36er should be quite a bit harder to get rolling, harder to stop rolling, and more comfortable to keep rolling. Which in fact it is
Yet again physics has told us the stuff we already knew. Of course, the important point is the physics help understand whats actually going on and gives a way of measuring and predicting what results design variations might produce.
Sorry for rambling I think the physics of unicycling is quite interesting and have spent a lot of time considering it. The main problem is that there are a squillion different factors at play and it’s hard to estimate how significant each is relative to the others.
Yep. I like the feel of long cranks, but I found they limited my speed. I like to spin on long cranks, but there’s a limit to how fast I can do that within my limited aerobic fitness On a bicycle I tend towards pushing really hard in a high gear - I guess I’d like the ability to cruise at a not-ridiculous speed without having to maintain a wobble-inducing out-of-breath making cadence.
