Homemade Brass Tumbler Math Demystified

[hunter64]

Homemade Brass Tumbler Math Demystified.

The latest craze in how to clean your brass is with stainless steel media in a rock polisher instead of in a vibratory cleaner as was the norm for years. Living in Canada I get taken to the cleaners when it comes to cross border shipping and sometimes buying local can be just as hard on the wallet.

Cabelas Canada has the Thumler for $229.99 for there 12 lb capacity tumbler. Some of the bigger ones have a 15 lb capacity.

I thought that I should be able to make one cheaper and be able to hold more than 12-15 lbs total of water,pins and brass. Water itself weighs 8.3 lbs (US Gallon) and then they say you need 5 lbs of pins so that only leaves 1.7 lbs of brass (15lbs-8.3-5). Not sure exactly how much 1.7 lbs of brass is but the amount that I shoot when I get home from the range the bag is heavy and to clean all that brass would take about 4 trips in the tumbler.

So I cobbled together a very crude mock-up of what I wanted the tumbler to look like after watching lots of you tube videos. I did a rough layout on my bench with a piece of wood, some crude bearings, some redi rod, a couple of pulley’s and an old treadmill motor and controller. I put a roller on each end to prevent the drum from walking across the shafts. Threw it all together and tested it out and it worked great.












I then saw a you tube video of a design I liked and welded up a steel frame and used some of the posters idea’s on what to cover the shafts with and away I went. Had trouble with the bearings not turning correctly but after I ran them for a bit they loosened up and are now working great.
http://www.youtube.com/watch?v=TtVHv...ature=youtu.be











All I did was mount the treadmill motor and associated controller on the new frame. I left off the rollers on each end because with adjustable legs I could perfectly balance the base to keep the drum in the middle and not walk along the shaft.

Well I built 4 of them now for my friends over the weekend and every one of them asked me what parts are needed to make the drum spin at the correct amount if you only have a single speed motor like out of a furnace or washer/dryer.

To calculate the size of the pulleys needed with a certain speed of the motor we can use this simple formula.

Motor RPM x Motor Pulley Diameter = Driven Pulley Diameter x Driven RPM

After we are done figuring, this only gives us the speed of the driven shaft on the tumbler
Since we want the speed of the driven shaft on the tumbler we can re write the formula as:

Motor RPM x Motor Pulley Diameter
---------------------------------------------- = Driven Rpm (Speed of the driven shaft)
Driven Pulley Diameter


Then you use the speed of the driven shaft on the tumbler to figure out what the speed of your Tumbler’s Drum is going to be. I combined both formulas into one to make it easier to figure out the speed of the drum. I made up some letter designations to make it easier to follow the formula and here they are:

Motor Rpm= M
Motor Pulley Diameter= MP
Driven Pulley Diameter = DP
Diameter of Driven Shaft = DS
Diameter of Tumbler Drum = TD
Driven RPM of the Drum = DR


M x MP x DS
------------------- = DR or the speed of drum on the tumbler.
TD x DP


Lets try one .

You found a motor at the dump that has a sticker on it that says it turns at 1725 RPM.
You go to Lowes and find a pulley that fits the motor and it has a diameter of 2”.
You buy some bearings for the shaft to run on and they are ½ “ size for your ½” shafts.
You buy a 6” pulley for the driven shaft for the tumbler drum to run on.
You make a 6” tumbler drum out of a empty plastic jar.
How quick will your tumbler drum be turning at?

With our handy dandy formula we can plug in some numbers and find out.

1725rpm x 2” x ½”shaft
--------------------------- = 47.9 RPM or about 48 RPM the tumbler drum will be going.
6” drum x 6”pulley


The Thumlers regular speed is 30 rpm and the high speed is 40 rpm. We don’t want anything quicker than 60 rpm because the brass and contents will just stick to the outside wall due to centripetal force. So in this case we guessed correctly for the size of drum we want and the pulley needed to obtain that speed.



So let’s say we find some 5/8” bearings on sale and our drum size is 8” instead of the 6” we had before.
Using the same motor and pulley sizes what would be our drum speed?

1725 x 2” x 5/8”
------------------- = 44.9 RPM So 45 RPM is right in the ballpark .
8” x 6”

You can always buy an adjustable pulley for the motor that varies so you can fine tune the speed of the drum but figuring out what size of drum you want to make and the smallest size of the motor pulley, you can mix and match the size of the shaft and pulley on that shaft so you don’t have to spend extra money experimenting on what you want.


If you know the size of your Drum that you want to make and the size of the motor pulley then with algebra we can manipulate the formula to come up with the size of the pulley on the driven shaft.

