Adding weight to a wheel

Unicycles and Equipment
1

I used to think that weight was bad, and money was good, so that proper unicycle design would be a simple matter of striking a balance between the two.

Pedal weight is the worst, because it rotates out of balance. Crank weight is second worst, for the same reason, only less so, because it’s closer to the center.

Frame weight sucks, because it just pulls you down, but at least it just pulls down, and not down and to the side, like pedal- crank weight.

Certainly hub and rim- tire weight must be bad in many cases. Cranks spins and jumping would seem easier with a lighter wheel set.

But what about a 36 commuter ? I got this idea with these wrist weight straps someone left in my yard. They look like the picture. Together all 3 weighted 4 lbs. I strapped them around 3 spokes and tightened the Velcro, right at the rim. There was 9 spokes between each of the weights, to achieve balance. Installation time, 3 minutes. :slight_smile:

I have just came back from a 2 hr. ride. I fully expected this to be a bad idea, but it was free and easy, I couldn’t resist just seeing how bad it was.

Actually I like it ! It was very much like an unweighted wheel. I got used to the slower turning pretty quick.

There was some very real advantages. I could ride faster with less concentration. Hard pedal inputs have less effect. The uni tracks straighter. Balance, no doubt due to the gyro effect, was helpfully improved. I could easily ride with both hands on the saddle, something I never much tried before. It had the effect of transforming me into a smoother rider who could pedal harder and straighter with less effort, and better balance.

I’m not saying this is for everyone, but 36 riders, and maybe 29’ers might like to try this. I’m going to leave the weights on for now. I’d try more weight if I had them !

I guess I’ll go to more fat girl’s garage sales. :slight_smile:

51kG3+Q7XEL.SS500.jpg

2

I have thought about this but never tried it. I to relunctant i guess, but very good on the discovery! i think since someone tested it out i have a reason to try it. :slight_smile:

3

The Atlatl, unicycle connection: Bannerstones

4

here is a thread that I started on the topic last year, unfourtunately it quickly got off topic.

A heavy wheel can definately help your stability and smoothness but will be much harder to stop and slow down. It will also prevent you from easily making fine adjustments to prevent caristrophic falls at high speed…

It was fun untill my collarbone was where my shoulder blade shoud be.

5

“feel the light” I think you could be onto something good here,existing unis are definitely eccentrically weighted, as long as the additional weight doesn’t bring too many negatives it would smooth the wheels rotation.You only have to hold a uni up by the seat post and spin the wheel to see how out of balance they are.Todays crazy ideas for tommorrows improved unicycles.

6

I think pedal weight is not as bad as what you make it out to be. When the rider is on their pedals- the weight of their legs would be far more significant than the weight of the pedals- so regardless of how uneven the unicycle spins when you spin it in mid-air, it is going to be more uneven with a rider atop it. Fat riders should lose weight themselves before worrying about shopping for lightweight pedals.

Frame weight doesn’t really matter when you are riding unless you are hopping. Unless it is really heavy then it will drag you back on the hills. Frame weight does not pull you down unless you are already falling- the frame weight is balanced on top of the wheel if you are upright.

Maybe you should do a few long rides on an old steel coker with the heavy tires- you will soon notice how unnecessary any extra weight is for stability. I agree with Ken, lighter is better as long as it is strong enough.

7

As the wheel gets heavier, the pedalling corrections have less effect on the wheel. But someone once astutely remarked that every action has an equal but opposite reaction. So on a heavier wheel, the balance corrections are made by adjusting the body position relative to the wheel inertia, where the pedal correction force translates to a body adjustment rather than a wheel adjustment.

Does this make any sense to anyone else? Would the physicists out there be able to explain it better?

8

I’m not a physicist, but here’s what I’m thinking…

As far as forward motion is concerned, there are two methods that work together as you work to maintain balance over the wheel. The primary method for smaller wheel sizes is to pedal the unicycle such that the wheel is slightly ahead of your center of mass as you need to slow down, or slightly behind your center of mass as you speed up. The more the wheel is ahead or behind, the faster you slow down or speed up. However, to maintain balance at a steady speed, the wheel must swing forward and back constantly so that on average, your center of mass is directly over the wheel. This takes a fair amount of effort to maintain.

As the wheel gets larger, the inertia of the wheel (it’s resistance to an instantaneous change in speed) can also be used to an advantage. A larger, heavier wheel will have a greater resistance to changes in speed and will allow you to shift your center of mass more quickly and with less effort than the first method can. The inertia will allow your center of mass to remain more centered over the wheel, and so you will use less energy in maintaining balance.

I noticed this difference when I recently begain riding a Coker. I notice that I spend a lot of energy on my 29er keeping the wheel under me, and that it feels like it is constantly shifting forward and back as I ride. On a smooth path, the Coker feels like it stays in position better and with less effort. I think it is the wheel inertia that makes the difference. If this is the case, weights added to my 29er could cause similar improvement. Hmmmm…

-Aaron

9

I was pretty sure it was a bad idea

I want to emphasis that I only tried this because it was free and easy, not because I believed it would a useful mod. So I sorta expect others to be skeptical. I was surprised at the results.

