Does this 29er rear hub configuration look workable?

I am building my first electric bike and just need to know if I am on the right track. I am looking at a 29 inch hard tail mountain bike. I am a big guy and like the feel of the 29 inch wheels. The hard tail is for a rack to carry a 15lb 48v 20ah Lipo battery. I am looking at a 9C type 48v 1000w rear hub motor. Can't seem to find anyone that sells this with a 29" rim so I will have local bike shop lace it for me. Reading the forum I have read that 29" wheels make for a high gear for a rear hub. Around town it is mostly flat to up to 7% grades. I will occasionally go up the canyon at a average 6-9% grade with sections from 4-21% grade. Any opinions would be welcome.

Desired max speed on level ground. 30mph
Desired max range at what cruising speed. 30 miles @ 20mph
Preferred bike wheel size 29"
Brake type of motor wheel. Disc.
Rider weight. 210
Terrain. see above.

Thanks!

If there’s room in the frame triangle I’d put the battery pack there instead of a rear rack. 15lbs sucks up high over the rear wheel IMO. Sucker will always feel funny and rough road will probably have things popping loose.

Mounted in the triangle you’ll hardly notice it’s there except when doing a dead lift. Many good frame bags out there.

I dunno 29” stuff but I’d steer towards slower speed winding for any large diameter wheel. I heard something about EBK (ebikekit.com) might have some slower DD (direct drive) motor winds available? I’d probably give ‘em a shout for advice and perhaps quote? I’ve heard they’ve got great chat help, LOL…

Most every vendor sells their motors in a 700C rim (622mm) and that's all a 29" rim is, a wider 700C rim. Most 700C rims they use have an internal width of about 19mm which is ok for up to about a 2.0" tire. However since it costs a lot more to ship a whole wheel than a motor and since most Chinese wheel builds stink it is best to lace your own or have a shop do it for you. E-BikeKit wheel builds are acceptable and they use a slightly wider rim that is recommended for up to a 2.25" tire.

The bike will definitely be tail heavy. If you're sold on the rear motor/rear battery combination you could save some weight by using a pair of 6S 16Ah MultiStar LiPo's from HK which weigh in at 8.5 lbs total. If you pedal with light to moderate effort 30 miles at 20 mph should be possible. If you choose E-BikeKit you could also go with their new larger geared motor and save more weight.

-R

This should work.
http://www.ebay.com/itm/48V-1000W-700c-Rear-Direct-Drive-Kit-Ebikeling-Electric-Bicycle-Kit-ebike-/271920373206
For that range you will need a 48V 15ah minimum pack (650wh) of your choice.

Thanks all. You have given me a lot to think about and work with. 700c it is. Also, thinking hard about the battery location and weight distribution as advised. Check out this battery:

http://www.aliexpress.com/store/product/48V-20AH-Rear-rack-Lithium-Battery-with-BMS-Charger-48V-1000W-Electric-Bicycle-POWER-Akku-Li/1714144_32293327385.html

48w, 20ah, 25A continous and ~13lbs. Looks great, locks to the rack, has all the specs I want and the price is right. I checked out K-power and it looks like they are pretty big and doing medical and cell phone applications. Could be smoke and mirrors. If I stay with the rack mount any concerns?

emotate said:

I am a big guy and like the feel of the 29 inch wheels.

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...but it is the small wheels that like the feel of a big guy
Small wheel with big tires, that is.

Buy a heavy and slow winding motor to run in a large wheel, or else pedal assist

Rack mount fine for street use IMO. Dirt another story. Off road you need to throw that rear tire around too much to ride with much more than 5 pounds back there.

Rear direct drive with 48v usually good for 30 mph, or close enough if the battery charges to 58v. But your choice is 13s, so 54.6v gets you more like 27 mph on most kits with 20-25 amps controllers.

But if efficiency up large mountains is your need, then the lower rpm motor will get you up them with less waste heat in the motor, though slower. In any case, you won't be going up long grades faster than 15 mph, unless you ante up for a 2000w motor, and battery up to a 40 amps discharge.

Check your drop out spacing before you order. I tried to do the same with a Canondal SL Trail 29er but the drop outs were 142mm not the stock 135mm. I ended up going middrive because of this.

krunchi said:

Check your drop out spacing before you order. I tried to do the same with a Canondal SL Trail 29er but the drop outs were 142mm not the stock 135mm. I ended up going middrive because of this.

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Why couldn't you add a spacer/washer? I've never seen a rear hub motor axle yet that wouldn't fit up to 145mm dropouts using spacers/washers. Plenty of axle thread.

The bitch is when aluminum dropout's = 120-130mm and your motor is closer to 145mm. That's a little too much distance to safely spread aluminum.