Stuart Twin Victoria (Princess Royal) Mill Engine

[Dr_GMJNParticipant @dr_gmjn]

Thanks Jason – I did take some y- cuts each side, but right at the end of the process. I’ll try as you say.

yes – I got mixed up with the paint/bright bits of the covers.

Is there a tool similar to a scraper that would get rid of machining marks like this? It takes ages with abrasives even though I can’t really feel the marks with a finger nail. What about a Dremel with the sandpaper discs?

[Dr_GMJNParticipant @dr_gmjn]

Talking of valve chest covers, I want to put an oiler in the middle, so am planning on leaving a circular raised face in the milled centre. I was looking at this engine last weekend:

And noticed it had an oiler on the cover as well:

It seems to have two taps, perhaps so you can oil during running. Are these available for models?

I think a single tap with a screw cap might look neater, but just wondered.

Where is the best supplier for fittings like these?

Thanks.

[DiogenesIIParticipant @diogenesii]

Posted by Dr_GMJN on 19/09/2021 07:37:02:

..Is there a tool similar to a scraper that would get rid of machining marks like this? It takes ages with abrasives even though I can’t really feel the marks with a finger nail. What about a Dremel with the sandpaper discs?

I think there's a typo in JB's comment – I think it's meant to say 'File and then emery paper'.. ..decent Swiss files will whip marks like that off in a most satisfying way – I know it's an old cliche, but if you get a set, you will find them out on the bench all the time and wonder how you ever did without them..

The trouble with small discs is that the edges are thinner and cutting faster than the face – if they touch the side of the spigot, it's easy to cause other marks that are even harder to remove.. ..it's also a process that's always on the edge of being uncontrolled, never a good thing for precision work in metal..

[JasonBModerator @jasonb]

Yes that should have said file, I'd probably go for a 6" No3 smooth cut and then 100g Emery, don't pussy foot about with something too fine like 240g. You can get small triangular scrapers but I think you will be there for longer with one of those, I tend to keep mine for clearing burrs from the inside of bores with cross holes.

I only tend to use the dremel to add a bit of texture rather than smooth things off in which case the orange/beige teardrop shaped grinding bits work well just lightly run over the surface.

[JasonBModerator @jasonb]

I've not seen the two cock oilers or fat pots available from the ME suppliers, usually a case of making your own. Yes the idea is you can fill with the lower cock closed while the engine is running then close the top one and open the bottom to allow the oil in, Early ones that would have used animal fat you had a larger top opening so the thick fat could be put in and then the heat of the engine would make it less viscous so it would flow in.

As our needs are different to a working engine and your scale quite small it may be easier to have the cocks as dummies and just use it as a fancy oil hole plug.

One I prepared earlier but as it is on a 2/3rd scale engine a bit less fiddly.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Dr_GMJN on 19/09/2021 07:47:40:

… noticed it had an oiler on the cover as well:

It seems to have two taps, perhaps so you can oil during running. Are these available for models?

…

No idea if they're available for models.

According to my book, this type of lubricator is called a Cylinder Oil Cup, or Tallow Cup, depending on whether the lubricant is oil or tallow. "Made of Gun-metal, upper cock for filling; lower cock for admitting the oil or melted tallow to the cylinder or steam feed pipe. The steam carries the oil forward to the piston and valve."

Although it looks similar to an ordinary Oil Cup, Tallow Cups work on a different principle. This type of lubricator runs hot enough to melt tallow, and it adds oil to steam, not drip feeding a bearing like an ordinary lidded Oil Cup. Two valves are necessary for refilling on a Tallow Cup because the lubricator's output is normally at steam pressure; opening both valves with the engine running would blast the operator with a jet of oily steam. Potentially dangerous on a full-size engine.

Does anyone still use tallow as a lubricant these days? Being rendered animal fat makes it liable to go off and become a smelly bio-hazard, but it has both grease and oil properties. Grease is best for slow moving joints, as when a steam engine is started from cold, and oil is best when an engine is running hot and fast.

Absence of smelly tallow is another reason I suspect visiting a heritage steam engine can't be fully authentic. Apart from the H&S precautions, the engines are too clean and brightly lit; many are turned cold by an electric motor, and if the engine is being steamed, the boiler burns clean coal or coke. The visitor doesn't experience the heat, hard work, long hours, or dimly lit stink of an actual industrial engine earning a living.

Dave

[Dr_GMJNParticipant @dr_gmjn]

Thanks all. I’ll probably end up using a simplified oiler then, even one with a cap and no lower cock.

