Bob,

It looks like you've put a lot of thought into this, but please remember that if there's one thing that screens are good at, it's destroying themselves.

So if you need to rely on the piece of equipment, I think you will be better off buying a proven design. An 8' wide screen box is quite large & prone to problems, and as a bare minimum I'd say you wouldn't want to make the cross-beams any smaller than maybe 6" high x 1/4" thick. Possibly a better option, given that you have no huge time constraints to process the material, would be to find a small, cheap-and-cheerful screen that's maybe 4' or 5' wide & feed it slowly perhaps?

A few things you want to be careful of:

- The line of motion of the force coming from the exciters / vibratory motors needs to be through the centre of mass of the moving screen box. This is difficult to predict without a 3d cad model. If the line of action is out, the screen can rock backwards and forwards like a rocking horse & not move product.

- A 3D CAD model will also allow you to check natural frequencies if you have access to FEA. If the operating frequency is too close to any natural frequencies of the box, it will destroy itself.

For a fairly simple & informative overview of how to get things like motor power, exciters and springs right, ROSTA (Switzerland) have spome design guidelines in their oscillating mountings catalog - or at least they did last I looked.

Sorry I can't be of more help, but to review this properly is a big job & something that needs to be done very carefully. ■

Originally Posted by Lakeside bob

Small box screen I designed "Requesting detailed serious meaningful comments on it"

I have designed a small gravel box screen for my small dirt construction company.

Looked at many screens and the drawings attached is what I have settled on.

I will not screen many yards of gravel a year, but I could have used this small box screen in the past.

I would prefer to build one then rent one, give me something to do in slow times when I have time on my hands. The cost of even a good used screen is more $ then I want to spend.

And the small box screens on the market are too narrow (my bucket is just under 8 feet wide) and do not have grizzly bars that I need for my area which has lots of rocks in the gravel pits. For that reason alone the manufactured screen boxes would not work for me.

I ask that you review my plans and think about it; then make comments on what’s wrong with it and how to improve it.

May be my shaker box will not hold up as designed, I am looking for input.

Whatever comments you make (hopefully detailed) they will be greatly appreciated.

Does one need supports under screen to curve the shape of the screens flat surface? I have included a center support of 3 inch height and two lower 2 inch height supports on each side of the 3 inch height support for the curved surface of screen cloth.

Wheel loader with 2 cubic yard bucket will feed screen. Just under 8 feet wide bucket.

Bucket full dump clearance is 8 feet 5 inches, top of grizzly bar frame is 8 feet 8 inches. Is the screens top height too tall?

2 yards gravel weight is 5,600 pounds.

Screen shaker deck frame weighs 2,200 pounds with screen cloth.

Grizzly tips up to clean off grizzly bars, using the wheel loader bucket to lift the end of grizzly frame at top of deck slope, grizzly has two springs one on each end at the top of the grizzly frame for controlling impact of gravel dumped/placed on the grizzly bars and possible falling down of the grizzly frame onto the screen box frame, slipping off of the wheel loader bucket.

Grizzly bars are adjustable in width opening.

The screen deck shaking is from a 4 feet long 1 & inch square solid steel bar weighing 31 pounds, welded onto the 2 & 7/16 inch cold round shaft that is 5 feet long with one end machined to connect to 1 inch H7 yoke. Connection via other H7 yokes and 1 inch shaft to belt pulley powered by a 12 HP gas engine.

2 & 7/16 inch pillow blocks bolted to 8 feet 6 inch angle iron of 5 inch x 5 inch x 3/8 inch steel, between the two 9 feet 4 inch tubes spaced 10 inches apart. See drawing.

2 & 7/16 inch cold round shaft machined on one end to connect to 1 inch H7 yoke.

