Stuart Twin Victoria (Princess Royal) Mill Engine

[JasonB]

On JasonB Said:

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

Tried the Dremel a couple of days ago, with grinding bits and the abrasive cylinders, but it didn’t touch the scale. It’s like very hard glass. I’ll get some acid and try that.

[JasonBModerator @jasonb]

Let me just check it won’t attack the iron, will put some in this morning and report back.

[JasonB]

On JasonB Said:

Let me just check it won’t attack the iron, will put some in this morning and report back.

Thanks Jason, I can get some from Screwfix down the road if it’s suitable.

[JasonBModerator @jasonb]

While it ddd not attack the CI sample it did seem “damp” which I assume is some of the acid soaking into the porus iron. So probably not the best idea as the acid may come back to haunt you in the form of rust. It also did not attack the paint that was on one face of the sample.

[JasonBModerator @jasonb]

While it did not attack the CI sample it did seem “damp” which I assume is some of the acid soaking into the porus iron. So probably not the best idea as the acid may come back to haunt you in the form of rust. It also did not attack the paint that was on one face of the sample.

[JasonB]

On JasonB Said:

While it did not attack the CI sample it did seem “damp” which I assume is some of the acid soaking into the porus iron. So probably not the best idea as the acid may come back to haunt you in the form of rust. It also did not attack the paint that was on one face of the sample.

Ok thanks for that. I’ll continue with chipping it away and filling the rest.

[Dr_GMJNParticipant @dr_gmjn]

I got the broach. It came with a small shim, but I assume that any shim would need to be at least as long as the bush/hub for it to work properly?

Also, when setting up in the press, is it a good idea to angle the work slightly so that the ram is always pressing the broach towards the bush? I think it was Ramon who mentioned that a broach could climb into the work and cause issues.

 

[JasonBModerator @jasonb]

Yes you would want to make a longer shim so the broach is supported through the whole length of the hub.

I’ve always done it vertically.

[Dr_GMJNParticipant @dr_gmjn]

Continued with de-scaling the wheels. I’ve run out of grinding bits for the Dremel, so have had to pause until new ones arrive next week.

Gave me chance to consider the barring slots again – I think they will have to be a separate insert after all to to space constraints at the rim. I think I could possibly get away from laser-cutting by turning an insert from mild steel – or mill a ring using the R/T, then fit it with JB Weld, then cut the slots. I suppose the insert would have to be perhaps 1 mm or so deeper than the slot depth to keep everything looking like a one-piece casting. Ideally I’d paint it final colour before milling the slots to save a load of masking. I like the look of plain metal on the machined slots.

[Dr_GMJNParticipant @dr_gmjn]

Slightly waylaid with kidney stone treatment last week (deep joy) but back to the flywheel:

I was having trouble centering them in the 4-jaw chuck, because the position of the edge of the inner rim (which I was centrering to) I found difficult to judge, and of course using a dti is impossible becasue of a) the cast surface, and b) the spokes are in the way. I printed a stepped ring that was a fit on the inner rim in six places (radially and axially), and was offest a bit. This gave me two ‘best fit’ faces to true to:

I could get it to 0.010″ radial and 0.006″ axial, which I thought was OK. Running it up in the lathe seemed to confirm all was well.

The o/d cleaned up easily enough:

As did the central boss:

I used a button tool to try and blend the machined bits to the cast bits to eliminate any visual wobble there. This sort of worked, but I’m still left with the imperfections in the casting, especially where I removed the square pads:

I wondered wheter to just feed the button tool in all the way and machine the radius, then paint it, but then again I thought why not wait and just use Milliput after everything is done. It is after all only on one side – the other will be machined for the barring ring. The opposite side will need Milliput to fill the caphead counterbores anyway, so it wouldn’t be such a big deal to do the whole circumference.

I drilled the central hole up to 10mm:

Then used a 10mm end mill in the hope of being able to get a more accurate diameter on both wheels, Unfortunately I’d not accounted for the step at the shank end of the mill, so it wouldn’t go all the way through. I ended up boring it slightly over 10mm:

I suppose now before setting-up the second wheel, I should turn a spigot to fit this bore, and then bore the second wheel to suit?

I’m wondering whether if I turn said spigot between centres, I can use it to subsequently centre the pair of wheels on the faceplate before clamping the spokes for final machining? I could then remove the spigot and finally bore the boss to 14mm diameter for the crankshaft. Seems like it would be easier than tapping it with a hammer to get it true?

