How best to motorise a soil sifter

May? It's got near zero fan cooling plus greatly increased current. Maybe it takes Sherlock to work out what's going to happen.

NT

A jigsaw would be easy to mount.

Maybe like this:

It's good but I would think the sifter needs greater movement so as to agitate the soil much more.

You possibly need it to stop and change direction quite rapidly. Using smaller sieves will allow them to hit the sides on the direction change and shock out the earth that sticks in the holes. You need to mimic the operation as if you were doing it by hand where you will find it doesn't work on anything but 100% dry dust if you are gentle.

Last weekend I sifted the contents of a full compost bin by hand.

I used a vibratory motor, 240V about 150W, to shake a hopper. I think it was made by Vibtec. This could be mounted either way but horizontally it moved the material forward. It was adjustable by moving the bob weights.

If I were doing this I would use a belle mini mixer and buy a second drum to which I would fix mesh as a trommel.

AJH

Use a motor fitted with an large eccentric (wooden) cam. Fit elastic bungee cord to to the motor side of the box to provide the return 'spring'. Fit a end stop to the box travel so the cam disengages with the side of the box at some point during the motor revolution and the box stops with a shock. Perhaps fit a weaker bungee cord to the other side of the box to stop it from tilting when being pulled back by the bungee on the motor side

Windscreen wiper motor?

Hmmm, I've seen some fast and pretty violent agitation from large stepper motors as used in line/laser/3D printers. An application for a Raspberry Pi?

Well, it look ok in principal but as others have mentioned I'm not sure how long it would last and I'm not sure it is fast enough, depending on the size of the stuff you are sifting.

When I have use a garden sieve I think I oscillate it much faster, basically so that the mass stays still and the sieve moved back and forth underneath it. More like pulling a tablecloth out from under the crockery rather than pulling the crockery onto the floor. ;-)

As would I.

Sounds reasonable.

Also seen later post. ;-)

At full speed maybe but the variable speed one I have can be set to run quite slowly and already has the gearing built in.

Yes, but only from how I use a sieve by hand.

Understood.

Cheers, T i m

Outside of the dynamic load affecting how the frame sat, the only way that would happen was if the running gear wasn't very good or you hit the end stops? Ignoring such issues, all the inertial forces should (would?) be produced and absorbed by the person shaking the sled (Newton's third law of motion).

Increasing the directly coupled mass of everything except the sled would help that's for sure (Newton's third law again), as would doing the same thing using braces and even (ideally, low electricity) guys.

Cheers, T i m

Nice bit of woodwork

Bill

You may or may not like to look here

I made it years ago for a specific task and it was OK but some of the parts should have been metal rather than wood.

Subsequently I have bought a used Sheppach one which is OK but not perfect. hth Bob

Thanks

That's the closest I have seen to what I had in mind.

Can you remember the wattage (or HP) of the motor? I guess I would need something similar as a normal drill would not have the power.

I used an induction motor - 1/2Hp 6 pole 950rpm if run from 50Hz. I ran it from a variable speed drive as seen in the video. From memory, the belt speed reduction was around 5:1 and I ran the inverter around 25Hz which would give a crank speed of 95 rpm. Tweaking the speed did make a difference to the effectiveness/throughput from day to day depending on the soil dampness. The stroke was also adjustable and I seem to recall only needing just over the pitch of the mesh for effective performance.

If you want finer sieving, then adding a second layer of the same mesh offset by 1/2 square in both directions works well rather than search out a finer mesh.

hth

Bob

That's welcome! I was thinking I might need 2 HP or more.

My best guess was 120 rpm so your rpm figure helps verify that.

The variable speed drive sounds ideal but even second hand ones on ebay are quite expensive. Mind you, pairs of stepped pulleys as used in a lathe are also quite costly.

OK.

That's a surprise. I'll bear it in mind though I suspect that some of the clayey soil here will need a bit more violence!

I've got that covered. The fixed mesh is very coarse at 50mm but the sled is sized to allow my normal garden sieves to fit inside. In which case, the 50mm mesh will do little more than help support them.

I need the coarse first size as some of the ground here seems to have had a past life as a building site. ;-)

Pulleys can easily be made from wood (ply or mdf) slather with thinned varnish just in case they get wet. Either Vee groove for standard belt or flat driving surface with cheeks either side (to stop the belt walking off and a toothed timing belt or poly vee belt run on its back makes a good substitute for a flat belt and readily available on ebay etc.

You will possibly find it easier to source a used 4pole motor than a 6 pole so you are looking for 15 to 16:1 reduction. Trying to do all the reduction in one hit might end in tears but two stages of pulleys at 4:1 should be a doddle.