Author Topic: Unusual Corliss  (Read 3997 times)

Offline Caber

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Unusual Corliss
« on: June 27, 2021, 09:00:20 PM »
I have been thinking about building the MEM Corliss for a while. The nearest real Corliss to me is at the National Museum of Scotland. This is a reasonably locally built example, middling to small size. I was rather astonished to see that rather than the usual oscillating disk operating the valve there are instead two eccentrics with shafts directly operating the inlet and exhaust valves.







Does anyone know about this type of gear and what is the collected opinion on whether this would be simpler to make for the MEM Corliss than the designed version?

Cheers😃🏴󠁧󠁢󠁳󠁣󠁴󠁿
« Last Edit: June 27, 2021, 09:17:48 PM by Caber »

Online Jo

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Re: Unusual Corliss
« Reply #1 on: June 27, 2021, 10:11:21 PM »
American Corliss engines normally have the disc whereas British engines have the two shafts. There are various flavours of mechanisms used to get the quick cut off on full sized engines but on models you need something chunky/simple like the disc or the Throp Corliss model engine it uses Musgrave trip gear.

The Douglas and Grant Engine's valve gear could be a bit tricky to scale down and have it work. Another view of the trip mechanism:



Notice that only the inlet valves "trip".

<a href="https://www.youtube.com/watch?v=4BoDp8dSFTg" target="_blank">http://www.youtube.com/watch?v=4BoDp8dSFTg</a>

Jo
« Last Edit: June 27, 2021, 10:15:52 PM by Jo »
Enjoyment is more important than achievement.

Offline Charles Lamont

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Re: Unusual Corliss
« Reply #2 on: June 27, 2021, 10:29:48 PM »
I don't know that the oscillating plate arrangement is actually 'usual' in UK practice. The Pollitt & Wigzell engines at Markham Grange & Blists Hill have disks, but the steam and exhaust are separate, with the smaller steam disc partially hidden behind the exhaust one. I have also seen running in the flesh the the corliss valved engines at The Bratch and Mill Meece pumping stations, the Ellenroad Ring Mill engine and the 'big red engine' at The Science Museum. None of these engines has a disk, and all have independent steam and exhaust gear. There is reasonable YouTube coverage of all these engines running.

Offline Caber

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Re: Unusual Corliss
« Reply #3 on: September 30, 2023, 05:54:14 PM »
Ok I have started my Corlis build. I am not yet decided whether to use the rocking plate or the two eccentric type gear but it is going to be based on the MEM drawings. I have started with the cylinder block being carved out of a lump of Mehanite cast iron. I roughed it to size with a shell cutter and finished with a fly cutter though surface finish still not good enough. I bored the cylinder on the lathe, unfortunately gone slightly oversize as I mis allowed dimension allowing for spring in the boring bar as it is stuck out just over 2.5”

I am proposing to drill the valve ways next maybe tomorrow though I realised I don’t have a 1/4 reamer so ordering one today. Is it better doing this before the valve chests and passages?

Caber:)

Online crueby

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Re: Unusual Corliss
« Reply #4 on: September 30, 2023, 05:57:56 PM »
Great to see the build start, will be watching along. For me, I like the rocking plate version just since it adds an intriguing visual dance to the engine operation, great eye candy. But, as said, there are lots of variations over time and between countries.

 :popcorn: :popcorn:

Offline Caber

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Re: Unusual Corliss
« Reply #5 on: October 08, 2023, 11:14:09 PM »
Progress today drilling the valve bores. All the quarter inch stainless stock is seemingly just undersize so rattled in the test drilling reamed to quarter inch. My quarter inch drill however matched the stock so I drilled the holes to 7/64 then ran the quarter drill through very slowly which gives a very nice fit and finish in the bores is excellent. While on this set up I plan to drill the holes for fixing the valve caps.

Offline Caber

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Re: Unusual Corliss
« Reply #6 on: October 22, 2023, 07:02:02 PM »
This weekend’s progress was a bit hampered by the installation of a new central heating boiler! What I have achieved is drilling the fixing points for the valve bonnets , all 32 of them and carving out the exhaust valve chest both exercises in learning the circle and array functions of my new DRO.

I also paid another visit to the NMS to look at the Corliss there. I am going to see if I can adapt the MEM design to look more like this engine. One aspect will be mirroring  the design so the valve gear and flywheel will be on the other side, the next task will be to rearrange the slide bar tunnel and connection to the main crank bearing. The final and most challenging  change will be replacing the wrist plate with a second eccentric and valve rod. If anyone who has built the MEM Corliss can tell me what the rotation angle of the valve is when the engine runs that would be a great help to determine the required  eccentric throw as there is no intermediate lever in this design!

