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Stuart Twin Victoria (Princess Royal) Mill Engine

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Dr_GMJN22/07/2021 22:10:56
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The 10BA bolts finally arrived, so I drilled and tapped the cylinder feet to suit:





I ground the tip off the tap to ensure the minimum hole depth. Time will tell if the holes will break into the cylinders…



They look pretty small for the job, but they are as per the instructions. TBH I think the JB Weld would have been fine on its own.

I’ll de-grease everything and fit the bolts permanently after coating with more JB Weld. Then it’s cylinder boring time.

Dr_GMJN25/07/2021 17:34:38
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JB Welded the screws into the cylinders this afternoon:



And began setting up for boring the cylinders:









And checking the travel - saddle will go left to right:





I’ve opted not to fly-cut the cylinder ends - I’ll do all four on a mandrel later on.

Can anyone see anything wrong with this, before I remove the centre plugs? I’m a bit concerned about it moving under load. I’ve put some paper under the top plate, but can’t do much with the other interfaces without adjusting the centre height. I suppose I should de-grease all the interfaces? I don’t want to use excessive clamp force in case I distort the bores.

Cheers.

JasonB25/07/2021 18:28:36
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Only thing I can see is that you look to have lined things up based on the pop marks in the wooden plugs. Are these true to your feed which have been fitted to the base and 5/8" up from the feet?

I also assume you are going to go with Ramon's suggestion of machining the cylinder ends on a mandrel, if not move the packing so you can flycut one end at the same setting as boring and that the piston rod end if facing the headstock.

Clamping should be fine.

Dr_GMJN25/07/2021 18:52:48
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Posted by JasonB on 25/07/2021 18:28:36:

Only thing I can see is that you look to have lined things up based on the pop marks in the wooden plugs. Are these true to your feed which have been fitted to the base and 5/8" up from the feet?

I also assume you are going to go with Ramon's suggestion of machining the cylinder ends on a mandrel, if not move the packing so you can flycut one end at the same setting as boring and that the piston rod end if facing the headstock.

Clamping should be fine.

Thanks Jason. Yes, as I mentioned after the last image, I’m going to machine the ends afterwards, on a mandrel - as per Ramon’s advice.

The feet were JB Welded to the cylinders with everything set up on the beds, on the mill. I was able to confirm the centres on the mill after clamping, so I’m confident the feet are very close to height and flat already. This seems to be confirmed by checking the lathe centres align with the plug centres, as per the first two images.

Did you mean true to “feed” or “feet”? You mentioned both.

If anything is out, it can’t be much more than 0.5mm from the marks in the plugs - I can’t detect any centering error visually.

Is there a way of double-checking overall longitudinal alignment? I’ll check the 5/8” height.

Cheers.

JasonB25/07/2021 19:01:30
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Feet. You could hold a straight edge against the ends of the feet and move the carriage along while a dti is held against the straight edge.

Dr_GMJN25/07/2021 19:17:38
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Posted by JasonB on 25/07/2021 19:01:30:

Feet. You could hold a straight edge against the ends of the feet and move the carriage along while a dti is held against the straight edge.

OK I’ll try that too.

The height from the shimmed flats (where the feet sit) to centre height is 3/4”. :



That’s also what it says on the drawing - unless I’ve misunderstood it, in which case I’m in real trouble now…

I’d assumed the 5/8” stepped seat faces of the feet to bore centre would be machined from the finished bore centreline as the datum (using the mandrel) - like the ends? I thought that was the previous advice to machine as much as possible from the finished axis?

JasonB25/07/2021 19:24:33
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Forgot you had not cut the notches

Dr_GMJN25/07/2021 19:28:45
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Posted by JasonB on 25/07/2021 19:24:33:

Forgot you had not cut the notches

No not yet.

Ramon Wilson26/07/2021 00:06:42
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Hi Doc, can't quite understand why you've drilled and tapped for the 10 ba screws after the feet were JB'd in place?

