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PostPosted: Sat Feb 07, 2009 4:16 pm 
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I am almost done with my homemade drumsander its 24". Can´t wait to press "on" . BUT ! I need to understand what size I need to make it as it should be in "rpm" the motor is an old 1.7 horsepower 2800rpm, 50Hz, "using 3pins" 370W" not 220W if this helps ? .
As I understand it, it supposed to run on around 2000rpm, so what size of pulleys do I need to get it to run at the right speed.??? The pulley that´s on the motor now is 3" .

I will use a 3/4" rod well 20mm to be exact. hope this is enough for the load. any thoughts ?.

Lars.


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PostPosted: Sat Feb 07, 2009 4:59 pm 
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Lars .. you dont say what the drum diameter is ???? I run a 3/4 hp 1725 RPM motor, 3 inch pulley, to a 6 inch drum 6 inch pulley .. so about 860 RPM on the drum. that seems ot work well .. if your drum is adifferent diameter, you might want to figure out feet per minute that the sandpaper hits the wood ...

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PostPosted: Sat Feb 07, 2009 5:09 pm 
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Lars…It’s the surface feet per minute that you need to be concerned with.
What size drum are you using? Is it 24” in width or is that the diameter? I have seen large dia drums but that would be huge. Choosing the correct pulley in order to get the proper SFM is dependant on the drum diameter or more to the point the circumference. The larger the drum, the lower the shaft RPM.

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PostPosted: Sat Feb 07, 2009 5:38 pm 
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if you've got a 6" drum you should be ok with double pulley size on drum vs motor which would give you a ltlle over 2100 fpm.

do you have dust collection to handle the sander?
btw, i'm just finishing up my own drum sander shooting some paint on it now, turned out to be a bigger project than i initially planned duh

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PostPosted: Sat Feb 07, 2009 5:44 pm 
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the drum size is 3,3/4" (9.5cm)


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PostPosted: Sat Feb 07, 2009 5:51 pm 
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the drum size is 3,3/4" (9.5cm)


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PostPosted: Sat Feb 07, 2009 5:52 pm 
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4 1/2" on the drum would give 2055 fpm

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PostPosted: Sat Feb 07, 2009 5:54 pm 
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great !! thank you soo much. how do you calculate this ?.

lars


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PostPosted: Sat Feb 07, 2009 5:58 pm 
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Lars Stahl wrote:
great !! thank you soo much. how do you calculate this ?.

lars

well it's late and it seems my math is flawed...
but still i think 4 1/2 would work

9,5cm drum gives you 29.83cm pr revolution. its spinning at 2800 rpm which is 83524 cm/m /30,48=2740 fpm

correct me if i'm wrong but 3" pulley on motor and 4 1/2" pulley on drum will give 1826 fpm on a 2800rpm motor. as i said it's late here in norway...

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PostPosted: Sat Feb 07, 2009 7:27 pm 
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Thanks alot Frank.
I am from Sweden. Good to know I have more neighbors guitarfriends. :D .

Lars.


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PostPosted: Sat Feb 07, 2009 7:53 pm 
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Lars Stahl wrote:
great !! thank you soo much. how do you calculate this ?.

lars


Feet per minute on a drum is calculated:

Drive shaft D

Driven shaft d

RPM of motor R

Diameter of Sanding drum in inches S

FPM=d/D*R*S/4

I'm cheating here since I'm assuming pi = 3, but that's close enough.


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PostPosted: Sun Feb 08, 2009 7:05 am 
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Thanks Joe.


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PostPosted: Sun Feb 08, 2009 10:32 am 
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Lars, you will love the drum sander once you get it up and running and all the quirks worked out.

Have you run the motor prior to getting it all hooked up to the drum sander? The reason I ask is because here in the US we run into cheap motors all the time that are 3 phase and most of us dont have that at our houses. I'm just wondering if that is what you have with that motor, hence the specs you were reading. Forgive me in advance if I don't know what I'm talking about as I am ignorant of power supply in Sweden. idunno

Are you using the old clothes dryer/presser thing that you showed pics of when you first moved into your shop for this? I can't wait to see pics as I love adapted use tools.

Good Luck.

Darrin


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PostPosted: Sun Feb 08, 2009 10:36 am 
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Wonderful news Lars. How about some pictures? We would love to see your version of a drum sander. Hopefully you were taking pictures through out the building process.

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PostPosted: Sun Feb 08, 2009 9:38 pm 
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Darrin. No not running it by the presses I showed a while back :D Its a 3 fas. old nice motor at 1,7 horsepower. Haven´t started it yet, waiting for the rod so I can stack the drums and hook it up. Not long til I do though [:Y:]

Lillian, I havent taken many photos on the sander, but I sure will though. and I will post as soon as I have some on the camera. the thing is that my camera is not working on a macintosh wish I have, so I have to install the photos on a PC and then transfer them over to the Mac !! hmmm grr. takes forever it seem.

Lars.


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