Tank Tumbler ?'s

[NorthWoodsDiver]

So I embarked on a journey to build a tank tumbler for a pair of tanks, this due to getting a screaming deal on a pair of used steel tanks which after paying for I found some rust and pits.

I have found a couple 1/4hp electric continuous duty motors with 1750 RPM rating. For tank tumbling I need like 40-70 RPM so I will need to use a pulley system and maybe a jack shaft setup. However its been a while since I have done even basic math and I fall way short of knowing how to calculate what size pulley will lead the proper RPM. can anyone point me to some simple way of estimating this. I will be tumbling mostly steel 72's but eventually aluminum 80's, 63's, 40's, and who knows maybe even some smaller tanks. I know that RPM will drastically change for different Diameter tanks but the whole system will be adjustable for tanks from 4" to 8" diameters with the standard 7.25" being most commonly used.

I figured the best way to do such a variety of tanks would be to add a radiostat but I have heard thats not possible on AC motors, which is what I am going to use. is there any other option for making RPM adjustments?

Thanks

 

[PhilEllis]

So I embarked on a journey to build a tank tumbler for a pair of tanks, this due to getting a screaming deal on a pair of used steel tanks which after paying for I found some rust and pits.

I have found a couple 1/4hp electric continuous duty motors with 1750 RPM rating. For tank tumbling I need like 40-70 RPM so I will need to use a pulley system and maybe a jack shaft setup. However its been a while since I have done even basic math and I fall way short of knowing how to calculate what size pulley will lead the proper RPM. can anyone point me to some simple way of estimating this. I will be tumbling mostly steel 72's but eventually aluminum 80's, 63's, 40's, and who knows maybe even some smaller tanks. I know that RPM will drastically change for different Diameter tanks but the whole system will be adjustable for tanks from 4" to 8" diameters with the standard 7.25" being most commonly used.

I figured the best way to do such a variety of tanks would be to add a radiostat but I have heard thats not possible on AC motors, which is what I am going to use. is there any other option for making RPM adjustments?

Thanks

You are not going to like that setup. I think you would have to reduce the 1750 RPM motor approximately 24 to 1.

Phil Ellis

 

[do it easy]

I just finished my tank tumbler- 1 year in the making! The business end was finished last year, but I added the motor this year because I was tired of using my bike to run it.

At any rate, I'm pretty good with math but was surprised that the numbers don't add up exactly right. I bought the pulley and shaft parts through McMaster, but a 10" pulley isn't quite 10" ID. I did make some estimates to account for the difference between ID and OD, but when gearing down, a small difference can have a pronounced effect.

I have a 3450 RPM motor and it was too slow although everything on paper said it should be just right. I was able to use the extra parts so that I could tumble 7" and 8" tanks and then "shift" gears and tumble smaller AL40s. I'm not sure if friction factors into this at all- I had some leftover parts and was able to make them work.

As far as the math goes, We start our thinking in terms of circumferences and rotations- a pulley that is 3" around will require 4 whole revolutions to turn a pulley that is 12" around. Lucky for us, circumference and diameter are proportional, so a 1" diameter pulley will require 4 whole rotations to turn a pulley that is 4" in diameter.

So going using a 1" pulley on your motor and connecting it to a 4" pulley will slow your RPMs down by 1/4. Lather, rinse, repeat, use bigger pulleys, and don't forget to consider the tank itself and the roller that drives it. You'll get the biggest reduction using a small pulley on the motor and large pulley on the drive shaft.

I have 3450 RPM motor. I used a 1-1/2" pulley on my motor, a 10" pulley and a 6" pulley on the jack shaft, and 10" pulley on the drive shaft with a 4L belt. The drive shaft has 2" rollers. It turns out to be roughly 75-80 RPMs for 8" and 7.25" tanks.

Based on your motor, you might be able use a 2" pulley on the motor and 10" pulley on the drive shaft (2" rollers, 8" tank, and everything else equal). Of course the beauty is in the details, unless you get one of those triple pulleys that have 3 circumferences on them so that you only have to get close

OK, I have a few more tanks to tumble...

 

[Couv]

Have a look at this:

The Deco Stop

and this:

The Deco Stop

 

[NorthWoodsDiver]

so lets assume I didn't want to use any pulley like the commercial tumblers. where would I find one of those slow RPM 120V (or 115V) continuous duty electric motors for a reasonable price. surplus center doesn't have anything nor does my local stores. any ideas. Thanks

 

[603doug]

I machine parts for my drilling co and have a couple of lathes. My large one is perfect for tumbling tanks, probably only cost me 40 bucks in electricity

 

[do it easy]

so lets assume I didn't want to use any pulley like the commercial tumblers. where would I find one of those slow RPM 120V (or 115V) continuous duty electric motors for a reasonable price. surplus center doesn't have anything nor does my local stores. any ideas. Thanks

Look for wheelchair motors, BBQ motors, maybe windshield wiper motors- you're only limited by your imagination.

 

[NorthWoodsDiver]

Yeah I work at a metal fabrication shop and thought the lathe would work but we dont have a large enough chuck for these steel 72's with the rounded bottoms and the 3 phase power costs would kill my boss.

I thought about welding some 2 inch shaft to a plate and welding that to the end of some 8 inch pipe but if the shaft was off even slightly from 90 degrees the wobble at the other end would be drastic.

On the motor issue. I investigated scavenging something but the motors for a bbq seem to be kinda wimpy. if this pans out I will eventually end up tumbling the friends tanks too I bet and some of them have the big 104's and 130's and I fully intend to own some also so I want some power and nothing less than 1/4 hp. I also want something rated for continuous use which seems to come at a cost. I have budgeted $75 for the motor (likely used) on this because I am asking alot. I could spend more but why and with building a booster whip, drysuit drier, tank tumbler, and river creeper I need to spread out the funds all while trying to fill up the gas tank and save for the new drysuit (and accessories of course).

Are there more places like surplus center that may have what I am looking for. Thanks

 

[captain]

Watch ebay for one like this. It should be in the 40 to 1 or 60 to 1 reduction range depending on what the motor speed is. Beats fooling with pullys and jack shafts. Mine is direct coupled to the motor and the tank roller.
Grainger Dayton Gear Speed Reducer, 56c, 60:1 - eBay (item 150245281118 end time May-15-08 13:45:22 PDT)

 

[spectrum]

I just told my wife that I'd build her a lapidary tumbler as a Mothers Day gift. If I'm clever I can kill 2 birds with 1 stone!

Pete