Heavy rims

[Woofie]

I have been wondering for some time now about how a heavy rim would work on a very flat course instead of using a light one.

Surely the heavier one will carry more momentum?

 

For instance on a TT bike where the profile is very flat. Wouldnt it be of an advantage then?

 

Have any of you DIY guys every made a deep section rim your self out of an old rim and carbon fibre or fibre glass?

 

How funny would that be, rocking up at a TT race with a old lejuene with the down tube shifters moved to the TT bars and your homemade deep sections that used to be alex rims.

Funny enough, I think it would actually work as well and if the course is flat I think you could have some fun.

I actually have a old lejeune that is lying in my friends wendy house......

Do you think that is a worthwhile project?

 

 

 

[Guest Agteros]

Just make sure the wheels are balanced!

 

Like some poor purchaser on the hub found out, you can attach lead weights to your bicycle disk wheels to balance them

 

Don't know who'll be able to help with the balancing... Maybe Tiger Wheel & Tyre?

 

[mountain_lion]

If you want more mass for more momentum, you can add it anywhere on the bike. (a rolling wheel is not a flywheel).

 

Unfortunately, it will not make you faster over all.

Although you decelerate slower, you will also accelerate slower...

 

 

[Woofie]

Why wouldnt a heavy wheel be like a flywheel?

 

ya, maybe tiger would be able to balance it out.

It would be a massive problem at 70KM/h if the wheel was very unbalanced

 

Sure it would take much longer to accelerate. but in TT you dont need to accelerate fast you just need to be able to keep a very high constant speed.

 

Would a heavier bike be harder to use in a TT?

Surely not?

 

I actually saw a pic on the hub a few days ago of a old school track bike with deeeep section wooden rims. Flip, they looked really awesome.

Surely those must weigh a half a ton? They must surely act like two flywheels?

 

 

 

[Matchstix]

 

If you want more mass for more momentum' date=' you can add it anywhere on the bike. (a rolling wheel is not a flywheel).

 

Unfortunately, it will not make you faster over all.

Although you decelerate slower, you will also accelerate slower...

 

 

[/quote']

 

But will a heavier wheel not have the same effect as a flywheel?

to get it up to speed to takes a bit more energy but to keep it there a little less?

wonder what JB's conclusion will be

 

[techguy]

Any rotating mass acts as a flywheel...thats why the older disc wheels weren't  so popular for the amature cyclists as the rotating mass would be a hinderance below a certain speed...

[bikemonster]

The heavier rims would indeed act as a flywheel.

 

Time to accelerate not a prob?  We both ride a 40km TT at an a steady max speed of 40 km/h.  (As if I could!)

 

With my super-light, wispy wheels I accelerate to 40km/h in 90 seconds.

 

With your hefty, slower accelerating wheels, you accelerate to 40km in 120 seconds.

 

I win!

 

While there is some advantage to sacrificing lightness for aero, there is never any advantage to adding weight for its own sake.

 

James

[Woofie]

 

Any rotating mass acts as a flywheel...thats why the older disc wheels weren't  so popular for the amature cyclists as the rotating mass would be a hinderance below a certain speed...

 

Exactly. But if you are a strong cyclist the rims would probably give you awesome stability at speed.

 

Lets think out of the box here, really extreme.

What if you had to go really overboard and create a solid back disk out of concrete. Cast it over some old rims so you have a straight rim to work with and some steel inside to hold it together.

Yes, it would weigh 10+ kg, but and it would take a few minutes to get to cruising speed, but just imagine the momentum you would carry!

You may have to fix a disk brake onto there to be able to slow you down though.

 

 

 

[Woofie]

 

The heavier rims would indeed act as a flywheel.

 

Time to accelerate not a prob?  We both ride a 40km TT at an a steady max speed of 40 km/h.  (As if I could!)

 

With my super-light' date=' wispy wheels I accelerate to 40km/h in 90 seconds.

 

With your hefty, slower accelerating wheels, you accelerate to 40km in 120 seconds.

 

I win!

 

While there is some advantage to sacrificing lightness for aero, there is never any advantage to adding weight for its own sake.

