Saw a two-wheel-drive bicycle yesterday.

cj7hawk
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Saw a two-wheel-drive bicycle yesterday.

Postby cj7hawk » Thu May 19, 2016 1:19 pm

Was walking back from lunch in West Perth and saw a nice home job. What looked like two 1kW motors mounted on a bike, with two controllers and batteries. It wasn't going fast or speeding at all, but I reckon it would ride nice, and I couldn't but help think ElDavo might like something like that on a fat bike since it would make riding on the beach pretty nice. Actually, that makes me wonder whether using a couple of motors and a passive link between them would be good for beach riding since it would distribute the effort across both wheels and keep the bike from bogging down the front wheel a bit more.

Anyway, sorry for the lack of photos. I didn't have enough time to get one -

David

eldavo
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Re: Saw a two-wheel-drive bicycle yesterday.

Postby eldavo » Thu May 19, 2016 1:38 pm

Two wheel motors have been done many times, lots of forum theory brain thrashing about the merit. Consensus from motorcycles to bicycles seems to be not very beneficial over a single rear motor most of the time. Typically the front works well being light and floating, while the rear has the weight bias and the power/traction. Moving forward takes traction off the front, so its more front wheel roost, rear wheel drive, than all wheel drive.

In Paris-Dakar they have had low power hydraulic motors on the front wheels powered off the engine, and currently there's a local adventurer riding 400km in Greenland testing a fat bike for a South Pole attempt, using a custom power takeoff pinion drive from rear left side hub through shaft in frame to drive the front wheel, conventional pedal crank drive right side supplying the power take off. People riding those conditions have said when it's that bad for a front to have merit, it's usually so slow at the threshold for putting it on the sled and hiking it. The pinion setup doesn't look very heavy to be a handicap if it's not very useful. Will be interesting to see how it goes. I'll update with her name and pics when I get to a PC.

There's a dual 3kW motors rigid fat bike with footage on dunes footage on YouTube. It's riding around motorised offroad vehicles. Looks bumpy but the weight probably keeps the front down for climbing and affords less rider skill for hill climb body positioning.

People still like doing stuff just coz, we don't really know until we experiment. Heck, there's even some local guy who made a petrol electircity generator to an electric assisted bicycle ;)

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mikedufty
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Re: Saw a two-wheel-drive bicycle yesterday.

Postby mikedufty » Thu May 19, 2016 2:59 pm

I saw a dual motor bike in West Perth yesterday too, but it seemed to be a central drive (through the chain to rear) bike with a rear hub motor added, so not 2WD.

My own bike is the more common 2Wd set up, electric to the front and pedal power to the rear.

The front drive seems to work very well on most surfaces, though it will wheel spin slightly from a standing start if you are not careful. Surprisingly stable while doing that, I guess the extra gyroscopic force offsets the lack of traction.

The most surprising thing is it doesn't seem to have increased the front tyre wear noticeably. The power must be fairly balanced as I do a similar speed when experimenting with pedal only or power only (but 99% of the time do both at once. I guess the extra wear on the rear is primarily due to the weight distribution, not the power, at bicycle power levels. Currently on my third rear tyre and original front. Although about half the km were pedal only (rear drive only) I have worn out one rear completely in 2WD mode.

I have often wished for 2WD when trying to ride an MTB on soft sand, but a fat bike would probably be more effective, I'm not sure how much benefit you would get in practice from the front in those conditions when it is impossible to put enough power through the rear to keep moving without digging a hole, probably just get sand in your face.

eldavo
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Re: Saw a two-wheel-drive bicycle yesterday.

Postby eldavo » Thu May 19, 2016 4:09 pm

What colour/frame was the one you saw Mike?

Weight bias and wear sounds right. You can do it on your bathroom scales to see the weight split. I run lower front pressure on some upright ergonomics road(path) bicycles with wider tyres to take the harshness off the bars, e.g. on a 20in have a 2.1 front Big Apple Plus low-mid pressure and a rear 1.35 Marathon Plus at max pressure. Or on the 29in CrossMark 2.1 front/rear have minimum 35psi front to 65psi rear.

MTBs are cottoning on to the wider rims and lower pressure, Schwalbe have a new dual tube/tubeless system now for high pressure rim protection, with tubeless tyre carcass benefits. Minimum 25mm rims. With 29+ 29plus semi-fat, you could run a light motor like you have, lower pressure from the larger volume tyres, and split the difference in the extreme from skinny to fat (like 27.5 split the difference from 26 to 29). New snow extreme 5.5in Snowshoe 2XL is prompting even larger frames and 120mm bottom brackets =D

Someone told me in NZ there's some fan/blade thrust powered bicycles mounted to front racks bulky like the Velo-Solex but thrust power front, conventional pedal rear drive. I haven't looked/found a link yet.

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mikedufty
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Re: Saw a two-wheel-drive bicycle yesterday.

Postby mikedufty » Fri May 20, 2016 2:58 pm

I think the one I saw was a silver/bare aluminium colour. One of those purpose built ebike long wheelbase frames with the battery between seat tube and rear tyre, but with an extra battery on the top tube.

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