I was about to point this out; maybe it’s pedantic but this is an engineering matter and pedantry is important. Chains of this sort do not stretch; the side plates are not under anywhere near enough stress to lengthen them. Well, I’m going to assume that you’re not using a small bicycle chain on a real 240hp motorcycle; possibly that would in fact stretch the side plates, briefly, as they turn to toffee. Simple back-of-an-evelope reality check - if the forces in play were enough to actually permanently deform the side plates, how would the pins (much smaller cross-section) possibly survive transmitting that force?
What happens is the pins and rollers wear over time, depending on lubrication, power load and so on. At least for modern motorcycle chains that wear is extremely small with even cursory lubrication by the owner. I’ve had chains last … well, goodness, seemingly forever. Yes, eventually the small rotations back and forth of the pin in its socket within the side plate will wear a small amount off the plate and pin. Summed up over the entire chain that tiny wear will make the chain length a bit longer. It’s wear, not stretch.
On a barely-powered veloci-hipster like this I doubt there is much more than 1kW in use and you could get away with a bit of string to connect the motor and rear wheel. I really doubt any of these will get enough total usage to wear anything expect patience.
Modern bicycle chains do wear quickly, though. I have to change the chain about once a year on my commuter bicycle (about 1500 miles, at a guess). It’s recommended that it should be replaced when it’s ‘stretched’ about 0.75%; the last one I changed was about 1.5% longer than when it was new. Admittedly, this bike does have a derailleur, so the chain will spend most of its time in a non-optimal alignment.
Funny how much this bike resembles the styling of the first commercial motorcycles >100 years ago. Which of course were really just bicycle frames to which an inventor incorporated a motor, like this.
Did I miss the phase in the product evolution cycle of the motorized velocipede or was that not ever a thing, what with its lack of rake and associated scary, twitchy turning even at the slowest of speeds?
Please forgive me; I’m going further down the rabbit hole of detail and pedantry here.
You’re correct to point out that “chain stretch” is actually a phenomenon of wear. But you’re wrong that it’s negligible on a typical bicycle. Bikes tend to use very narrow chains with small pins and thin side plates. In daily use they typically last around a few thousand miles before accumulating significant (1/8" per foot) stretch. By the time they hit that mark, they’re pretty much worn out.
On single-cog, single chainring bicycles, you typically don’t use a spring-loaded chain-tensioning device, so they’re generally designed so that you can move either the cog or the chainring back and forth, allowing fine adjustment of chain tension. As the chain wears, even before it’s totally worn out, it will become noticeably loose. Readjusting the effective chain length (by repositioning the rear wheel or bottom bracket) allows the chain to be used through its full service life.
I have a moped, although the vestigial pedals on the thing are mostly for regulatory reasons, there are some fun use cases they enable. What? Road closed for construction but I can see a safe path through? Simply kill the engine, tweedle through with the little spinny pedals, once the obstruction is past, start the engine back up and continue upon one’s way.
Also works for sidewalks, playgrounds, parking lots, lawns, buildings, and cemeteries.
So, buy an old bike, and make one.
You could just start with a bike that already has the desired aesthetic:
and add conventional electric power. Or, you could top everything, and take your inspiration from bikes that I find particularly cool, which are the ones powered by a radial engine built into the wheel:
I have a couple of friends who put together electric bikes with parts from the same company.
I’ve only seen the one. It’s a Specialized fat-tire comfort bike, cost him maybe $1700.00, is quite comfortable and can go about 30 mph.
This one takes more cargo, is pre-built, has a HUGE battery, goes 40 mph and has that nearly irresistible light.
Not a bad idea, but you really don’t want to discount the weight of the battery and drive system. Depending on specifics, you can easily double the bike’s weight even without using lead-acid batteries. Another overlooked issue is how much easier it is to break parts when you’re moving under power at 30 MPH or more. I went through spokes like crazy going 28-30 all the time, but haven’t had any issues since limiting the current to top out at 20 MPH. Starting with an old frame means checking for cracks more frequently as well.
I would suggest stripping the frame, and reinforcing it with stronger tubing. I have bending equipment, so I would likely build the frame from new and stronger tubing.
I was just suggesting an economical way to achieve something with the same sort of aesthetic. I agree that doing so would not be without challenges. And the weight thing tends to compound itself.
