IDEA: 2 Speed Roller Drive

JennyB

JennyB

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Jan 25, 2008
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Northern Ireland
:idea: Inspired by Miles and Kepler:

RC motor ala Kepler drives a smaller roller on a parallel axis via a pair of 1:1 spur gears. Mounted on a mechanism such that (big hand wave) on power up the roller drives the tyre, and once up to speed the direction of the motor is reversed, the roller is kicked out and the motor comes into contact to drive the tyre directly.

Possible?
Practical?
Useful?
:?:
 
That is very clever. :) I like the idea, and I like how it lends itself towards being mechanically passive for switching operation.
 
It would be nice to isolate the additional roller and the gears with a one-way bearing on the motor shaft but that would make the changeover more complicated.
 
Nice. We are looking in same direction. I had idea to use one speed from hub gears but to attach it to rc motor axle. So the fixed axle from hub gear will be input axle and sprocket become fix.
 
HAL9000v2.0 said:
Nice. We are looking in same direction. I had idea to use one speed from hub gears but to attach it to rc motor axle. So the fixed axle from hub gear will be input axle and sprocket become fix.
Click to expand...
I was thinking of something like the Hidden Power, with twin arm support and hub gear roller.

P1060473.JPG
 
Why stop at one. Much better to balance the forces with two :D

On a full-suspension bike no less.

http://pedalix.com/impressions/storck/


[Edit] fixed image link.
 
Pondering the Kepler and Todd-drives, I have considered making a two-speed. I am certain it would reduce amp-draw and make ESCs more survivable and abuse-tolerant. I have not finished my own friction-drive yet, so its a year away before I experiment with other odd ideas I have (if I actually try any of them at all!).

Perhaps a rocking arm with a 1" to 1-1/2" roller for first gear, driven by a toothed HTD belt. And the RC-Motor shell is the second gear, just like Keplers build? (edit: after re-reading the first post, other than me using a toothed belt rather than a spur-gear, you had this idea first, Jenny. Great suggestion!)

I am still interested in Storms suggestion about a cone as a CVT...

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A larger drive roller means higher speeds, or slower motor rpms for the same speed. I put together a table to show rpms for speed with different size rollers. It's at the bottom of pg 2 on the "resources" thread: http://endless-sphere.com/forums/viewtopic.php?f=28&t=7192&start=15 - jd
 
How about a tapered roller and making it slidable as the motor slides in and out the ratio changes?
 
I think that's basicly how Storm's cone roller works, that seems like an excellent idea to me, only one question, I bet Miles could answer this one: Will the cone and the tire be spinning in the same direction radially? Meaning, as the roller moves "down" to larger diameter, would you need some sort of pivoting action to make sure the roller and tire are parallel? It can't just slide across the tire and be the same surface friction through the range can it? If so that's the best solution I've seen and I'm stealing it! :twisted: Thanks Storm! :lol:

But seriously, Jenny that is a great idea, way better than any brainstorming I could come up with so far. I bet you could make it to only add a kg. Anybody care to photochop the rig on a Kepler drive for kicks?
 
Here is another idea ..
similar to Storms cone roller, but make the "roller" a sphere, ... or actually a 1/2 sphere... and then you can pivot the motor about the center of the sphere to alter the effective drive diameter . It May be easier to engineer a pivot than a sliding mount. ..( Hah ! the EVTodd vs Kepler design principles again ! :D )
 
Hillhater said:
Here is another idea ..
similar to Storms cone roller, but make the "roller" a sphere
Click to expand...

You beat me to it, I was going to suggest the same thing! :) It wouldn't even need to be a half-sphere, just a circular surface-of-revolution with the pivot point at the center of radius. (I tried looking on Wikipedia for a better way to describe the shape but struck out) That would keep the roller and tire parallel as it pivots and also keep the distance and pressure constant.

I was trying to think if there would be a way for this to be self-adjusting... If you angled the roller very slightly there would be a sideways force proportional to the torque, and with a spring return the roller would move according to the torque applied. But, I don't know if this would produce the desired result... that's why I'm an EE not an ME. :) Using a separate servo to control electronically might be necessary. The control for that should be very simple, though, just use a control loop which tried to keep the motor at the most efficient speed. You could make it a little more complex by using the throttle input to adjust the setpoint a little bit - so, like in a car, if you punch the throttle it'll downshift for more power.

I think I want to make myself one! :-D
 
I'm not sure if I understand the last couple of posts, so I apologise if I am repeating the same idea in a different way (the method my boss uses where he suddenly "has a good idea"), but...

I don't know if a simple angled cone would have some odd tracking characteristics or not (Miles?), but I have an Idea for idea fixing that, which led me to an interesting additional idea. (clearly triggered by Hillhaters use of the word 'sphere')

Stealing a concept from NuVinci, two balls (or perhaps half-spheres, rounded portions towards the tire) that start out farther apart, with the smaller diameters rubbing against the tires (at a point away from the center of the tire). That would be low gear, and as I am using a 1/2" shaft, it would not be unreasonable to allow a usefully-small 3/4" steel sleeve as the core of the mechanism.

As you accelerate, the two half-spheres are drawn to the center to raise the ratio. All loads would seem to be balanced, plus the drive rollers are self-centering. It might even spread out the additional wear applied to the tire from a friction-drive. (although...it also 'might' require that the two half-spheres be mounted on two separate but parallel shafts, one motor, shafts connected on the other side by an HTD belt? OR...two separate shafts and cone/sphere-rollers, but only ONE of the shafts is powered, with the two rollers drawn to the center by an interconnecting lever?)

This thought led me back to my steam-engine studies from years ago. Spring-loaded centrifugal weights 'could' be used to auto-shift the gears? which would also auto-return to low gear as you slow?
 
spinningmagnets said:
I don't know if a simple angled cone would have some odd tracking characteristics or not (Miles?), but an I have for idea fixing that, led me to an interesting additional idea.
Click to expand...
I think it might be problematic. Best to have a symmetric roller or mirrored rollers.
 
A picture is worth a thousand words:



Apologies for the terrible drawing, but MS Paint is all I have handy at the moment. The pivot point is centered above the tire and the contour of the roller is defined by an arc from the pivot point. This way the roller surface is a constant distance from the tire as it pivots back and forth. The axis of the roller ends up canted so it's not parallel to the bike axle. I think that so long as the wheel axle, roller axle, and pivot point are all co-planar, then the forces will all be in-line. That is, I don't think the roller will scrub sideways on the tire and I don't think there will be any sideways torque against the pivot point. I think...

Not drawn, but presumably the motor would be mounted directly above the roller with a belt drive. An RC servo or something similar could be used with a lever arm to actuate the pivoting motion.

P.S. Miles, I'm now embarrassed to post my picture after yours. :-(
 
rhitee05, very clever idea! no reason it couldn't be either belted or direct-drive for a motor attachment...

Miles, I really like you computer drawing skills! and the inter-woven fingers are also brilliant (for avoiding double-shafts)...I would gladly PayPal you the price of a delicious and refreshing cup of coffee from your chosen vendor, if you would draw Jenny's first-post idea? (small roller for first gear, motor shell as second ala Kepler?)
 
spinningmagnets said:
I would gladly PayPal you the price of a delicious and refreshing cup of coffee from your chosen vendor, if you would draw Jenny's first-post idea? (small roller for first gear, motor shell as second ala Kepler?)
Click to expand...
I'm still thinking about this one. I can certainly model it when the specifics of the linkage are clearer.
 
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