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.

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