Unisk8r Geared 36"

i dont thin that would be a problem dpending how the idler wheel was set up.

you could have it so that as well has pushing the belt into the teeth, it would also tension the belt in the same way as the idler wheels on a derallieur gear system

I think it would be a problem. The reason idler wheels work on bikes is that the chain is only being pulled in one direction. On a uni, the chain (or belt) would need to handle force in both directions. If the axles of the input and final drives didn’t move relative to each other, the tension of the belt would change dramatically and make the drive system all but unusable on a uni.

I’m not suggesting it would be spring operated like it is on a bike. I was just using as an example of a chain tensioner.

I was suggesting it the idler wheel could be held in place. It would need to be held in place anyway to push the belt into the ‘teeth’

It would be under a lot of force, but it would be anyway keeping the belt from being pushed out from in between the ‘teeth’

the way I am envisioning it, it wouldn’t be problem. buyt im not too good at explaining it…

That is one of the challenges in such a system. The belt must be relatively static (yet flexible enough to be deformed through the wave). This means, as you stated above, that the input and output pulleys will need to adjust relative to each other…

unless…

you use two idler wheels! As one idler wheel begins to deform the path of the belt on the input pulley it is beginning to dis-engage from the output pulley. This has two advantages:

  1. It prevents the need to vary the distance between input and output pulleys while maintaining belt tension in the system.

  2. It provides for a greater variation in gear ratio than deforming the belt path on only one side if the system.

Further it does not significantly complicate the design (which, by the way, is entirely theoretical at this point).

The only drawbacks are:

  • it would be a little heavier
  • it would require higher tolerances to obtain the precision required.
  • it makes my head hurt to think about it.

-mg

Yes that sounds good - and could probably be done with some sort of “see-saw” machanism so that as one end engages the other one is withdrawn the same amount.

It seems like you would need multiple “idler” gears around each main gear to be able to deform the belt enough to give a useful range of gear ratios though…

The see saw could be achieved by using a hydrulic tube thing that pushes the idler gears on pistons, sort of like how hydraulic brakes work, as one moves in, the other moves out. This would probably be the easyest way with good accuracy and reliability.

With the seesaw thing, I don’t think that the automatic transmission idea would work, because there would be pressure on both idlers at the same time. If it were possible, though, it would be interesting to try it on a uni.
Maby if the spring was adjusted just right, it would be a self-balancing uni - all you have to do is pedal at the exact same speed.
maby you could make a segway or motorised uni without all the gyro sensors and stuff.

Just one concern for using it on a uni. would’nt it pull more when tooth of the idler sprocket was first pulling the belt, then a sort of lag until the next sprocket grabbed the belt, then pull it faster, then lag, then pull it faster?

Sory if I dont make any sense.

Re: Unisk8r Geared 36"

On Thu, 9 Dec 2004 10:50:18 -0600, “mgrant” wrote:

>you use two idler wheels!

That’s a golden idea. I see one more advantage: it costs less net
force to change the gear ratio. You have to push one idler wheel in
for which you need force, but the other one is pushed out by the belt
yielding much of that force if the two are somehow connected.

Is the inventor / patent holder aware of this discussion? This is a
significant addition to the original concept.

Klaas Bil - Newsgroup Addict

“Deflating pi does not reduce calories, it just concentrates them. - billham”

I realise now that a selfbalancing uni would not work, because when more resistance is applied, it would slow the wheel down. UNLESS you put the Idler on the drive gear, defeating the purpose of automatic transmition in normal applications and working your legs/ motor harder.

Both are valid observations. I’ve considered them as I think about it and the attached rough drawing shows what I currently think is a potentially viable design.