Stuart 10V Vertical Steam Engine

[dr_gn]

rolster said:

I noticed your excentric strap issues, but not sure how far you have already gone into the machining process, as ideally before the top surface of the excentric strap on the bolted side is reduced down, then you: clamp the strap vertically; file a small flat (but within what you will take away later on finishing) and center punch the hole centre, by hand. Then carefully using a long drill bit (to get the chuck above the top of the excentric strap), drill the hole vertically down. If you don't have a long drill set, then an extension with a collar can be made just make the hole in the end to hold the drill bit an interfearance fit, heat the collar sligthy and pop the drill bit in the freezer, then insert the drill bit and let them normalise. You can then heat the collar afterwards to retrieve the drill bit. Alternatively use the same drill to drill a hole in the extension and then loctight it in place, but then you loose the drill bit. As seen there is not enough room for a centre drill, unless you can find some of the long ones, which i have not seen for a very long time. For the conical part of the oil resevoir, i suggest a taper reamer and then hand finishing the flare with a small burr or such. Very much enjoying the project and your updates.

Thanks rolster. On the advice of the ME forum, I managed to find a long series (3” long) 4mm O/D centre drill, which will just fit next to the arm, drill the hole and make the countersink in one operation.

ETA, I've finished the strap apart from the hole. The part is supplied as a brass stamping, and is near net shape. A few flats need milling, and of course the flanks and holes, but the area where the oil hole is just needs polishing, so you get one change to center it correctly. Shouldn't be an issue with the edge finder though. Cheers.

Edited by dr_gn on Monday 28th September 11:27

[rolster]

Great news on finding the long centre drill. I have not seen one in a long time, they are so useful but usually break when machining sticky materials. i think the last time i saw any, was when digging through some trays at Tracy Tools, when they used to be in Dartmouth. I have a vague memory of the excentric strap being a casting way back when, but obviously now a stamping.

[dr_gn]

rolster said:

Great news on finding the long centre drill. I have not seen one in a long time, they are so useful but usually break when machining sticky materials. i think the last time i saw any, was when digging through some trays at Tracy Tools, when they used to be in Dartmouth. I have a vague memory of the excentric strap being a casting way back when, but obviously now a stamping.

It looks like a casting to me, as did the connecting rod and the cross-slide, but they are often referred to as stampings, so I don't really know.

[dr_gn]

Today I re-visited the cylinder, and made some progress with the steam ports.

First off, the pockets adjacent to the cylinder. A depth and diameter is given, but no centre location. I used a 6mm milling cutter, moved to marked-out arcs defined by the gasket cut-outs:





Then the exhaust drilling, to measured dimensions from the drawing. I marked out the projected position of the cast-in ports as a double check. Luckily the drill broke through the back of the port perfectly:



Then opened up the hole for a few mm, and tapped for the exhaust pipe fitting:



So that one turned out ok:





Then the tricky angled ones I’ve been putting off for a while. I started by extending all the port lines to the edge of the casting, and effectively drawing the positions of the ports on the side using the projected lines and measured depths. I then got the tilt angle using a protractor, and made a setting jig from an old plastic card (26 degrees):



The machined port face was located against the gap in the vice bed, ensuring it was square. Then a centre drill was used to start the hole dead in the corner of the milled port:



With the dro zeroed, I moved the casting so I could set the z-stop such that any error wouldn’t result in breaking into the exhaust port, giving me a chance to correct things if necessary:



Then moved back to x-zero and drilled. It broke through bang in the corner of the port, as did the other side. Which was nice:





Next will be the insulation jacket securing holes, and the drain cock holes, but I’m waiting for a tap for those.

[dhutch]

Great as always, always a bit of a 'hope this works out ok' as you set off drilling that sort of a hole.
Not done it in this sort of setting, but have drilled a few holes through walls in houses and hoped the exit point it about where planned!

[dr_gn]

dhutch said:

Great as always, always a bit of a 'hope this works out ok' as you set off drilling that sort of a hole.
Not done it in this sort of setting, but have drilled a few holes through walls in houses and hoped the exit point it about where planned!

