Bike with two gears and two chains

[lenny]

Why it makes perfect sense for this bike to have two gears and two chains
Bike design seems like a solved problem, but there's a lot to learn from Buffalo.

Why it makes perfect sense for this bike to have two gears and two chains

Bike design seems like a solved problem, but there’s a lot to learn from Buffalo.

arstechnica.com

 

[guerney]

I've only had one bike chain break, many years ago when I started cycling, and it was due to my incompetence at joining links - I was pedalling hard uphill at the time, chain broke, I topppled over and chipped a tooth on the tarmac after losing balance at sudden unexpected low speed. This two chain solution looks interesting. Broke a chain? Use the other. I could get away with using just two gears with my legal 36V 720W Bafang BBS01B mid-drive 20" wheeled folding Dahon: 1 of 8 and 6 of 8, if gear ratios and BCD spider adapter for the chainwheel etc. were compatible. It'd be the end of the "Single point of failure" on mid-drives stuff a certain forum dude kept going on about until recently.

(video cued at the explanatory bit)

 

[saneagle]

I've only had one bike chain break, many years ago when I started cycling, and it was due to my incompetence at joining links - I was pedalling hard uphill at the time, chain broke, I topppled over and chipped a tooth on the tarmac after losing balance at sudden unexpected low speed. This two chain solution looks interesting. Broke a chain? Use the other. I could get away with using just two gears with my legal 36V 720W Bafang BBS01B mid-drive 20" wheeled folding Dahon: 1 of 8 and 6 of 8, if gear ratios and BCD spider adapter for the chainwheel etc. were compatible. It'd be the end of the "Single point of failure" on mid-drives stuff a certain forum dude kept going on about until recently.

(video cued at the explanatory bit)

The design is fundamentally flawed. It'll work great in tests with new chains, but after a few miles the chains will wear at different rates, mainly because they're different lengths and the fact that one will be doing the drive a lot more than the other, then one will start jumping off. The tensioning system can only adjust both chains together the same amount.

 

[Ghost1951]

I've got an old Releigh Superbe with a fully enclosed chain case. I've looked in there at the chain and I bet it is the original one. It looks perfect. Not even a spot of rust. Chains sized and stressed like those should last a very very long time if they are oiled now and again. The enclosed chain on my CG 125 has done 17,000 miles and it's pretty much happy to have a light brush iof engine oil every 300 miles and a very occasional adjustment. I think that's the original chain, as I've had the bike for half of its mileage.

 

[saneagle]

I've got an old Releigh Superbe with a fully enclosed chain case. .............Chains sized and stressed like those should last a very very long time if they are oiled now and again.

I bought a chain from Ebay about ten years ago. It's still in its sealed packet in my spares draw. Inside the packet seems to be a lot of oil. Your post inspired me to check it. Guess what? It still looks like new, just like yours.

Compare that with the one on my bike that doesn't get oiled and needs to be replaced every 10,000 miles. I therefore conclude that oiled chains don't deteriorate unless you use them. You learn something new every day. Thank you for enlightening me.

 

[Ghost1951]

I bought a chain from Ebay about ten years ago. It's still in its sealed packet in my spares draw. Inside the packet seems to be a lot of oil. Your post inspired me to check it. Guess what? It still looks like new, just like yours.

Compare that with the one on my bike that doesn't get oiled and needs to be replaced every 10,000 miles. I therefore conclude that oiled chains don't deteriorate unless you use them. You learn something new every day. Thank you for enlightening me.

Your theory is partially correct. Indeed an unused oiled chain will last a long time. Surprise surprise, but that isn't what I am talking about. The Raleigh bike has not been unused and neither is the chain on the CG125. Tht chain has done about 8,000 miles with me riding it and transmitting 6 to10 hp for that distance. It shows very little wear since I started riding it and I conjecture that the chain is original on the basis that it had some wear when I first got it at 10,000 miles and shows a little more at 18,000.

