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

[Roger]

Oct 10, 2024 10:45:34 GMT JonL said:

I suspect you won't really notice much difference in efficiency until you start looking at things like water and coal consumption over a full day. At this scale it does make a difference, but not enough to notice lap by lap, if you see what I mean. You have the patience of a saint; I'm desperate to see this in action!

It will certainly be interesting to see how it pans out. I don't think we tend to notice much about efficiency, as long as the supply of Steam is plenty for what we need. However, I once drove a friend's Locomotive that was in such a dire state that you had to keep the blower on hard, all of the time, and the fire almost White hot with the bypass almost closed to be able to generate enough Steam.

The Club Locomotives are pretty well sorted out and well designed, but if you get one or more of the bottom flues blocked, you can be in real trouble when you're pulling a full train. My point is that the margins on some designs may not be that great. People like to talk about a free Steaming Boiler, and what this says to me is that the potential rate it can produce Steam is greatly in excess of what's needed. The bigger that margin, the easier it is to drive, because you don't get caught out so easily when the pressure is low, the water is low and the fire is low, or any combination thereof. Obviously you try to stay on top of things, but you get my point.

So my aim is to use the Steam as efficiently as possible, while having the capacity to make much more than I need. This is why I've gone for more Superheaters rather than less. Time will tell, but it's fun trying to figure these things out.

[Roger]

Time for some plumbing, this time for the RH Injector.

First up is the 4mm Steam Feed Pipe...


PXL_20241009_210127981 by David Buckland, on Flickr

I didn't show it, but all of the Flanges have a shallow location pocket for the pipe which not only makes it easier to set up, but also makes it a lot stronger. All of the Flanges are made from PB102.

PXL_20241009_210132679 by David Buckland, on Flickr

... which looks a bit peculiar here, but it's the effect of the flux.

PXL_20241009_210559723 by David Buckland, on Flickr

This is the Water Feed Pipe...

PXL_20241010_094402859 by David Buckland, on Flickr

... and the other half of it.

PXL_20241010_101612625 by David Buckland, on Flickr

I find that two turns of the 0.5mm Silver Solder wire is about right for the fillet I want. I wind it around a drill shank that's 1mm smaller than the pipe size. 

PXL_20241010_101620765 by David Buckland, on Flickr

You can see the groove for the 1mm section O-ring. The bolts are M1.4 Stainless which are screwed into threaded holes in the Injector Flanges. Obviously these should be nuts and bolts, with a gasket for the seal. I'll live with the lack of noticeable nuts for the sake of convenience.

PXL_20241010_110248402 by David Buckland, on Flickr

The brass unit on the end of the pipe is a coupler. This is a Water feed pipe, so there's no pressure. I've used two 1mm section O-rings in that to make sure it forms a good seal, even if the pipe isn't perfectly smooth and round.

PXL_20241010_110346705 by David Buckland, on Flickr

This pipe goes from the LH Pannier Tank Water Valve, heads forward, then dives under the Boiler behind the Firebox, and then back to the RH Injector. Hardly ideal, but hopefully it won't pose a problem.

PXL_20241010_110721566 by David Buckland, on Flickr

This pipe passes across the top of the two Blowdown Valves, and it's impossible to thread it through once the Boiler is in place.
I could have decided to install the pipe along with the Boiler, but that makes it a bit too much of a Chinese Puzzle. This way I can remove the pipe without taking the Boiler off.

pxl_20241010_144839279 by David Buckland, on Flickr

So this is how that ends up looking...

pxl_20241010_144901169 by David Buckland, on Flickr

... and for reference, this is how it looks on 1501, so tolerably close. I'll make the overflow pipe when the Rear Steps have been fitted, because the pipe runs back to those, exiting through a hole in the support bracket.

DSCN5646 by David Buckland, on Flickr

[andyhigham]

Oct 10, 2024 12:35:04 GMT Roger said:

Oct 10, 2024 10:45:34 GMT JonL said:

I suspect you won't really notice much difference in efficiency until you start looking at things like water and coal consumption over a full day. At this scale it does make a difference, but not enough to notice lap by lap, if you see what I mean. You have the patience of a saint; I'm desperate to see this in action!

It will certainly be interesting to see how it pans out. I don't think we tend to notice much about efficiency, as long as the supply of Steam is plenty for what we need. However, I once drove a friend's Locomotive that was in such a dire state that you had to keep the blower on hard, all of the time, and the fire almost White hot with the bypass almost closed to be able to generate enough Steam.

