Rotate using hydraulics

[Brian Matlack]

Hi!
I'm new to the forum so thank you in advance for your patience.
I'm not an engineer, just an ole farm boy trying to build some hay equipment.
I am using Inventor 2012

I am looking for a way to take a 4"X4"X60" square tube and rotate (invert) it 180 degrees (length wise) using a single 12" stroke hydraulic cylinder.

Any thoughts, ideas or guidence would be greatly appreciated.

Thanks again in advance for your help. Have A Great Day!!

[PinkertonD]

I am looking for a way to take a 4"X4"X60" square tube and rotate (invert) it 180 degrees (length wise) using a single 12" stroke hydraulic cylinder.

Hi Brian, welcome to the forum.

Turning anything 180-deg with a straight action is always going to be difficult, but there are some cheats you can try.

1:
Does it really have to be a full 180? Can it be 175? That may be doable without cheating.

2:
At the end of the extending drive of the cylinder have the clevis (or whatever) contact a compression spring about 2" out from full 180. When the return is selected, the spring will start the movement back and overcome any over-center lock that may have been set up. You could even have a similar spring on the return end to assist starting.

Thinking... thinking... thinking...

[RWOLFEJR]

Hi Brian and welcome to the forum,
Like Dave said... do you really need 180? what he has in mind would surely be the least expensive and least complicated way to go.
If you do need 180 then let me run this by you...

Couple questions...
Where will your center point of rotation be? Middle of the tube? End of the tube? Does it matter? What do you have in mind for holding the position once it's there? Do you want the cylinder to do the holding or will you have a catch or pin etc. to lock it in place once rotated? Will this thing cycle all day or just at the end of a row or dozen times a day two days a year?

Also going to need to consider the weight of whatever your load is and what your cylinder will produce. How many psi available off your hydraulics and what diameter cylinder? I don't recall what my old R or 820 put out but guessing you ought to be producing close to 1,000 psi off your pump?

Right off... I'm liking the idea of changing your straight line power motion of the cylinder to rotary motion via a gear and rack. You guide your ... say... 18" long gear rack (little bit extra to allow being off a bit when mounting) that is bolted into the end of your cylinder rod. Guide it with with a couple of piece of greased up flat stock and as it moves it rotates a gear that is keyed to a shaft that is welded to your tube. Maybe the end of the shaft that's going to mount to the tube is welded onto a flange to distribute the mounting load over the tube better. You'll need to support that rack on three sides so it doesn't load your cylinder rod cock-eyed or try to pull away from your spur gear.

You can then adjust for your available power if need be by adding a second gear on a idler shaft to get a gear reduction and still develope the needed amount of rotary motion. Problem with this arrangement might be a possibility of some float at the ends of the stroke but a stop at either end ought to fix that. Maybe make the stop adjustable?

So say you have a standard-ish 2-1/2" farm tractor cylinder... 1,000 psi... You'd have about 4,900 pounds of force on the extend and without doing the math to take out whatever the rod diameter is you'd have roughly say... 3,000 pounds anyway... on the retract.

So you go maybe 6 pitch x 36 tooth spur gear that has a 6" pitch diameter and you'll get 180 degrees of motion with about 9-1/2" of your stroke. That's a nice stout gear pitch that'll take some abuse. If you do indeed have say... 3,000 pounds of force from the cylinder then at 3" out (distance from gear center or your pivot point) you would have 9,000 inch pounds or 750 foot pounds of torque to rotate your tube.

Load on the tube (bail of hay or whatever) will need to know where this pivot point is as I mentioned first off.

You might be able to do this a lot cheaper (remove cost of rack and gear) by mounting a couple old motorcycle sprockets and a chain to the beam your cylinder is fixed to. Then weld a tang off of one chain link to connect to your rod clevis. One sprocket is and idler and the other connected to the shaft that'll spin the square tube. Stroke the cylinder... moves the chain... spins the sprocket that holds the shaft that connects to the tube...

If those ideas don't grab ya I'm pondering another possibility but I don't quite have a grip on it yet.

Good luck,
Bob

[PinkertonD]

Another thought instead if using a spring, what about a bias of the balance of the weight/load in favor of the return trip. If you are inverting a tub, then have the butt-end of the tub hang further out from the center of rotation than the lip-end. At the end of the 180, it is going to want to head for home like a rented horse.

Another thing I thought of in the middle of the night is two shorter cylinders joined back-to-back. Bear in mind I have not fully thought this one through -- yet. Have a pressure relief valve in the line between the two. The release pressure would be a little greater than the load but less than the max available. That way the first cylinder extends until it is all the way out and then loads up the valve. The flow through the valve then extends the second cylinder. That way each cylinder is only providing 90-deg of rotation and easily doable. Same-same for the return trip.

Still thinking...

[zeke]

If you can live with slightly less than 180, per Dave, then a reverse slider- crank mechanism solution could do it, which is cheaper but not as good as RWolfe's rack and pinion.

[LutiiChell]

im no tire expert but doesnt that all go out the window when you start lowering and changing camber?
i currently rotate all my NON directional tires on my other cars. ive rotated front to back only on my e30. my wifes are staggered so thats a no brainer. unless you work at tires plus who put 1 rear 9 inch wheel on the front and the other on the back on my wifes 540.

Edited language use... Admin (Kelly).

[mcnurlin]

Brian, I realize this is quite late for a solution to your problem. I found your post while I was researching a similar application myself. The Peaucellier-Lipkin linkage is the solution I went with. You can easily get more than 180 degrees of rotation from a linear input.

[jboggs]

Can you post a graphic of your solution? I don't see it in the normal P-L linkage.

[mcnurlin]

Here is my initial layout in SolidWorks. By applying a cylinder to the top pivot you can see that pushing from left to right will rotate the red link 180 degrees CW. With a dog leg in the in the lower links of the rhombus it could easily exceed 180. My goal for the application I'm designing is 230 degrees of rotation. I haven't put any math to the forces yet but it does appear to be fairly efficient throughout the range.

[jboggs]

Look at the second diagram above. It appears to me that the red and gray links are in an indeterminate state at that point. They could go either way from there. Have you actually built this thing? Does it work reliably as expected?

[mcnurlin]

Look at the second diagram above. It appears to me that the red and gray links are in an indeterminate state at that point. They could go either way from there. Have you actually built this thing? Does it work reliably as expected?

The red link in the center picture is not in an indeterminate state because the force at the floating end of the link is almost perpendicular to the link. I uploaded a video to YouTube that shows this more clearly. The red link is pivoting 262 degrees in the video. There is more range available, I would say the limit with this type of mechanism is about 350 degrees.

I'm in the design stage of a turntable that need to have rotate 225 degrees, so no I have not built this yet. I'd guess I'll have something built by February or March. It's for an in-house project so the priority is low.

If the video is block by the ad or if you want to see it full screen here's the YouTube video link