A Tandem Compound Mill Engine

[deltatango]

Between the crankshaft and the high pressure cylinder is the base for the slide which guides the crosshead, this also supports the valve rockers and governor so alignment and squareness are necessary. As with the main bearing base the casting was filed close to flat on the underside then the top machined to make the first datum surface:



I hope the world doesn't run out of 8" x 4" file cards (I'll explain what those are/were for younger people if necessary ) before I cease to need them!
The casting was turned over and the underside finished flat and to thickness:



then flipped again to clean up the crankshaft end flange as the next datum:



At the same setting the back edge was milled as the third reference face. It was clear from the casting fondling stage that there was very little, if any, metal to spare on the width so there would have to be compromises on the flange dimensions. The main bearing base was added to the set-up so at least the flanges would line up, even if they were under nominal size, and the longitudinal centre line could be aligned between the two parts:



Locating the centre line from the reference edge I dug out the slide way with an oil well at each end:



Some holes for handrail stanchions and holding-down bolts were next. The part-circular cut out to clear the HP cylinder flange was very rough as cast but cleaned up fine later with half-round files:



The mounting face for the governor was the final surface that needed machining and the bolt holes in the flange and that of the main bearing base were drilled in the same setup :



Just one more base casting to go then on to smaller, maybe more interesting, bits.

David

[Ramon Wilson]

Hello David - good to see you making more progress 👍 At this rate you'll soon be catching me up

I sent you and Neil Lickfold a PM from my old laptop when I was on holiday - it shows as sent but he didn't get his, can I assume you didn't either?

Decided to carry on a bit further on mine, near finishing the governor parts at the mo

Regards - Tug

[deltatango]

Tug: I've got a way to go yet to even see the dust you're making but I am moving (PM dealt with). I'm also really pleased to see you getting back to work on this engine - seeing yours was what started all this.

The base plate for the two cylinders was tackled much the same as the other base castings. Neither side was smooth and flat enough to leave as a reference so the top side was filed smooth(er) and set downwards on the mill table to take a skim from the bottom:



Lots of clamp juggling was involved as was the case for the top side after turning the part over. Also at this setting one long edge was milled (after changing the face mill for an endmill):



I don't have a picture of machining the crankshaft end flange but that was the second datum face to be cleaned up. After that the second edge was milled:



The drawings show four cast-on bosses for holding down bolts but the end two were missing on this piece and were replaced with steel inserts:



The blue line shows the nominal location by measurement from the flange but this isn't critical so I drilled the holes concentric with the casting's rounded corners and used JBWeld to fix the inserts in place.

I don't have any dislike of working with wood but the "marine grade" ply I bought to build up a core for the engine base is horribly splintery and the dust mask was essential, nothing like the marine grade material I've used in the past. Anyway, it is very stiff, and hopefully its stable, so there is something to rely on for long-term alignment. With the two pairs of flanges bolted up and the main bearings aligned using the crankshaft the holding down bolt holes were drilled and some of the studs made so the work so far could be put together:




I've stocked up on BA fasteners with smaller heads and I think these really improve the appearance, hope so anyway because they're damned expensive!

David

[Ramon Wilson]

All this work takes me back a bit David - glad all that CI dust is in your workshop and not mine again 

It's a big old base needed for sure - have you had any thoughts on filling that open area at the back? I'm at a bit of a loss on that - possibly a neatly printed description plate?

I had a new belt arrive today - much better, pulled flat the stretched out length was 166 260+ mm as ordered. I have to take the shaft out to fit it but can see that the tension will be much better - https://www.ebay.co.uk/itm/Turntable-Drive-Belt-166mm-record-player-belt/280828907661?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

You are right about the fasteners - pricey little devils and this engine just eats them

Regards - Tug

[deltatango]

Tug, Thanks for the info on the governor belt, now I know what to look for but I'll wait until the actual bits are in place before measuring the length.

As for cast iron dust the Karcher industrial vacuum cleaner is probably the "tool" that gets turned on most often at any time. When I'm machining CI then it gets even more use.

That big empty space is an issue. I have thought about moving the steam stop valve into it and maybe adding some dummy small valve levers but that makes the piping messier. George Watkins' book "The Textile Mill Engine" shows pictures of a lot of engines and the engine house interiors, some of these have magnificent Victorian CI lamp standards in that space, fluted columns and elaborate lampshades, one of those would be fun to model. However, in Vol 2 of Watkins picture # 48 shows a large alternator in that area with a short rope drive from the flywheel. In between the introduction of electric motors for driving machines and the National Grid being able to provide all the power needed, some mills (maybe mostly weaving sheds) had both rope drive and electric power transmission. Drawings for a 1920s 500kW alternator would be very useful.

Back in the workshop I decided (hoped?) that I'd worked out the locations for the eccentric keyways - I'd found the original drawings difficult to interpret for certain. The positions I used are:



and the Arduino controlled dividing head made setting out the angles easy. There's a reference line scribed across the crank and the shaft end to align things, just have to remember to get the crank pointing the right way on final assembly:



Next up are the eccentrics and straps.

David

[scc]

 

[Ramon Wilson]

Hi David, I'm not sure what the actual 'diameter' of the belt is that I have currently fitted but though it does work it is a bit on the slack side. Of the two I bought the 166mm dia appears to be about right. I have yet to remove the flywheel in order to fit it though.

Like you I have several of Watkins books -  The kind of layout you refer to with central floor mounted stop valves, lights etc is usually  associated with twin layouts - single cylinder or tandem - but most inline plants appear (though not always) to have the stop valve on the hp cylinder. As you can imagine I scoured the ink off the pages looking for ideas and details and based mine on several images. Most of these in-line engines were erected in some pretty tight engine rooms as indicated by the angle of which most images of them are taken. Great books by GW, just a shame (from our perspective) that the individual engines are only covered by the one image.

I'm pretty certain the 45 and 42 degrees for the Corliss set up are the same as Peter Southworth had annotated (too late now to go and check).

Got the governor linked up today - looking good and works well but still more linkage to come. So far, overall, I have found the drawings to be fine to work too but the build up of the links to the cut off levers is quite misleading. The GA side view shows the drive lever to be on the outside of that top bracket (and outside of the governor lever too) though differs in the plan view. I don't  think its going to quite work out that way on mine

Hope you get some more good progress in in coming days  - afraid I can't help with drawings for an alternator

Regards - Tug

[kvom]

Would you be willing to share the Alibre part files?  I am wondering if they can be converted to Solidworks.

[deltatango]

Tug, thanks for the comments, I've found some pictures of generators and alternators in 'Modern Power Generators" by James Weir French, Volume 2 of 1908 so they are more or less the correct period. There's a lot of work to draw something up from the pictures (and wonderful paper fold-out diagrams) but it would be possible, I wouldn't try to make a working version!

As I've modeled it the HP cylinder with the valve gear looks like:



The link lengths aren't quite right yet, the "Trip Gear and Dashpot Arrangement" drawing isn't dimensioned so I'm having to scale from it, not good practice I know but I'm trying to get the Alibre assemblies to move as near to reality as possible. I don't think this is totally possible with the current set of motion constraints but I hope I can make a video of the valve motion without being able to simulate the trip action.

In his build log Tug also pointed out the problems with assembling the eccentrics so I 3D printed one of each type (Corliss valve and slide valve) as originally drawn so I could have a play with the pieces (Corliss on the left, 1/8" throw, slide valve on the right, 1/4" throw):



It's just possible to get nuts on the studs for the slide valve eccentric but adequate spannering doesn't seem possible; on the Corliss side even getting a nut on was challenging. These will have to be solid and "decorated" somewhat to improve the appearance, although they aren't really all that visible.

Before starting on making the eccentrics it looked like a good idea to have the straps to hand to use as gauges so the three GM castings were fondled and found to have plenty of machining allowance, to have the core hole close to the centre and remarkably close to circular. They were mounted off this to start machining:



with both sides smooth the external lumps and bumps were brought to size in sequence:




the clamp stud holes drilled and the two halves slit apart:



then set up in the 4-jaw chuck for boring the hole to size and turning the internal groove:





Thanks for looking in!

