Muncaster's Joys Valve Engine

[ths]

Your bottom edge is probably as representative as Mr Muncasters. Don't worry.

Hugh.

[smfr]

The last part of faffing around before being able to glue the base together was to mill a couple of slots for the cross braces. The one next to the crank pit is at the usual casting angle, so my angle blocks come in handy for possibly the last time to hold the side at the correct slant:



Now to prep for bonding. I used the "peg and hole" method I prototyped earlier, with the addition of some threading in the holes and roughing up the mating surfaces with a small bur in the Dremel; this was more to give the epoxy somewhere to go than provide gripping, though I hope it does a bit. The threading was of the "whatever tap happens to fit" variety. 



The pegs were turned from random bits of small scrap, and, as before, have a flat filed on them to avoid hydro-lock on assembly. Here are all the bits after a cleaning with mineral spirits:



I did a trial assembly to make sure everything is on hand, since you have to be fairly quick once the epoxy is mixed. I used my glass plate, since this model won't fit on my surface plate, and a sheet of coated paper avoids sticking to the glass. The rod through the crank locating holes ensures that the sides are reasonably well aligned.



No pics of the expoxying (I was busy!) but here we are after assembly, with some clamps holding things together, and lumps of cast iron to make sure things lie flat.



That'll sit for 24 hours or more until the expoxy is hard.

That gave me some time to think about the bearing caps! I found a bit of stock that two will fit into, and large enough to contain the radius centers. Putting one on each end makes setups easier:



Then I could do the main curves with the rotary table in vertical mode, using my new favorite cutter, a 1/2" carbide end mill with a 0.06" radius corner. The finish profiling was done in 0.5deg increments.



Four lots of that, and the top curves were done. Then the end curves were just a normal rounding job in horizontal mode; I only had time for one this evening, so here's where I'm at:



These bearing caps have the same fussy profile that I did on the bearing pedestals; I have yet to mark out for those, but the process will be the same as before. The tops of the bearing caps should have oil reservoirs I think; I'm of a rectangular recess with a nice brass pyramidal lid, something like this:



Simon

[GailinNM]

That's a lot of very nice work Simon.   
Gail in NM

[swilliams]

Yep, what Gail said

Steve

[smfr]

Slow but sure progress continues!

Got both bearing caps profiled on the rotary table:



but I put this aside to focus on the base.

Inspection after the JB-Weld had cured showed a reasonably good result, but one end piece was a bit out of line and needed some cleaning up. At this point I could treat the base like a casting; take a file to the underside to get it to sit flat:



and then take a few thou off the high spots on the upper side to I can blend things together:



which required a bit more work on those curved profiles to get them to blend into the end flat. The end face also needed a lot of filing work:



so I attacked it with my biggest file, and eventually got things blended pretty well.

Now, to the top surfaces. I planned for the top plates to be 0.25" thick, but need a little more thickness, and I want to leave some surface features there to locate the crosshead slides, the cylinder block, and the valve pivot standards. So some 5/16" plate was cut to size and marked out:



The corner-radius end mill was a handy way to get a radius for the surface features:



The underside of the upper plate needed some work too; a slight recess where the valve link pivot block is located, and some thinning around the two holes so the thickness looks more appropriate in that area.



I've been thinking for a while about how to secure these top plates for JB-Welding. I could just rely on the JB-Weld, but I want some fasteners too. I could put in temporary screws, and later drill out and fill the holes, but I worry about the screws getting stuck in there with the epoxy. So I decided to make some aluminum, countersunk screws to hold the plates down, the tops of which will be milled off later. I needed 10-12 of these, so got my rhythm going like this:

Get about 3/4" of bar projecting from the collet chuck, mark off 1/2" (thread depth) with a marker. 2-3 passes with the Al insert tool takes it down to a bit over 3/16":



Swap to another insert that happens to give me a 45deg angle, align it with the end, set the carriage end-stop using a 1/2" drill bit, do a couple of passes to go down to final diameter and get the bevel (after the first one, I can use the dials to get to final diameter):



Swap the belts to go to low speed. Use a tailstock die holder to thread under power, stopping once to clear chips, and carefully holding the die holder by hand, letting it slip when it hits the bevel. Back off under power (low speed!).



Back to high speed. Touch up the end of the threads with a file, swap to the parting tool and part off, leaving some material on the head to cut the slot:



And repeat!

I also turned some pins from bits of scrap to pin the joints where there isn't room for a screw:



Without any support on the tailstock end, they come out with a bit of a taper, but that's just fine for what I want them for.

There that little lot, just needing some slots cutting (which I'll probably just do with a hacksaw):



Now the next stage is to get the top plates accurately positioned on the base to drill holes for the screws and pins. I have a accurate centerline on the plates, and took some time to line up the base on the milling table:



I have a plate clamped to the milling table with the engine base sitting on top. With a bit of bar though the temporary crankshaft holes, I used an indicator to get the base aligned as accurately as I could. Then I used an edge finder on the bearing standards to find the centerline, checking my result with a parallel adjusted to fix exactly on either side between the edge finder body and the standard.

And then it was time for dinner and 

Hopefully I'll get some time during the evenings this week to get the JB-Welding done. Next steps are:

• Align plates to centerline, and clamp
• Drill, countersink and thread for the Al screws around the edges, and drill for the pins
• JB-Weld and fasten with the screws, let cure
• Mill non-critical surfaces down to final height, lots of corner-rounding
• Accurately mill channels for the crosshead slides, cylinder block pedestals, main bearing slots
• Finishing. Lots of finishing   

Can't wait to get this base out of the way. I think the next part will be the cylinder block, and I've almost convinced myself to make it from two lumps of cast iron which I already have, rather than ordering a single 4"x4"x2" lump. Just need to figure out how to bolt them together.

There's also the matter of the exhaust. As designed, the exhaust from both cylinders passes through a passage between them and through a hole in the base casting to...nowhere. That seems like a great way to spread an oily puddle of water over the bench! So I think I'll put an exhaust pipe under the cylinder block and exiting through a hole in the base, but with my two-part cylinder block that means part of the exhaust passage intersects the join between the two sides, which could be leaky. Not really sure if that matters for exhaust, though? 

Simon

[smfr]

Here's a picture of the cylinder blocks (in my split version), with the valve plate. Note the cavity between the cylinders for exhaust. Hopefully this makes it a bit clearer what I'm talking about!



Simon

[swilliams]

Nice stuff Simon, I'm enjoying your thread

Steve

[Jasonb]

Simon, think about bringing the exhaust down into the wooden display base and out the side, something like this



Rather than all that machining to form that large exhaust passage why not leave the mating faces solid and drill mill a passage, you could go horizontally to join the two exhausts and then vertically down either half & half or offset the exhaust so it comes down in one block only to save thinking about a long gasket joint. Solid would also give more options for joining the two halves.

J

[smfr]

Thanks Jason, that gives me another option to think about, though there's a gap between the cylinders and the base in the middle, so I'd have to have a bit of pipe somewhere. I may decide to bring the exhaust for each cylinder out of the back of the cylinder blocks, and have a nice Y-shaped join made of copper pipe.

Quick update on the base: I finally got the epoxying done this evening  so it should be cured in time for finish machining over the weekend! Nothing too exciting in the process, other than finding that one of the top plates was also banana-shaped and needed a bit of milling to sit flat.

Here I'm drilling holes for some pegs to firm up the rather skinny joint adjacent to the crank pit:



Note the clamping arrangement with the large clamp; I need to keep the clamping force over the sides, otherwise I'll cause the plate to bow in the middle. Some drill bits ensure that the existing holes stay aligned.

A quickie fixture with some threaded, countersunk holes keep the screws in place to hacksaw the slot (I don't really care how pretty they are as they will get milled off):



and a dry run before epoxying:



Now it's all JB-Welded and sitting on the surface plate with some big lumps of cast iron on top 

Simon

[Jo]

  Now the difficult bit...

How long before you want to fiddle with it  .. It really needs a couple of days

Jo

[smfr]

Now the difficult bit...

How long before you want to fiddle with it  .. It really needs a couple of days

Saturday, so it should have about 36 hours which I think is OK. Can't wait to get all the blue off and finally make this look more like a casting!

Simon

[Tennessee Whiskey]

Simon, I'm following along. The Stuart build has helped me immensely on my little PM. Build, so this one I'm storing for future reference. I don't think I'd worry to much about the base. As we old Southern boys would say; " You got it glued, screwed and tattooed, forty damn different ways. 

Whiskey

[Don1966]

Simon you have been busy and some how I missed a few post, but have caught up now. You have done some impressive work and it shows. Great work as usual. 

And Jason I still love the Benson it's on my list to do.  That is when I get better at it.

Don

[steamer]

I haven't been in on this thread much, and a shame I haven't...I've missed a great deal of wonderfull work!

Go Simon!

Dave

[smfr]

Thanks for the comments, everyone. I'm glad I didn't lose you all with my drawn-out tales of glueing lumps of Ally together! 

Here's what things look like after curing, with a nice bead of epoxy around the screws suggesting that penetration is good 



and, as hoped, the screws are almost invisible after milling and sanding:



I milled off the overhang, and followed up with a corner-radius end mill on all the horizontal corners:



and then spent some quality time with the file collection to blend all the joins. I started with a coarse file, but ground the end smooth so that it didn't ding the bottom profile if I went too far. I found that crossed 45deg strokes did a good job of taking off the material:



The corner edges had to be radiused by hand, as well as blending the radius up the bearing pillars, and the radius gauge came in handy for that:



Rubbing down with 150grit wet & dry with WD40 takes off most of the tooling and filing marks.

This still looks a bit "blocky" and not like a casting. I'm going to have to study the drawings to see whether I should adjust the radii. 

Simon