I was wondering if anyone has considered using a sliding weight to enhance the fly wheel effect of large diameter unicycle wheels.
The way I picture it working is having a light weight (few ounces) that starts at the hub (or close to it) when the wheel is at rest, and it slides out as speeds pick up. It would allow the wheel to accelerate faster then if the weights started out on the rim.
It’s not something that I would make, but it’s just an idea that popped into my head while walking the dog and thinking about the brain yo-yo.
And what is the point of adding the weights in the first place? I could only see this being useful if you wanted to maintain high speeds, not getting to them. Is that what you mean? I’m not familiar with the “flywheel effect” term.
The higher weights add stability to the wheel when riding at high speeds. This is why some people like cokers so much. By making the weight slide out, it allows you to start riding with a wheel with a smaller rotating inertia then a wheel with static weights on the rim.
I personally think this is an excellent idea. The only isse I can see with it is that you would have to springload the weights so they didn’t drop to the bottom of the wheel when you first start, although this isn’t a huge deal.
What would be cool is to be able to control the distance between the axle and the weights. That way when you really want an extra boost in speed, you could simply pull the weights to the center of the wheel. That’d kick your rpms up insanely quickly, althought it may also kill you…
Couldnt you just put some fishing weights on the spokes, that would almost instantaneously whip to the rim, and with fishing weights, you could get them easily, cheaply and in many different weights and sizes.
There was a company a few years ago that made a 6 speed shifting bicycle. It worked the same way that daino149 is talking about. As you pedaled the bicycle faster, it would cause the weights which were connected to the rear derailer to move outward making the derailer move to a higher gear. When you slowed down, it would shift back down to the lower gears.
“daino149” <daino149@NoEmail.Message.Poster.at.Unicyclist.com> wrote in
> I was wondering if anyone has considered using a sliding weight to
> enhance the fly wheel effect of large diameter unicycle wheels.
> The way I picture it working is having a light weight (few ounces) that
> starts at the hub (or close to it) when the wheel is at rest, and it
> slides out as speeds pick up. It would allow the wheel to accelerate
> faster then if the weights started out on the rim.
As you probably understand, the stability effect of your rotating wheel
increases with speed anyway, Your lead weights would be adding to the rim
and tyre weights, but unless they are a significant proportion of the
tyre/rim weights they will have negligible effect.
One weight would throw you out of balance, so you would need at least two.
It is an interesting conversation piece, but I doubt it will have much
practical value. I would suggest a heavier tyre and sacrifice that bit of
acceleration for the added stability if you need it. Remember of course
that you add straight line stability, and thereby reduce manoeuverability.
On Fri, 11 Feb 2005 14:32:37 -0600, “daino149” wrote:
>The way I picture it working is having a light weight (few ounces) that
>starts at the hub (or close to it) when the wheel is at rest, and it
>slides out as speeds pick up.
At the bottom part of the cycle, gravity helps the weights go towards
the rim, while at the top part gravity works the other way. So at
intermediate speeds, all the weights may yoyo back and forth. How
annoying would that be?
I assume that the weights are spring-loaded to stay near the hub?
Since the “centrifugal force” is low near the hub (low radius) you
need quite a lot of rotational speed before they move out, if at least
the spring is strong enough to overcome gravity.
I like gerblefranklin’s idea about a boost derived from conservation
of rotational momentum. Not so much for a unicycle (you have to be
aple to pedal at that speed anyway) but it would be great for a bike
or car. Not very practical though, since you have to lug around all
that weight all the time, but it might be handy for the human-powered
Klaas Bil - Newsgroup Addict
people who unicycle are shyly exhibitionistic - GILD
You seemed to see the same problems as i’ve been seeing, but I just noticed another. Assuming we can properly adjust the springs to overcome gravity but still move to the rim at the right speeds, we have to again take into accout conservation of angular momentum. As those weights move outward, they will have the effect of slowing the wheel down. Thus, you don’t really have a way around the severly reduced acceleration.
I think my idea could work on a bueshifted or jackshifted coker, since you’d them be able to spin the wheel MUCH faster.
Water inside the tire would add weight but would probably slow you down. Since water is not a solid it would have a tendency to stay at the bottom of the tire. Even if you could get all the air out and fill the tire completely with water, I think you would still feel the effect of the water moving inside the tire. When you start moving, the tire would move but the water would create a dragging effect until the water’s rotational speed catches up with the tire. However, what if you could fill the tire with water and freeze it?
That’s just asking for a blowout. Liquids don’t have variable volumes, so a tire filled with water would absorb no shock and be unable to comperss. Then, since water expands when it freezes, as it froze the pressure onthe tire would increase, eventually blowing up the tire.
An air filled tire is not changing in volume (ok, it does a little, but it’s an insignificant amount), it’s just being displaced. Water will still absorb shock, but it will be different as the water can’t be displaced as quickly as air.
Install a refrigeration device to cool the water in the tire to 39.2 degrees (waters highest density) once the wheel gets up to speed. That way you have changing weight without the problem of springs, shock absorption, or the expansion of freezing.
it would still absorb some shock because the tube is made of rubber, and is stretchable. when you hit a bump it would just stretch at the top of the wheel to absorb it.
but, as has already been said, it would take time for the watter to catch up with your wheel when you accelerate, meaning lots of friction. it would also keep going when you tried to stop, making it hard to stop.
I rode Florian’s 24*1.5, effective 36, today and compared to a Coker it has much less angular momentum (fly wheel effect). This is much better than having more. Turning and leaning both require changing direction and you get more giroscopic effect on the larger wheel. This didn’t seem to be a good thing.
What having all the geared uni’s next to eachother seemed to show even more was that to accelerate or slow down you have get your center of mass off center exactly the right amount and then try and move the wheel back under you. A heavier wheel makes it that much harder to get the wheel under you when you start to fall so it amplifies any bumps, wobbles or errors rather than helping absorb them like it would in a car (where you don’t have to worry about getting the wheels back under the car.)
A basic tenet of bike racing is that the best weight to get off the bike is rotational weight. For bikes, lighter is faster, and the best place to remove weight (as long as it doesn’t make things break) is from the wheels.
Adding more weight might make for a more comfortable ride, but would be unlikely to make for a faster ride, except possibly over very short (sprinting) distances.
Having a pair of weights that helped to compensate for the “wobble factor,” that which makes the wheel want to zig-zag left and right, might be a positive thing though. Helping the wheel go straighter might reduce some of the rider’s fatigue in high speed pedaling.
On the other hand, when I go fast on my Coker I don’t notice a wobbling problem. It’s there, but the heavy Coker wheel straightens itself out pretty well. If we ever get lighter Coker tires/wheels, we will see more wobble.
On Mon, 14 Feb 2005 12:09:42 -0600, “johnfoss” wrote:
>Adding more weight might make for a more comfortable ride, but would be
>unlikely to make for a faster ride, except possibly over very short
How would (more) weight help here? I would rather say that when
accelerating, weight holds you back. Conversely, once you are at
speed, weight wouldn’t matter (at least in an idealised world: no
acceleration/deceleration, no cornering, no bumps, no increased air
>Having a pair of weights that helped to compensate for the “wobble
>factor,” that which makes the wheel want to zig-zag left and right,
>might be a positive thing though. Helping the wheel go straighter might
>reduce some of the rider’s fatigue in high speed pedaling.
That, and also if it straightens out the path, the actual riding
distance from A to B is a little shorter.
Klaas Bil - Newsgroup Addict
people who unicycle are shyly exhibitionistic - GILD