Help with 'Speedy' valve gear and other issues...

[Roger]

Aug 27, 2024 16:33:36 GMT ianholder said:

Hello Roger, I have always found that viton o-rings work for me. But I am interested to know why you are going to China when all types of o-rings are readily available here. I have used Simply Bearings whenever I need them and they usually come by return. They have a vast range of sizes in all materials. Regards Ian ( I am only a customer of Simply Bearings)

Hi Ian,
I buy O-rings of all types through eBay because they're almost always cheaper than mainstream suppliers. I do occasionally use Simply Bearings for those and bearings too though.
Viton rings tend to be a bit inflexible and hard, and this application really needs to keep the friction to a minimum. I thought I'd give these a try, in the hope that they would be more flexible and have a more polished finish that might be lower friction than Viton.
I've used Viton on all of the Boiler fittings and everything that comes into contact with Steam elsewhere. The only gaskets are on the Cylinder Covers, and there will be very few joints that will use sealant. I'm a huge fan of O-rings, I don't know why they're not universally used in ME.

[Roger]

I've finally got round to piping up the Steam Brake Cylinder to the Combined Vacuum and Steam Brake. There are quite a few pipe runs around here, hence wanting to get the dummy Hydrostatic Lubricator in position first. I've looped the pipe near to the Cylinder so that it's got more flexibility.

PXL_20240828_090751469 by David Buckland, on Flickr

I thought I would go a bit further with the Vacuum Braking system, even though I'm not sure I'll end up actually using it. Ideally, I'd like to make a driving trolley with Vacuum Brakes.

Anyway, what I think you call the Train Pipe has a connection on the side of it on 1501 for the LH Vacuum gauge, so that's what this is going to be.

PXL_20240828_103351355 by David Buckland, on Flickr

The pipe is being supported by the shank of a suitable drill so that it doesn't get crushed. It's just clear of the spot where I need to drill the hole.

PXL_20240828_153048357 by David Buckland, on Flickr

The eagle eyed amongst you will see what went wrong in this shot where the fitting is being Silver Soldered in place.

PXL_20240828_160635263 by David Buckland, on Flickr



PXL_20240828_160819950 by David Buckland, on Flickr

I thought I'd add this first, and then the fitting for the Brake Valve.

PXL_20240828_172028605 by David Buckland, on Flickr

That was Silver Soldered with plenty of Nail Varnish to keep the Silver Solder away from the nut, thread and O-ring groove.

PXL_20240828_185640605 by David Buckland, on Flickr

And if you're still looking for the error, I managed to drill the first pipe I made on the wrong side. This is where it should have been. Fortunately I spotted the problem before Silver Soldering the fittings!

On 1501, the pipes come down in front of the open Fire Door just as it's shown here. The Ejector Steam pipe needs to be added next.

I refitted the Blower Valve including the Auxiliary Valve with the Cool Handle. Somewhere along the way I've mislaid the Brake Handle. I have a feeling it was masked up for spraying Red, but I can't see it at the moment. I do have the connecting link though. Ideally I'd like to finish those and get them on the backhead.

PXL_20240828_194722947 by David Buckland, on Flickr



PXL_20240828_194736917 by David Buckland, on Flickr

[mbrown]

Once I had fitted vacuum brakes to my driving truck and fitted up the locos accordingly, I never looked back. Running my non-vacuum fitted Bagnall the other week took me back to the old world of hauling on the hand brake to stop instead of moving a little Tufnol handle on the brake valve with one finger - no comparison as an experience.

If you go to all that trouble to make the controls as close to scale as possible, you might as well go the whole hog and make the driving experience as close to full-size as you can.

Malcolm

[Roger]

Aug 28, 2024 20:42:07 GMT mbrown said:

Once I had fitted vacuum brakes to my driving truck and fitted up the locos accordingly, I never looked back. Running my non-vacuum fitted Bagnall the other week took me back to the old world of hauling on the hand brake to stop instead of moving a little Tufnol handle on the brake valve with one finger - no comparison as an experience.

If you go to all that trouble to make the controls as close to scale as possible, you might as well go the whole hog and make the driving experience as close to full-size as you can.

