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(DIR) Return to: Restorations
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#Post#: 40518--------------------------------------------------
Back to the Beast .... Big Sipp Problems
By: Stoker Date: April 18, 2021, 4:34 pm
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Just thought that as I'm sort of taking the day off, I'd go back
in time six weeks or so and continue the saga of problems found
on this "Bargain" half horse Sipp.
After finding that the crankshaft was not causing the bind, it
was time to disassemble the piston rod, crosshead and open up
the cylinder to find where the bind actually was coming from. As
noted before, the crank rod ends seem not the issue either, and
to further examine that linkage train, I will now note that the
crosshead slide seems to have just about the right amount of
"slop" or tolerance, to slide smoothly without binding, though
the slide shoes are shimmed with gasket material to attain a
closer tolerances for that clearance.
[attachimg=1]
Having disconnected that from the piston rod, next move was to
open up the cylinder end cap, free the piston rod packing gland
nut and back the piston out of the cylinder. While this was
easily done, as it appears there was only a sleeve in the
packing gland and no actual packing, it was noticed that there
was more than a little drag on the movement of the piston as it
was pushed back in the cylinder. So it seems that at least a
goodly part of the rotational drag noted on the flywheel/crank
assembly likely has the piston/cylinder as its source, so much
further investigation was needed here next!
Upon opening up the cylinder and removing the piston, a couple
of other telltale features were immediately noted. First, the
cylinder cover bolt hole drilled and tapped just above three
o'clock violates the steam passage port from the steam chest,
while the next one down at about five o'clock into the rim of
the cylinder, had initially been miss-located, but was caught
and corrected before it had been drilled too far, or more likely
the pre-assigned spot was missed to match with a misalignment in
the drill holes of the cylinder end cap. Whichever is the case,
something wasn't done quite right, as seen here:
[attachimg=2]
Also note in this photo, at the front end of the cylinder
(rather out of focus) the drill gouge and threading marks from
the large hole that was drilled and plugged into the front
bottom of the cylinder for no known reason.
But an interesting aspect of this is that while that hole and
plug are down at about seven o'clock in the photo, the gouge and
thread marks are up at around ten o'clock, so that brass front
face of the cylinder is an insert that is pressed of screwed
into the cast iron cylinder casting, in order to provide for the
piston rod packing gland set-up as seen here:
[attachimg=3]
Now, even at this point I'm unsure as to whether this brass
packing gland assembly "insert" is just pressed in or actually
threaded, but I suspect it is only an interference press fit,
and will test this assumption the next time I tear the engine
down. Based on the rotation of the plate on the inside of the
cylinder, as evidenced by the changed location of the drill
gouge, it could be either, but a press fit perhaps makes more
sense, we shall see.
In any event, now knowing at least much of the drag is coming
from the piston/cylinder combo, I felt it time to make do a
little measuring, testing and hopefully improving any situations
that were remedial in this area. Thus I measured the cylinder
bore for cylindrical conformity in a couple of different ways:
[attachimg=4]
[attachimg=5]
Having so measured the bore all around and in and out, I found
it to be quite consistent within a couple of thousands, and
believe that runout only to be caused by the roughness of the
bore, due to a scale or corrosion build up mostly along the
bottom 1/4 where you'd expect condensate to collect after a run.
It seems likely the cylinder was originally factory bored to be
this good compared to how much of the rest of the machining
seems to be done. To be sure the worst of the roughness was
along that bottom portion of the cylinder, but in fact all walls
of the cylinder seemed to be unnaturally dark with some form of
deposit or buildup, and thus I felt the next step to take of
benefit, would be a bit of honing of the bore. So a lashed the
engine in an end up position to the trailer hitch ball on my
trucks bumper, so as to align the cylinder vertically for ease
of working, and thus reducing any tendency of gravity to cause
uneven honing around the bore, as seen here:
[attachimg=6]
[attachimg=7]
[attachimg=8]
In the last photo you can better see (now in focus) the gouge in
the front plate of the cylinder left over from drilling the plug
hole that can barely be seen at about seven o'clock, and how it
is now rotated up to about ten o'clock. This few minutes of
honing evened the bore noticeably and smoothed it to the touch
as well. Perhaps I'll go another round of honing next time I
have it apart, but the upshot is that clearly doing this did
help materially in smoothing the engines motion.
