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| vtsteam:
Great Steve! :smart: I've had some things from HK arrive in 3 weeks and some in 5 days even without extra postage. One more point about load and power -- hills will obviously make a difference to amp draw. I'm guessing you'll have to keep an eye on your ammeter on a hill, and slow down until amperage is in the comfortable range again. Not entirely sure how this is all going to work out -- as I'm really used to airplanes -- it will be really an interesting thread to see how it all works out in practice instead of theory. :coffee: :coffee: :coffee: |
| S. Heslop:
--- Quote from: kayzed1 on June 02, 2014, 04:53:31 PM ---I have a pair of motorcycle sprockets here if you want them, not new but good, 420 chain size. Lyn. PS: may even have a new DID chain as well.. --- End quote --- Thanks for the offer but I don't think I really need a chain and sprockets any more with the friction drive. --- Quote from: vtsteam on June 02, 2014, 05:03:58 PM --- Not entirely sure how this is all going to work out -- as I'm really used to airplanes -- it will be really an interesting thread to see how it all works out in practice instead of theory. :coffee: :coffee: :coffee: --- End quote --- Yeah i'm excited to see how it works out too. It's kind of been a lifelong dream to stick a motor on a bike, but I never really knew enough to manage it. I still don't know enough, but having the internet helps! |
| S. Heslop:
The gears just arrived in the post this morning, they're really not bad for £5 a pair, and that's everything now delivered. As for the plan, I spent a while fussing and figured the best way to go about it would be to build a sturdy carrying rack on the rear of the bike for the motor/ idler to pivot on. It's a bit of a clumsy looking design but it's the best I could come up with! A spring on the lower of the 3 bars on the arms will hold the rollers against the rim, and the top most bar will hopefully act kind of like a caliper brake (controlled by cable) to release the rollers from contacting the rim if I want to pedal. Here's a still from some video I took. I made the punch from a motor shaft, and it's the first piece of steel i've ever successfully hardened thanks to John Doubleboost's video. Heating it till it stopped being magnetic and then quenching in oil did the trick. (I just noticed that they kinda look like the British Isles. It might be sub-conscious since it's all britain this britain that on the tv at the moment!) I went to the boot sale today to buy a better jigsaw. I was surprised to see so many people at a Wednesday boot sale. I guess i'm not the only person unemployed in the north east! I also picked up a nice new bench grinder and wrecked arms carrying it home on the bus. In other news, I've been trying to buy batteries off of ebay. I guess the word got around that laptop batteries were a good source of cheap lithium ion cells. At 8am yesterday morning I decided to try bid on an auction that was at £12 for 20 used batteries, but in the last 5 seconds it jumped up twice to £50! I suppose even at that price it'd still be cheaper than the £500+ they charge for dedicated eBike packs. I've got a bunch of mismatching NiCd RC car packs I might try rewire to test the motor, but first I want to get some of the metalwork done. |
| vtsteam:
Wow, great drawings Steve! Would laptop batteries have a high enough C rating for the motor? They should be able to deliver close to 100 amps. Seems like R/C batt packs would be the cheapest and most suitable -- even the low cost ones are 20-30 C. Probably cheaper to put together multiple smaller packs than buy a larger pack. 3S and 2S packs are often the lowest cost per watt hour. At 20 C and the minimum possible capacity you'd need a 7S 5000 mah pack. You could make up that from a series hookup of (for example): http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=31952 http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=32119 You might want bigger capacity than that, which is fine if you can afford it. But it may be more cost efficient then to start paralleling packs -- you'd have to work it out. A word of warning about HobbyKing which I just used as an example. Never order batteries from them overseas -- ONLY buy from the UK warehouse, and ONLY if the item is listed in stock. Their customer service and honesty are not beyond question in my experience, and you could wait months to receive an order -- or even never receive it. Generally orders from the local country HK warehouse are reliable, but sometimes they gouge you on postage. If you use another source for batts that you know well, that's a good option. I use Zippy brand batteries in my planes and they are a good low cost reliable batt. |
| vtsteam:
I should mention, of course, and probably you already know that Li-ion cells like laptop batts are safer than Li-poly batts like R/C batteries. But both need special chargers, or you run a real risk of fire and explosion. Nothing to fool around with. In my opinion the best Li-poly chargers are the ones that charge each individual cell through the balance plug, rather than the type that charge across the whole pack and require that you periodically discharge and balance individual cells. The former is simpler, faster, cheaper (for the charger) and foolproof. There are other cells which are safer -- A123's or LiFe I believe, but they are a different voltage per cell and more expensive so the number of cells etc. would all be different. |
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