I need some help with this repair

[Pete O]

I got the new piston finished this afternoon. I'm glad I don't have to pay me by the hour for this stuff.

I turned the piston o.d. and then machined the lands for the seal and wear rings before taking it to the bandsaw and separating it from the big chunk of bar stock. After finishing the seal groove to correct depth and width, I spent a fair bit of time on the lathe polishing the groove with the edge of a small oilstone. I'm confident the seal should work on the groove surface.
   
You may notice the design feature I added to one of the wear ring grooves. I was using a digital caliper to work to rough depth, at one stage I zeroed the caliper and then plunged the tool to the depth I had worked out without zeroing. Very annoyed with myself but decided it wasn't worth scrapping the part for.

I whittled the old piston away until only the bit with the concave seat in it remained.
   
   
then put the new piston back in the lathe and worked on it until it was ready for the insert.
   
a smear of Loctite 620 on the insert and pressed it home.
   
   
The new piston has .004-.005 clearance in the bore, the seat is at exactly the same depth in the new piston as in the original so I'm reasonably confident it should be a fix. I chose to add two 15mm-wide wear rings so the error in the groove I'm confident will have no effect under one of the wear rings. Getting the seal over the piston and into that groove may prove something of a challenge.

Thanks again for the very helpful advice on this one.

[TomG]

Nice job Pete. You can't put a by the hour rate on the amount of satisfaction gained by such an accomplishment.

Tom

[f350ca]

Great repair Pete. Wonder if you'll notice the extra lift capacity with the bigger piston.

[Highpower]

(10-14-2017, 07:38 AM)TomG Wrote: Nice job Pete. You can't put a by the hour rate on the amount of satisfaction gained by such an accomplishment.

Tom

[Pete O]

New hydraulic pump, a completely choked-up pickup filter and everything else in the hydraulics freshened up, I sure hope there's a difference but it might be hard to tell what part the cylinder size plays. Lots of work to do on the old girl yet too.

[awemawson]

Presumably the lifting capacity is directly proportional to the piston area, so if the new piston is 5% larger then so will the lifting capacity

[Pete O]

The seal and wear rings arrived today. The wear rings are split, so fitting them to the piston is childs play. Getting the seal into that centre groove was very difficult.
   
The wear rings once fitted to the piston are a very nice sliding fit in the cylinder.

I actually started putting things back into the hydraulic chamber this afternoon. That felt good.