Thread: What sized motor to power a 100kg screw lift

Hi guys,

I am building a new stand for my homebrew kit and an important feature will be some sort of lift for raising a 50L volume of near boiling wort from ground level to about 900mm after the beer is boiled. Doing this allows me to use gravity to drain the beer from the pot, through a chiller, and into the fermenter.

I plan on cutting a 3/4 ACME screw and nut that I will cut myself for the lift and then driving it with an electric motor.

My question is, what sort of power motor should I be looking at? DC or AC? The max load would be 100kgs, and the time it takes to lift the load is not important (within reason -I dont want to wait an hour for the lift to happen, yet I also dont want it to be so fast I need reflexes like a steel trap to stop the lift before it maxes out).

Brendan

Brandon,
I would say an old cordles motor or even the whole drill would work fine, that's where I'd start....if you go with that idea it may cost you a few beers though....LOL
Ewan

Hi Brendon,
Are you sure you'll need a motor?
I'd start with a cordless drill.
I havent done the math but lifting 100kg 1meter in one minute sure doesnt sound like it would need much power.

Stuart

Originally Posted by Stustoys

Hi Brendon,
Are you sure you'll need a motor?
I'd start with a cordless drill.
I havent done the math but lifting 100kg 1meter in one minute sure doesnt sound like it would need much power.

Stuart

Power= Work/t = (force x displacement)/t = (m x g x s)/t = (100 x 10 x 1)/60 = 17 Watts (at 100% efficiency).

I've done the math and it comes out ar 12.5W.....(Can that be right?) So power doesnt look like being an issue.
3/4acme is 6tpi? thats 216 turns for 36". My cordless drill runs at 700rpm max so (if my maths is right) would lift it in around 20 seconds(at 37.5W).

Stuart

Edit, thanks Bob looks like my math was pretty close(I did cheat and use 3 feet instead of 1 meter)

What about friction, both in the screw and friction on whatever retains what is being lifted?

But shouldn't the actual figure be in newton metres rather then watts?

Originally Posted by .RC.

What about friction, both in the screw and friction on whatever retains what is being lifted?

According to Wikipedia screws are between 25 and 75% efficient, assuming a 50% efficient motor then the overall efficiency is between 12.5 and 37.5%, even so it's likely to be under 100 W.

But shouldn't the actual figure be in newton metres rather then watts?

Force (Newtons) x Distance (m) / time (s) = (N m)/s = watts

Sweet. Thanks for the input fellas. Sounds like building it to run off my cordless drill could be a good option