M x MP x DS
---------------------= DP (The size of the pulley needed to put on the driven shaft)
DR x TD

Let’s try one out.

You have a 7” drum, a 1725 rpm motor with a 3” pulley on it and you have some 7/8” bearings and 7/8” shaft to use for your tumbler. What size of pulley do I need to put on the 7/8” shaft to give me 60 RPM for the Drum?

1725 RPM x 3” x 7/8”
-------------------- = 10.8” (You would need about a 11” pulley)
60 RPM x 7”

It would be hard to find an 11” pulley so your better bet would be to drop the 3” pulley on the motor to a 2” pulley which running it thru the formula again would give you about a 7” pulley which is more realistic.


You have the driven shaft pulley diameter of 7” on a 5/8” shaft and you want to know what size of pulley I need to buy to put on the motor to give me 55 rpm for my 8” drum.

Manipulate the formula to give you this.

DR x TD x DP
------------------ = MP (Size of the pulley needed on the motor shaft)
M x DS

Let’s try it.

55RPM x 8” x 7”
-------------------- = 2.85” ( You would buy a 3” pulley and that will get you close)
1725 RPM x 5/8”

With an adjustable DC motor like on a treadmill then just buy any two pulley's that you need and you can adjust the speed of the motor to get what you want.


How much to make the Tumbler?

3” pulley 6.00
4.5” pulley 9.00
½ “ shaft for 5 ‘ 9.00
½” Pillow Bearing 13.00 each (52.00 total)
½” heater hose 4.00
Base mounts 12.00 (rubber cups I put over adjustable screw in legs)
1 ½” Square tubing 30.00 for a 8 foot length and I had 4” left over
Motor found at scrap yard

Total $122.00 in Canada

You will get the supplies much cheaper if you live in the US.

I could have skipped the welded square tubing and substituted wood which would have been cheaper but I wanted something to last. As far as the motor goes, look on Craig's List or visit a furnace replacement company or find an old washer or dryer, there are lots of free motors out there.

One online store wants 799.99 US for a 40 lb tumbler. Mine was 122.00 and is just as good and will actually hold more weight.

Only thing left is the drum, I made one out of 8” PVC from a Plumbers Warehouse with a neck down coupler and a cap on the end. Cost me about 18 bucks but I can fill the thing with the brass, pins and water and when I weigh it the scales tip at 55 lbs. A far cry from 15 lbs max in the store bought one and I have a 3/4hp motor driving it instead of 1/30th HP.

[dragonrider]

Thanks Hunter I will need that.

[cajun shooter]

That's some very nice back yard handi work that looks as if it may out last the owner.

[Mk42gunner]

I think we need to make the original post in this thread a sticky.

Robert

[Jailer]

Your second design looks like BIGDAWG's design from ar15 forums. I'm right in the middle of building mine using that design.

My first attempt at a drum from 6 inch PVC was a failure because I bought the wrong parts so once I get it situated it will end up a bit smaller than I initially intended. Should still hold around 2 gallons of water.

I've got a buddy that works for the water dpt in a local town that got me a piece of 8 inch sch 40. I'm picking that up this weekend for my next attempt at a drum. An 8 inch piece at 18 inches long should do plenty of brass.

Thanks for the math too. Should make things a little easier for us dummy's trying to do this on our own.

[hunter64]

Jailer: I have seen lots of designs and they are all about the same. I did the mock up with wood and then I went looking on the Internet and came across a few that were detailed like BIGDAWG's. The biggest thing that is missing from all of them is the math so I did it so you didn't have to play around with different pulleys to get what you need for speed.

I work for a gas utility company so I have an unlimited supply of PVC ends that can not be used so I picked a 8" diameter and tried it. The problem with it is that it is not a standard size for caps and adapters so I use it for my dry tumbler stuff in walnut and went to a plumbing supply store to make up a water tight version.

I just couldn't see buying a tumbler that could only do about 1/3 to 1/4 of the amount I need cleaning at one sitting after a day at the range.

I can now do all my .223 and .45acp together at once. My 45-70's in another batch and my 38 spl in a third batch. With a 15 lb model I would have had to do 3 batches of .223, 2 batches of .45acp, 2 batches of 45-70 and 2 batches of 38 spl.

[Jailer]

I just couldn't see buying a tumbler that could only do about 1/3 to 1/4 of the amount I need cleaning at one sitting after a day at the range.

Exactly the same reason I went ahead with my build. Why spend nearly $200 for a small tumbler when you can build one for about the same price that will do a large amount of brass at once.

With the amount of 223 and 45 that I go through the Thumler just wasn't an option.