Offline Caber

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Re: Unusual Corliss
« Reply #7 on: November 04, 2023, 05:43:11 PM »
So I am some 16 hours of workshop time and have now drilled all the holes except cylinder covers into the cylinder block. Touch wood no broken drills or significant errors. The most nerve racking bit is the 20 holes for the steam ports. As these are in the curved surface of the valve guides I decided to create a flat area with a 3/32” end mill then went straight in with 1/16” drill. I used a sensitive drill attachment in a collet with an expensive sharp HSS drill which all went surprisingly well. Now a ton of tapping 6BA for the 1/8” holes and 9 BA for the 1/16” Experimenting on my scrap cast iron it seems I need to go straight in with a bottoming tap as a number 2 bottoms on the 3/16” hole without forming enough of a thread.

Offline Caber

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Re: Unusual Corliss
« Reply #8 on: November 13, 2023, 09:20:25 PM »
Another weekend on the Corliss. I made the cylinder covers and as I am looking to get more location for the cross head guide the back end cover is somewhat deeper. The intention is to bury the heads of the bolts to get full contact between the guide and cover. I used the DRO hole circle function but could not realign this after I took the cover off.

I then started work on the cross head trunk guide. This is being made from some 2” scrap steel bar that seems to be cutting quite well but needs support in my lathe.


Offline Caber

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Re: Unusual Corliss
« Reply #9 on: November 19, 2023, 03:19:14 AM »
I finished the trunk guide roughing today. Next challenge is to fit it to the cylinder block all fully aligned. After several different ideas I am planning on a couple of stout dowels and clamping them with bolts through the side of the trunk guide. I will start on this tomorrow!

Offline Dalboy

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Re: Unusual Corliss
« Reply #10 on: November 19, 2023, 08:31:16 AM »
Some great progress I enjoy watching other people produce some fine workmanship. I will be following this build keep up the good work

Online Kim

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Re: Unusual Corliss
« Reply #11 on: November 19, 2023, 04:39:25 PM »
Enjoying watching your build. Nice work on your block and trunk guide.   :popcorn: :popcorn:

Kim

Offline Caber

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Re: Unusual Corliss
« Reply #12 on: December 03, 2023, 08:17:34 PM »
I don’t know what happened to last weeks report so this covers 2 weekends work. Last weekend saw the cylinder and trunk guide united and aligned. I also made feet for the cylinder and commenced the bearing pedestals. This week has been trying to incorporate the bearing pedestal and the trunk guide extension. This has involved a number of “interesting” set ups to preserve alignment. I have tried creating splices between the bearing pedestal and trunk extension that have not worked out as expected. I think I may need to rethink some of this so gave up early this afternoon to get some headspace for fresh ideas.

Offline Caber

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Re: Unusual Corliss
« Reply #13 on: January 01, 2024, 06:16:13 PM »
Further progress has been limited however the crank bearings and supports are complete as is the crank disk. First attempt at the crank shaft failed as I was pushing myself at the end of a session and consequently mid setting the DRO and made what should have been an interference fit with the crank disk a sloppy slip fit☹️ I have been working on the set out of eccentric and valve rods. Making eccentric’s and straps is next on the list. I am trying to figure out valve travel. I think I need 90degree movement at the valve and decide on length of valve cranks.

Offline Dalboy

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Re: Unusual Corliss
« Reply #14 on: January 01, 2024, 06:29:35 PM »
Looking good I have been following what you have done so far. Keep up the good work.

I have yet to get into the workshop but then the first job sort out space for the new toys tools

Offline Caber

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Re: Unusual Corliss
« Reply #15 on: February 04, 2024, 06:22:46 PM »
So more work has been completed. Getting the engine erected on the baseplate complete with flywheel has to be some kind of a milestone and is pretty much essential to setting out the valve gear. I have made a pair of eccentrics but I am really confused by the angle required for the valve operation. I was working back from the MEM drawings and concluded I needed 90degrees of movement however having spent today looking further at video of operating engines I am coming to believe 45 degrees is nearer. If anyone who has built the MEM engine to the drawings can help me out here it would be appreciated.

The next job will be the eccentric sheaves. I happen to have some castings for the RobRoy locomotive and the eccentric dimensions are very close so these are next weekends task unless I need to remake the eccentrics with less throw!

Online crueby

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Re: Unusual Corliss
« Reply #16 on: February 04, 2024, 08:10:20 PM »
Hi Caber,


I just looked at my Mem Corliss, and the travel on the valve cranks at the end of each valve is more like 30 degrees from center at most, and the travel on the center plate each one connects to is about half that. I built mine at about half size, so the angles might be slightly different than  full size, but not much.


Chris

Offline Caber

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Re: Unusual Corliss
« Reply #17 on: February 04, 2024, 08:42:47 PM »
Chris

Thanks. That is quite a surprise I am not sure where my calculations have erred. Literally back to the drawing board!

