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I am in the process of building Hawley's thickness sander. I just have to buy a few more screws and bolts and I'll be done. I put a copy of an Excel spreadsheethttp://www.jaymc.com/guitar/other/Thickness%20Sander%20BOM.xlsx on my website which shows the parts I use, the cost and where I bought them. I made circle cutting jig to cut all the 3/4" plywood disks that make up the drum. The drawings are available on my site. http://www.JayMc.com/guitar JayMc.com/guitar. I'm into it about $300 and still need to buy about $30 of parts plus sandpaper. You could build one for a little less if you used scrap wood, etc.



Spreadsheet http://www.jaymc.com/guitar/other/Thickness%20Sander%20BOM.xlsx

bringing this back up to ask about pulley sizes. I picked up a free 3/4 hp motor. It runs at 3450 rpm. I'm working on a drum that is 5"x20". I know the motor rpm is probably a little on the high side but was hoping to size the pulleys to slow the drum down. Looking at some of the factory made drum sanders of the same size the drums are running about 1600 rpm. Anyone have suggestions on pulley sizes? Am I shooting for the right speed? I was looking at the motors that Grizzly sells, if this motors doesn't seem to fit the job it might be a good chance to increase the hp and get the right rpms. But I'll wait and see what I hear back from the forum here for financial reasons. Thanks.

kyle

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Kyle

Pulleys in the ratio of 2 to1 will get you in the ballpark. Three inch on the motor and six inch on the drum will give you one half your motor r.p.m.s. Any combination of 2 to1 will do the job. Generally sanding speeds are quoted in feet per minute for the abrasive. Not sure what that should be,so you will have to wait for others to give you an answer.
Tom

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A person who has never made a mistake has never made anything!!!

That motor should be fine, Kyle. Some may tell you it's not powerful enough, but unless you're doing a motorized feed at a set rate, you'll be just fine. Slowing it down is a good idea. Don't be obsessive about it. 1600 is good, but it's not an exacting tolerance. Shoot for a 2:1 gear ratio, but as long as you're close, just go with it.

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David Morris

Kyle,

When I built mine a few years ago, I looked up the feet per second rate for a bunch of available sanders. I then took the average of those rates and shot for that. I had a motor on hand with a step pulley and a single pulley that fit my shaft. I picked a setting on the step pulley that gave me a drum RPM in the range I wanted (I had a general idea how big I wanted the drum diameter to be). I then sized the drum to have the circumference that would give me the FPM I wanted. There is a lot of room for variation, but the moral of the story is, try to get the surface feet per minute right (RPM doesn't take into account drum diameter).

Sadly, I can't find all of the figures I used to get mine done; If I ever have to make another I'll be at square one. . .

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Grizzly specs 2100-2300 FPM (feet per minute) for their 16"-24" drum sanders. I used 2200 FPM for the one I built (1.5 HP, 4" drum).
The equation is
speed = 2 * Pi * RPM * radius
FPM = 2 * Pi * RPM * radius_in_inches / 12
solve for RPM:
RPM = 6 * FPM / ( Pi * radius_in_inches)
1680 rpm = 6 * 2200 / (Pi * 2.5)

For a 3450 motor, that's a 2.05:1 reduction. Tom's estimate of 2:1 is right on! If the motor stalls, you could go 2.5:1 or slower.

The diameter that matters is the "pitch diameter", which is the middle of where the belt actually rides. PD is less than the OD of the pulley, the amount depending on the belt:
http://www.mcmaster.com/#zinc-die-cast-pulleys/=fqfa9g
The difference between PD and OD is more important if using smaller diameter pulleys and/or narrow belts.

I'd suggest a cogged belt, as they run smoother.

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David Malicky

Thanks so much for the input. I will be shopping for pulleys in the next week or two so I'll have time to get a closer estimate of what I need. I may order both 2:1 and 2.5:1 to play it safe. Thanks again.

kyle

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Kyle

I am thinking about dismantling the 10" bandsaw (has a 1/2 HP motor) once I get a larger and better cast iron bandsaw, and using the motor and other parts on the bandsaw to build it into the thickness sander.

I figured if I sold the bandsaw I am probably not going to get much out of it, and the cost of the motor will easily be higher than whatever I get from selling that bandsaw anyways. Then I could just use the wheel as a pulley if I can find ways to carve a V groove into the aluminum wheel.

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

I don't know that I would dismantle the band saw. When you get a larger saw, you may find that you want to keep the smaller one with a smaller blade for certain tasks. I'd look for some pillow blocks and proper pulleys locally rather than destroy a useful (albeit not ideal) working tool.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

+1 to this. When I was sourcing a motor, I looked everywhere. I know you have limited resources in Taiwan, but surely there's something you have access to that would have a motor. I took one out of an old evaporative cooler. Don't buy a motor though. Just take one out of something that's broken and/or free.

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David Morris

What about an AC unit or a washing machine? new motors are quite expensive in Taiwan.

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

Now you're thinking. All you need is a method of forcing a shaft to spin with enough strength at a reliable speed. The motor doesn't care what it used to do. My guess would be that an AC unit would be a good bet, but you'll have to do some research.

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David Morris

The problem is, how do I know if a given appliance will exert enough power to do what it needs to do?

I don't think I'll have trouble tracking down old fans or whatever that still have a working motor but I just have no way of knowing if they'll have enough power without trying it first. I was thinking AC units because the compressor motor has to be quite powerful in order to drive the thing... Maybe I'll have to check those AC repair places to see if they have compressor motors.

