Suggestions on how to keep a flat plane table, in orbital motion, from spinning or rotating. 2

[ABabymaker]

I am needing to move a flat, horizontal table (that will hold a 30 pound container) in a 4" orbital (or circular) motion of about 800 RPM, but NOT SPINNING (Table must face the same direction when in operation).
I am planning on using a 1hp motor, vertically mounted, with a 2" offset cam (with bearing) mounted to the table. This moves the table orbital motion.
To hold the weight of the table and container (also keeping the load off the motor), I am using 4 rods with swivel ends (load rated) mounted from each of the 4 corners of the table to 4 'like' positions around the base of the motor. (Think of the motor centered vertically between 4 rods supporting a table).
This seems to work well except the table will 'twist' or 'turn' the direction of the motor rotation, causing the table to 'bind' (the 'twisting' causes a lowering effect of the table of about 1/4").
My QUESTION: What can I do/use to keep the table from TRYING to spin?
1. Maybe an identical 4" cam (on the same plane), using a rod rigidly connected to the table (thinking of the (2) wheels connected on an old time locomotive). Although this may not work due to 'twisting' of the table.
2. Maybe a rod rigidly connected to the table, then, rigidly connected to a 'sliding arm'/piston/OrThingyIdontKnowTheName (thinking of the same locomotive but the piston assy that drives the 2 wheels). This way DOES CAUSE a 'slight' wobble but IS acceptable.
3. Or there is a better way?

http://www.babytronix.com/Orbital_Table.jpg

 

[tbuelna]

A picture is worth a thousand words.

 

[3DDave]

How many Gs is that going to see? It feels like that's shaker table territory.

I'd suggest bolts.

 

[ABabymaker]

tbuelna
I will try to get a pic up tomorrow. This might help... Visualize a cup or glass on a coaster (the table) supported on it's edge at 4 equal points with 4 rods extending down. (This enables the table to hold a heavy weight, during a 4" orbital or circular motion, not putting a side-load on the motor.) The motor is mounted vertical (under the coaster) attached via a 2" offset cam. Hope that helped.
3DDave
About 3-4 Gs. And Yes, its a shaker table, rock crusher.
Bolts would not work as the table must move in an orbital or circular motion without trying to spin from the force of the drive motor.

http://www.babytronix.com/Orbital_Table.jpg

 

[MintJulep]

Base plate with an east-west slot.

Moving plate with north-south slot.

Sliding cross in between.

 

[gruntguru]

You say "cam" but I assume you mean "crank" or "eccentric".

To produce true orbital motion with no rotation, you need to add two additional eccentrics (non driven) for a total of three, laid out in a triangle. This will make your struts redundant. For best load capacity use 4 eccentrics - one driven and three passive - located towards the corners of the table.

je suis charlie

 

[TheTick]

4-bar link with equal-length parallel arms.

 

[btrueblood]

I have a lapping table at home, for polishing slabs of rock. The lap pan is mounted on springs that allow some lateral compliance (to create the orbital motion), but no more than a few degrees of rotation. The multiple drive points would work as well.

 

[rb1957]

all the points on the table are rotating about different centers.



another day in paradise, or is paradise one day closer ?

 

[3DDave]

One of the items already mentioned goes by the name Oldham coupling.

I was referring to stopping the table from moving around the room; I would probably have seen it quicker as motion platform, but I get it.

Are you sure about the load? An online calculator suggests 36 gs. Presently too lazy to run the calc myself.

 

[MintJulep]

Oldham coupling. Thank you.

Couldn't recall the name.

 

[ABabymaker]

gruntguru: You are correct, I do mean 'eccentric'. I like the idea of the additional eccentrics, but as these being horizontal, I don't see them holding weight on a side load. (I could be wrong tho, I am NOT a mechanical engineer, but I get by. I am more of an electronic and optical engineer.) That is why I was using the struts, to hold a total weight of around 50lbs including table and container. If I go this route I think I will still use the struts.

3DDave: Hmmm. I use Oldham Couplings all the time for when shafts mismatch. I can't seem to relate (some call this a brain fart) to where I would place this? Center? Sides? This is another I think may work. And I could be wrong about the G's, that test was done with a larger container and a cheapo accelerometer.
MintJulep: Your suggestion, where were you thinking it may go?

This is my first question on this awesome site. (Yeah, I'll answer questions for 'payback'.)
Thanks for ALL the replies, they were very helpful (it got my dusty wheels turning) and I am hoping to get more suggestions.

 

[MintJulep]

You could implement the Oldham mechanism as an annular ring between the support plate and the moving plate.

The following picture for example. It's opposite my original description, in that the slots (42, 43, 44 and 45) are in the middle piece and the pins (46, 47, 48 and 49) take the place of the "cross", but the function is identical.

 

[ABabymaker]

Looks interesting. I think I can adapt this into what I need.
I am wondering what this can take @800rpm, and longevity. Time testing will tell.

And what I thought would be almost impossible, I was shown a few ways to tackle the problem.
Thankx EVERYBODY! Wish I would have found this site a long time ago, I might have gotten somewhere by now!

 

[3DDave]

As I mentioned, I think the load is closer to 40gs than the 4gs you posted. That will make a difference in longevity.