Generic upgrade concepts

[McWheels]

How about this, a shaft-driven Cruzbike? I wouldn't recommend it for a RWD recumbent, big shaft!
w - dynamicbicyclesuk
But then I also realised the problem, the BB to sprocket distance varies on a Cruzbike.

Nil Desperandum! All RWD cars have a splined driveshaft to allow for the flexion of gearbox vs chassis vs differential. After all, it's not the chain that defines the distance, it's the boom-slider, so a splined variable length drive-shaft would also work with a suspended fork. Trouble is getting one made that suits. Sussex Engineering don't seem to be thinking about it, yet.

 

[mzweili]

a shaft-driven Cruzbike?

angular gears are by far less efficient than a chain transmission.
the grease / wax problem left aside, a chain drive is the best, lightest and most efficient transmission for a bike

 

[jond]

a chain drive is the best, lightest and most efficient transmission for a bike

and cheapest if not the most long lived.

 

[McWheels]

Fair point, but the manufacturer thought of that

dynamicbicyclesuk.co.uk/faqs/

 

[Zzzorse]

Mike Burrows counters,

"At racing or fast touring speeds derailleurs can be better than 96% efficient out of line, and about 98.5% with the chain running straight."

Furthermore, he writes,

"Every few years someone somewhere in the world launches a shaft-drive bike. But they never make much impact. It's an expensive way of building a less efficient bike with limited gearing options, and which may be less pleasant to ride."

 

[LarryOz]

"Every few years someone somewhere in the world launches a shaft-drive bike. But they never make much impact. It's an expensive way of building a less efficient bike with limited gearing options, and which may be less pleasant to ride."

A couple years ago, before I ever even rode a recumbent I commuted daily to and from work.
I rode in everything, rain, snow, etc, etc - no I was not a postman!
Anyway - I actually bought a shaft drive upright bike to test out.
I rode it back and forth to work like I had been doing daily for years. Same route, the bike was similar in size, weight and tires.
I thought, this would be perfect, no chains or derailleurs to clean or replace. The gears where said to last much longer - 10's of thousands of miles.
I did this for a whole month.
I did not have the advantage of a power meter to test with, but I can tell you that there was a good 10-15% loss of power to the wheels, as I went considerably slower for the same effort on the same route.
All the "shaft-drive" makers claim an efficiency somewhat close to that of chains, and also claim that most bikes have un-kept chain systems and therefore are ultimately less efficient that their shaft-drive systems. (I say no way)
I also think that the shaft drive was not designed for as hard of use as I gave it, because after awhile I could actually feel and hear the gears gridig a little.
They told me that I was riding too fast (image that) and the grease was getting flung off the gears and on getting back on them quickly enough. The had me put more grease but it did not really help
I took advantage of a 30-day return policy and basically had to pay shipping and a 10% restock fee. I was happy to do that and not get stuck with the bike.
...
Anyway - I agree that the chain drive systems are probably the most efficient. If they were not, you would see the pros riding something else too - and they are not.

 

[McWheels]

Mike Burrows is the Oracle. Apart from the gearing options, which a nexus 8-speed is quite good at.

And he insists on building his ratcatchers and ratracers with RWD. I think he's been experimenting with internal chains to the carbon frames he's been making recently. For what reason could he turn down the MBB FWD??

 

[super slim]

A couple years ago, before I ever even rode a recumbent I commuted daily to and from work.
I rode in everything, rain, snow, etc, etc - no I was not a postman!
Anyway - I actually bought a shaft drive upright bike to test out.
I rode it back and forth to work like I had been doing daily for years. Same route, the bike was similar in size, weight and tires.
I thought, this would be perfect, no chains or derailleurs to clean or replace. The gears where said to last much longer - 10's of thousands of miles.
I did this for a whole month.
I did not have the advantage of a power meter to test with, but I can tell you that there was a good 10-15% loss of power to the wheels, as I went considerably slower for the same effort on the same route.
All the "shaft-drive" makers claim an efficiency somewhat close to that of chains, and also claim that most bikes have un-kept chain systems and therefore are ultimately less efficient that their shaft-drive systems. (I say no way)
I also think that the shaft drive was not designed for as hard of use as I gave it, because after awhile I could actually feel and hear the gears gridig a little.
They told me that I was riding too fast (image that) and the grease was getting flung off the gears and on getting back on them quickly enough. The had me put more grease but it did not really help
I took advantage of a 30-day return policy and basically had to pay shipping and a 10% restock fee. I was happy to do that and not get stuck with the bike.
...
Anyway - I agree that the chain drive systems are probably the most efficient. If they were not, you would see the pros riding something else too - and they are not.

