First, provide yourself with a "tram." This you can do by taking a 1/4
inch iron rod, about 18 inches long, and bend about two inches of one
end to a sharp angle. Then sharpen both ends to a nice sharp point.
Now, fasten securely a block of hard wood somewhere near the face of the
fly wheel, so that when the straight end of your tram is placed at a
definite point in the block the other, or hook end, will reach the crown
of fly wheel.
Be certain that the block cannot move from its place, and be careful to
place the tram at exactly the same point on the block at each time you
bring the tram into use. You are now ready to proceed to find the dead
center, and in doing this remember to turn the fly wheel always in the
same direction. Now, turn your engine over till it nears one of the
centers, but not quite to it. You will then, by the aid of a
straight-edge make a clear and distinct mark across the guides and cross
head. Now, go around to the fly wheel and place the straight end of the
tram at same point on the block, and with the hook end make a mark
across the crown or center of face of fly wheel; now turn your engine
past the center and on to the point at which the line on cross head is
exactly in line with the lines on guides. Now, place your tram in the
same place as before, and make another mark across the crown of fly
wheel. By the use of dividers find the exact center between the two
marks made on fly wheel; mark this point with a center punch. Now,
bring the fly wheel to the point at which the tram, when placed at its
proper place on block, the hook end, or point, will touch this punch
mark, and you will have one of the exact dead centers.
Now, turn the engine over till it nears the other center, and proceed
exactly as before, remembering always to place the straight end of tram
exactly in same place in block, and you will find both dead centers as
accurately as if you had all the fine tools of an engine builder.
You are now ready to proceed with the setting of your valve, and as you
have both dead centers to work from you ought to be able to do it, as
you do not have to depend on your eye to find them, and by the use of
the tram You turn your engine to exactly the same point every time you
wish to get a center.
Now remove the cap on steam chest, bring your engine to a dead center
and give your valve the necessary amount of lead on the steam end. Now,
we have already stated that we could not give you the proper amount of
lead for an engine. It is presumed that the maker of your engine knew
the amount best adapted to this engine, and you can ascertain his idea
of this by first allowing, we will say, about 1/16 of an inch. Now
bring your engine to the other center, and if the lead at the other end
is less than 1/16, then you must conclude that he intended to allow less
than 1/16, but should it show more than this, then it is evident that he
intended more than I/I16 lead; but in either case you must adjust your
valve so as to divide the space, in order to secure the same lead when
on either center. In the absence of any better tool to ascertain if the
lead is the same, make a tapering wooden wedge of soft wood, turn the
engine to a center and force the wedge in the opening made by the valve
hard enough to mark the wood; then turn to the next center, and if the
wedge enters the same distance, you are correct; if not, adjust till it
does, and when you have it set at the proper place you had best mark it
by taking a sharp cold chisel and place it so that it will cut into the
hub of eccentric and in the shaft; then hit it a smart blow with a
hammer. This should be done after you have set the set screws in
eccentric down solid on the shaft. Then, at any time should your
eccentric slip, you have only to bring it back to the chisel mark and
fasten it, and you are ready to go ahead again.
This is for a plain or single eccentric engine. A double or reversible
engine, however, is somewhat more difficult to handle in setting the
valve. Not that the valve itself is any different from a plain engine,
but from the fact that the link may confuse you, and while the link may
be in position to run the engine one way you may be endeavoring to set
the valve to run it the other way.
The proper way to proceed with this kind of an engine is to bring the
reverse lever to a position to run the engine forward, then proceed to
set your valve the same as on a plain engine. When you have it at the
proper place, tighten just enough to keep from slipping, then bring your
reverse lever to the reverse position and bring your engine to the
center. If it shows the same lead for the reverse motion you are then
ready to tighten your eccentrics securely, and they should be marked as
before.