The engine in the picture runs on air, but some run on steam on open days a few times a year. It’s at Wortley top forge near Sheffield – they have quite a few engines. There are more pictures here:

**LINK**

[JasonBModerator @jasonb]

Tallow is still used and available, often used as a thread cutting lubricant, not known of it going off and a tub will last a long time.

Those oilers still work on air as they don't rely on condensate to displace the oil, it just drips down. That one in my photo actually has a needle on the end of the "t" handle to regulate flow.

Doc you also need to consider the scale of the model you are making, the one in your photo is about the size of the original victoria but you are making a much larger engine which would likely have had some quite extensive oiling arrangements with sight glasses and oil feed pipes to the various moving bits rather than a simple fat pot. A look at Ramon's Corliss build on MEM will give you some guidance.

Edited By JasonB on 19/09/2021 13:33:46

[Dr_GMJNParticipant @dr_gmjn]

Thanks Jason, I’ll take a look at Ramon’s thread if I can find it. I’d like to get on with the covers while I’ve got some momentum going, and have a feel for the R/T. I don’t want to go OTT with a full lubrication system, but I’d like at least something that gets oil into the engine when running on air.

Anyway, got the other side done this morning. The vice stop method worked really well. I took cuts in y as suggested and the marks were less obvious:

I was given a set of small files, so used them to get rid of the larger machining marks. I found using a flat one, bowed very slightly convex was good for dealing with the surfaces away from the edges:

I do t have any Emery cloth, but used some #250 and #400 wet and dry lubricated with WD40. I would have gone further if they were to be left as bare metal, but I think as they are will give a good key for the primer:

This is the result:

I aimed to remove the absolute minimum from the castings, and the result was that a few places were missed:

I opted to leave them because a) I think they are the undersides, and won’t be visible once assembled, and b) Once painted it won’t be obvious anyway.

So regarding fitting to the cylinders. My plan is to co-ordinate drill the locating holes in the valve faces from the mill mandrel I made, and from the steam chest sides and ends. Hopefully this should ensure the valve rod and cylinder axes are parallel? Then I’ll fit, mark the valve faces and mill to size.

[Ramon WilsonParticipant @ramonwilson3]

Nice result Doc – a credit to your appoach

Re your comment on the Corliss – detail on the oiling system starts here

BTW a good material for making the glass of cylindrical oilers is the crystal clear tubes that protect artists paint brushes.

Ramon

Just found these pics from the Waller build that may be of use

 

Edited By Ramon Wilson on 19/09/2021 18:50:52

[Dr_GMJNParticipant @dr_gmjn]

Thanks Ramon – I found the thread on the other forum earlier. What an amazing model – everything about it is quality. It is better than many museum models I’ve seen. The lubrication system is impressive, but beyond what I had in mind for this engine. I think you described the glass oilers in another thread where I was asking about it: IIRC they are bespoke, made by you? I think I will design something similar for the crank bearings, with the cranked feed tube, but for the valve chest I’d like something simpler – perhaps just a brass cup with a sealed cap, and for the cross head slides, open cups similar to the 10V. I’ll look online for some OTS items. I found some on EBay earlier, but they looked a bit ornate.
Cheers.

[Dr_GMJNParticipant @dr_gmjn]

Posted by JasonB on 30/08/2021 20:04:25:

I've never found the need to do the separate CSK screws to hold the chest in place, I always just use the studs that run right through and retain the cover. Easy enough to slip a couple of larger nuts over two studs to act as spacers so the chest can be held in place when the eccentric rod length is being set then no need to be able to hold the chest without cover after that.

If you still want to go with them then I don't see the need for them being 4BA, get some M2.5 or even M3 CSK socket screws and use those.

Next job is drilling the valve chests. As you say, I can't figure out the need for CSK screws in the corners. It would seem to be better from a simplicity and load distribution point of view to just take all apart from the mid-side 7BA holes right through the block and drill and tap the valve face to take studs. The mid hole on the inlet side can't have a through-stud because it would partially obscure the inlet hole. So I'd end up with 8 through holes in the chest, and the two mid positions threaded for short studs (just for the sake of symmetry).

When you said use a large nut to temporarily fit the cover, was the nut just to compensate for the thickness of the cover? I was going to use threaded 7BA rod so wouldn't need a spacer. Is it better to make studs only threaded at their ends (as per the 10V valve chest studs)?

Thanks.

