Stuart 10V Build Log – Complete Beginner…

[Dr_GMJNParticipant @dr_gmjn]

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:

[Dr_GMJNParticipant @dr_gmjn]

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_GMJNParticipant @dr_gmjn]

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, so I know they are pretty much square to each other.

[Dr_GMJNParticipant @dr_gmjn]

When I get around to making the piston/cross head, and drilling the connecting rod hole, is there any advantage of calculating the mid point of the piston in terms of equal cylinder volumes top and bottom (compensating for the rod volume for the lower volume, and setting the Crank at mid throw to that, or is that just unnecessary and pointless?

[SillyOldDufferModerator @sillyoldduffer]

Gorgeous! Is the secret attention to detail?

Dave

[Dr_GMJNParticipant @dr_gmjn]

Posted by SillyOldDuffer on 03/10/2020 10:31:05:

Gorgeous! Is the secret attention to detail?

Dave

Thanks Dave.

I think if there’s any secret at all, it’s based on me having a large buffing wheel!

I build small scale plastic and paper kits, mainly of aircraft, ships and cars, so I suppose I try to get a similar finish on any type of modelling.

Getting a good superficial finish is one thing, but secondary to machining skill – something I obviously lack as a beginner, but am gradually getting better at. What this build has shown me is that at the very least I have a great deal to learn about machining to set dimensions, and compensating for the foibles of my equipment to do so. The learning curve is extremely steep, but by asking questions on this forum, and getting great advice, I’ve made progress.

[Dr_GMJNParticipant @dr_gmjn]

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_GMJNParticipant @dr_gmjn]

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 being 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, and have started a thread on it elsewhere on the forum:

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.

[Dr_GMJNParticipant @dr_gmjn]

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_GMJNParticipant @dr_gmjn]

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 is a video, which might work if you click on it:

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

Edited By Dr_GMJN on 04/10/2020 19:51:59

[Dr_GMJNParticipant @dr_gmjn]

Guys – I’m getting very close to test assembling the whole thing and running it for the first time. Is the best way just to run at a low speed on air with plenty of oil? Is gland packing essential at this stage?

What oil should I use, and approximately how long should I have to run it for to bed it in? I’ve test assembled various sub-assemblies and everything seems ok. The piston/rod/cross head has a couple of minor binds – probably on the rod/lower cover hole – but nothing significant.

When that process is done, plan is to strip it, thoroughly clean everything and paint it. Then re-assemble with gland packing.

Any advice on the end-game much appreciated.

I can’t believe it’s nearly done. I thought it would be at least a years work or more for me.

[JasonBModerator @jasonb]

Should run without packing, I always run mine first with no gaskets, packing or piston ring/packing.

Just put a drop of light oil into the inlet every so often but should not take long to bed in with any luck. Don't use steam oil at this stage as it is far too sticky at room temperature, I use clock oil.

You will probably find you need a slightly higher pressure to start with so the compressor regulator will need to be set higher then control the speed by flow of air, once run in should work on a couple of Psi when not under load.

[Dr_GMJNParticipant @dr_gmjn]

Posted by JasonB on 07/10/2020 07:03:44:

Should run without packing, I always run mine first with no gaskets, packing or piston ring/packing.

Just put a drop of light oil into the inlet every so often but should not take long to bed in with any luck. Don't use steam oil at this stage as it is far too sticky at room temperature, I use clock oil.

You will probably find you need a slightly higher pressure to start with so the compressor regulator will need to be set higher then control the speed by flow of air, once run in should work on a couple of Psi when not under load.

Thanks for the info Jason.

[Dr_GMJNParticipant @dr_gmjn]

On to the cross head last night, which is supplied as a brass stamping. It’s got a spigot, which is handy for holding it for initial work. First job was to face the end:

Drill and tap for the piston rod:

Then turn the O/D to within about 0.010” of finished:

Saw off the spigot:

Tighten onto the piston rod, mark it so it can be tightened to the same position in future. Then mount in the collet chuck and incrementally turn to size for the standard bore. A good tip to easily get fractions of a thou feed is to turn the compound slide to a slight angle to the bed, such that any turn on the crank translates to a much smaller amount of feed into the work:

The final feature is the connecting rod hole. I was concerned that due to any errors in size accumulating from my own work, combined with the un-toleranced drawings, I might end up with the piston crashing into the cylinder caps. I decided to temporarily assemble the cylinder, measure it’s internal bore length, and calculate the clearances at each end based on the actual crank throw.

Measured the throw by using the z-dro on the mill:

…and the bore length by measuring the piston displacement in a similar way:

From these figures I calculated that I needed 0.7mm clearance at each end of the bore. I made a 0.7mm thick washer and put it in the bottom of the cylinder:

Then, with the crank at the bottom of its stroke, marked the hole position:

Double-checked at the top of the stroke, spot-on:

So then dis-assembled, and mounted in the mill vice. Double-checked it was level, then marked, drilled and reamed the pin hole:

Next up is making the threaded pin. I think that’s the last bit of machining before test assembly.

