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Old 2018-02-19, 06:58 AM   #46
tholub
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Originally Posted by johnfoss View Post
I always found it kind of interesting that 20" is almost exclusively used by hockey players, while 24" is almost exclusive in basketball. I think it's because the 24" wheels don't get in the way as much for basketball, but they do more in hockey. I would prefer the speed for both sports, but when watching top hockey teams, they seem to do just fine on the 20's.
We don't ride 24" unis for speed, we ride them for height. Gaining two inches is really important in basketball.

When I was debating and testing between 20" and 24", I didn't notice much of a speed difference. There are a lot more turning motions than straight-line motions in basketball, and the 20" is faster at turning. If I were purely playing a guard position, I'd probably go with the 20", but I often wind up playing under the basket where you need to be as tall as possible.
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Old 2018-02-19, 08:32 AM   #47
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Originally Posted by johnfoss View Post
I'm not a uni hockey expert, but my gut feeling is that the best wheel would be light and responsive, but that I wouldn't want a skinny tire. Also I wouldn't want a non-sturdy wheel
I agree with that, one further consideration that I believe could be useful is how much space a wheel takes up. Goalies more often than not use 24's to cover more goal, if you have two defenders and a goalie on 24's it may cover more of your goal from shots. It may also assist a defender in blocking players. Similar to how defencemen in ice hockey and field lacrosse use different equipment made (longer) for defending.
Equipment breakage is definitely an issue with most disciplines. Until things become competitive most will want something that never breaks. I think our sport is a long way from the equivalent of swimsuits that can only be worn for 1 race and cost $15,000.

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Originally Posted by johnfoss View Post
I always found it kind of interesting that 20" is almost exclusively used by hockey players, while 24" is almost exclusive in basketball. I think it's because the 24" wheels don't get in the way as much for basketball, but they do more in hockey. I would prefer the speed for both sports, but when watching top hockey teams, they seem to do just fine on the 20's.
Talking on the Hockey rulebook committee almost all the members believe 24's are too dangerous as they are too hard to decelerate (in comparison to 20's) That is why I decided to work out how much harder they were to decelerate (based on equipment not the rider weight). I think if we are really looking at "safety" then we should be looking at inertia, as a crap build on a 20" with 89mm cranks is harder to stop than a good 24" with 125mm cranks. 24's can also get in the way of your own stickwork occasionally.

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Originally Posted by tholub View Post
We don't ride 24" unis for speed, we ride them for height. Gaining two inches is really important in basketball.

When I was debating and testing between 20" and 24", I didn't notice much of a speed difference. There are a lot more turning motions than straight-line motions in basketball, and the 20" is faster at turning. If I were purely playing a guard position, I'd probably go with the 20", but I often wind up playing under the basket where you need to be as tall as possible.
Physics-wise is the turning ability of a wheel based on anything other than inertia of the wheel? I am wondering because when comparing a 24" that has a rotational inertia lower than a 20" it actually turns easier so I was assuming not.

Of course a 24" with less inertia than a 20" definitely wouldn't hold up to basketball. I had a previous light build that started pulling spokes through the rim when I was doing large amounts of hopping.

Last edited by Pinoclean; 2018-02-19 at 08:33 AM.
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Old 2018-02-19, 04:24 PM   #48
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Originally Posted by Pinoclean View Post
Talking on the Hockey rulebook committee almost all the members believe 24's are too dangerous as they are too hard to decelerate (in comparison to 20's) That is why I decided to work out how much harder they were to decelerate (based on equipment not the rider weight). I think if we are really looking at "safety" then we should be looking at inertia, as a crap build on a 20" with 89mm cranks is harder to stop than a good 24" with 125mm cranks.
I'm with you on that one; it's a rather silly thing to be worried about. (For the same reasons that I think your calculations are a bit silly, but this appears to be a case of silly begetting silly).

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Physics-wise is the turning ability of a wheel based on anything other than inertia of the wheel? I am wondering because when comparing a 24" that has a rotational inertia lower than a 20" it actually turns easier so I was assuming not.
You have to consider the biomechanics. Turning more or less happens as an exaggeration of your wobble to one side or the other; you initiate a turn to the right when your right pedal is on the way down. On a smaller wheel, the ground distance between turning opportunities is smaller and your natural circle size is smaller. A 20" that weighed as much as a 36" would still be easier to turn.
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Old 2018-02-19, 07:45 PM   #49
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Originally Posted by tholub View Post
You have to consider the biomechanics. Turning more or less happens as an exaggeration of your wobble to one side or the other; you initiate a turn to the right when your right pedal is on the way down.
When you begin to learn turning I think this is true however once your a competent rider I think you very often turn against your downward pedal.