Yes exactly. I remember when I was a kid, my dad and I wanted to put a phone in the separate garage next door, so we drilled a hole for the extension cable under the soffit of their bungalow, thinking it was above the level of the living room ceiling, and would end up in the loft. It didn't. My mum wasn't happy when a ragged exit hole suddenly appeared in the middle of the wall opposite where she was sitting...Much shouting.

Happy days.

[dhutch]

Love it! I can just imagine.

[dr_gn]

So today I tried to mill the outer cylinder concentric with the upper cylinder, using a method suggested on the forum. This involved positioning a rod in the bore, putting it in the vice and milling a series of flats all around:



I must admit I found it hard to position correctly - it was easy to get it into a position where the o/d wasn’t at its lowest point relative to the cutter. This culminated in it grabbing, and damaging the casting:



Maybe it wasn’t orientated right, and I guess the vice should have been tighter, but either way it’s not a process I was particularly happy with.

Anyway, luckily the damage was only cosmetic, and some epoxy metal and flatting and re-priming (for the next stages of marking out) resulted in the desired outcome, ie a consistent step to the end caps:





I profiled the cladding using an 18mm socket, and test fitted it. It still needs trimming a bit:



But so far, so good:



Not sure if the cladding is some kind of anodised metal, but the finish is slightly flawed at one point. I might spray it satin black in the end.

Also painted the box bed and screwed it to the wooden base:

[dhutch]

dr_gn said:

So today I tried to mill the outer cylinder concentric with the upper cylinder, using a method suggested on the forum. This involved positioning a rod in the bore, putting it in the vice and milling a series of flats all around:



I must admit I found it hard to position correctly - it was easy to get it into a position where the o/d wasn’t at its lowest point relative to the cutter.

Yes, I can see its one of those jobs where it sort of works, but not is a warm and satisfy way. Still it's looks very well for it.

You forget the scale till you see it with that socket.

Daniel

[dr_gn]

Eccentric strap. Started by mounting the stamping into the 4-jaw chuck, using a tight fitting spigot in the tailstock chuck as a guide:



Then bored the hole:



Transferred to the mill and faced the main bore sides with the fly cutter:



The shaft was bent:



So I straightened it the best I could using a screwdriver and spanner as levers:





Then milled the flats and corners level:



and drilled the clamp hole:



and then the tapped locating pin hole after first milling a bit of a flat:



Cut the slot using the 0.8 mm slitting saw:



Then drilled the small end for its bolt. The specified clearance hole sizes on the plans are all way too big for a good fit:



and milled the faces symmetrical and to be a sliding fit in the fork end of the valve rod:



Finally the oil hole. Tricky one because the 1mm/4mm long series centre drill would have removed way too much material had I used it to drill through to the bore. I decided to make a cranked oil hole by first angling the rod to give clearance for a 1mm standard drill in a small chuck, and making a centre dot with the long centre drill:



Then drilling to the bore using a 1mm drill:



Then returning to vertical and using the center drill to get a chamfer on the flat surface, while allowing the 1mm part to break into the initial hole:



Made a bit of a meal of it I guess, but there was no room available for a simpler method (that I could think of), and I wanted an un-skewed cone at the surface:



I also turned two standard nuts to thin nuts to make them look less clunky:





Here it is test fitted to the eccentric. I cut the eccentric screw down by threading it into some thin strip and filing the end off:



Getting there.

[dr_gn]

Also been fiddling about finishing some other stuff. The lower cylinder boss didn’t match the standard diameter, so secured them together and turned as a pair (should have done that in the first place):





Also needed 0.6mm taking off the height:



I took it off the feet because the cross slide bore was machined in the same setup as the top surface.

[dhutch]

Looking good as always. The oil won't notice the hole being at a mild angle! Half nuts look nice.

[dr_gn]

Back to the cylinder and it’s aluminium shroud. I Bent it to a good fit, but still oversized. The challenge being to drill holes for the 4 retaining screws, exhaust pipe and drain cocks. After much thought I settled on this:

Align the cylinder side in the vice, using a turned hardwood plug as a spacer. This allows the vice to be tightened without crushing the excess aluminium:



After measuring and getting co-ordinates for both retaining screws, Spring the shroud in place and hold tight by hand, then drill a pilot hole:



Remove shroud, drill and tap 8BA. I opened the shroud holes up a bit by hand. The hole is literally right on the edge of being sound - it’s actually broken through the wall towards its base:



Re-fit shroud, screw in place and repeat for the other hole:





Then turn around and repeat on the other side. I used an edge finder and a wiggled point to determine datums and co-ordinates again:









That worked fine:



Then it was a simple matter of flatting the excess aluminium on the surface plate:



The screws can’t be tightened without bowing the shroud - it’s un-supported where the screws are. I might put some epoxy metal behind and file it flush at some point, unless anyone can suggest a better method.







