Arnold's take on the MEM Corliss

[steamer]

All that needs is some elbow grease...it's fine Arnold!...Keep going!

 

Dave

[vcutajar]

Thanks Arnold for showing how to make a square hole (is this correct English?).

Just a thought.  If you decide to remake the valve disk how about making the middle portion around the square hole a little wider so that a 3mm nut and washer won't look too big.

Vince

[Maryak]

Arnold,

Nice work, I thought there was more than enough room for the nut and washer. Is it me or is that area narrower than the original 0.5", 12mm?

Best Regards
Bob

[b.lindsey]

Arnold, i don't see any laziness in your post at all...just some good efficient planning which we can all learn from....nice work as always.

Bill

[larry1]

Arnold,  Great work and thank you for posting the pictures.     larry

[arnoldb]

Dave, Vince, Bob, Bill & Larry - thanks for checking in Gents 

Vince, I think it's perfectly good to say it's a square hole  .  There are other ways to make square holes - and a bit neater than I did, but for those one needs additional tooling - things like broaches or EDM machines and so on.  I don't have broaches, and they're a bit expensive, no EDM, and while I could have made up a broach from silver steel, it would have taken me much longer to do, so this just seemed the easiest solution here.  Another option was to run through the hole to square it up with a 1mm end mill - the ones I have can reach 5mm deep - and then just round over the corners on the pivot pin a bit to fit.  That might be a neater solution, but milling with such a small end mill can take ages...  So I opted for the much quicker file&go option.

It's possible to "cheat" a bit with the valve disk and spindle for anybody not interested in messing around with square holes and such...  The main reason for the square is to allow one to tighten the nut on the spindle with the spindle and hub already mounted on the cylinder block.  Instead of making the squares, just turn the square section on the spindle down to 3mm, make a slot at the big end for a flat screwdriver and leave the hole in the disk round at 3mm.  Then it's easy to assemble the hub, spindle and disk together before mounting the hub on the cylinder block.  The downside to this deviation from plans is that the disk arms mount to the back of the disk, so these would be fiddly to install later - or if installed to the disk before mounting the assembly on the cylinder block be prone to get in the way while mounting the assembly.  As so often happens building engines, it's a bit of swings and roundabouts - and one must choose where one would like to do the fiddly bits 

  Bob you're right...  I made that middle section only 6mm wide instead of 12mm  - entirely my fault.

But I'll still have to make up smaller nuts... - the flange on the pivot mount is only 6mm wide, and standard M3 nuts don't have enough clearance to turn there.   

For starters I'll just use screws or cap screws where things are tight - the main thing is I want to get the engine to a point where it is fully assembled so we can set about exploring how to set the timing and maybe add that bit of detail to the plans thread.  I think I know how to set the timing, but I also think there's a bit of a gotcha involved...  Once its running, I'll get down to the detailing.

Kind regards, Arnold

[arnoldb]

I had a shop session this afternoon.  As mentioned earlier, there are some areas where standard 3mm nuts will not fit for mounting things.  I need to get bits and pieces of the engine stuck together slowly for test-fitting parts together as they are made from now on, so I turned up a handful of 3mm bolts from some 5mm hex brass:


A note to fellow builders here:  The cylinder feet are particularly difficult to bolt on.  One's fingers can't get between the base of the mountings and the upper flanges - so a pair of pliers or tweezers is needed to get fasteners started in there.  In addition, there is very little room for using a spanner (wrench) to tighten up the inside fasteners of the mounting feet.  In fact, once the first mounting foot was bolted to the cylinder, I fiddled around for half an hour and couldn't get the second foot's inside fasteners installed at all.  If you're not in the mood for an inordinate amount of fiddling, it may be easier to keep the cylinder mounting base plates and T-top sections as separate pieces and add mounting holes for two or three M4 countersink screws between them.  That way, the "T" sections can be bolted to the cylinder block easily, and then the base plates screwed to those.

After the fiddling around, I felt in the mood for making something easier - so I turned up the piston.  It's a bit too-close a fit in the cylinder, but that's OK, as I still have to lap the cylinder bore out to smooth it up:

As you can see, I chose the "alternate" piston configuration.

On to the piston rod, and I chose a bit of 6mm stainless steel rod to make it from.  Here the piston end is turned down to 4mm and threaded with a tail-stock die holder:


The cross-head end received the same treatment, and the piston rod was done:


Digging around my materials, I found that I don't have suitable bronze for the cross-head.  Brass would do just as well, so I used some 22mm brass rod to make a start on that.  I turned it to a smooth slide fit in the cross-head guide, and then drilled and tapped it M4 to match the piston rod.  You might have noticed that I didn't add a tread run-out groove to the piston rod, so to make sure it screwed in nice and flat on the cross-head, I just used a center drill to add a generous chamfer to the threaded hole in the cross-head - now the piston rod can screw into it nice and flat:


I mounted the dividing head in the mill vise, and started milling the flat sides of the cross-head:


After the second flat was milled, I drilled a 5.9mm hole trough at the correct position:

That hole was then reamed to 6mm.

Seeing as I was already working on the mill, I just transferred the chuck to the rotary table and used a slitting saw to part the cross-head from the parent stock.  Here is where I stopped - with just a tiny sliver of metal still left to cut.  Any further, and one have to play "Find and pick-up" after the part got flung somewhere during final separation:

Also clearly visible in this photo is the "generous chamfer" I mentioned earlier.

After de-burring the cross-head, this is the set of parts for today:


I stuck that lot in the engine and ended for the day:


There's still a bit of tightness when moving the piston rod, so I'll have to find out where that's coming from.  It shouldn't be difficult to fix though, and I have a hunch once the cylinder is lapped it will be gone.

Kind regards, Arnold

[vcutajar]

Slowly but surely, bit by bit, it is getting together and it is looking really good.

Vince

[steamer]

Looking good from here!

Dave

[Captain Jerry]

That is looking very good, Arnold.  The assembly shot gives a hint of things to come. 

I usually read your posts very carefully and several times as well but somehow I missed your explanation of the reason for the square shoulder on the valve disk shaft and the alternate method to tighten the holding nut.  It might have been more appropriate to post my solution at the time but others may like this alternative that I used on my earlier Corliss.  The problem is that the shaft rotates freely in the mounting plate making it impossible to torque the nut on the end.  My solution was to drill an oil hole in the top side of the mounting plate spigot and a corresponding hole through the pivot shaft. To torque the nut on the end, just stick a pin in the hole to lock the shaft and torque the nut.  With the pin removed, the hole provides a convenient way to oil the shaft.  I found that there were other times when it was helpful to be able to lock the shaft such as during assemble of the linkage and adjustment of the valves.

I do thoroughly enjoy your detailed progress posts.

Jerry

[Tennessee Whiskey]

Arnold, great job with the files. There have been many a fine double barrel hunt your land that were built using a great bit of hand filing.

Yo Redneck
Eric,

[swilliams]

Nice Arnold

Looking impressive

Steve

[Bearcar1]

IIRC, Arnold, you had mentioned the height of the mounting feet as being a bit on the shallow side and had thought about making them taller. This of course would have made an impact on the heights of the bearing standards and so on. Anyway. I am certain you will no doubt ferret out any other *surprises* that may lurk in this design. This type of thing is mainly just a minor inconvenience and nothing more. You are soldiering on like a trooper.


BC1
Jim

[Don1966]

She's really starting to look good Arnold and as Steve said very impressive. Still following here with great interest.

Don

[sbwhart]

She's comming on well Arnold 

Stew