Jaeger (Hercules) engine compression

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J Tiers
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Jaeger (Hercules) engine compression

Post by J Tiers » Sun Sep 24, 2006 10:18 am

Got a Jaeger recently, that won't stay running. Good spark, got fuel, real good compression. Should go.

It DOES "pop", but won't keep going. The issue is that it always seems to bounce off of compression the next cycle... can't store enough energy in the flywheels to get over-center on the next compression. With compression released it spins nicely, so that isn't a problem.

It was at one point taken apart completely by the P.O., and some parts replaced. So, it is possible that this one has higher compression than it should due to faults in re-assembly, or replaced parts that are wrong.

I estimated it ought to have about 3.5 to 1, and I think (but cannot prove) that it is higher than that. I am basing that on the force required to pull it over compression, which is a LOT. I figured it should take about 60 to 80 lb max at the rim to pull over, based on the pressure, piston area, leverages and the "toggle" action of the conrod, but I think it is quite a bit higher.

Since the free friction is negligible, I don't think that is a problem, even with compression forces on the bearings.

Anyone actually measured compression in an engine like this? I'd rather not do a volumetric test, that is a heck of a mess with oil etc., although it "can" be done.

The usual compression tester assumes a fairly rapid cranking, and that just isn't happening, I have trouble turning it over fast enough to not get compression leakage via ring gaps etc.

RET
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Post by RET » Sun Sep 24, 2006 10:58 am

Hi,
I'm not that familiar with stationary engines, especially this particular one although my grandfather had one pumping water on the farm where I grew up as a boy.
If you do an internet seach of Jaeger+engine, you will get a number of sites, including one with pictures. From that I see that yours is the type that has a cam driven exhaust valve but the intake valve depends on engine vacuum to open it. Since the head comes off, wouldn't it be simple enough to make a 1/16" or 1/8" thick head gasket to try & lower the compression ratio. From what you are saying, it sounds right & this would be an easy way to check.
Since generally speaking, this whole class of engines had a low power to weight ratio, I would think that as you say the compression ratio shouldn't be very high. Its quite possible that the previous owner tried to raise it & found out that it didn't work. If the rings didn't seal well, you might also get the results you describe. You might also squirt just a little gasoline directly into the cylinder & see what that did.

Like I said, I'm not an expert on these, but it should be fairly easy to try.

Richard Trounce.

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J Tiers
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Post by J Tiers » Sun Sep 24, 2006 3:16 pm

The gas squirt was the first item of business, and it does result in pops.

Compression is good, obviously, or it would not "bounce" back off compression. Even if it were half normal, it ought to at least keep running, especially since the reduced power would also have reduced compression to overcome.

I just have not been able to dope out a decent simple compression test that is non-invasive, and still valid.

You SHOULD be able to crank up with the compression and spark arm held released, and then let it go.

When I crank as fast as I can, it still bounces back off the compression stroke. That suggests something may be amiss, but as for proving it, well, I have had no grand ideas yet.

RET
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Post by RET » Sun Sep 24, 2006 4:15 pm

As I said before, I'm not an expert when it comes to these things, but I think you should be able to troubleshoot fairly well by comparing it to the modern 4 cycle gasoline engines (lawnmowers, et.) because after all it is still a 4 cycle machine, even although it doesn't have a cam operated intake valve.
With that in mind, does it "breathe" the way it should? Is it pulling air in through the carburetor & pushing it out the exhaust? Is the exhaust valve opening when it should? Is the spark firing at the proper point in the cycle (TDC or a bit before)? Does the carburetor look right?

When it "pops," does the noise come directly out the exhaust, or does the thing try to turn first? Are you turning it the right way?

Some of these questions are quite simple & obvious and some of them may not even apply, but they might give you enough information to figure out what's wrong. From the sound of it, it could be fairly simple.

Richard Trounce.

RET
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Post by RET » Sun Sep 24, 2006 4:27 pm

Reading your reply again takes me back to your original statement. If everything else is OK, maybe as you say, for whatever reason the compression is TOO good. Where the exhaust valve closes in the cycle can affect the compresssion. If the valve doesn't close until part way down the intake stroke, you would get a smaller charge & less compression. You should get a similar effect if you choke off the intake. Just other things to try. All of this is really showing that I'm not an expert with these things, but these are the kind of things I would try if I were in your place.

