The primer is now sorted and the next problem is a paint that will stand the heat of the smokebox. What I want is a black paint that will give a semi-gloss finish and hopefully I can also use it for the outside of the frames and the cylinders.
There are a number of possible paints for this job varying in their temperature range. Various manufacturers make very high temperature paints for car exhausts, barbeques, cast iron stoves etc. but a lot of them are not very black, more a grey colour. One possibility I've looked at is high temperature enamel designed to paint car engines with and it just so happens Halfords sell a range of this which is supposed to withstand 300°C. They do a satin black version so I bought a tin to try it out. It can be sprayed if thinned down with white spirit but initially I just brushed it on.
Using the piece of brass I had previously etch primed I covered a third of it with the satin black and let it dry naturally for a couple of hours. The finish was about the right semi-gloss I was after so into the oven it went and 'baked' at about 250°C for an hour. After this the paint was still pretty tough with no signs of flaking but it had dulled down quite a lot and now looked matt rather than satin. Hmmm.
Halfords also do a gloss black version so I had the bright idea of mixing the gloss and the satin 50/50 to see what happened. Off to halfords again ( they are only a mile or so down the road) and returned with a tin of the gloss. Another third of the test piece was then painted with a mixture and the heat treatment repeated. Although the unheated paint looked fine, after heating it had actually turned grey so perhaps the two paints are not compatible?
Out of curiousity I painted the last third of the test piece with the straight gloss and after the obligatory heat treatment it actually looks perfect! A nice dull gloss which should look the part. If I do decide to go ahead with this paint and use it for the frames as well, I may cook the frames in the oven to produce the required level of gloss. The smokebox will probably sort it's self out after a few steamings! I believe that Precision Paints suggest painting a smokebox with their gloss black enamel which will then dull down when the loco is steamed. I do know some-one who has done that but I have my doubts whether ordinary enamel will stand the heat on Helen's smokebox as she runs very hot when working hard.
The high temperature enamel is also available in gloss red which I may use for inside the frames and the boiler fittings in the cab. The front section of the frames get pretty hot due to the three cylinders which run at well over 150°C.
For the top coat of olive green I've eventually gone for Precision Paints enamel alhough my initial idea was to try and find a paint from elsewhere which may have worked out cheaper. However, looking around, it would seem that the minimum quantity you can buy from most car paint suppliers is 1 litre which will be far more than I need and I had visions of most of the paint going to waste.
I did actually buy a spray can of the Halfords acrylic car enamel to try and it went on very well. Unfortunately, although the finish was pretty tough when cold, it went very soft when heated to 150°C and was very easily damaged. You may have realised by now that I'm trying to source suitable paints from local suppliers rather than have to track down specialist ones. In the small quantities I need for Helen I don't think it's worth the time and trouble but probably would be for a larger loco.
Anyway, I seem to have sorted the paint out so the next job is to devise some sort of spray booth to do the painting in. I'm not very impressed with the usual small open fronted ones that many people seem to construct which have a fan in the top or side to extract the paint fumes. Although they may be fine for extracting the paint and fumes, they will also pull all the dirt and dust from the air into the booth and no doubt deposit it all over the nice wet paint!
Another alternative is the much larger booth that you actually stand inside with a fan to blow in filtered air and an outlet for the paint and fumes to escape. I don't really fancy making one of those as I haven't really got the room for one that big. I haven't got a garage or suitable shed to put it in anyway. One thought is to make a smaller sealed booth with arm holes in the front so that you stand outside but have your arms inside to operate the airbrush etc. This design appeals to me but the problem will be to seal the arm holes and still allow plenty of freedom to move your arms from side to side when spraying. Watch this space!