This is the current situation. Needs 0.9 mm removing from the joint face to get the overall width right. Not checked the boss protrusion yet, but it looks approximately ok:

What is the best way of smoothing the cast surfaces? I’ve been using Dremel tungsten burrs and grinding bits, but they are a bit harsh and don’t give good control. The sanding barrels would be OK, but hardly touch the surface before becoming smooth or disintegrating.

Anyway, I’m still hoping to be able to get the wheels stuck together by the end of the bank holiday, and I’ll worry about surface finish later.

Thanks.

[JasonBModerator @jasonb]

Yes turn your pin to fit the first wheel before starting the second.

I would still clock the rim when it comes to doing the pair, Unless your pin sticks out a long way and is a perfect fit 1thou of reading at the hub could be 7thou at the rim.

 

I only tend to use burrs on very hard castings, the grinding bits work for me and as you say the sanding drums and spiral wraps wear as they are not really for removing that much metal maybe just final touching up. These are the ones I use most of the time.

From the last photo it does not look like much more is needed, they are after all cast surfaces not machined ones you are replicating.

I think this was the last Stuart Flywheel I did, you can see the “flats left where I have used a tool with approx a 1.5mm radius on the end to clean up the insid eof the rim at the same time cutting away the bosses. This was finish bored on th efirst setup

Then to do the other side I clocked the previously machined face & side of the rim.

After machining out with the Dremel to tidy the slokes and blend in the “flats”

Some high build primer and paint and thats it

[Dr_GMJNParticipant @dr_gmjn]

Thanks Jason. I was going to mount on a faceplate to do the other side (as per article), but might as well do it in the chuck; I keep forgetting he didn’t use a chuck.

I think I’ll re-bore the hole on that next setup, since its axis needs to be normal to the faces I’ll be machining. Then make the spigot. I suppose any out of true could mean the rims don’t mate precisely.

Those shape grinding bits are what I use, but I got a box full from Amazon for not much more. I took a chance on quality, but the ones I ended up with are just as good as original Dremel ones.

I’ll continue machining, and worry about clean-up just before fixing the halves together I think.

[Dr_GMJNParticipant @dr_gmjn]

Re-set the first wheel without much problem. Got it more or less spot-on, but couldn’t quite get it perfect. It’s all going to be finally skimmed once assembled I guess, so no big deal:

Faced the mating faces without issue, and then re-bored the 10mm hole a bit to true it perfectly, then the larger diameter which will be inside the middle of the hub to a depth of about 10mm:

Then turned the locating spigot between centres:

Then set the second wheel in the chuck:

And turned the outer faces and boss without too much problem, although the scale seemed a lot more robust on this one – a few sparks until it all got cleaned off:

I’ve left it for today – I need to figure out how to measure the outer diameters to get them more or less matched before joining; they are too big for any of my calipers:

[Dr_GMJNParticipant @dr_gmjn]

I found a method online of measuring diameters of more than the calliper’s opening dimension – by measuring a chord length, and its distance from the circumference.

Might give it a try.

[JasonBModerator @jasonb]

A flat or square length of bar with two toolmakers clamps set to touch the rim of the first flywheel can be used to gauge the diameter of the other. One step further is to add a feeler gauge of say 20thou when you set the clamps, this will allow your gauge to slip over the second wheel as it gets within 20thou of finished size and if you then use thinner fealer gauges you can measure the gap and take the gauge thickness from 20 to give the final amount to come off.

[Dr_GMJNParticipant @dr_gmjn]

Thanks Jason. I suppose another variation of your method would be to set the clamp on the second wheel (the oversized one currently in the chuck), then put it over the first one and use gauge blocks to find the difference. Then half that figure and use the cross-slide dial to turn to size?

Before doing that I’ll turn it around in the chuck and bore the hole, so that the final o/d and mating face will be all perpendicular. Then finally turn the o/d.

[Michael GilliganParticipant @michaelgilligan61133]

Might I suggest that if you simply wish to match the diameters, it would be much easier to check the circumferences

Simply wrap a length of fine wire around one, and then t’other.

No absolute measurements required.

MichaelG.

[Dr_GMJNParticipant @dr_gmjn]

Thanks Michael. Yes I could try that. It would be nice to have a figure to machine to though, even if it’s approximate.

