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| S. Heslop:
--- Quote from: vtsteam on May 31, 2014, 11:08:50 PM ---What about chain drive? Sprockets and chains are available from tractor/farming supply companies. Have you worked out your wheel size and some idea of what kind of reduction ratio you want to try? The larger the wheel size the greater the reduction needed. Also, how many volts and what type of battery will you be trying? It might be economical for testing and ballpark estimating to just find a used 12V car battery and make a wooden kart and see what that will do, then move on to whatever else you have in mind once you've established a baseline for components. Also, aren't there motorized bicycles that use friction drive against the wheel rim? A clutch and reduction rolled into one, and a pretty big reduction ratio. --- End quote --- I'm aiming for 24 volts. I've got a whole bunch of old RC car NiCd packs I thought I could rewire to test it, and if it works out I'll go hog wild and build a gigantic lithium battery. I was thinking of using 12v sealed lead acid batteries, but i've been reading that they can't really supply enough current to keep up with brushless outrunners. I live in an ex industrial area, all centered around the long gone Connsett iron works. But that means there's a whole load of disused railway cycle paths (complete with viaducts!) that go all over, and one goes right by house. It's a silly idea but I thought I could ride the bike up to my grandparents. I visit weekly and the bus fare costs £7 just to get there. My grandad usually drives me back home but he really doesn't feel comfortable leaving my grandma alone for too long in case she injures herself when he's not around. And I sure as heck can't afford my own car on a student loan. But yeah i'd be surprised if I could produce anything rugged enough to survive long weekly trips, but at least it's all downhill back home if something breaks! Y'know I never thought about running a motor on the wheel's rim. I'd only seen photos of people running them against the tyre. If I had a bike with disc breaks that might work well, but with the rim breaks on this bike I can't think of anywhere I could easily attach it. |
| vtsteam:
Steve I just looked up figures for that motor and them ran them through Motocalc as a fictitious airplane to try to get some figures out of it. As an estimate at 5700 rpm and 24 V and a 7 cell lipo pack you should be hitting it just about at your target power -- 485 watts output from the motor with an additional waste wattage of 66 watts, estimated motor efficiency 88%, current 23 amps. Hypothetical, and based on assumptions and mfr's figures for idle current and resistance , but I'm pretty good at monkeying motocalc and I tend to get good results. Will 500 watts motor output push you an your stuff at 30 mph? Dunno that part. But I'm rooting for ya! |
| S. Heslop:
Yeah i'd be surprised if 500w reached 30 mph but it should be enough to push me along under its own power at a lower speed. I kinda wish I ordered 3 sets of gears now! Although with a bigger gear box I won't be able to fit in the space i've got... I guess I could always go for a bigger motor if needs be. I wonder how the tiny gears would hold up too. And i'm also wondering how speed controllers designed for RC planes would hold up. I guess you only learn by making mistakes~ |
| philf:
A very interesting project. Unless I'm missing something obvious I don't think your Halfords freewheel is going to work on the left hand side of the bike (unless you try to ride it on battery power backwards)! Going out on my bike now - 80 plus miles into Cheshire. I may be wishing I'd got electrical assistance for the big hill a mile from home. Cheers. Phil. Edit: I've just been thinking about this on my ride and of course you can fit a single speed freewheel either way round but you will need a left hand threaded lock ring to stop the freewheel unscrewing. You can buy hubs which are designed for fixed on one side and free on the other which would do the job. Just sat in a cafe waiting for my cheese and onion toastie. Phil Last Edit: It looks like not all single speed freewheels will fit the wrong way round. Phil. |
| Joe in Oz:
I'm watching with great interest! You will need to think about cooling for this motor. In an RC plane, it has the propeller wash cooling it - on your bike it has the draft from going forward when you do - up to about 30mph in your estimate. That's nothing like enough I believe. So you need to moount a little blower and shroud on the shaft as well. Looking forward to your results and reports - good or bad! Cheers, Joe |
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