leolion Scooby Slapper
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kgm World Chat Champion
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G The Voice of Reason
Joined: 02 Feb 2002 Karma :
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Easy-X Super Spammer
Joined: 08 Mar 2019 Karma :
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Posted: 13:13 - 22 Jun 2019 Post subject: |
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Brace yourself! Tef level reply incoming...
I've had a similar moment of madness. Things to consider...
Ebike motors
You can have any size motor you like on the back or for mid-drive but on the front you'd want the very lightest possible so 250/350W internally geared motors. So a bit lacklustre TBH but it will get a "normal" bike to 15mph however what we're talking about here is a MUCH heavier bike so 250W is just a little boost. (Your own legs can put out ~700W.)
For any ebike you need a controller, battery, pedal sensor and/or throttle... maybe a display. (Mid-drives tend to have the controller built into the motor case.) All that stuff has to go somewhere on the frame, more on that later...
50cc el cheapo chinesium motors
Assuming you have a standard "trapezoid" frame you'll need a fairly large one. I normally ride 17 to 19" MTB frames but the petrol motor only just fitted within a 21" frame in the end. Luckily my inside leg is relatively long (wayhay!) for my size so it was still rideable. (BTW, hardtail only frames.)
Okay, so you've just consumed all the space "inside the triangle" so where are you going to place the ebike battery? Hmm... maybe a pannier rack one? Maybe not...
The petrol tank is a PITA and was my ultimate defeat for getting the conversion bike through the MSVA. It's neck sticks up too much and about the only way round it, as far as I could see, was to mount it on a pannier rack at the back to avoid any "knackers caught on filler cap in a crash" type issues.
Also consider the petrol motor needs a motorbike sized throttle & kill switch and a locking clutch lever. Your rear brake lever needs to go somewhere or you could go for a double cable right lever, eeek! The handlebars are going to get pretty cluttered with all the controls.
Out of the box petrol motors have you clamp the rear sprocket directly to the back wheel spokes around the hub using some old off-cuts of car tyres. Yes, old car tyres! However, this does sorta work a teeny-weeny bit like a cush drive. There's no freewheeling function in any of this; callback to the locking clutch lever.
The way I looked at it the bike then only had two gears: me pedalling = low gear, release clutch and use motor = gear 2. Or in our case ebike motor + pedalling = gear 1/2 and petrol motor maybe gear 3. It's a lot to juggle! Pedal + conventional gears, ebike pedal sensor? or maybe a thumb throttle, petrol motor throttle + clutch, brakes... however you go about that!
As an aside there are aftermarket kits that reroute the petrol drive output through the right-hand side gear train so you could use your derailleur or IGH but consider that the chainset is not build for the ~1.6kW of a petrol motor. My boss has a mid-drive 1.5kW BBSHD and has being through 3 chains and two rear cassettes in the last year.
Are we even getting into the electrics you'd need if you wanted to get this through the MSVA. No? Good
And you would need to get it through the MSVA as, unlike the "sleeper" nature of any conventional overpowered ebike, the distinctive 2-stroke (which, with the supplied exhaust, is borderline on the decibel limits) offers zero plausible deniability.
tl;dr
Sounds like an exciting project! Best of luck ____________________ Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter |
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