Thoughts on Mem Corliss build on Sherline equipment

[crueby]

Hi all,

I've been drooling over the wonderful builds on the MEM Corliss design, and, wanting to build one but not sure about turning/boring/milling that big a single chunk on a Sherline lathe and mill - it is possible to make it fit but is pushing the limits of the machine. But, that has never stopped me building big stuff before...

One idea I'd like to float about the engine block construction - rather than try and make it all out of one monolithic block, I came up with the idea of splitting it into smaller chunks that would bolt back up into the larger block to get the original size again. Below is a sketch of what I am thinking.

Basically, a square core (303 stainless) with the cylinder bore, surrounded by flat slabs of 303 stainless to bulk out the areas for the valves and all the linkage mounts. That gets the size of the core block down to something I can more easily/safely set up in the lathe, plus lets me work on the complicated valve blocks seperately, which does two things - easier to fit into smaller mill, plus allows for botching a part and remaking it without trashing the entire unit.

Couple things would have to be worked out:
 - locations of the bolt holes to hold the parts together,  thinking they would have to be recessed to allow holding the combined unit in the mill vise as needed.
 - would have to combine the parts for drilling/tapping some of the linkage and end cap parts, since the holes for those would span the core and slabs.
- only place needing a pressure seal would be between the top/bottom slabs and the core, I think
- when time comes for the flywheel, that can be a built-up one, and its possible to turn the headstock on the sherline to allow truing the rim of a larger diameter wheel.

So - lets open this up for other's ideas - do you think this would work, if not why not, and any better ways to do this? I'd rather not scale the engine down to fit the machines, and getting larger equipment for the shop is not on the table (workbench?) at this point.

Chocolate mint chip cookies for the best ideas/flaws/suggestions! (maybe even for you Zee, though I probably owe you some already)

[Maryak]

There is at least one drawback I can see straight away, (apart from the problems of aligning and securing the 5 into a composite whole). The thin walls of the cylinder bore block could easily distort the bore as one approaches finished size.

Perhaps a 3 piece assembly by Incorporating the link blocks into the cylinder block.

HTH

Regards
Bob

[crueby]

There is at least one drawback I can see straight away, (apart from the problems of aligning and securing the 5 into a composite whole). The thin walls of the cylinder bore block could easily distort the bore as one approaches finished size.

Perhaps a 3 piece assembly by Incorporating the link blocks into the cylinder block.

HTH

Regards
Bob

Hmmm, good point.

[Flyboy Jim]

Chris,

Do you have any experience with Sherlines horizontal mill conversion: http://www.sherline.com/6100pg.htm
Would that be of any benefit for this project you're thinking about?

I've been looking at it for a project I have in mind.

Jim

[crueby]

Chris,

Do you have any experience with Sherlines horizontal mill conversion: http://www.sherline.com/6100pg.htm
Would that be of any benefit for this project you're thinking about?

I've been looking at it for a project I have in mind.

Jim

I had not seen that one before - could be handy for a lot of operations, not just with the headstock turned 90 like they show,  even to reach outer parts of large plates/wheels. Could be a good way to get extra reach for things like cutting large gears.

One thing with it, looks like to move the column from one place to another requires undoing two bolts underneath the x/y base into the column - does not look so easy to do and align as moving the headstock is, with its single bolt and aligning rod. Still, worth considering.... Thanks!

[Captain Jerry]

Chris

Glad to see you taking an interest in a Corliss model.  I have a couple of ideas about how the cylinder and valve blocks could be created out of 3 blocks of  something.  If you are working at the limit of machine capacity, doesn't stainless add an unnecessary degree of difficulty?  Would you consider cast iron as substitute?  I am certainly no expert with silver solder but I think that you could create a multi-part block within the capacity of your machines.  I have given thought to a multi part block for other reasons, mostly to enable the drilling of steam passages without the need to go back and fill the access holes.  I realized early on that the ability to knit the pieces together would require the ability to silver solder.

I have not drawn it up in 3D yet but I can nock something up pretty quickly if you are interested.