Acceleration was about normal. I’m about 180, the uni was 17 lbs. before I added 4 lbs to the rim. So I figure the extra 2 % mass I need to accelerate is unnoticeable in practice. Anyway, it starts and stops about the same as before. I don’t have a brake.

I think that the most positive effect of the rim weights is due to 2 things. A gyroscope like effect that improves balance, and an "engine like " flywheel effect, that requires fewer good pedal strokes to keep it up to speed and aiming straight. The whole rig seems much more forgiving, like riding in a wagon. Corrections that would be needed on a lighter wheel aren’t needed. Hard kicks that would turn a lighter wheel to the side, move this one so little, that the natural tendency is to kick harder.

It wasn’t more tiring to ride. The extra friction caused by 2 % extra vehicle weight was made up by the lack of effort needed to control the thing. My general impression is that this rig is as safe and handles better then without the weights, particularly at high speeds in a straight line. It does have a way of making me pedal faster.

Anyway, these weights can be had for 12 $ / pr. of 5 lber’s. , that can be adjusted in 1/2 lb units. I used 3, but they aren’t adjustable.

I think I will leave them on for now. Maybe buy the deluxe set of adjustables later.

If I really get into the heavy 36 rim concept, I have a better design. I’ll use 3 inner tubes. One will have no stem and be slit all around the inside. This one can be installed into the tire first, with a bit of rubber cement to hold it in place.

I’ll drill a stem hole in the rim 180 degrees opposite of the first one, then install and inflate 2 tubes. This has 2 advantages. The flywheel weight is placed farther from the wheel center, then with spoke wraps. And an edge against punctures. Most punctures would only get one tube, so the tire would only lose 1/2 pressure, and could be pumped back up without first needing to fix the flat.

10

I disagree that it wasn’t more tiring to ride. Did you actually do a long ride or just a regular ride? If you do 100km on a big heavy wheel you will notice the difference than riding 100km on a lightweight wheel. Turning a 700c wheel for a long time produces a lot of saddle soreness but very little muscle soreness because it doesn’t take much work to keep it moving. The heavy Coker wheel is definitely harder to ride. It covers the k’s a bit quicker but you feel the weight on the uphills. I think effort for controlling a wheel is minimal for skilled riders compared to the effort of cranking up hills at speed. I am looking forwards to trying a geared 700c to get some speed without the burden of the weight.

11

I want to lighten my Coker rim (which is absolute heavy crap). How so? because every time I do movements to correct my balance the inertia of it all hurt my Achill’es tendons. (for sure I Coker only off road). So I want a lighter rim/tire!

now for smooth road riding some inertia has appeal: how about a small weight that could slide along some special spoke (not crossing another)? when going slowly the weight will be near the center (need some spring fixed to the hub too) and as you go faster the weight will go outwards and produce its effect?

12

Personally I think you’re wrong on this one, having ridden a variety of wheel sizes and weights recently.

I’ve recently done the reverse on my schlumpf, lost 400g off the tyre & tube. I think it makes a big difference in feel to lose wheel weight, and losing weight on the wheel is a definite advantage.

The heavier wheel does feel at first like it’s less effort to ride in a straight line for the reasons you mention, but over a ride, it makes you tired more quickly, and you tend to go slower. I time my commute, and it seems pretty likely from the data that the lighter wheel is faster - all my commutes have been very close to or better than my previous best time (although I’m not ruling out the influence of it being a shiny new toy until I’ve ridden it for more than a week).

On the flat, I think lighter wheels take a little bit more skill to control, but once you’ve developed that level of skill, they are faster and less effort. Uphill, it still makes a difference, although I’m not sure it’s as much.

In terms of what is the worst kind of weight, typically it’s thought that tyre and rim weight are worst, because they are rotating furthest out from the centre of the wheel.

If you want to get the feel that it is harder to turn, but less input is needed to go in a straight line, without weight disadvantages you might be able to get something similar just by changing down a crank size.

One other piece of evidence against the heavier = better theory, is that I know both the last two 24 hour record holders are obsessive lightweight weenies, same for the hour record holders I know of.

Joe

13

my observations

I have to agree with you on this, to a point. When I was first experimenting with weighed wheels I was fairly new to unicycling and my technique sucked. The heavy wheel was much more forgiving and allowed me to spend less energy keeping the thing balanced. Therefore I have to agree with you that in some circumstances a heavy wheel takes less effort. Swooping turns were also really fun with the heavy wheel.

After spending some time with the heavy wheel my technique improved. I removed half the weight from the wheel and found the lighter wheel was much more responsive, I was able to make sharper more precise turns (like following meltwater channels in the streets)

As for making you pedal faster this can be good and it can also be really bad. On May 11th last year I was riding to school to write a Final exam and I was running a bit late. I was pedaling as fast as I could while maintaining some semblance of safety. I did not have a speedometer but I estimate I was going about 22km/h. I hit a small patch of gravel and started pitching forward. I tried pedaling faster to catch up with myself but I just managed to accelerate until I was going so fast that my foot just came off my plastic pedal (the kind you like so much). There was a car slightly behind me when I hit the pavement and they stopped to see if I was OK, I told them I was fine not realizing that my shoulder was half a foot below where it was supposed to be and I asked how fast I was going, they said “at least thirty”. So yup, it can make you go faster by making to take longer to correct fore-aft balance issues. 30km/h on a 27" wheel is pretty freaking fast.

