Lifting speed computation 5

[mayjark]

Hi,

I just want to ask if my computation is correct for this situation.
I have an Actuator coupled with a gearbox and lifting a gate vertically using screw thread (ACME).

Gate height - 2.5 meters
SCREW THREAD - 3 TPI (ACME), 38mm dia.

Gearbox ratio - 4:1
Gearbox torque capacity - 600 ft lbs
Thrust capacity - 40000 lbs

Actuator output rpm - 73
Rated output torque - 100 ft-lbs

My computations is: Lifting speed = (actuatorRPM * efficiency / (gear ratio * TPI)

efficiency = 90 percent

So using the formula I get 5.48 inches per minute, am I correct on this?

Thanks in advance

 

[3DDave]

Efficiency isn't part of rate; it affects the amount of power required.

 

[mayjark]

So Sir 3DDave the correct formula is Lifting speed = actuatorRPM / (gear ratio * TPI)?

 

[3DDave]

Input Revs/minute * (Output Rev gbx/Input Rev gbx) * (Thread Inch/Thread Output Revs) = Thread Inch/minute


Sir Units says Yes.

 

[JStephen]

If the actuator output is independent of load, you can work out travel speed, and neither torque nor efficiency enter into that equation.
If the actuator output varies depending on the load on it, you don't have enough information as stated to determine the answer.

 

[rb1957]

is this a simple geometry question or work done ?

Is this school or work ?

another day in paradise, or is paradise one day closer ?

 

[TheTick]

First reduce the problem to an ideal state so that you know the upper limit of possibilities.

Force * speed = power --> Speed = Power / Force
Force = weight of gate
Power = torque * speed (much easier in metric)

If you know your max available power and weight of gate, you can determine maximum ideal lift speed. Any real life result will be less. If you need more speed, you must have more power. No amount of gearing or leverage can change that.

The problem is determining your actual torque and your actual power at that torque. You only have one point on the actuator's torque vs speed curve.

The other useful bit to know would be the torque required to jack up the gate. Ideal torque can be determined by force and thread pitch. If you can check (e.g. w/ torque wrench) you'll be in better shape.

 

[BUGGAR]

Similar to above, you can just take power = force x velocity. The force is 1.0+ g and the velocity is the speed in feet per minute you want it to rise vertically. This is quick and dirty and you can throw in a high and low efficiency factor to get close.