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Hello friends
sorry after long time as i was busy in selling tonewoods

now i took the project of making drum sander

i have 1 HP motor of 1420 rpm
is this rpm enough for thicknessing back and sides and tops?

i have attached 2" pulley to motor and 4" to the drum
may know what rpm will i get by this assembly?
and if want to increase rpm.. what is the procedure
waiting for ur reply

Just look at what most commercial drum sanders run at - Jet, Performax, etc seem to hover around 1700 rpm. What 'matters' is the surface feet per minute - the rate at which the paper runs over the workpiece. The Jet/Performax style open-ended sanders have speeds of about 2200 surface feet per minute, some bigger machines have variable rates between 2200 and 3200. This is easily calculated:

[3.14 x drum diameter)] / 12 x [RPM]

(circumference of a circle is 2 pi times the radius of said circle).

The relationship between pulleys is also linear: a 2" diameter pulley at 1420 RPM driving a 4" pulley will give you shaft rotation of 710 rpm, which, assuming a 5" sanding drum, is a very low SFPM figure (about 930 SFPM). If you want to increase RPM, the ratio of the pulleys (motor : drum) multiplied by motor RPM will yield RPM of the drum.

Hello sir
thanks for ur good answer
but i am sorry. did not understood anything

as i was very bad at physics in school

lol
the diameter of my drum is about 60 mm
what i understood from ur answer
is that if i want to increase the rpm i should interchange the pulley
i.e 2" at drum and 4" at motor
isnt it?
also what is sfrm ( in meters or feet)
waiting for ur reply

I have a 5in drum and run a one third HP motor at 1700 - I forget the actual ratio of the pulleys - but if your in the neighbourhood of 1700 rpm and running a 1:1 or less pulley arrangement it should be ok.... however - I would try if I were you on some scrap pieces - Im of the = if it works, it works = school of thought...
cheers
charliewood

today i interchanged the pulleys
ie 4" at motor and 2" at the drum
but the speed was too much so i did not sanded the wood
thinking of using both the pulleys of same size
either 4" or 2"
which is recommended .. 2 or 4 "
also will the 1420 rpm is sufficient for sanding?
waiting for ru replies

Hi Rahoul! There's more to it than pulley ratio. You have to consider drum size to equate the surface feet per minute.

At 60mm's you are looking at about 2 3/8" in diameter. Multiply that times pi or roughly 3.14 to get the circumference, which would be 7.42 inches. This is the distance the outside of the drum moves the paper per rotation. If you are running a 1420rpm motor this rotates the outside of the sanding drum at 10537 inches per minute. Dividing the 10537 by 12 gives feet per minute. About 878 sfpm. Not fast enough! putting the 4"/2" pulley ratio doubles that to 1756 sfpm. which is still too slow but closer.

There's another thing to consider and that is drum size itself. The larger drum which allows more sandpaper to be used on the drum, this helps keep the sandpaper cooler, last longer and reduces scorching. A 5" drum gives you almost 16" of paper per rotation while yours only gives about 7.4". The smaller amount of paper is gong to have to do a lot more work. I've seen smaller drum sanders work and for small amounts they get the job done but it's better to go bigger.

_________________
Billy Dean Thomas
Covina, CA

"Multi famam, conscientiam, pauci verentur."
(Many fear their reputation, few their conscience)