[Dr_GMJNParticipant @dr_gmjn]

For some reason I didn’t have enough rod left in the kit to make the pin – I think I made a mistake with the valve rod and had to scrap it. It was only a 15 minute job to turn one from an off-cut of steel though.

So here’s the first go at test assembly of all the mechanical parts (I'll have to sort the pip out on the connecting rod pin – the camera is a harsh critic):

And a video clip of it moving, lubricated with some light oil. Valve and timing setup isn’t done yet, and there is no gland packing. There is one slightly tight spot towards the bottom of piston travel, but it’s getting more free as I fiddle with it:

Next job is to make the inlet and exhaust fittings. I’ve got some hexagon bar on order, so they shouldn’t take long to make.

Edited By Dr_GMJN on 07/10/2020 08:00:39

[Dr_GMJNParticipant @dr_gmjn]

Just for completeness, here’s the piston and slider assembly, and the connecting rod pin:

I hope it still runs smoothly with the gland packing. I’ve marked the orientation of everything so I can re-assemble it the same way.

[Dr_GMJNParticipant @dr_gmjn]

The packing material supplied in the kit doesn't look right to me – at least it's not what I expected it to look like:

Does it need any special grease or other lubricant when fitting?

[JasonBModerator @jasonb]

I use a much greasier one that smells like it has tallow in it as well a graphite powder but have had it so long I can't remember where I got it from, not keen on that dry stuff. Another option is to take several lengths of plumbers PTFE take and twist it into a rope and use that,

[Dr_GMJNParticipant @dr_gmjn]

Posted by JasonB on 07/10/2020 13:17:00:

I use a much greasier one that smells like it has tallow in it as well a graphite powder but have had it so long I can't remember where I got it from, not keen on that dry stuff. Another option is to take several lengths of plumbers PTFE take and twist it into a rope and use that,

OK thanks. I've got a load of PTFE – like the sound of that.

[Dr_GMJNParticipant @dr_gmjn]

Made a start on painting the castings yesterday. Cleaned down with brake cleaner, and masked with Tamiya tape and Blu-Tack:

Primed with Tamiya fine surface primer and airbrushed with several thick coats of paint. After all the research I’ve done over the months, I’m fed up with the sight of green 10Vs, so decided on Dark Blue Meccano enamel that my dad bought decades ago, but never used. I think it will look great with polished silver and brass:

As expected, a few bits peeled off the smooth flywheel areas on removing the tape (should have removed it before the paint flashed off). Not a problem though because I’d always planned on a final corrective coat done in the lathe to get as concentric a demarcation as possible:

I often use this technique on scale models to get perfectly concentric painted bands on various things.

I thinned the paint a bit for the valve cover, and blobbed it into the cast recess, letting capillary action do the work:

Then into the oven to bake out the solvents and harden the paint a bit:

Pretty much done:

[Dr_GMJNParticipant @dr_gmjn]

Few loose ends to tidy up.

The hole positions for the cylinder cladding screws are such that the undersides are unsupported, making the cladding bow on tightening. I made some Milliput bosses, filed flush, then painted satin black:

Then the 1/4” thread for the steam inlet union:

And made a sealing washer parted off from some old copper pipe. Needs annealing:

[Dr_GMJNParticipant @dr_gmjn]

Every time I looked at the connecting rod:

…I saw an Elephant’s leg.

By mistakenly sawing off the turning spigot, I gave myself a problem in how to hold it to subsequently taper-turn the shaft. The main bearing block is turned to a diameter, so I decided to try and make a split fixture for that end, and clamp an aluminium block in the little end for centre drilling:

I drew it out on CAD, and settled on a 3 degree included angle taper. After setting the compound slide to 1 1/2 degrees, try as I might, I couldn’t get any of my turning tools to do it in one pass. I ended up doing half, then re-setting the tool and doing the rest. After a quick polish you can’t see the join. It now looks better:

Also cleaned up all the Little end pin end, the stud ends and bolt heads – most of them had prominent pips:

So now I’m waiting for some supplies to make the unions and open up the cladding holes, and it’ll be on to assembly and testing.

It’s worth noting that as I went through all the supplied fasteners, I found two of the nuts were half-nuts – probably for the eccentric clamp bolt. I’d already made my own half nuts by turning down some standard ones. I’ll just use the supplied ones for the big-end caps instead.

[Dr_GMJNParticipant @dr_gmjn]

Made an inlet union – I based it on the quick-release air supply from my airbrush:

Now for an exhaust stub.

[Dr_GMJNParticipant @dr_gmjn]

One thing I need to sort out: all the threaded parts I’ve made are horribly loose fitting. When I’ve got a split die I’ve always sprung it open as much as possible, but to no avail. I wonder if the taps I’ve got are loose tolerance? Something’s definitely not right in the threading department.

Actually – I say “all”, but thinking about it, it’s really the larger threads on the inlet fitting and gland nuts that are by far the worse.

 

Edited By Dr_GMJN on 12/10/2020 21:48:50

[JasonBModerator @jasonb]

I've had a few ME dies bought in recent years that don't cut a particularly good thread so that may be the problem.

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