Offline Caber

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Re: Unusual Corliss
« Reply #18 on: March 04, 2024, 08:50:49 AM »
Making the eccentrics and straps has been most challenging but so far. After the false start with incorrect throws I remade the eccentrics only to have one grab the tool and fly out of the chuck on the finishing pass destroying the flange. The strap’s weren’t any easier. I started with some castings I had for a Rob Roy . These were horrible with too much draft and a very out of centre and I discovered not round core. After spending a full day trying to get one to size I realised it wasn’t happening so ordered some 1/4” sheet brass. I then needed to do the conversion on my portable band saw to a table type. A project that had been hanging around so I could reasonably accurately rough out the shapes from the sheet. First one went OK second one not so much!  It slipped on the rotary table so I had to redo the set up. Then I broke the carbide cutter that had done the first one without complaint. Then the second cutter broke for no apparent reason. I broke the third by stupidity not lifting the cutter before moving the table which left only one to finish the job. Despite being good on dimensions I needed a lot of fitting to get the straps running nicely on the eccentrics. I think my tolerances on measurement are not good enough anyway done for now but I may remake the straps so they look better once I have sorted the valve events.

Online Kim

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Re: Unusual Corliss
« Reply #19 on: March 04, 2024, 06:20:17 PM »
Wow, Caber!  You had quite a time with those straps!   :o  Hope you have a better time with the next part you tackle.  That could get expensive going through three cutters for each part!   But they do look good in the end so you persevered.  :ThumbsUp: :popcorn:

Kim

Online crueby

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Re: Unusual Corliss
« Reply #20 on: March 04, 2024, 06:37:31 PM »
Bummer about the cutters!  One thing for future reference  in case you don't know , most sheet brass is alloy 260, sometimes  called yellow or cartridge  brass. Its a lot grabbier and pushes before cutting than the alloy 360 that most flat and round stock comes in. The 260 still works, but its tougher to cut cleanly, seams to act more like copper does.


 :popcorn:

Offline Caber

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Re: Unusual Corliss
« Reply #21 on: March 04, 2024, 08:17:47 PM »
It looks like I may have been using cutters intended for fibreglass PCB rather than metal! I got them a year ago at a show rather cheap and looking online to replace them the only ones that look similar are not meant for metalwork so maybe the wrong tool. However where can I get 3/32nd" and 1/8th" milling cutters that will work with brass phosphor bronze and steel?

Online crueby

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Re: Unusual Corliss
« Reply #22 on: March 04, 2024, 08:50:06 PM »
What country are you in, and what type of end mill holders do you have? Collet, Weldon shank? What diameters? Many choices out there!

Offline Caber

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Re: Unusual Corliss
« Reply #23 on: March 04, 2024, 09:01:47 PM »
I am in the UK I have R8 collets down to 1/8"and ER32 collets down to 2-3mm. Max speed on the mill is about 1500RPM  :)

Offline Caber

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Re: Unusual Corliss
« Reply #24 on: March 10, 2024, 07:01:41 PM »
A moderately successful day today two valve spindles complete the other two ready for the valve flats to be cut only one scrap! Sorry no photos as  I had to leave early for dinner guest!

Offline Caber

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Re: Unusual Corliss
« Reply #25 on: April 26, 2024, 11:00:57 PM »
It has been a while since I posted as I have been working on my 5” hunslet austerity in preparation for club portable track duties this summer. Today was a full day on the Corlis. I have completed a lot of the valve linkage. I was intending to make the small bits from silver steel however I somewhat bent the rod so picked up what I thought was silver steel though I think it is stainless given the grief I have had with surface finish and drilling. I am not entirely happy with the valve levers and may need to remake anyway. Tomorrow job are the link rods then it will be back to piston crosshead and connecting rod!

Offline Caber

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Re: Unusual Corliss
« Reply #26 on: April 28, 2024, 11:09:29 PM »
Another workshop day today completing valve linkages. Not much to say just a lot of quite repetitive turning and drilling operations. Putting it together showed the need to shorten the valve rods a bit to centre the valve motion.

Tomorrow will see a start on piston , piston rod, crosshead and connecting rod to complete all the moving parts😃

Offline Admiral_dk

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Re: Unusual Corliss
« Reply #27 on: April 29, 2024, 06:34:40 AM »
I see that you make progress almost daily  :ThumbsUp:

So even if it's only a bit at the time, it all add up  :)

Per      :cheers:

Offline Caber

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Re: Unusual Corliss
« Reply #28 on: April 29, 2024, 06:57:28 AM »
Ah yes! The secret is I retired at the end of March so time to access the workshop has significantly increased🤣

Offline Caber

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Re: Unusual Corliss
« Reply #29 on: May 14, 2024, 04:55:12 PM »
Significant progress yesterday and today! The Con Rod! Quite a lot to do starting with 3/4” steel square bar. Also the first significant piece since the cylinder block that I have not had to do twice! I am not saying no cock ups just that they were recoverable and the only remaining bad machining mark cannot be seen as it is buried in the trunk guide!

4 valve bonnets and crank pin to make then it is time to disassemble and paint before fitted assembly and valve timing. That will have to wait for a while as my 5” Hunslet austerity failed with non working hand pump and injector and it is wanted for club running this summer!

 

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