You may imagine that you will have this to do often. Well don't be
scared about it. You may run an engine a long time, and never have to
set a valve. I have heard these windy engineers (you have seen them),
say that they had to go and set Mr. A's or Mr. B's valve, when the facts
were, if they did anything, it was simply to bring the eccentrics back
to their original position. They happened to know that most all engines
are plainly marked at the factory, and all there was to do was to bring
the eccentrics back to these marks and fasten them, and the valve was
set. The slipping of the eccentrics is about the only cause for a valve
working badly. You should therefore keep all grease and dirt away from
these marks; keep the set screws well tightened, and notice them
frequently to see that they do not slip. Should they slip a I/I6 part
of an inch, a well educated ear can detect it in the exhaust. Should
they slip a part of a turn as they will some times, the engine may stop
instantly, or it may cut a few peculiar circles for a minute or two, but
don't get excited, look to the eccentrics at once for the trouble.
Your engine may however act very queer some time, and you may find the
eccentrics in their proper place. Then you must go into the steam chest
for the trouble. The valves in different engines are fastened on valve
rod in different ways. Some are held in place by jam nuts; a nut may
have worked loose, causing lost motion on the valve. This will make
your engine work badly. Other engines hold their valve by a clamp and
pin. This pin may work out, and when it does, your engine will stop,
very quickly to.
If you thoroughly understand the working of the steam, you can readily
detect any defect in your cylinder or steam chest, by the use of your
cylinder cocks. Suppose we try them once. Turn your engine on the
forward center, now open the cocks and give the engine the steam
pressure. If the steam blows out at the forward cock we know that we
have sufficient lead. Now turn back to the back center, and give it
steam again; if it blows out the same at this cock, we can conclude that
our valve is in its proper position. Now reverse the engine and do the
same thing; if the cocks act the same, we know we are right. Suppose
the steam blows out of one cock all right, and when we bring the engine
to the other center no steam escapes from this cock, then we know that
something is wrong with the valve, and if the eccentrics are in their
proper position the trouble must be in the steam chest, and if we open
it up we will find the valve has become loosened on the rod. Again
suppose we put the engine on a center, and on giving it steam, we find
the steam blowing out at both cocks.
Now what is the trouble, for no engine in perfect shape will allow the
steam to blow out of both cocks at the same time. It is one of two
things, and it is difficult to tell. Either the cylinder rings leak and
allow the steam to blow through, or else the valve is cut on the seat,
and allows the steam to blow over. Either of these two causes is bad,
as it not only weakens your engine, but is a great waste of fuel and
water. The way to determine which of the two causes this, is to take
off the cylinder head, turn engine on forward center and open throttle
slightly. If the steam is seen to blow out of the port at open end of
cylinder, then the trouble is in the valve, but if not, you will see it
blowing through from forward end of cylinder, and the trouble is in the
cylinder rings.
What is the remedy? Well, if the "rings" are the trouble, a new set
will most likely remedy it should they be of the automatic or
self-setting pattern, but should they be of the spring or adjusting
pattern, you can take out the head and set the rings out to stop this
blowing. As most all engines now are using the self-setting rings, you
will most likely require a new set.
If the trouble is in the valve or steam chest, you had best take it off
and have the valve seat planed down, and the valve seated to it. This
is the safest and best way. Never attempt to dress a valve down, you
are most certain to make a bad job of it.
And yet I don't like the idea of advising you not to do a thing that can
be done, for I do like an engineer who does not run to the shop for
every little trouble. However, unless you have the proper tools you had
best not attempt it. The only safe way is to scrape them down, for if
your valve is cut, you will find the valve seat is cut equally as bad,
and they must both be scraped to a perfect fit. Provide yourself with a
piece of flat steel, very hard, 3x4 inches by about I/8 inch, with a
perfect straight edge. With this scrape the valve and seat to a perfect
flat surface, It will be a slower process than scraping wood with a
piece of glass, but you can do it. Never use a chisel or a file on a
valve.