Compression Change-Over Mechanism CS 3/1

[tomgilbert]

How does the Compression Change-Over Mechanism work on a CS 3/1. I have printed a cross section and read the accompanying body at www.oldengine.org/members/diesel/Technical/change.htm but am none the wiser. The plaque on the valve on the tap reads "screw in to start/unscrew when running" but I found the engine starts to run down when unscrewed.

Also, the hand priming lever was a fantastic innovation (now that I know what it is) but can someone proved a manual or information as to how to change the oil and what oil should be used in this engine?

Cheers

Tom

[Chaz]

Others may disagree, but in my opinion there is generally no need to screw the C/O valve out, but if you do, then you must screw it all the way out to the stop.
Not sure about the 3/1s, but on the 6/1 the C/O valve was done away with in the later models.
There are two ways to change the oil. One is to unscrew to plug located at the bottom of the crankcase at the same end of the engine where the C/O valve is.
The other way is to remove the access cover which has the breather attached to it ( also at the same end of the engine) and suck the oil out with a hand pump.
There has been a lot of discussion on the forum about suitable oils. I have a 1935 model 6/1 and I just use a good quality diesel oil in it (think I'm using a Shell product at the moment)

[rmchambers]

The changeover system is simple and somewhat elegant for its day.

The idea behind it is that with the changeover screwed in the cylinder is size X and with it unscrewed it is size X+Y since there's a Y sized chamber behind the changeover valve seat.

Since the moving area of the cylinder is fixed, having a larger area to compress the air results on a lower compression.  If that extra space is shut off (changeover valve screwed in all the way) then the air has less of a space to compress into and therefore has a higher compression (and since compression creates the heat for ignition - a higher heat).

Once the engine is started on high compression you are sposed to unscrew the C/O valve and lower the overall compression.  If your engine is running down when you unscrew it, I'd look for some leakage around the valve shaft which is lowering the compression to the point where it no longer sustains combustion.

I hope that was understandable.

Robert

[Stan]

Chaz...the 3/1's and 6/1's and 12/2 CS engines retained their C/O valve to the end of their run.  Right Peter??  When the 8/1 came out with it's higher rpm it did away with the changeover valve, probably for the relative ease of making the heads with fewer parts.  The Valve has a valuable function however.  It changes the compression ratio to the higher (smaller cylinder volume) ratio for easier starting.  It also allows the engine to run under heavier loads using the lower ratio to allow for less stress on internal parts.  You also have to factor in your elevation.  I am at 4000 feet and that will make a difference in where I run the C/O valve (either full IN or full OUT, no partly is allowed, kind of like there's no such thing as being partly pregnant).  Those of you nearer to sea level will use the valve accordingly.

They must be cleaned, however every 1000 hours or so, depending on the fuel you use.  I am waiting till I get Penelope together before I pull mine out for cleaning due to the "use the compression" method of getting them out.
stan

[Ironworks]

How does the Compression Change-Over Mechanism work on a CS 3/1. I have printed a cross section and read the accompanying body at www.oldengine.org/members/diesel/Technical/change.htm but am none the wiser. The plaque on the valve on the tap reads "screw in to start/unscrew when running" but I found the engine starts to run down when unscrewed.

Also, the hand priming lever was a fantastic innovation (now that I know what it is) but can someone proved a manual or information as to how to change the oil and what oil should be used in this engine?

Cheers

Tom

The reason it "runs down" as you say, could be due to lack of compression.  Give the cylinder a hone and slap some new rings in it, grind the valves and I bet it will run great with the change over unscrewed.  They are meant to be run with it out because if the compression is lower (which it is when unscrewed) then there will be less stress on the engine overall which equals longer life.....i.e.  Longevity.   I might have a manual on PDF Ill have to check.  As far as oil goes there are alot of choices.  I would use a Rottella 30w for soot control.  I just disconnect the oil line at the bottom of the sump and drain it out.  Then I spray diesel fuel all over the inside to clean the soot and wipe off as much diesel fuel as I can.  Then I give everything a good coat of WD 40 and fill er up with oil.

[Chaz]

Chaz...the 3/1's and 6/1's and 12/2 CS engines retained their C/O valve to the end of their run.  Right Peter??  When the 8/1 came out with it's higher rpm it did away with the changeover valve, probably for the relative ease of making the heads with fewer parts.  The Valve has a valuable function however.  It changes the compression ratio to the higher (smaller cylinder volume) ratio for easier starting.  It also allows the engine to run under heavier loads using the lower ratio to allow for less stress on internal parts.  You also have to factor in your elevation.  I am at 4000 feet and that will make a difference in where I run the C/O valve (either full IN or full OUT, no partly is allowed, kind of like there's no such thing as being partly pregnant).  Those of you nearer to sea level will use the valve accordingly.

