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Old 2017-05-26, 08:40 AM   #61
maestro8
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There have been many attempts on this forum to model the unicycle in the simplest of modes, and all have failed, because a model is but a gross approximation of a very complex system. In this case, the system is a bimodal double pendulum, a system that has a very strong sensitivity to initial conditions.

Whereas some systems can be approximated with a mathematical model, this can only be done when all first-order effects are well-understood, and higher-order effects add to the approximation at lower orders of magnitude. A classic example is ballistics calculation. We can use Newton's equations and predict with reasonable accuracy where a projectile will land, based only on initial conditions, without accounting for the effects of drag, wobble, and such. These factors don't change the calculation but for a few percent.

With our double pendulum, the first-order effects are strongly sensitive to the conditions in which the inputs are applied: pressure on the pedal when the unicycle is in just the right orientation will result in a very efficient translation to forward motion. Pressure on the pedal when the unicycle is off-balance will result in a very embarrassing face-plant for the pilot. There is simply no way to model all the dynamics of a rider pedaling up a hill as this is a chaotic system: there is no repeatable behavior a unicycle-rider system can exhibit, even if the rider's inputs are perfectly replicated millions of times.

Reading through this thread, I feel I'm reading the text of an author that's studied a subject just long enough to know how to use its parlance in conversation, but not long enough to understand the limits of his study. Then, said author is using his parlance to expound on an activity he's only seen on YouTube through a haze of insufflated model glue and malt liquor, pounding his theories out on a nicotine-stained keyboard whilst occasionally kicking the dog beneath his desk. Failing to get a reaction from the dog, our author continues to beat his keyboard at an increasingly frantic rhythm, straining to milk this forum for the slightest shred of recognition of his "genius", yet failing to even see the very text he's producing.

Chaos theory isn't covered in Physics 101, and there's no CRC Handbook of Unicycle Tables, so unless you just got your PhD, you're not really going to get anywhere in this thread. Please, for the love of Peck, just go ride your grundle up a mountain, then get back to us about how much ball sweat you wrung out of your riding panties. We only accept empricial evidence here.
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Old 2017-05-26, 11:18 AM   #62
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Quote:
Originally Posted by vookash View Post
What I would like to emphesize in first part of the discussion regarding the rotational weight is that even when climbing, we on unicycle slow down and speed up the wheel several times each revolution to maintain the balance. And even if these are micro slow downs and speed ups for an experienced rider, we loose a lot of energy on that and that is where wheel weight makes the difference.
This is simply a bad understanding of physics. Make all the arguments about unicycles and wobble you want, but it's a basic fact that a flywheel rolling up a hill conserves input energy and releases it doing useful work - if you overspeed it sometimes, you get that all back when you underpush it at others.

Until there's mutual understanding of such a fundamental isolated principle, there's no point in having a conversation about more complicated topics like unicycles.

Note that no one has been trying to model an actual unicycle here - rather, just look at the most basic underlying mechanisms so that the more complicated ones not modeled can be tested in the real world against a known reference
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Old 2017-05-26, 11:21 AM   #63
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Originally Posted by tholub View Post
As I said at the beginning, this has been tested. We did a whole series of tests with different wheel sizes and crank configurations on the same climb in training for Ride the Lobster. What we found was that the rider was by far the most important factor (I believe the place ordering was the same on every attempt), and that riders were always the fastest on the configuration they were most comfortable with.
If you found that riders are always fastest on the configuration they are most comfortable with, that substantially invalidates the result of experimentation with different wheel sizes - it basically says that you didn't try them all long enough to tune in to riding each. That's not just a learning process, something like mashing vs. spinning is ultimately involves muscle training, so it would not change quickly.
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Old 2017-05-26, 02:47 PM   #64
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Quote:
Originally Posted by Engineer on a Unicycle View Post
This is simply a bad understanding of physics. Make all the arguments about unicycles and wobble you want, but it's a basic fact that a flywheel rolling up a hill conserves input energy and releases it doing useful work - if you overspeed it sometimes, you get that all back when you underpush it at others.
You're missing the extremely obvious and fundamental point that:

F = m * a

So for greater m (mass of the wheel), with F (force input by the rider) held constant, a (acceleration of the wheel) is lesser.

