Author Topic: Question about MEM Corliss  (Read 3324 times)

Offline Jasonb

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Re: Question about MEM Corliss
« Reply #15 on: December 19, 2020, 07:56:27 AM »
I'm sure you were but could not see how you got your "helpful" figures, could not even blame them being in imperial as Julius' ones were in metric ;)

Coming back to the point about restricting the flow of steam, on the MEM one the drilled passages are going to be the main restriction, as Fizzy is going to be upscaling his one there should be room to get a suitable cutter into the bore and have a slot as per the usual full size practice and the Thorp model.

Any thoughts from the wider membership?

Offline Ramon Wilson

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Re: Question about MEM Corliss
« Reply #16 on: December 19, 2020, 08:59:48 AM »
I would be reducing it to around 1.5 mm too if running on steam. The Throp Corliss has similar as you say but appears to not be enough to be able to get sufficient volume of air in in the short cut off period.

The MEM Corliss is a very nice and buildable subject but to me it has one unsatisfactory design fault. That is the main crankshaft bearing supports. I can't see any full size engine having a crankshaft and bearings sitting a top a narrow pedestal - much narrower than the actual bearing. To me this needs to be reversed to give more substance to this area and probably more so with the extra mass of the 12" diameter flywheel.

On one of the videos of this design the pedestal can clearly be seen flexing in relation to movement of the crank which to my mind reinforces that thought. Were I to build one this is one mod I feel I would need to make to what is otherwise a very nicely designed engine.

Regards - Tug
"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline Jasonb

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Re: Question about MEM Corliss
« Reply #17 on: December 19, 2020, 07:49:02 PM »
Thanks for your thoughts Ramon and also correcting my spelling :-[

I'd not looked that closely at the bearing support but having done so would tend to agree. Options would be to make something more substantial in metal with about a 2" long bottom or to sit the existing bearing block onto a solid "foundation" but I think I would go for the former and match the support for the main frame of the engine to the outrigger one.

As for your flywheel Fizzy I wonder if one could be rolled from say 50 x 6 black bar, you would be upto the welding job. Once built up into the rest of the flywheel a light skim of the outer face and edges should clean it up OK. The traction engine guys often roll two pieces about 3/4 of a circle each and then cut to give to matching halves which does away with the bits at the ends of the bar that does not roll to the same radius. If you wanted to add a bit more interest the flywheel could be made to look like a two piece one with some dummy joint flanges.

Being quite wide but thin section you could possibly modify a shepherds/hen hut wheel casting, some 12" ones on e-bay.
« Last Edit: December 19, 2020, 07:58:52 PM by Jasonb »

Offline fizzy

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Re: Question about MEM Corliss
« Reply #18 on: December 19, 2020, 09:04:36 PM »
Thanks JB. At the moment im toying with buying a 'normal' flywheel for the inner gubbins and using an outer sleeve. Recon it would need to be at least 6mm plate if rolled as inside and outside would need skimming....dont know if youve ever rolled 6mm plate but its an industrial process if done cold. Brain working as I type.....some 2" x 8mm flat bar would round a former (I have a few BIG lumps of ali for end plate formers) with the help of a large amount of OXY heat would (Might) work, do two of them as you suggest....would just need to find someone to weld them together  :whoohoo:

Offline pgp001

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Re: Question about MEM Corliss
« Reply #19 on: December 20, 2020, 12:02:47 PM »
Fizzy

I have sent you a PM regarding your search for a flywheel.

Phil

Offline fizzy

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Re: Question about MEM Corliss
« Reply #20 on: January 01, 2021, 09:25:54 PM »
The main parts excluding flywheel and supports are all completed, but i had big problems trying to get a parallel bore. Got there in the end but at the cost of oversized bore and awful finish.  Not too worried about the finish as having built a few bigger engines I have found that using graphite string (the 6mm square section stuff) works just as well as rings at low pressure and will work with a poor finish when running with wet steam. If it isnt good I will get some new honing stones, clean it up and make a new piston so not too much to lose. There is about 40 thou between the valve and the bore at its thinnest point, not something I wanted.  I will add some photos as soon as I remember to take the camera into the workshop. I had forgotten how much pleasure there is in making something for yourself instead of for a customer....and forgotten how dirty cast iron is to work with. Happy new year to one and all. Fizzy

 

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