How to make a air cylinder push up a gate

[g_speran]

Hello All,
I am building a project where I am looking to have a pnuematic cylinder mounted underneath a ramp and push up a gate that is hinged, to 90 degrees, however I am struggling on how to get this to properly function. From center to center of the 2 clevis mounting holes, on the cylinder, is 15 3/8" (in the closed position). The cylinder has a 7" stroke, therefore in the open position, from center to center of the clevis mounting holes is 22 3/8". I am not sure where the cylinder needs to be mounted underneath in order for the hinged gate to be pushed up to a 90 degree, at a full stoke and parallel when fully retracted.
I have pictures of what I am trying to accomplish but it is 10MB in size so I am not able to upload it. Pictures are woth a thousand words :-) If you think you can assist me, I will be more than happy to send you the pictures (6 in total)

Thanks
Gary

 

[g_speran]

I just created a web page to show the pictures. please be patient for the images to load.

Here is the link:

http://g_sperano.tripod.com/gate/gate.htm

 

[Danger]

Good pictures, G_speran. Welcome to PF.
I don't think that where you mount the cylinder is terribly important. The length of the attachment bracket on the rod end will determine the starting and ending positions of the gate.
Math isn't my thing. In a situation like this, I just cut out pieces of cardboard in the right dimensions, nail them to the floor, and muck about with things until it works right. Then I transfer the resulting points to the real equipment.

 

[g_speran]

I've been mucking around with it for about 11 hours and no success. If I munt the cylinder so that it is at Full stoke and the gate is at 90 degree, then when it goes to close, it is fully retracted and the gate is at about a 20 degree angle.

There has got to be some math to this :-)

 

[Danger]

Well, I know that it has to do with leverage ratios, but I don't know how to work it out. You'd have to figure how much linear displacement correlates with 180° of rotation, and scale the mounting lever appropriately. (I know what I mean, but I'm sure not expressing it well.)

 

[g_speran]

Any other recommendations. Any mathmetical calculation anybody have to help fugure this out?

 

[pantaz]

Since you need to move it ninety degrees, I look at it as an isosceles right triangle. The equal length legs denote the lever's starting and ending points, and "C", the junction of the legs, is the pivot point. The hypotenuse is the cylinder's travel, seven inches, therefore the length required for the arm is 4.95 inches (from center of hinge pivot.)

This is just a rough sketch, not to scale.

 

[Lazer57]

By creating that distance from the bottom of the gate it increases mechanical advantage (i.e. the further away you are from the door hinge, the easier it is to push the door open). The cylinder is probably best parallel to the ramp, although you want to make sure that the joint between the cylinder rod and the gate has enough room for the gate to go to 90deg.

 

[Ranger Mike]

i think you need at least 45 degree angle ( cylinder to gate) to properly actuate this.

 

[Lazer57]

i think you need at least 45 degree angle ( cylinder to gate) to properly actuate this.

its the moment generated about the hinge that matters and that moment arm would only get smaller with an angled cylinder. its like rotating an x shaped revolving door; you don't need to put force on a particular door, they all act as a moment arm allowing you to rotate the door. plus if you're trying to connect directly to the gate, much of the force will be trying to pull the hinge apart and it wouldn't be very easy to set it up so that it works properly through the 90 deg rotation.