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

[92220]

Hi Roger. Paul is correct. Don't sandwich paint in between riveted, or bolted, surfaces that have to be tight. Always use metal to metal contact. Over time a trapped paint coat would fret and thin and the joint would become loose. When painting the frames, paint the red first and then the black. Black will cover Red but Red won't cover Black. Because the joins between Black and Red, on the insides of the frames, are hidden, great care is not necessary in obtaining a perfect join between the Red and Black. A small overlap will be hidden. Alan is right about the use of hex heads too, though if they are long enough for the head to stay well proud of the surface, the adverse effect on the spraying would be minimal. As far as drilled holes go, I would just run a size drill through the holes to clear any paint residue. Fiddly but you can be sure the hole is to size, and not got a small blob of missed paint inside it. When I painted my fully assembled loco frames back in 2002, I gave them a coat of rust stabilising primer (Corroless S); allowed that to dry for 10 days, and then applied the top coats. The advantage of Corroless S is that it will kill any rust that may be lurking there, and prevent rust from starting, even if the paint is scratched, as long as it isn't a wide scratch. Don't know how it works but I used to sell loads of it for boat trailers and caravans. Although it specifies 2 coats, one thin coat works fine as long as there is no obvious rust. By that I mean if it hasn't penetrated the surface of the metal (which is unlikely with your loco!!!!). The frames can be primed with 2-pack etch primer which give a very thin coat, and it will cover both ferrous and non-ferrous metals. Allow to dry for around 72 hours, for all solvents to evaporate, before applying the colour-coats.

As far as how much to paint in one go, paint the inside surfaces and allow to dry and harden, then mask and paint the outside surfaces. When putting subsequent coats of paint on, either spray the second coat before the first is still tacky (that allows the 2 coats to become one single coat with no intercoat adhesion problems, or allow the first coat to dry for at least 24 hours before applying a second coat.

If you find you have to rub down an etch primer coating, DON'T, as long as it is a complete coat. If you try rubbing it down you will rub through it and have to start all over again. If you need to get rid of marks or runs, apply an undercoat of another colour and rub that down until you see the etch primer. If it is still not good enough, apply another coat of a different colour primer, allow to dry fully and then rub down again, until you see the original primer colour. This keeps the coating thickness to a minimum. Hope that helps, and good luck with the painting.

Bob.

[delaplume]

Dec 9, 2018 18:35:15 GMT 92220 said:

Hi Roger. Paul is correct. Don't sandwich paint in between riveted, or bolted, surfaces that have to be tight. Always use metal to metal contact. Over time a trapped paint coat would fret and thin and the joint would become loose. When painting the frames, paint the red first and then the black. Black will cover Red but Red won't cover Black. Because the joins between Black and Red, on the insides of the frames, are hidden, great care is not necessary in obtaining a perfect join between the Red and Black. A small overlap will be hidden. Alan is right about the use of hex heads too, though if they are long enough for the head to stay well proud of the surface, the adverse effect on the spraying would be minimal. As far as drilled holes go, I would just run a size drill through the holes to clear any paint residue. Fiddly but you can be sure the hole is to size, and not got a small blob of missed paint inside it. When I painted my fully assembled loco frames back in 2002, I gave them a coat of rust stabilising primer (Corroless S); allowed that to dry for 10 days, and then applied the top coats. The advantage of Corroless S is that it will kill any rust that may be lurking there, and prevent rust from starting, even if the paint is scratched, as long as it isn't a wide scratch. Don't know how it works but I used to sell loads of it for boat trailers and caravans. Although it specifies 2 coats, one thin coat works fine as long as there is no obvious rust. By that I mean if it hasn't penetrated the surface of the metal (which is unlikely with your loco!!!!). The frames can be primed with 2-pack etch primer which give a very thin coat, and it will cover both ferrous and non-ferrous metals. Allow to dry for around 72 hours, for all solvents to evaporate, before applying the colour-coats.

As far as how much to paint in one go, paint the inside surfaces and allow to dry and harden, then mask and paint the outside surfaces. When putting subsequent coats of paint on, either spray the second coat before the first is still tacky (that allows the 2 coats to become one single coat with no intercoat adhesion problems, or allow the first coat to dry for at least 24 hours before applying a second coat.

If you find you have to rub down an etch primer coating, DON'T, as long as it is a complete coat. If you try rubbing it down you will rub through it and have to start all over again. If you need to get rid of marks or runs, apply an undercoat of another colour and rub that down until you see the etch primer. If it is still not good enough, apply another coat of a different colour primer, allow to dry fully and then rub down again, until you see the original primer colour. This keeps the coating thickness to a minimum. Hope that helps, and good luck with the painting.

Bob.

--- as above .. I forgot to mention about the Red on Black effect which is good advice IMHO.

Alan 

[JonL]

I use a toothpick in threaded holes.