Or more simply: Heavier wheels are slower.

Quote:
Until there's mutual understanding of such a fundamental isolated principle, there's no point in having a conversation about more complicated topics like unicycles.
Now you've said two correct things.
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Old 2017-05-26, 02:50 PM   #65
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Quote:
Originally Posted by Engineer on a Unicycle View Post
If you found that riders are always fastest on the configuration they are most comfortable with, that substantially invalidates the result of experimentation with different wheel sizes - it basically says that you didn't try them all long enough to tune in to riding each. That's not just a learning process, something like mashing vs. spinning is ultimately involves muscle training, so it would not change quickly.
That's one way to look at it. Another way to look at it is that the physiological factors may dwarf the mechanical factors in climbing speed. It is very possible that the human body can't be optimized for two different configurations at the same time.
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Old 2017-05-26, 02:56 PM   #66
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Quote:
Originally Posted by Engineer on a Unicycle View Post
That's dangerously close to saying that the bicyclists are faster "because they're faster".
You seem to have missed that it's based upon experimental observation (which I mentioned in a previous post, hence the reference back) - the point being that the bicyclists are already spinning a bigger gear faster, so put them on a smaller gear there's zero chance of them not also spinning that faster.

Quote:
This is simply a bad understanding of physics. Make all the arguments about unicycles and wobble you want, but it's a basic fact that a flywheel rolling up a hill conserves input energy and releases it doing useful work - if you overspeed it sometimes, you get that all back when you underpush it at others.
Meanwhile you seem to have a bad understanding that not everything is physics. When balancing on a unicycle you put energy in to speed the wheel up and to slow it down - we're into the world of physiology here, where even if you think you're just letting your legs go round with the wheel there will be energy used to move those muscles. So no, the flywheel effect doesn't conserve all of the energy, not when it is connected to a pair of human legs with a significant amount of hysteresis.
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Old 2017-05-26, 03:48 PM   #67
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Maestro8 is right about the complexity of the system you guys are discussing. Not everything is physics, but physics can account for more than most of you are saying it can, provided you figure out all the forces at work here, which Maestro8 says is not possible. He may be right about that, I don't know.

F = m * a is obviously an applicable formula, but I don't think it tells the whole story of the effect of wheel weight on speed of a travel. Maybe for an exercise bike it would, but for a unicycle going up a hill...
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Old 2017-05-26, 04:53 PM   #68
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Originally Posted by song View Post
Maestro8 is right about the complexity of the system you guys are discussing. Not everything is physics, but physics can account for more than most of you are saying it can, provided you figure out all the forces at work here, which Maestro8 says is not possible. He may be right about that, I don't know.

F = m * a is obviously an applicable formula, but I don't think it tells the whole story of the effect of wheel weight on speed of a travel. Maybe for an exercise bike it would, but for a unicycle going up a hill...
F = m * a is a start. You also have to include rotational inertia, I = m * r^2, which is why rotational mass (m) is more important than non-rotational mass, and why smaller wheels (r) accelerate faster than larger wheels.

But the important issues, I'd say, are the physiological system (the rider's ability to impart forward force on the pedals over time), and the non-linearity of the force vectors (how much of the input force goes to sideways motion). The first factor is lower and the second higher on unicycles relative to bikes.

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Old 2017-05-26, 10:40 PM   #69
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Quote:
Originally Posted by Engineer on a Unicycle View Post
it's a basic fact
For all the work you're putting into insulting the intelligence of others, consider you could be putting that work into better explaining yourself so you don't have to write 50 posts all attempting to make the same point.

Quote:
a flywheel rolling up a hill conserves input energy
Why are you belaboring this point? There aren't any parallels between that simplified example and the topic of this thread: there are no riders capable of "overspeeding" a wheel during a hill climb, and there is no energy being conserved in a system as lossy as the combination of unicycle+rider.

Quote:
Until there's mutual understanding of such a fundamental isolated principle, there's no point in having a conversation about more complicated topics like unicycles.
There are many here who are solidly grounded in fundamentals. Several with advanced degrees in said fundamentals, currently in this thread.