 

James

[/quote']

 

Good point.

The heavier wheels will not have any advantage on a flat road then.

However, if there was a very short roller how long do you think it would carry you up there for if you were going very fast?

And obviously the heavier wheels would be a huge advantage on the downhill as well.

 

 

[bikemonster]

...it would weigh 10+ kg' date=' but and it would take a few minutes to get to cruising speed....
[/quote']

 

There's your problem, right there!

 

And persuading that "bad boy" to change direction might also get kinda fascinating.

 

There are some odd designs that come out of the bike industry from time to time (Rotor cranks, anyone?) but if nobody is doing something that is simple to conceptualise, there's generally a good reason.

 

Next up: Wouldn't square wheels work to smooth really rocky trails for mountain bikers?

 

[Woofie]

 

Rotor cranks

 

[parabola]

Its a compound problem. It depends on the riders performance as well as the course. Flywheels in a car even out the power delivery and are selected based on both motor performance as well as the course. So it would depend on how smoothly the rider can pedal. A heavier wheel may actually help a rider with uneven pedalling force  for example.

 

If the course was entirely flat I dont think the obvious answer would be 'as light as possible' but rather there would be a wheel weight/design which allows for peak performance.

 

I'm just speculating based on the physics, I've never even ridden a road bike for that matter, so take this with a pinch of salt.

 

[bikemonster]

Rotor cranks

 

A similar idea to Shimano Bio-Pace, which used an ovoid (egg-shaped) chainring to try and eliminate "dead spots" in the pedal stroke.

[Woofie]

 

Its a compound problem. It depends on the riders performance as well as the course. Flywheels in a car even out the power delivery and are selected based on both motor performance as well as the course. So it would depend on how smoothly the rider can pedal. A heavier wheel may actually help a rider with uneven pedalling force  for example.

 

If the course was entirely flat I dont think the obvious answer would be 'as light as possible' but rather there would be a wheel weight/design which allows for peak performance.

 

I'm just speculating based on the physics' date=' I've never even ridden a road bike for that matter, so take this with a pinch of salt.

 

[/quote']

I think you are onto something here.

I have heard that some "suuped up" cars get lighter flywheels which allows them to accelerate faster, but then as soon as they hit a hill they end up slowing down faster than normal.

 

This is where we need mythbusters to do the tests for us.

 

 

 

[Guest Agteros]

 

 

Any rotating mass acts as a flywheel...thats why the older disc wheels weren't  so popular for the amature cyclists as the rotating mass would be a hinderance below a certain speed...

 

Exactly. But if you are a strong cyclist the rims would probably give you awesome stability at speed.

 

Lets think out of the box here' date=' really extreme.

What if you had to go really overboard and create a solid back disk out of concrete. Cast it over some old rims so you have a straight rim to work with and some steel inside to hold it together.

Yes, it would weigh 10+ kg, but and it would take a few minutes to get to cruising speed, but just imagine the momentum you would carry!

You may have to fix a disk brake onto there to be able to slow you down though.

[/quote']

 

Is one area of the wheel not constantly decelerating, while the other is accelerating?

In that case rather give a me a lighter wheel, or one that cuts drag more than what the added weight 'cost'

 

Which wheel would you want to roll on the out leg of the half ironman (+- 500m ascent), a heavy earo/disk one, or a light earo/disk one?

Agteros2009-11-26 09:37:43

[mountain_lion]

 

 

 

Is one area of the wheel not constantly decelerating' date=' while the other is accelerating?

[/quote']

 

At last someone who is talking sense.

 

The bottom of a rolling wheel (contact patch) is stationary relative to the surface it is rolling on. We know this is true, else the wheel will be sliding along rather than rolling.

The top of the wheel is moving faster than the rest of the bike relative to the ground and the centre of the wheel is moving at the same speed as the rest of the bike. From this we know that all points on a rolling wheel except the centre is constantly accelerating and decelerating relative to the ground.

 

When adding or reducing weight on a bicycle, it does not matter if you do it on the wheels or on any other place on the bike. The effect is the same on acceleration and deceleration.