Set up for boring looks fine but I share your concern of it moving under load. I would if possible re think that clamping as it's never a good idea to rely on a single clamp.The action of tightening those bolts as you have it will tend to bend the clamp plate across the cylinder

You could consider making that top clamp a single one from one side and put two others on the feet on the other side. A thin slip of paper under those feet both sides will improve matters considerably. You have a lot of sliding surface potential so you need to be as sure as you can be before cutting commences as your first cut needs to get under the skin and as such will need to be a decent one.

Not popping in as much as I was due to C/L distraction but good to see progressyes

Hope that boring goes well.

Regards - Ramon

Edited By Ramon Wilson on 26/07/2021 00:08:13

Dr_GMJN26/07/2021 08:47:12
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Thanks Ramon, I’ll see if I can fit more clamps, or re-arrange, but there’s not much room there.

I assume the bolts are there as a mechanical backup if the Araldite (JB Weld) cracks? Therefore the order they are fitted isn’t that important. It says in the original instructions to clamp the feet to the cylinder, then drill, unclamp, then apply Araldite and final assemble. All I’ve done is added the JB Weld at the clamp stage. I figured that there would also be no gaps at the interface that could have made drilling a bit tricky, and that JB Weld would be way stronger than Araldite.

Ramon Wilson26/07/2021 22:22:17
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Hello Doc,

It's always best if a clamp can apply a single downwards pressure on a solid spot beneath rather than as you have it. One - it will be much firmer as it applies pressure to something solid and two - it wont tend to distort the casting - not so much an issue with a sturdy cast iron casting but especially important if it's gunmetal or aluminum. Several small clamps are always much more secure than one large one. Sometimes theres no choice but to use an unsupported surface as you have but there should always be reinforcements if possible.

My very first lesson on a one clamp set up, a Stuart Turner hand pump casting left the faceplate/angle plate set up as soon as the tool touched on. And when I say left - it went over my shoulder like a rocket narrowly missing my ear and the corner of the base actually embedding its self in the door surround. Yep - really!

If the JB 'cracks' or parts something would be seriously wrong with it! The bolts could have been there in the first instance to help locate the feet while the JB cured but will have little structural effect if fitted after curing takes place. Still they are there now and won't do any harm.

I try to use the JB as a structural 'part' of the finished item as opposed to using it purely as an 'adhesive' - a heavy chamfer around both curved edges of the cut outs would have allowed the JB to form an internal fillet as well as an external one with a much stronger end result for little extra effort.

Regards - Ramon

Dr_GMJN27/07/2021 00:21:41
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Thanks Ramon. TBH I’m struggling to find room to add clamps to the feet; the nut pockets are quite narrow. I’m thinking of drilling and tapping a steel plate to suit the feet, and screwing the feet directly to it. Then somehow clamp the place down. I’d still keep the top clamp.

The feet were bolted to their beds while the JB Weld set, and I checked the cylinder alignment once they were in place and clamped (using a pointer in the mill and the DROs), so alignment was pretty good by default. As suggested, the feet machining, cylinder ends and valve face etc will all be machined on a mandrel, so all critical dimensions should be spot-on to the turned cylinder axis. I double-checked the centre marks on the plugs were a best-fit to the o/d of the flanges (not perfectly concentric, then again they can’t be since the flanges are a bit oval), so I doubt I could do much more to get it right.

ETA I could remove the top clamp for the final fine cuts to eliminate any distortion I guess?

 

Edited By Dr_GMJN on 27/07/2021 00:31:44

Ramon Wilson27/07/2021 08:22:48
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Hi Doc,

Looking at your set up you could turn four short spacers of identical length to sit in the pockets and bridge them with a bar. A single clamp could then be set between the two existing clamp bolts. The pressure on the top plate could then be eased very slightly. The problem with the top plate as it is is that you have no idea if it is applying equal force across the valve face.

Having 'bought the tee shirt' on occasion with this kind of set up one is met with two distinct feelings - the first is that gut wrenching one where you think you may have just buggered the job followed immediately with the question to oneself why the hell didn't I put that extra clamp on. Biggest issue is having to reset the job accurately if you've half machined away your references.

I say this only as a note of caution - every op you do successfully is more to lose if having to restart.

