Thread: need help with coffin pop up

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I was tring to do a 4 bar coffin pop up. It was going good till I dreesed it up now it dont pop up. I'm running out of time I need a simple popup or situp rig.
I'm using a 12inch stroke air cylinder had it at about 90 psi. help with the 4 bar or another idea I would appreciate it. oh dual acting cylinders

Does it act like there is too much weight on it, or is something jamming up the mechanism?

Take the clothes off, bunch them up and tape them on a part of the prop where they won't interfere with the mechanism to find out for sure. Either way it sounds like a relatively simple fix, either with lighter clothing or cutting them away to make sure nothing sticks.

First thing I would do, turn off the air to the cylinder and raise it by hand. If you can do that, it's not a problem with your linkage binding.

Next try it with more air pressure and if 90 psi is the limit of your compressor, add a spring to the linkage to help take some of the weight off the cylinder.

Got any pictures of the air cylinder connected to the prop? Can you adjust where you mounted the air cylinder to the linkage? By moving it a inch or so, it will take leverage off the cylinder.

On second thought I would try this before any thing else...activate the prop and give the cylinder a little help by pushing on the prop to help lift it. It takes more air pressure to start the lift than it does to finish it. If this works then you will need to adjust where you connect the air cylinder to the linkage or add more pressure.

I would agree with madmax, sounds like you have either a linkage problem or a weight distribution problem. Think things through logically and go over it all step-by-step. I am almost done with my coffin-sit-up and i can tell you......it involves a LOT of trial and error. Linkage changes, settings, distribution.......Also note that you can have a cylinder with a 12 inch stroke but it's really the diameter of the cylinder that matters here. A relatively small diameter will lift next to nothing in comparison to a larger diameter with the same stroke.

Thanks for the replys i will try them all.

I have the cylinder mounted to a bracket on the side of the pvc pipe. I was thinking it might need to be behind the pvc pipe. Would this hurt the lift of the prop?