Shaker box is 9 feet 4 inches wide with welded on to the ends of the square 3 inch tubes a 3/8 thick 12 inch height x 8 feet 6 inch plate. On top of the screen frame is a 3/8 inch x 12 inch height x 9 feet 4 inch long plate. Forming 3 sides of a box the other side is open for the oversized aggregate to roll off.

Screen deck is sloped at 20 degrees.

Each corner of the screen deck frame is supported by 2 springs for 8 total. Each spring is in a 4 inch wide round steel tube, top and bottom of spring, with 4 inch opening between for a total height of 12 inches.

What size coil spring would work best for this box screen?

In center of screen deck is a screen mounting device to attach the screen cloth to in the center of the screen deck. The screen mounting devise is one 3 inch angle iron welded onto the flat side of a 6 inch wide channel and on each of the channel legs is welded a 1 inch wide thick bar to hold the screen cloth hook.

On each end of the screen where the 3/8 thick 12 inch height steel plate is welded to the 3 inch square tube, holes are drilled through the 3/8 plate for 5/8 inch bolts to tighten the screen cloth on the outside edge of the deck.

Screen frame is made of 3 inch square x inch tubing.

Grizzly bar support tubing top and bottom of grizzly frame is 3 inch square 3/8 inch tubing, the two sides of the grizzly fame are 3 inch square x inch tubing.

Grizzly bars are of 3 inch square inch inch thick tubing.

Could I use just one wide screen cloth 9 feet four inchs or so long or do I need two screens??

Carbon steel or stainless steel for wire cloth which is best? What is performance difference?

I have designed a one deck screen with the grizzly bars above removing the large oversized, will this work or is a two deck screen better?

Material to be screened is pit run gravel that has lots of rocks in it, up to 18 inch size, I would waste to the side of the pit larger rocks rather than putting them on the grizzly bar deck. I plan on using a grizzly bar opening of 3 inches, but as the bars are adjustable I would have the option of opening it larger.

Screen cloth hole opening is to be 1 inch square. Yes I may use smaller opening screen cloth but my need is to remove over size rocks from pit run gravel.

What size pulley on the engine and screen shaft would work best?

I think a shaft RPM of 900 would work.

12 HP engine is 3600 RPM.

With my counter weight design can I get the shake needed to screen gravel??

What problems could I have and possible fixes for them resulting from my shaker design?

What is this screen boxes, speed, stroke, slope (20 degrees)?? Is 20 degrees best for this box screen?

If the ten images attached are not readable I can resend them to you.

What ever comments thoughts you provide will be greatly appreciated.

Originally Posted by misterblobby

Bob,

It looks like you've put a lot of thought into this, but please remember that if there's one thing that screens are good at, it's destroying themselves.

So if you need to rely on the piece of equipment, I think you will be better off buying a proven design. An 8' wide screen box is quite large & prone to problems, and as a bare minimum I'd say you wouldn't want to make the cross-beams any smaller than maybe 6" high x 1/4" thick. Possibly a better option, given that you have no huge time constraints to process the material, would be to find a small, cheap-and-cheerful screen that's maybe 4' or 5' wide & feed it slowly perhaps?

A few things you want to be careful of:

- The line of motion of the force coming from the exciters / vibratory motors needs to be through the centre of mass of the moving screen box. This is difficult to predict without a 3d cad model. If the line of action is out, the screen can rock backwards and forwards like a rocking horse & not move product.

- A 3D CAD model will also allow you to check natural frequencies if you have access to FEA. If the operating frequency is too close to any natural frequencies of the box, it will destroy itself.

For a fairly simple & informative overview of how to get things like motor power, exciters and springs right, ROSTA (Switzerland) have spome design guidelines in their oscillating mountings catalog - or at least they did last I looked.

Sorry I can't be of more help, but to review this properly is a big job & something that needs to be done very carefully.

Originally Posted by Lakeside bob

After 238 views only one reply, why would that be so????

No one has any input for me????

Hello Lakeside bob,

The problem is that screening and building screens is a huge bit of mechanical engineering

science which can be a disaster in the making if the basic laws of physics are not followed.

