adlai

Most ebike systems have basically two gear settings: the motor strength and then the gearing of the bicycle. There is a lot of redundancy there IMO, basically where the power ratios are duplicated, kind of like how 27 gear bicycles had a lot of redundant gears.

It appears to me that it makes the most sense to just have a giant ebike hub motor (that can also do regen) and have an optional single speed gearing. The motor would do most of the work, especially on hills., while the single speed gearing would be used on flats or downhills.

My current ebike has 250watts middrive. I guess like a 750 watt or 1000 watt or even higher hub motor combined with a 42:20 single speed chain ratio would be a good idea?

Smaug1

I wouldn't call it redundancy. One cool thing about eBikes (as opposed to mopeds) is that they are not too heavy to pedal, in case the motor can't be employed. Many eBikes are 60+ lbs, and would not be pedalable if they only had a single higher gear. I have one such bike in my garage now, the Lectric XP Lite. Its single gear is set up for a comfortable cadence at about 15 mph. This is a good speed for average flat terrain. Going uphill? Going to need to use a lot of juice. Going downhill? You won't be able to pedal fast enough. Having just the one gear essentially puts my speed envelope between 11-18 mph.

I have a Magicycle Commuter coming in today, also a single speed and I think it's going to be the same thing.

There are a few drawbacks to this approach:

1. No mechanical low gear, in case you run out of battery or need to climb a steep hill
2. No high gear for long, slight downhills, where I might want to go maybe 23 mph.
3. Big hub motors are heavy. They throw off the balance of the bike, which matters on a bike rack or off road.
4. Those big hub motors with regen are direct drive and are not torquey enough for climbing. Or if they are, they're motorcycle-heavy. They're more for speed. That's why geared hub motors are so popular.

I like having several speeds. I could settle for three:

• A climbing gear, set for 3-4 mph, for limping home without battery
• A cruising gear, for flat ground, set for 13-15 mph
• A high gear, for slight downhills

2old

Amen to the above! The limits for a bicycle in CA (and the US AFAIK) is 750 watts. Anything more is in moped/motorcycle designation and requires license and insurance (as well as hernia protection if you need to transport it - just kidding; my 1500w street bike weighs only 45 pounds without battery).

unterhausen

I have thought the same thing about a single speed working on an ebike. But that means you will have to pedal really slowly uphill, even though the motor might carry you up a hill. For a flat place, it might work correctly.

2old

Really good point above (obviously). People residing in most (all) areas of FL have different needs than those in San Francisco.

skookum

The boys over at High Voltage offer an upgrade kit , basically a new controller, to run the BBSHD at 72 volts and 5000 watts.
One of the guys ran his as a one speed with I believe a 1:1 ratio, 42 tooth front and rear. Don't think he actually did much pedalling on it, maybe on really steep hills.
I think that kind of system would work fine with a multi kilowatt motor and different assist levels, wouldn't need to worry about gears.

poiuyt

For information, a quite popular (at least here) e-bike startup (https://www.cowboy.com) has a bike based on this principle. Single speed with belt drive, and variable assist (the slower you go, the more assist you have). These bikes have the reputation to be fun to ride, but lack a bit of power when you have loads (hills, wind), but that is also due to the European limit of 250W.

veganbikes

We built a Specialized Como as a single speed (I think we built two of them actually) and while I enjoyed it as a single speed lover I would not want one as a main bike, just for fun tooling around on flat areas. I don't want a 3x1 bike (as in 3 gears at the front and 1 at the back) which is essentially what that bike was though it was a 1x1 in actual practice. The motor shouldn't be doing all the work and you are likely to just burn it out quickly trying to use it as your gearing instead of just shifting like a normal bike. Also there aren't really redundant gears on an e-bike sure in some triple set ups but not enough to negate the usefulness of a 3x9 set up or something similar.