The Club Locomotives are pretty well sorted out and well designed, but if you get one or more of the bottom flues blocked, you can be in real trouble when you're pulling a full train. My point is that the margins on some designs may not be that great. People like to talk about a free Steaming Boiler, and what this says to me is that the potential rate it can produce Steam is greatly in excess of what's needed. The bigger that margin, the easier it is to drive, because you don't get caught out so easily when the pressure is low, the water is low and the fire is low, or any combination thereof. Obviously you try to stay on top of things, but you get my point.

So my aim is to use the Steam as efficiently as possible, while having the capacity to make much more than I need. This is why I've gone for more Superheaters rather than less. Time will tell, but it's fun trying to figure these things out.

With my 3 1/2" "Lucky 7" its just a case of chucking as much coal and water in as is physically possible. Those big 2" cylinders consume a lot of steam!

[Roger]

The Cab top half is bolted onto the bottom half with M1 nuts and bolts if it's going to be close to scale. However, this is really too small and fiddly to be practical. So I've decided to drill out the M1 clearance holes to 1.1mm and tap them M1.4

This avoids having nuts altogether, while using bolts that don't look unduly large. It's a compromise, because I don't want this to be a nightmare to maintain. As it is, there will be 12 M1.4 bolts to undo to get it apart.

So here's a supporting arrangement so I can drill and then press firmly down to get the Tap to bite. I think they're a bit blunt, I ought to get some new ones.

PXL_20241013_204724586 by David Buckland, on Flickr

[Roger]

The Drain Cock lever in the Cab is screwed to the floor with two M1.6 bolts. Originally, I thought these would have nuts on the back of them, but one of them ends up on top of the Frame Stretcher, and the other is inaccessible.

I'd already drilled them out to the clearance size, so that needs to be done differently. I opted to make some threaded inserts from an M2.5 high tensile bolt, drilled and tapped M1.6

Those were a bit fiddly to make. I have an M2.5 female mandrel to hold the bolt for drilling, tapping and parting off. However, cleaning up the through tapped hole isn't easy. Fortunately, parting it off with a very narrow, sharp, blade, meant that I could hold it in the mandrel with a bolt to stop it moving and managed to get a Bottom tap right the way through both of them.

Anyway, here are the holes being tapped M2.5...

PXL_20241116_101814717 by David Buckland, on Flickr

... and here are the inserts, ready for High Strength 601 Loctite applied from both sides. The thread isn't too snug, so wiggling a wire in the middle to move the insert slightly ought to be enough to guarantee the Loctite goes where it's needed.

I cleaned the holes with a cotton but and acetone from both sides, and the inserts spent an hour in an alkali degreaser that's part of the Chemical Blacking kit.

I might lightly peen these over when they're fully cured, and then file them flush. At least I know that the thread is unlikely to strip, being High Tensile material.

PXL_20241116_111818066 by David Buckland, on Flickr

So, a lot of faffing about for something I should have figured out when I designed it. At least that's one more small step towards getting it finished. I want to get the Drain Cock and Transfer Valve levers completely finished with all of the pins and split pins made.

This is the peculiar setup for the Drain Cock lever. The pointy triangle piece uses its own weight to let it drop into one of the slots, similar to a Pole Reverser. To release it, you pull back on the lever and push down on the other end of the pointy triangle.


20180110_105605 by David Buckland, on Flickr

I'd made this years ago, but hadn't cut the slots, so here those are going in now.

PXL_20241026_210806694 by David Buckland, on Flickr

I managed to break two PCB cutters before switching to this more robust and expensive Metalworking variety. It's only 0.5mm diameter, to it was asking a lot of PCB cutters, even with tiny cuts. They're just too long and brittle.

PXL_20241027_141633019 by David Buckland, on Flickr

The pins are 1.4mm diameter with a 0.55mm cross hole for the Split Pin. That maked them too slender to cross drill when they're machined to the finished diameter, so I turned down the and to 1.6mm and cross drilled that first.

PXL_20241027_143919537 by David Buckland, on Flickr

The ER16 collet mandrel is ideal for holding this sort of thing in the Lathe. I turn this sort of thing to the finished size in two or three stages, using a deep cut to the final size before moving on to the next length. That means there's more support for the cut, and avoids having to take fine cuts with it hanging out a long way.

PXL_20241027_150855730 by David Buckland, on Flickr

And here's how that looks. I'll have to get some scale grease and Coal dust to put on it later.

