Author Topic: Mem Corliss question  (Read 292 times)

Offline Woodguy

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Mem Corliss question
« on: June 07, 2019, 05:53:08 PM »
With the crank at top dead centre, what is the correct angular orientation of the eccentric?

Offline crueby

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Re: Mem Corliss question
« Reply #1 on: June 07, 2019, 06:05:36 PM »
Should be 90 degrees from the crank pin. On mine, I made the eccentric point towards the cylinder when the crank was at the top - if you went the other direction it would run the engine in the opposite direction.

Offline Jasonb

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Re: Mem Corliss question
« Reply #2 on: June 07, 2019, 08:38:09 PM »
I tend to set my engines up with some lead for smoother running so the eccentric should be ahead of the crank by 90deg plus the lead, say 20deg if air running 30 deg if steam powered.

This is similar to what Stuarts suggest for their engines

https://web.archive.org/web/20060713173202/http://www.stuartmodels.com/pdfs/SM-Timing.pdf

Offline kvom

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Re: Mem Corliss question
« Reply #3 on: June 08, 2019, 12:27:56 AM »
The actual Corliss in Rhode Island has the top of the flywheel turning away from the cylinder.

Offline crueby

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Re: Mem Corliss question
« Reply #4 on: June 08, 2019, 12:52:02 AM »
Just checked my videos of the compound Corliss at the Owls Head museum in Maine, it has the top of the flywheel turning towards the cylinder, not away. With this type of engine with a full crosshead guide, it may not matter as much?

Offline Woodguy

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Re: Mem Corliss question
« Reply #5 on: June 08, 2019, 12:54:03 AM »
Thanks for that.

Offline kvom

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Re: Mem Corliss question
« Reply #6 on: June 08, 2019, 01:09:14 AM »
I suppose much depends on the mill machinery being driven.

Offline MJM460

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Re: Mem Corliss question
« Reply #7 on: June 08, 2019, 10:34:26 AM »
It is worth going back to first principles and remembering what valve events are required to produce an ideal indicator diagram.

Normally with crank at either dead centre, the inlet valve should be just on the point of opening as the crank turns in the required direction.  With a conventional slide valve, that is all that is required, as all other valve events follow from the valve dimensions and port layout if the engine has been designed correctly and made accurately.  If you canít remove a cover to see when the port opens, you could jury rig a plastic tube to the steam inlet and blow into it to see when the valve opens.

However on that Corless there are several little links that all have to be the correct length, so you may need to check the valve openings and closings a bit further.  I donít know if they are adjustable or just have to be the design length.  You may have to check the inlet for each side of the piston, and even check that the exhaust opens at the right place, usually just before the end of the inlet and expansion stroke.

I assume that if the valve opens at the correct point, the valve dimensions and motion plates determine the closing if the links are all the correct length.

Perhaps someone with more knowledge of the Corless valve gear could help us all understand a bit more of just how it ensures each valve event in the cycle.

MJM460

The more I learn, the more I find that I still have to learn!

Online Jim Nic

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Re: Mem Corliss question
« Reply #8 on: June 08, 2019, 12:32:07 PM »
On my version I made the valve operating links to be adjustable on the valves by using a clamping arrangement rather than the design method of pinning or Loctite.  Having set the basic timing by positioning the eccentric I was able to adjust the individual valves for best running.

Jim



The person who never made a mistake never made anything.