The point is that sturdy chains, protected by the enclosed chain guard and regularly oiled and kept away from water and grit, last very very well. As an example - think about the enclosed primary drive chains in the old motorcycles both you and I started out with. They lasted pretty much forever if the oil bath was maintained at a sensible level, as did the cam chains in our old cars and even Jap motorcycles.

That's all I am saying. No need for the edgy tone in the above post.

 

[saneagle]

Your theory is partially correct. Indeed an unused oiled chain will last a long time. Surprise surprise, but that isn't what I am talking about. The Raleigh bike has not been unused and neither is the chain on the CG125. Tht chain has done about 8,000 miles with me riding it and transmitting 6 to10 hp for that distance. It shows very little wear since I started riding it and I conjecture that the chain is original on the basis that it had some wear when I first got it at 10,000 miles and shows a little more at 18,000.

The point is that sturdy chains, protected by the enclosed chain guard and regularly oiled and kept away from water and grit, last very very well. As an example - think about the enclosed primary drive chains in the old motorcycles both you and I started out with. They lasted pretty much forever if the oil bath was maintained at a sensible level, as did the cam chains in our old cars and even Jap motorcycles.

That's all I am saying. No need for the edgy tone in the above post.

Motorbike chains are different. If it's lasting more than 10,000 miles, it probably an O-ring chain with the grease sealed in. They typically last about 20,000 miles, then the worn O-rings let the grease out and the water in causing imminent demise.

I've never heard you mention that Raleigh, so who's riding it or not?

I had a Honda CD175 with fully-enclosed chain case, which I rode to over 60,000 miles commuting in all weathers and winter touring. I bought the best chains I could get and tried every technique to prolong chain life, including boiling up in the grease and swapping chains every month, but I could never get them past 10,000 miles. They were plain, not O-ring ones.

 

[thelarkbox]

Perhaps the next iteration of the design will incorporate a simple sprung chain tensioning wheel or two if differences in chain wear do become apparent? even if an enclosed chain does fair better the bike in question has chains open to the environment..

 

[Ghost1951]

Its a plain ordinary chain. That bike only puts out about 10 hp. Even my 20 hp honda cb 250 has a plain roller chain which was half worn when i got it and that one has done about 5000 miles with me. I don't thrash them mind, and i oil them frequently with gear oil on a paint brush. Same on my ebikes. Sadly, the Argos folder chain got wet and salty this winter and rusted, while layed up for the bad weather. I got it out on a nice day a week or two back and the chsin jammed. I got it freed up, but it is spoiled and compromised now.

The difference between enclosed, oil bath chains and those running on wet, salty, winter roads is huge.

 

[guerney]

One of those chains sure looks bouncy. I hazard the SRAM design dude considered ways to build a tensioner within the freewheel gizmo, but discarded such fancies because this drivetrain is intended to be robust, cheap, low and easy maintenance.

 

[saneagle]

One of those chains sure looks bouncy.

That's because the other one is already tight, so the wheel can't be pulled back to tension the main chain.

 

[Hoppy33]

What’s wrong with 3-speed Sturmey-Archer hub gear? Absolutely reliable, even when thrashed to death, totally abused, with zero maintenance.

As a teenager in the late 60s, I had a second-hand boneshaker and rode it hard everyday, everywhere, all weathers, to school and then paper-round six days a week, and up to the rec most evenings to kick a football around with mates. They also had similar bikes - derailleurs were around, but nobody had them.

Many thousands of miles. All the sprockets were hooked, chain knackered, but that Sturmey-Archer never failed.

 

[Ghost1951]

What’s wrong with 3-speed Sturmey-Archer hub gear? Absolutely reliable, even when thrashed to death, totally abused, with zero maintenance.

As a teenager in the late 60s, I had a second-hand boneshaker and rode it hard everyday, everywhere, all weathers, to school and then paper-round six days a week, and up to the rec most evenings to kick a football around with mates. They also had similar bikes - derailleurs were around, but nobody had them.

Many thousands of miles. All the sprockets were hooked, chain knackered, but that Sturmey-Archer never failed.

