Checking Timing on LE American? - CONFUSED!!!

[DianneB]

My background is many decades working with 1:1 single-cylinder traction engines and this is my first go at a locomotive and only my second time around with two cylinders - the first time didn't turn out too well (LOL!) So I am a bit out of my league and could use some help and advice.

I picked up a LE American this spring and have been chasing around in circles trying to isolate a problem that may be timing related. The engine is 40 years old and has been through a number of hands, it has some wear but nothing that seems atrocious. The main wear seem to be in the eccentric straps, probably because they are difficult to oil, but the wear doesn't seem to effect the valve motion significantly.

The problem is that although it seems to run fairly well in reverse (going down-grade), it is VERY weak going forward (up-grade, if it moves at all) and kills the steam pressure FAST.

One D valve was tight on its stem and I corrected that - made it about the same fit as the other side.

In neutral on the Johnson bar, both valves move about the same amount and neither uncover any ports.

The maximum port openings SEEM to be about the same in forward and reverse motion but I am unsure how to check admission or cut-off points relative to crank position.

I have done a LOT of searching and have not been able to find a procedure to VERIFY the timing on a Stephenson valve gear (particularly an INCLINED valve gear!)

The nature of the problem would seem indicate a timing difference between forward and reverse gear but I need to be able to measure the timing to confirm, THEN I can try to sort out how/why the timing is out in the first place (if it is out at all).

I could put a few PSI of air pressure in each valve chest and listen for air out of the drain ports to find admission and cut-off at each end, forward and reverse but how do I measure the angle before/after each dead centre???

Thoughts? Ideas? Things to look for?

Thanks gang!

[Lovesthedrive]

Do you know how to time it diametrically?

[Lovesthedrive]

The way I was taught to time a steam engine regardless of valve gear is to use low air pressure (about 5-10 psi). You will need a pencil with a protractor.
-To work on one side at a time.
-When you start, it will be done on one side then the other side of the locomotive/engine. The locomotive will be on a test track long enough to achieve one wheel rotation.
-remove the cylinder drains on the side you are working.
-valve gear should be in full forward as that is the direction that is commonly used.
-you want to mark on the driven wheel your top dead centers.
-Starting on one of those dead centers you want to ease the locomotive forward till you hear the initial cha from the cylinder drain.
-using a fixed position on the frame, with the protractor, make a mark on the wheel. (warning! that protractor should not be able to be reset during this time!)
-rotate the wheel 180 degrees and listen for the cha.
-observe where those marks are. If the engine is correctly timed, the marks will be 180 degrees apart.
-when the marks are not timed, adjust the rod entering the steam chest to get the marks to where they are 180 degrees apart (that side is now diametrically timed). Replace the cylinder drains and repeat the process on the other side.
-when both sides are done. Steam it up and have some fun!

[David Powell]

By the seat of my pants--- Do not worry too much about exact angles of advance. You are very unlikely to get really consistent repeatable results testing a worn unknown engine. What you do need is sufficient valve opening . and in particular , plenty of advance, especially when notched up. If it were my engine I would rig up a compressor and reducing valves to give about 5lbs or so, remove the drain cocks, jack the drivers off the track, preferably but not definitely with at least the driving axlebox shimmed/wedged in about the usual running position, turn the air on, turn the wheels by hand( Mind if she is a good engine she may try to turn a bit, do not get fingers pinched) Now FORGET about how you time a single cylinder traction Set the reverser one turn or one notch from full gear. Twin cylinder locos which have lots of get up and go generally have enough advance to kick backwards just before dead centre.IF you only run air to one cylinder at a time. IF your eccentrics are set screwed and not keyed you are in luck, advance one forward eccentric until the hiss from the drain cocks begins BEFORE dead centre,I play in 3 1/2" gauge and usually the hissing begins about 1/8" of piston travel BEFORE dead centre.Larger models may take more advance, but it is a fair place to start,Once you have done one side do the same to the other. Replace draincocks, but not linkage, shut draincocks, increase air pressure till engine runs, open drains one at a time and compare results. With your previous successes you will doubtless be able to analyse and fine tune from here on. Regards David Powell.

