Tilt cylinder pressure

[reno611]

What is the rated pressure for the tilt cylinder on a 643 Bobcat? Thanks....

 

[Tazza]

The 643 series run 1,900 PSI so it would be rated at at least that pressure. I would suspect there would be at least a 50% safety margin on top of that (don't quote me). I hope this was the information you needed.

 

[1fatcat]

The 643 series run 1,900 PSI so it would be rated at at least that pressure. I would suspect there would be at least a 50% safety margin on top of that (don't quote me). I hope this was the information you needed.

Did you bend a rod? Just curious.

 

[reno611]

Did you bend a rod? Just curious.

A belated thanks for the information. My computer took a powder for a long time. Anyway, no I did not bend the rod, I just am having a time with it leaking and dropping down with or without a load. I had it rebuilt once, the cost was HIGH..it lasted about 15 minutes, so I have been living with it and have gotten pretty good at keeping it from tilting slowly downward by playing with the petal, but it is a pain...The old cylinder wall was scored pretty bad and metal had gotten into the tank, so I cleaned it as best I could with a magnet, fished out small slivers of metal. I continue to monitor the magnet (perniment in tank) and now fish out a very small amount of minute particals almost like graphic..Again my thought was buying an after market cylinder, same size piston rod, stroke and pressure rating and change out the old one..would be a hell of a lot cheaper that having this one rebuilt again. What are the thoughts....

 

[Tazza]

A belated thanks for the information. My computer took a powder for a long time. Anyway, no I did not bend the rod, I just am having a time with it leaking and dropping down with or without a load. I had it rebuilt once, the cost was HIGH..it lasted about 15 minutes, so I have been living with it and have gotten pretty good at keeping it from tilting slowly downward by playing with the petal, but it is a pain...The old cylinder wall was scored pretty bad and metal had gotten into the tank, so I cleaned it as best I could with a magnet, fished out small slivers of metal. I continue to monitor the magnet (perniment in tank) and now fish out a very small amount of minute particals almost like graphic..Again my thought was buying an after market cylinder, same size piston rod, stroke and pressure rating and change out the old one..would be a hell of a lot cheaper that having this one rebuilt again. What are the thoughts....

uum.... there is no reason for you getting small pieces of metal from a cylinder.....

Even if the cylinder walls are scored, the piston should not make contact with it. I would be a little worried about where these metal pieces are coming from. Now, you mention you can get it to not move by adjusting the pedal. Does this also work when the machine is turned off? give it a go, shut the machine off and tilt the pedal back and see if it slows the drop if the bucket. If it does, it will either be your load check seals in your spool valve or a broken centering spring in the spool valve. I replaced my seals on my load checks on my 731 (some where shredded), the lift arms used to just fall on their own even after i replaced the ram seals, but i could stop it moving my tilting back on the pedal.

Also, this ram, did they fully re-build it and not just replace the seals? as you did say it was scored did they hone it out or replace the outside of the cylinder. If not, that is probably why it worked to start with then went back to how it was. It would have just killed the piston seals if they didn't and you would be back to square one.

 

[goodtech]

uum.... there is no reason for you getting small pieces of metal from a cylinder.....

Even if the cylinder walls are scored, the piston should not make contact with it. I would be a little worried about where these metal pieces are coming from. Now, you mention you can get it to not move by adjusting the pedal. Does this also work when the machine is turned off? give it a go, shut the machine off and tilt the pedal back and see if it slows the drop if the bucket. If it does, it will either be your load check seals in your spool valve or a broken centering spring in the spool valve. I replaced my seals on my load checks on my 731 (some where shredded), the lift arms used to just fall on their own even after i replaced the ram seals, but i could stop it moving my tilting back on the pedal.

Also, this ram, did they fully re-build it and not just replace the seals? as you did say it was scored did they hone it out or replace the outside of the cylinder. If not, that is probably why it worked to start with then went back to how it was. It would have just killed the piston seals if they didn't and you would be back to square one.

Have you changed your hydraulic filter on this unit, it may be plugged and going though bypass mode right now, and that can cause hydraulic problems also

 

[reno611]

Have you changed your hydraulic filter on this unit, it may be plugged and going though bypass mode right now, and that can cause hydraulic problems also

I have changed the filter twice since owning the machine. The tilt cylinder wall was scored bad, the piston was scored as well on one side. The mechanic said it was the worst he had ever seen, naturally it was mine. Anyway, he took it away and a new cylinder was built and everything inside replaced...nice big write off. When I mentioned working the tilt pedal, that is what I do, keep a little pressure on the heel and try to keep it tilted up or level..I move honey bees on pallets, four hives each..at night, no light, except to flick on bright red lights for an occasional look see. Bees do not fly at night, but they crawl and will fly to light. Sometimes it is hard to keep one's mind on tilt cylinder attitude while being covered with bees and ending up stabbing the forks into the ground and dumping a pallet of bee hives. It ain't pretty.
Today I will try the test with the machine and see if it might be the spool valve. The repair of these valves sounds involved so I might be better off calling the mechanic back and brace up...thanks, wbl.

 

[reno611]

I have changed the filter twice since owning the machine. The tilt cylinder wall was scored bad, the piston was scored as well on one side. The mechanic said it was the worst he had ever seen, naturally it was mine. Anyway, he took it away and a new cylinder was built and everything inside replaced...nice big write off. When I mentioned working the tilt pedal, that is what I do, keep a little pressure on the heel and try to keep it tilted up or level..I move honey bees on pallets, four hives each..at night, no light, except to flick on bright red lights for an occasional look see. Bees do not fly at night, but they crawl and will fly to light. Sometimes it is hard to keep one's mind on tilt cylinder attitude while being covered with bees and ending up stabbing the forks into the ground and dumping a pallet of bee hives. It ain't pretty.
Today I will try the test with the machine and see if it might be the spool valve. The repair of these valves sounds involved so I might be better off calling the mechanic back and brace up...thanks, wbl.

Just had the tilt cylinder rebuilt for the second time. It still falls down, loaded or not, but not as fast as after the last rebuild. So now what do you think might be the problem. Someone mentions previously that the spool valve might need rebuilding..Where is it and what does it look like? I did the test with no results. Thanks..

 

[Tazza]

Just had the tilt cylinder rebuilt for the second time. It still falls down, loaded or not, but not as fast as after the last rebuild. So now what do you think might be the problem. Someone mentions previously that the spool valve might need rebuilding..Where is it and what does it look like? I did the test with no results. Thanks..

What model bobcat do you have?
It should be located on the left hand side when you stand at the front looking in over the bucket. Lift the rops and it should be rite there down on the left. If its a gresson brand spool it has a heap of O rings that should be replaced that are located in the load checks. Each load check has 3 O rings, 2 load checks per spool block. Then there are 3 or 4 O rings between each spool block that you will need to replace if you have any leaks between sections. But if there are no leaks just leave them alone. The easiest way to replace the load check O rings is to remove the spool but its not a nice job!.
You could change them on the machine but it will be difficult. Let me know the model and that may help in giving you more information.