Malcolm

Fair enough, I've never driven a Vacuum Braked setup, so I don't know how that feels. It is appealing though. I'll carry on and make it possible to add the rest later. I'm not going to delay the build any more by desiging a Vacuum Ejector at this point. I'll take a look again when it's all up and running.

[Roger]

I can't tighten the slotted nut that holds the Train Pipe onto the Brake Valve, so here's a tool being made from 1.5mm Gauge Plate.

PXL_20240829_090720225 by David Buckland, on Flickr



PXL_20240829_112624147 by David Buckland, on Flickr



PXL_20240829_112647716 by David Buckland, on Flickr

That's all very nice... except... it didn't work. It doesn't latch onto the slot in the nut without wanting to slip off. It's also a bit on the narrow side.

So here's my second attempt which works nicely. Now I know why they're the shape that they usually are.

PXL_20240831_113806995 by David Buckland, on Flickr

This is pretty delicate, so I've hardened and tempered it to make it stronger. The slot is only 0.8mm wide, so the tool needs to be slightly narrower than that. I've also made this one from 2mm Gauge Plate too.

PXL_20240831_113829364 by David Buckland, on Flickr

Fitting the Whistles, it became clear that I hadn't got the pipes with the right amount of offset, because the Whistle Servo Valve didn't clear the buffer angle. So I desoldered and tidied up the nipples from the old pipes and here's one being bent for the second attempt.

Normally I use a flat slipper with a semi-circular groove, but there wasn't room to get that in. So I made a barrel type of support that could fit over the clamp pivot. Ok, it doesn't actually clamp the pipe, but it's good enough and doesn't mark the tube.

PXL_20240830_155957971 by David Buckland, on Flickr

That's much better.

PXL_20240830_200820579 by David Buckland, on Flickr

I had to take it all apart again to get the Steam Feed pipe in place and bend it to line up with the Union on the Whistle Servo Valve. It's a 3mm pipe, which hopefully is big enough to supply enough Steam. I could make it bigger, but on 1501 it's clearly smaller than the other two pipes on the Turret.

PXL_20240831_115134864 by David Buckland, on Flickr

I had to disassemble the Turret to get the pipe in the right position, and that proved to by awkward because a standard 7mm spanner is too thick and bulky to get at the locking nuts.

So here's a custom slimline 7mm spanner to make that job easier. I've Hardened and Tempered that too. The setup below allows a flame to gently get to both sides to heat it evenly, and it's easy to just tip it into the Grinder water tray when it's at the right colour.

PXL_20240831_191403405 by David Buckland, on Flickr



PXL_20240831_192917868 by David Buckland, on Flickr

That fits much better.

PXL_20240831_192929887 by David Buckland, on Flickr

Another trial fitting of all the pipes made it clear that the Train Pipe and the one for the Vacuum Ejector wouldn't go past the Cab Stretcher. This is why I haven't painted the stretcher yet.

So here it is back on the Mill to clear the pipes. They stand clear of the Firehole door, that's why they hit this. I'll have to add more slots to the Chequer Plates on the Footplate, but I'll do that later.

PXL_20240831_195453402 by David Buckland, on Flickr

That's better. I may have to add a clip to steady the pipes at the bottom though.

PXL_20240831_210918205 by David Buckland, on Flickr

[Roger]

Returning to the Whistle Servo Valve, I've now received some 0.5mm thick Stainless Steel wire to wind some stronger springs. I tried some at the original length, but decided to increase them to 20mm from 16.5mm to slightly increase the force.

I also opened up the clearance on the guide bush at the spring end, and increased the depth of the grooves on the Pistons to give just 10% compression so as to reduce the friction. I polished the Spool Valve element too, and replaced all of the O-rings for the Green FKM ones. These definitely feel smoother and slightly more flexible than the Black Viton variety that I usually source. Although they seem to be some kind of Viton, they aren't the same.

Anyway, here's a much more promising result. I've run this up to 90psi, and this test is at 60psi. It seems to run ok down to about 50psi which is probably good enough.