[SlowSmokeN]

Can you put up a couple of pictures with the tube on it running

Thanks

[hunter64]

A guy at work has it for a few days. When it gets back I will post a few pictures.

http://www.youtube.com/watch?v=TtVHv...ature=youtu.be

This is basically the same other than he uses a single speed motor to drive his and his 8" drum is slightly longer than mine, the rest is the same.

[BigShot]

Impressive workmanship!

[Jailer]

I picked up my 8 inch piece of sch40 so my 8 inch drum should be finished in the next couple days or so. Once I get that done I can get working on getting the steel cut for the frame.

Everything else is ready to go, I'm just holding off having the steel cut until I have a finished size on my 8 inch drum to work from.

[hunter64]

Did 500 .357 Magnum brass last night and after 1 hour I took the lid off to see if that was enough time in the tumbler. There were a few cases that still needed a bit more so I put it back on for another hour.

The brass looks absolutely new, inside and out and even the wife commented on how clean they were. The brass was absolutely filthy before they went in, most were range pickup that had been sitting in the dirt for who knows how long.

I know how to post pictures but is there a help me file on the site somewhere that teaches us older folk how to post video?

[beagle]

My old shooting partner who is a master machinist and his son got together and made what we call the "Tumbler from Hell".

They machined a nylon gear and a base fitting for a 5 gallon plastic bucket and set it on about a 45 degree slant. An old washing machine motor geared down ran it. Nylon slats were run inside the bucket to break up the payload and cause a tumbling affect. Used with regular media, it would tumble about 3,000 9mms at one time. It works well.

Another acquaintence made a tumbler with a DC motor and set it in his pickup bed and he'd tumble to and from work every day and save electricity.

You never know what you can come up with until you give it a try./beagle

[montana_charlie]

the brass and contents will just stick to the outside wall due to centripetal force.

Centrifugal force
CM

[hunter64]

I always thought that Centrifugal force was the theory (or Math) behind an object spinning on the outside of an axis and centripetal force was the actual object doing just that.

Not really sure but the idea is that if you turn the drum too quick the brass and pins will stick to the outside wall and not much cleaning will happen. With water as the medium instead of air I am not really sure the theory still holds true and you just might be able to go quicker.

Anyway 2-3 hours is all that is needed to clean lots of brass. Compared to running my vibrating brass cleaner all day with walnut shells and not even coming close to the same cleanness as the stainless steel pins, I am really happy.

Beagle: I once seen a club member years ago use a cement mixer to clean his .45acp brass with lizard litter, he could put a lot of brass in there also. As Plato said. "Necessity is the mother of all inventions" or something like that.

[montana_charlie]

I always thought that Centrifugal force was the theory (or Math) behind an object spinning on the outside of an axis and centripetal force was the actual object doing just that.

Centripedal force (generated by gravity) prevents the Moon from escaping, and centrifugal force (generated by velocity) keeps the Moon from falling on our heads.

CM

[hunter64]

Thought I would update what the final product looks like with the motor/controller mounted. I have had lots of requests to take some pictures.

[nanuk]

Centripedal force (generated by gravity) prevents the Moon from escaping, and centrifugal force (generated by velocity) keeps the Moon from falling on our heads.
that is how I was taught it in grade school!
CM

Thought I would update what the final product looks like with the motor/controller mounted. I have had lots of requests to take some pictures.

hunter64: any reason to couple the shafts together or do you think having only one power shaft driving the bucket will be enough?

[hunter64]

hunter64: any reason to couple the shafts together or do you think having only one power shaft driving the bucket will be enough?

I was concerned about that also. When I first started it up to give it a test run, once in a while the drum would slow down with the rear shaft driving and the front shaft idle. I figured that maybe the pillow bearings needed to be broken in first as they were stiff to move with just my fingers when they were out of the frame.

I made sure the bearing were full of grease and I turned on the tumbler and let it run overnight with no drum on it, just the motor turning the bearings. In the morning I removed the shaft and tried the bearing again by hand and I noticed a huge improvement on how little effort it took to turn compared to what it was when they first came out of the box.

So I switched the front bearings that were not driven to the back and put the back ones on the front. That is all it took and it works perfectly now with never slowing down.

In hind sight I was testing the tumbler with a drum that was empty and only weighed 5 pounds or so at the most. The next time I tested it the drum was full of brass and water and pins and is close to 50 lbs.

I am going out to the range today so sometime this evening I am going to take out the tumbler and before filling the drum with brass i am going to try it again on the rollers without anything in side and see if it slows down. Most likely it will not as I have run it about 40 hours so far.

[Catshooter]

Nice work hunter.


Cat