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Old 2019-10-29, 08:16 AM   #16
Quax1974
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Originally Posted by tholub View Post
The idea that unicycles could be faster than bikes, on any kind of terrain, given equivalent rider strength, is completely absurd and contradicted by every data point we have.
I think you are right.

I am pretty sure the energy loss of the drive train on a good bike is way less than the energy loss of maintaining balance on a unicycle.

And then add to that the possibility to change gears to keep optimum cadence / momentum on incline changes.
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Old 2019-10-29, 10:53 AM   #17
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Originally Posted by Quax1974 View Post
I think you are right.

I am pretty sure the energy loss of the drive train on a good bike is way less than the energy loss of maintaining balance on a unicycle.

And then add to that the possibility to change gears to keep optimum cadence / momentum on incline changes.
Exactly!

I often overtake bicycles when riding up moderately steep and longer hills. It's not because a unicycle is better up hills, it's simply that I have no gearing and so have to compensate by riding at the optimum speed for that unicycle's fixed configuration on that hill. The bicycle rider can change down through the gears as the speed slows, a unicycle can't. I don't want to ride some hills that fast, but slowing down is often inefficient and wastes energy so I maintain a speed that works best.

As unicycle riders we must overcome the huge deficiencies a unicycle has compared to a multi-geared and mostly self balancing bicycle, and as such the rider can become a good hill climber, not the unicycle.
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Old 2019-10-29, 10:32 PM   #18
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Originally Posted by tholub View Post
The idea that unicycles could be faster than bikes, on any kind of terrain, given equivalent rider strength, is completely absurd and contradicted by every data point we have.

But, as you say, there are many unicyclists, including Ben and Harrison, who are faster than many bicyclists. Ben is an amazing athlete who would be beating 1:00 on Diablo if he were training on bike. (Harrison, probably, also). Glenn Drummond, the previous record-holder on Diablo at 1:13 (since 2005), was an extremely strong bike rider, and had finished in the top 5 in the bike category, and still finished sub-1:00 as recently as 2017 (at age 55).
A single data point is hardly evidence. In either case, my original statement was regarding a constant gradient, where the unicycle wheel/crank ratio is optimal. If Mt Diablo has lots of different gradients it doesn't amount to what I said.


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Exactly!

I often overtake bicycles when riding up moderately steep and longer hills. It's not because a unicycle is better up hills, it's simply that I have no gearing and so have to compensate by riding at the optimum speed for that unicycle's fixed configuration on that hill. The bicycle rider can change down through the gears as the speed slows, a unicycle can't. I don't want to ride some hills that fast, but slowing down is often inefficient and wastes energy so I maintain a speed that works best.

As unicycle riders we must overcome the huge deficiencies a unicycle has compared to a multi-geared and mostly self balancing bicycle, and as such the rider can become a good hill climber, not the unicycle.
Be careful with mechanistic reasoning. The human body is complex and this type of reasoning is the lowest level of evidence that we ascribe a level to.

You could counter that statement with similar mechanistic logic: Most unicyclists spend little effort balancing on the road. Unicycles are lighter than bikes. Track bikes are also fixed gear, it is not an impediment if the terrain is constant.

Yes, I did the same, but there is a paucity of evidence and I was commenting on Harrisons statement, and also on some of my own observations on my own hillclimb routes (as a bicyclist/unicyclist).

Last edited by GizmoDuck; 2019-10-29 at 10:59 PM.
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Old 2019-10-29, 10:37 PM   #19
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Originally Posted by tholub View Post
Ben is an amazing athlete who would be beating 1:00 on Diablo if he were training on bike. (Harrison, probably, also)
This is for Harrison to comment, but it doesn't look like you should be including it in your 'data point':

Quote:
Originally Posted by unicycleharry View Post

Interesting my old bike time is considerably slower, and only made up time on the two flat/downhill sections.
What I was commenting on, as well as personal data.

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Old 2019-11-01, 05:23 AM   #20
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I think it can be close between a bike and unicycle.

Bike: At least around 2% drivetrain loss? (exclude tires, assume equal for unicycle and bike).

Here's an idea to calculate effort required to balance a unicycle:
Going uphill for me, I don't believe I push backwards more than normal(biking) to balance, it's just pushing forward more or less.
Thus, my model for balancing is pushing 0-10% more on some pedal strokes, and 0-10% less on other pedal strokes. This makes it approximately up to 1.5% more difficult. (explanation in next paragraph)

For example, instead of riding at 200W smoothly (ie on a bike), you ride at 220W for a few pedal strokes, and 180W for the next few pedal strokes. This is harder than just riding at 200W continuously. Bicyclists sometimes use "normalized power" to describe this. If you average 200W, and never go above 220W or below 180W, normalized power maxes out at around 203W. So it is 1.5% more difficult. This is worst case though.. if it's just 220W for a few seconds, followed by 180W for a few seconds, repeatedly, it's more like 201W normalized power (0.5% more difficult). Normalized power obviously isn't perfect, it's just some equations people thought up of, but it works well enough for bicyclists to gauge their effort.

