Adding weight to a wheel

Unicycles and Equipment
21

Latest idea in wheel weighting

After some more riding, I have determined that adding weight to the wheel of a 36 commuter creates a useful fly wheel effect. There is a better way to do this then ankle weights, though less convenient for experimentation

Stick on lead wheel weights, available here…

http://patchboy.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=P&Product_Code=WR314-30&Category_Code=3-7

The amount of flywheel effect created by adding weight to a wheel is determined by only 3 factors.

1 The amount of weight added.

2 The distance from the center of the wheel.

3 The velocity of the weight.

The last 2 factors are of greatest relevance, because inertial energy increases with the square of velocity. Energy = mass x V 2

Eric should note that the ratio of weight added, to the original wheel weight, is not a factor. A basic understanding of the physics involved would show that a great deal more weight would need to be added to a light trials wheel, then to a heavy 36 wheel, to achieve a comparable flywheel effect. It is for this reason I expect all experiments adding weight to <36 wheels to be
fruitless.

I plan to see if I can add these weights to the inside of the rim. Because this location is a few inches further from the wheel center then is achievable with ankle weights, I will need a bit less then 3 lbs. to achieve the same effect as 4 lbs in spoke wrapped ankle weights.:slight_smile:

On my test rides, I noticed that I rode until I was tired on both the light and heavy setups. They both felt the same to me, I have determined that my testing cannot measure the difference in effort needed between them. It was to small to be noticeable to me. Actually, my ass gives out before my legs, unless I am riding muni.

WH-025.jpg

22

I’m surprised to have noticed the differences of just having a heavier tire.

The increased momentum several things were made easier: rolling over most bumps (also from the thicker, harder to deform sidewalls), maintain speed on flat, and climbing, provided I kept my speed above a certain amount.

It was harder to change speed, at speed I had to lean to turn, and climbing hills was harder if I didn’t keep my speed up.

There was a small period while going uphill, where the qyroscopic effect was neither good or bad, but the added weight to pull up the hill took a bit more work for me.

Overal I much preffer the lighter tire.

I was just about to mention stick on weights used in ballancing car and motorcycle wheels:)

23

I always thought my Coker wheels were heavy enough; they don’t need anything extra to have a strong flywheel effect. :slight_smile:

A heavier wheel can be great for cruising, control, and fitness training. It will not be good for racing. Common bike racing wisdom says that the best place to remove weight from your bike, if you can, is from the stuff that rotates. The further from the center the weight is removed (such as using a lighter rim), the less energy it will take you to do the same amount of riding.

That much is obvious enough. So I am tempted to try this on my Coker for RTL training…

24

Bikes aren’t the same

One of the 2 advantages to a larger flywheel, the other being gyro balance, is a mechanical flywheel effect. Energy is stored in the wheel, and released instantly as soon as anything tries to slow the wheel. So it takes more pedal energy to reach a speed, but then the energy comes back as soon as you skip a beat, minus < 1 % power loss to bearing friction.

Of course, bicycles would not be able to harness the fly wheel energy in their wheels, without giving up the ability to coast. In this way, the dual direction drive of the unicycle has an advantage, that allows wheel inertia to drive the uni forward , whereas a bike would go click click click. :slight_smile:

I did more riding today. About 7 miles with the 4 lb ankle weights, the about 5 miles without.

The biggest change I noticed was how little difference it made. The stock steel Radial 360 has an impressive amount of flywheel.

I wish I was a trickier rider. I can idle and go backwards on my 24, but I haven’t learned that yet on the 36. So all I can say is that I can do the same stuff on both wheels.

That said, I still prefer the heavier wheel. Riding into the strong gusty wind, the headlight bobs back and forth more with the light wheel. In general, the heavier wheel rides smoother and just wants to go straighter. It also seems possible to lean slightly more forward, but the difference is very small.

25

I’m tempted to try adding more weight to the 36" wheel just for swooping more on turns. This reminds me of an longstanding question as to whether a 24" wheeled guni’s can swoop when in the 36" equivalent gear mode. (I’ve asked about guni riders experience the forum, but have not seen an answer.)

I think the swooping turn is a result of the gyroscopic inertia counter balancing the lean of the rider falling to the side through the turn. Switching down from a 36" to a 24" ( 0.66 times smaller wheel) draws me down the path of thinking that the 24" wheel rotating mass (primarily rim/tire/tube weight) would need to to be 1/0.66 = 1.5 times more than the 36" wheel. But, this is canceled out by the 24" wheel turning 1.5 times faster to maintain the same speed through the turn as the larger wheel. So all that is left is that the per unit length of the rotating mass between the wheels, the 24" guni wheel needs to be about 0.66 of the 36" wheel. I expect that the wheels are close enough, and so a guni can do a swooping turn. (Not sure I have this correct.)

