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Author Topic: Videos of slow running M90 Hit & Miss Engines  (Read 220 times)

Jim

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Videos of slow running M90 Hit & Miss Engines
« on: October 22, 2020, 05:11:54 pm »
Found these two videos of slow running M90 Hit & Miss Engines.

What's the forum brains trust think of how these two are running?

https://youtu.be/ee76fu_bENc


https://youtu.be/cqP_WDyeNd8
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Nick

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Re: Videos of slow running M90 Hit & Miss Engines
« Reply #1 on: October 22, 2020, 07:31:20 pm »
Very nice! Wish they came out of the box like that  ;)
Nick

Stoker

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Re: Videos of slow running M90 Hit & Miss Engines
« Reply #2 on: October 23, 2020, 12:34:19 am »
I've come close to the frequency shown in that second video, but the first video is a whole level of magnitude beyond what I can even conceive of at this point. It would be nice to know what all has been done to that one to get it down to that infrequent firing regimen. That is just how I'd like to get mine running someday!
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tony1951

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Re: Videos of slow running M90 Hit & Miss Engines
« Reply #3 on: October 23, 2020, 04:24:42 am »
I've come close to the frequency shown in that second video, but the first video is a whole level of magnitude beyond what I can even conceive of at this point. It would be nice to know what all has been done to that one to get it down to that infrequent firing regimen. That is just how I'd like to get mine running someday!

Same here on the way mine has run Stoker. I reckon mine had a firing pulse about once every second when I temporarily removed one of the governor springs. I also stretched it just a tiny bit as well, which helped. I know this is not good practice to have a spring on only one side, but it was just an experiment.

As for how the first engine still runs with so few ignition strokes, I think (just guessing) that the owner must have reduced the compression ratio somehow. Mine would certainly stop before TDC on a compression stroke at that speed, because the energy in the flywheel would not push it over the peak compression point. That would require some machining of the piston and a degree of daring. Would it still run after, or would you have to make a new piston? I know some skilled people have taken about 10 thou off the top and also dished the piston. I don't have the machines to do that and would not try it myself.

classixs

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Re: Videos of slow running M90 Hit & Miss Engines
« Reply #4 on: October 23, 2020, 02:43:02 pm »
I notice that both have been modded, to a single soft spring directly across the governor.
Makes the weights move very smoothly, straight, and "squeeze-free" out when rotated, compared the standard trick of simply removing one of the original two springs.
Certainly a simple mod which will be implemented here as well.
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Jim

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Re: Videos of slow running M90 Hit & Miss Engines
« Reply #5 on: October 23, 2020, 05:53:10 pm »
They are running nice aren't they and one really especially so.
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tony1951

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Re: Videos of slow running M90 Hit & Miss Engines
« Reply #6 on: October 24, 2020, 03:54:35 am »
I notice that both have been modded, to a single soft spring directly across the governor.
Makes the weights move very smoothly, straight, and "squeeze-free" out when rotated, compared the standard trick of simply removing one of the original two springs.
Certainly a simple mod which will be implemented here as well.
That is certainly true, Classixs, but I still think it is more than the spring tension that allows one of those above  to run so very slowly with long periods of idling and the very occasional pulse. There is no way at all that my machine would run that long without stopping, simply because it has far too much compression in comparison to the flywheel energy at low speed, to allow it to do so. I have played about with spring tension and when the firing rate falls below about once a second, the engine just stalls with a bump at around TDC as the compression overcomes the flywheel energy.

I feel sure the piston has been altered.

classixs

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Re: Videos of slow running M90 Hit & Miss Engines
« Reply #7 on: October 24, 2020, 04:45:25 am »
I agree with you completely Tony.
Just wanted to point out, that the centered spring solution here, is way better engineering, than just removing one of the original springs.
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tony1951

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Re: Videos of slow running M90 Hit & Miss Engines
« Reply #8 on: October 24, 2020, 11:11:13 am »

Just wanted to point out, that the centered spring solution here, is way better engineering, than just removing one of the original springs.

Definitely that's right.  ;D

I might buy a selection of springs to try the impact of different ones. Sad to say, I lack both the equipment and the engineering skill to modify the piston, though I might try a thicker head gasket to make more space above the piston. As far as I can see, the only other variable that would affect is the exhaust push rod and there is a bit of latitude there to adjust that easily. The limiting factor is probably that just adding a ten or twenty thou head gasket would not make much difference to a 7cc engine.

Adirondack Jack

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Re: Videos of slow running M90 Hit & Miss Engines
« Reply #9 on: October 28, 2020, 06:49:44 pm »
Reduced compression by shaving the piston is one guess. Another is carefully going through the Governor mechanism and polishing everything to operate smoothly. The last guess is timing very carefully retarded so it fairly jumps to life just a skinny hair AFTER TDC. It’d be nice for display, but under any kind of load might not be happy.

odu50

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Re: Videos of slow running M90 Hit & Miss Engines
« Reply #10 on: November 04, 2020, 03:17:50 pm »
Beautiful operation

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Belugawhaleman

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Re: Videos of slow running M90 Hit & Miss Engines
« Reply #11 on: November 05, 2020, 04:35:34 pm »
Nice and slow.
   I recently changed the springs on my engine with some softer ones. Although slightly
Larger in diameter than the originals I think they look better. However, I haven't been
Able to get my engine to fire much lower than once every second. But that's an improvement over its original rate. I really don't want to tamper any more with my engine,
but the single centrally mounted spring seems a good idea.
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