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. . . the Great Babbitt Debate

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By Staff

Gas Engine Magazine is, of course, required reading for anyone
involved in the stationary engine hobby, so it’s no surprise
the magazine gets discussed on the Stationary Engine Mailing List.
The recent two-part article by Craig Prucha in the March and April
2004 issues about his extreme restoration generated a great deal of
interest, as the following discussion shows.

What do you all think about Craig’s method of drilling,
tapping and using brass screws to align the crankshaft and get the
proper standoff, and then pouring the babbitt? As a relative
newcomer to the hobby this sounded good to me. For those who
didn’t read the article, he left the brass screws in place
after the pour.

It’s the same method a man who worked in the elevator
business taught me. He poured many bearings using this method, and
the best advice he gave me when I started to pour bearings was,
‘What have you got to loose? If it doesn’t pour right, melt
it out and pour again!’

I think this method would make it harder to use a bearing
scraper later on. But, I guess that’s a problem for the next
owner, and not a problem you’ll face.

Two weeks ago, I poured babbitt on a trip hammer crankshaft
(first time doing this). To set my distance, I took an old leather
belt and cut two pieces, one for each main, with the leather
lengthwise (1/4-inch wide by 3/4-inch long) resting on the bottom
of the main, and sat the shaft in place (the shaft held the leather
down).

After I had smoked it up, I made a dam on both sides of each
main, heated the main casting while keeping the babbitt hot, then
poured babbitt one at a time. The leather’s still in place and
will hold some of the oil. If I ever need to redo the babbitt, it
comes out easy.

A discussion doesn’t go very far unless there’s some
disagreement. We at the Stationary Engine List are proud of our
longstanding ability to disagree. In this case, the lone voice of
dissent was from an Australian contributor.

The brass screws will rip the crankshaft journals to shreds.
Brass is definitely harder than babbitt and will react/respond/
perform quite differently to the lubricant. The leather strip
method sounds reasonable if you don’t want an adjustable
frame-type setup.

I trust Craig’s knowledge and workmanship 100 percent. The
bearings on my 15 HP IHC are brass and have done no damage to the
crank during the past 90 years. Additionally, most rod bearings on
oil field engines produced in the U.S. (90-100 years ago) were
brass ‘blocks’ that have been machined to fit the crank,
thus the name ‘brasses.’

That’s what was on the Tillinghast half-breed oil field
featured in the December 2001 GEM. (John Fankhauser modified a set
of brasses to fit it.) One hundred-plus years of wear and no
perceptible damage to Tillie’s crank! I also have a 2 HP Jaeger
that used brass pins (perhaps 1/4-inch) to insure the bearings
didn’t spin -again, no damage to the crank.

I would disagree with your thoughts on this. While brass is
considerably harder than babbitt, you must take into account the
bearing surface area.

You might have only 1/16 of a square-inch (or less) per brass
screw of surface area touching the crankshaft (if the screw head
totaled 1/4-inch). You would possibly have 24 square inches (for
say a 2-1/2-inch crankshaft with a 6-inch-wide journal) of babbitt
material touching the same crankshaft. The wear differential would
be so minute that I think you wouldn’t see any significant wear
at the screw area.

Leather sounds okay and would work fine for our old hunks of
iron. But, if you have a piece (or pieces) of leather 1-inch-wide
and say 2 inches total in length to support the crankshaft, on the
scenario I mention above, you’re going to lose close to 10
percent of your bearing surface area.

For these old, slow-running engines, I don’t think it
matters either way.

That’s kind of what I was thinking. But, if you
drilled/twisted the screw head off and left the shank, you would be
certain that the babbitt wouldn’t ‘spin.’

Small vernier adjustments could be made prior to pouring to
assure good alignment, proper babbitt thickness, etc.

The bearings in my 2 HP Chapman are indeed brass or similar
metal, but they’re a split bushing, not babbitt. There was very
little crankshaft wear, but the bearings themselves were worn quite
a bit. I simply slid shimstock around the bearings when I put them
back in, compressing them a bit and tightening this up.

I wonder if the ‘brasses’ might actually have been
bronze. I’ve been told that bronze makes a much better bearing
than brass. How does one tell the difference?

I don’t have a clue. I keep the two separate by buying brass
and bronze and marking them as such.

The brass and bronze I buy machine differently -I can tell that
much. But, there’s a wide variety of alloy compositions in
both. It’s hard to generalize about characteristics of the
two.

I suspect most of the ‘brass’ bearings are in fact
bronze. It’s the proportion of zinc to copper to tin that makes
all of the difference.

Anyway, I quite agree that bronze (or brass) makes a great
bearing surface. My comments regarding brass screws came from
observing a crankshaft that had been very badly scored by the brass
dowel pins that located the brass-backed babbitt-lined shells. My
memory fails to recall the make, but I believe it was an American
six-cylinder gasoline engine of about the 1930s, and it was out of
a dragline or small shovel. The brass dowels had a step in their
diameter, with the larger diameter located in the main bearing
tunnel in the crankcase, and the smaller diameter located in the
bearing shell. This was used instead of the more common tang
device.

On two of the main bearings, the dowels had worked through the
brass shell and scored the crank. Needless to say, the brass shells
also had worked their way into the tunnel to the point where the
tunnel needed to be line-bored to true it up.

A new set of brass shells were made with oversized diameters to
suit the new tunnel diameter. These shells were then babbitted and
bored to match the rebuilt crankshaft. New brass dowels were used,
but this time they were threaded into the bearing tunnels, with
their tops well below flush with the bearing surfaces in the fitted
shells.

The use of brass screws to locate the crank is a good fix, but I
wouldn’t if the engine were going to be put to serious use.

As is usually the case with old engines, there are no
hard-and-fast rules. Manufacturers constantly ‘borrowed’
ideas from each other and developed new ideas of their own – much
like car designers today. Through discussions such as this, we can
learn ways of keeping old engines running for future
generations.

On a side note, over the past week there has been some
readjustment of the balance of iron from one side of the Atlantic
to another. The Baker Monitor and pump jack my husband gave me at
Portland finally arrived in England, along with a Maytag twin and a
small R&V purchased at the big R&V show in September. In
return, a small two-stroke lawn mower engine headed west.
Hopefully, you’ll be able to read about these engines in future
editions of GEM.

Engine enthusiast Helen French lives in Leicester, England.
Contact her via e-mail at: Helen@insulate.co.uk You can join the
Stationary Engine List on the Internet at: www.atis.net

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