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  #31  
Old 06-30-2013, 08:56 PM
Viking Viking is offline
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Here's the drum being glued up.



I've got quite a bit of work to do on it to true it up. It's not that even. Kinda rushed through the process of cutting the disks.

I also installed the dimmer switch in the electronics of the saw and fired it up. Great RPM control. All the way from about 5-10 RPMs on the low end, all the way up to full speed. And it is quite a bit quieter on the lower end.
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  #32  
Old 06-30-2013, 09:37 PM
charles Tauber charles Tauber is online now
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Originally Posted by Viking View Post
One of the successful drum sanders I've seen runs at around 1000 RPMS.
RPM=Revolutions per Minute. It is plural. No need to pluralize a plural. RPMS (RPM's, RPMs, etc.) is incorrect. Semantics, I know.

What is more important than drum speed is surface speed in feet per minute. That is, how many feet of sanding surface pass a given point in a given time. That varies with drum diameter and rotational speed (RPM). For the same rotational speed, a larger drum will have a higher surface speed than a smaller drum.


Quote:
A dimmer switch could bring that level down to a more reasonable (and safe, I don't want the drum to fly apart) speed...
If the motor is air cooled, reducing the speed of the motor will reduce the speed of the cooling fan. You run the risk of frying the motor. A better solution is probably to use a more appropriate pulley ratio, one that gives you the speed you want.

You'll need a means of securing the drum to its shaft so that the drum doesn't spin on the shaft. The drum will need to be concentric on the shaft for a) accuracy/repeatability and b) for dynamic balance of the rotating mass (drum). You'll need a means of attaching the sandpaper to the drum.

I'm guessing from the photo that your finished drum will be about 5" or so in diameter and 20" or so long. The combination of drum diameter and shaft diameter needs to be sufficiently stiff to prevent flexing mid-span under load.

Ideally, you'll want about 400 CFM of air flow for dust collection. You'll also want some sort of dust shroud to keep the dust "in". Alternatively, use it outside.

Grit Laskin wrote an article about his home-made drum sander in an early issue of Fine Woodworking. The article provides fairly complete working drawings. You might want to read what he did. Or not. Another author gave full plans for a home-made wide-belt sander in a different issue of the magazine.

I literally jumped for joy the day I disassembled my home-made sander in favour of a commercially made one with a variable speed feed and drum speed, quick-change sandpaper, accurate depth gauge... Back in the day, sanders started at over $20k: now one can be had for as little as $600.
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  #33  
Old 06-30-2013, 11:06 PM
Viking Viking is offline
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Originally Posted by charles Tauber View Post
RPM=Revolutions per Minute. It is plural. No need to pluralize a plural. RPMS (RPM's, RPMs, etc.) is incorrect. Semantics, I know.
Semantics indeed...

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Originally Posted by charles Tauber View Post
If the motor is air cooled, reducing the speed of the motor will reduce the speed of the cooling fan. You run the risk of frying the motor. A better solution is probably to use a more appropriate pulley ratio, one that gives you the speed you want.
Slowing the motor speed should also mean it generates less heat. It's an intermitent duty motor anyway, and I won't be super sorry if it fries, so I'll risk it.

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Originally Posted by charles Tauber View Post
You'll need a means of securing the drum to its shaft so that the drum doesn't spin on the shaft.
I've thought about that. I don't have a drill press, so I free hand drilled the holes for the shaft. The disks just barely fit on the shaft, and so given the fact that they were randomly placed on the shaft and the holes were not completely square, when I clamped them together after gluing them, they should exert a considerable amount of force against the shaft itself. I doubt very much that they will ever come off the shaft without considerable effort.

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Originally Posted by charles Tauber View Post
I'm guessing from the photo that your finished drum will be about 5" or so in diameter and 20" or so long. The combination of drum diameter and shaft diameter needs to be sufficiently stiff to prevent flexing mid-span under load.
The drum will be a fuzz smaller than 4" in diameter when it is finished, and just almost 20" long. The shaft itself it 3/4" steel. If I control the RPMs () and keep them from getting out of hand, it should be stable. But we'll see.

