Modifying a Hydraulic Cylinder

boustany · Sep 15, 2004

I needed a cylinder which was 12" retracted length, (pin hole to pin hole) and a 5" stroke. The one I found was 16" retracted, but the 'overage' was the extra length of the rod, and the stroke was 6". So I cut 4" of the rod, ending up with a 12" overall length and a 6" stroke. Then I shortened the stroke to 5"

The extended length was, if I recall, about 22" pre- and 17" post.

I guess the title should have been Modifying a Hydraulic Ram, but most people refer to these things as cylinders.

Yes, I did not actually cut the cylinder. I probably would have needed a lathe to do that, especailly to cut the grove for the snap ring.

Henro · Sep 15, 2004

I was surprised to see you took the cylinder apart to shorten the rod...

I bought some surplus cylinders with ends already on them, and just cut the ends off and welded on what I needed...I was careful not to overheat them. They were welded cylinders. When doing what you did I would just have cut the end off the rod and shortened the rod, and welded the end back on. I don't claim to know how to do things right though...the way you did it is probably the safest.

Was there a reason you needed to take the cylinder apart to do what you did?

Enjoyed the photo sequence.

jimgerken · Sep 15, 2004

That looks great. After hearing advice here on TRN, I did some welding to a cylinder rod without taking the unit apart. I extended the rod, wrapped the rod with wet rag to keep the heat from traveling all the way to the o ring end, and did the weld. I added a swivel ball end to make a top link of it. It has worked great for a couple years now. Your way would have been better, but this way worked fine. I coated the rod with splatter shield stuff to keep it from getting any weld stuck to it.

boustany · Sep 15, 2004

There were a few reasons I took the cylinder apart.

First, the rod is relatively light, and fully extended would only be a few inches from the end seal. I figured there was a risk I could cook the seal because the rod heated up real quick.

Second, remember I had to shorten the stroke, which meant placing the bushing on the rod, so I had to take it apart to do that anyway

Third, I wanted to make a clean, square cut, and I figured having the rod apart was the best way of doing that

Fourth, it allowed me to easily jig the thing and weld it vertically with the copper pipe to protect from splatter. I also used splatter shield but I wanted to make sure I didn't damage the rod.

Finally - I wanted to see inside! /forums/images/graemlins/smile.gif

Henro · Sep 15, 2004

Finally - I wanted to see inside! 

Me TOO! I was wondering what the inside of a cylinder looked like and thought "Thank you Boustany" when I viewed your pictures... /forums/images/graemlins/cool.gif

 Second, remember I had to shorten the stroke, which meant placing the bushing on the rod, so I had to take it apart to do that anyway 

I'm missing something here...if a bushing inside the cylinder could shorten the stroke, then there would be no need to cut the rod. And it seems like a bushing inside the cylinder would not affect the retract, since the part of the cylinder that holds the rod is original length.

What does stop the cylinder rod from retracting into the housing, if that is the right word?

I took the easy way out and ordered cylinders that had the retracted lenght that I needed as well as the stroke needed, so I don't know much, and want to learn, and that is why I am curious.

It just seems like if one would want to shorten a cylinder, he would take half off the housing, and half off the rod. I know that what you have done works, more ways than one to skin a cat, and all that... /forums/images/graemlins/cool.gif

markct · Sep 15, 2004

if you go to the link at the bottom you will see a post of how i made a hydraulic toplink from a cylinder that i had around but was about 8 inches too long, i shortened both the rod and the outer tube, didnt realy need any machining since i cut the end off and rewelded it rather than messing with the gland end, it has held up very well

homemade hyd toplink

boustany · Sep 16, 2004

Henro:

The overall assembly was too long because of the length of the rod. The cylinder itself was just right. However, a 6" stroke was too long and it would have scruntched up the deflector when fully assembled. In order to not damage anything, I needed a cylinder which was 12" retracted and 17" extended. Because the rod was 4" too long, the retracted length (i.e. piston bottomed) was about 16", and the extended length was 22"

After trimming the rod, I had 12" retracted and 18" extended. It bottoms retracted, and goes up to the point where the piston hits the top cap when extended. The bushing effectively thickens the piston from the stop, so when it extends, the rod only goes 5". The retracted length is the same because the bottom of the piston is in the same place.

I admit that buying the proper cylinder would have been the logical thing to do, and probably cheaper, too, especially considering I risked scrapping a perfectly good, new cylinder. However, I would have had to book time off work to visit a hydraulics dealer, place the order, waited a while, then took time off work to go get it, because I start work before most people leave for work, and I leave work after most stores are closed. So I bought at a retail store that has some hydraulic things.

Markct: That was good work on the mods, and cutting the bottom of the cylinder makes a lot of sense. Did you use a big pipe cutter or something? I would have had to do a lot of trial welds before I had the courage to do what you did. Your project looked fantastic!

Henro · Sep 16, 2004

I can see clearly now... /forums/images/graemlins/smile.gif /forums/images/graemlins/blush.gif

Somehow it did not register that the cylinder had excess rod that stuck out when fully retracted. It should have, the paint does tell the story...

Also like that bushing you put inside to limit the extension.

Glad you took the time to post the photos. Great work!

markct · Sep 16, 2004

( Did you use a big pipe cutter or something? )

i just cut it off in my bandsaw then ground it to a chamfer and ground out the old weld that held the endcap onto the cylinder so i could reweld it in its new position, then i drilled a hole and welded a new fitting on to connect the hose to, it worked realy good and lucky had no leaks. it sure seems to be strong, i have lifted stuff on my pallet forks the was heavy enough to lift the front of the tractor off the ground, and the tractor is a 105 hp tractor that weighs about 11,000 lbs so thats alot of strain on the toplink! i have lifted cars before with the forks and carried them around that way and luckly the welds seem to have held just fine

Junkman · Sep 16, 2004

( and finally, here is what it looks post modification with the cylinder in the 'In' (deflector up) position.)

It looks like you have added another modification to the chute. An extension to the top??? /forums/images/graemlins/confused.gif If this is correct, could you please furnish more details of how and why?.... Junk.. /forums/images/graemlins/wink.gif