This fall I got back on the same wheel just to see how it compared to the 36er that I had been riding. It felt similar in acceleration/deceleration but the skinny tire felt really harsh. I removed the weights to see what a it would feel like and it was really flicky and took very little effort to ride, less effort than with the weights. I recently took the wheel apart to use the hub for a freestyle unicycle I built up.

I tried putting weights on a trials wheel and I found no gains and it just made jumping way harder.

In conclusion I think that a heavy wheel can really help people that are still learning or still have poor technique. The effect is much more noticeable on larger wheels and it might make learning on a 29er more manageable. That being said I don’t think that anyone with good technique would ever voluntarily add weight to their wheel. Once you are comfortable riding and no longer spend energy keeping balanced you can go faster have more control and spend less energy with a lighter wheel.

I would suggest fishing weights clamped on the spokes over ankle weights. It takes a bit more time to put them on and off and they will probably be wrecked after you remove them but they would not be able to move around on the spokes. I would be concerned with ankle weights shifting especially at low speeds. And you can get them to within a cm of the rim.

Good to see other people have curiosity and experiment

-ERIC

edit: all my weighted wheel experimenting was done on a 27x1 1/4" road wheel except the brief experiment with a trials wheel. I believe that I was using 102mm cranks for the whole time on the 27 but I might of started with 127s, I can’t remember.

14

MO-MENT-UM. I would say this is a great idea for just cruising around town not going very fast, good for a 24 or 26 inch uni.

15

I’ve been thinking about making heavier rims for a bike, but it would work far better on a uni. It should help long straight and smooth stuff and hurt quick agile moves, as everyone else has explained. I would imagine that it also helps get over small bumps that could eat momentum otherwise, and it would make 1-foot easier.

16

The long lever effect

A one lb. weight attached to the rim of a 36 will be about 16 " from the center of the hub. Attached to a 29 rim, about 12 inches or so.

So I think it would require 4 ish lbs. of weight added to the rim of a 28, with both rims turning at the same speed, to put the same “fly wheel torque” into the hub as 3 lbs would on the rim of a 36. More or less. Basically, the weight on the rim of the 36 is working on the hub through a longer lever, thus more torque.

So I am of the opinion that wheel weighting may be of value only on 36’s. It would be easy enough to check, but I don’t have a 29. I appreciate Eric’s input, but I am not sure his experiment adding 3/4 lb to the rim of a 29’er yielded enough of the "gyro - fly wheel effect, for him to notice.

Hopefully some 36 riders will become curious enough to pick up some ankle wrap weights and try it themselves. You just wrap them tightly around 3 spokes, tighten the strap and fasten the velcro. On or off in seconds. I have had no trouble with them coming loose, and they are soft and padded.:slight_smile:

17

You can definitely notice a change in the “gyro - fly wheel effect” when adding 3/4 lb to a 27" wheel. Remember that even a light 36er setup will have over 6 lbs in the rim-tube-tire alone where my 27" wheel was only about 1 lb in the rim-tube-tire. The rim is also a slightly taller loop than a 29er. (deceiving I know)

I noticed 3/4 of a lb on a 1 lb wheel just as much as I am sure you noticed 4 lb on a 7 lb wheel.

A beefy 29er wheel is probably double the weight of a skinny 27" wheel so you might need twice as much weight as I did to feel the same difference.

18

I am sure that the flywheel effect is much more pronounced with a larger wheel. Perhaps wheel wights may be worth using on a 29, but I am sure they would not work as well as on a 36.

19

There’s something I particularly like about this quote. It’s like someone telling you that you don’t actually like pizza, you just think you do. Or, you’re not really cold, you just think you are.

It is entirely possible that it is not only easier, but much easier, for some riders to use a weighted wheel under some conditions. It has to require less energy to make corrections on a stable wheel than a really twitchy one. It takes a certain amount of energy to move the weight of the unicycle over a distance. It takes a varying amount of energy to deal with the instabilities of the unicycle over this same distance. This varying amount of energy depends on the skill level of the rider, the conditions of the road, the irregularity of the surface fluctuations, the total vertical climb, the steepness of the hills, and any number of other factors.

There are good and sound reasons to explore this effect. I’m glad there are a couple of people committing time to this and trying to quantify the results. That’s what would be most difficult in tests like these.

20

I think you should try and sell the idea to mountain climbers. Heavier gear for more stability. Give them a doorstop and tell them it will anchor them to the mountain. Maybe you could even borrow yourself a pole from the tight-rope walkers and improve your balance by having weights at each end, and it could be used for unicycle-jousting.