There's a small delay for it to operate when it's stone cold, and it's not instant even when it's hot. Obviously there's a volume behind the piston that needs to be filled with Steam, and then it has to move before the valve opens. Ideally the valve needs to be almost at the point of opening to start with, and it ought only to open as much as necessary once that happens. The total travel as manufactured is 1.6mm, so it's not a huge volume, but I could potentially shim it to make that slightly smaller.

Click on the picture below to see the valve in operation. You'll notice that there's a noticable venting of Steam on those tiny inlet valves I made. I might redesign those to have a better seal which would help with the delay issue. That might cause a delay in the off time though, but it's probably worth experimenting further with.

PXL_20240911_113133122.TS by David Buckland, on Flickr


Anyway, it's a different animal to before, and that's only due to relatively subtle changes. It's amazing just how differently it behaves on Steam compared to Compressed air.

[gambit]

Hi any chance of approximate dimensions for the support plates, Id like to fabricate them as im not into 3D Printing pete russell

[Roger]

Sept 11, 2024 15:31:33 GMT gambit said:

Hi any chance of approximate dimensions for the support plates, Id like to fabricate them as im not into 3D Printing pete russell

I think you might have posted this on the wrong thread?

[jasonb]

Roger, I think he wants details of the paint mixer, see this thread on ME, may be better to reply there.

www.model-engineer.co.uk/forums/topic/flexiable-paint-can-turner/

[Roger]

Sept 11, 2024 19:07:22 GMT jasonb said:

Roger, I think he wants details of the paint mixer, see this thread on ME, may be better to reply there.

www.model-engineer.co.uk/forums/topic/flexiable-paint-can-turner/

Ah, thanks for that. I don't ever look at the Model Engineering forum.

[Roger]

Sept 11, 2024 15:31:33 GMT gambit said:

Hi any chance of approximate dimensions for the support plates, Id like to fabricate them as im not into 3D Printing pete russell

Hi Pete,
If you'd like to PM me, I'll be able to supply you with everything you need.
Roger

[Roger]

I've redesigned the Piston Cover Plate so that it's now in two parts and integrates a larger drain valve with an O-ring seat.

My current thinking is that you're better off letting it blow out any excess condensed Steam so that it doesn't end up filling the Pilot steam pipe back up to the Pilot Valve. The pipe is very thin, so there's much more resistance to flow when it's filled with water.

The outlet hole is offset so that the ball can't block it, and it's nearer the bottom of the cylinder. The axially sealing O-ring serves the dual purpose of sealing the outlet and providing a seat for the 3mm Ceramic ball.

I've piped the outlet so that it can be directed down and away below the frames. It's going to get wet enough from the Steam coming out of the Whistles.

Hopefully this ball valve will quickly seal up when the Pilot Steam is applied, and open quickly open as the pressure drops. Obviously the exact way this will work in practice will depend on the spring rating and the fit of the Ball in the pocket.

This ought to make it more predictable and reliable. I can forgive a short delay in operation.

Sectioned valve with drain valve by David Buckland, on Flickr

[pault]

Hi Roger
part of the delay in operation may just be steam condensing in the pipe work or the valve. Given that steam reduces in volume by over 1600 times when it is condensed back into water that may explain it.

[Roger]

Sept 12, 2024 9:04:16 GMT pault said:

Hi Roger
part of the delay in operation may just be steam condensing in the pipe work or the valve. Given that steam reduces in volume by over 1600 times when it is condensed back into water that may explain it.

Hi Paul,
It's good to hear from you, I hope you're well.
I'm sure you're right, it's certainly an issue when it's stone cold, and there's no way it's all going to stay hot enough between operations. I have considered adding a needle valve to bleed Steam through the body of the valve to keep it hot. However, that's going to end up getting choked with Limescale, so it's probably not the most satisfactory solution.

[chris vine]

The simple solution is to blow the whistle frequently!!
Chris

[simon6200]

“It isn’t wrong, but we just don’t do it.”