Larry, I agree as I bought a Mountain Drive bottom bracket for my trike after got having a low enough gear to climb at a 40 cadence, a 20% incline, 5 km long damp dirt road, in Tasmania, from the bottom of Liffey Falls, on a 60 kg trike with a 12.3" gear inch.
I had to pedal in bursts at 20 cadence , then lock my knee, as the front brakes would not stop me sliding backwards!

My brand new three lengths of chain was completely stretched after that 1,600 km Tasmania trip, and I think it was all done on that one hill climb!

I fitted it to the Silvio to see if a lower gear (so 80 cadence, instead of 50) would give me a faster time up a 6.5 Km long 5.5% average grade hill climb.
I was 10% slower at 80 cadence, and with a chainring change so the Mountain drive was the same as a 30T Chain ring, it was 5% slower!

I removed it after that, and sold it 2 years later, after touring loaded on the Softrider around NZ!

 

[bladderhead]

you would see the pros riding something else too

UCI would ban it.

 

[Zzzorse]

Maybe there is a way to make a shaft drive that is highly efficient.

 

[Rampa]

That is super cool, but I think you lose a great deal of efficiency just changing angle in power transfer like that. This transfers power at 90 degrees, while a chain is straight. But I want one anyway if they make them!

And UCI was concerned about spinning disc rotors!

 

[McWheels]

Anything that moves against anything else creates friction. But what's clever about their idea is that the drive-shaft's teeth [bearings] rotate, so they can be static relative to the teeth on the ... sprockets I suppose. The drive shaft's bearings is then quite simple. Certainly it's a step above that thing at the top of the thread. Another good observation was the number of things that could muck in them and slow down. It's not all weather, but maybe a track bike?

 

[bladderhead]

So, normally you have friction between the teeth of two cogwheels, but here you have friction within one cogwheel. So they have just moved the site of the friction. Does that reduce friction?

 

[Rampa]

They have done more than that. By having the "gear teeth" be bearings, it is probably slicker than well designed involute gears (like in your car). The "tooth" rolls with the passing cog-notch in this case.

 

[Rampa]

Here is a video just about it.

 

[benphyr]

And a nice muddddddy / slushy ride. Would that equal a completely worn out $10,000 drivetrain, $5,000 worth of parts, "chain-guards" for dirty conditions, a pressure washer or a garden hose? And how do you re-lube those bearings? I know they are at the beginning, but these questions have 100years worth of working them out on chains. It would be great if this could incorporate a better solution for that too otherwise it is only really helpful for racing. Kind of like KERS that is completely burned up by the end of one Grand Prix.

 

[bladderhead]

With a IGH when you change you can jump several gears. I do not think this system will allow that. But as a fixie it would work.

He says you can change the ratios by putting a different end on the shaft, but that would be a different radius, so the shaft would need to be sideways adjustable.

 

[benphyr]

With a IGH when you change you can jump several gears. I do not think this system will allow that. But as a fixie it would work.

He says you can change the ratios by putting a different end on the shaft, but that would be a different radius, so the shaft would need to be sideways adjustable.

I think he was saying that the computerized timing (like machine-gun through the propeller it seems to me) would choose when to shift based on current torque levels, pedal position, and possibly other factors and would do it VERY quickly - that is, multiple gear change at once would be so fast as to not be noticeably different from several gear jump with an IGH.

Awesome observation bladderhead -sideways adjustable would make it at an angle relative to the teeth and re-introduce sliding friction, but maybe that rear "cog" could be made adjustable - in/out to match changing drive shaft ends so that the shaft always is maintained perpendicular.

 

[bladderhead]

Elliptical chainwheel.

 

[tiltmaniac]

I wonder why they haven't realized that it is easier to have multiple pinions, which can separately engage or disengage.
Perhaps they're worries about losses?

In any case that'd be a simple mechanism and allow for shifting at any time.

I think their approach has some real merit, especially if you consider that you can make the drivetrain the hub of the wherl (or integrate with it partially.
Since the wheel isn't asymmetrical, you can have a less wide hub overall, as well, which could claw back some weight as well.