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Originally Posted by charles Tauber View Post
Ideally, you'll want about 400 CFM of air flow for dust collection. You'll also want some sort of dust shroud to keep the dust "in". Alternatively, use it outside.
I'm going to use it outside AND I'm going to put together the dust collection. Just sounds like fun. You should watch (if you haven't) Matthias Wandel's shop made dust collector video. Fascinating. He gets a tremendous amount of power out of the impeller he built.

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Originally Posted by charles Tauber View Post
I literally jumped for joy the day I disassembled my home-made sander in favour of a commercially made one with a variable speed feed and drum speed, quick-change sandpaper, accurate depth gauge... Back in the day, sanders started at over $20k: now one can be had for as little as $600.
I can certainly appreciate that the commercially made sander was a step up. But for a married father of two with bills to pay, this is the best I can do right now. If it gives me a basic thicknessing capability, then I'll be happy with it.
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  #34  
Old 07-01-2013, 06:47 AM
stuw stuw is offline
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Nick,
A little trick I found when making my rollers was after a ton of sanding, I chalked the roller to see the low and high spots, put wood putty in the low spots, let dry and re sanded, sped up the process a lot. I use the hook and loop on mine, the Velcro is thick and does help.

Only other minor issue I found on mine was I had to shim one of the pillow blocks up to match the exact height of the table.

Charles, now that you've gone high tech how much time do you save thickness sanding a top or back set? I like my homemade thickness sander, but it sure does take time.

Stu

btw Nick, how do you plan on adjusting your table height?
Also do you any auctions near where you live? I was at one sat. and they had 4 electric motors from 1/3 h to 1 horse and they went for $10.00 each.
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Last edited by stuw; 07-01-2013 at 06:59 AM.
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  #35  
Old 07-01-2013, 09:17 AM
printer2 printer2 is offline
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Auto body filler might be a good idea to fill out spots. I just set up the sander and put a coarse grit sandpaper on the base raising it more as it took off the high spots. Didn't have quite that much to straighten out but that is just a little more time.


Still would not bother doing the combined impeller thing. I did make up a couple for some heat treating furnaces and learned a bit about it. Find an old furnace, call up a heating-AC company and get the blower from one they replaced. Then you can use your dust collection for other tools also.


The dimmer voltage control might not be a good idea, the motor generates a back EMF (fancy name for a voltage) which counteracts the voltage being supplied. The slower the speed the less EMF it produces compared to the voltage coming in. The bigger the difference between them the more current gets drawn. This is what gives you your power but it also heats up the windings. Better to use the right size shiv.

Last edited by printer2; 07-01-2013 at 09:25 AM.
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  #36  
Old 07-01-2013, 10:39 AM
charles Tauber charles Tauber is online now
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Quote:
Originally Posted by stuw View Post
Charles, now that you've gone high tech how much time do you save thickness sanding a top or back set? I like my homemade thickness sander, but it sure does take time.

Stu
Probably cuts out about an hour or more by the time you include a variety of related activities that are now eliminated.
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  #37  
Old 07-01-2013, 10:58 AM
arie arie is offline
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truing up that roll is the perfect job for a lathe...
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  #38  
Old 07-01-2013, 11:09 AM
charles Tauber charles Tauber is online now
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Originally Posted by Viking View Post
You should watch (if you haven't) Matthias Wandel's shop made dust collector video. Fascinating. He gets a tremendous amount of power out of the impeller he built.
I'm not quite sure what to make of what he's done and his approach to doing it. It looks like a fun experiment, but not a very practical means to having a quiet, low cost, shop vac. The science and engineering behind making a shop vac type machine is well known, much of which he sort of skirted around. His vacuum sort of reminds me of the use of a cogged wheel as a predecessor to the employment of the technology used in gears. They both largely do the same thing, but one lacks the refinement and "science" of the other. Still, kudos to him for doing it, though these days it isn't how I'd choose to spend my time, effort or money.