As long as they are properly adjusted, they work extremely well. Perhaps in the context described here though, they might be more finicky than what is described. On this two gear bike, I have no idea how that kick back mechanism works at the component level though. The freewheel pawls must be disengaged, perhaps a cam which works on it. I don't know.

There was someone on here who was experimenting with a sturmy archer SRF3 as the transmission for a crank motor. That would be an interesting test of the long term reliability of the srf3. Most riders of three speed bikes will never put out as much power as a legal crank motor. They are not generally Lance Armstrong types. Thinking about how they are made and how they operate though, there is not much to go wrong, as long as the steel they are made from is hard enough to stand the forces involved in changing gear. I can imagine that powered gear changes could remove the corners of the clutch dogs in time as the parts crunch together while powered by the motor. A gear change switch would be essential I think.




EDIT:

As to SA wear under motor power - the fact that you can buy spare parts for the srf3 for pawls and clutches and such does suggest that they wear in time under normal use, which would not bode that well for the experiment detailed above.

They do wear out though:

Sturmey NIG 3s hub; what to look out for, what breaks. - Cycling UK Forum

 

[saneagle]

What’s wrong with 3-speed Sturmey-Archer hub gear? Absolutely reliable, even when thrashed to death, totally abused, with zero maintenance.

As a teenager in the late 60s, I had a second-hand boneshaker and rode it hard everyday, everywhere, all weathers, to school and then paper-round six days a week, and up to the rec most evenings to kick a football around with mates. They also had similar bikes - derailleurs were around, but nobody had them.

Many thousands of miles. All the sprockets were hooked, chain knackered, but that Sturmey-Archer never failed.

It's not automatic like the Bafang one.

 

[Hoppy33]

How much energy did I have in those days!! Unbelievable. And quite a few of those miles were with a mate on the crossbar. That was a tortuous experience all round.

SA hubs are hardly a secret though, so I guess they must have been dismissed for some reason. Maybe cost, maybe supply chain and business hurdles?

 

[saneagle]

As long as they are properly adjusted, they work extremely well.

Until you try to put 80NM from a modern crank motor through thrm. Only three ratios in them sucks too, which is the main reason nobody wanted them.

Also, you forgot the bit about whenever you fell off your bike, you smashed the little shift chain thing and thereafter got stuck in top gear until you could persuade your dad to buy you a new one. Does this picture bring back memories?

Pardon our interruption...

 

[Ghost1951]

Until you try to put 80NM from a modern crank motor through thrm. Only three ratios in them sucks too, which is the main reason nobody wanted them.

Also, you forgot the bit about whenever you fell off your bike, you smashed the little shift chain thing and thereafter got stuck in top gear until you could persuade your dad to buy you a new one. Does this picture bring back memories?

Pardon our interruption...

Funnily enough I never broke one of those. Maybe I was lucky. They do go out of adjustment now and again though, although I can't see why, but they do. I rode an SRF3 for 4000 miles on a fake Chinese alu Bromton, and I stripped the hub to look at it after finding some bearing cones needed adjustment. I modified the hub a little to fit an oiling port as was used on the old SA hubs before they were made in the far east and grease was used. The hub has no oil seal, so you could only put a few of drops in or it would come out and go everywhere, but I rode the bike a lot after that and it never needed any more stripping down. The bike got retired when the frame suffered a failure. That would never have happened on the original B bike. It is still rideable, but I have a proper Brompton now and it is vastly better than the fake.

Brik fitted an SA hub to a bike with a Bafang 250 watt mid drive motor. Seemed to work for at least as long as he kept us informed.

BBS motor with Gates belt...

...has any one done this? I'm hankering after some shiny new metal as a bit of a treat for my upcoming birthday and have spotted a new belt drive bike with hub gears, It looks like the bike uses a concentric bottom bracket to tension the belt and I'm wondering if it would be possible to at least...

www.pedelecs.co.uk

 

[Ghost1951]

Great video on stripping and cleaning SA AW hub. I would have lubricated parts much more than he does, but the video is very clear about taking it apart and re-assembling it.