By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale Jan 24th

Stuart Twin Victoria (Princess Royal) Mill Engine

All Topics | Latest Posts

Search for:  in Thread Title in  
JasonB16/09/2021 06:53:04
avatar
Moderator
21435 forum posts
2448 photos
1 articles

That it, you don't need to change tooling once you start milling so can maintain the height setting.

Dr_GMJN16/09/2021 07:55:28
avatar
1225 forum posts

Thanks, Im not bothering a radiussed cutter for this: one part has a bit of a radius (may be sand residue) the other is a clean corner all round.

Im planning on using an 8mm or 10mm cutter, since I assume the extra stiffness will be beneficial over a 5 or 6mm one?

Dr_GMJN18/09/2021 22:00:21
avatar
1225 forum posts

Temporarily clamped the bosses to the castings, and drilled the 7BA clearance holes using the DROs:



Then tapped the stud holes:



Then fixed them using 7BA csk screws ready for machining, and centered the vice on the R/T:



Then, after much adjustment, centering and angle calculation, made a start on milling the profile while periodically moving in x, then rotation in z, at gradually increasing depts of cut. I tried to always move the table clockwise for this to reduce backlash errors:



Then re-centered on each end, using the vice stops, and rotated the table to give the radii:



Turned out OK for a first attempt:





Before and after:



Needs some flatting of the machining marks, despite using a constant z-setting for all the final cuts. Not a big deal in this case because they will be painted eventually, and so could be filled if they won’t flat out:



Now for the other one…

By the way, what is the best way to flat out machining marks like this? I’m sure I’ll get some in the valve chest cover recesses, and those won’t be painted, so I really want them smooth.

Thanks.

Edited By Dr_GMJN on 18/09/2021 22:01:00

JasonB19/09/2021 06:56:31
avatar
Moderator
21435 forum posts
2448 photos
1 articles

You could have taken a couple of cuts in Y while still set up for the main shape which would have got rid of most of those two "V" shapes you have either side before moving the part for the ends, maybe try that on the second.

Fine and then Emery paper backed by a file is the usual way in my workshop, also tend to paint any recesses covers just leaving the raised edge bright.

Shape looks good.

Edited By JasonB on 19/09/2021 06:57:14

Dr_GMJN19/09/2021 07:37:02
avatar
1225 forum posts

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_GMJN19/09/2021 07:47:40
avatar
1225 forum posts

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.

DiogenesII19/09/2021 09:07:12
308 forum posts
153 photos
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..

JasonB19/09/2021 10:10:42
avatar
Moderator
21435 forum posts
2448 photos
1 articles

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.

JasonB19/09/2021 10:17:17
avatar
Moderator
21435 forum posts
2448 photos
1 articles

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.

SillyOldDuffer19/09/2021 10:22:33
Moderator
7549 forum posts
1680 photos
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_GMJN19/09/2021 10:53:38
avatar
1225 forum posts

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**

JasonB19/09/2021 13:27:16
avatar
Moderator
21435 forum posts
2448 photos
1 articles

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_GMJN19/09/2021 14:29:16
avatar
1225 forum posts

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 Wilson19/09/2021 18:43:19
avatar
1194 forum posts
296 photos

Nice result Doc - a credit to your appoachyes

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

dscn4532.jpgdscn4516.jpg

 

dscn4568.jpg

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

Dr_GMJN19/09/2021 21:34:13
avatar
1225 forum posts

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_GMJN22/09/2021 22:03:37
avatar
1225 forum posts
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.

JasonB23/09/2021 06:55:37
avatar
Moderator
21435 forum posts
2448 photos
1 articles

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

Ramon Wilson23/09/2021 09:06:18
avatar
1194 forum posts
296 photos

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_GMJN23/09/2021 17:23:24
avatar
1225 forum posts

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 Wilson24/09/2021 12:34:26
avatar
1194 forum posts
296 photos

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

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Latest Forum Posts
Support Our Partners
Eccentric July 5 2018
cowells
JD Metals
walker midge
BOLDON
emcomachinetools
Warco
rapid Direct
Eccentric Engineering
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest