[alberg30] Winch Power Ratio (Corrected)

[Guy Lalonde]

From: Guy Lalonde <lalondegc at videotron.ca>

I may have induced the list into error about how to determine the power ratio of your winches. Thanks to Bob Johns for pointing it out.

So for anyone interested here goes.

Some manufacturers winch numbers represent the actual power ratio and others' only represent a model number. This is how you can find out the power ratio of your winch and if you have a 2 speed what is the power ratio of the other speed.

Most manufacturers quote the power ratio of their winches using a 10 inch winch handle. In stores you will find 8 & 10 inch handles. So if you are using the shorter one your actual power ratio will be less because you have less leverage.

First determine the gearing ratio of your winch. Count how many turns of the winch handle it takes to turn the body of the winch one turn (this is where I made a mistake, I had said it the other way around in my previous note). If it takes 5.5 turns of the winch handle to turn the winch body one turn, then gear ratio is 5.5 to 1. If it is a one to one relationship then your winch is not geared, ratio is 1 to 1, the mechanical advantage comes only from the difference in the radius of the drum and the radius of the winch handle.

Then calculate the power ratio:

(gear ratio    multiplied by    winch handle length in inches)    divided by    radius of the drum in inches

the drum being the part where the sheet winds around the winch

If your gearing ratio is 5.5 to 1, your winch handle is 10 inches long and the radius of you drum is 2 inches then

(5.5 x 10) / 2  = 27.5 to 1 is your power ratio

If you were using an 8 inch handle on the same winch, your power ratio would be 22 to 1, a decrease of 20 %.

If your winch is 2 speed, determine the gearing ratio when turning in the other direction and redo the calculation to get the power ratio for that speed. A lot of 2 speeds are geared in one direction only and not in the other (1 to 1 gear ratio). Larger and more expensive ones are geared in both directions.

Guy
Cyrena #466




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