26

I must be wrong about the swooping between the uni and the guni, because that would say that any uni can swoop, it’s just a mater of getting up to speed. But 24" uni’s don’t bank, and I’ve tried banked turns on a 28", it’s just not the same as on on a 36". The 28" banked turn is quick maneuver, no real swooping experience.

27

sorry but I don’t get that, why does the drive have anything to do with it? the wheels do no need to turn the pedals in order to drive the bike or unicycle with their inertia, they exert a force to the frame through the axle. If two bikes are travelling at the same speed and one has higher inertia wheels it contains more energy, assuming everything else is constant it will coast further.

28

Wheel inertia on bikes still allows them to harness the energy in their wheels. It’s what keeps them rolling when you stop pedalling.

It is a factor, in that the relative change in power required is greater. For example if you add 2000g to a coker wheel, you’ve added something like 50% extra weight to the wheel, whereas if you add it to my 29er wheel, you’ve added approximately 110% extra. The relative amount of work you need to do to accelerate the wheels will change accordingly.

Also, as for not trying it on 29er wheels, I think you’ve probably not ever ridden a big apple, especially a geared up one, there really is a big flywheel effect on it.

What you really need to do for this to be convincing though, is rather than trying to justify it with slightly dubious physics, actually time some rides, and do some big rides on it. You maybe need to get more riding experience though, if your arse is tired before your legs, you’re never actually getting far enough to have a real idea of when your legs feel tired.

Joe

29

I have put a light 29er tube in my coker and noticed a big improvement over the heavy coker tube. I have since switched back to the coker tube for better reliability. I like the responsive feeling and quicker acceleration of the lighter wheel. I know what you are saying about the stability of the heavy wheel though and I think it would be great for flat land riding.

One thing you might try is filling your wheel with water. They do this on tractors for the weight and stability. you would need to take a filler hose off a bike pump. First suck all the air out of the tube, then fill the tire with water. Then it only takes a little bit of air to bring it up to the pressure you like. I dont know how much water a coker tube would hold but it would probably be about right. Just don’t leave it outside in the winter and let it freeze, but I guess that wouldn’t be a problem where you live.

30

do you mean tube?

31

A Coker tire would hold about 0.2 cu ft of water or about 13 pounds. Water is an incompressible fluid so a tire filled with water will not give a cushy ride. A tire filled partially with water will give some compressibility but a sloshy ride.

32

Yeah that would be a lot, probably heavier than you would want. You definitly wouldn’t want a tire half full either. It works on tractors but they probably only fill them part way full and at low working speeds the water would stay at the bottom where it would do the most good for stability.

Oh well

33

An article along similar lines of this thread, except about automobile wheels.

The table at the end of the article shows the lighter weight wheel results have improved gas mileage.

34

so the weights give the tyre more inertia?

35

this might be adaptible to muni also.

36

I’m not 100% sure what you mean by “swooping turn”, but I’m assuming from your desrcription below that you are referring to a wide-radius turn that you enter fast with only a little bit of bank and then you continuously add more bank (to the point where you feel like you could scoop something up off the ground when you’re at the greatest degree of bank).

For both those types of turns and the sharp, hard and fast turns (with a lot of bank) that I sometimes like to do to hook a 90 degree turn at an intersection, I much prefer the heavier wheel… as welll as for general riding.

One-foot extended is much easier with the heavier wheel and the stability allows me to do foot-plants and pirouettes (and other tricks) with confidence. Overall, it just makes it a lot easier and more fun for me to execute maneuvers and mess around. I could probably do most of the maneuvers with a lighter wheel, but it would require a lot more concentration and precision - which I’d rather put toward avoiding pedestrians, potholes, and cabbies here in NYC!

All that being said, I’m currently riding the lighter wheel because of it’s strength advantage. If there was a heavier rim available that was equally as strong as the airfoil, that’s the one I’d have.

37

Hey HardCoreCokerRider! Your the champ of those banked (swooping turns). It’s good to see your avatar.

38

The compressibility of water is a function of pressure and temperature. At 0 °C in the limit of zero pressure the compressibility is 5.1×10-5 bar−1. In the zero pressure limit the compressibility reaches a minimum of 4.4×10-5 bar−1 around 45 °C before increasing again with increasing temperature. As the pressure is increased the compressibility decreases, being 3.9×10-5 bar−1 at 0 °C and 1000 bar. The bulk modulus of water is 2.2×109 Pa.

The low compressibility of non-gases, and of water in particular, leads to them often being assumed as incompressible. The low compressibility of water means that even in the deep oceans at 4000 m depth, where pressures are 4×107 Pa, there is only a 1.8% decrease in volume.

Still that’s 1.8%

39

Sorry, Michael. Water is an incompressible fluid when compared to nitrogen, or air which are both about 1 per bar I think.

Good to hear from you again.

40

I sense a new edge here: Fill your coker tires with water, remove the brake, point 'er downslope, and let it rip! He who survives wins!