Power requirements for a lift 1

[Kristianx2]

How can I calculate the power requirement (winch, motor size) given the safe working load and the tare mass of a man cage? Thought of using F=m.a and Power= F.V. Am I on the right track? Any help will be appreciate.

Regards.

Kristian

 

[HEC]

An alternative would be change in potential energy (m.g.delH) to give a change in joules then divide by the rate of height change (hoisting velocity) this would give watts (J/sec)

Mark Hutton

 

[tygerdawg]

Web search for "Smart Motion Cheat Sheet" PDF file. Use the equations therein to calculate peak torque requirements for your mechanical system. Similar equations, examples, and methods can be found at the "Application Engineering" section of most gearmotor manufacturer's websites.

The design of these "man lifts" of which you speak are governed by various standards for safety reasons.

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com

 

[TheTick]

I always get a sick feeling when first-time posters start w/ sub-basic questions for projects that could kill people.

 

[IRstuff]

If you have no one who is supervising you on this that knows anything about the design process, you need to [red]STOP, NOW[/red].

This is not something for a rank beginner to attempt; a design mistake on your part could result in injury or death.

TTFN

FAQ731-376

 

[EngineerTex]

I'm with TheTick on this one.

You're going to need a specifically-designed hoisting winch and an engineer. Your equations are fine if you're doing homework for a high-school physics class. The power requirements are going to be a function of how fast you raise the man-rider and which wrap of cable is on the winch drum, not to mention motor efficiency and motor type since some motors don't handle full load at stall. Further problems with the question involve what you're going to do to lower this contraption. Do you have an adequate resistor bank for dissipating all this energy you have in order to attain a controlled descent? Google the NEMA motor plates on a 1-hp motor. If your winch has a 1-hp motor on it, remembering that 746W=1-hp, you would know that that for 120V line current, according to the equations you're using, you would end up with sizing your circuit for a max draw of 6.2 amps, implying a 10-amp breaker and THIS IS NOT THE ANSWER.

This question is not within the scope of this forum.

Engineering is not the science behind building things. It is the science behind not building things.

 

[zekeman]

Homework??
If not, I agree with the others. Stop, get some schooling and tell your boss to get a consultant-- not necessarily in that order.

 

[Kristianx2]

The system is already in place. We just want to buy a standby motor, unfortunately the company that supplied the current motor is no longer in operation and the namplate is ineligible. We need a point of reference when getting in touch with suppliers.

Tnx.

 

[EngineerTex]

Whew. That is comforting to know.

I don't think that you'll have any choice but to remove it and take it to a motor supplier or rebuilder. The power requirement is fairly far down on the list of what you will need to know to replace this motor.

The following features may easily differ between two motors with identical power requirements and outputs:

1) Type of motor
2) Number of phases
3) Number of poles
4) Line voltage
5) The face and bolt pattern
6) The shaft diameter
7) The shaft length
8) Whether or not the shaft is tapered
9) The foot mounting style/pattern

Without the nameplate, most of this information will be a shot in the dark. If you don't pull the motor out to look at the shaft and determine what type of motor it is, there's no way to know the rest of this info.

But to address your burning question, the amount of power required for your system can be calculated simply by your equations or the others posted above. But I don't think that the answer would mean anything. Many of these systems use strange and exotic (to us mechanical engineers) setups to control the lowering of the load. Some motors don't take kindly to being back-driven. Some motors might be ok and some may not be. The resistor bank may not be connected to all phases of the motor. This would require a motor that could be significantly oversized for the lifting application while only barely adequate for the lowering. Without knowing the design of the rest of the system, calculating the ideal power requirement is just a guess. This doesn't even take into account whatever is going on between the motor and the wire rope.

Bottom line is that you would need to take it off and have a qualified technician look at it.

-T

Engineering is not the science behind building things. It is the science behind not building things.