[JasonBModerator @jasonb]

Yes larger nut makes a simple spacer. I tend to thread my own studs, 3/32" rod will be fine for 7BA

[Ramon WilsonParticipant @ramonwilson3]

Hi Doc, yes all the oilers on my engines are bespoke – some just simple open top cups others to represent full size with glasses etc. Easy enough to make in a variety of forms. As Jason says your engine represents a much larger engine than that in your photo so the oilers should be in keeping.

Oiling of your engine cylinders would more likely be by forced lubrication in full size of a similar engine. I found over the years – running on air – that putting a good slug of steam oil into the airline entry will get carried around and coat all internal surfaces more than adequately enough so cylinder oilers can at times be simple 'dummies'

If you can get hold of a copy of the Textile Mill Engine by Geo Watkins you'll see all sorts of examples.

Ramon

[Dr_GMJNParticipant @dr_gmjn]

Thanks Ramon. I’ll figure something out. The crank oiler with the bent feed pipe looks tricky…

Moving on a bit – you mentioned PTFE piston rings a while ago (I think), for running on air. Can you give more detail of sizings and any piston redesign that might be needed?

I think it was PTFE…it was definitely some change to standard, but I don’t think the details were discussed.

Cheers!

[Ramon WilsonParticipant @ramonwilson3]

Hi Doc, didn't you share in the PTFE impregnated yarn I bought? There were three of us – I was sure you were one.

If so make the groove a little wider than the nominal width of the material and a little shallower – around 5 thou or so in both cases.

The piston should be a good 3-4 thou down on diameter so there is no metal to metal drag.

I use a sharp (new blade) scalpel to cut the packing with a scarf joint across the width not the thickness. The extra width allows for a little compression when fitting – once in the bore it will find it's own level and give a very good seal with extremely low friction.

When fitting the piston to the bore make sure there are no surplus threads from the packing running down the side of the piston.

Not disagreeing with those who prefer to use o rings but groove dimensions are much more relaxed and friction a lot less.

Ramon

[Ramon WilsonParticipant @ramonwilson3]

Hi again Doc, just checked through my PM's and yes you did share in the PTFE yarn. It's excellent material so you should have no issues fitting it

[Dr_GMJNParticipant @dr_gmjn]

Thanks Ramon, yes this is the stuff:

So about 0.005” protrusion on diameter ( if I can figure out the nominal thickness)?

And 0.003-4” piston undersized to bore diameter. Presumably the bore needs finishing to be very smooth / polished?

Also, I’ve been marking out the cylinder valve faces for milling to size. All looks fine apart from on one cylinder (on the left below):

The cylinder longitudinal midpoint is out w.r.t. the central valve port, by about 0.5mm. Presumably I can adjust the mid point of the slide valve to compensate with no ill effects?

The valve pads will be machined to the upper and lower scribed lines, giving equal flat areas on all 4 ends.

Thanks.

[Ramon WilsonParticipant @ramonwilson3]

Doc, if the machining inside the bore is as reasonable off the tool as you said then you shouldn't need to hone or lap the surface as such other than with some wet and dry paper.

If you turn a piece of wood or ally to about 30 – 40 thou down on bore size about as long as a cylinder and wrap some 400 wet and dry around it that will out smooth the surface more that well enough. Drill it through to hold it on a handle of some kind and cut a slot along it deep enough to slot one edge of the wet and dry into then wrap round so that the motion tightens the abrasive not unwraps it.

Re the valve ports – this is what I meant about cast in ones from Stuart. You may be able to accommodate the error with the valve position but if you want to be absolutely certain of identical positions then as previously said you have to fit an insert with correctly machined porting. Not difficult to do and a bit late in the stage of thing but still achievable if you desire to go down that road.

[Steve WithnellParticipant @stevewithnell34426]

Posted by Dr_GMJN on 19/09/2021 07:47:40:

Talking of valve chest covers, I want to put an oiler in the middle, so am planning on leaving a circular raised face in the milled centre. I was looking at this engine last weekend:

And noticed it had an oiler on the cover as well:

It seems to have two taps, perhaps so you can oil during running. Are these available for models?

I think a single tap with a screw cap might look neater, but just wondered.

Where is the best supplier for fittings like these?

Thanks.

That oiler is a 'shapely lady' I think. For my single cyclinder victoria I made my own, which isn't too difficult. Im not an expert, but I don't think the one in the photo is big enough.

I copied mine from this engine – for scale the screws are 12BA. This link takes you to how I made the lubricator for my Victoria.

Shapely Lady

[Dr_GMJNParticipant @dr_gmjn]

Thanks both.

