Stuart Twin Victoria (Princess Royal) Mill Engine

They don't do the heavy one now which just has a rectangular section rim, yours is a "T" shape with the six bosses.

The lugs want removing from both the outer faces anyway, so on one side you would just need to turn a crisper recess and then make a separate barring ring that could be JBWelded into place. If you do it right that will cover the screw heads and as it will be painted could be made from anything easy to cut or what about a 3D print?

I did something similar on this engine where the barring holes were central so made it up from 3 water jet cut parts. Worth looking through it all as it covers a fabricated beam engine.

That fabricated flywheel looks great.

I was wanting to try cutting the notches myself, possibly using a gear wheel because I don’t have a rotary table.

I could get an aluminium or mild steel ring laser-cut, JB weld it into the machined recess, and paint the whole lot. Then machine the notches out of the aluminium? I wanted to leave the notches bright.

In that case do it in steel

I suppose aluminium would look a bit bright.

Following this thread with interest as I have the Twin Vic kit and plan to make the Princess Royal with it at some point. I had not appreciated that the modern flywheels would cause a problem with the barring rack and no doubt would have come-a-cropper when I got to that point.

Doc - I have no idea as to how laser cutting services price their jobs - but if there is any significant economy in getting multiples cut - then I'd be happy to go halves with you on a pair when it comes to getting the ring cut.

Cheers

Dom

Dom, yes I’ll let you know.

About the only thing I’m fit for today, after the sledgehammer side effects of the Covid jab, is reading, so I’m going through the P.R. article again.

Re the flywheel, it says “Machine the face and the boss, line and line across..”

What does that mean?

Thanks.

Still puzzling over the connecting rods. It says to machine the rods down to 0.3” between the lines that mark the extents of the radiused transitions. Then switch to a tool with a 5/32” true radius, to form the transition radius as the middle diameter is reduced. But if you’ve just reduced the diameter between the extents with a step, how will the radiussed tool get rid of the step? You appear to be trying to form an internal radius where you’ve just put a corner, ie you need to add material.

The "lines are where the radius meets the taper so you are first turning to where the radiu starts and the second tool will then traverse further to the extent of the radius.

I'll have a look at the other bit.

J

PS I was like that on Friday after having mine on Thursday with what felt like the Flu.

Edited By JasonB on 28/03/2021 07:53:15

Line & line across looks like he just means face the hub back to the same plane that the side of the rim cleaned up to

Thanks Jason, that would make more sense, but it’s not what it says in the instructions. The dimensions in the drawing are to the edge of the radius on the rectangular bits, not the circular section rod. Those same dimensions are also in the text, where it says to initially machine down between them. If you follow the written instructions, I think the radius would crash into the first set of bolt holes for the strap.

It also says to mark the extents of the initial thinning with a felt-tip, but then once machined, to use a rule to find the extents of the rad. In that case why would you need a rule? It’s the same dimensions (there are no others), and you’ve just made a machined step to them, so it’s obvious where it is? There’s some error somewhere because you can’t use the same dimensions for both operations and end up with a smooth transition.

I think what he meant was to add on the tip radius to the distance from the ends (ie he shouldn’t have quoted the drawing values for that initial operation) and as you say machine initially to that. Then mark with a felt tip and extend as necessary. Why you’d need a felt tip for one job and a rule for the other is also confusing to me - surely you’d just mark the initial length, and the final length and work to those? For me, the instructions are almost too detailed in this case because they seem to suggest different marking techniques for the same simple job.

May well have misunderstood something, and I want to make sure I’m not scrapping a part because of this.

Yes there is something wrong with how it's written.

I would put a sharpie mark where I have put the pink lines on that image as they are easy to see while you rough out without the need to keep stopping and take measurements or have to scribe a deep line across the finished face of the ends. This will knock all the corners off and get you down to a round section.

Now that you have roughed out change tool and cut the tapers forming the fillets at the same time either measuring or setting a stop, usually a bit of both is needed as the curve of the tool will extend further along the deeper it gets into the work.

Yep, that all makes sense.

When I’m grinding the radiussed tool (planning on doing it on the linisher), are you supposed to harden it afterwards? Maybe dunk in water after grinding or something?
Presumably I can draw the profile on the tool and work to that, estimating the angles?

Is there a special file for sharpening tools, or is it a case of re-grinding when the cut isn’t as good?

New to all this - Thanks.

If you are grinding an HSS blank then it can be used as is. If grinding from gauge plate/silver steel then it will need hardening.

Tough up with a slip stone or more likely these days a small diamond lap if the edge goes off, this can be used on both materials

Ok Thanks.

I made a start on the boring bar, by drilling the centres. I used the vertical slide method, although it was quite tricky. I put the bar in the 3-jaw chuck, and then offered the vertical slide up, making sure the bar seated in one of the slots. Once everything was clamped up I checked the top surface and side with a dti, and it was quite a way off in terms of not being parallel with the bed. I couldn't really get it right to the dti, yet it slid in and out of the chuck quite freely.

Anyway, I figured that the most important thing was concentricity with the chuck right at the end, so I fixed the dti in the jaws and got both ends to within 0.001" all the way around:



Then undid all that good work by fly cutting the end!



Then re-did the centering (I need to learn to think the order of things through more carefully), and centre drilled:



When both ends were done, I put the bar between centres. Side to side, on the top and side edges, I'm getting pretty much no deflection of the dti, but about 0.004" when I turn it on its axis:



I don't suppose it matters too much, since the cutter will be rotating around whatever virtual axis it has at that point, and it won't be moving axially anyway?

I could really do with making a proper holder for the dti in a chuck for these concentricity measurements, not sure if there's a simple plan out there - or I could 3D print something.

Assuming the above is OK, the next job will be to mill a flat for the carrier, and a flat for the grub screw hole, and to make the cutter hole. Then I think that's about it.

BTW, for the boring operation, I was thinking of fitting my old 3-jaw chuck over the live centre, and using the jaws to contact the carrier (if it fits). I think it would save me messing about with bits of wire to stop it flapping about?

I’ve been looking at a couple of past threads on boring bars, and some seem to suggest a diagonal hole for the tool is better - presumably to increase stiffness.

Before I cross-drill it (with an adjustment grub screw), is the diagonal method worth it? Is it a case of setting the bar at some angle in the vice and slot drilling to begin with?

Thanks.

The angled designs tend to mount the tool at a specific angle so that a screw can be used to advance the tool by a set amount per turn.

Never bothered myself and find the 90deg hole makes for easier tool grinding so all my homemade one sate 90deg, though the Micro bore head does have it's own scale so you know how much the tool is advanced but don't use that much.

I’m making the bar at the moment - what is the purpose of locally turning it true? I can see that it’ll give a co-axial cylinder where the tool is, but a

I assumed you’d machine, measure and re-set the tool. I can’t figure out why you’d need a cylindrical portion of the bar?

Also, I think I’ve cut the bar too long. Presumably it should be the minimum length for the job plus a bit - but how far each side should the ‘plus a bit’ be?

Thanks.

As you will need to set the tool to desired radius plus half the bar diameter turning the area around the hole true ensured that the half diameter is actually half diameter not what half the bar is from the lathe axis.

I think mine have a length approx equal to the bar dia turned true equalised about the hole

Edited By JasonB on 05/04/2021 19:14:40