Drum Sander Concept

shipwright · Post by **shipwright** » Mon Mar 21, 2011 1:36 am

Something to ponder:

1) SS (500 and later anyway) comes with two outputs on the left side that run at two different speeds.
2) Drum sanders (thickness type) need two drives at different speeds.
3) I could use a drum sander for veneer leveling here in AZ.

So could the output speeds be reconciled to the required drive speeds for a drum sander without resorting to ten foot diameter pulleys?
Well, yes actually.

The following concept shows my idea for such a beast. I think if my calculations are correct (Please check them. It's late and I could be miles off) the feed belt would run at about ten feet / minute and the drum would run at about 1700 rpm with the SS set at 700 rpm. If I'm right, this concept could work well............maybe.

This is only a concept at this stage. Something to think about and give me feedback. The sprocket and chain are imported and not very true to scale and lots of things like covers, bearings, dust collection and structural bracing are omitted because I'm very new at sketch up and it's a lot of work for me.

So... Am I nuts? or am I onto something? or do I need those ten foot pulleys because I can't do simple arithmetic?

http://sketchup.google.com/3dwarehouse/ ... 2830a8f2a6

Paul M

JPG · Post by **JPG** » Mon Mar 21, 2011 4:01 am

shipwright wrote:Something to ponder:

1) SS (500 and later anyway) comes with two outputs on the left side that run at two different speeds.
2) Drum sanders (thickness type) need two drives at different speeds.
3) I could use a drum sander for veneer leveling here in AZ.

So could the output speeds be reconciled to the required drive speeds for a drum sander without resorting to ten foot diameter pulleys?
Well, yes actually.

The following concept shows my idea for such a beast. I think if my calculations are correct (Please check them. It's late and I could be miles off) the feed belt would run at about ten feet / minute and the drum would run at about 1700 rpm with the SS set at 700 rpm. If I'm right, this concept could work well............maybe.

This is only a concept at this stage. Something to think about and give me feedback. The sprocket and chain are imported and not very true to scale and lots of things like covers, bearings, dust collection and structural bracing are omitted because I'm very new at sketch up and it's a lot of work for me.

So... Am I nuts? or am I onto something? or do I need those ten foot pulleys because I can't do simple arithmetic?

http://sketchup.google.com/3dwarehouse/details?mid=a31d1e95179bb4c380e2ca2830a8f2a6

Paul M

Insufficient input information to answer(belt/input shaft linkage/ratios/etc.)

However tis a fact that with the ss set to '700' rpm, the lower shaft is doing 1138 rpm.

dwevans · Post by **dwevans** » Mon Mar 21, 2011 9:18 am

You don't necessarily need two power inputs, I built mine as a manual feed sander with a crank, but this design could be modified to power feed if you want it. Adds a lot of complexity though.

Check this thread out, post #6 if my thickness sander.

https://forum.shopsmith.com/viewtopic.php?t=6256

pennview · Post by **pennview** » Mon Mar 21, 2011 9:32 am

For feeding, I'd expect you need a separate slow speed motor like a gear motor or a DC motor and controller like on a Performax, etc. If the feed roller has a 2" diameter with a circumference of about 6.28", you need to turn the roller at about 20 RPM for a feed rate of about 10 feet per minute. I don't think you'll get there by using pulleys to reduce that 700 RPM spindle -- that's about 35:1 reduction, requiring a 70" pulley driven by a 2" pulley.

damagi · Post by **damagi** » Mon Mar 21, 2011 10:04 am

In general my thoughts on this were to use the main table to raise/lower. If a belt feed were desired it could either sit on top of the table or straddle the carriage. my thoughts on power feeding were around repurposing a cordless drill motor.

ddvann79 · Post by **ddvann79** » Mon Mar 21, 2011 10:54 am

shipwright wrote:Something to ponder:

1) SS (500 and later anyway) comes with two outputs on the left side that run at two different speeds.
2) Drum sanders (thickness type) need two drives at different speeds.
3) I could use a drum sander for veneer leveling here in AZ.

So could the output speeds be reconciled to the required drive speeds for a drum sander without resorting to ten foot diameter pulleys?
Well, yes actually.

The following concept shows my idea for such a beast. I think if my calculations are correct (Please check them. It's late and I could be miles off) the feed belt would run at about ten feet / minute and the drum would run at about 1700 rpm with the SS set at 700 rpm. If I'm right, this concept could work well............maybe.

This is only a concept at this stage. Something to think about and give me feedback. The sprocket and chain are imported and not very true to scale and lots of things like covers, bearings, dust collection and structural bracing are omitted because I'm very new at sketch up and it's a lot of work for me.

