Shaft driven bike

[mickle]

Shaft drives have their uses if you are happy to put up with the extra transmission drag, weight and to buy into a technology which is alien to 99.99% of bicycle mechanics. They're clean, don't rust like chains can and won't destroy your flares.

Many cars used chains in the olden days. Nash were the last IIRC. For vehicles with lots of power - cars and motorbikes - the transmission losses of a shaft drive and bevelled gears aren't worth worrying about. It's only because humans are such piddly little power sources that it's an issue for us.

 

[mickle]

I think the losses on older designs were more a factor of materials and the limits of manufacturing tolerances. This new one may very well be much better.

In terms of efficiency one shaft drive is very much the same as the next, and in that respect nothing significant has happened to shaft drive for 100 years. Not one can come close to the famous efficiency of a bicycle chain and pair of sprockets.

 

[benb]

If the teeth intermesh closely enough to prevent loss you then get the problem of friction - which brings you back to loss again

If the teeth intermesh losely enough to remove the initial friction...well you are looking at loss again.

Some early cars were chain driven, but then the differential came along, car engines produce far more torque so can overcome the initial friction of shaft drive.

The losses are in the two right angled crown & bevel geared turns in the drive from pedal rotation to shaft rotation and from shaft rotation to rear hub rotation.

The other problem they have is shaft wind up under load which makes the pedals feel soggy.

Yeah, that makes sense, thanks.

I think the losses on older designs were more a factor of materials and the limits of manufacturing tolerances. This new one may very well be much better.

The article was certainly positive, although it did mention the extra weight as a problem. I really like the clean look you get with it, and I'd be really interested in test riding one.

 

[Riding in Circles]

In terms of efficiency one shaft drive is very much the same as the next, and in that respect nothing significant has happened to shaft drive for 100 years. Not one can come close to the famous efficiency of a bicycle chain and pair of sprockets.

I don't think that is true.

 

[Zoiders]

I think the losses on older designs were more a factor of materials and the limits of manufacturing tolerances. This new one may very well be much better.

Manufacturing tolerances are the problem.

If it runs tightly enough to remove as much loss as possible then you as a puny human don't kick out enough watts to overcome the initial friction.

Start up requirement is always greater, so it's makes for a pants town bike that is stopping and starting all the time.

 

[mickle]

I don't think that is true.

Which bit?

 

[Zoiders]

Chain drive with a new chain/rings/sprockets has been shown to be something like 98% efficient IIRC.

That's hard to beat, to get any better we will have to wait for room temperature super conductives to come along.

 

[fenlandpsychocyclist]

The final drive units on many powerful rear wheel drive cars have cooling fins, purely required to
get rid of frictional heat from the meshing gears.
(Yes i know a differential has more moving parts than this cycles simple cog-box, its just an example).

 

[Riding in Circles]

Which bit?

That there has no significant change in efficiency in the last 100 years.

 

[Zoiders]

That there has no significant change in efficiency in the last 100 years.

No there hasn't.

Be it tool steel or modern stainless steel a shaft drive is fairly hard to change at the business end.

 

[Riding in Circles]

No there hasn't.

Be it tool steel or modern stainless steel a shaft drive is fairly hard to change at the business end.

I think there have been significant improvements in shaft drive technology in the last 30 years alone in the motorcycle industry. Both from the use of better materials and in manufacturing tolerances, also in the way the gears are cut.

 

[Zoiders]

I think there have been significant improvements in shaft drive technology in the last 30 years alone in the motorcycle industry. Both from the use of better materials and in manufacturing tolerances, also in the way the gears are cut.

Yes the motorcycle industry.

It still doesn't apply to pedal cycles - the shaft it's self has been improved to stop it winding up under high torque - typically that produced by modern high powered bikes, the gear tooth profile - I don't believe they have done anything that has not been used before in the last 70 years

You are confusing one application with the other.

 

[Norm]

Yes the motorcycle industry.

It still doesn't apply to pedal cycles - the shaft it's self has been improved to stop it winding up under high torque - typically that produced by modern high powered bikes, the gear tooth profile - I don't believe they have done anything that has not been used before in the last 70 years

You are confusing one application with the other.

But the original assertion was that one shaft is the same as another and that nothing significant had happened in 100 years. As you say, there are differences between different applications (carbon tubes, for instance) and changing the shape of the bevel gear's teeth has reduced the losses at either end of the shaft.

A clean, new chain on fresh teeth might be 98% efficient but I doubt that anyone who uses their bike for cycling through the muck and grime will be seeing that level for much beyond the first few hundred yards.

Shafts were also less popular because of the gear options, not just because of the efficiency differences. It was easier to get a wide spread of gears with cogs on both axles. Shaft drive were limited to 3-speed hub gears one just the wheel axle.

Most of us can change a tube in 5 minutes flat ... could be a challenge on that!!

I think (I read the article a few days ago so could be wrong) that there's a simple release system so pulling the wheel out should be straight forward.

 

[gaz]

It has a Shimano 8 speed hub gear.

But for c£1290 and weighing 14kg for a rigid everything hybrid, I think it has as much chance as becoming a commercial success as all its other shaft drive predecessors, i.e. zilch.

£2299.99 for a rigid everything hybrid.

 

[RecordAceFromNew]

£2299.99 for a rigid everything hybrid.

£2299.99? Pah! perhaps enough to buy the mudguard of this contraption...