Looking at this slalom there are quite a few instances where he quite easily initiates his turn away from his downward pedal. I think as you improve agility it is because you learn to not have to turn with your pedaling and can turn by rotating hips and dropping weight to one side instead.
https://www.youtube.com/watch?v=3FIYwukwGy0

It is a bit extreme but if we turn when that side foot is on the way down the roll out of this 36 would make it impossible to do what unigeezer is doing. The new 36 is much more manoeuvrable than the old one so I think it probably has a lot to do with it. From my experiments it makes a big difference despite wheel size not changing.

https://www.youtube.com/watch?v=JkzWOAdrPOg
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Old 2018-02-21, 04:52 AM   #50
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Originally Posted by tholub View Post
We don't ride 24" unis for speed, we ride them for height. Gaining two inches is really important in basketball.
Of course! I think I used to know that... 2" can make a big difference, not so much for shooting, perhaps, but definitely for defending! And I thought I was riding one for speed. Actually I was; because in my case I'm better at riding fast than at most of the "basketball" skills.
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Originally Posted by tholub
When I was debating and testing between 20" and 24", I didn't notice much of a speed difference.
I found similar, back in the day when I compared them for what we now call the IUF Slalom. My test times were about the same. Major difference was the pedals on the 20" being more likely to hit the ground, which is generally a deal-breaker in high-speed, sharp turns. But there was that one guy at Unicon 18, in the Slalom finals on his 20". Fast and smooth!
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I agree with that, one further consideration that I believe could be useful is how much space a wheel takes up.
Definitely. In hockey, everything is happening down at the end of your stick, where wheels will always be in the way. In basketball, some action takes place down low (dribbling), but a lot more takes place up above the wheel so the bigger size is less of an issue.
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Originally Posted by Pinoclean
Until things become competitive most will want something that never breaks. I think our sport is a long way from the equivalent of swimsuits that can only be worn for 1 race and cost $15,000.
I used something like that once, though not to such an extreme. In the Indoor Cycling World Championships (Artistic Bicycling and Cycleball) in 1986 (last time I competed), A connection had been made with the USA's Olympic organization and track suits were provided for the two American athletes. Those two were me, riding at the level of, perhaps, a German 7-year, and Greg Milstein (who hosted Unicon II a few months earlier), who had just finished only 2 weeks of triaining.

So we had these super-aerodynamic track (Velodrome) suits from the USA Olympic Team, to make us look reeeeeally good while went slowly around in circles. It was like wearing a full-body rubber band that was several sizes too small. TIGHT! And they didn't pass moisture. HOT! It was kind of like wearing a balloon, but at least they didn't fall apart from a single use! It was quite an honor to wear a USA Olympic Team uniform; I only wish I'd been unicycling; something I'm much better at! I looked really good when I missed the one transition trick that kept me from getting to my other high-scoring trick, and my score was pretty pitiful. Except compared to Greg. But he didn't have the lowest score. There was a guy from Malaysia that had only arrived that morning. Our coaches helped him memorize several basic figures, which was enough for him to enter, and add another new country to the sport of Artistic Bicycling! A few years later, they had the Indoor Cycling World Championships in Malaysia for the first time.

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Originally Posted by Pinoclean
Talking on the Hockey rulebook committee almost all the members believe 24's are too dangerous as they are too hard to decelerate (in comparison to 20's)...
Which makes one think about how dangerous uni-basketball is. But it's not the same. In hockey, there's a focus down on the floor, where all the action is, and everybody has a stick, which keeps one (or both) arms occupied. In basketball, pretty much everything except dribbling is above the waist, and only one person at a time has anything in their hands, which makes it a much safer environment for high speed riding in close quarters.
Quote:
Originally Posted by Pinoclean
Physics-wise is the turning ability of a wheel based on anything other than inertia of the wheel?
I imagine crank size is the other major part of that puzzle. Both sports call for a "medium-ish" crank length to balance speed with power. I used to play basketball with 140mm cranks, though today I bet more players use 125, as it's the common size for Track.
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Originally Posted by tholub View Post
On a smaller wheel, the ground distance between turning opportunities is smaller and your natural circle size is smaller.
20" wheels have an advantage in that they can do more things in a limited space than a larger wheel. This is easily demonstrated in the Sumo ring, if you've ever done that with different wheel sizes, or when trying to do a Freestyle performance on a small stage. A 20" wheel just fits more revolutions into the space than a 24" does, so you can do more within that space.
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Last edited by johnfoss; 2018-02-21 at 05:04 AM.
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Old 2018-02-21, 06:20 AM   #51
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Originally Posted by johnfoss View Post
Which makes one think about how dangerous uni-basketball is. But it's not the same. In hockey, there's a focus down on the floor, where all the action is, and everybody has a stick, which keeps one (or both) arms occupied. In basketball, pretty much everything except dribbling is above the waist, and only one person at a time has anything in their hands, which makes it a much safer environment for high speed riding in close quarters.
I don't think basketball is safer than hockey. At UNICON I've personally seen a dislocated shoulder and a broken arm, and in Rennes we had a knee injury which required stitches. In our local game we've had a number of broken wrists and fingers. It's definitely more dangerous than MUni.