PXL_20241116_114526103 by David Buckland, on Flickr

I've also been working on the Chequer Plates for the Cab Floor. Again, I made these years ago, but now I have to decide how to fit them and keep them in place. I also need to get access to the bolts that hold the Cab in place as well as other ones for the Grate Release lever etc.

In the end, I opted to use Magnets, one advantage of making everything from Steel. I machined a 1,1mm deep pocket 5.2mm diameter to take some 5mm x 1mm Neodymium Magnets. I don't think I'll need to stick those in place because they want to stay in their pockets, even when you pull them off another Steel surface.

The ones in the wooden floor ar 0.5mm thick. I managed to ruin the original floor board I made by going too deep, trying to use a 1mm magnet, so I ended up having to make another one.

All of the plates were on the big size, so I've trimmed them down to make sure there's enough room for the paint thickness.

PXL_20241116_120241125 by David Buckland, on Flickr

[baldric]

Just for info, it is common to just push down on the triangle latch to close the drain cocks, without pulling the handle back.
As is normal, your work is looking really good, something I aspire to.
Baldric.

[Roger]

Nov 17, 2024 16:05:01 GMT baldric said:

Just for info, it is common to just push down on the triangle latch to close the drain cocks, without pulling the handle back.
As is normal, your work is looking really good, something I aspire to.
Baldric.

Hi Baldric,
Ah, I see what you're saying now. It doesn't take much force to release the latch. Thanks for that.

[Roger]

This is the vertical link from the Drain Cock Lever down to the Bell Crank that takes the motion through the frame behind the rear wheel flange. The top one slipped and ended up being scrapped.

This is 1.5mm Gauge Plate, machined with a 2.5mm Carbide cutter.

PXL_20241117_120131189 by David Buckland, on Flickr

Once connected, I could set the correct position of the actuating lever at the front. Here that is being cross drilled 0.8mm to take a piece of Stainless Steel spring wire.

PXL_20241117_195037411 by David Buckland, on Flickr

This is how that was held in the vise.

PXL_20241117_195046590 by David Buckland, on Flickr



PXL_20241117_203018484 by David Buckland, on Flickr

I may have to put a small joggle in the handle to miss the down pipe from the dummy Hydrostatic Lubricator. We'll see.

PXL_20241117_211656595 by David Buckland, on Flickr

The lever pulls nicely against the springs and latches with the pointy triangle.

PXL_20241117_211720221 by David Buckland, on Flickr

The rod passes under the outer edge of the horns like it does on 1501, and is supported by two brackets, one of which is shown here.

PXL_20241117_213626594 by David Buckland, on Flickr


And here's a video of the action of that on the valves. You can see a drop link that's attached to the frame. That converts the back and forward motion of the rod that. Fortunately, the rod operates in tension, so it works without any noticable play or elasticity, other than the spring tension.

PXL_20241117_212021540.TS by David Buckland, on Flickr

I don't know for certain that the tiny ball valves will seal reliably, but I have the option to use tiny O-rings if that proves to be a problem.

Anyway, I'm pleased to have got this out of the way, it's not something I was looking forward to sorting out, being so fiddly.
Oh, and great news... Knupfer in Germany are now supplying M1 Stainless Bolts and Nuts, so I've ordered plenty of those. All of the fixings on the Drain Cocks are currently in Brass, which not only looks wrong but isn't very strong.

[andrewtoplis]

Does anyone know why the GWR used this latch arrangement? I've been on many engines and never seen another drain lever that needed holding in one position.

[Roger]

Nov 18, 2024 14:00:23 GMT andrewtoplis said:

Does anyone know why the GWR used this latch arrangement? I've been on many engines and never seen another drain lever that needed holding in one position.

I don't know why they used poppet type drain cocks, with a spring to hold them closed. However, once you've made that decision, you have to hold them open against the spring force, so there has to be some kind of arrangement to achieve that.

[mbrown]

Not "big railway" examples, I know - but most of the Talyllyn locos have some positive engagement for "open" and "shut" with the cocks. No 7, Tom Rolt, has sprung poppet valve cocks after the GWR style (and 3 per cylinder too!) and the lever works in a quadrant slipping into slots at the sides. No.4 has plug cocks, but the weight of the linkage tends to let them drop open so it has a detent on the quadrant to retain the lever in the shut position. Nos 3 and 6 have pull-out levers which are notched for the two positions. Only Nos 1 and 2 have cock linkages stiff enough to require nothing to hold them in position.

Horses for courses, I guess.

Malcolm

[JonL]

I have used a spring to hold them open on my Britannia; You pull the lever while pulling away, then let go. I wanted something fairly foolproof with Piston valves.