Stuart Twin Victoria (Princess Royal) Mill Engine

[Dr_GMJNParticipant @dr_gmjn]

[Dr_GMJNParticipant @dr_gmjn]

This will be my second model engineering project after the 10V:

https://www.model-engineer.co.uk/forums/postings.asp?th=161327

It's a model of a twin cylinder mill engine, based on the Stuart Models Twin Victoria:

Back in the mid '80's, "Tubal Cain" (Tom Walshaw) who was a prolific contributor to Model Engineer magazine, published a series of articles on how he modified and detailed the Stuart Twin Victoria. He called this version the "Princess Royal".

Refinements included a more realistic cylinder mounting method, re-designed connecting rods, incorporating scale bearings and caps, a working governor, a more refined ropewheel (flywheel), more relistic oilers and scale handrails.

The Stuart Models kit is very expensive, so after getting advice from the ME forum:

https://www.model-engineer.co.uk/forums/postings.asp?th=168605

I've opted to buy only the castings. I will fabricate the beds from aluminium, and make the rest from stock materials, which I've already got from a local supplier:

The BA fasteners I'll get from a specialist. I did buy the Twin Victoria plans, but I think most if not all the drawings for the Princess Royal version are in the ME Magazine articles:

The total saving doing it this way is around £250. It'll be a huge challenge for me – especially the governor.

Currently fettling the lathe and mill, so this one will probably get started properly after Christmas. Thanks all!

[Ramon WilsonParticipant @ramonwilson3]

That's a good start Doc – nothing like getting prepared. I'm doing the same thing but not quite in the same quantity. Looks like we will both be starting new projects around the same time. Good luck with yours

Hope you get your lathe and mill sorted out successfully

Regards – Ramon

[Dr_GMJNParticipant @dr_gmjn]

Posted by Ramon Wilson on 01/11/2020 22:57:51:

That's a good start Doc – nothing like getting prepared. I'm doing the same thing but not quite in the same quantity. Looks like we will both be starting new projects around the same time. Good luck with yours

Hope you get your lathe and mill sorted out successfully

Regards – Ramon

Thanks Ramon. I’m just finalising the CAD for the beds, with some input from Jason. I’ve got the materials and fasteners, so they will be the first bits to make. I’ll get castings after Christmas – things get expensive at this time of year: 2 birthdays, Christmas and car insurance due!

I just converted the ML7 to wide bed, and had to dress the front slideway to eliminate a couple of thou wear. It’s much smoother now – I can get full saddle travel without having to adjust the gibs half way! Just need to machine the other slides for bearings and re-settable dials. Using it should be a much nicer experience. Then to start on the mill and it’s issues…

[Dr_GMJNParticipant @dr_gmjn]

Re. the JB Weld epoxy for joints, and simulating casting fillets; there are a few types on Amazon, is this the correct stuff?

Thanks.

[JasonBModerator @jasonb]

That's the one, the "original formula" avoid the rapid or marine versions.

[Ramon WilsonParticipant @ramonwilson3]

Yes as Jason says that's the one Doc – just make sure you mix it really thoroughly and homogenise it well – just stirring it in to each other will provide a much weaker material.

As said before it can be quite runny especially where fillets are concerned. A drop of this ''stuff' mixed with it will thicken it considerably. I don't know for certain if that has a diminishing effect on it's tensile strength or it's temperature resistance but it certainly hasn't been an issue on my D10 (on steam).

Regards – Ramon

Jason – I'm having real problems staying logged in – yes I tick the box but it is very intermittant. Is there something else I need to do?

 

 

Edited By Ramon Wilson on 09/11/2020 13:10:45

[Dr_GMJNParticipant @dr_gmjn]

Thanks guys.

I've got a load of "Microballoons" for fibreglass model glider wings, but I guess that's the opposite of what I want as a thickener for this application…

[Ramon WilsonParticipant @ramonwilson3]

 

Doc, as you are aware microballoons are a filler – used them a lot mixed with F/G resin for fillets on C/L aerobatic model wing roots. The higher the loading in the mix the less JB you have. Definitely not the same as the silica. It's primary use is for making epoxy resins thixotropic. You don't use very much of it to get the effect of thickening. The 25 gm tub would last a lifetime

Ramon

 

Jason, if you are reading this, that's the fourth time I've had to log in today despite clicking the 'remember me' box -any thoughts?