#Post#: 40525--------------------------------------------------
Re: Back to the Beast .... Big Sipp Problems
By: Stoker Date: April 18, 2021, 6:08 pm
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Moving on to the piston now, there is lots to see and do here.
First thing I noticed here was that the piston had to be made in
at least two parts (possibly as many as four) that were screwed
together in order to capture the large cast iron piston ring.
Next thing I noticed was how incredibly rough the outside edges
of the piston face plates appeared, as seen here:
[attachimg=1]
Sadly, I was unable to get any kind of a purchase on the rims of
the piston's face plates without causing damage, in order to try
unscrewing them. Will likely make a clamping fixture to grip one
side while I chuck the other side and may be able to unscrew it
that way, the next time I have this engine apart, as there is
plenty else that needs be done here, as there is much else
wrong.
I did feel that since I was going to reassemble the engine right
away to try and run it a little at the GPU, that I should "clean
up" the rough edges around the rims of the piston's face plates
and proceeded to do so chucked up in the lathe with a collet on
the piston rod. However, as soon as I saw the amount of runout
both in circumference, as well as laterally, I knew that
something was definitely not right here, so proceeded to
indicate off of the offending surfaces and found over .007"
difference in the two face plate's circumferences and
concentricities, but even more staggering was that there was
some .040" of lateral runout. Which is to say that the faces of
the plates were wobbling wildly, the meaning of which is simply
explained by the fact that the hole, which was drilled and
tapped through the piston assembly to mount it on the piston
rod, was neither centered nor square with the surfaces of the
piston's face plates! That much lateral runout means that the
piston sits in the bore of the cylinder at an angle about 1 1/2
degrees off of a true 90 degrees. NOT GOOD!
[attachimg=2]
[attachimg=3]
As it appeared that the piston ring was still wearing quite
evenly, and no significant amount of running was expected soon,
other than a short run for the GPU, I decided to defer any
serious work on the piston problem until the next disassembly,
when I can make a tool to take the piston itself apart, to
perhaps rebore and retap and make an adapter insert, or possibly
just to build a new piston. But that's for later.
#Post#: 40529--------------------------------------------------
Re: Back to the Beast .... Big Sipp Problems
By: Jim Date: April 18, 2021, 6:50 pm
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Well you've certainly got a tiger by the tail with this engine
Daniel.
One consolation is that currently as a static model...at least
it looks good!
#Post#: 40536--------------------------------------------------
Re: Back to the Beast .... Big Sipp Problems
By: Stoker Date: April 19, 2021, 12:03 am
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Now to jump from the piston/cylinder end back down to the
flywheel/crankshaft to hopefully wrap this tale of woe up until
actual restorations get underway.
Upon opening up the crankshaft bearing caps, I was immediately
presented with a host of odd shaped and multi-layered oily
gasket and brass shims on both sides and top.
[attachimg=1]
While it all seems to work okay, I think it may be wise to try
to make a new set of shims that allow for only one in each
position, and possibly even mill the bearing blocks themselves
slightly to reduce the total thickness of shims required. But at
this point all I did was to punch stamp each of the bearing
halves, so as to assure that they would remain in proper pairs
and properly oriented.
[attachimg=2]
Next to be considered was the attachments of the crank arm and
flywheel, where a very ugly situation was discovered, in that
there is no keyway milled into the crankshaft for the attachment
of either of these features, which appear to be gripped by more
of an undersized key caming action, than by anything else.