I think a proficient unicyclist corrects with less than +/-10% variations for a smooth uphill road, so from this point of view, balancing effort could be less than 0.5%.


Obviously, if the correction happens by pushing backwards more, versus just letting up a bit, then it could be be wasting a lot more. With 10% variation, that could be as much as, 10% to pedal harder, then 10% pushing backward, resulting in 20% extra effort. However, I rode Diablo with a powermeter pedals before on both unicycle and bike, and my torque effectiveness was in a similar range as when I bike. So I think my assumption that balancing comes from pedal forward more or less could be true.


As gizmoduck said, with the wrong gradient and thus non-ideal cadence, this easily goes out the window.
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Old 2019-11-01, 07:15 AM   #21
tholub
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Originally Posted by unicycleharry View Post
Obviously, if the correction happens by pushing backwards more, versus just letting up a bit, then it could be be wasting a lot more. With 10% variation, that could be as much as, 10% to pedal harder, then 10% pushing backward, resulting in 20% extra effort. However, I rode Diablo with a powermeter pedals before on both unicycle and bike, and my torque effectiveness was in a similar range as when I bike. So I think my assumption that balancing comes from pedal forward more or less could be true.
You're leaving out the inefficiency of the wobble. Unicycles don't travel in a straight line; they wobble around their axis with every pedal stroke. (This is also true of bicycles but to a much lesser degree). That wobble increases both the effective distance traveled, and the translation of power input into forward momentum.
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Old 2019-11-01, 09:00 AM   #22
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Originally Posted by GizmoDuck View Post
Be careful with mechanistic reasoning. The human body is complex and this type of reasoning is the lowest level of evidence that we ascribe a level to.
The only mechanical "reasoning" was related to machines, not human bodies. The reasoning provided is not evidence so please do not judge it's quality. It's just an opinion based on personal experience and observation, like everyone else.

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Originally Posted by GizmoDuck View Post
Unicycles are lighter than bikes.
Spend enough and bikes are lighter than a uni. My 29" comes in at 8.5 kg, that's heavier than many bikes. A few Kg here and there is not part of these discussions, it just too many pies.


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Track bikes are also fixed gear, it is not an impediment if the terrain is constant.
Not an advantage either.
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Old 2019-11-01, 02:23 PM   #23
unicycleharry
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Originally Posted by tholub View Post
You're leaving out the inefficiency of the wobble. Unicycles don't travel in a straight line; they wobble around their axis with every pedal stroke. (This is also true of bicycles but to a much lesser degree). That wobble increases both the effective distance traveled, and the translation of power input into forward momentum.
Yes, that is true. Handlebars help with this, but is definitely a disadvantage. However, wouldn't a squiggly line just mean a unicyclists rides at a slightly lower effective gradient? This would increase rolling distance and rolling resistance per straight distance covered, but at about 10W of rolling resistance for good tires, 5% increase of rolling distance and thus rolling resistance losses is quite small. 0.5W?

The resistance per squiggly traveled distance should be very similar to resistance per straight distance. The rolling resistanve coefficient may be a few percent more as the tire takes more sideways loads, but even so, I think it's tiny.

Lightly squiggly movement could change aerodynamics too, but we are currently quite slow on unicycles it really shouldn't matter either.

Don't know how squiggly riding's effect can be quantified, but maybe it's possible?
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Old 2019-11-01, 03:35 PM   #24
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Forgot to mention momentum. I don't think it's an issue, like I said it's like going up a lightly lower gradient. The squiggly path will have a bit more rolling resistance, but I don't think it's much. For example, a bicycle making a turn on a smooth surface doesn't loose much more speed than if it were to coast going straight. If the squiggliness is just a few degrees at maximum, I don't think there's much loss. Cornering rolling resistance on thin bicycle/unicycle tires.. maybe there's a study out there somewhere..

