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### Topic: About dunkermotoren gr63x55 torque (Read 281 times)previous topic - next topic

#### PHOTOGUY

##### Jul 22, 2018, 11:32 amLast Edit: Jul 22, 2018, 11:39 am by PHOTOGUY Reason: Photos
Hi

My project is to add some support to my bicycle by adding 100 watt silent motor.(dunker motoren gr63x55)

The problem is the torque of the motor is not enough to turn the wheel by friction. (I am using 8s lipo battery)

I will be really happy if you could give an advise to increase of the torque of this motor. ( by pwm frequency, or adding magnets... without adding gears to slow rpm)

Sami

#### Robin2

#1
##### Jul 22, 2018, 12:05 pm
Image from Original Post so we don't have to download it. See this  Simple Image Guide

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

#### Robin2

#2
##### Jul 22, 2018, 12:07 pm
You need to provide a link to the datasheet for the motor.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

#### FredScuttle

#3
##### Jul 22, 2018, 12:22 pm
How will the motor be mounted in relation to the tire? Surely not the way you are holding it in the picture.
Awww! Who needs an instruction manual to use a simple chain sa......

#### PHOTOGUY

#4
##### Jul 22, 2018, 01:50 pm
Hi. Specifications are given below

It will be mounted with brackets. I am inspired by some examples on youtube

Nominal voltage   V   24
Nominal current   A   4.9
Nominal torque   Ncm   27
Nominal speed   rpm   3350
Friction torque at no load   Ncm   2
Peak stall torque   Ncm   257
Maximum output power   W   245
Nominal power   W   94.7
Torque constant   Ncm/A   6.4
Terminal resistance   Ohm   0.6
Terminal inductance   mH   1.5
Starting current   A   40
Demagnetisation current   A   33
Rotor inertia   gcm^2   750
Weight   kg   1.7

#### Robin2

#5
##### Jul 22, 2018, 03:25 pm
Your spec says the motor's normal speed is over 3000 RPM. When you calculate the gear-ratio between your tyre and the motor, how fast will the motor be turning?

Clearly if the wheel is not moving, then neither will the motor move and you will be relying on the stall torque and the stall current.

First, I suspect the motor is not designed to withstand 40 amps for more than a few seconds.

Second, I have no idea if your batteries are capable of safely delivering 40 amps.

Third, you need to calculate whether the 257 Ncm stall torque is sufficient to achieve what you need. If it is not then maybe you need additional reduction gearing. Which brings me back to my first paragraph.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

#### PHOTOGUY

#6
##### Jul 22, 2018, 03:35 pm
Thank you very much Mr Robert

#### MarkT

#7
##### Jul 23, 2018, 07:26 pm
0.27Nm with approx 1cm radius drive dog is about 3kgf on the tyre, plenty to overcome friction I'd have thought.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

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