Making cylinder and piston for a ram

[Lanza]

I'm making some cylinder shafts for a hi-ab crane jack legs for a truck, we can not get replacements. I know the pistons are welded on, not good from a maintenance point of view. My question is about the piston face having a recessed undercut, and the recess has a very slight dish to it. I wonder if anyone knows what is the purpose of this concave dish? Both have it, one cylinder has been remade which is why you see one shaft is solid. The OEM shaft is hollow and was originally hard chromed.

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• Lanza
• May 23, 2022

Drawing showing dished recess

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• Lanza
• May 23, 2022

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• Lanza
• May 23, 2022

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• Lanza
• May 23, 2022

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• Lanza
• May 23, 2022

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• Lanza
• May 23, 2022

 

[eKretz]

I've read that the dishes, when present, are there on cylinders that feed into the end of the cylinder to ensure there is a high surface area available to hydraulic pressure even when the piston is fully bottomed out. Otherwise a situation could arise when the piston is bottomed where the available surface area was only as much as what the hole admitting fluid has in cross sectional area.

 

[DDoug]

I've read that the dishes, when present, are there on cylinders that feed into the end of the cylinder to ensure there is a high surface area available to hydraulic pressure even when the piston is fully bottomed out. Otherwise a situation could arise when the piston is bottomed where the available surface area was only as much as what the hole admitting fluid has in cross sectional area.

Yup, or maybe something to slow down the cylinder at the very bottom, a cushion of sorts.

 

[john.k]

Normally ,crane outriggers retract unloaded,but one issue is oafs running the piston up to a hard hard stop when its completely unnecessary.....the net result of this with a Hiab is the lower end nut seal is blown out of its groove,and oil goes everywhere.......Other issue is the ram gets a lot of sideload when the truck is jacked up on a slope ...........funny story about that ......steep slope ,driver jacks the truck on both sides ,back wheels clear the ground,truck slides away downhill on the outriggers and crashes into a half finished house in the next lot.