[Roger]

Many thanks for all the advice, although I'm not convinced on the metal to metal joints. Surely the risk of rusting in the joint is going to be an issue? If the paint is just a two pack primer and allowed to thoroughly cure, is that really going to be an issue?

[mbrown]

Roger - why would you get rusting between the joints? I would have thought the edges of the joints would be sealed by the outer layer of paint, if you follow me. How would moisture get in?

When I dismantled by Bagnall - painted in 1983 and never taken to pieces until recently - there was no rust whatever between faces that had been assembled before painting (not that I stripped it down as far as taking the buffer beams and frames apart, I admit).

Malcolm

[Roger]

Dec 9, 2018 21:27:13 GMT mbrown said:

Roger - why would you get rusting between the joints? I would have thought the edges of the joints would be sealed by the outer layer of paint, if you follow me. How would moisture get in?

When I dismantled by Bagnall - painted in 1983 and never taken to pieces until recently - there was no rust whatever between faces that had been assembled before painting (not that I stripped it down as far as taking the buffer beams and frames apart, I admit).

Malcolm

Hi Malcolm,
Well, there's going to be moisture and oxygen in the atmosphere when you assemble the bare metal, so won't that potentially cause rust?

[coniston]

Hi Roger, as Malcolm says there is really no possibility of rust forming between the mating surfaces. in both the clubs I belong to we have passenger trolleys that were constructed many years ago and painted after assembly, probably with much less care than you will take on your loco, there is no sign of any real corrosion problem with them. IMHO you will give yourself more problems of fretting/loosening by painting the mating surfaces than the minute risk of corrosion. When I rebuilt a Torquay Manor some 10 years ago I left all the riveted parts assembled for obvious reasons. There was no sign of any paint between the surfaces and there was no sign of any corrosion. I used 2 pack automotive etch primer which was actually a filler/primer. This allowed me to flat it off with wet and dry used wet with soap to stop clogging. This gives a lovely smooth surface for the top coats so less work towards the end of the painting process. The insides were painted with top coat first, with red followed by black (typical GWR), then masked with brown paper and masking tape so the outside could be done. I cleared the holes with taps or drills after painting rather than masking, but I did spread Vaseline on the horns and sliding surfaces before the primer. When finished I could then just wipe the painted Vaseline off with very little difficulty. Hope this helps.

Chris D

[delaplume]

Good point about the grease ( Vaseline )..

I don't know about brown paper but each week the Council deliver a local, "freebie" newspaper which is ideal for masking-off ...and E-Bay wrapping as well so I get through a lot !!... Isn't that nice of them ??

[Gary L]

Dec 9, 2018 22:08:39 GMT Roger said:

Dec 9, 2018 21:27:13 GMT mbrown said:

Roger - why would you get rusting between the joints? I would have thought the edges of the joints would be sealed by the outer layer of paint, if you follow me. How would moisture get in?

When I dismantled by Bagnall - painted in 1983 and never taken to pieces until recently - there was no rust whatever between faces that had been assembled before painting (not that I stripped it down as far as taking the buffer beams and frames apart, I admit).

Malcolm

Hi Malcolm,
Well, there's going to be moisture and oxygen in the atmosphere when you assemble the bare metal, so won't that potentially cause rust?

Hi Roger

You could always try the boatbuilder method of bolting things together on a layer of wet (or soft) paint or primer. That will keep out the water, but it can get devilishly messy! But I agree with the others, you shouldn't get any trouble if the paint coats cover all round every joint.

However, if you are going to spray your frames, inside and out, you might get a nice finish (which you won't see for long, because oil, mud and track rust will soon see to that) but you will have trouble with the spray not giving a decent coat in crevices and retreating from joints and edges. It is even surprisingly difficult to spray every facet of every nut and bolt. I always brush-paint frames and castings for this reason. If you turn the frame assembly horizontal and paint the two upper surfaces one day, then turn it over to do the next two and so on, you should get a tolerable finish, and every nut and joint should have a nice fillet of paint to seal it. It isn't quick, but it can be a lot more more thorough.

HTH

Gary

[JonL]

I've worked on a lynx aircraft that had been recovered some years previously after a deep trip in some salty water, and strangely it showed no signs of corrosion. I was expecting it to be leeching from all sorts of joints.

[Roger]

Many thanks for all of that, it's evidence that I was looking for when it comes to rust. I really like the idea of vaseline, or presumably any grease, to keep the paint off bearing surfaces.

I'm not keen on hand painting the frames, I think I'd prefer to spray those. If the odd nut on the inside is missed, I wouldn't object to touching that up with a brush, but not on the outside.

[RGR 60130]

I'd go for metal to metal assembly every time because I don't see the point in trying to produce components thou perfect and then daubing ten thou of paint on them before assembly. You'd be surprised at how well close fitting bare surfaces can remain rust free, even in a marine environment.