[attachimg=3]
[attachimg=4]
So clearly when I do manage to get the flywheel and crank arm
off of the crankshaft, I will be wanting to mill a keyway into
the shaft of a size to properly accept a whole key to secure
these critical features.
And finally .... now onto the truly "Fatal Flaw", that makes
this engine essentially irredeemable ...
[attachimg=5]
To wit, three of the adjacent spokes exhibit hairline cracks
showing through the paint, which likely suggests that these
spokes are in fact cracked all the way through from some former
drop, or sideways blow to the flywheel. This is likely the
source of the flywheel wobble noted in my earlier posting, and I
can think of no practical way of making such a repair, so if any
of you out there know the whereabouts of any spare half horse
Sipp flywheels, I'd sure like to hear about it!!!
#Post#: 40539--------------------------------------------------
Re: Back to the Beast .... Big Sipp Problems
By: Scorpion2nz Date: April 19, 2021, 1:40 am
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All i can say is it looks like an interesting project .
I would build a new piston .
I would do some serious investigation of the flywheel does it
wobble from the cracks or is the bore wonky
#Post#: 40540--------------------------------------------------
Re: Back to the Beast .... Big Sipp Problems
By: classixs Date: April 19, 2021, 3:16 am
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Quite a few flaws of significant importance there.
I agree with Dennis, forget about that piston, and make it a new
one.
In fact i think i just would have made it a fast one, running a
teflonring or similar, just to see how the engine behaves with
something properly sized in there.
When the bore is properly honed, there might not even be a
reason for anything more in your case, as it would last decades
if merely intended to be a demonstrator, rather than an all day
workhorse under load.
Would be a good thing to get those bearing machined to fit a
single shim, and the flywheel will tell whether it really is
bent, or the bore crooked, as soon as you get it off there to
attend the keyway on the shaft anyway.
If it isnīt too badly bent, those 3 cracked spokes could be
brazed, and it would be back to a relatively high structural
health.
#Post#: 40566--------------------------------------------------
Re: Back to the Beast .... Big Sipp Problems
By: Gregowen Date: April 19, 2021, 9:15 pm
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This is really a fascinating account of the many things that
can be wrong with an old engine, and possible solutions, very
educational, Thanks!
#Post#: 40573--------------------------------------------------
Re: Back to the Beast .... Big Sipp Problems
By: Stoker Date: April 20, 2021, 9:10 am
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[quote author=Gregowen link=topic=4257.msg40566#msg40566
date=1618884947]
This is really a fascinating account of the many things that
can be wrong with an old engine, and possible solutions, very
educational, Thanks!
[/quote]
Thank you Sir for the kind words. Yes, very many things wrong
with this poor beast, but time will tell if I am able to
resuscitate it in any meaningful way.
Meanwhile, as I'm unsure if you've gotten the WHOLE story,
thought I'd add a couple of links here, to take you back to
earlier related threads that provide more detail and perhaps a
bit of insight.
(HTM) https://www.officeofsteamforum.com/general-discussion/12-hp-g-sipp-in-the-bag/
(HTM) https://www.officeofsteamforum.com/restorations/bargain-12-hp-g-sipp-the-good-the-bad-the-ugly/
If you haven't already seen these .... I hope you do enjoy them!
#Post#: 40593--------------------------------------------------
Re: Back to the Beast .... Big Sipp Problems
By: St Paul Steam Date: April 20, 2021, 8:27 pm
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I admire your sticktoitness re:this beast Daniel , you were
Leary of it from the Start & rightly so , this one appears it
will never be completely sound with anything less than a
complete remake but sometimes we can get it to as good as
possible with what we have to work with . carry on good Sir . &
thanks for the updates.
#Post#: 40613--------------------------------------------------
Re: Back to the Beast .... Big Sipp Problems
By: txlabman Date: April 21, 2021, 6:38 am
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Thanks for the detailed diagnosis of the issues with this engine
Daniel.
Way beyond my skills.
The flywheel cracks are the most concerning.
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