Motor speed help

[marcros]

Can anybody help with this. I have a standard 2 pole motor- 2800rpm.

I need a surface speed of c2200 feet per minute on a 4" drum. According to an online resource that is approx 1950 rpm required. The motor pulley is stepped so an be 2" or 4" (there is a smaller one too but I can't remember its measurement).

What size pulley do I need on the drum? This can be anything- I plan to turn it.

Is is as simple as 1950/2800 =0.7 so 2" driving a 3" =0.66 = near enough.

Any help appreciated!

 

[HOJ]

This may be of use:

http://www.blocklayer.com/Pulley-Belt.aspx

Good website for lots of calculators

Paul

 

[woodfarmer]

Can anybody help with this. I have a standard 2 pole motor- 2800rpm.

I need a surface speed of c2200 feet per minute on a 4" drum. According to an online resource that is approx 1950 rpm required. The motor pulley is stepped so an be 2" or 4" (there is a smaller one too but I can't remember its measurement).

What size pulley do I need on the drum? This can be anything- I plan to turn it.

Is is as simple as 1950/2800 =0.7 so 2" driving a 3" =0.66 = near enough.

Any help appreciated!

yes

however, is the 2,200 fpm a maximum or normal working speed ? If maximum it would pay to slow it down some.

 

[marcros]

I saw it as quoted on another forum, but it is something that I wanted to check. There was no mention of max or working speed, and I don't know how critical it is.

But now I have the principal I can work it out.

Now to try and find a few different opinions on surface speed for sanding.

 

[sploo]

A 4" diameter drum has a circumference of 4" x PI = 4" x 3.141 = 12.566"

2200 feet per minute is 26400 inches per minute, so you'd need to spin the drum at 26400 / 12.566 = 2100rpm

2100rpm is 75% of 2800, so with a 2" pulley on the motor you'd need a 2/0.75=~2.7" pulley on the drum (or a ~5.3" pulley if using the 4" on the motor).

A 3" pulley on the drum would give 2/3=0.66, or 1848rpm; which is 1848*12.566=23221 inches per minute (1935 feet per minute).

Sounds like it'd work ok.