Edited By Ramon Wilson on 09/11/2020 22:26:33

[JasonBModerator @jasonb]

Have you been looking in on another device such as a phone that may still have the forum "open" even if not on the active screen. That can sometimes be the problem

[DiogenesIIParticipant @diogenesii]

Ramon, if your browser is set to delete all cookies on exiting, that will also "close the forum door" each time, although you can probably exempt it in the browser settings..

[Ron LadenParticipant @ronladen17547]

Also worth noting that the original J-B Weld also machines well, I have milled, turned, drilled and even tapped it and it was fine, a very good metal filled epoxy.

[Dr_GMJNParticipant @dr_gmjn]

Posted by Ron Laden on 10/11/2020 07:54:58:

Also worth noting that the original J-B Weld also machines well, I have milled, turned, drilled and even tapped it and it was fine, a very good metal filled epoxy.

Thanks all.

[Dr_GMJNParticipant @dr_gmjn]

I’m wondering what the best way of machining the cylinder recesses in the feet strips is? I’ve got 12” of 1/2” square steel (as specified), but I can’t make out the machining method photos. Not sure if in fact he used square plate with a central hole.

I was thinking maybe somehow attaching each strip to a faceplate in the correct position, and turning the arc with a boring bar. Perhaps even do three or four at once, if they fit.

I want to machine them, not file them. Thanks.

[Ramon WilsonParticipant @ramonwilson3]

If you have a boring head for the mill you could use that after establishing the correct throw but clamping the individual parts against fixed stops on an angle plate bolted to the face plate will ensure uniformity. You may have to drill and tap some holes for the stops and may not want to but if they are positioned uniformly and the stops made to suit they can be used for all sorts of future set ups.

Edited By Ramon Wilson on 10/11/2020 21:59:04

[Dr_GMJNParticipant @dr_gmjn]

Thanks Ramon. Unfortunately I don’t have a boring head. Maybe I should get one from Arc – looks like they do R8 versions for the SX2P.

Any other way you can think to do it?

[Dominic BramleyParticipant @dominicbramley60728]

In the magazine I think he has soldered 3 strips of 1/2 inch bar together and then bored through them – so the outer two strips will have the correct profile.

[Ramon WilsonParticipant @ramonwilson3]

Boring heads are 'nice to have' when really needed but I find rarely used. The one I have for my Linley mill is a really cheap one but it does the business. The other, a more expensive one bought when I bought the Amadeal mill five years ago has never been used.

There are several ways you can machine these parts – you could use a rotary table of course as another option but personally I would use the lathe and angle plate set up. You can use the model bolt holes for holding the parts to a simple fixture fixed to the angle plate – once you have established the centre of the radius you can either rough all four to with say ten thou then return them and finish them all at the same setting or complete each one separately. Given that these radii won't need to be 'accurate' to any degree probably the latter is the better way to proceed. The former though would bring them close to being identical with more certainty.

This is one part where you will see how cold rolled steel reacts to large cuts on one side!

Ramon

PS the method as has just been described is yet another option!

Edited By Ramon Wilson on 10/11/2020 22:45:44

[Dr_GMJNParticipant @dr_gmjn]

Posted by Dominic Bramley on 10/11/2020 22:33:09:

In the magazine I think he has soldered 3 strips of 1/2 inch bar together and then bored through them – so the outer two strips will have the correct profile.

Right. I’ve not got the drawings to hand, but does that give the correct offset by default?

Thanks.

[Dr_GMJNParticipant @dr_gmjn]

Posted by Ramon Wilson on 10/11/2020 22:44:04:

Boring heads are 'nice to have' when really needed but I find rarely used. The one I have for my Linley mill is a really cheap one but it does the business. The other, a more expensive one bought when I bought the Amadeal mill five years ago has never been used.

There are several ways you can machine these parts – you could use a rotary table of course as another option but personally I would use the lathe and angle plate set up. You can use the model bolt holes for holding the parts to a simple fixture fixed to the angle plate – once you have established the centre of the radius you can either rough all four to with say ten thou then return them and finish them all at the same setting or complete each one separately. Given that these radii won't need to be 'accurate' to any degree probably the latter is the better way to proceed. The former though would bring them close to being identical with more certainty.