All the best - Ramon

Dr_GMJN27/07/2021 08:37:14
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Thanks Ramon, I’ll have a look later, but I don’t think I’ve got enough T- slots to add finger clamps to both sides.

Clive Brown 127/07/2021 08:45:11
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Posted by Dr_GMJN on 27/07/2021 00:21:41:

ETA I could remove the top clamp for the final fine cuts to eliminate any distortion I guess?

Edited By Dr_GMJN on 27/07/2021 00:31:44

I think that's the last thing I'd want to do. Distortion of the CI casting will be insignificant and there's a chance of the set-up moving slightly.

Clive

Zan27/07/2021 09:03:04
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How about a short turned plug in the feet, then clamp each down with a long stud stud, clamp bar sat on packing

then add additional clamp bars to the same stud but longer bars going outside the lower clamps, so you now have 8 clamps using 4 studs There would be room in the centre for a strap clamp as well

it has the additional benefit of making the clamp positions wider on the casting thus removing the tendency of twisting

with regards to the feet fixings, I think it’s a mistake to tap the holes in the base. The wood plug cantering is very inaccurate and could easily be 10 thou out at each end, thus the bore is angled relative to your base fixings. The easy way is to spot through accurate fitting using plugs in the finished cylinder with reamed holes and a straight bit of silver steel as a pointer. Set this up on the bed, clamp in exact position then tap the base holes. You may find that to correctly align the cylinder ot will need some small rotation so the feet holes will need to be pulled over to allow this . I hope not

Edit…..perhaps you should rely on the position of the feet holes as you seem to have positioned these very accurately setting these parallel to the lathe axis, then just centering at the headstock end  

Edited By Zan on 27/07/2021 09:04:08

Edited By Zan on 27/07/2021 09:08:09

Zan27/07/2021 09:13:14
282 forum posts
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The problem with a strap clamp like yours is that all the down force could be on a single pimple point on the valve face, thus you only have in effect one clamping point with a very high force on it.  This makes them a bit of a problem compared to 4 clamps . Do be certain to use t bars not t nuts or there is a real risk of breaking the t slot in the cross slide, there wupill be considerable force on them

Edited By Zan on 27/07/2021 09:14:38

Dr_GMJN27/07/2021 09:21:21
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Posted by Zan on 27/07/2021 09:13:14:

The problem with a strap clamp like yours is that all the down force could be on a single pimple point on the valve face, thus you only have in effect one clamping point with a very high force on it. This makes them a bit of a problem compared to 4 clamps . Do be certain to use t bars not t nuts or there is a real risk of breaking the t slot in the cross slide, there wupill be considerable force on them

Edited By Zan on 27/07/2021 09:14:38

Thanks Zan, what's a T-Bar?

Zan27/07/2021 09:43:17
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Ah. Your beginner status shows again, but Iv been following your posts and your level of skill is impressive!

t bar, a very long t nut with tapped holes for the studs. Mine for the S7 are 4,2 and 1 inch long with holes tapped every .5” or so they spread the load and minimise the risk of damage. Also be careful the x slide is not bent when the clamps are tightened too much. I’ll provide a sketch of the clamping outlined above if you didn’t fully get it

JasonB27/07/2021 10:14:34
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I'm not sure why you are saying there are not enough tee slots. You could use the slots that the existing top clamp is held down by and easily fit 4 individual clamps with narrowed ends onto each foot pocket and support the other end with blocks.

vic clamping.jpg

 

The machining plate that the casting could be screwed down onto is another method I use quite often usually to hold the whole base of an open crank engine with as the sides of the plate also act as a good straight surface to clock with a DTI

 

On the other hand I would say many of these 2 x 1 Stuart cylinders have been machined with just a simple top clamp over the top as that is how Andrew Smith shows them being done in his books and the way I did my beam engine many moons ago and the bar was only 1/4" x 3/4" with a M6 stud either side. Even Tubal Cain uses little more than that in teh Princess Royal article, looks like a bit os 1 x 1 x 1/8" angle to mesmiley

 

Edited By JasonB on 27/07/2021 10:17:44

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