I've now cobbled up a sort of spray booth using whatever materials I had to hand. I've not made it completely sealed yet and will try it as it is first. The base is a 3' x 2' piece of MDF and the ends are two scrap doors of a kitchen unit! Another piece of MDF forms the top which has a hole cut in the centre to take a 4 inch ceiling fan such as fitted in bathrooms etc. That was also salvaged from a job I did for some-one earlier in the year. The back and sloping front are made from a thick clear plastic film that I had lying around. The booth sits on one of the kitchen worktops in front of one of the windows which just happens to have an old extractor fan fitted (one of those self powered ones that is supposed to suck out when the wind blows it round but doesn't!). I removed the window fan and the exhaust from the fan in the booth exits through the hole in the glass via bits of pipe and a couple of elbows normally used for drains.
The improvised spray cabinet
The front of the cabinet is open at the moment which makes access for spraying easy but may also allow dust etc to get inside onto the parts being sprayed. I can always seal the front somehow if this becomes a problem.
The extractor fan seems to be adequate and does remove most of the fumes and overspray but could with advantage be a bit more powerful I think. Although very little overspray escapes from the cabinet I would not advise spraying without a mask, especially if using some of the two part paints that use nasties such as isocyanates. Better to be safe than sorry and use a mask with the appropriate filters for the type of paint you are using.
Since finishing the cabinet I've been experimenting with the tinned etch primer that arrived the other day. I've tried spraying it unthinned, thinned, and using both airbrushes. It did not spray very well unthinned (although it is quite thin straight from the tin) and gave a very grainy finish due to it drying too quickly and not pulling out level. It gave much better results when thinned 5 parts primer to one part thinner. I tried various thinners as it does not mention thinning the paint on the tin and had mixed results. White spirit seems to work for thinning the primer but the primer dries very soft and is easily scratched off. It is possible that it just needs a lot longer to dry but I did not pursue the white spirit any more. Synthetic thinners spray and dry ok but you have to be quick cleaning out the airbrush as the primer starts to go gooey after a short time. To be fair, a lot of these etch primers do need a special thinner so I was not surprised at the results so far. I happened to have a small quantity of the Precision Paints special etch primer thinners that some-one gave me and using that gave good results. The synthetic thinners are fine for cleaning out the airbrush afterwards though and probably the cheap thinners sold as 'Gun Wash' would be ok as well.
After sorting the thinners out I tried spraying the primer with the cheapo airbrush and could not get a decent finish with it despite trying different air pressures etc. I then had a go with the Badger 175 with some improvement but it still wasn't perfect and the brush seemed to be putting too much paint on (I also found this with the high temperature enamel). I had been using the medium needle and spray jet which was recommended in the instructions for thinned paint (the airbrush comes with three sets-fine, medium, and large) but I decided to try the fine needle/jet combination which is recommended for spraying inks. This made a vast improvement and made it a lot easier to put a nice thin layer on. Probably the smaller jet was giving better atomisation of the paint and a much finer spray. Incidentally, the primer dries out to a lot thinner layer than the wet primer would have you believe.
I'm now at a point where I feel reasonably happy to start painting the frames. I've changed the plan of action here and am now going to fully assemble the frames before priming. This should make the overall job easier as all the csk head screws can be filled and sanded before painting and the alignment of the frames checked and adjusted. I think if I primed the bits first I'd no doubt damage some of the paint during assembly and probably get greasy finger prints over it all meaning I'd have to degrease everything again with the risk of fetching the primer off with the solvent. There would also be the hassle of having to prime all the individual nuts and bolts after assembly!
I've reassembled the frames,checked the alignment, and filled in the csk screw heads along with any dings around the horns where I missed with the hammer when rivetting them in! There were a few tapped holes now surplus to requirements and these were filled with bits of threaded rod loctited in and then filed flush. I've also made a couple of mods to the frames:
The holes where the steam pipes to the outside cylinders pass through have been enlarged to cater for the new threaded joints. The steam manifold will be threaded 3/8"x40 for new steam pipes so the holes have been made a clearance size for these. Basically, the steam pipes don't need to be this big at the ends but it means I can just thread the bore of the old steam manifold and not have to make a new one!
I've also moved the holes that take the securing bolts for the reverser further back from the boiler to give more clearance between the reverser handle and the blowdown valve on the water gauge.
