# Drum Sander #2: Calculations

 Blog entry by Andrew posted 505 days ago 658 reads 0 times favorited 2 comments
 « Part 1: Planning Part 2 of Drum Sander series no next part

Out of curiosity, I ran some calculations on power requirements:

If I have a 1.5 HP motor, I can use a force of 2.88 lbs on a 25” piece. This would mean a low removal rate for larger pieces. I could not determine how much of a removal rate. Some sources say they would remove at a rate of 1/128” each pass. This seems reasonable for a 3 lb force. On smaller pieces more force can be applied. A 1” piece would stall the motor at 72.12 lbs. This amount of force applied to the material would seem to dislodge the piece from the tray, or destroy the sanding belt.

Assumptions :
• A thin slice of sanding belt would come in contact with the material.
• No losses on the pulleys and belt

When I sand by hand using an orbital sander, I do not apply very much force, just a bit more than the sander weighs. My sander weighs 6 lbs over a surface of 19.25 in2 (5 in diameter). This would result in a force of 0.31 lbs/in2. Assuming I apply an additional 10 lbs of force to the sander, totaling 16 lbs of force, this results in a pressure of 0.83 lbs/in2.

Making an assumption that the drum will deform to allow a transverse contact of 0.25 in and utilizing full force potential before stalling the motor, this would allow for a force of 11.52 lb/in2. Therefore, I believe a motor of 1.5 HP would be sufficient to drive the machine and effectively remove more material than I can using an orbital sander. This would also result in a straighter surface.

## 2 comments so far

 dbhost4830 posts in 1611 days #1 posted 504 days ago I can not attest to the engineering data behind it, however I have seen demonstrated Darren at Woodworkingtalk.com had built a 24” wide drum sander with a 1 HP motor, and he demoed it doing full width passes and I believe he claimed his depth was about 1/32”, no stalling, just a TON of sanding dust everywhere. He hadn’t gotten the dust hood on yet… I think you may be trying to over engineer your sander. Which is fine, but just realize, 1/32” is quite a bit of material to be taking off with sandpaper. You really ought to be happy with 1/128” per pass if you are sanding this down. -- Manufacturer of fine quality sawdust since 1984. Comments and advice on my shop welcome. Check it out at http://lumberjocks.com/dbhost/workshop. Gladly accepting shop build donations! Andrew14 posts in 508 days #2 posted 504 days ago That is good to hear that there was a successful demonstration using a 1HP motor at 1/32 removal depth. I doubt that I would ever take off 1/32 using sandpaper. I’ll end up connecting a 2 1/2” dust port at the top of the machine for dust collection. Thanks!

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