Best Motor Size to Avoid Burning Out?

[RokitL]

Hi all,

Im planning on putting together an ebike from scratch, and am wondering what would be the best size motor to go for:

- I'd like it to be able to travel comfortably at about 35 kph, without risk of the motor burning out.

- I planned on running at 48V for a nice amount of Torque (too many traffic lights in the city), and then finding a suitable controller after.

From what I've seen on forums, I'm tempted to go for a 500w motor, just to avoid risk of it burning out, but am wondering whether this is overkill?

I had been looking at the Q100/c/h, and Q128/c/h motors, but then realised that they are geared motors, which I would rather avoid, again for reliability. Can anyone recommend a good, cost effective, gearless hub motor?

Any help is always appreciated! Thank you!

 

[Deleted member 4366]

Geared motors are about the same reliability as direct drive ones. Just different problems. Neither have any significant reliability problems. In fact problems are so rare that I can't even remember the last time anybody reported one.

Instead of worrying about theoretical problems, you should just choose a motor that does the job.

 

[RokitL]

Thanks, d8veh.

I'd gotten the impression that the nylon gears can cause problem on the geared motors, but you don't think this is worth worrying about?

If that's the case, then I may go with the Q128H, as this seems to be the one that i've come across the most during my searches.

Just out of curiousity, do you know of any direct drive motors with similar performance?

 

[anotherkiwi]

I'd gotten the impression that the nylon gears can cause problem on the geared motors, but you don't think this is worth worrying about?

If you dump 2 kW into a 250 W motor the nylon gears may get upset but you didn't mention using a 35 A controller and a 72v battery...

 

[Benjahmin]

Got an Ezee geared hub with about 5000 miles of hilly west Wales riding on it. Gearbox no problem. Did have a problem with a duff bearing, but that can happen to the best.

 

[Deleted member 4366]

It's been a very long time since anybody reported worn gears. In my 7 years of working with and on geared hub-motors, I've only seen one. It was a high speed Q100, run at 48v and 20 amps, throttle only. The gears hadn't failed, but did look a bit worn.

You won't have any trouble with a Q128, which has bigger and stronger gears.

 

[danielrlee]

Gears do fail if you load them hard enough. I've destroyed the gears in three hub motors - 2x Bafang SWXH's and 1x Q128. Both the SWXH's were operating at around 1500W (melted old non-composite gears, multiple times) and the Q128 at just under 2000W (stripped gears under heavy load).

If you run them within certain parameters, they are surprisingly reliable, but my problem is that I always have to push performance to breaking point.

I have never destroyed a DD hub motor, but that's probably because I only run them with temperature monitoring & thermal rollback on overtemperature.

 

[KirstinS]

Also ruined the nylons gears in a 250w 36v 8fun

But I was running it at 48v and going up South over street in Brighton

Which is very steep , don't know ratio