Stuart Twin Victoria (Princess Royal) Mill Engine

I got a length of 1" diameter steel bar stock to make the between centres boring bar. I obviously need to face and centre drill each end, but I don't have a fixed steady (I do have a Myford travelling steady). Is there an alternative method? I assume with a fixed steady, I could set the bar in the chuck, run the fixed steady up to it and adjust, then slide it along to the end of the bar and face and drill as normal?

Any other methods, or is it £100 on a fixed steady?

Thanks.

Well a fixed steady is a good accessory to have - when you need it - which from my perspective isn't that often.

You can jury rig it with a decent thick piece of ply wood bored to a good fit on the bar. Clamp or bolt the plywood to an angle plate and then to the cross slide and set as you describe. Not ideal but it would just about get you by for drilling two centre holes - and save you a hundred quid

Perhaps others may have other suggestions but If I only had to do two holes that's how I'd tackle it

Good luck

Clamp to cross slide with packing or to the Vertical slide of you have one. Flycut the end. Put DTI in lathe chuck and adjust bar's position until dti shows it's true and ctr drill with drill in spindle. I have used the wooden block method Ramon mentions in the past when I did not have a fixed steady for the Emco

Strictly speaking the holes do not need to be spot on but it's handy for measuring tool projection though that can be got around by turning down a section around the toolbit hole to a known diameter

Is a 1" bar going to be of use on your cylinders as it won't fit!. 3/4" would allow it to pass through the core (I think) and allow room for a few cuts & swarf

Edited By JasonB on 08/03/2021 13:31:20

I am just doing the cylinders on my Twin Victoria, my first steam engine project, and I wonder how deep the 7BA tapping holes should be. I don’t want to drill through into some thing vital! Especially in the cylinder face of the steam chest.

Any advice gratefully received!

Andries

I drilled them about 6mm deep which should be plenty of thread engagement without having to bother with a plug tap, I was using a spiral flute one. End flanges nearer 4.5-5mm if you don't want to see them break through the back of the flange but not an issue if clading. The hole that comes closest to doing some damage is the 3/16" exhaust one.

It says in the Princess Royal write-up that breaking through from the feet fixing drillings into the cylinder, is likely, but not much of an issue if you do. I suppose if the holes are small and there are no burrs, it's all sealed anyway.

Having said that, I wonder if the feet holes are orientated such that they would miss the piston packing rings though? If the packing goes over a hole it might damage it.

Sorry, I meant 3/4":



I was going to reduce it in diameter a bit: a) to get some practice in machining between centres - I've not really done it before, and b) to give a bit more clearance for swarf:



It would also be a good check of my tailstock alignment I suppose.

Think I would tend to keep it as solid as possible.

Thanks guys. My first cylinder end was about 4.5, so I will continue with that throughout. Is there some formula which gives a ratio of depth to thread diameter, ie twice or three times depth?

Just looking at the beds again, and the cylinders. This might seem trivial, but:

The drain cocks and operating mechanism don't seem to be defined too well in the article. Which drain cocks are good for this application? The ones I used on the 10V are pretty stiff, and the handle shape wouldn't lend itself to being drilled for linkages.

Reason I ask at this stage is I'd like to do all the drilling of the beds while they're square, rather than drilling on the draw angle later. If an operating spindle or rod needs a hole, and a boss, I'd like to plan for it now.

Ramon - I notice you've got a nicely engineered system - but I can't see which drain cocks you used. Could you elaborate please?

The straight ones that most of the other ME suppliers sell come with a flat lever that is drilled with a few holes so easily linked together and they also have a pipe union on the other end. The alternative would be to plumb the two drain holes into one 1/4 turn valve either centrally mounted under cylinder or hidden in the base

I know nothing about this engine but looking at the cylinder couldn't that be set up in a 4 jaw with spacers to clear the end flanges if needed and then bored with a standard boring bar.

I am probably missing something

I think you can, but the boring bar would have to be quite long, and the one I've got would be getting a bit flexible at that extension.

Plus its another technique for me to have a go at.

I've a ton of pictures I took whilst building my Victoria. I took it quite away beyond the 'kit' Stuart supplied in the end.

Most are here in the blog I ran at the time:

Victoria BLog  First Page

Some the posts on this site too - ME Forum Post

I did mean to serialise all of this for Model Engineer, but never got round to it.

 

Steve

I met a guy way back, he had built the Stuart Twin Victoria as a clockwinder for a client...

Edited By Steve Withnell on 09/03/2021 14:43:22

Edited By Steve Withnell on 09/03/2021 14:44:09

Edited By Steve Withnell on 09/03/2021 14:48:38

Edited By Steve Withnell on 09/03/2021 14:58:15

Thanks - really nice and runs beautifully.

I need to get some additional reamers - 1/4", 7/16" and 3/8". I can get them from ARC (as hand reamers) no problem, just wondering if there are any benefits or disadvantages to getting imperial/metric equivalents in terms of availability of the bar that ultimately goes through the holes? I thought I read somewhere that some were unavailable.#

The 3/8" hole isn't a running fit, I think its for the crank webs, that require spigots machining to fit on the crankshaft. I might be better boring these holes - assuming my boring bar will fit?

Thanks.

I'd bore the bearings and crank that way you can fine tune the fit, For example you want the flywheel bore a slightly tighter fit than the bearings so unless you are going to invest in 0.001" increment reamers you won't get it with a single nominal size one. 1/4" is easier done with a reamer.

As for metric/imperial it really depends on what you are thinking of making in the future, imperial designs are often best done with imperial stock.

I think it said that the bearings were best reamed, to get a perfectly matched centre height from the mounting face (or something like that). I don't think the flywheel is specified as reamed, so that's ok.

On the subject of the flywheels, the use of a double key, one of them stepped, and the riveted together rims seems pretty elaborate. Couldn't just one key be used, and the rims screwed together with CSK screws, and the slots filled? It's all machined flush in the end anyway. Presumably the key configuration is to replicate the real thing, but I cant figure out why you'd use rivets rather than screws, especially since the rims are Araldited together anyway, so it's not like they're going to move relative to each other.

With a chance that the drill could wander and the reamer just follow the drilled hole I would say there is more risk of different heights when reaming, Boring will true up any wayward drilled holes and provided you have the bottom of the casting against a fixed stop like the vice's fixed jaw then heights should come out the same.

Double tapered keys will be less likely to "tilt" the flywheel to one side which can happen with a single key if the flywheel is a bit loose on the shaft, stepped key is only if things don't line up.

From your photos it looks like you have the "lightweight" flywheels so will have to go about the joining slightly differently and if you want the barring ring than that will have to be added as a separate piece. The reason rivits are suggested is that they also expand in thickness when peined over so will ensure there is no movement unlike a screw with a bit too much clearance that can fret.

I would forget the Araldite on any part of the model, we now have JB Weld which will do a better job and if you put some into the holes during assembly then screws can be used, I would probably do with M3 cap heads into counterbored holes which can then be filled. Also measure OD of the screws and use a close fitting drill for the clearance holes eg 2.8mm or 2.9mm as they are often undersize.

Hmm I didn’t realise there were different types of flywheel.

Id really like to incorporate the barring notches - how do you suggest do it?

Thanks.