Basketball is contested in much tighter spaces than hockey; if you have the ball, the defender is attempting to get as close as he can to you and grab the ball from you. Collisions in traffic are at least as common, probably more common than in hockey. But the danger comes from the nature of the sport, not from the size of the wheel.

Last edited by tholub; 2018-02-21 at 06:22 AM.
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Old 2018-02-24, 12:52 AM   #52
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Originally Posted by Pinoclean View Post
Physics-wise is the turning ability of a wheel based on anything other than inertia of the wheel? I am wondering because when comparing a 24" that has a rotational inertia lower than a 20" it actually turns easier so I was assuming not.
There's an interesting difference here between rolling and turning (for engineering geeks). For rolling, it's only really the mass of the rim/tyre which is important, not the inertia - because whilst a larger wheel has more rotational inertia than a smaller wheel with the same rim/tyre mass, for a given linear speed the rotational speed is lower and these things cancel out (given what you're interested in is the linear acceleration). However for turning, to turn 180 degrees both the small and the large wheel have to turn 180 degrees and it's rotational inertia which is important.

What also needs pointing out is that rotational inertia for rolling (where the rotation is around the horizontal axis of the axle) isn't the same as the rotational inertia for turning (where the rotation is around the vertical axis). For turning the average distance of the rim-tyre from the turning axis is lower, hence the rotational inertia is lower. However in both cases the rotational inertia is proportional to the wheel size. Hence for a larger wheel to be as easy to turn it has to be lighter than the smaller wheel.

Finally I'll add that ISTM that wheel mass/inertia has a more significant effect on turning than on linear acceleration, given we're only interested in rotational inertia not linear inertia and the rotational inertia of the wheel is a larger proportion of the total rotational inertia.

Of course there are also gyroscopic effects, but it's too much trouble to even start to think about the effect of those!
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Old 2018-02-24, 03:07 AM   #53
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There's an interesting difference here between rolling and turning (for engineering geeks).
No, even for me, and I havenít taken physics since I was a teenager, and usually donít even read about it (unless you count the book I have on Albert Einsteinís 1800-page FBI file), so I definitely donít qualify as an engineering geek. I think anyone who rides a unicycle -or even just watches one go by- has thought about these questions to some degree. Itís fascinating to see them put into words by people who know what they are talking about. Please continue!
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Old 2018-02-24, 03:08 AM   #54
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.....Of course there are also gyroscopic effects, but it's too much trouble to even start to think about the effect of those!
A scientific look at the gyroscopic effect may be quite interesting. Especially for touring at speed on a 36er I'd guess that the gyroscopic effect is a very large part of what makes the unicycle so easy to ride. The lighter the tire, the less gyroscopic effect. How much lighter can you go before having an adverse effect on riding?

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Old 2018-02-24, 05:02 AM   #55
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I'd guess that the gyroscopic effect is a very large part of what makes the unicycle so easy to ride. The lighter the tire, the less gyroscopic effect. How much lighter can you go before having an adverse effect on riding?
I recon there is more than enough gyroscopic effect in almost any wheel. The ease of the 36 is its slow response so it takes longer to get out of the stable zone. However this is a trade for responsiveness required when terrain changes and the rider gets out of that zone.

Most of my falls on my 36 are nothing to do with stability but rather because I cannot get anything like the acceleration I am used to on my other unis when I find myself too far forward. I have just fitted it with the new 500 gram (27%) lighter Nightrider. I'm really looking forward to taking it for a spin when I get over this rotten virus.

The new Nightrider is constructed much more like the lightweight tyres I use on my other road unis.