I've decided to fit the cylinders after the frames are painted and the cylinders will be painted separately before fixing which will make it easier I think. There is a slight problem doing this with the middle cylinder as if the bolting faces inside the frames are painted, the cylinder will not fit due to the thickness of the paint! What I'll do is mask off the small section of frames where the cylinder fits and then paint this by hand after the cylinder is fitted. To be honest, all the inside surfaces of the frames could be hand painted as hardly any of them can be seen once the boiler and tanks are fitted and a few brush marks are not going to be noticed. I'll try spraying on the primer and see how easy it is to get inside with that.
To make turning the frames over for painting easy I've cobbled up a quick stand that holds the frame by the buffer stocks. It's basically the carrier that I've used for transporting Helen to the track with a couple of bits of wood screwed to the handles. Two lengths of square tube pivot on a bolt through the wood and each tube has two bolts which fit into the buffer stocks. It works quite well and will probably serve as a building stand when the rest of the bits are reassembled onto the chassis.
Chassis mounting in stand ready for painting
The only problem is that the stand is too big to fit into the spray booth so I think I'm going to have to spray the frames outside in the fresh air. With them being such a complex shape to paint I need to be able to get at them from all angles so I need plenty of room to move around anyway. Frankly, I'm not bothered about a few bits of dust getting on the paint for the frames as they will hardly be glaringly obvious, unlike on the boiler and tanks.
Last night I stripped the cylinders and cleaned them up ready for painting and found one or two problems. One cylinder had a lump of O ring inside which must have come from one of the steam manifold seals, and on all the cylinders the Peek bushes for the piston rods fitted in the rear cylinder covers had come loose. One of the bushes for the valve rods had also come loose. The bushes all seem very tight on the rods and I reckon they have expanded with the heat and then seized on the rods, causing the bushes to be forced out of the housings. The bushes coming out have also allowed the O ring seals to come out and one was badly damaged. Obviously a redesign is needed here to prevent this happening again. The easiest thing to do would be to fit bronze or gunmetal bushes instead I suppose, or make new Peek bushes but with greater clearance on the rods.
Two of the three piston O rings look quite worn although the bores are nice and smooth. It is possible I've made them too tight a fit so I'll check that on reassembly. It could also have been caused by the early problems with the lubricator when they could have been running without oil.
Went to the club at Whitwick today for the usual Thursday working session but spent most of the time trying to sort out an ailing ModelWorks Black Five owned by Roger, another of the members. He's been trying to sort out the valve timing for months now and today it was no better. After faffing around for a couple of hours he called it a day. I reckon there's something seriously wrong with the geometry of the valve gear and I don't think the valve travel is long enough to open the ports properly. He's hoping to bring it again on Sunday so I'll try and do some measuring up and see if I can find the problem.
When I got home I decided to spray a coat of the etch primer on the chassis and so make a start on the painting. As mentioned above, it was too big to fit in the spray booth so I sprayed it outside under the car port. It's actually fairly sheltered by the fence so it wasn't too draughty. I was glad of the room as it involved spraying from all angles to get in all the nooks and crannies inside the frames. I concentrated on the inside the frames first doing one section at a time and finishing that before moving onto the next bit. The revolving stand was a real help and enabled the frame to be turned around to get at the top and bottom of the frame plates and stretchers. When the inside was finished, I moved on to the outside which was quite easy in comparison. The spray from the airbrush is quite fine so it's possible to build up the coat gradually using several passes without causing runs.
The finished job doesn't look too bad at all and I seem to have got a nice even coat with no runs. There's a few bits on the paint surface but on the whole the finish seems ok. I'll have a close look tomorrow when the primer is properly dry. Any defects can be sorted out with some very fine carborundum paper.
Frames after priming
For painting the wheels I made a simple jig from some bits of wood and a couple of screws which locate in the centres in the axles. This enables the wheels to be easily rotated as they are painted.
