Stuart Twin Victoria (Princess Royal) Mill Engine

[JasonBModerator @jasonb]

Seems like a 3D printed ring that is shaped to fit around the handwheel hub/spokes and with graduations around it would be the way to go, what is the pitch of the screw?

[WearyParticipant @weary]

Re: Tailstock DRO.

If you don’t want to make your own, nor create a suitable handwheel maybe have a look at ebay item No. 354373217838 ?

I have a similar item (different lathe) and have found it useful.  It needs no ‘fixings’ and can be easily removed when not required.

Phil.

[Dr_GMJNParticipant @dr_gmjn]

Thanks Phil, mines’s an ML7, so that wouldn’t fit. Looks as neat as it’s probably going to get, but not sure I’d trust magnets to hold it.

I might end up with something similar, but D&T a couple of holes to secure the fixed collar.

[Dr_GMJNParticipant @dr_gmjn]

A quick measurement seems to indicate the pitch is 1/8”.

[JasonBModerator @jasonb]

I suppose a 125 division scale would have to do. Mine is 10tpi so an easier to keep track of 100 divisions. Also got crisp 1mm divs on the barrel which are Ok for drilling when accuracy is not quite so critical.

[Martin ConnellyParticipant @martinconnelly55370]

So far I have not had to do better than set the barrel to a clear extension point on the scale then lock the tailstock in the start position (my tailstock has a window and a clear line for the scale to match up to and a 1/8″ pitch) and then estimate the tailstock handle in 1/8 rotations from the starting point which is horizontal. This is close to the nearest 1/64″ in depth. So, for example, 1 full rotation plus 1/8 rotation would give me 9/64″.

If I need better I can use a set point on the tailstock scale as the target depth, set the tailstock up to the start point on the part you are working on, wind the barrel in a bit then use an indicator to move the tailstock towards the part by the required depth then lock it in position. Then when you wind the barrel out to the set point on the barrel scale you are at the correct depth. Note that often this requires a small start on the machining of the part to be able to set the start point correctly.

Martin C

[Dr_GMJNParticipant @dr_gmjn]

So what with the warmer weather, I’ve re-entered the garage again. I’m keen to get on with another big step (for me) which is the flywheel and fitting it to the crankshaft:

There was some discussion about tapered keys a while ago, and I’m still not sure how to go about it, but first things first:

I think Jason mentioned that the flywheels I’ve got are not the right ones, so need some fettling. I can’t remember the details, and I can’t seem to skip to a specific thread page, but from memory:

1) The blocks at the end of the spokes need grinding away, so I guess that would be the first step, along with cleaning everything up with wire brush and file.

Then, with reference to the instruction article:

2) Mount on a faceplate, trueing the iside of the rim (such that it doesn’t look eccentric when spun I guess). I might get away with mounting directly to the faceplate at this point, since there is a bit of an overlap:

3) Turn the O/D to clean-up.

4) Face the edge of the rim

5) Face the hub (which is offset outwards)

6) Turn the O/D of the hub to where the spoke radii meet it (probably use a button tool for this so it blends out into the casting a bit better?)

7) Centre drill and bore the hub to about 8.7 mm.

8) Repeat 2) to 7) for the other flywheel.

9) Re-set on the faceplate the opposite way.

10) Face across checking that the boss is slightly recessed (1/2 – 1 thou).

11) Bore or drill the recess in the hub.

12) Repeat for the other casting.

13) Drill each rim for rivets (I think I’ll use screws, so a clearance hole in one, and a tapped hole in the other. Maybe use counterbore and capheads, subsequently filled with JB Weld?

14) JB Weld and screw the two wheels together – possibly using a turned axle to align them?

15) Leave for a few days to set and de-stress.

I’ll leave it at that for now.

I think I’ll draw out the rims, because one face needs the barring slots, which it was suggested were laser-cut into a plate, and subsequently glued into a turned recess. This is fine, but I also need to machine in the slight recesses immediately under the rim, and machine the face where the rivets (screws) will fit. This face along with the filled holes for the screws will eventually be painted, leaving the the outer recess a machined finish. There isn’t much room for all this so I have to make sure it looks right.

As ever, any advice very welcome. Thanks.

 

 

 

[JasonBModerator @jasonb]

I think you have the right flywheels as you want the ones with the blocks at the end of the spokes for joining the two together. Fettle first and then I just turn them off where they are not needed which will be on the outer edges of the “pair” of flywheels.

If you have the correct size 4-jaw then it is easier to use that by reversing the jaws and there is just enough room to grip by the inner face of the rim. This also saves having to fiddle about with packing under the spokes, clamping plates etc.

As you say tap one side and then counterbored holes for cap heads on the other, M3 would do or M4 if you can get the heads in.

Only drill a small pilot hole at this stage so you can locate ctr and use a pin to line things up during drilling and assembly. Then open out and finish bore when they are one unit.

Resin printed barring ring may now be an option as it gets painted, could even be done in segments.

[Dr_GMJNParticipant @dr_gmjn]

Thanks Jason, I’m drawing something up now which shows the proportions. Here it is so far:

I’d like to mill the barring slots using the R/T if possible – seems it might be quite satisfying (if it goes well!). I might be able to get away with milling them into the casting, then again they may look too far towards the rim. Should the radius where the slots are, be machined away locally to give a “square” pocket I wonder rather than the asymmetric pocket shown in the section above?

The tappings are for M3 capheads – the head O/D counterbore just about fits within the un-machined bit of the casting, and remains on the pads on the inside. I might change it to blind drill and tap the opposite side to save filling and flatting the exposed external holes.

The keyways are at 120 degrees to each other. Since the hub is hollow in the middle, I guess the amount of material to be removed is minimised. I think a 3 mm width of key might be fine, and use a broach. I think a parallel, not tapered keyway, secured with a screw would be OK on reflection? Not sure about the maximum length the broach can take, I think it’s 22 mm on the Arc Euro specs, but the hub is 44.5 mm, so that might need more thought. I’m assuming a simple extension bar would just push the broach through whatever length is needed though?

Thanks.

[JasonBModerator @jasonb]

There is not much to loose by cutting directly into the flywheel, if it goes wrong then you can just turn a recess and inset a separate ring.

As shown in the section will be OK. However I’m not keen on the semicircular shape so would come in sfrom the side and cut say 1mm  (0.040″) closer to the rim. TC talks about plunge cutting but he also mentions moving sideways so that would give a short slot rather than just a half circle. You could 3D print a small section and see what looks best.

You will need to make your own bush for the broach to get the required length to support it throughout the cut. Simple top hat shaped bit of turning and then mill two slots at 120deg. ARC do (did) sell extensions but any bit of bar that will fit down the keyway to allow you to push it right through will do, I have just used short lengths of 3mm round mild steel bar.

[Dr_GMJNParticipant @dr_gmjn]

Thanks Jason, I’ll re-draw the barring slots. I’ve had a look at some full-size flywheel images, and there are some that show the barring slots quite close to the edge of the rim.

Re. The central hole. Wouldn’t this be better bored rather than drilled? I’m concerned a small drill might wander (had this before), and cause mis-alignment when joining. Also the middle will need boring anyway – before fixing the two wheels together – to form the central pocket in the hub. My small boring bar will do about 8.5 diameter minimum IIRC. I assume that so long as the initial bore is less than the final size by a few mm, It would be easier to align (for joining) with a more substantial pin?

I want to keep the biggest diameter on the wheel that I can, to give the final rim some depth, so ideally I don’t want to take much off the o/d faces (to remove any radial mis-match) once the two wheels are joined.

[JasonBModerator @jasonb]

As I said earlier

Only drill a small pilot hole at this stage so you can locate ctr and use a pin to line things up during drilling and assembly. Then open out and finish bore when they are one unit.

6 or 8mm pilot will be fine then drill out to say 10mm once assembled and then change to the boring bar. The cavity can just be drilled to size before assembly as it is not critical and won’t touch the crankshaft.

I always try and keep a flywheel casting as big as possible too.

[Dr_GMJNParticipant @dr_gmjn]

<p style=”text-align: left;”>Understood, but I assumed that for best accuracy, boring would be better than drilling, and therefore would minimise any radial mis-match at the rim. I remember from past advice here and on the 10V, boring was often recommended over drilling.

</p>
If drilling 8mm will be accurate enough too, then of course it’s not a problem.  I suppose by the time the void is bored out, the effect of any wander is minimised so long as each wheel is drilled from what will become the outside face of the hub.

I think the crsnkshaft itself was finished about 14mm, but I’ll check later on.

[JasonBModerator @jasonb]

I suppose there is a slight chance any wander could affect a pin used during assembly so bore it out to 9 or 10mm.

[Dr_GMJNParticipant @dr_gmjn]

Just to be clear, when you say ‘pin’, that is a short dummy axle to temporarily align the flywheel halves?

(not sure why the text in my posts is annotated with stuff when I reply using my phone).

[Dr_GMJN]

On Dr_GMJN Said:

(not sure why the text in my posts is annotated with stuff when I reply using my phone).

Presumably because you are using the formatting features of the ‘phone instead of the ones on the menu ‘ribbon’

It looks fine when you are composing, but reverts to displaying  html code when you submit the post.

