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©FBI 2003
This morning dawned bright and sunny; a clear blue cloudless sky and just a hint
of frost. According to the weathermen, it's just a pause between two lots of bad weather, but it couldn't have
been on a better day because today is the last show of the season. It is just an afternoon at the Victorian steam
sewage pumping station in our local town, but a good excuse to get the engines out once more. Inside the building
are four beam engines, one of which will be in steam for the afternoon, while the stationary engines are outside.
As it gets dark by around 3:30pm, people usually take lighting displays, either engine powered or oil and acetylene
lamps. A brass band sets up at the top of the engine house, between the beams, playing Christmas carols, and the
transport museum, which is housed at the site, get out their toys and drive or ride around. stationary-engine@atis.net
Before we can really turn our attention to warm, summer engine shows, there's still plenty of time for restoration
and repair projects. The discussion here began with a report a list member had given following his visit to Jeremiah
O'Brien Liberty Ship in San Francisco and an exchange about the crankshaft assembly method on the ship's engine.
* We decided that it was a built-up assembly, probably with shrink fitting
of the
journals. Yesterday, I picked up a 1930's book from my favourite second hand book store, called "Machine
Construction & Drawing", by Frank Castle. In the book are lots of drawings of mechanical items such as
line shafting and fast/loose pulleys, bearings and
engines. One item caught my eye, it was a ship's crankshaft, journal diameter was 15"
with a width across the web of 29". Not quite as big as the liberty ship but almost identical in construction,
with the journal shrunk into the webs and a dowel pin (actual rather bigger, it is 2.25" diameter) fitted
in a hole drilled exactly on the joint, thus stopping any rotation. Another, larger crankshaft is shown in the
next drawing which has journals of 26" diameter with a slightly different methods of construction.
We agreed that this was a practical method of making up a replacement shaft for an engine, but has anyone actually
used this method to produce a spare crankshaft for their engine ?
* Ronaldson-Tippett built their Austral Oil Engines with a fabricated crankshaft. It is pressed together and made
of five pieces. It is the only flaw in the construction of the engine as some engines slip and you end up with
your flywheels not lining up and a very unbalanced engine.
* How about welding a crankshaft bearing surface that is rusted and pitted? Might you have done it? I need to
fix a crank on my current project and I think I should be able to weld and have it turned. Keeping her straight
would be the trick.
* One of the instructors at our junior college told me that any time
that a crankshaft is welded, it must be straighten before grinding down the journals or mains. He uses a hydraulic
press to get the crankshaft in alignment.
* Welding a crankshaft is easily done with a submerged arc machine. However if you want to DIY, you start by grinding
the surfaces to be welded to eliminate any contaminates or hardening. Then you have a choice of wave welding or
rotary. Wave is easiest if you don't have access to a lathe or turntable (need to rotate the crank slowly to do
rotary). Then you heat the journal up and use the proper rod to build up the journal so that all of it is higher
than needed. Once your done you let it cool SLOWLY then have it straightened (if you have a couple V blocks and
a dial indicator you can do it yourself) If you have a press you can use it BUT the pros use a big hammer and a
brass drift. Once straight then you need to grind the journal to the correct size. I've done a couple and had good
results. I should start looking for a few newer machines, maybe a crank grinder and a table grinder for flywheels
and such.
* I've had a couple of ole hunks that had crankshaft trouble. Instead of having them built up and ground, on
one I had it ground true and then had a brass insert made for the brass rod journal. The other had a poured bearing
and I simply had a new bearing poured. If you have to take more than 100 thousandths taken off to smooth it up,
you may have to go the build up route as you are beginning to loose some strength in the journal.
* Years back I had a crankshaft metal sprayed. The repair brought it back to size and it machined and stayed
true. It is still working ok as far as I know. Before it was sprayed, it was really rough cut in the lathe to
give a good key. Also allowed a good depth of spray metal after machining.
* Spray metal on the crank bearing surface sure sounds intriguing. However the fellow at one of our good machine
shops said he doesn't trust it to hold. I have seen sprayed factory rebuilt water pump shafts fail in very short
hours. We blamed the lube system on the engine and even removed the engine to inspect and prove it good. Many,
many hours and expense till somebody from another dealership told us they had seen same thing and quit using the
rebuilt shafts because it didn't have good bond. I do know my crank is deeply rusted - I'm a DIY person and will
probably try to weld it.
* Metal spraying for crankshafts was used extensively in the 1940's onwards
in the UK and probably a bit earlier. It was one of the processes used by London Transport for reconditioning their
bus engines (AEC diesels) for many years without problems.
The key, if you'll excuse the pun, is to ensure a good bond between the new metal and the old surface, and to this
end it is necessary to take off the old surface before spraying on new metal.
It is still used as a process, but engine reconditioning seems to be dying out now as engines seem to last almost
the life of the car, in the UK at any rate.
As far as welding goes, I have an old Amanco crankshaft that has been welded all over the big-end surface, and
it has taken the shaft well out of true, so apart from the cost of getting the bearing ground back, the shaft will
have to be straightened again.
Hard chrome is very effective, but the matter of keying into the old surface is again a matter of concern, a bad
surface key will result in the chrome lifting off with immediate damage to the bearing material and journal.
* What about hard chrome and regrind? I have used this process with excellent results.
* I have a friend who builds models. He builds his crankshafts starting
with a full length of mainshaft, slides the webs to the correct position, fits the crank pin, and then silver solders
it all together. He then saws the main shaft just inside the webs. This method maintains perfect mainshaft alignment
for him. With large enough webs and sufficient shrink fit it would seem this method should work nicely for replacement
crankshafts.
* Although it does involve a fair bit of work, there is no reason why the technique could not be used for a replacement
crankshaft for a rare engine, or even a not so rare one come to that!
* There's a company in NC who is the official repair center for John Deere crankshafts.
They will preheat your crankshaft, submerge arc weld it in a lathe (neat automatic welding process), rough turn,
and final grind to restore your crankshaft to as new condition. A hit & miss crankshaft will be a piece of
cake for them.
In this hobby, ANYTHING is possible. It all depends on the available knowledge and resources … and, quite frequently,
that all-important resource, hard cash! Well, no-one said this obsession for preserving the engines of the past
for future generations to appreciate would be easy! And in the spirit of seeing some of those future generations
enjoying the power of the past, I'm off to put on a few more layers of clothing and head off for the pumping station!
Happy New Year to the readers of GEM from the worldwide contributors to the Stationary Engine Mailing List.
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©FBI 2003