new BH bikes

[nightrider]

I see 50cycles are selling these new BH bikes with rear motor and 500 or 600wh batteries. They claim 140nm torque, just wondering with the ebikers in the know if this is highly unlikely and is there a good chance of internal motor damage on the long run with this amount of torque. Also does anyone know apart from their bikes which they are well known, I wonder if their motors and battery would be up to same quality as their bikes. any answers much appreciated thanks.

 

[soundwave]

the guy that owns 50c is a total tosser so i would never even buy a can of coke from any of there stores

 

[artspeck]

I would say highly unlikely as some cars only have that torque. Also unnecessary and dangerous for a bicycle to be so powerful surely.

 

[Andy-Mat]

I see 50cycles are selling these new BH bikes with rear motor and 500 or 600wh batteries. They claim 140nm torque, just wondering with the ebikers in the know if this is highly unlikely and is there a good chance of internal motor damage on the long run with this amount of torque. Also does anyone know apart from their bikes which they are well known, I wonder if their motors and battery would be up to same quality as their bikes. any answers much appreciated thanks.

Such high torque is to my mind MOST unlikely (Impossible?).
Furthermore, the higher the torque on a bike motor,the more likely is that the fixed (to the rear forks) part of the motor, will turn and rip out all the electrical connections, leaving you with at best a costly repair, or even the need to replace the motor completely.
I have just noticed that the seller is claiming that the bike has a similar torque to a 2 liter VW diesel motor, so he really is a stupid tosser.....being nice!!
AVOID LIKE THE PLAGUE!!
regards
Andy

 

[EddiePJ]

There are two bike brands that I wouldn't touch with a barge pole, BH being one of them.

Once bitten twice shy and all that.

.

 

[nightrider]

thanks for the response guys saved me a few bob

 

[vfr400]

The motor runs with 48V, so straigh away, it has a 33% advantage over a 36V one. It looks like a fair sized geared motor. I have similar motors at 48V that can put out around 100Nm, but they have a 5:1 internal ratio. Modern motors tend to have larger reduction ratios, so with 8:1 or 12:1, 140Nm would easily be achievable.

To give you some idea, a Bafang BPM or CST wound for 30 mph running at 48v makes around 95 Nm at 35 amps, so if you increased its internal ratio from 5:1 to 8:1, it would make 152 Nm and have a top speed of 19 mph.

35 amps is pretty high and would require a large controller and a strong battery. This is the bit that doesn't quite match that BH bike. I would think 20 amps would be more like it, which would bring the torque down to 87Nm, however, the ratio could be increased to 12:1 and a higher speed winding used, so 140Nm is not impossible. It would only require 22 amps.

 

[vfr400]

Such high torque is to my mind MOST unlikely (Impossible?).
Furthermore, the higher the torque on a bike motor,the more likely is that the fixed (to the rear forks) part of the motor, will turn and rip out all the electrical connections, leaving you with at best a costly repair, or even the need to replace the motor completely.
I have just noticed that the seller is claiming that the bike has a similar torque to a 2 liter VW diesel motor, so he really is a stupid tosser.....being nice!!
AVOID LIKE THE PLAGUE!!
regards
Andy

I think you're misunderstanding something. The car's torque is measured at the crank at thousands of RPM. The torque at the wheels is substantially higher. That BH bike has a hub-motor, so the torque is measured at the wheel.

At 7mph, the car's wheel turns at approximately 50 rpm. Let's say the car has 100Nm torque at 2000 motor rpm, so in first gear the ratio is about 40:1, which would make the torque at the wheels 4,000NM. Each time you go up a gear in the car, you reduce the torque. Say you can do 70 mph at 2000 rpm, that would mean that you get a maximum torque of 400NM at the wheels at that speed.

A Tesla car has 5,826Nm torque at the wheels.

This is also something that people don't fully understand with crank-drive bikes. Each time you change to a higher gear your torque goes down as your speed goes up. When Bosch or anybody else quotes a torque, it isn't a real figure because it would be different for every bike depending on the gearing. If you got 60 Nm in bottom gear with 32 teeth, you'd only have 20Nm in top gear with 11 teeth.