I’m quite pleased with the fit - especially next to the valve chest. I’m glad I thought to make the sides wider than specified on the drawing to make everything flush.

[dr_gn]

Then the drain cock holes. These will be clearance holes in the shroud, drilled and tapped in the cylinder casting. The issue now was to drill pilot holes without crushing the shroud. I opted to first get the centre of the cylinder with the casing held vertically in the vice. The fixed jaw bring the y-datum:



Then turn through 90 degrees. The y centre distance is now the y-axis offset from the fixed jaw. I then spot- faced the casting with a 6.5mm slot drill, after using the edge finder to determine the x-offset:



The second spot-face caused the drill to grab, and damage the casting. I have a theory about what is causing this recurrent issue with the z-axis:



Anyway, I re-set in the vice and centre marked the spot faces:



Then fitted the shroud and clamped in the vice using a stiff brass rod, offset from the vice jaw with some old 1” slip gauges to avoid contact with the moving jaw:



Then centre drilled using identical co-ordinates:



Then drilled 1mm diameter straight into the bore:



Then drilled and tapped to the drain cock thread size and depth.

Next on to the exhaust hole in the shroud using the same basic method:





The drain cock and exhaust holes need opening up - I’ve got a small step drill on order. Also need some fibre washers to seat the drain cock bosses:



Overall OK so far, but the anodising is so thin and easily scratched that I may end up painting it.





I also need to sort out the issue with the mill z-feed before it causes a scrap casting.

[vanwithwindows]

Absolutely love this! Was given a small lathe and milling machine probably 10 years ago and managed to figure out enough to build a stirling engine.

Really want to recommision them and build something else now...

[dr_gn]

vanwithwindows said:

Absolutely love this! Was given a small lathe and milling machine probably 10 years ago and managed to figure out enough to build a stirling engine.

Really want to recommision them and build something else now...

Go for it. I’ve never attempted anything like this before, but I’m loving everything from modding the machine tools to figuring out machining & fixturing strategies. Plus I should have something decent looking to fiddle about with at the end of it.

[dr_gn]

So the final bits of machining I think - the piston and cross head. Before turning them to size, I made a couple of laps out of turned down oak:



Charged them with #600 SiC and oil, and worked the bores up and down:







I think the laps should have been a bit tighter - they quickly became quite free in the bores, but anyway, onwards...

[dr_gn]

Started by facing the brass for the cylinder:



Drilling and tapping to 5BA:



Then marking out and turning the oil grooves:



Then turned to finished diameter +0.5mm, and parted off.

Next, after confirming the piston rod ran true in the collet chuck (it was within 0.002”), faced it off, turned down and ran a 5BA thread down, to the depth of the piston:





Then tightened the piston onto it, faced the assembly, and scribed a line over the exposed join so it can always be tightened to the same position:



Then turned to he O/D in fractions of a mm until it just fitted in the cylinder bore:



It’s a good fit; if I put the cylinder vertically on the surface plate and cover the valve port and drain hole up, the piston slowly makes its way down the bore. I don’t think it needs lapping. The piston and rod is also a nice sliding fit With the lower cover fitted:



Here’s a video that should work if you click on it:



Now to repeat the process for the cross head end of the piston rod.

Edited by dr_gn on Sunday 4th October 19:30

[dhutch]

That video is lovely!

Also; you appear to have a hole in the back of your thumb.


Daniel

[dr_gn]

dhutch said:

That video is lovely!

Also; you appear to have a hole in the back of your thumb.


Daniel

Thanks!

Yes I noticed the hole. If I’m ever threading manually in the lathe, or reaching for something near the mill head, I seem to end up with a cut. That insert for cutting stainless, with the knife edges and small tip radius is particularly harsh.