Poll: Has your front hub motor spun out of your forks?

[Blaze]

It looks like a lot of kits are shipping without torque arms to keep the axle from spinning, or safety retainers to keep the front wheel attached if the nuts come loose. This can result in the front wheel falling off, if your motor has enough torque to spin the axle.

Manufacturers are telling me that if the wheel comes off, it's because I installed it wrong. Common sense tells me that you just don't put that much torque on the center of an axle.

I haven't seen too many rear hub motors, but this poll is for the front hub motors only, since that is the kit I am worried about. Also, please let us know what kind of motor you have (high/low speed, high/low torque, voltage, watts, manufacturer, etc...)

 

[Blaze]

my kit

Mine has spun out of the forks. Hopefully, I have it fixed. I will post the info on fixing it when I get it put back together and tested.

My motor:
48v
600w
About 17/18mph actual top speed (advertised top speed was 24mph)
High torque- climbs medium hills without pedalling and very steep hills with little pedalling effort
Manufacturer- China Gas (via Don Grube), purchased from Spookytooth Cycles
It's a silver motor with red rings painted on it.

 

[Wheels]

Blaze would someting like pictured make a good torque arm or is it too heavy?

wheels

 

[gone_fishin]

wait a doggone minute...a poll i can't vote in...what's up with that? :/

 

[Blaze]

Wheels- that might not work too well. It's not how heavy it is, but how thick. You only have so much axle space to use up. I will post photos of my finished torque arm in a day or two. It's made out of a 10mm wrench from ace hardware. It's cheap, light, strong, and fairly thin. What you want is something that has flat surfaces to hold the flat spot on the axle. You want to think about how a coaster brake arm works when you build a motor torque arm.

Augi- Sorry you can't vote on this one. That's what I like about having one gas bike and one electric. It's like being bilingual.

 

[Wheels]

So you have chosen forged steel for the arm, would not plate steel be thinner? Like to see some photos when you get it hooked up. Your art of problem solving is interesting.

wheels

 

[Blaze]

Yeah, plate steel would be great, if you have something to cut it with (all I have is a dremel w/cutting wheel). You would want something about the same thickness as the coaster brake arm. The wrench idea is just fast and easy because the wrench is already a good shape for the job. If you had plate steel that was roughly the same shape, but as thin as the brake arm, that would be the best solution by far. Especially since the wrench has to be modified so it sort of locks onto the axle and doesn't slip out. The wrench has an open end that slides onto the axle from the side. The plate steel could be cut with a closed end that could never slip off. I'll get some more photos up this weekend for sure. And I'll draw a quick template for the plate steel torque arm, too.

Meanwhile, this drawing was the concept for my current torque arm.

The final build is pictured below. I basically went with the planned design, but it was too hard to grind a slope on the axle, so I ground the whole wrench surface flat and just left two raised tabs on the ends. This way, I only had to grind two small notches into the axle instead of the whole slope. Installation and testing is tomorrow.

 

[Wheels]

Why not just use a brake lever?

 

[Blaze]

The hole in the end has to be shaped to get a tight fit on the axle to keep it from spinning. That brake arm in the photo would be perfect if it had a hole the exact shape and size of the axle, instead of a big square hole. A brake arm like that was the very first thing I wanted to use, but the hole just wasn't the right shape or size.

 

[gone_fishin]

so, the axle has a flat/square section? anyone have an actual pic for us?