I will suggest that you visit and the crushing and screening manufactures web sites

VSMA/CEMA; purchase a book about screening materials, read it thoroughly and then

you will understand why it is better to buy or rent one.

Mechanised screening has been around for over a century and it has evolved into

many types of screens including fine mesh screens down to 30 mesh and smaller,

screen drives screening methods including wobble screeners for large cuts of

oversize ores and aggregates, elliptical screens which throw material back on

itself to screen the material in one or more cuts, rotary screens which sift

material while it is rotated by a cam armed gearbox with the screen at 21

degree angles, horizontal screeners which operate at a very slow rate of feeding

and speed for fine screening of halite salts and other materials to remove the

30 plus percent of salt fines to improve its quality.

Then there is the dreaded Tyler method(WHICH I HATE, BUT IT WORKS) of determining what angle the screen should be to screen the material which is:

Take a 5 gallon bucket of the material to be screened and lift the bucket of material to chest height and flip it over and get out your

protractor to determine the slump angle of the material and this is the angle the screen should be set at when it is installed with either a wire rope suspended screen or a screen supported with springs or a screen supported with Rosta mounts or a screen suported with airbags.

Myself and the other moderators and members want you to succeed and not be doomed before you start.

Purchase a book on screening and crushing from the crushing and screening manufactures association www.VSMA.org

www.CEMA.org and read it and then decide.

Speaking to you as a person who was involved in underground mining for 22 years there are small horizontal screeners that are

easily maintained, owned and operated which use small gas engines for power and can cut material at least twice for you and the sceens can be changed to rescreen the material to a smaller cut with little difficulty other than consuming time.

The smallest mobile flat screener can and will do what you want it to do and you can tow it around with a pick up truck.

You can purchased them used as they come on the market on occasion.

You can buy them for less than you could if you wanted to build one because the manufacturer has the opportunities

of scale and a staff of mechanical engineers to do the design work which are discussed in detail in the publications

offered by the VSMA and CEMA folks.

A screener can and will destroy itself in seconds if something is wrong with it(been there done that-actually watched it happen

simply because of the quota system for production. PRODUCTION PAYS THE BILLS AND THE MAINTANANCE DEPARTMENT IS

A PARASITE LIVING OFF THE PRODUCTION DEPARTMENT.

I realize that you have a larger loader but what prevents you from using a small skid steer loader

as many owners of these screens do? BY the way, a smaller front backhoe bucket or a skid loader

will be better to feed it anyway as the screener will be flooded and it will not screen very well due to the

large volume of material being dumped at one time.

These folks have done the work for you and it works well as they have sold, leased and rented many of these

machines since they were brought to the market.

Renting a screener concentrates the time you need the screener to permit you to screen the material in

a very short time. The rental of a screener will be simpler as you can concentrate on screening a large

volume of material in a short time.

It all comes down to examining the rental in a cost per hour basis in the 24 hours you rent it. ■

Originally Posted by Lakeside bob

That you for your reply, Lakeside Bob

Your welcome Lakeside bob. We want you to succeed.

Lakeside bob, by renting a small rental screener and working the machine

continually for 28 to 48 hours will produce a large volume of cut material for

you quickly with only the rental, fuel and lube costs to deal with and you will be

better prepared simply because in the event of a breakdown you will not have to

fix it the rental company will.

I do not know where you are located but I would check with the folks at ez screen as thier

units come up for sale occasionally and they know where they are or were selling them as trade ins

if I remember correctly.

www.ez-screen.com ■

Originally Posted by Lakeside bob

After 238 views only one reply, why would that be so????

No one has any input for me????

Designing an 8 foot wide screen is not easy and will give you some serious problems.

My advise would be purchase an 8ft wide 2nd Hand machine that suits your needs or contact a screen Manufacturer who designs screens to suit your requirements. ■