I was lucky enough to find an old galvanized steel work table at a scrap metal yard that I tipped over to form the U shaped chassis needed to get the tractor bucket in to scoop up the sifted soil. I paid just $100 for the table which is probably less than the cost to make one from scratch. The table dimensions weren't ideal (see video below) but it worked fine after I dug the ground to get enough screen tilt (30 degrees to horizontal). I load the screener from the "wrong" side as the "right" side is too high. This all works fine and I get a great view of the screening action from the loading side.
Step 1: This Video Gives an Overview of the Screener
Step 2: Screen Scrounging & Screen Frame Construction
One piece has a mesh size of about 1 inch and the other about 3/4 inch. Neither piece was large enough to cover the whole frame size needed so I just cut them to fit half of the frame size each.
Cutting the screen was surprisingly easy with the 4-1/2 inch angle grinder. I installed a "super thin" metal cutting wheel and cut away with ease.
The size of the screen and screen frame were based on the size of the "chassis" that I bought at the scrap metal yard. I cut the angle iron on the metal chop saw (with an abrasive wheel).
I bolted the frame together with 3/8 inch hex bolts and nylon locking nuts. No welding used here or anywhere on the screener (other than the bought chassis that was already fastened together with welds).
Although I set up a tent to do outside work, whenever possible I brought the angle iron inside to drill holes with my drill press. (The tent was eventually blown to pieces in a hurricane so after that I moved the screener inside to do the rest of the work).
Step 3: Making and Mounting the Three Hinges
The three hinges were cut cross-wise (radial direction) from the tire and were a "perfect" size for this screener.
I mounted all three hinges while the screen frame was propped up clear of the chassis with a couple of 2X4 spacers. 3/8 inch bolts and locking nuts secure the hinges in place.
Step 4: Making and Mounting the Two Springs
I tried using springs made from radial sections of the tire (same as the hinges in Step 3) but that shape was a bit too flexible. The springs shown were cut from the center circumference of the tire. Each spring is about 16 inches long before being formed into the required U shape.
The jig shown in the photo is pretty well essential to hold the spring in position for drilling.
I clamped the pressure treated 2x4 leg, along with the tire spring, in the jig and drilled the holes completely through the whole works with an extra long 3/8 inch twist drill bit.
After I removed the spring from the jig I ran a 1/2 inch drill bit through the 3/8 inch holes to make it easier to insert the 3/8 inch bolts.
Once mounted on the hinges and springs the screen frame and chassis have no metal to metal contact. The V belt makes another "rubber" connection to the engine. This all helps make a smooth running and quiet screening machine.
The jig labelling (photo above) shows where a hole is drilled for a "spring tension bolt". The idea was to install a bolt with washers and a nut to adjust the bulge of the spring if the screener frame, and belt tension, loaded the spring down too much. After many tons of screening the spring has maintained its shape so the spring tension bolt has not been tried.
Step 5: Engine and Drive Train
I want this screener to last so I selected 3/4 inch pressure treated plywood for the engine mounting panel and the engine platform. The pictures show the angle iron brackets that support the platform and engine. The brackets are held together with 1/4 inch hex bolts and locking nuts.
The 4 inch dia pulley on the engine drives the 6 inch dia unbalanced pulley that gives vibration to the screen. The pulleys are linked together with a cogged V belt. A 4 inch dia spring-loaded idler pulley takes up the belt slack under vibration and keeps the belt where it belongs - on the pulleys.
The vibrating pulley is mounted on a shaft and the shaft is mounted in two inexpensive flange bearings that sandwich the bearing plates. (I made two identical plates to give enough rigidity.) The bearing assembly is secured with bolts and locking washers as well as locking compound. The bearings, that I had on hand, require a large clearance hole - a couple of the pictures below show these holes being made with a metal cutting hole saw. The sealed bearings have held up so far without any problems.
I mounted the bearing plates with one 5/8 inch hex bolt to the screen frame. The plates hinge on this bolt until the system is bolted permanently in place. Once the belt is in place the bearing plate is pulled up with the belt tensioning turnbuckle. I used chemical locking compound on the threads of the turnbuckle to prevent loosening. After adjusting the turnbuckle I always double check that all related nuts and bolts are fully tightened.
When adjusted and tightened the screen frame, bearing/pulley plates, and turnbuckle, form a rigid triangle that all vibrate together.
Step 6: Covers and Access Features
I cut down a large plastic storage container for the engine rain shield. A bungee cord holds the cover in place.
Installing, adjusting, or removing the engine pulley is made easy by having access through a circular door that I jig-sawed out in the engine mounting panel. The access door is held in place with three wood screws driven in around the cut line.
I protect the screener with a large plastic tarp during the winter months.
Step 7: It's All About the Shake
I did some experimenting with various weights to get what I ended up with here. One picture in this step shows the belt thrown off the pulley due to too much weight and too much vibration. But other factors play a role in getting the desired shaking action and to keep the belt secured on the pulleys. For example the idler spring may not have enough tension, or the pulleys may not be in proper alignment, or the turnbuckle might not be tightened up enough.
It's easy to adjust the weight on the pulley if you end up with too much or too little vibration. Just change the weights on the eye bolt - making sure that the last component is a locking nut.
I found that with the present vibrating pulley set-up (main photo) I needed to run the engine at pretty well full speed to get good vibration after a heavy load of soil is dumped on the screen. A different size pulley or pulleys and/or more weight on the vibrating pulley might allow a slower engine rpm to get the desired vibration.
That grey gunk on the pulley and shaft is anti-seize compound. I used this material on all parts where there was a chance of metal to metal seizing - highly recommend using it as the screener will be outdoors most of the time.
Step 8: Where There's Shake There's Break
A higher quality turnbuckle and better mounting alignment would make this part last longer.
A turnbuckle with swivelling mounting ends should solve this problem totally - so far I haven't found one of suitable size.
Anyway, changing the turnbuckle is only a 15 min job and the turnbuckles that I have been using are cheap.