For weight, I think there is a difference.
My unicycle weighs 10.5lb (5kg). Compared to the handicapped bike with gears that aren't necessary for our perfect-gradient- course, the unicycle was easy to build and probably lighter than every bike that was at Mt. Diablo Challenge. A 5kg bicycle would require a lot of fancy expensive carbon parts. Yes, even 3kg bike is out there... But my unicycle also has a lot of "easy" weight it could lose if there was a market for stupid light unicycles. Aluminum frame, aluminum saddle, solid steel hub, aluminum cranks, disc brakes; technically it is not hard to make these parts on the unicycle lighter, there's just no weight weenie unicycle market.

My bike that costs about the same as my unicycle weighs twice as much. 5kg is a lot. Even 1kg is a lot, at my weight of 60kg, 1kg is more than a 1% change.

At least, that's my reasoning for why my bike times don't blow my unicycle times out of the water... I think gradient varying from 3-7%, on climbs like Mt. Diablo, account for a big portion of the 15% slower unicycle times Tom noted. That's 5%+/- 2%, a 40% variation. That's about 3 or 4 gear changes on a road bike, which every unicycle currently lacks.

Last edited by unicycleharry; 2019-11-01 at 04:03 PM.
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Old 2019-11-02, 12:42 PM   #25
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Quote:
Originally Posted by tholub View Post
You're leaving out the inefficiency of the wobble. Unicycles don't travel in a straight line; they wobble around their axis with every pedal stroke.
That depends on the rider.

Quote:
Originally Posted by BruceC View Post
The only mechanical "reasoning" was related to machines, not human bodies. The reasoning provided is not evidence so please do not judge it's quality. It's just an opinion based on personal experience and observation, like everyone else.
I was also offering mine, based on personal experience, and commenting on Harrisons bicycle vs unicycle time.

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Originally Posted by BruceC View Post
Spend enough and bikes are lighter than a uni. My 29" comes in at 8.5 kg, that's heavier than many bikes. A few Kg here and there is not part of these discussions, it just too many pies.
My racing 29 sits around 4kg, without any customised parts. The UCI has a min 6.8kg weight limit for race bikes.
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Old 2019-11-02, 01:21 PM   #26
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Originally Posted by unicycleharry View Post
I think it can be close between a bike and unicycle.

Bike: At least around 2% drivetrain loss? (exclude tires, assume equal for unicycle and bike).

Here's an idea to calculate effort required to balance a unicycle:
Going uphill for me, I don't believe I push backwards more than normal(biking) to balance, it's just pushing forward more or less.
Thus, my model for balancing is pushing 0-10% more on some pedal strokes, and 0-10% less on other pedal strokes. This makes it approximately up to 1.5% more difficult. (explanation in next paragraph)

For example, instead of riding at 200W smoothly (ie on a bike), you ride at 220W for a few pedal strokes, and 180W for the next few pedal strokes. This is harder than just riding at 200W continuously. Bicyclists sometimes use "normalized power" to describe this. If you average 200W, and never go above 220W or below 180W, normalized power maxes out at around 203W. So it is 1.5% more difficult. This is worst case though.. if it's just 220W for a few seconds, followed by 180W for a few seconds, repeatedly, it's more like 201W normalized power (0.5% more difficult). Normalized power obviously isn't perfect, it's just some equations people thought up of, but it works well enough for bicyclists to gauge their effort.
I can see how it's calculated, but I can't find references as to how this 'normalisation' is calibrated physiologically. It is also aimed at large variations in power output (ie going up/down hills), rather than the minute corrections we make for balance.

Your example of 180-220W is a 20% variation in power output, which seems excessive. The natural variation of pressure within the pedaling circle would be many orders of magnitude more than the amount of pressure adjustment needed for balance, and both are averaged out by the power meter.
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Old 2019-11-04, 01:05 AM   #27
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Originally Posted by GizmoDuck View Post
I can see how it's calculated, but I can't find references as to how this 'normalisation' is calibrated physiologically. It is also aimed at large variations in power output (ie going up/down hills), rather than the minute corrections we make for balance.

Your example of 180-220W is a 20% variation in power output, which seems excessive. The natural variation of pressure within the pedaling circle would be many orders of magnitude more than the amount of pressure adjustment needed for balance, and both are averaged out by the power meter.
I also couldn't figure out how the equation for normalized power was created and how accurate it is. Based on it's formula, shorter term variations (<<30seconds) basically disappear, since it uses a 30s rolling average. My +/-20% example calculation alternates 220W for >30seconds, 180W for >30seconds. This is a worst case scenario, giving 1.5% efficiency loss. Thus, if balancing is <20% force variation for <<30seconds, the efficiency loss will most likely by <1.5%.

I don't know how this can be calibrated easily.. But I think it at least shows that unicycling losses (balance + squiggle) compared to a bike, if at the right gradient/gearing, are likely not 10%, but more on the order of 1%, or less.
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