Richard Trounce.

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J Tiers
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Post by J Tiers » Sun Sep 24, 2006 8:38 pm

As usual, asking generates a solution..... even if unrelated to anything discussed.

It seems to be "going" now.

All I can figure is that since it had sat unused for quite a while after the refurb it had gottten, and the cylinder oil got gummy and gave really good compression.

After a few shots of gas in the cylinder as I mentioned (did that since I didn't want to fill the tank), it started to loosen up. I think it was basically solvent action, from gas and new oil from the dripper.

Now it can be pulled over OK, and by filling a length of fuel line with gas, I got it to run for a while, governed, as it should. Governor adjustment needs work, for sure!

We'll see if the gummy stuff was washed out, or if the condition returns.

Odd, since I am used to LOW compression from stuck rings, etc, etc, but hadn't run into HIGH compression due to gum....

RET
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Post by RET » Sun Sep 24, 2006 9:27 pm

Hey,
Glad to hear you got it to go in spite of my "help"! As I said before, I don't consider myself to be an expert when it comes to these things. I'm sure I'm not an expert in many other areas too. I find things mechanical to be interesting, it doesn't matter if its locomotives, or almost anything else.

Best of luck.
Richard Trounce.

RET
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Post by RET » Mon Sep 25, 2006 3:51 pm

In thinking it over, I'm sure you're right. Tha gas diluted the old cylinder oil and that reduced the drag of the piston against the cylinder wall to the point where you could spin the engine fast enough to get past TDC. Once that happened, it took hold & began to run on its own. I'm sure when that happened, you must have had a grin from ear to ear. I know I would have. The compression won't have changed. Since it seems it went without your really having to do anything, I'm pretty sure you must have a winner. Congratulations!

What you might want to do now is to use a dial indicator with a magnetic base to check bearing clearances. On modern gas engines, the normal bearing clearance should be 1 to 1 1/2 thousandths per inch of bearing diameter. Since your engine doesn't turn that fast, you might relax that tolerance a bit, but not by much. Bearings should never be loose enough to have visible "play." You should be able to use a pry bar to move the shaft enough to see what the play is.

Have fun!

Richard Trounce.

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J Tiers
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Post by J Tiers » Mon Sep 25, 2006 8:57 pm

Heh.... this is grease lubricated, and that seems to be the stock way they were, based on all the pics I have seen. Ecept for the cylinder, that has a Lunkenheimer sight drip oiler.

So I reckon the clearances are probably larger than that! But its pretty tight.

Pics. One grease cup is missing, I'll have to get one in there, but I;ll have to braze it first, since there are some threads missing too. The other place would have one too, you'd think, but the governor weights would hit it. I think that one gets oil.

Image

Image

RET
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Post by RET » Mon Sep 25, 2006 11:34 pm

Hi,
I think I see where the missing cups are supposed to go. As I said, I don't consider myself an expert on these things by any means, but if the rest of it has grease cups, then maybe those parts are supposed to as well. I think oil would be a more likely choice for a fast moving shaft.

Where the bearings are concerned, you might try two things. First, let the engine run for a short while & see if any of the grease lubricated bearings get hot. They should get warm, but I wouldn't think they should get to the point where you can't keep your hand on them unless they are too tight. They should all wind up at roughly the same temperature by feel.

Second, try to listen to the bearings with a rod that touches the bearing at one end while you put your ear to the other (old test but works well with a screwdriver, but a screwdriver would be too short to use safely in this case). For instance, when you perform this test on a ball bearing equipped electric motor you should hear a low hissing noise if the bearing is good. In this case, the bearing should be quiet, no thumps or knocking.
The first test should tell if any of the bearings are too tight. The second should tell if they are too loose.
Again, just my thoughts for what they may be worth.
Richard Trounce.

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ronm
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Jaeger on ebay

Post by ronm » Mon Oct 02, 2006 9:17 am

JTiers, do you have your engine listed on ebay? If not, somebody has one that looks an awful lot like it...#140037395951.

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ronm
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Post by ronm » Mon Oct 02, 2006 9:30 am

Nope, sorry- skids are different....

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