Single speed E-BIKE advice

[eugene]

Can anyone advise me .

I have been given a bicycle and am in the process of building a E-bike from the ground up . The frame I am using is a superb Ishiwata 022 tubed frame which I have had powder coated .

From BMSBATTERY I have ordered the following . Bafang QSWXK-Front E-Bike DC Brushless Motor , E-Bike 36V20AH LiMn2O4 Pack with charger & Alloy 05 Case and all the other bits to go with it .

While in the garage yesterday starting to polish bits and put bits back on the frame , it struck me as to why am I putting on a deraleaur and front shifter ! . Would it be more efficient running a single speed bike using the Motor power to make up the deficiency in my strength ? The obvious advantage being a far lighter bike possibly as low as 8kg + another 8kg for the battery , controller and motor = 16kg in total and also a much simpler and reliable setup .

My question , if anyone can help is would a 250w motor provide sufficient power to compensate for the loss in gears ?
Is this the way to go or should I stick with a 10 speed bike .?

The bike is for Road use only with not to many hills just slight incline all the way one way . Journey 15miles return with no opportunity to recharge

 

[BenMoore]

Personally, I would test your system out with rear gears, then remove them if desired. The optimum gearing set up will depend on so many things - riding style, terrain, and the characteristics of the particular motor - that it's hard to know in advance.
I think that having a range of gears on the back would make it easier to determine the best gear for an eventual single speed set up anyway.

Ben.

 

[Drunkskunk]

The motor you listed is new. we have a few people here about to test them, but nothing conclusive yet. 250watts probably won't replace all possable gears, though.

But that said, plenty of people prefer single speed human powered bikes to multi speeds. I don't currently have a working shifter on my 500 watt bike. haven't needed it, so I haven't bothered to fix the cable. I never installed the front derailer at all on that bike. I knew at the time I would never need it.

 

[gogo]

The obvious advantage being a far lighter bike

The weight savings if calculated as a percentage of the system (you+bike) is of almost no consequence. The ability to efficiently add human power is worth the small extra weight.

 

[torker]

Keeping some gears is probably a good idea. Mine stays in high gear now with 500 watts "unless" I run the battery down a couple miles from home. Then the old gears come in handy.

 

[deardancer3]

Muti chainrings in the Front probably not needed.

With a single speed hub motor, you should read some of the tests relating how moderate pedaling in the right gear helps with hills, Decreases peak battery drain, saves batteries, increases range. nothing magic, 40 thru 90 gear inches quite enough.

my opinion.

d

 

[Russell]

I run the little 250W geared motors and believe me unless your local terrain is as flat as a pancake you will want those gears to help the motor up steep hills and to travel at speeds above the capability of the motor.

I pedal all of the time on my E-bikes and like to keep my cadence in a tight range (90's) so gears are essential. Both of my bikes use 12-30T 8 speed cassettes in conjunction with 39/26 or 42/30 chainrings on triple cranks with bashgaurds taking the place of the large chainwheel. I use all of the rear cogs but only need the 30T ascending a 12% grade or the 12T when pedaling over 25 mph. I never have to move to the smallest front chainwheel unless the motor fails so a 1 x 8 set-up would actually fill my needs. With less hills I could see using even fewer gears but I'd still want some. I would consider one of the internally geared rear hubs if you have a single-speed frame or if you want a simpler system.

-R

 

[dogman dan]

Keep all the gears. It's not that much weight. But one day when the motor won't work, or the battery dies you will want that lowest gear again.

If it's really all that flat, mabye you could get rid of the front deraliur and go to just one chainring. I end up riding in one gear 99% of the time, but on different bikes with different motors it ends up a different gear So keep the gears till you sort out what gears you like to use.

I took off the front derailur on my commuter bike, but kept the chainrings. When shit happens, I can just stop and pop the chain onto a lower front chainring and slog home. I need that lowest gear bad if the bike breaks while I'm still down in the vallery. The bike is 85 pounds, so who cares about another pound one way or the other. On the commuter, all kinds of stuff is weighing down the panniers, tools, water, warm clothes I needed in the morning, dinner.

Another thing I've noticed, the bus comes by only once an hour, but the breakdown is allways 5 minuites after it just went by. In the low gear, I can pedal home quicker than waiting for the bus.

 

[eugene]

Well I didn't expect such reply . I will go for assembling the bike back as a original 10speed racer once done will post some photos as it will look very retro but with a twist " and go "

 

[amberwolf]

On Crazybike2, I hardly ever shift down from the largest front chainring, but I do shift around on the rear from lowest to highest a fair amount, simply due to starting from a dead stop so often during rides on the road with traffic controls. Keep in mind that on mine, the motor and the pedals go thru the same bike drivetrain to get to the rear wheel.

I *can* stay in the highest gear all the time, and the bike works fine, but it isn't good for the battery *or* the drivetrain--that's how I destroyed the front large chainring on the previous triple I had on it, and actually bent teeth tips over a bit on the smaller couple of sprockets on the rear cassette.

 

[dogman dan]

That's one nice thing about the dd hubmotors. If your battery can hack it, you can hammer the motor starting if you feel like it. I just motor to about 5 mph, but I ease onto the throttle at first. At 5 mph I can hammer the throttle and the pedals even in high gear, that's a 58 front, and 14 rear. Three hard cranks and I'm going top speed. But if I hit the pedals too soon in top gear, I'll strip out the 14 tooth rear gear. 58 teeth give the chain a lot of pull, and I have broken chains too.