Jerry

[crueby]

Chris

Glad to see you taking an interest in a Corliss model.  I have a couple of ideas about how the cylinder and valve blocks could be created out of 3 blocks of  something.  If you are working at the limit of machine capacity, doesn't stainless add an unnecessary degree of difficulty?  Would you consider cast iron as substitute?  I am certainly no expert with silver solder but I think that you could create a multi-part block within the capacity of your machines.  I have given thought to a multi part block for other reasons, mostly to enable the drilling of steam passages without the need to go back and fill the access holes.  I realized early on that the ability to knit the pieces together would require the ability to silver solder.

I have not drawn it up in 3D yet but I can nock something up pretty quickly if you are interested.

Jerry

Hi Jerry,

The 303 stainless machines very easy, so I don't think it adds much strain. That alloy works much better than some of the other alloys.

As Maryak also mentioned, the wall thickness could be an issue, but I am thinking that increasing the distance between the bore and the valve a bit could solve that without hurting the performance.

[Dave Otto]

You could scale it down (Jerry Kieffer style) so that it would fit on your mill. 

http://www.craftsmanshipmuseum.com/Kieffer3.htm

Dave

[crueby]

You could scale it down (Jerry Kieffer style) so that it would fit on your mill. 

http://www.craftsmanshipmuseum.com/Kieffer3.htm

Dave

Oh my, but he does some incredible work!  While that scale would save material costs, the added psych bills and prison term from going postal would make it not worth it!

[Captain Jerry]

Chris

This is a quick and dirty assembly of 5 pieces.  Remember, all those rectangular block Corliss engines are sheet steel covers over a lot insulation. The underlying core looks more like this.

Jerry

[crueby]

Chris

This is a quick and dirty assembly of 5 pieces.  Remember, all those rectangular block Corliss engines are sheet steel covers over a lot insulation. The underlying core looks more like this.

Jerry

Jerry, Now that is a clever approach!   

You must have had a big toy chest to have had a chance to take a corliss engine block apart when you were a kid.

That opens up a whole lot of options, thanks for keeping me from sleeping tonight and thinking of this instead. That one earns some cookies!

The sides could be plated with sheet stock to give a place to mount all the valve gear, and the top/bottom plated to complete the original block look. Clever. Kudos to you, plus to the engineers 100+ years ago who thought up all these cool devices for us to model.   

For those on phones/tablets that have a hard time with animated pdf files (mine did), attached is a snapshot of what Capt. Jerry posted (hope thats okay Cap).

Oh, and I like your signature line, the similar one I used to like using on my door at work is "Those who say it cannot be done should stay out of the way of those doing it!"

[crueby]

Oh, and that approach could be assembled either with silver solder, or, a combination of high strength loctite and a few strategically placed short bolts through the end plates and partway into the cylinder core. Recently I've started using Loctite 603, which was what the manufacturer spec'ed for assembling some flex shaft cable into end fittings for some RC model propeller linkages - works quite well. That or good old Loctite Red.

[Captain Jerry]

Glad you like it, Chris.  The snapshot is a good idea.  My ideas are meant to be shared as much as possible.  I like .pdf files because if viewed with Acrobat reader, they can be rotated in 3D.

Once the block is assembled, I can see no reason that you would want to disassemble them so I would go with Red.  You would also need bosses, similar to the top valve boss for the exhaust and to mount the wrist plate pivot on the front.  If you get into it, I have a few other tricks that I would be happy to share.

I'm headed for the pantry to see what might have appeared.

[Jasonb]

Can't it be bored with a between centres boring bar then you don't need to worry about a bit lump of metal spinning round.

[crueby]

Can't it be bored with a between centres boring bar then you don't need to worry about a bit lump of metal spinning round.

I am not familiar with that method, how does it work? Can you point me at a diagram or pictures?

[Jasonb]

I use the method quite often on cylinders and bearing housings. It should also gove a more parallel bore than using a long boring bar in the toolpost as the unsuported end can deflect away from the cut









<a href="https://www.youtube.com/watch?v=AuWl-SZcC58" target="_blank">http://www.youtube.com/watch?v=AuWl-SZcC58</a>

[sco]

It should also gove a more parallel bore than using a long boring bar in the toolpost as the unsuported end can deflect away from the cut

I've seen this several times on the net but makes no sense to me - surely the force on the boring bar from the cut is the same which ever part of the bore is being cut?

