Whilst perusing some fascinating 19th century material on chainless bicycle solutions, I happened across this drawing of the Hildick Chainless Bicycle Gear.
The Hildick Chainless Bicycle Gear (1898)
Given the main reason for replacing the bicycle chain is to obviate a messy, potentially dangerous and fragile drive system, the decision to opt for a large, open gear and all the greasy, moving parts that entails seems somewhat eccentric. In case you haven’t worked it out, the inner ring of the mechanism is fixed and the outer ring runs on bearings, something like a giant freewheel. In its favour, it looks as though it could have been retro-fitted to any standard, chain-driven bicycle.
It made me reflect on something I’d once read Dean Kamen, inventor of the Segway, say about the South Pointing Chariot invented by the ancient Chinese – a cart which, through an assembly of differentials, pinions and annular gears, would always point an indicator stick South, no matter in which direction it was driven. The odd thing is that the Chinese had already discovered the magnetic properties of lodestones and thus had a ready method of detecting North even when unable to use astronomical navigation. They had essentially reinvented the problem! Now, if only someone had pointed Mr Kamen towards the bicycle he might have saved himself a lot of bother.
To me, the most elegant solution for a chainless bicycle offered in the late 1890s was the bevel-geared shaft-drive system by Sterling and others in the USA, possibly because it looks so much like the hand-operated food mixer I remember mentally disassembling as a child. Unfortunately, it would probably have limited serviceable life due to gear wear – the bevelled teeth providing such a small point of contact that they would be unable to take the full leverage of the crank over a prolonged period – but it does offer some inspiration.
The Sterling bevel-geared Chainless Crank Bracket (1898)
What if the crank axle were a fixed worm gear so that there was more metal in constant contact with the drive shaft and hence a more evenly spread load? This after all is the chief benefit of a chain – the spread load of numerous teeth being driven at once. Would the gear ratio be too low to be practical? It would certainly take up less space in the bottom bracket…
If we revert to a chainwheel and chain, with the appropriate constraining rollers, there is no reason at all we could not have a chaindriven system which was completely enclosed in the chainstay!
Any thoughts?
UPDATE: Appears that UK company Zero Bikes have already resuscitated the shaft-driven chainless bicycle. I really should keep up to date!
UPDATE 2: OK! There’s also Dynamic Bicycles in the USA. Jings! I’m so out of touch!
UPDATE 3: Yes…and also from Beixo in the Netherlands. This post is now closed!
r:B
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January 25, 2009 at 4:10 pm
WestfieldWanderers
From the CTC web site Chris Juden writes the following:
Shaft drive has also been tried many times during the history of the bicycle, often combined with hub gears, indeed there are bikes on the market with it now, but they will never enjoy general popularity …
Shaft drive involves two right-angle direction changes, requiring bevel gears or the like, meshing at very low speed with consequentially high tooth pressures. Gears (particularly bevel gears) exhibit high frictional losses under such conditions and in tests a bicycle shaft drive was found 8% less efficient than a clean well lubricated chain transmission, or about on a par with a worn-out, dry and dirty one!
The high torque also twists the shaft and that makes the drive feel soggy. A carbon-fibre shaft would be good, but too luxurious for an inevitably less than efficient bike – so shaft-drive is heavier too. In conclusion: it works well enough for an undiscerning or inexperienced rider not to notice any problem, but inexperience is a temporary condition!
It’s not so difficult anyway to ensure that a chain remains clean and well lubricated, whilst neither throwing off nor spreading lubrication where it isn’t wanted.
He concludes by suggesting: Simply fit a chaincase!
Sounds utterly reasonable to me! Call me a Luddite if you must, but to me the enduring attraction of a bicycle is its beautiful simplicity. The basic design is a long established classic. I deplore the constant efforts to make a simple, efficient, easy to maintain machine more complicated, expensive and non-user maintainable than it needs to be. Sure, it’s only human to try and improve something and innovation is something to be applauded, but innovation for innovation’s sake, creating answers looking for questions…?
January 25, 2009 at 9:23 pm
R::B
Well said and heartfelt I’m sure!
On the whole, I have to agree. Engineers often have a pet solution and are simply looking for problems it’ll fit in order to show off their brilliance, but there’s a point at which the “solution” becomes the problem.
Like dragging a south pointing chariot around when a small sliver of magnetite on the end of a floating leaf would have sufficed…