Hoist info. ?

[kez]

I'm thinking of making a small hoist that would lift a little over 1000 lbs 9'6". Could anybody confirm if a 1/3 hp motor would do this in one minute? I think I have two options for the electic motor - 1725rpm & 3450 rpm.Below are my thoughts. Thanks for your help. Al

Math for Hoist
Question 1 : Determine horsepower (electric motor) required to raise appoximately 1000 lbs up 9.5 ft in one minuite.?
Ans.: 1/3 hp eletic motor.

Horsepower Formula is 330000 ft.lb/min = 1 hp

Question 2 : Determine gear ratio to accommodate 1/3 hp electic motor @ 1725 rpm
Ans : 106 : 1

load moves 7" per rotation of hoist drum with a cable. 9'6" requires 16.8 rotations.


Question 3 etermine gear ratio to accomadate 1/3hp electric motor @ 3450 rpm

Ans :212 : 1

load moves 7" per rotation of hoist drum with a cable
9.5 ft = 114 inches
114 " requires 16.28 rotations of 7drum ( 114" / 7" = 16.28 )
212 : 1 ( 3450 rpm/1628 rotations = 211.9 )

 

[Charles (in GA)]

Buy a half ton hoist, much easier and safer.

Charles

 

[Anonymous-0]

Yeah- a brake would be nice.

 

[kez]

Thanks for your opinions. I realize where your coming from. The purpose of this hoist is not the regular one. I plan to have a brake, two cables, etc for safety. I just need my questioned confirmed.

I'm almost smart enough to know how stupid I am !
Thanks again for your input. Al

 

[Anonymous-0]

If you're lifting something up, get a certified hoist designed for lifting. You could probably make something that would work fine but if it ever failed, you'ld have a big lawsuit and no chance of winning. Buying a commercial hoist would probably be a lot cheaper anyway. Dave

 

[LilFarmer]

Hi Kez,

Yes, I believe your arithmetic is correct, BUT I am going to give you some more food for thought!

First, I don't want to know what you are going to lift or move with whatever contraption you are building. I would, however like to know how you plan to drive it? Belt, or chain, or gearbox?

Is the 1000 lb load going to be constant from startup?

To get a 106:1 ratio using chain or belt is going to require some parts that are custom made and very pricey, same with a gearbox.

By using some jackshafts driving other jackshafts you can accomplish your drive ratio,using off the shelf parts, but it begins to get bulky.

I also don't believe a 1/3 horse motor will have any where enough starting torque to move 1000 lbs from a dead lift.

Just my 25 cents.

 

[Pooh Bear]

(quoted from post at 19:18:08 11/05/07)
Horsepower Formula is 330000 ft.lb/min = 1 hp

You got one too many zeros in there.
It's 33000 ft-lb/min or 550 ft-lb/s = 1 hp

Pooh Bear

 

[kez]

Hi LilFarmer,
It takes a LOT of food for thought, especially for a first time project.

I have a small collection of parts on hand; so far I thought of going with a chain drive but haven’t excluded using belt or gearbox.

The load would be constant.

That point about starting torque? I am thinking that the motor would need a chance to get up to 1750 rpm to develop full torque and would need to develop quite a lot of rpm to start the load. Also, if the load stopped I wouldn’t be able start it again.


Your 25 cents is worth a million! Thanks