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

Yes, but it will be belt drive, which means if the motor doesn't work, it's not hard to replace it. Here's a little secret. I have no idea how strong the motor is on my drum sander. The casing is too rusted to tell, and I have no idea what the model of the evaporative cooler was. But it works. If you do know what you're taking the motor from, go to Google and see what you can find out. I believe you're correct about the AC units. I think most dryer motors are something like 1/3-1/2 hp, and if you can find an old table saw, even better. Electric lawnmowers are great too. I would think you could probably buy a used piece of outdated technology for much less than you could buy an extracted motor. In the States, it's not too tough to come by that stuff for free if you're resourceful.

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David Morris

The HP will almost always be on the motor label, along with RPM, Volts, Hz, and phases. I'd suggest 1/2 HP as a minimum.

There are 3 motors in an AC system: the compressor motor, the condenser fan motor, and the blower motor.
- In a residential system, the compressor motor is usually hermetically sealed inside the black compressor shell and would be difficult to extract... even if cut apart, it probably doesn't have a usable shaft. The condenser fan and blower motors are much easier to use -- these range in HP from 1/10 to 1/2 HP on a residential system.
- In a commercial system, all motors are likely to be standard AC motors and at least 1/2 HP. More likely to be 3 phase, though.

Washing machine motors are usually 1/2 HP and 1725 RPM (at 60 Hz). They're typically fully exposed so you'd need to make a protection shell (as well as some kind of mount, usually). Often they are 2 or 3 speed (multiple windings) -- that sounds nice but the wiring labels are often not present at all on these, so you'd need a wiring diagram to even wire one at a single speed. An older or low-end washer motor is more likely to be single speed and easier to wire.

The dryer motors I've seen are similar to washer motors (no case, odd mounting), but single speed and 1/3 HP.

Also look for broken treadmills -- these have DC motors between 3/4 and 2.5 HP. Be sure to get the controller and speed pot, too.

In most any US city there are industrial metal recycling yards -- these are often good places for bargain used motors, as they tend to view stuff more like scrap metal. I'd guess there are similar places in Taiwan?

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David Malicky

I'll look around. I remember getting rid of an old drill press and the guy said he bought it for the motor, but I am not sure if I'd find an old, cheap drill press lying around though.

I am sure such things exist but due to my limited understanding of how things work in Taiwan (they do not post stuff on google, craiglist, or ebay like most Americans) it will take a bit more time.

_________________
Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

My motor came from my dad's basement. He doesn't remember where it came from, it was probably a furnace blower motor. It is only 1/3 hp. It will bog down when sanding a jointed back (16+ inches wide) if I try to take too much off per pass. As a hobbyist, I can take my time with light passes. The great thing about belt drives on home made machines is that I will someday stumble on a good deal on a more powerful motor.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

I ran across another source for good motors at low $: used pool or spa pumps. In the US, these often show up on craigslist as pool owners upgrade to high efficiency types or because the pump leaked. It's pretty easy to disassembly them to get the motor (search youtube for "pool pump impeller"). If you can deal with some idiosyncrasies, they are bargains -- I just got a 1.5 HP for $30 and another 1.5 HP for free. It's apparently a buyers’ market -- no one else had called on them for weeks (who wants a used pool pump?)

The motors are typically 1/2 - 2 HP (115V up to 1.5 HP), 3450 RPM, CCW rotation (at pump end), open drip proof case, continuous duty, and made by AO Smith, Magnetek, or other good maker. They may be capacitor-start (same as on machinery) or permanent-split-capacitor (less overload torque available, but probably ok unless your app is 'hard to start', like a compressor). The capacitor is often inside the end-shroud. Unlike other motors, the nameplate amps corresponds to the HP * Service_Factor (i.e., the max amps). SFs range from 1.0 up to 1.85 (a "1 HP" motor with a 1.5 SF can actually deliver 1.5 HP continuously).

The shaft is usually 5/8" but no keyway or flat -- I either file a flat or drill a short indent for a setscrew. They are usually face mounted, which is less convenient for most apps, but a foot can be made. Some of the motors have a large "square flange" overhanging mount which isn't great for belt drive (one of mine was like this... I cut the flange off). The spa pumps usually have a foot.
http://www.electricmotorwarehouse.com/pool_spa_menu.htm
The bearings are probably not designed for large belt loads, but should be ok at lower duty. Both of mine had smooth bearings but were a bit noisy... running outside for years. I dripped some oil into the bearing seals and they quieted down nicely.

http://craiggers.com/#!/search/all/sss/ ... rice=%3C50

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David Malicky

The best drum sander plan I have seen is to stay at your job enough extra hours or sell some items on ebay to make enough to buy yourself a jet drum sander.

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http://goatrockukulele.com

That's not as much fun as building your own though!

My sander is pretty much the same design as this one, except it is 21 inches wide. Make sure your table is very sturdy. I tried to get by with one piece of 3/4 birch ply, and it flexed/pivoted on the adjustment screw, causing it to sand heavy in the middle and light on the edges. I would recommend at least two sheets of plywood. My motor is a 1hp, 3750 rpm off of an old air compressor. The gearing is 1:1 with a 6 inch drum, and it hasn't had any trouble so far.

And then you get one that isn't cantilevered.

Yes, the table needs good reinforcement to keep it from flexing.

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David Malicky