So... Am I nuts? or am I onto something? or do I need those ten foot pulleys because I can't do simple arithmetic?

Paul M

Paul,

I think you may be onto something here. Without taking the time to do the math one can't be certain, but it would appear upon preliminary review that your gear reduction would be pretty close to the appropriate feed rate for the belt. I work in finance, not engineering, so I'd have to dust off those cobwebs, but I think you'll get some substantial speed reduction with that setup. It's ingenious. Using the measuring tape tool in SketchUp, these are the sizes of the pulleys I came up with from your drawing:

Drive Pulley - 1 1/2"
Large Idler Pulley - 8 1/2"
Small Idler Pulley (same shaft) - 1 1/2"
Belt Drive Pulley - 9"

Based on some of the previous comments, I'm wondering if people realized you have two stages of gear reduction here. Without doing the math, I'm guessing your drum would rotate at about 800 to 1,000 rpm at it's spindle. You stated it would rotate at about 1,700 rpm. Perhaps you want to swap the pulleys for the drum? Maybe I'm in left field here. What do you think about using wooden gears to drive the drum instead of pulleys? You could have a couple of different sized gears on hand and swap them out to change the drum speed. The catch is the arms that hold the drum in place would have to be able to articulate.

Along the same note, you could use gears in place of belts and pulleys for the belt drive as well. That might be easier to maintain. Here is Matthias Wandell's gear template generator for making wooden gears.

I really like the idea for the thicknessing (drum lowering) mechanism. I'm just curious as to how the rig will stay in place without some sort of lock. I would think it would have a tendency to unscrew itself and result in the drum slowly moving away from the work.

Keep up the good work!

jimmyd · Post by **jimmyd** » Mon Mar 21, 2011 11:43 am

No answer to the feed motor issue, but your post reminded me of killer plans for a thickness sander Nick Engler included in his "The Workshop Companion" series in the Sanding and Planing volume.

shipwright · Post by **shipwright** » Mon Mar 21, 2011 1:28 pm

JPG, All the info is there in the sketch up. You should be able to download and examine the model.

dwevans,pennview,damagi,jimmyd, I am aware that there are lots of DIY drum sanders out there with various configurations of hand operated drives and auxiliary motors. The whole plan here was to create something of "elegant" design that would make use of SS's inherent advantages. This isn't meant as criticism, just a clearer statement of the purpose of this little experiment.

ddvann79, You seem to have grasped the concept very well. Yes I did invert the drum drive pulleys. the actual specs are in the sketch up if you download and measure, but here are the main ratios etc:

The speed ratios are as follows:
SS output, top shaft = 700 rpm, 1.5” to 9” ratio= idler shaft speed of 11.67 rpm, 1.5” to 9” again = 19.44 output shaft rpm. two inch drum at 19.44 rpm = 6.28” circumference x 19.44 rpm = 122” / minute = 10.17 feet/minute.
I did get the pulleys reversed on the drum drive but I fixed it this morning. They are now:
SS lower output at 700rpm upper output = 1141 rpm, 4.5” to 3” ratio = output speed of 1711 rpm.

Paul M

JPG · Post by **JPG** » Mon Mar 21, 2011 1:48 pm

shipwright wrote:JPG, All the info is there in the sketch up. You should be able to download and examine the model.

dwevans,pennview,damagi,jimmyd, I am aware that there are lots of DIY drum sanders out there with various configurations of hand operated drives and auxiliary motors. The whole plan here was to create something of "elegant" design that would make use of SS's inherent advantages. This isn't meant as criticism, just a clearer statement of the purpose of this little experiment.

ddvann79, You seem to have grasped the concept very well. Yes I did invert the drum drive pulleys. the actual specs are in the sketch up if you download and measure, but here are the main ratios etc:

The speed ratios are as follows:
SS output, top shaft = 700 rpm, 1.5” to 9” ratio= idler shaft speed of 11.67 rpm, 1.5” to 9” again = 19.44 output shaft rpm. two inch drum at 19.44 rpm = 6.28” circumference x 19.44 rpm = 122” / minute = 10.17 feet/minute.
I did get the pulleys reversed on the drum drive but I fixed it this morning. They are now:
SS lower output at 700rpm upper output = 1141 rpm, 4.5” to 3” ratio = output speed of 1711 rpm.

Paul M

Decimal point off 1 place.

shipwright · Post by **shipwright** » Mon Mar 21, 2011 2:06 pm

[quote="JPG40504"]Decimal point off 1 place.]

OK, 1.666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666667http://www.shopsmith.net/forums/images/smilies/wink.gif
How do you get those little faces top work?
Paul M