MichaelG.

[Michael Gilligan]

On Michael Gilligan Said:

On Dr_GMJN Said:

(not sure why the text in my posts is annotated with stuff when I reply using my phone).

Presumably because you are using the formatting features of the ‘phone instead of the ones on the menu ‘ribbon’

It looks fine when you are composing, but reverts to displaying  html code when you submit the post.

MichaelG.

I’m not using any formatting on my phone apart from Space, and Enter, as far as I’m aware.

[Michael GilliganParticipant @michaelgilligan61133]

Sorry, I’m lost then …

MichaelG.

<p style=”text-align: left;”>

</p>

starts and ends the formatting of a paragraph

[JasonBModerator @jasonb]

Yes just a piece of stock to line things up during assembly.

Reply from my Android phone

[Dr_GMJNParticipant @dr_gmjn]

I made a start this week cleaning up the castings, but some of the scale that appeared after heat treating them in the fire is pretty robust. I probably wouldn’t try that again if I’m honest. I wonder if shot-blasting would get me back to a decent finish?

Anyway, fitting to the 4-jaw chuck is quite a challenge. The clearance to the ways on the ML7 is marginal:

It’s not helped by the corners of two of the jaws interfering with the spokes:

Is there a “trick” to getting the wheel both centred and true? I’m happy with centering turned work using a DTI, and can adjust those types of parts pretty quickly and accurately with the method I use, but with a rough casting like this, and also trying to get it in true – it’s not so easy. I want to get the inner rim and hub true – with preference to the inner rim; it always looks bad when there’s eccentricity there when its spinning, even if the OD is perfect.

I’m about to order a 3mm broach from Arc. I guess there’s no point buying a shim, since it won’t be long enough for the extended boss I’ll need to make. How should I calculate the height of the keyway from the opposite side of the boss diameter? Clearly it’s not a standard size. The nominal depth of the tapered key in the plans appears to be 1/8″ (c. 3mm). On the drawings I posted previously, I’ve made the top of the keyway 1.5mm above the boss diameter, which sounds tiny, but looks about right, and puts the shear plane half way up the key. In terms of possibly making a shim, what’s the maximum first-pass (and subsequent) depth of cut for a broach like this?

Thanks.

[JasonBModerator @jasonb]

Just put something blunt in the toolpost like the back end of a cutter or blunt end of a pencil. Turn the flywheel round by hand and look at the gap between it and the blunt end and tap the flywheel to even things out. A flywheel may be pringle shaped so you will just have to use best judgement.

When I make broach bushes I measure from th efirst tooth to the back of the broach and make that the depth of my slot.

0.8mm for the shim, though it won’t hurt if you use a bit more.

If you said the keyway was roughly half the broach width then that is total 1.5mm cut so single pass about 0.75mm which ties in with the shim being approx half.

[Dr_GMJNParticipant @dr_gmjn]

I’ve not been able to order a broach yet – Arc Euro won’t let me sign-in, and there appears to be no way of getting a new password. I’ll give them a call on Tuesday I guess.

Looking at the hub – I’m a bit concerned that once cleaned-up, the wall thickness where the keys are will be quite thin. I’m not sure what the height of the keyway would be with no shim. I’m thinking I could mill the broach bush to give a shallower hub keyway height, and compensate by having a deeper keyway in the shaft (this has come about becasue the stepped shaft has ended up thicker than the plan – 14mm diameter rather than 11mm). If I do that I might not need a shim at all?

As drawn, the head of the tapered key (about 7mm high) would project above the turned hub by about 2.75mm. I guess this would look wrong, so I might have to reduce it by this amount?

 

[JasonBModerator @jasonb]

As you are using two keys I should think you could go 1mm deep rather than 1.5 so that would leave you 3mm of hub thickness above the keys. go with a thinner shim.

I usually make the hea dof a key twice it’s height so if you reduce to 1mm in the hub then that is 2.5mm key so a 5mm head which will come just inside the hub.

[Dr_GMJNParticipant @dr_gmjn]

Thanks Jason, that would do it.

I managed to true one of the wheels in the lathe. It’s right on the edge of fitting, but once skimmed on the rim and face it should be easier to re-fit. I’ve not managed to get rid of the scale yet – I think it would be best to do that first rather than risk damaging a machined wheel. I’m considering using Milliput to smooth the worst of it out.

I expect that these days JB Weld would replace Araldite for sticking the wheels together. Would this cause issues with discolouration along the peak between the middle rope grooves?

[JasonBModerator @jasonb]

Grinding bit in a Dremel would smooth the casting or brick acid is good for getting scale off steel so should work on CI.

Yes I’d use JBW these days

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