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.

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.

stationary-engine@atis.net

Site Index

Back

Articles Index

Next

Email










©FBI 2003