Ramon – I think I’ll see how it goes before committing to making inserts. I don’t think it’s that far out, but I guess if it turns out to be a problem, it’s removing cast iron rather than adding it. The cylinders are OK, but I think they still need a bit of finishing in the bores, mainly to get rid of the slight discolouration half way down one of them, and also to make sure the JB Weld filler in the screw holes is truly flush.

Steve – thanks for the info about the oilers. I think on mine they will just be simple brass cups with lids, so I can drop oil in occasionally, rather than the reservoir type you describe.

[Dr_GMJNParticipant @dr_gmjn]

I had a go at the cylinder covers this afternoon. I’ve read the article method loads of times, but still couldn’t make head or tail of the descriptions: It says machine the plain cover spigot first, to a good fit to the cylinder, the reason being that it centralises the packing…but there isn’t any packing on that cover.

It then says make the spigot on the gland cover ends (the ones with the packing) a slack fit. It also says to machine the spigot diameter after facing, to ensure concentricity. Surely concentricity doesn’t depend on the face being true, plus if it’s slack, why is it important?

I was left wondering why in those cases bother with either spigot at all since one has nothing to centre, and the other is a slack fit anyway.

In the end I just went with what seemed logical. I assume when the article was written, the covers didn’t come with cast tails on the back, so I used those to mount in the chuck. I first faced the gland bosses, centre drilled them as best I could on the mill after marking with the verniers, and set up true in the 4 jaw. Then turned the bolt faces and re-faced the gland bosses to the correct depths:

Then drilled the piston rod and packing holes:

The 10V piston hole was reamed, but it says not to bother for this one. Which seems logical since it’s the piston and cross head that seem to define the rod position. Adding a third fit seems pointless, especially when the packing will centralise the rod. Anyway, that got me here:

Then sawed off the tails:

Made a mandrel as per the article:

Set up with a dti (both were within 0.002” O/D and 0.001” on the face, so I thought that was ok:

And turned the inside spigots and the flanges to thickness. I made the spigots a good fit to the cylinders. I can slacken them off if I need to I suppose:

Then finished the spigot faces in the 3 jaw:

I guess there was better way to do it than this, but it seemed to work ok:

[Dr_GMJNParticipant @dr_gmjn]

The castings where right on the edge of being big enough for the stated dimensions, in fact there are still a couple of pinholes on one of the gasket faces. The brass extrusion I bought was never going to be big enough to make the glands:

Got plenty spare…

I’ve got some brass bar, so I’ll try to make them from that:

Lessons learned: I should have bored the packing holes rather than drilled them – my smallest boring bar will just fit. Oh well, I think they will be ok.

Next job is to make a mounting block for them for the R/T vice, and get them milled as per the valve blocks. I might put some JB Weld around the bosses – they look very close to being undersized despite everything being pretty central.

[Dr_GMJNParticipant @dr_gmjn]

In other news, went to the Kelham Island museum this morning (it’s only 30 minutes from home). Parked next to a double flywheel similar to the one on the Twin Victoria. Never seen one before, it looks like it was part of some electrical machine judging by the circumferential details:

A few other engines:

And things in glass cases (always good):

And of course the 12,000hp River Don engine:

Bought myself a poster for the workshop:

Unfortunately it wasn’t running today due to a boiler issue. I’m always amazed it can go from full forward speed to full reverse speed in 2 seconds, without shutting the throttles. It’s one of those things where you can feel the power just by standing near to it when it’s working. Same awesomeness as a Typhoon display, or being on the pit wall at Silverstone when the old 3.5 litre V10 F1 cars were current.

Other random stuff:

Sheffield Simplex:

Cavity magnetron (with Sheffield made magnet!):

Anyway, a great museum, and it’s free (of course made a donation though).

[Dr_GMJNParticipant @dr_gmjn]

The back cylinder caps are domed, and this was a challenge. I took the advice I understood from the other thread (on machining domes believe it or not), and drew out the profile in CAD, then machined from a bar of cast iron:

I set the tool parallel to the bed:

And using more CAD:

Roughed the domes out:

Then using co-ordinates, approximated the profile:

Then using a combination of a dremel, files and abrasive paper:

Smoothed to shape:

Parted off using the home made rear post from earlier this year (worked great):

Then made a spacer ring and reversed in the chuck to turn and mill the inside details:

Took a few goes, but eventually I got a decent result:

The domes are primed; they’ll be painted blue eventually. I checked the height offsets with the height gauge, and they were identical to within half a thou believe it or not.

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