sizing DC motor

I am trying to size a DC motor and need some assistance as to how to
do this.
The mechanism I am designing will be a 'drop test rig' for a product of
ours (stress analysis & destructive test). Essentially, it will be two
#80 chains running vertically on sprockets. On the chains there will
attachments that will pick up a car which is running up an I-beam to a
pre-set height where the car will disengage from the chain attachments
and drop down and impact on a platform.
I want the chain to be moving relatively slow (24"/sec), however I will
want some control over the speed.
The load it will have to lift will vary between 300 lbs (136 kg) - 600
lbs (272 kg).
Any information would be appreciated.
Marc Rigollet
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Let's suppose the chain lift is vertical and the max load of 272kg ascends at 0.6 m/s. Let's suppose the gear reduction and motor are 85% efficient overall. Then the motor power needed is force X speed / efficiency% = power required.
In SI units there are no nuisance conversion factors, so it's just 272 kg * 9.81N/kg * 0.6 m/s / (85/100efficiency) = 1884 watts
If 0.6 m/s is the max speed desired. Else you scale the power requirement with the speed ratio.
OK 1884 watts is a shade more than 2.5 HP, so a 3 HP motor would meet the spec. A speed controller is also needed.
There might be better ways but a thryristor controller on the AC input followed by a transformer rectifier would be one way.
Brian Whatcott Altus OK
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Brian Whatcott

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