I am a big fan the Maxxis DTH (Drop-The-Hammer). My "standard" uni has a 24 x 1.75 DTH that only weighs about 440 grams. Many times its low mass allowed me to accelerate out of what seemed a certain fall.

I use a Maxxis Torch 29 x 2.10 on my 29 inch x 42 mm Dominator wheel for on the road. (They don't make a DTH for 29 inch.)

I have just set up a 26 inch Dominator wheel with a 26 x 2.15 tanwall, foldable bead DTH that only weighs 550 grams (less than half the weight of a Hookworm). It looks and feels great and I can't wait to ride it too.
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Old 2018-02-25, 08:57 PM   #56
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A scientific look at the gyroscopic effect may be quite interesting. Especially for touring at speed on a 36er I'd guess that the gyroscopic effect is a very large part of what makes the unicycle so easy to ride. The lighter the tire, the less gyroscopic effect. How much lighter can you go before having an adverse effect on riding?

Jim
Interesting you say that. I recall someone telling me 20 years ago that the 36" had more momentum than the 29", and so could push themselves over road bumps and impediments more easily. Of course, that was when they were heavier.

What is the gyroscopic effect? Can the rider experience it?
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Old 2018-02-25, 09:08 PM   #57
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Interesting you say that. I recall someone telling me 20 years ago that the 36" had more momentum than the 29", and so could push themselves over road bumps and impediments more easily. Of course, that was when they were heavier.

What is the gyroscopic effect? Can the rider experience it?
The 36" is marginally less affected by road bumps because its tire profile is taller, and you may be riding faster. The forward momentum is important, but the rotational momentum doesn't really have an effect on bumpiness. Forward momentum is mostly a function of velocity, so at the same forward speed, there's probably not much difference between the 36er and 29er.

The gyroscopic effect is not substantial in unicycle or bicycle wheels.
http://www2.eng.cam.ac.uk/~hemh1/gyrobike.htm
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Old 2018-02-25, 09:21 PM   #58
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The 36" is marginally less affected by road bumps because its tire profile is taller, and you may be riding faster. The forward momentum is important, but the rotational momentum doesn't really have an effect on bumpiness. Forward momentum is mostly a function of velocity, so at the same forward speed, there's probably not much difference between the 36er and 29er.

The gyroscopic effect is not substantial in unicycle or bicycle wheels.
http://www2.eng.cam.ac.uk/~hemh1/gyrobike.htm
Well, it feels like, speed being equal, the inertial weight of the 36" makes it easier to roll up curbs and over impediments than on a 29" or smaller tire. I can sort of relax riding the 36" off road over roots, etc, which I cannot do on a 29".

Thanks for the input, and for the gyro link, which I didn't exactly understand esp as it applies to unicycle.
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Old 2018-02-25, 09:28 PM   #59
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Well, it feels like, speed being equal, the inertial weight of the 36" makes it easier to roll up curbs and over impediments than on a 29" or smaller tire. I can sort of relax riding the 36" off road over roots, etc, which I cannot do on a 29".
It's not the inertial weight which makes rolling up curbs easier, it's the tire height. Imagine a 1cm tall object being rolled over by a 2cm tall wheel; that's a big bump, right? But on a 29er or a 36er, it would be trivial. The ease of rolling over an obstacle is a function of the ratio of the size of the wheel to the size of the obstacle, which will always be higher for a 36er than for a 29er. If a 36er and 29er wheel of the same weight were moving the same speed, it would still be easier to roll over obstacles on the 36er.
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Old 2018-02-25, 09:34 PM   #60
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Originally Posted by tholub View Post
The 36" is marginally less affected by road bumps because its tire profile is taller, and you may be riding faster. The forward momentum is important, but the rotational momentum doesn't really have an effect on bumpiness. Forward momentum is mostly a function of velocity, so at the same forward speed, there's probably not much difference between the 36er and 29er.
Bigger wheels essentially filter smaller dips in the road (which are more common than bumps), since they can't go as deep into them, that's the main reason they are less affected by unevenesses in the road.


This sort of shows what I am on about, now imagine a 36" wheel with that bump, it wouldn't even get all the way down into the dip.
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The gyroscopic effect is not substantial in unicycle or bicycle wheels.
http://www2.eng.cam.ac.uk/~hemh1/gyrobike.htm
Yes. if you don't believe that source, you can easily test this by picking up your unicycle at the saddle, and turning it like you would when riding around a corner, one time with the wheel spinning, one time without, the difference will be very little.
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