Consider the difficulty here isn't your audience's grasp of physics, but your own inability to communicate, to draw the line between your model and the problem at hand. I suspect you're beating on "basic facts" with such volume and frequency because this is where you, too, are stuck.

Quote:
Note that no one has been trying to model an actual unicycle here - rather, just look at the most basic underlying mechanisms so that the more complicated ones not modeled can be tested in the real world against a known reference
No one is waiting for your "known reference" to be constructed, studied and understood to being testing in the real world. There are thousands of folks who have already been doing this "testing" for decades now, and several are in this thread, giving you the results of their "tests". tholub and johnfoss are two of our community's subject matter experts on this very topic!

This being said, if you can't reconcile your model with their experience, it may well be the case that your model is flawed. It appears your ego is standing in the way of your ability to consider that case...

P.S. Have you ever ridden a unicycle? Much of what you're posting speaks to the contrary.
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Old 2017-05-27, 05:21 AM   #70
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Quote:
Originally Posted by maestro8 View Post
...said author is using his parlance to expound on an activity he's only seen on YouTube through a haze of insufflated model glue and malt liquor, pounding his theories out on a nicotine-stained keyboard whilst occasionally kicking the dog beneath his desk.
But are you describing Tom, or Engineer?
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Originally Posted by maestro8 View Post
Please, for the love of Peck, just go ride your grundle up a mountain, then get back to us about how much ball sweat you wrung out of your riding panties. We only accept empricial evidence here.
Should that be in milliliters or grams?

Reference: "Peck" refers to George Peck, one of the fathers of Mountain Unicycling. He taught a lot of us how to ride up steep things, and gave us the motivation to do it.
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Originally Posted by Engineer on a Unicycle View Post
...it's a basic fact that a flywheel rolling up a hill conserves input energy and releases it doing useful work...
I suppose it's also a basic fact that unicycles make lousy flywheels. They don't go straight, while a bicycle essentially has two flywheels, minus a slight amount for small steering corrections in the front wheel.

Speaking of lousy flywheels, today I was riding an adult-sized tricycle (don't ask). Ever try to go fast on one of those? 6" wide, heavy wheels. High-torque pedaling pushes the wheel side to side pretty hard. You can counteract this with the handlebars, but not perfectly and that takes a bunch of energy. The faster you pedal, the harder it is to keep that oscillation from fouling your steering.

Then I had a full-sized adult standing on the back of the trike, and was trying to keep up with the other tricycle, which had a very small person on the back. And I had my backpack camera bag on (again, don't ask), so I had to lean really far forward to not lose my passenger, so I had crap leverage with the handlebars. But I had to pedal really hard to keep up, so my arms got really tired! Moral of the story? Stop trying to change the subect.
Quote:
Originally Posted by Engineer on a Unicycle View Post
If you found that riders are always fastest on the configuration they are most comfortable with, that substantially invalidates the result of experimentation with different wheel sizes - it basically says that you didn't try them all long enough to tune in to riding each.
Except for the bikes, which were apparently 20% faster even if they weren't what the riders were most comfortable with. Also they were aware of the comfort factor. Most of us have ridden enough different stuff to know we will only get fully efficient with it after plenty of time for our bodies to adjust. I'm still kind of getting used to my new Muni, which I got last summer. Old one had 24x3" tire and 145mm cranks, and new one has 26x3" tire and 150 cranks. Mostly I just haven't done enough rides on it...
Quote:
Originally Posted by tholub View Post
You're missing the extremely obvious and fundamental point that...
I've got to get the two of you into a Mexican restaurant (or Sushi place) with some beers, preferrably after a long ride with lots of climbing. I think you guys could go forever! The place would close and you'd be the only ones left there.

Got to get to know people in person, when possible. My wife and I are considering finally making another trip to NY in September during the NYC Uni Fest. I need to re-connect with the NY unicyclists I once knew, and meet some of the new ones!

