Author Topic: Unusual Corliss  (Read 3175 times)

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!

Offline 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

Offline 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?

Offline 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!

 

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