[JonL]

Sept 12, 2024 20:02:08 GMT chris vine said:

The simple solution is to blow the whistle frequently!!
Chris

I'm in the habit of slightly cracking open my whistle valve a little before the SW boards at my club, it means its more likely to sing when needed. I even considered a globe valve in parallel to let a little steam through all the time when running.

[Roger]

Ok, the last iteration of the valve didn't work well enough. The sprung outlet valve was too slow to open and varied too much with pressure when I tried different spring weights. I found this out on Air, so it had no chance of working with Steam.

However, I tried an experiment with the valve spring removed, and using as a non-return valve for the inlet instead. I then found that it opened fine on Air, but at lower pressure it wouldn't quite open. If I put my finger over the outlet, which is now always open, I found it operated even before I completely closed the outlet. This was still using the 1mm outled fitting which was intended to be used with a 2mm pipe to direct the Steam down between the frames.

The upshot of this was that I thought that a 1.6mm outlet pipe might provide sufficient back pressure to operate the Pilot piston, but still be big enough to let it close quickly when the pilot steam was removed. The non-return valve on the inlet stops condensate being pushed back up to the valve on the turret, and it allows condensate to completely drain from the whole pipe and valve assembly. 

So here's how that looks.


Sectioned valve with drain valve by David Buckland, on Flickr

This very nearly worked, but I found that the valve wouldn't return smartly when it was hot.

The only remedies for that are to increase the strength of the return spring, or make it easier to move the spool valve.
Since the spring is already pretty strong, I opted to decrease the compression of the O-rings.

So here's the pilot piston groove being made deeper to give 0.09mm compression. The ER16 collet chuck is so useful for this sort of thing.

PXL_20240921_180013052 by David Buckland, on Flickr

I also reduced the spool valve diameter from 5.15mm to 5.09mm on the Tool & Cutter Grinder.

PXL_20240921_191545783 by David Buckland, on Flickr

And finally, here's a video of that working nicely at last. I think it's going to need a little displacement lubricator for all three steam inlets, but that's easy enough to arrange. If it dries out, it's going to become unreliable

PXL_20240921_195144284.TS by David Buckland, on Flickr

Completely unrelated to this is this new holder I've made for some tiny Carbide Boring bars I was given a while ago. I've always struggle to clamp them between a couple of pieces of Aluminium sheet, but it's a real bodge.

So here, finally, is a holder that will really get hold of them. I've propped up one of them on the bottom holder so you can see the tricky cross section. The pocket was rouged out with a 1.5mm Carbide 4 flute and finished with a 1.5mm Ball Nosed cutter with a 0.1mm overlap. That finishing cut took about 45 minutes.

PXL_20240921_201801831 by David Buckland, on Flickr



PXL_20240921_201921946 by David Buckland, on Flickr

[Roger]

Now that I'm happy with the Whistle Servo Valve, it's clear that it won't continue to work for long periods without lubrication. It's all additional complication, but I can't see an alternative at the moment. I don't think even PTFE would work without some lubrication.

Anyway, this is what I've decided to do. This is a very simple Displacement Lubricator for the main Steam feed to the Servo Valve.

Big lubricator by David Buckland, on Flickr

The idea is that it's big enough to last a long time, maybe all season. The design allows for the removal of the Reservoir using a box spanner without removing anything else. I'm using the same AF size for the smaller ones for the Pilot Steam feeds.

The Reservoir is filled to the brim, and then refitted. The O-ring seals on the diameter, so finger tight is all that's needed.

Sectioned big lubricator by David Buckland, on Flickr

It's way too much effort to 3D model the pipe runs, but I think this will just about fit like this. There will need to be spacers and some sort of plate to hold them. I may make a new, bigger bracket that holds the whistles and these too. However, it might be preferable to mount just the lubricators on a separate plate so that the Whistles and the Servo Valve can be removed separately.  I'll see how it looks when I've got all of the pieces made and I can mock it up. Getting a spanner onto the various pipes may not be easy. Obviously I'm not planning on taking this apart very often, but I don't want it to be a nightmare when I do.

Whistle servo layout by David Buckland, on Flickr

[Oily Rag]

I am trying to catch up on Roger's build.
I see George Daniels in still channeling in strong!