Interesting Video Explaining The World's First, Geared, Continuously Variable Transmission.

[Eddyde]

Found this on YouTube, or maybe it found me... Anyway, I think it's pretty interesting.

 

[400bird]

I watched that! It doesn't look overly robust. All the torque is transfer through each gear/lever pair one at time.

Amazing and impre engineering!
Personally, I'd need the reliability proven.

 

[RandyWilson]

Being in the automotive powertrain business, that video has been shoved at me non-stop. All I can say is a lot of complexity for no real gain. The example is for a bicycle. Scale it up for automotive use and even a Van Doorne belt starts looking good.

 

[Eddyde]

I watched that! It doesn't look overly robust. All the torque is transfer through each gear/lever pair one at time.

Amazing and impre engineering!
Personally, I'd need the reliability proven.

Isn't the torque of any transmission transferred through only one gear at a time?
Well it is only a prototype so yeah, lots of testing/proving needs to be done.

 

[Eddyde]

Being in the automotive powertrain business, that video has been shoved at me non-stop. All I can say is a lot of complexity for no real gain. The example is for a bicycle. Scale it up for automotive use and even a Van Doorne belt starts looking good.

Apparently the gain could be an increase in efficiency. Also since it can start from zero rpm it could eliminate the need for a clutch or torque converter.

 

[MikeWi]

Not only is it a single gear, but thru an arm that doesn't look too robust even if scaled up, and more importantly to me, it relies on a one-way bearing. How long is that bearing going to last under any load heavier than a bicycle?

 

[Eddyde]

Not only is it a single gear, but thru an arm that doesn't look too robust even if scaled up, and more importantly to me, it relies on a one-way bearing. How long is that bearing going to last under any load heavier than a bicycle?

I don't think it relies on the one way bearing. The video said it was there because the prototype was for a bicycle and needed the one way feature to prevent the pedals from turning, while coasting.

 

[RJSakowski]

Not only is it a single gear, but thru an arm that doesn't look too robust even if scaled up, and more importantly to me, it relies on a one-way bearing. How long is that bearing going to last under any load heavier than a bicycle?

Torque in an ICE is transmitted one crank at a time. The one way bearing aka sprag has been around for a very long time and is commonly found in automatic transmissions.

edit: From what I understood, the sprag was use in the bike transmission to allow the pedals to free wheel. It wouldn't be necessary in an automotive application and would in fact, prevent engine braking.

An interesting idea. Any concept can be scaled up to address increased power needs. Increasing power transmission efficiency by 10% is a laudable cause.

 

[brino]

Was discussing this with a gear-head here at work.

He mentioned the Prius CVT being much like the old "three-speed hub" planetary gear system used in old bicycle rear axles. The kind where you lock one component at a time to achieve three different speeds, except instead of locking you rotate one component with a low-power motor to give the continuously variable features.

He knows a lot more about these things than me, so I guess I gotta go look up the Prius CVT now.......

Brian

 

[RaisedByWolves]

Not only is it a single gear, but thru an arm that doesn't look too robust even if scaled up, and more importantly to me, it relies on a one-way bearing. How long is that bearing going to last under any load heavier than a bicycle?

How big is the bearing?

Sprag clutches have been used in automatic transmissions since the 50s, with even some early designs capable of handling thousands of HP.

It is stated in the video that that design uses ratcheting elements, and the arms shown are meant for "Bicycle" use, and could take any shape needed.

The main benefit is very low frictional losses.