Don't Use Aluminum Forks with front hub motors!

[casainho]

So it's definitely a compromise. It's good within a certain envelope, and bad out side the limits. It works good for me for riding on dry pavement, or wet that is not too steep. It's no good for dirt riding, trail riding. You just gotta have a rear hub for that. Dual hub can be nice in dirt, but really I prefer to have a light front so I can pull a small wheelie over larger obstacles. I run 1200w max, 48v. So I burn a little bit of front tire rubber, but nothing that alarms me. You should get quickly used to a small wheel spin the first foot or so as you start. Do be cautious about going from 0 throttle to full on a corner with wet or sand. But if you are already spun up, you can power through a corner fine.

Ok, it's decided. I will go with the Bafang BPM 500W front motor on aluminum forks but using 2 arm torques.

My travel is 50km (25km + 25km to return) on flat dry pavement/tarmac roads (I live near the ocean). 2 years ago I did this with 180W front motor, 1 year after with 250W front motor and now I want to go with the Bafang 500W.

My controller gives 22A at 48V, which is 1056W at start. Since I came from a 250W motor and I just need more 50 or 100W, I will do 2 things:
- limit the maximum throttle with a circuit to 0.7, 500W*.7 = 350W
- ramp up the acceleration of throttle with the opamp circuit(or Arduino) to have 3 seconds of ramp from 0 to maximum power

Limiting the power to 350W to be safe, also because I don't have gears to go over 44km/h (maximum speed with the 250W motor were 38km/h) and I want to always pedal, also I will ride 50km with a charge but I plan to increase for the 70km/h.
I wish I could limit the power and ramp up on the controller, so when lifting to the air the wheel like on a bump, the wheel would take time to accelerate and so more safe.

I hope to survive to any possible accident due to front motor and have the chance to change for rear motor

My actual electric bicycle is this one (V2.1 in Portuguese):


It is a Cute-85 motor for 16'' but installed on a 26'' wheel, 250W, 24V. Battery 24V 25Ah.

[amigafan2003]

This carbon fork with alloy dropouts and a front motor will make many of you cringe then



Just passed 1000 miles on it.

[casainho]

This carbon fork with alloy dropouts and a front motor will make many of you cringe then

Just passed 1000 miles on it.

You are pushing your luck by not using arm torque. You don't know if you are near the limit.

[dogman]

It would make me cringe if it had any power. Properly installed, nut torque alone is proven to provide enough resistance for lower torque levels. And I do see a torque arm.

One thing to note, Sometimes the wider width at the cover common with gearmotors will not fit between the tubes of a suspension fork. You need the type of fork that has the dropouts mounted to the inside of the tube. Many forks have the dropouts centered on the fork tube, and typically the motor cover is too wide to fit. Usually a 9 continent dd motor will fit most forks. It's narrower at the cover, but sometimes still rubs on the bearing housing of a tight fork.

So measure it before you order.

[casainho]

It would make me cringe if it had any power. Properly installed, nut torque alone is proven to provide enough resistance for lower torque levels. And I do see a torque arm.

Sorry for my mistake amigafan2003, now I see you are using torque arm.

One thing to note, Sometimes the wider width at the cover common with gearmotors will not fit between the tubes of a suspension fork. You need the type of fork that has the dropouts mounted to the inside of the tube. Many forks have the dropouts centered on the fork tube, and typically the motor cover is too wide to fit. Usually a 9 continent dd motor will fit most forks. It's narrower at the cover, but sometimes still rubs on the bearing housing of a tight fork.

So measure it before you order.

dogman, thank you for sharing. Are you suggestion me to measure before order? If so, I already ordered 2 pairs of BMSBattery arm torque and a KU93 controller (current is KU123, the one that broke the alu dropouts).
I don't know if BMSBattery arm torque are good and if they will work, but before ordering I were ready to make myself them so I will verify and think the BMSBattery ones and if needed weld them or the steel sheet I will use.

[dogman]

I was talking about measuring the motor itself. Moot point if you have it already and it fits. Depending on the fork design, some motors are too wide for the forks. The dropout is still standard 100mm, but the measure between the two tubes might be only 80 mm. So the motor won't fit between the two tubes.

[amberwolf]

Sometimes the wider width at the cover common with gearmotors will not fit between the tubes of a suspension fork.

Yes, the first Fusin I got from you fit fine on DayGlo Avenger's cheap RST Omni fork. But the cover fasteners on it were domed phillips screws, and those on a second Fusin from you were taller squared-profile allen-head bolts, which would only fit if I took the lockwashers out, on one side. Why they fit on the other side I dunno, but they cleared fine there.

So even the very "same" motor from the same company may not always fit! And it might not be obvious why it doesn't fit at first, either. The Fusin was obvious, as it clicked on each bolthead. What wasn't obvious at first was that the suspension would "stick" once it went down, and not rebound, so the next bump wasn't absorbed as well or at all, with the spacer in there. Eventually it wore inside the fork enough to work normally again, probably less than a hundred miles.

[amigafan2003]

This carbon fork with alloy dropouts and a front motor will make many of you cringe then

Just passed 1000 miles on it.

You are pushing your luck by not using arm torque. You don't know if you are near the limit.

I am using a torque arm - look closer

EDIT: I see you've noticed

It would make me cringe if it had any power. Properly installed, nut torque alone is proven to provide enough resistance for lower torque levels. And I do see a torque arm.

Yeah, it's only pulling 750w max.