Shaft Drive

[Dogtrousers]

Shaft drive is one of those things that gets periodically reinvented, like expanding chainrings, and continuously variable transmission.

Here's a new take on it, and leaving aside all considerations of practicability, marketability, and whether or not it's an improvement on chain drive, you have to admit that it's a lovely piece of engineering. It really does look nice.

Warning: This is a GCN video. Some people who are allergic to excessive enthusiasm may prefer not to watch, as they may find their wick got upon somewhat. It's the first item in the video, so you don't have to put up with too much wittering.

 

[dhd.evans]

I saw a sneak-peak type video of this some weeks ago and i must say i'm very impressed. No chain drop or clinking/clunking as you shift gears? Uh, yes please.

Also the rest of the video led me down the rabbit hole of "Do i need a 13 speed cassette on my good bike? Hmmm... how much is that..." aaaaaaaaaaaand now i have a bad case of the N+1s.

 

[Drago]

It's a pith poor piece of engineering. Just about every 2 wheeled shaft propelled vehicle uses the shaft tunnel/torque tube as a structural member, both saving weight and adding rigidity. Not only that, most of the gear train is exposed to the elements where it will attract dirt and crud, which utterly negates the main benefits of shaft drive at a stroke, ie, low maintenance, low wear, long lasting and durable transmissions. Even the typical GCN sycophancy can't mask the glaring errors with the design.

 

[Oldfentiger]

I have my doubts about the shaft drive concept.
In non-engineering speak, the roller bearing gear on the drive shaft and the cassette will create a load which will try to force the two apart.
I cannot see the "cassette" having the structural integrity to resist this load.
We have to consider worst case scenario. Think 18st fit rider standing on pedals, sprinting up a short steep incline. 1500W maybe?
I'd be delighted to be proved wrong, because it's innovative thinking.

Edit:
Ah I see @Drago is thinking the same.

 

[Bazzer]

Perhaps one of the engineers on here could explain why the "chain ring" doesn't have a spiral bevel gear. I thought these were more efficient and spread the load more? - Genuinly interested.

 

[Bazzer]

Perhaps one of the engineers on here could explain why the "chain ring" doesn't have a spiral bevel gear. I thought these were more efficient and spread the load more? - Genuinly interested.

 

[Bazzer]

Perhaps one of the engineers on here could explain why the "chain ring" doesn't have a spiral bevel gear. I thought these were more efficient and spread the load more? - Genuinly interested.

 

[loopybike]

I had an itch to build something around a shaft drive for years. I've been waiting for the right one. It will have to have "the look" or be totally hidden within the frame. It will also have to be efficient.
This isn't "the one" due to what @Drago says.

One day though .......

 

[loopybike]

Perhaps one of the engineers on here could explain why the "chain ring" doesn't have a spiral bevel gear. I thought these were more efficient and spread the load more? - Genuinly interested.

I don't think there is an engineering reason. The point of pressure on this design is very small. I suspect this was designed for looks. I would be concerned about it jumping out when powering up a hill...... Who am I kidding, I don't "power" up hills lol

 

[Bazzer]

I don't think there is an engineering reason. The point of pressure on this design is very small. I suspect this was designed for looks. I would be concerned about it jumping out when powering up a hill...... Who am I kidding, I don't "power" up hills lol

Thank you.

 

[Oldfentiger]

Perhaps one of the engineers on here could explain why the "chain ring" doesn't have a spiral bevel gear. I thought these were more efficient and spread the load more? - Genuinly interested.

With any 90 degree gear drive, whether they be straight, helical or spiral, the gear teeth need to be tapered or it would be impossible for them to mesh.
It is this taper which creates a load which forces the gears apart. This is usually contained by using appropriate size bearings contained within a suitable housing.

 

[BromptonChrispy]

Why not judge it on it's performance? It looks beautiful and its bound to be well engineered.
Will it wear quicker than a chain? I've snapped a couple of chains in my time (my poor maintenance probably) but have been able to do a roadside fix.

 

[Pale Rider]

There a shaft drive kit similar to the one in Newtie's pic called a Sussex.

It's been around a while, although has never really caught on.

http://www.chainlessbike.com.cn/index_en.html

 

[Globalti]

Great in dry California or Europe but get some British mud on those pinions and they will grind themselves away in very short time.

But the major shortcoming of shaft drive is that you lose 15% of the energy with each 90 degree change of direction. In a conventional car or motorbike with a longitudinal crankshaft that's bearable but the most efficient arrangement is crankshaft and axle parallel and connected by meshed gears or chain-linked gears as on a bike or a transverse-engined car or motorbike.

 

[Tim Hall]

The one pictured is a concept/prototype. It doesn't have gear changing (yet).

Here's another video about it:

(I think this was posted a few weeks ago on Cycle Chat)