Haha, yeah. Nylon is great because it keeps the metal bits from wearing, allows them to be softer and lighter materials like alu, prevents shavings from spreading and grinding bits, and they’re quiet. But they lose strength at not too high temps. Beefier nylon gears can have enough strength even when softer. E.g. the helical gear of Bafang BBSHD which people regularly run 1kW through. Some people used to put Delrin (Teflon) gears in their motors, but I don’t think production motors have ever done that. These gears from the pic are tiny with small, helical, teeth. The front version of this motor is 1.8-1.9kg. Whenever you see a bike with a small hub, smaller than a typical disc rotor, front or rear, it almost certainly has similar sized gears. I also have a Shengyi with similar parameters to the G310 and it has almost identical design inside.

Not quite. Just ran a couple of simulations with the motor I use. If you run a Bafang G310 at its nominal power of 250W at 5% incline, it would reach 150°C in 25 minutes. Its gears are nylon which soften and lose a lot of their strength well before that - in the 65-85 range. Their teeth would strip under power well before the motor reaches 150°C. At 10% incline it overheats in 5 minutes, gears would strip in less. If you run it at 500W on 5% incline and many controllers would give it that much, it would overheat in 12 minutes. Even on flat ground, I can get mine to 85°C by riding hard at high speed with the motor at ~450W in under 45 minutes. If then started climbing a steep incline with the same power and low speed, I’d very likely strip the softened gears. A friend stripped his this way. This is what they looked like:

You can see how the stripped teeth are at the motor rotor shaft end, which is one of the hottest parts of the motor.

A beefier motor like the GMAC can withstand 5% grade at 500-700W of power without overheating. Perhaps without losing teeth too since its gears are significantly stronger even if still nylon. 10% at ~650W would kill it under 13 minutes.

So it depends on a few variables but especially small motors aren’t difficult to “melt their gears of” by which I mean soften enough to strip under load.

Must be a mechanical coupling of some sort.

Oh yeah, you don’t need more than 500W for climbing if you pedal. That said, if you ran a small hub of the 2-2.5kg range at 400-500W at low speed, like when climbing, you’d overheat it and melt its gears in minutes. Ebikes.ca have a nice motor simulator that can pretty accurately estimates how long it takes for many different motors to overheat.

What’s the motor?

I’ve used KMC X11e/e11 ever since this disaster. No broken chains and they last very long on non-ebikes too.

Hahaha. What chain and cassette?

The ebike world isn’t getting away with calling this a bicycle. This was a custom designed mid-drive made by a crazy guy that wanted to shred offroad. This contraption would never pass any legal certification for an ebike. I don’t think he made more than a few hundred of these before he stopped making them. In fact that was part of the reason I switched to a small hub. It was lots of fun but both illegal and unsafe. Going over 55kph at the push of a button is not something you want long-term. Accidents happen and the energy the body has to absorb coming to a stop grows exponentially with speed so…

E: The most powerful version was 6KW. Here’s a guy riding it, limited to 4KW.

That motor was outputting 1500W at every start from a dead stop and often for extended periods during cruising. That motor was actually 3KW but I had it limited due to the max battery current and the insufficient size of my balls. That said I’m pretty sure grinding was a major contributor too. :D

The very first time I rode this, I hadn’t limited the power, I pressed the throttle and the bike escaped from under me by doing a violent wheelie.

Both mid-drives and hubs are great. The main differences come down to weight distribution and climbing ability. Climbing ability is significantly better with mid-drives because they can use the bike’s drivetrain to achieve higher speed reduction and therefore higher torque. This allows a mid-drive to exchange bike speed for torque which makes it able to climb steep inclines. Hubs generally come with a fixed gearing or no gearing at all. The highest reduction hubs come with 13:1 gearing which is much smaller than the effective gearing a mid-drive and drivetrain can achieve. The lower the gearing ratio, the larger and heavier the motor has to be to achieve equivalent torque. Which brings me to weight distribution. Mid-drives sit low, in the middle of the bike which doesn’t significantly affect handling. Hubs add 1.8kg at a minimum to one end of the bike. 1.8-2.5kg on the lower end is noticeable but it isn’t horrible. Larger hubs are more noticeable. Many hubs are in the 3-5kg range. On flat ground or low inclines, there’s no significant differences in the behaviour of a small hub compared to a mid-drive. Both feel great.

Another important difference is the ability to shed heat. Most hubs shed heat poorly and overheat if pushed hard at low speed over many minutes. Some are better than others. Mid-drives are better at that and typically have internal temp monitoring and control.

Both hubs and mid-drives have special requirements around frame mounting. Most mid-drives need special frames. Hubs require strong dropouts, and/or torque arms. Installing a hub on an aluminum frame is only safe without atorque arm in the rear. And even then you may start mangling the material when cycling the nuts at 40-50Nm as required.

Hubs generally require less maintenance as tbey don’t wear your drivetrain. Direct-drive hubs should be almost indestructible as they have no internal gears to melt.

Factory mid-drives like Bosch, etc. require authorized service to repair so DIY is no-go as far as I’m awarr. Hubs don’t. This is the main reason I’m riding small hubs (Bafang G310). I can repair any part of the system myself. If the hub goes, I can replace it with another, even different hub and get the rest of the system to play nice with it.

In the end, if I were not into bike DIY, I’d probably buy a factory bike with a mid-drive. And if I wetr into DIY, then it depends on the application.

True but this is definitely not wax. 😄

Shimano SLX rear and a Race Face front were durable enough for it. KMC X11e was strong enough to go without going clunk. Funnily I still ride the same SLX M7000 cassette I bought for that bike. I replaced the 11s gear once as that got worn. I stopped riding that monster in 2017-18.

The peak torque was similar to pushing standing on the pedals, a torque a chain must sustain, but not necessarily for extended periods. This motor could sustain that torque for as long as the battery lasts. Production motors these days can do similar peak torque during start from a stop but don’t sustain it indefinitely. I think the Tangent was geared to do about 120Nm. The new DJI does 120Nm for half a minute. Bosch has a few models that do 100. After trashing that chain, I switched to ebike-specific model from KMC. Never had an issue with it and lasted thousands of km on that monster. I now ride all my bikes with X11e EPT / e11 EPT even though I don’t use mid-drives anymore. It lasts a lot and it handles a lot of abuse and neglect.

Is DC special or can he put any municipal police force under federal command?

Saddam Hussein’s hiding place.

Yeah, makes sense especially when using STI shifters.

Prrty!

The last bike I built is a mix, disc in front, V-brake in the rear. Works fairly well.

But I say no to mechanical disc brakes.

Hey look, we’re building a tunnel under the 403!

AirZound baby.

I do have a bell for first warning too.

In reality I ride with the assumption that pedestrians don’t hear me or see me and maneuver safely around them. So I rarely use sound alerts. The AirZound is mostly for cars.

Don’t be a savage, create users for people.

😔