[AT] hydraulics question

[Tom]

Cecil E Monson wrote:
> 
> >  Dudley
> >       I've got to take issue with a couple of your statements above.
> >       A hydraulic control valve relies on the fine clearances achieved
> >       at manufacture to perform. To hone a valve body is going to only
> >       increase internal leakage unless one is in a position to fit
> >       oversized spools. O rings are fitted to prevent low pressure
> >       external leakage as there is generally a gallery back to the return
> >       inboard of the O rings.
> >
> >       Secondly, oil supply to the cylinders is common, therefore if one
> >       leaks internally the drop in load gets shared between them.
> >       Otherwise, to maintain equality in stroke length, there have to be
> >       flow dividers in their supply circuits to ensure balanced flow to the
> >       cylinders.
> >
> >  Cecil
> >       With the problem at hand, water contamination most probably has
> >       contributed to the deterioration of the seals. If the original type
> >       seals aren't available, there are quite a few manufactures that can
> >       supply synthetic seals of more modern design that will either fit
> >       in the original locations or can be fitted with the remachining of
> >       the pistons. I've found it hard to go past Greene Tweed seals in
> >       when rebuilding & modifying cylinders.
> >
> >  Tom
> 
>         Thanks, Tom. I'll keep that in mind also.  As to Dudley's comment
> on honing and polishing, I took it to mean he polished and honed the cylinders
> and pistons, not the inside of the control valve. Read his post with that in
> mind and I think you will agree.
> 
> Cecil
> --
> The nicest thing about telling the truth is you never have to wonder
> what you said.
> 
> Cecil E Monson
> Lucille Hand-Monson
> Mountainville, New York   Just a little east of the North Pole


As I forgot to unsubscribe I'm still getting the list so can respond
to your comment.
Dudley wrote:

 "I am not a hydraulics expert but I have taken three maybe four two-way
  hydraulic valves apart in the past two or three years, cleaned them
up,
  honed the cylinder bores, polished the pistons and installed new
O-rings.
  I've installed two of these valves on two different tractors to use
for
  controlling aftermarket 3-pt hitches and when these valves are in the
  center/neutral position they will hold a load for days with no
noticeable
  compression of the hydraulic cylinders/lowering of the hitch."

I cannot construe the above as talking about nothing, other than
"hydraulic
valves", Dudley confirmed that in another post responding to my comment.

Tom