350watt BB drive ebike

This is my e-bike project for the winter!Having seen cyclone kits i wanted a chain drive system having been previously very disappointed with a 200w hub motor (legal limit here in sunny old england)

The bike is a piece of junk really, one of those made to look good mountain bikes where nothing works and you end up upgrading every component because when one fails you have to replace a whole lot!Light aluminium frame though, the shocks are a joke though!No breaks on the rear as there is no rim brake mounts (how rediculous!)





The 350watt scooter motor is mounted to the frame with u bolts i made from threaded rod, currently there is an 11 tooth sprocket on the motor and 68 on the BB, waiting for the 80 tooth to come.It has a cyclone crank and freewheel, greased as it wasn't from the factory!

Started the project with great optimism but now i'm beginning to think of all the problems!Ultimately with all the reduction it will be about 10:1 at most and i'm thinking this isn't going to be enough!Am i just being silly or will it be way to overgeared? I am not expecting it to go up any significant hills at all, infact its pretty flat where I live (maybe 1:100, 1:50).

The bike will have its first 24 tooth chainring functioning, but i'm only planning to pedal up steep hills without motor at all and on the flat, gentle hills i willl be using the motor only.

Planning to have 2 18AH AGM SLA batteries on a pannier rack at the back, also the bike is going to run a YK40 yiyun 28 Amp controller

Please somebody tell me if it's imminent failure before i waste anymore money on this project!

Hi Andy,

Yes it is a bit over-geared at the moment..... even with the 80t.

I've assumed the motor speed is about 2500rpm

Is the 24t chainring the one that you'll use?

Yep, so it will be 11 tooth to 80 tooth then 24 tooth to 28 tooth, i'm going to try and get a 9 tooth sprocket for the motor, or i will have to reduce the front chainring to 14 tooth or something, but then pedalling is completely pointless!

I think I would go larger than 80t, too - you can get sprockets up to 125t.

That would be perfect!Any idea where i can get a 125 tooth?i had to order the 80 tooth from TNC scooters in the US!Otherwise no idea what to do!

Medway list a 125t sprocket:
http://www.medwaypt.co.uk/power_transmission.html

SDP in US list 120t:
https://sdp-si.com/eStore/

These are unrelieved plate sprockets, you might want to get someone to mill them out a bit, to reduce the weight.

The other possibility is to get Chris at Highpath to make one up to fit to your bolt pattern:
http://www.highpath.net/cycles/index.html He can do non-cycle chain pitches [the pricing only relates to 1/2" pitch].

The TopHat supplier may be able to provide a 125.

http://blog.myspace.com/index.cfm?fuseaction=blog.view&friendID=53429708&blogID=334583408

No. of Teeth/Cost (USD)
--------------- -----------------
26 to 39 / $37.50
40 to 46 / $39.50
47 to 53 / $43.50
54 to 57 / $46.75
58 to 60 / $49.75
61 to 72 / $54.50
73 to 80 / $67.50
Above 80 / Call or write

Anodized Color - Add $15.00 per sprocket
Hard Coat - Add $20.00 per sprocket

$12.50 Flat rate shipping to Lower 48 States for up to 5 sprockets (mix or match). Products will be shipped genearlly within 3 business days.

Australia : USPS Priority Mail in flat rate envelope (up to 2 lbs) is $16.50 (includes $66.88 insurance)...For tracking number add $13.50

Canada : USPS Priority Mail in flat rate envelope (up to 2 lbs) is $17.50 (includes
$66.88 insurance)....For tracking nuimber add $13.50.

Write for shipping to other areas.

Special Notes:

At no additional charge we can (just let us know):

1) Enlarge the center hole to 1.75" to better work on
coaster brake hubs or other hubs requiring
additional spacing

Click to expand...

Good thinking TD, I'd forgotten about Kings.

Might be worth their while to do a batch and put them on their ebay store.

Miles said:

Might be worth their while to do a batch and put them on their ebay store.

Click to expand...

I'll send him a link.

Finally got the 80 tooth sprocket!Installed and ready to go, just waiting for my 2 SLA 18AH batteries and the pannier rack they are going to be mounted to, then it will be up and running!Gear ratio is now 8.5:1, should be ok providing the motor has enough torque at 30 amps and below

Thanks for all the help on the 125 tooth sprockets but it seems they need machining or if they are machined already they cost a small fortune!

Run into (yet another) problem, if you try put the bike into gear 3 and above the bike chain hits the drive chain, i need that longer BB shaft, how annoying!Kind of defeats the whole object of having the motor in front so the gears can be used as well!Anyway once it gets up and working and i think it's worth going on with the project then i'll get the bigger shaft.

Are you using the whole scooter drive chain/controller/throttle on this?

yeah just a regular brushed 350 watt controller and throttle!The chain is #25 6mm scooter chain

So why isn't the "geared version" of the 350 watt motor being used? I noticed there is a 450 watt version also. Seems like everyone's using jackshafts, gearboxes, etc. I assume just more amps wasted without the gearbox or maybe you don't really need them?

The geared version would practically bolt right on and be able to run a stock bicycle chain. That's what I'm using... I will go direct pull from the motor to the rear wheel and then run the chain past the front chainring which has a front freewheel built into it.

That would have been my first choice but unfortunately no one sells them in the UK and if i had to buy one from the US i may as well just buy a cyclone because it would cost more to import it!