They must be cleaned, however every 1000 hours or so, depending on the fuel you use.  I am waiting till I get Penelope together before I pull mine out for cleaning due to the "use the compression" method of getting them out.
stan

Hi Stan,
I've got both the original (1930-something for 3-1, 5-1 and 10-2) manual and the 1970 edition for 6-1, 8-1, 12-2 & 16-2. Seems that by then the C/O valve was an optional extra for the 6-1 and 12-2 only, but not an option for the 8-1 and 16-2.
I've never run our Mr Lister in low compression as A/. we're only 100 feet above sea level, and B/. it's only ever called upon to deliver about 3 kW max.
Consequently, I've never had the need to pull the C/O valve out and clean it.

[Stan]

OK, I've just got the original manual for Penelope, 1949 vintage and also have seen book #103/236 (not sure what year it would be).  The option without the compression changeover valve would not be a CS version then would it, or is it permanently in high compression mode.  That sure would be hard on an engine operating at more than 1/3 of load (that should be 1 kw), especially at sea level.  I'm not a diesel mechanic but that doesn't prevent me from figuring out the physics of the diesel system. There must sure be some hard knocking going on inside a machine on high compression mode.
Stan

[tomgilbert]

Okay I think I have a handle (pun intended) on the Change-over valve. As I was unsure of the consequences I was nervous to undo it all the way. I will investigate further. Thank you all.

Tom

[Chaz]

OK, I've just got the original manual for Penelope, 1949 vintage and also have seen book #103/236 (not sure what year it would be).  The option without the compression changeover valve would not be a CS version then would it, or is it permanently in high compression mode.  That sure would be hard on an engine operating at more than 1/3 of load (that should be 1 kw), especially at sea level.  I'm not a diesel mechanic but that doesn't prevent me from figuring out the physics of the diesel system. There must sure be some hard knocking going on inside a machine on high compression mode.
Stan

Hi Stan,
book 103/236 must be a pretty early edition I think. It gives Listers phone number as Dursley 177. There is a fulll list of spare parts with prices - a crankshaft was 3 pounds, 10 shillings (= $7-00!!). Probably a months wages, or more.
In book 103/171 the drawing of the head shows it with a plug in lieu of a C/O valve. In the parts list is a section headed up COMPRESSION RATIO CHANGE-OVER VALVE (OPTIONAL EXTRA) 6/1 AND 12/1ENGINES ONLY.
Also the head shown in this book has only 4 head studs instead of the 6 that the earlier models had. Obviously, this is what the Listeroids were cloned from.

[Stan]

Does the drawing with the plug show it only going in to the first chamber (which would make the head low compression) or does the plug have an extension which fills in both the outer and inner chamber (which would make it high compression)?  It would be interesting to know how they gasketed the cylinder also as that would make a big difference in compression.  Lots of gaskets on the bottom would lower the compression etc. etc..
Stan

[Chaz]

Does the drawing with the plug show it only going in to the first chamber (which would make the head low compression) or does the plug have an extension which fills in both the outer and inner chamber (which would make it high compression)?  It would be interesting to know how they gasketed the cylinder also as that would make a big difference in compression.  Lots of gaskets on the bottom would lower the compression etc. etc..
Stan

Stan - it does have an extension which takes it all the way to the main chamber.
The Parts list shows 4 X Joint (gaskets) - Crankcase to cylinder for the 6/1 and 8/1. Additionally for the 8/1 only it shows 2 X Metal shim .015"

[Stan]

OK, now it's starting to make sense, that many gaskets would indicate lowering of the compression ratio.  does it show what the "bump clearance" is between the piston at TDC and the head?  Maybe someone much more familiar with doing these calculations than I am could then figure out the compression ratio of a non-c/o valve 6/1.  Not that it matters to me but just for interest.
Stan

[Chaz]

OK, now it's starting to make sense, that many gaskets would indicate lowering of the compression ratio.  does it show what the "bump clearance" is between the piston at TDC and the head?  Maybe someone much more familiar with doing these calculations than I am could then figure out the compression ratio of a non-c/o valve 6/1.  Not that it matters to me but just for interest.
Stan

.045 to .050 for the 6/1, 12/2 and .075 to .080 for the 8/1,16/2

[Stan]

Nope, .045 - .050 is the same as in my manual.  That means they are running in high compression mode.  I wonder if they found out the engines last just as long on high compression mode as the variable comp mode engines do or maybe they just "shortened" the warrantee period. 
Stan

[Chaz]

Hmmmm - who knows? Over here on Great Barrier Island broken crankshafts on Listeroids is a common problem, but the few original Listers just keep on running.....