David

[Ramon Wilson]

Thanks for the drawings David - I do admire your ability to do such 

I had come to the conclusion that the format was as you have it then 'found' the undimensioned trip gear drawing (twice scale) that shows it correctly. Hadn't paid too much attention to that whilst making the parts.

I have found that there has been one or two parts that required 'scaling' but as you say no alternative. So far though it appears to be working out. I think I will have to modify that top bracket slightly as mine is slightly wider than dimensioned - it will need a cut out to clear the drop links to the cut off arms.

The one thing I am wondering about is that the trip arms only engage the trip block by their own weight which isn't a lot - they will certainly have to have a very free pivot! Have to see how that works out in practice.

Keep up that great coverage 

Regards - Tug

[deltatango]

Tug,
Thanks for the kind comments re the drawings (screen dumps in this case), those are almost a given once you've built the CAD model, that's the trickier bit. You could always download the Alibre Atom3D 30 day free trial and I'll send you some files to look at & play with 

I was stressing about having missed something that would make the trip arms positive in their action but I really don't think that there is anything but gravity. Jeweled watch pivots come to mind as being necessary! People have built these engines and got them to work so it must be possible. Is their anyone on MEM who has finished one? Knows of a finished one?

Regards, David

[Ramon Wilson]

Yes David I've seen two run and one other turned over by hand.


The first was a twin tandem compound, corliss and slide valve but it did use a lot of air. The second, built by Terry Fleet who was the original instigater of the design, I've seen run several times at our local show. That is a cross compound (both corliss) I do remember Terry telling me he had to fiddle a lot with the valve setting before he got it running (don't think about it - think positive I tell myself )

The other was a single corliss bought by a friend who brought it round to show. It was bought as a non running example but the reason was soon traced to a poorly made linkage on the trip blade. Haven't seen him since so don't know if he got it running - I'll ring him later to see.

Thanks for the offer but I think I'll forego the Alibre at this time   

Regards - Tug

[deltatango]

With the straps available to use as gauges the eccentrics themselves were turned on a stub of FCMS bar:



and parted off using the rear tool post (best thing since sliced bread IMHO, particularly with a TC tipped tool):



The three thin slices of steel were tricky things to hold. Machining soft jaws to take them was the first thought but, just for once maybe, I stopped to think a bit further ahead and instead turned a mounting hole in a bit of Al bar:



The first attempt to use hot-melt glue turned out to be a not-quite-good-enough idea and I went back to using cyanoacrylate to hold the eccentrics to finish the second sides and start the marking out for the crankshaft hole:



Centre-punch dots are to keep each part associated with its fitted strap.

Transferred to the 4-jaw for boring and bored out to fit a plug gauge turned to the measured crankshaft diameter:



If I had an arbor press and a set of broaches then the keyways would be really easy but I haven't been able to justify the cost for something that wouldn't get much use. What I do have is the slotting head that came as part of the package with the Aciera mill and I used this for the first time for the flywheel and governor pulley keyways. For use in the slotter the cutting bits are carried in simple 12 mm diameter tool holders and I made up another to take 5 mm round HSS bits. A block of scrap Al was the first test piece:



and when that 1/8" key just pushed in and sat there it was a good feeling!

The previous jig now came back into use after boring it out to give the slotting tool somewhere to run into and adding two M6 screws for clamping:



That good feeling came back when the keys fitted nicely in all three parts:



Because I haven't split the eccentrics I drilled and tapped them for M4 grub screws (no pictures) to prevent any possible sideways sliding and the progress so far looks like:



There's still a long way to go to catch Tug but hey, this is progress!

David

[Ramon Wilson]

And good progress it is too David  keep it coming.

I don't envy anyone having anything but I wouldn't mind having that slotting head  - a very nice facility when you need it eh? 

Regards - Tug

[gary.a.ayres]

... and I wouldn't mind having the Aciera mill. Pure class...   

Lovely engine developing here.