Building a Muncaster entablature engine

[Jasonb]

Looking good.

There should be 2mm of thread sticking out the back of the crank for a locknut and the space is 3mm wide.

[Gas_mantle]

Thanks Jason, the amount of interference from the nut is small so I think I'll just make a smaller one.  I might even remake the crank pin, it works ok but I could do with reducing the length of the bearing surface between the head and the crank web, I made it a bit longer thinking a bit of play would be needed but a close fit would be better.

Thinking ahead a bit, did you use any special tooling to drill the 0.8mm holes in the pins ? I've never drilled anything that small and still need to buy some very small drill bits. I'm guessing my bench drill or mill will lack sensitivity.

[Gas_mantle]

Hi, all

I'm now managed to get a bit further forward by making the valve and the glands, all simple parts but still a step toward completing the model.

This engine has the usual slide valve design with a pocket on the underside and a slotted cross to take the valve rod and nut.







It's a snug fit in the but slides nicely



Onto the piston rod gland, I decided to use the cylinder cover to hold it in the vice and use the boring head to profile the sides. I've never done this before and wasn't sure how it would go, I was a bit concerned that with the mill running in reverse the head may try to unscrew from the arbor but with light cuts all was well.





With one side nearly done it seems to be working ok.



With the same method for the valve rod gland I arrive at this assembly





They aren't perfect but I'm reasonably pleased with the result.  That pretty much only leaves the eccentric to get the engine running 

Peter.

[Jasonb]

Looking good. You can run the mill the right way but it just needs the tool grinding a bit differently.

[Gas_mantle]

Thanks, I did wonder about using the mill conventially but I had a few brazed carbide cutters that came with the head so I thought I'd give it a try in reverse just cut a few mm of brass.

I'm looking at making a couple more glands for the steam inlet and exhaust as I'd like to have plumbing coming up through the base - ideally I'd like steam valve on the base but I'm not sure there will be enough room without ruining the appearance.

[pgp001]

Looking good Pete. Will it be at Doncaster this May ?

Phil

[Gas_mantle]

Thanks Phil. I'm not sure about Doncaster, I have thought about it as I'll probably have it finished to the point of getting it running in a week or so. I'd then like to spend a bit of time adding the plumbing, the base, painting etc.

I have a few castings and some barstock that a couple of forum members gave me to make a replica Stuart 10V, I'd like to start on that very soon and do build log following roughly along Andrew Smiths guide book.

[Gas_mantle]

Hi

Just a few basic turning jobs for the next 2 components but for the benefit of other beginners who may be following along I took a few photos to show. I had wanted to make the eccentric strap next but found I haven't any brass of the right size and have now ordered some.

Although unable to make the strap I decided to tackle the eccentric and make a pulley.

I'm not sure how others tackle eccentrics but I usually turn the larger diameter first (in this case 20mm) then offset the throw in the 4 jaw using an indicator to measure ( 3mm).



Next turn the smaller diameter and drill for the crankshaft, it's at this point I realised I hadn't cut a groove in the major diameter before offsetting 



The groove needed is 1.5mm wide so this parting tool is just the right size, I bought it when I first bought my lathe - it was cheap but it was cheap because it is rubbish. It will do for cutting a shallow groove though.



With the groove cut and parted off I turned the part around and Loctited to a close fitting mandrel to face of the back and add a small raised boss.



The pulley was made using a similar technique on a mandrel so that gives me 2 more parts to cross off the list.



With them both installed on the crankshaft they nicely fill the void in the entablature.



All being well I ought to be able to get it running this week - just need my brass to arrive now   

[crueby]

That's looking great, very good proportions on everything.   

[Gas_mantle]

Thanks Chris, I can't take credit for the proportions though - I'm just the guy twiddling the knobs according to the plans :-)

[Craig DeShong]

Really nice, the brass accents really makes the engine POP !

[Gas_mantle]

Thanks Craig, I have considered leaving the brass capitals untouched when I paint it 

Not really a proper update today but I've been thinking about the plumbing which I'd like to run under the base and ideally I'd like to fit a globe valve also. There isn't a lot of room between the columns for a valve but I looked at the possibilty of fitting one to the front of the valve chest.

Here I have knocked up a temporary prototype cover with a boss for the valve and would appreciate any feedback - does it look naff and unrealistic ? Is the valve too big ?







I haven't drilled the base yet so nothing is finalised but any comments would be a great help.

Many thanks 

[Jim Nic]

You could position the globe valve horizontally across the valve chest and put either a bend or a 90 deg junction to lead the inlet pipe to the side and then down through the base.  To my eye a smaller valve might look a little more in keeping with the engine.
Jim

[Gas_mantle]

Thanks Jim, its useful to get a second opinion 

I tried your idea of having the valve horizontally but the handwheel then sits outside the columns and doesn't look right    I can get a smaller globe valve but that takes the inlet pipe down to ³/₃₂" and my gut feeling is that is too small (I want to run on steam now and again)

I'll have a think for a few days as I'm not committed to anything yet.

[Gas_mantle]

Hi all,

All that's need to start testing the engine are the eccentric strap and valve rod fork, I tackled the strap first and began with boring a 20m hole.



I find some of these brazed carbide bars are ok and some are dreadful but this small one does a reasonable job and is ok for this simple task.





Next its on to the rotary table to cut the outer profile, I started of using a centre in the mill spindle to get the part close to centre before setting up properly but was getting nowhere like this.



Eventually I gave up and did what I should have done from the onset 



So here we go....



Taking shape





Milling away the waste.



I forgot to take a photo before mounting it on the engine but it turned out reasonably well so it's the valve rod fork next.

To make this part I decided to take a different approach to the way I normally do it and started with round stock in the lathe.





Next job mill the 4 side faces





A 3mm slot drill to take out centre





Then a few small cuts to round of the end.



I didn't cut the centre slot quite deep enough as can be seen here but a file sorted out the last little bit



That takes me to this nearly finished engine  I've not yet decided what to do about the pipe work so for now there is a temporary fitting to accept an air line. I need to make the valve fork pin plus a few small items like oil cups and decorative nuts for the columns but them machining is pretty much complete.









I haven't yet fully tested it on air yet as the valve rod needs a few mm taking off but I'll do that tomorrow and take a video of it (hopefully) running. I did try a few days ago just moving the valve by hand and it does respond well so I'm optimistic that a bit of tinkering will sort things 

Peter.