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But for a married father of two with bills to pay, this is the best I can do right now. If it gives me a basic thicknessing capability, then I'll be happy with it.
I understand the no-money thing. I started out with a Sears router, literally a hand full of hand tools and a rickety bench. I had lots of time and no money. Basic thicknessing capability is a hand plane, scraper and sandpaper.

I also understand the desire to do it all from the ground up, making all one's own tools, jigs, machinery, etc. Also been there, done lots of that. Designing and making tools is a different activity than making guitars. Just depends upon where one's interests lie, how one partitions one's time between making tools and making guitars.

Last edited by charles Tauber; 07-01-2013 at 11:17 AM.
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  #39  
Old 07-01-2013, 01:42 PM
Tom West Tom West is offline
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Originally Posted by charles Tauber View Post

You'll need a means of securing the drum to its shaft so that the drum doesn't spin on the shaft.
Use a pulley to match shaft diameter, have a machinist machine off the outside half of the V, on that flat surface drill 4 screw holes, put the altered pulley on the shaft and run the flat up to the end of the plywood discs, install 4 screws, tighten set screws on shaft.
Tom
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  #40  
Old 07-01-2013, 02:34 PM
charles Tauber charles Tauber is online now
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Quote:
Originally Posted by Tom West View Post
Use a pulley to match shaft diameter, have a machinist machine off the outside half of the V, on that flat surface drill 4 screw holes, put the altered pulley on the shaft and run the flat up to the end of the plywood discs, install 4 screws, tighten set screws on shaft.
Tom

At the ends of the drum, I cross-drilled the shaft, inserted a pin through the hole longer than the diameter of the shaft and put screws into the ends of the drum adjacent to the pin, preventing relative rotational motion of shaft and drum. Lots of ways that it could be done, including keys.

Last edited by charles Tauber; 07-01-2013 at 02:42 PM.
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  #41  
Old 07-01-2013, 03:12 PM
printer2 printer2 is offline
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Used epoxy.
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  #42  
Old 07-01-2013, 05:15 PM
Tom West Tom West is offline
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Quote:
Originally Posted by Viking View Post




The drum will be a fuzz smaller than 4" in diameter when it is finished, and just almost 20" long. The shaft itself it 3/4" steel. If I control the RPMs () and keep them from getting out of hand, it should be stable.




















Your shaft of 3/4" should be more then big enough. The discs add stiffness to the shaft and the pillow blocks are close to the drum.
Tom
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  #43  
Old 07-01-2013, 06:52 PM
stuw stuw is offline
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I used apoxy also, it has never slipped or moved yet
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  #44  
Old 07-01-2013, 07:00 PM
printer2 printer2 is offline
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I just noticed, some of the boards your shop is made of might make for a cool guitar.
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  #45  
Old 07-01-2013, 09:14 PM
Viking Viking is offline
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So I'm covered in saw dust, or rather sander dust. Good grief. My wife may never forgive me.

I spent a good 1-2 hours tonight truing up the drum. I simply used a piece of flat wood, on top of the adjustable table, to which I had stapled some sand paper. I've still got a number of low spots, but I feel confident they'll come out in the next day or two.

Turns out the dimmer switch is probably just not necessary. I pretty much had it wide open the entire time. I think the drum is turning at roughly the right speed. I don't think the motor is able to turn the whole thing at it's full RPM capacity. Though, I didn't smell any cooking electronics during the whole affair, and I actually pushed the motor pretty hard. Several 5-10 minute sessions without giving the motor a break.

And, the drum ran straight, no wobbling. at least, none once some of the bigger irregularities were sanded off. They did initially make for some decent wobble. Once they were gone, it runs steady. I feel certain it will result in some pretty consistent thicknesses once I'm actually sanding wood on it.

The drum was solid on the shaft as well. If the shaft was turning, so was the drum.
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