This is one part where you will see how cold rolled steel reacts to large cuts on one side!

Ramon

PS the method as has just been described is yet another option!

Edited By Ramon Wilson on 10/11/2020 22:45:44

OK understood. I don’t have a rotary table either!

I do have an angle plate though. I was only thinking the other day that it’s the one thing in the tooling cabinet that Ive not used yet…

[JasonBModerator @jasonb]

By soldering 3 pieces of the 1/2" square stock together that will give you a distance from ctr of hole to "bottom" of the outer two pieces of 3/4" which is the required distance. Note that you may not quite have 0.500" stock but the 1/2" is not the critical size its ctr line to the notch that sits on the frame that matters. This notch would be best machined after JBWelding it together as you can't be accurate glueing to the cast surface.

Another option would be to do them on the cross slide with a between ctrs boring bar, a simple block to bring the blank to height and screw them to would make it fairly simple but I think the soldered method will be quicker.

 

Edited By JasonB on 11/11/2020 07:49:00

[Dr_GMJNParticipant @dr_gmjn]

Posted by JasonB on 11/11/2020 07:05:00:

By soldering 3 pieces of the 1/2" square stock together that will give you a distance from ctr of hole to "bottom" of the outer two pieces of 3/4" which is the required distance. Note that you may not quite have 0.500" stock but the 1/2" is not the critical size its ctr line to the notch that sits on the frame that matters. This notch would be best machined after JBWelding it together as you can't be accurate glueing to the cast surface.

Another option would be to do them on the cross slide with a between ctrs boring bar, a simple block to bring the blank to height and screw them to would make it fairly simple but I think the soldered method will be quicker.

Edited By JasonB on 11/11/2020 07:49:00

Thanks Jason. Silver solder? If so I’ll need to get some (and a new gas bottle).

What is a good between centres boring bar to get? I might need one for the cylinders.

[Ramon WilsonParticipant @ramonwilson3]

A simple pin set on centre line of the arc and another in the cylinder wall will locate the feet accurately enough while the JB sets, though I was underr the impression the mating area was going to be machined too.

Yes another way this op can be done, but as Jason says it would be best to machine the lower surfaces after bonding – done with the cylinder held on a mandrel the dimension would be both identical over both parts and importantly parallel with the cylinder bore too

You can make a simple 'tween centres boring bar of any size you want to suit the job. I have some made many years back from silver steel. They have a small flat on them where the cross hole for the 1/4 HSS cutter goes. By making the hole blind the flat area can be drilled and tapped for say a 6ba screw which helps move the cutter when very small movements are required. Remove screw, mic across flat and tool tip – simple maths gives the radius. There are other ways – inset adjustable carbide tips for instance but that above has served me well for a long time now – I much prefer to use 'between' centres for bores to eliminate taper.

Soft solder will be sufficient!

 

Ramon

This pic should help explain it better. The turned portion is to ensure the diameter is true to the axis of the centres.  Radius required is dimension plus .462 across tool tip and flat

Edited By Ramon Wilson on 11/11/2020 08:52:42

[JasonBModerator @jasonb]

Yes just soft solder them together for machining.

As Ramon says a between ctrs bar is easy to make, mine are not even solver steel.

[Dr_GMJNParticipant @dr_gmjn]

Thanks guys.

The setting up of the cylinder and feet is a challenge. I'll have to re-read the article. The plane of the feet faces has to be parallel to the nominal cylinder axis, and the valve face at the top, and they have to be aligned laterally with the cylinder axis. Also, so that when the cylinder is bored, and the valve face and feet are finally machined, they are the same thicknesses, and the cylinder walls are consistent.

I suppose the boring would be done last, resting on the finished feet. Then the valve face would be machined in the same way, parallel to the feet?

It's not so easy. I can imagine getting everything done nicely, then finding the cylinder is offset in the casting. I suppose the final boring could be done to the best-fit in the cylinder casting, but then the cross-slides would have to be adjusted to suit. That sounds all sorts of wrong.

[Author]

Posts