Muncaster's Joys Valve Engine

[Jasonb]

The crosshead is tapped, as the bolt is tightened it pushed down on the wedge which closes up the split bearing, the nut is to lock the bolt in position.

The end of the bolt is likely to be turned to core dia and slightly rounded at the end and locate in a shallow hole in the wedge

[Don1966]

Simon following you photos is like being in a class room. You give a great step by step. I like............

Don

[b.lindsey]

Nice to see you back at it Simon...hope the trip was enjoyable too!!

Bill

[smfr]

Thanks folks! It was a very enjoyable trip, Bill!

A bit more progress on shaping the main bearing supports over the past few weekend days.

If you look at the last picture you can see that the radius on the sides (that I bored earlier) doesn't bring the end face of the columns down sharply enough to meet the flat top face of the end cross piece. That would both leave some awkward profiling to do later, and also not make it easy to add the holes used to secure the base to the substrate. The plans lie, and suggest the simple radius that I bored before, but it's really a non-circular curve.  So I had to fix this!

This photo makes it clearer what I need to remove. The two side pieces are ganged together, requiring a nice long endmill to remove the material.



I just nibbled up to the line:



and then filed away the tool marks with a combination of round and half-round files:



The sharpie marks are so that I can see what material is being removed. The parts are still ganged together, and I had to take care to keep the files perpendicular to the part to avoid crooked faces.

Now it's much closer to the plans:



Now to work on the bosses around the main bearings. There's a small radius feature here that I'd like to replicate. First I had to mill the bosses to final thickness (clamping the parts will require shims from now on, because here I lost my original surface). After some careful marking out, using the holes as the datum, I was ready to use a 1/16" corner-rounding end mill to cut the radius. I had to grind the tip of the end mill down to be able to use the cutter here, especially on the lower edge (remember that the part has a "casting angle" milled into it).



Because of that casting angle I can't get the cutter flush with the surface, so we are left with a small lip that requires some filing to remove.



This photo shows the files I used. I've ground a safe edge on the one in the top left (which was surprisingly easy and makes the file incredibly useful!).

But before we do too much filing, the corners need rounding! Time to break out the rotary table, center the part on the punch marks for each corner, and carefully do the radii:



Final result after some cleanup with files and wet & dry:



Now the final step on these bosses is to mill away the area where the bearing flanges will go, and a 3/16" end mill gives the right radii for the corners. I need to be fairly accurate here:



The central part will get milled away after base assembly, to make sure both sides line up. And that leaves us with this:



This rendering shows what we're shooting for. At some point I have to figure out how to do the interesting curves of the bearing cap 



Simon

[Jo]

Nice bit of profiling Simon 

I would have thought that after that those cap curves should be a breeze. (I'm assuming that you intend on putting the bolting down pads on separately).

Jo

[Don1966]

Simon I don't know about you but I liked the look of that lip left after you rounded the edges. I know you want it to look like casting, but that wouldn't of changed the look. There are intricate details also in castings. Beautiful work by the way and your work has really taken off.

Don

[Tennessee Whiskey]

Simon, truly outstanding. I really like the " mill to and file the line" . As they say these days; "Back in the day" many very fine and accurate parts were produced in just that manner. Seems we may have another up and coming George amongst us.

Whiskey

[smfr]

I would have thought that after that those cap curves should be a breeze. (I'm assuming that you intend on putting the bolting down pads on separately).

Yes, there are various bolt-down pads that I'll put in separately; end-mill a pocket, stick in a bit of bar, add a fillet with Milliput or JB-Weld.

Now that I look at it that profile on the bearing cap is pretty close to three circles (small one at each end, large radius across the middle), so some rotary table work should get it close! I can make both in one go and then slice them apart.

Simon

[Jasonb]

Simon, do you have part 9 of the Muncaster series as that shows bearing cap details, as you say one large curve and two rounded ends.

[smfr]

Simon, do you have part 9 of the Muncaster series as that shows bearing cap details, as you say one large curve and two rounded ends.

  Not sure what series you're referring to, Jason. I'm going on the series of 3 articles in Model Engineer, 1905. pp 222, 273 and 320. If this same engine is described somewhere else I'd love to hear about it!

Simon

[Captain Jerry]

Simon

That molded boss around the bearing is a superb detail.  You seem to be more concerned with the upper profile of the cap but I think you can handle that with ease.  I am anxious to see how you carry that boss into the cap.  Really nice work.

Jerry

[Jasonb]

E T Westbury did a series over 10 parts in 1957 about Muncaster's models, yours is not there but quite a few other future projects may be.

PM sent

[Jo]

The 1957 article by Westbury discusses many of the features of the model engines that Munchester designed and bringing them up to date. Such as this alternative main bearing.

Jo

[ths]

Hi Simon, here's a link to the 9 articles that ETW wrote on the Muncaster engines. They are all downloadable.

http://www.replicaplans.com/MuncasterSteamEnginePlans.html

Cheers, Hugh.

[smfr]

I have now read and digested the Westbury articles, and found them quite useful! Thanks to everyone who pointed me in the right direction. I do notice from the bearing pedestal detail in the Westbury article that I shouldn't have milled out the slot for the bearings like I did, but I think it's OK: I'll just have thicker bearing flanges.

Work on the base continues, and I'm getting quite tired of milling Ally and wanting to get onto some moving parts 

I thinned out the sides on the bandsaw, after cutting some 1/2" slots so I could get the blade in:



My slotted bandsaw table worked nicely, and I used a bit of bar in the slot, with an adjustable parallel to keep the part lined up. Slow going, but better than turning all that material into chips! Both sides done:



However, when I checked the sides against eachother I could see that sawing away half the thickness made them go banana-shaped 



I didn't realise this would be a problem with Ally!

So there followed some fussing around with a bit of steel bar in the bench vise trying to get things back into shape. I was surprised how much it could deform without actually taking the bend. I had the vise about as tight as it would go, even with a bit of pipe on the vise handle.



I attempted various bends on both sides, checking the exterior surface for straightness each time. Finally I got some movement, and now have it so that the ends match up, but I think only one of the bends really took so one side is a bit convex, but that's OK; these are non-critical parts.

Now I just have to mill angled slots on each side for the that bit of plate at the back, and I'm ready to JB Weld these chunks together:



Next I have to start thinking about the top surfaces and their various features:



Simon

P.S. Just noticed that I did the bottom edge profile wrong