Trommel Build (rotary sieve or riddle)

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barryjyoung
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Joined: Sat Jul 30, 2011 12:25 pm

Trommel Build (rotary sieve or riddle)

Post by barryjyoung »

I am attempting to set up my foundry to deal with weight issues as quickly and efficiently as possible. I do not have a desire to lift buckets of sand any more than absolutely necessary because I want to use this foundry when I am in my 70's. The thought is to design and build what will be needed in twenty years now while I still can rather than stop making stuff because it is beyond my abilities then. Sort of working for a demanding old fart I have not yet met. To that end, I have built a trommel for riddling the sand after it comes out of the muller (which is currently undergoing a slight re-design per Harry's excellent recommendations).

I started by obtaining all the crap necessary plus a little that will end up in the junk box when the thing is done. I bought two 20 inch (BMX size) girls bicycles (girls bikes are almost always cheaper and not as hammered). From these I took the chain, sprockets, and rims. The chain and sprockets were used on the muller. Ten 2x4 studs, two boxes of 5/16 X 1/2 pop rivets with three boxes of back up washers (save money, buy 3/16 flat washers from the hardware aisle instead), a box of 1 1/4 #6 and a box of 1 inch #6 drywall screws, two rolls of Rubber Mastic Tape (found in the electrical aisle as Scotch Moisture Resistant Electrical Tape since they changed manufacturers this month), a roll of 1/4 inch square hole wire mesh fabric, and ten 1 3/4 inch high rigid casters were acquired from your friends at Home Depot. The bike shop sold me 6 rim strips for 20 inch wheels. Gathering all this stuff took about a week cause I am old and slow.

Assembly was pretty easy. The wire mesh was 4 feet long which seemed like a real good length after I considered the alternative, which was another cut that I would not need to make if I could just be happy with a four footer instead of a three footer like envisioned. I unwrapped the roll of fabric and it immediately tried to unfurl itself like Old Glory. Having one of the bicycle rims handy I captured its ass deftly and with great grace by putting the rim over the end of the rapidly expanding roll. Overlapping the fabric about three inches, I cut along one row of holes with tin snips. I drilled the spoke holes in the other two rims to 3/16 which they almost were already. Starting with one of these prepared rims at one end of the fabric, I pop riveted through the spoke hole nearest the valve stem hole and one layer of fabric With a back up washer to keep the rivet from pulling through the fabric. Another rivet 180 out from the first with the fabric expanded as much as possible inside the rim made it sort of a big floppy mess. Rivets at 90 degrees made it start to form into a circle. I drilled out the first rivet and replaced it, this time going through both layers of fabric. The next step was filling in rivets around the rim leaving no more than two spoke holes empty between rivets. After this was done I went to Harbor Freight and bought a pneumatic rivet gun because those hand powered ones suck way too much for a big project like this. This was a great success, I highly recommend this inexpensive tool even if you never use it on another project. With my new power riveting capacity I went to town and everything went way way faster with less cussing. I took off the non drilled rim and replaced it with a drilled one then drilled the third rim. It was riveted in place in minutes rather than hours. No need to drill the first rivet out as I knew now how big to make the circle. I also riveted the middle rim in place with a few rivets using measurements from the ends to get it straight. This failed miserably and when I rolled the tubular sieve on the floor the middle rim wobbled like crazy. No problem, I planned to deal with that later. I ran a row of rivets every fifth hole from the end rims all the way to the center to seal the overlap in the fabric. The rivet heads were 1/16 tall above the interior surface of the rim and would make a loud thump thump when test run on the casters. That is when I came up with the tape idea. I cut pieces of the special electrical tape (which is 1/16 thick) and stuck them between the rivets. Then I covered the tape and rivet heads with two rim strips each to make a smooth and shock absorbing surface inside the rims. This really makes a difference. The four wooden frames were next, I added 1/2 inch to the 16 inch radius of the rims to determine the size of the frames and built half lapped frames glued and screwed (1 1/4 #6 screws) together from 2x4 . Then I dadoed and half lapped the four frame studs to locate each of these frames and glued and screwed them into place. Next I shimmed the rims away from the inside of the outer frames with 1/4 inch plywood on four sides then attached each of the four casters with three 1 inch #6 drywall screws to allow the caster to be riding inside the rim. I used a wooden gauge I made on the bandsaw to position the center rim and pop riveted that in place. This rim was like the others taped and covered with rim strips. Once I have decided on a motor, the vee belt from the motor will ride on this center rim making it turn.

This was a simple and I hope very effective option to a power riddle. I will post more pictures once I have the motor on.

Please feel free to comment or ask questions if you have any.

Barry Young
Young Camera Company
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Harry
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Re: Trommel Build (rotary sieve or riddle)

Post by Harry »

Be interesting to see how this works out and what you learn from it Barry. I am in the same position as you in that I want to make things easier, not only for my coming years but also just to be able to do more now without getting worn out. Having an overhead dump with riddled sand in it would save considerable time as well as work.

Sand handling is probably one of the biggest places to save grunt work in the foundry, from shakeout and processing to handling molds full of sand these are areas I think about for my eventual foundry 2.0

My current foundry is quite workable but it is also quite small so there is not a lot of room for adding to it so the new digs will be a complete rebuild in another location on the property.
I'd rather laugh with the sinners than cry with the saints the sinners are much more fun...
Muller
mite5255
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Joined: Thu Jun 02, 2011 1:11 am
Location: Caboolture Qld Australia

Re: Trommel Build (rotary sieve or riddle)

Post by mite5255 »

At this point in time I don't mind the manual handling of the sand, I find its damn good exercise and I need the exercise. At times it sure does gets my heart rate up tho

Mike
When life gets tough, remember: You were the strongest sperm :)
blindpig
Posts: 34
Joined: Thu Jun 02, 2011 5:06 pm

Re: Trommel Build (rotary sieve or riddle)

Post by blindpig »

Really slick idea Barry,
Is there going to be a potential problem with weight deforming the cylinder as material is added inside? Might want to consider bracing between the rims to prevent any such distortion (maybe some metal angles connecting all three rims,bracing against sagging, etc.). Just a thought.....
Keep up the good work and as a 70+year old I think your planning ahead is the smart thing to do ('cause it really ain't gonna get easier as you go along,still as much fun though).
Don
barryjyoung
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Joined: Sat Jul 30, 2011 12:25 pm

Re: Trommel Build (rotary sieve or riddle)

Post by barryjyoung »

Hi Don:

This trommel will only see a very small amount of sand at a time, it will be fed from the Muller via a conveyor. The conveyor will have buckets made from electrical junction boxes. I hope there will be no need for additional support, but that is an astute observation and now I will be looking for it.

I figure if I can barely lift my lazy butt out of bed at 50, casting at 70 will be quite a challenge.

Barry
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