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CCWKen
08-24-2005, 12:30 PM
I finally got a round-tuit and started cutting down some cylinders for the Kenbota. I'm adding a front-end loader and got some cylinders from a wheelchair lift. The cylinders are about 20" too long so I'm shortening them to 32" eye-to-eye.

In any case, I cut the first cylinder and removed the piston and rod. This is a pic of the piston. Notice anything strange?

http://img.photobucket.com/albums/0903/CCWKen/Loads/HydraulicPiston.jpg

I guess they don't use seals on this piston to allow blow-by to slow the cylinder down. (Wheelchair lift) The bore is 1.5 and the aluminum piston measures 1.480". That seems like a lot of slop.

Here we go shifting gears again. I now have to find a 1.5 piston seal kit and modify or make a new pistion(s).

HTRN
08-24-2005, 12:33 PM
Try Bishop. They sell tube, rams, pistons, glands, etc. in a huge variety of sizes.

It will probably be cheaper just to get a new piston with seals.


HTRN

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This Old Shed (http://thisoldshed.tripod.com)

tattoomike68
08-24-2005, 12:49 PM
If it has a single port it is a volume cylinder and the "piston" does not need seals, it can have holes in the piston and still work.

that piston looks like steel.

make a new piston from aluminum and use 2 3/16" o rings.

CCWKen
08-24-2005, 01:35 PM
These are dual action cylinders. They have ports at both ends. How much clearance should I allow on the piston? The current .010 (.020 total) seems pretty loose. But I guess with seals, it's ok?

Sandy H
08-24-2005, 02:16 PM
Not a cylinder expert by most accounts, but what pressure range do these cylinders run? If you're looking for decent pressure ratings, try looking at a Parker catalog for o-rings, gland seals, rod wipers, v-seals etc. The following link points to a lot of the available catalogs and might point you in the right direction.

http://www.parker.com/catalogs/catalog.asp?nav=1&type=2&id=68

Good luck.

Sandy.

MechHead
08-24-2005, 03:13 PM
Tattoo, would you mind explaining the meaning of a "volume cylinder" for me? Also, what would the point of putting holes in the piston be? If you wanted to slow the linear speed of it down, wouldn't it make sense to use either an external fixed orifice or an adjustable flow control? The single ported cylinders I work with are single acting, and either gas charged, spring return, or gravity return.

As for seals, if you are going to be using O-rings at pressures higher than 1000 - 1500 PSI, make sure you cut a groove wide enough so you can use a backing ring to protect against seal extrusion.

MechHead
08-24-2005, 03:27 PM
BTW, you might have a problem with extrusion at .010 radial clearance; you might want to go with lip seals. Ideal diametral clearance is .003 to .007.

tattoomike68
08-24-2005, 05:49 PM
((Tattoo, would you mind explaining the meaning of a "volume cylinder" for me? Also, what would the point of putting holes in the piston be?))

the piston is the shaft and the part that looks like a piston has that has holes or groves just keeps the shaft in the middle thats all, and oil cannot get trapped acting like a stop. also all the seals are in the head.

If it has one line it is a volume cylinder.

((The single ported cylinders I work with are single acting, and either gas charged, spring return, or gravity return.))

yep thats them.

wierdscience
08-24-2005, 07:00 PM
Here you go Ken,go to-

http://www.mcmaster.com/

Look for item # 9505k85,you will need two per piston facing in opposite directions.

You might get away with the pistons you have,but I would make new ones with .005" clearence and leave about 1/4" of meat between seals and at least 3/16" from the end of the piston to the ring grooves.

MechHead
08-25-2005, 08:28 AM
If you go the way of the lip seal, keep in mind if you have any bending stress at all in that cylinder you will need a wear ring in between the two lips. Otherwise, the piston will wear oval and leak.

MechHead
08-25-2005, 08:31 AM
Tattoo, Ok, I see, the volume cylinder is used as a regenerative advance cylinder, except without the external connection line. Haven't seen one of those before.

CCWKen
08-25-2005, 06:14 PM
Thanks "Wierd"! I'll have to make a longer piston and what MechHead says makes sense. I'll have room for wear rings too.

Thanks!
Ken

TGTool
08-25-2005, 08:28 PM
Ken,

If it is in fact a one-port cylinder as tattoo suggests and you make a new piston with seals, don't forget to vent the rod end unless you're using the air compressed there as a return spring.

Jan

CCWKen
08-25-2005, 08:43 PM
<font face="Verdana, Arial" size="2">Originally posted by CCWKen:
These are dual action cylinders. They have ports at both ends. How much clearance should I allow on the piston? The current .010 (.020 total) seems pretty loose. But I guess with seals, it's ok?</font>