Thanks All
Jerry raises a couple of very important points, especially the ones about friction. For all intents and purposes, I don't need the O-rings; in fact, I initially planned to go without them. From the first run of the engine, it was quite clear that there was very little blow-by past the valves, and the use of a thick lubricating oil on them will help reduce that to practically zero.
If the O-rings give me problems, I'll replace them with PTFE tape - that's what I'm using on the piston rod gland. Graphite string would be better, but that's unobtainium in Namibia; I'll get some from overseas at some point. The advantage of the tape/string is that one can add or take away bits to make things work better.
Anyway, for Vince and others' benefit - If you do make the valves a close but free-running fit in very smooth bores, you pretty much don't need packing of any kind for the valve bonnets, nor the
Oh, and I shudder at the thought of trying a fiddle... I'm pretty sure it'll sound like someone trying to play the bagpipes
I had a job to do at a client's site this morning. After a pretty hectic week at work, where nothing turned out to be quick or easy, I expected this one to follow suit, but, amazingly, it turned into a fairly quick and easy job. So I had the opportunity of a bit of unexpected shop time. With all the engine parts (except for fasteners) made, I disassembled everything - well mostly. In keeping with trying to work a bit tidier, I salvaged an old cutlery tray from the kitchen to keep the parts together. I kept all the bits that needs painting separate:
The one part out of place in the photo above is the valve disk... I was trying to decide on whether to re-make it, or try and tidy up this one a bit and use it as-is. Well, as you all know, I'm lazy and I quite like the thinner middle appearance on it, so I decided to keep it. After some careful filing it looks a bit more presentable. I forgot to take a photo of it, so I'll do that for the next post.
With the time that's elapsed since this build began, most of the steel parts have developed a light layer of surface rust. Either I should have been more careful about oiling them up, or I should have painted them as I built them - at least with primer. As I did neither, there was a bit of elbow grease required, so I started rubbing off the rust with a bit of Scotch-Brite (the fairly coarse green one sold as house-hold pot scourers locally) - to get rid of the rust, as well as to provide a key for the primer:
Next up was an impromptu spray booth. I cobbled together a make-shift structure with odds 'n ends... Two square tubing side-frames I had floating around (those were originally made ten years ago and were to be part of a removable bottom for Shrek's cage), some rectangular PVC trunking I had left over from installing telephone cabling in my house when I moved in, all tied together with electrical insulation tape and covered with split apart plastic refuse bags - with some old newspaper as a bottom. Not pretty, but functional:
I mentioned in the last post that I bought a new spray gun. It's nothing fancy; a cheap & cheerful Asian made one (cost about US$ 35), but on the surface of things, it appears acceptably made and all the adjustment screws and trigger operate fairly smoothly. I do have another spray gun, but it has a 1l cup at the bottom, and for trying to spray models, it's much too big. The bottom cup leaves nearly enough unusable paint left over in it when empty to just about spray a complete model. The new gun has a 120ml cup at the top, which means its easy to mix up and use small quantities of paint. This is the spray gun:
An airbrush may be more suited to this kind of work - I do have one that needs a bit of TLC, as all it's O-rings and so on have perished, BUT, most airbrushes only works well with thin paint. The "filling" etch-primer I have for this project needs a more robust spray gun for the higher viscosity paint.
I spent some time masking of various bits of a selection of the parts with ordinary paper-based masking tape. There are better products out there for masking off things, but I used what I had on hand. Some bits were lightly pinned to blocks of wood with brads through mounting holes to keep them in place. The bearing pedestal was just shoved on a bit of bent brazing wire to make a "handle" for it while painting; the handle to be used to hang on a hook to dry. The cylinder cover was literally just stuck to the wooden block with more masking tape. For the two bearing blocks, I just used an 8mm bolt in each with masking tape wrapped tightly around to keep them in place and to protect the edges of the bronze bushes from paint. All of this was just that there was some way to handle the bits while painting to get at all sides, and also to safely store it for drying:
None of the pieces shown have any holes with threads in them, so I didn't bother to plug the holes. It will be easy enough later on to clean paint from the holes with a drill bit...
After a last wipe-down with bits of my plentiful "John Wayne"(*) shop toilet paper lightly soaked in thinners, on to a bit of paint. And all of this was VERY new to me... Seeing as the spray gun was new, I ran about half a cup full of clean thinners through it spraying at a bit of cardboard. I tested the different controls on the spray gun to test what they were used for and how they responded. The clean thinners was just to make sure the gun was thoroughly clean before I tried paint.
Eventually I mixed some of the primer with thinners according to the instructions in a separate clean empty jam bottle. The instructions said 30% - 40% thinners to paint; I opted for the more viscous option because of the relatively small spray gun and went for 40%. A quick test on a bit of scrap plate, and with some fiddling with the controls I got a passable result, so I went ahead and sprayed all the bits.
I've used rattle-cans to varying degrees of success in the past; in fact, most of the painting I've done on models thus far have been done with rattle-cans (with some free-hand brush painting making up the rest). In all cases, tying to get a nice and even coat of primer on them proved to be very difficult, with quite a bit of work needed afterwards to smooth things with wet & dry, or in many cases a complete strip of all the paint for a retry. I found applying the paint with the spray gun was much easier. It gives greater control, and things turned out pretty well. As I finished each lot I stuck them in the old oven Don mentioned in my shop revamp to dry off:
No heat or anything; it's just a nice and dust-free place to store them.
This paint dries pretty quickly; on my test plate it took just 15 minutes to be completely touch-dry - it was a nice warm day today at about 32
oC with a smidge of humidity. So after about an hour I took the bits out of the "oven" for some photos.
I've mentioned before that I don't like painting things, but it's one of those things that needs to be done. Most of Elmer's engines looks great without any paint, but some colour does add character. On a bigger model like this it's part and parcel of the build.
Please pardon my enthusiasm...
Of all the primer paint jobs I've tried so far on engines, this was by far the easiest, with the most satisfactory results straight-away.
It easily covered in one thin coat, but did not tend to draw away from any sharp edges like I've always had. And the "filling" part of this primer also looks to be doing well; it covered toolmarks and went into corners very well and pretty evenly:
And
That was the shop session for the day - and quite satisfying at that
Kind regards, Arnold
(*) "John Wayne" shop toilet paper: It's rough and tough and takes crap from no-one. Non-perforated industrial toilet paper supplied on big rolls. Doesn't tear or fray easily.