Reg

[mr swarf]

I agree with previous posts about having metal to metal contact. To help avoid the paint from pulling back at the joint put a slight radius on the edge. It doesn't need to be much, just enough to take the sharp 90 degree edge off.
Paul

[Roger]

I suppose ships of old were riveted metal to metal and then painted, so presumably it wasn't a big issue for them or we'd know about it. I'm now convinced that this is the way forward. Much as I don't like the idea of bare metal in that situation, it would appear that you can exclude moisture and oxygen from the joint with paint.

I like to explore each issue before making a decision because far too much is done without the evidence to back it up in my opinion. I don't think it hurts to ask the questions and bring together all of the experiences we can draw upon.

[Deleted]

I've gone metal to metal... paint can upset critical dimensions if a number of painted parts are assembled after painting. I don't see any bare metal parts in-between being an issue. The paint will seal the joints and once in service there will be plenty of oil about to keep things protected.

Pete

[RGR 60130]

An excellent example of metal to metal flanges is found in certain electrical fittings (typically Ex-d) for use in hazardous areas. These must not ever be sealed between the flanges or have paint applied over the outer edges. Thousands of them are currently in use on Oil & Gas installations all over the North Sea. If corrosion did occur then the flame path would be compromised. They are inspected on a regular basis and while an odd one will need replacing, the majority last for years. For a bit more reading see this simple explanation:

www.sourceiex.com/Catalogs/Chapter%2012%20EX%20Protection%20Techniques.pdf

Reg

[ettingtonliam]

In the 1950s it was common practice for the faces of bolted joints in structural steelwork to be given a coat of red lead primer, then the joint bolted up while the paint was still wet. Having had to take some of these joints apart 40 years later, even with all the bolts out, it took some force to part the joint. With the advent of the high strength friction grip bolt some years later, joints for these had to be clean bare metal, although where the members were painted prior to assembly, the paint film was allowed to overlap the joint edges by 50mm all round.

[Roger]

Although it feels like a backward step, stripping the paint from the 'finished' buffers, I've looked at the photos of 1501 again and can see some changes that I can easily make now it's back to bare metal.

In this picture you can see that the coupling hook is pretty tall, and the square hole in my buffer could be bigger to make the coupling stronger. It's currently 3/16" square, so I'm opening that up to 5mm x 7.5mm high. Scale would make it about 4.5mm wide, but I can use 5mm gauge plate for the hook which will make it much stronger. It would be over 8mm high anyway, so it will still sit back against the face and look pretty much the same.

If you look at the top of the buffer edge, you can also see that there's a sheet metal top that comes right to the back edge of the buffer. that's not how it is as the moment on the buffer. I can easily put a rebait on the top face of the buffer and then use some 0.6mm thick sheet to end up with it looking like it does on 1501. I'll need to model that and add clearance pockets for the cosmetic bolts that come through and would make the sheet stand off the surface.

20140204_112616 by Roger Froud, on Flickr

Anyway, this is the revised 3D model...

Modified front buffer beam by Roger Froud, on Flickr

... and here is the square hole being turned into a bigger rectangular one.

20181210_213949 by Roger Froud, on Flickr

[delaplume]

Hi Roger,

That's a treadplate for putting you wee booties on when climbing onto the bufferbeam / smokebox access.....

It should have a diamond pattern on top......

There are castings available on the market---I think Polly do them in the Penrose Grange loco..

Best regards from a bloke who used to slip on those damm things when they were wet !!

Alan

Extra}--- On the buffer main body ( or stock ) the 4 small bolts are compressing that thin steel plate you can see between the buffer stock and the buffer beam.....Under the plate and on top of the buffershank is a very STRONG spring...

In the Workshops we use a press and jig .....The plate and spring are compressed and the 4 small bolts then hold the assembly together...

The assy is then taken to the locomotive  where .it is mounted onto the bufferbeam  where the 4 large bolts finally secure the whole assy together...

Alan..

[Roger]

Dec 10, 2018 22:35:33 GMT delaplume said:

Hi Roger,

That's a treadplate for putting you wee booties on when climbing onto the bufferbeam / smokebox access.....

It should have a diamond pattern on top......

There are castings available on the market---I think Polly do them in the Penrose Grange loco..

Best regards from a bloke who used to slip on those damm things when they were wet !!

Alan

Extra}--- On the buffer main body ( or stock ) the 4 small bolts are compressing that thin steel plate you can see between the buffer stock and the buffer beam.....Under the plate and on top of the buffershank is a very STRONG spring...

In the Workshops we use a press and jig .....The plate and spring are compressed and the 4 small bolts then hold the assembly together...

The assy is then taken to the locomotive  where .it is mounted onto the bufferbeam  where the 4 large bolts finally secure the whole assy together...

Alan..

Hi Alan,
Do you mean the step piece on the buffer itself, because that has dimples, not a diamond pattern. I've already made those.

At the moment, my buffer stocks have that flange piece as one, but I might modify that to give the impression that it's done the way it is on the full size. It would certainly look better. Now's the time to do it really.