> ...
> It's known that high pressure oil seals work if done right, so I'd bin
> that with the minor issues that can be solved later by throwing enough
> money at them, ...

I'd wish - but lots of slightly different sizes - and you are going to
be able to find a seal for each diameter?

Maybe one could get a list of stock seal diameters, and find that yes,
the pressure and therefore test force you'd end up with would be just
fine - sits just where it needs to be to plot the S-N curve for
fatigue performance. Throwing aside minor vanities like getting the
stress which should mean the mean-average sample break is at exactly
250k cycles, etc.

Rich S

"Jim Wilkins" <muratlanne@gmail.com> writes:

> ...
>
> [[[[[[[[[[[[[[[[[
> It's difficult to create innovative mechanical solutions with only
> stock parts meant to solve standard problems. At Segway which was an
> engineer's playground by official policy the CNC lathe and milling
> machine were almost always tied up making someone's wild idea. I used
> their manual lathe or my home shop machines but my main task was
> custom electronics.
>
> https://news.yale.edu/2008/12/05/students-learn-how-kiss-frogs-and-take-risks-morrell-s-class
> Electric model airplanes were practically a second product there, and
> they taught me the care and feeding of Lithium batteries.
> Unfortunately like bridge building the team dissolved and sought new
> challenges once the project was complete.
> ]]]]]]]]]]]]]]]]]
>
> Maybe the "hydraulic fluid" could be grease - thick - tranmitting to
> oil or water through a rubber membrane. So the piston/bush sees
> viscous grease not thin oil.
>
> [[[[[[[[[[[[
> It's known that high pressure oil seals work if done right, so I'd bin
> that with the minor issues that can be solved later by throwing enough
> money at them, and concentrate on identifying and resolving the
> show-stoppers.
>
> I'm glad I read the Amazon reviews before applying the thick black
> tire bead sealer goop. A reviewer advised to let it set somewhat
> before inflating the tire lest it spray out. I did, and only soapy
> water rubber lube sprayed me before the bead seated when I inflated
> it.
>
> Here is a racing engineer and technology historian who might know
> about metal fatigue in oil:
> https://www.calum-douglas.com/

Off-topic but...

Two
great leads in there!

Engine Development and how done.
Empires were at stake then and technical folk got resources - amazing
what they did.

The Calum Douglas lead - never met or seen a pic. of the brittle lacquer
method for stress distribution in-action. ****! it's effective!
The "perspex / polarised-light" method - I wanted to use that when I
knew a Finite Element Analysis modelling engineer must be talking
<...nonsense!...>, before I could FEA. I actually blagged some
"perspex" from a nearby company - but the Finite Element Analysis
engineer then made such a bad political slip-up that we lost the job
it was for anyway.

"Yale" / Segway lead...
The one about engineers "kissing a lot of frogs to find a
prince". Exactly! Yes, that's the reality of a scientist too!
You have to be able to think and process things that way, to be a
human having an effective channel of perception into the Natural
World.
I almost envy people living in what they think is a determinate world.

"Richard Smith" wrote in message news:lyzgwjnpx2.fsf@richards-air-2.home...

> ...
> It's known that high pressure oil seals work if done right, so I'd bin
> that with the minor issues that can be solved later by throwing enough
> money at them, ...

I'd wish - but lots of slightly different sizes - and you are going to
be able to find a seal for each diameter?

Maybe one could get a list of stock seal diameters, and find that yes,
the pressure and therefore test force you'd end up with would be just
fine - sits just where it needs to be to plot the S-N curve for
fatigue performance. Throwing aside minor vanities like getting the
stress which should mean the mean-average sample break is at exactly
250k cycles, etc.

Rich S

-----------------------

This is a US company selling inch-sized products, but it shows what to look
for.
https://www.baileyhydraulics.com/Product-Type/Hydraulic-Cylinder-Components-

When I needed new seals for leaky used Porta-Power-type cylinders I went to
a pump rebuilder who found seals that were close enough in the catalog of a
supplier I don't remember. My cheaply made Chinese cylinders were somewhat
non-standard so I had to machine the pistons a bit. I've been told they are
typical of import hydraulics that can't be repaired (without remachining).

The cylinders were $10 and $15 each and the right very compact size for my
bucket loader design so they were worth the trouble.

I suspect that seals are available for all cataloged sizes of chromed and
polished hydraulic rod stock, a part I can't make. Then you only need to
make (or buy) the packing gland that adapts the seal to the cylinder end
cap, and a crosshead to keep the piston running straight, both fairly easy
on a thread-cutting lathe. They could be combined into one part. Instead of
machining a hex you can drill two holes for a pin spanner wrench to tighten
it.

Last night the air cleaner cover latch on the Chinese engine of my sawmill
broke off so I made a stainless sheet metal replacement. I've stopped
hunting for spare parts that are difficult or impossible to find and no
better than the originals.

A -good- lathe is an investment that may appreciate. Collectors restore the
better examples of mine, like classic cars.
https://www.tinshackrestoration.com/2015/01/19/south-bend-heavy-10-lathe-2/
"Too funny! You bought a great lathe, and with all of those vintage Rovers
you better learn to make parts quick! Thanks for the note!"

"Richard Smith" wrote in message news:lyv977nm6b.fsf@richards-air-2.home...

"Yale" / Segway lead...
The one about engineers "kissing a lot of frogs to find a
prince". Exactly! Yes, that's the reality of a scientist too!
You have to be able to think and process things that way, to be a
human having an effective channel of perception into the Natural
World.
I almost envy people living in what they think is a determinate world.

---------------------

I have a BS in Chemistry so I understand how a scientist must think and
operate. It's a very hands-on discipline that applies to almost any industry
and we received a broader training than I've seen in other types of engineer
and scientist, such as Materials Science (the properties of steel) and two
years of Physics.

The profs told us a BS degree doesn't prepares us to do useful work
immediately, only to understand the explanations wherever we go. Advanced
degrees were essential, they said self-servingly. (Mitre was like that too.)
I was chosen for summer research grants and did learn more about real life
applications, and what it's like to hole up in the lab all night and not see
other humans for weeks at a time. I was disturbingly comfortable with that.

At graduation time I still needed 4 more credits in any subject and, being
somewhat burned out by then, signed up for 6 credit, certain-to-pass summer
theatre as a carpenter, and was packed in with as many touchy and demanding
humans as I could stand for 12-16 hours a day, good training I suppose. I
was dancing on stage when Armstrong landed on the moon.

When I graduated the grad school draft deferment had ended, taking with it
my Chemistry career, but the Army was glad to find someone they could train
to maintain complex electronics along the lines of your Colossus machine.
The few who survived that school all had technical degrees. The integrated
circuit was enabling electronics' Great Leap Forward and I got in it at the
start.