[DianneB]

Using low air pressure and listening to the hiss from the drain cocks it looks like the timing in the American is thoroughly screwed up!

In 3rd notch reverse admission occurs at about 50% the stroke and cut-off about 75% (by pencil marks on the crosshead). Forward stroke and back stroke are about the same. In forward motion, admission occurs later and cut-off happens earlier. Left and right cylinders are about the same.

This makes no sense to me!!! Admission should start at Dead Centre (or a few degrees before) and cut-off later in the stroke (how much later depends on the setting of the Johnson bar) to make efficient use of the steam.

I don't know if the eccentrics were normally pinned on Little Engine 4-4-0's in the 1970s and I haven't rolled this one over to find out but I don't know of any other way for things to be happening so late in the stroke except by shifting the eccentrics. I also don't know what instructions Little Engines originally gave for setting the eccentrics relative to the crank pin.

HELP!!

[Lovesthedrive]

have you tried adjusting the length of the valve rod in the directions that I posted above? It is far easier than messing with the eccentrics.

[lrdg2150]

Hi
With the piston in front dead center the forward eccentric should be forward and up and connected to the top of the link. The reverse link should be forward and down and connected to the bottom.
With the piston at mid stroke or crank pin down at 90 place the johnson bar in full forward adjust the forward eccentric to where the D valve is at the end of its motion opening the front port. The same can be done with the reverse eccentric and rear port. This should get you close with making small adjustments to dial it in. Adjust the valve stem length to center the motion over the ports.
Hope this helps.
John

[DianneB]

have you tried adjusting the length of the valve rod in the directions that I posted above? It is far easier than messing with the eccentrics.

Two completely different issues, but thanks.

Thanks Irdg2150 - that makes sense.

[ken572]

DianneB,

This might or might not be helpful, see what you think.

Valve Timing

The Valve-Setters Guide A Treatise 1910
by: James Kennedy

FREE and LEGAL

Download Link:
http://archive.org/details/valvesettersguid00kenn

Edit: Here are two more also.

The Slide-valve and Its Functions 1902
http://archive.org/details/slidevalveandit01begtgoog

Modern locomotive valves and valve gears 1917
http://archive.org/details/modernlocomotiv00mcshgoog

Ken.

[DianneB]

WOW! That's a great resource Ken!!!! A cop of that goes into my files for future reference. Now to start reading

[Pontiacguy1]

Absolute easiest way to 'quick set' the timing on a steam locomotive:

(1) remove the main rod from one side of the locomotive.
(2) roll locomotive until the drive wheel on that side is on front dead center
(3) Put the valve gear in full forward
(4) loosen the eccentric that runs the valve in forward
(5) Push the piston all the way forward on that side
(6) Apply some amount of air pressure. Usually, I do this by putting a few PSI into the boiler and cracking the throttle
(7) turn the eccentric in the forward direction of the wheels until the piston just begins to move rearward. That is the point at which the port is just beginning to uncover and admit steam into the cylinder.
(8) lock this eccentric down at that point. If you want some advance, you can turn it forward just a bit more.
(9) do the reverse one
(10) put main rod back on

All of this is contingent upon the valve stroke being set before hand. In other words, pull off the steam chest top and make sure that the ports are opening and closing evenly for both sides when the locomotive is in full forward. If the port openings are occurring evenly, then this will do. If one port is opening more than the other one, ajust your rod until they open evenly. Check the reverse doing the same thing. If the ports open a different amount on the same side from reverse to forward, then the adjustment needs to be made to the rods going from the eccentric strap to the link. If they are the same in both forward and reverse, then you adjust the valve position using the valve rod.

Once you know that the forward eccentric valve position is set, then check the reverse valve position. Once they are the same for both ports in both directions, then do the procedure above. You will need to do it for both the forward eccentric and the reverse eccentric. Make sure you rotate the eccentrics in the direction of travel. Then button it back up and do the other side the same way. You might need to do a little bit of tweaking on it, but this will definitely get you close, with no protractors, blocking up of the locomotive, or anything else like that.

[ken572]

WOW! That's a great resource Ken!!!! A cop of that goes into my files for future reference. Now to start reading

Dianne,

I added two more to my post above for you.

Ken.