Simon

[Captain Jerry]

It should also gove a more parallel bore than using a long boring bar in the toolpost as the unsuported end can deflect away from the cut

I've seen this several times on the net but makes no sense to me - surely the force on the boring bar from the cut is the same which ever part of the bore is being cut?

Simon

The deflection of the unsupported end of the boring bar is of course the same throughout the cut, as long as the hardness of the material being cut is the same.  Hard spot, more deflection, soft spot, more chatter.  Supporting both ends of the boring bar is more rigid. In addition, better ful length support of the part helps greatly, after you get it set up and dialed in.  Hitting the target for bore radius can be a PITA.

Just my thoughts. only did it once.

[crueby]

It should also gove a more parallel bore than using a long boring bar in the toolpost as the unsuported end can deflect away from the cut

I've seen this several times on the net but makes no sense to me - surely the force on the boring bar from the cut is the same which ever part of the bore is being cut?

Simon

I've had same question. As long as I finish with light cuts and even feed rates to avoid any waviness, I've always gotten very straight bores. If the part itself was deflecting from the chuck or the headstock was not square to the ways I could see the reason for a taper.

For my setup on this project I am not sure the centers method would work best, would have to get a larger hole drilled to start, and would need new tooling. Very interesting to see the different methods though!

[sssfox]

It should also gove a more parallel bore than using a long boring bar in the toolpost as the unsuported end can deflect away from the cut

I've seen this several times on the net but makes no sense to me - surely the force on the boring bar from the cut is the same which ever part of the bore is being cut?

Simon

You would use this method for the same reason that you would use a tailstock to support the end of a rod that you are turning.  As the diameter of the rod gets smaller and the length increases, the deflection increases.  At some point, a tailstock is a necessity.  The smaller the boring bar, the more deflection.  Depending on the size and depth of the hole that you are boring, there may not be a boring bar that can support itself without flexing more than an acceptable amount.

[Jasonb]

I suggested this method as it would save having to use several pieces of metal as you could easily get a single block of metal on the cross slide rather than another method of boring the cylinder for your setup. Tooling is easily made, I teh smaller dia bar I show is just a long 5/8" bolt with teh head and thread cut off, ctr drilled each end and a cross hole drilled

I see Jerry mentioned a built up cylinder, that works too provided you have enough heat to silver solder the parts or can use epoxy with fixings.





Though I still like to turn the final bore after assembly and skim the cylinder cover flange at te same setting to ensure everything is true and concentric as things can distort with the heat.

[crueby]

Thanks for some great ideas everyone, lot to think about.

Currently I am leaning towards the built-up approach like Capt. Jerry suggested, think it will fit my tools and materials best, while giving me leeway to redo parts of it if needed (which means it will all go perfect, according to Murphy, but thats okay too!). I did some drafting on it, and in order to get the fastener holes around the shaft holes and cylinder ends, plus to leave a reasonable thickness on the end of the cylinder core where the end plates go on, I am going to make one tiny change - moving the valve bores out from the cylinder just a bit, which also means the height of the block is slightly taller.

In doing more research on this type of engine, I did see some diagrams of the engine blocks without all the insulation and covers, and as Jerry said, this is about what they looked like. Mine will get plates to cover the sides/top so end result will look like the MEM plans.

Below is a sketch of where I am so far - the cylinder core piece will be 1.5" round (which is the limit of how big I can hold in the 4-jaw with the jaws normal way, which gives most surface to the jaws), stepped down at the ends to form a shoulder the end plates can seat against and also give clearance for the valve bore. The end plates are thick enough to take the bolt holes for the outer valve plates. I did not show the steam/exhaust tubes like Jerry did, but will put them in like he showed. Only functional difference from the original MEM plans is the distance from the valve bores to the cylinder is longer, but that is a fair tradeoff for keeping the cylinder core ends thick enough to be strong. The difference is small enough not to effect performance at all.

Again, thanks all for your help, build will probably start in the next couple weeks once some other projects are out of the way.