Wheel painting jig
The wheels and axles were sprayed with the primer after masking off the treads and then the wheels painted by hand with the olive green enamel. The wheel rims will be painted black.I thought it would be easier to hand paint the spokes etc rather than use the airbrush. The enamel went on very well and flows out well leaving a nice flat finish. I think the spokes will need another coat though as the primer shows through in a couple of places.
Wheels after one coat of enamel
One point to mention here is that it is essential to thoroughly stir the paint before it is used. This ensures that all the pigment is mixed properly and the paint comes out the intended colour. Stiring by hand with a thin rod or a screwdriver is not good enough and it's best to use some sort of electric stirrer. For the smaller tins of paint I used a bent piece of 1/8" wire held in the chuck of the milling/drilling machine. This could be lowered to the bottom of the tin and left running for a couple of minutes until the paint is well and truly mixed.
Bent wire paint stirrer
Stirrer in use
The litre tin of primer was too tall to fit in the mill/drill so I used a similar but larger stirrer held in the cordless drill.
Next I had a go at the cylinders and to make holding these easier I used a couple of bits of brass bar threaded to fit in the steam inlets for the outside cylinders, and a piece of wooden chopstick jammed in the exhaust port for the middle cylinder. These could be stuck in drilled holes in a block of wood after painting while the paint dryed.
The ends of the cylinders and valve chests were masked off with circles cut from sticky labels and then the cylinders were sprayed with primer. They were then hand painted again using the Halfords high temperature paint, gloss black for the outside cylinders and red for the inside. The red is quite 'bright' but not too far away from the buffer beam red enamel that I bought from Precision Paints. You don't see much of it anyway when the boiler and tanks are on the frames so the colour doesn't really matter that much! They will need a second coat as the paint does not cover or flow as well as the Precision enamel.
Cylinders masked and primed
Cylinders after one coat
I've decided to fit alloy covers over the cylinder end covers and the valve chest covers as in full size practice. Although this means more work, it means that the end covers and the fixing bolts do not need to be painted (except for the bits that will show) and it will be possible to retighten any bolts that come loose without damaging any paint. I've found that the end cover bolts usually need retightening after the loco has run a bit. Also the front valve chest covers can't be fitted until the motion has been reassembled and the valve timing reset.
Next job is to get the frames top coated so that I can start to reassemble the wheels and motion work. I am not sure whether to hand paint the inside of the frames as this may be a lot easier than trying to spray it. As mentioned, you can't see the insides anyway so I'm not too bothered about getting a super finish. I don't see the point in wasting time and effort getting a really good finish on bits that you can't see! Life's too short. Apart from that, it's only 3½ weeks to the first steam up!!
My apologies for the lack of updates recently but time has been a bit short over the last month or so. Work has progressed slowly but not as fast as I would have liked! Photos are a bit lacking over the next stages as I didn't get around to taking very many so you'll have to use your imagination a bit!
The frames were masked off to protect the insides and the outsides then sprayed with the Halfords satin black using the airbrush and two good coats. The satin black gives a nice sheen to the frames without being glossy which I don't think would look right. The paint was left to dry for a couple of days and the masking tape removed to allow the insides of the frames to be painted. I did this by hand using the halfords high temperature red, again giving two coats. This was again left for a couple of days to dry. In the meantime some of the smaller bits such as the hornstays, axleboxes, two to one lever, etc. were either sprayed or handpainted. I also hand painted the rims of the wheels using the Precision Paints gloss black enamel. I had toyed with the idea of putting a white line on the rims as well but I think they look ok as they are. The paint on the rims is bound to get scuffed and chipped with use so the simpler the colour scheme the better to allow touching up as necessary.
I could now start to reassemble the chassis starting with the wheels and coupling rods and the water pumps. Before refitting the cylinders I had to turn down the outsides of the cylinder and valve chest end covers to accept the aluminium covers. At this point I also decided to replace the O rings on the pistons with PTFE rings as another experiment to see how they would perform. The intention was to leave the grooves in the pistons as they were so that, if necessary, the O rings could be refitted. The new PTFE rings would be made to fit the existing grooves.
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