[DiogenesParticipant @diogenes]

Normally I’d just note the reference from the handwheel dial and turn the second wheel to that – certainly possible that I’m mis-apprehending the problem tho…

[Diogenes]

On Diogenes Said:

Normally I’d just note the reference from the handwheel dial and turn the second wheel to that – certainly possible that I’m mis-apprehending the problem tho…

Thanks. There have been a lot of tool post adjustments between the first and second O/D turning, so a fixed reference isn’t possible now really. I suppose I could/should have done it that way had I planned it better.

I could re-set the first wheel, get a reading then set the second, but…

End of the day both wheels will be finally skimmed across when they’re joined, being in the right ballpark would be good though.

I’m glad I left it last night to have a think: If I’m taking the second wheel off now to turn it around, I realised I can measure both diameters with my height gauge!

Might try some of the other methods just to see how accurate they are.

[Dr_GMJN]

On Dr_GMJN Said:

Thanks Michael. Yes I could try that. It would be nice to have a figure to machine to though, even if it’s approximate.

Wot Michael said, but use a tape measure.

An interesting question is, “how accurate does it need to be?”   Presumably not piston into cylinder accuracy

A steel tape should be more accurate than a dressmakers tape (about ±1mm on circumference), and both would be inferior to a big caliper (±0.02mm on diameter).  Usual health warning about my maths!!!

Say an accurate ⌀150.00 mm wheel is available, circumference 471.30mm:

• Measured by tape then the calculated diameter will be in the range 149.68 to 150.32mm.
• Measured by caliper then the diameter will be in the range 149.98 to 150.02

The tape is worse than the caliper by about ±0.3mm. ±0.15 if the operator is confident he can read the tape within ±0.5mm.  Is that “good enough”?

Gets exciting if a ±0.02mm caliper isn’t good enough!   There must be a way: during WW1 16″ shells were individually turned to better than 1 thou accuracy, in sets, each slightly larger than the previous to compensate for the thin layer of metal removed from  gun barrels by flame and friction on every firing.  Necessary when a shell, weighing about a ton, is required to land inside an oval about the size of a tennis court 15 miles away, and big gun barrels wear out after about 150 shots.

Dave

 

[Dr_GMJNParticipant @dr_gmjn]

Thanks Dave – in terms of accuracy, all will be revealed later!

Interesting anecdote about the shells. Must have been a logistical nightmare.

[JasonBModerator @jasonb]

Going back to the handwheel suggestion. Put your alignment pin in the flywheel that is in the chuck, slip on the previously turned one and touch the tool on the rim and zero the handwheel. Now you know the setting to turn the second handwheel to.

It’s times like these that my 300mm digi calliper comes out of the draw.

[halfnutParticipant @halfnut]

You could just use a 12 inch rule with 64ths graduations. Easy enough to get the two wheels within 5 thou of each other, using a magnifying glass if old eyes are fading like mine. Close enough for the purpose. It’s a flywheel, not a piston needing a precision fit. Part of machining is knowing when to apply appropriate tolerances so as not to waste time making silk purses when sows ears are all that’s needed.

Most important thing is to get the rim running true to the hub bore so no wobble is visible when the engine runs. People will see that but not one wheel being 5 or 10 thou bigger than the other one.

If you did need to get both the same size for some reason, — personal satisfaction etc –mounting both wheels on a common stub mandrel or arbor and taking one cut across the 2 wheels would be a sure way of doing it.

[halfnut]

On halfnut Said:

You could just use a 12 inch rule with 64ths graduations. Easy enough to get the two wheels within 5 thou of each other, using a magnifying glass if old eyes are fading like mine. Close enough for the purpose. It’s a flywheel, not a piston needing a precision fit. Part of machining is knowing when to apply appropriate tolerances so as not to waste time making silk purses when sows ears are all that’s needed.

Most important thing is to get the rim running true to the hub bore so no wobble is visible when the engine runs. People will see that but not one wheel being 5 or 10 thou bigger than the other one.

If you did need to get both the same size for some reason, — personal satisfaction etc –mounting both wheels on a common stub mandrel or arbor and taking one cut across the 2 wheels would be a sure way of doing it.

Thanks – yes as  I mentioned previously, the O/D will be machined as one once the wheels are joined. I just want to get them close before joining.

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