I wish I could recommend some good, large climbs in your area, but I don't know your local area well enough. I know there are some fairly steep hills in Manhattan, but nothing big. I mostly rode in my local area (Nassau County) when I lived out there, where all the big hills are along the north shore. Talk to road bikers and see if they can recommend some challenging climbs that aren't too far away.
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Originally Posted by tholub View Post
Or more simply: Heavier wheels are slower.
They are, and yet so many of us continue to choose those heavy 36" wheels. And why was it faster on the "lugging" sections of Mt. Diablo? It's like we had a set cadence that allowed us to continue for long-ish periods, but that was the same whether we were on the 36" or the 29". So the (much heavier) 36" was faster under those conditions.

So, anyone going up to NAUCC in July? Besides me? Driving; so I get to bring lots of toys!
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Old 2017-05-27, 05:27 AM   #71
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They are, and yet so many of us continue to choose those heavy 36" wheels. And why was it faster on the "lugging" sections of Mt. Diablo? It's like we had a set cadence that allowed us to continue for long-ish periods, but that was the same whether we were on the 36" or the 29". So the (much heavier) 36" was faster under those conditions.
Harrison just tied Beau's second-place time on the Mt. Diablo Challenge, at 1:14 (one minute off the record pace) on a 29er. I did it in 1:20 and 1:21 on a 29er. 'cause that's what I was used to, and I think I beat all the 36ers except Beau and Geoff Huntley. (My bike time: 1:09, though not at the Challenge, so slightly different).
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Old 2017-05-27, 09:59 PM   #72
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Wow. I thought this was a thread about unicycling Mt. Everest until I saw that both Tom and Jason had chimed in. I missed so much.

I would propose to Engineer-on-a-Unicycle that he could have his choice of unicycle and his choice of rider trained specifically for the event. In addition, he could have the surface of his choice including the average climb slope he desires as well as a periodic, alternating gradient on top of it with period equal to half the circumference of his chosen wheel size and whatever amplitude optimizes his rider's climb efficiency. That rider on that unicycle under those conditions would be wiped off the same course by Tom on his own commuter bike. And Tom is no world-class bike rider.

Unicycles are fun and challenging but, even idealized, they are no competition for a bicycle.
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Old 2017-05-28, 12:23 AM   #73
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Yeah, or as Finnspin said recently on a different thread: "There are only two things a unicycle can beat a bike in, wich are transportability and fun."
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Old 2017-05-28, 06:03 AM   #74
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Everesting
I made a quick chart of my Diablo times.
My fastest unicycle time is faster than my bike times. This greatly puzzled/puzzles me.

So given my biking and unicycling experience, if I can shuttle down the climb, without more data, I couldn't say which is more difficult for me. I probably will never find out first hand.
(Tried once on a bike and failed.)



Question
This site defines torque effectiveness as (P+ + P- )/ P+
https://www.cyclinganalytics.com/blo...dal-smoothness

The site above states torque effectiveness on a bike usually ranges from 60% to 100%.
How about on a unicycle for a given rider? Being comfortable on a given machine will likely have a very large bearing on this.

How close to 100% can I get on some given climb on my bike or my unicycle?

The question I want to answer for my riding(especially certain hills I have ridden):
For different uphill gradients, does the overall rider+cycle weight reduction of a unicycle outweigh the decrease in torque effectiveness?



Why this question
Ignoring rolling resistance difference, aerodynamics, gearing,

Unicycle benefits:
reduced weight[~5% total mass]
drivetrain losses[~1% less losses][assume negligible compared to reduce weight]

Unicycle cons:
energy to balance[to be determined]



How to test
Same crank length, same power meter, same rider, same climbs multiple times.
Check if the time differences match what my power meter says as far as power and torque effectiveness.



To do
Build powermeter(need to redesign for better accuracy/precision with KH cranks)
Software and data collecting(don't know how much more difficult to get more data analysis compared to just sending to Strava)
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Old 2017-05-29, 03:50 AM   #75
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Well, I'm no physicist, and I'm not sure what a bimodal double pendulum is, but to my layman's ear it sounds like a good description of a unicycle in motion. As far as formulas, the only one I usually use to explain unicycling is to say that if you ride a bike to some place, getting there is half the fun, but if you ride to that same place on a unicycle, getting there is more like three quarters of the fun.

Mount Diablo is a journey of about 18km, with a rise of about 1000m, and I think my formula might even explain why a 29” unicycle could conceivably get you up there faster than a bike: you don’t get bored!
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