I have to specify a motor/gearhead combination for automating the steering
column of an ATV. The first step I believe is to measure the torque
necessary to move the wheels with the vehicle stopped on asphalt. I figure
that if I choose a motor that has that torque and a little margin, I won't
have problems when the ATV is in movement.
Here's the method I'm using. I got 20 rubberbands together, hooked at the
end of the ATV's handlebar and pulled (tangent to the steering column) as
fast as I want the motor to pull it. I chose 20 rubberbands because if I
used less, it would stretch to the limit, with 20 I still have plenty of
room to stretch. In this experiment, the rubberbands went from 3 inches (no
torque) to 6 inches (max. torque), so 3 inches of displacement.
Then I used the same 20 rubberbands to lift a weight of 30 pounds, it
stretched 9 inches (6 inches displacement).
Can I assume that the elasticity of rubber is linear in this case? If so,
then 3 inches of displacement would lift 15 pounds right?
The next thing I did was to calculate the force necessary to cause that 3
inches displacement multiplying 15 inches by g, and then multiplying by the
handlebar distance from the center of the axle.
I ended up with a torque close to 25Nm, so I'm thinking about choosing a
motor/gearhead with a 50Nm available torque. RPM should be close to 20rpm.
Does that make sense? I saw some nice motors from Harmonic Drive that would
fit my application perfectly (small, very torquey, hollow shaft), for
instance the FHA17C, but they are too damn expensive (around $2800)
I need something around $100-$200 (motor+gearhead), am I being realistic?
16 years ago