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Post by fubar123 on Mar 25, 2021 18:22:43 GMT
Would a good soaking of thin laminating Epoxy Give the MDF a more stiffer structure prior to the finishing of the form ? Really enjoying your thread Chris
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Gary L
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Post by Gary L on Mar 25, 2021 19:38:04 GMT
Two Photos in one for you Gary. Didcot 2015 Feels like yesterday! David and Lily. Thanks David and Lily; that's oddly useful, because the latch on the filler hasn't been secured properly- so it is possible to see some parts of some parts that are not normally visible- like the cam profile on the handle Gary
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Gary L
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Post by Gary L on Mar 25, 2021 19:52:55 GMT
Some great stuff going on in this topic! Sympathies for the spinning failure, it looked like it was going well and was getting a good result. I was confused as to the shape that was coming out near the top of it until you explained what happened. That looks like a very labour intensive way to make the top of a clack valve. The design on my loco is just has a 1/16" pin or 10BA screw through the body to stop the ball reaching and blocking the outlet. I've had the loco at least 10 years and have never noticed either a noise or a problem coming from it. Hi David Indeed, me neither. I was attracted to Martin Evans's design because it seems to offer minimal flow restriction and it really wasn't diffcult to make- almost worth it for the interest. Also I just don't like the cross-piece that doesn't have a positive seal (though they seldom if ever leak in practice, and I have several examples on Paddington already). But I hadn't reckoned on this annoying behaviour of the ball. I think there must be an eddy current created as the flow escapes from the valve seat into the ball chamber. There wouldn't be much hope of stopping the eddy, but it might be possible to devise a simple trap that catches the ball and stops it joining in the fun. However I don't know if it will be necessary. It only occurs when I blow as hard as I can down the pipe. If the boiler feed water flows at a more modest pace, it probably won't arise. It might be made a little worse because the Carbide balls are noticeably lighter than stainless or bronze, so more prone to bouncing around. I wonder if anybody else has tried the Martin Evans design? Gary
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Gary L
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Post by Gary L on Mar 25, 2021 20:02:46 GMT
Hi Gary, I looked at the pictures and thought that's an interesting bit of spinning so I added my like to the post. But I went back and read the text and realised it was not a success, although lessons were learned. So I didn't want you to think that my endorsement was provided because it was a failure and an attempt to rub salt into the wounds. Quite the contrary. Good luck with the second attempt. Brian Hi Brian and Nobbysideways Thanks for the commiserations; it's a pain but I should have known better. I didn't mind telling this little story against myself, because reading this thread I was aware that I was giving the impression that everything always goes to plan and nothing ever goes wrong. If only that were true! We can all learn from mistakes (some say we only learn from mistakes, but I don't believe that) but it is always cheaper to learn from someone else's mistakes! Spinning is a black art and I've heard of lots of people who didn't succeed after a few attempts and gave up. But if you start from the right place (like a decent chuck!) the learning curve won't be so steep. Gary
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Gary L
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Post by Gary L on Mar 25, 2021 20:15:02 GMT
Hi Gary, Personally, I'd call that a success. You've learned what works and what doesn't. Now you're in a much better position to make the next step. Even if that doesn't turn out exactly how you planned, you'll probably have learned enough to nail it the next time. This is the sort of thing that I really enjoy, battling against the odds but finally coming out on top. I don't think extracting a mandrel is going to be impossible if you need to do that. Boring a really large hole in the middle will allow it to be collapsed into that space with care. Keep up the good work, it's most interesting. Hi Roger No, it's a scrapper. The softness of the former/mandrel/chuck (call it what you like) is what caused the failure. When you have formed the metal dead to the surface of the chuck, you can feel a vibration in the tool. It was the lack of vibration that made me keep pressing with the tool, not realising that I had gone significantly under diameter and was still going when the chuck broke off. Newcomers to spinning will be quite surprised at how tightly the metal will grip the chuck, even when there is a significant 'draw' on it as here. But the odd scrapper is all part of the fun... never try spinning without some spare blanks though, we amateurs are not likely to get everything right at the first attempt. Gary
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Gary L
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Post by Gary L on Mar 25, 2021 20:24:10 GMT
Very interesting indeed. I am keen to know how you achieved enough friction to drive the brass disc with only the pressure from the running centre. When I have tried this for spinning, the disc has simply slipped as soon as I put pressure on it with the forming tool. And what do you mean by "waxing"? I lubricated the brass, but used grease - is that what you are referring to here? Malcolm Hi Malcolm It's why you need a live centre, and a wood block for it to bear on. You have to wind the tailstock in quite hard, until the disc is held firmly. (You do this quite naturally as part of the process of centering the disc at the start). If it wasn't a live centre, the frictional heating would be spectacular! At 1000rpm (or thereabouts) whatever you use to lubricate the brass is going to want to splatter all down your clothes, walls, ceiling... so grease will work fine, but isn't ideal! Experienced spinners used to use soap, but wax seems to be the modern choice. Just ordinary furniture wax works fine: it doesn't fly off the disc, is clean to apply, and (top tip) you don't need to clean it off every time prior to annealing; it just vaporises and leaves no residue HTH Gary EDIT PS. There are limits on the minimum size of the pressure pad; if it is too small (in relation to the diameter of the work) you will never get enough friction for a decent grip, and so you'll need to plan the work differently; maybe using higher-friction materials, or mechanical fastenings or dogs- I don't know, I've never needed anything like that, but you could be inventive. -G
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Post by Roger on Mar 25, 2021 20:26:45 GMT
Hi Gary, Personally, I'd call that a success. You've learned what works and what doesn't. Now you're in a much better position to make the next step. Even if that doesn't turn out exactly how you planned, you'll probably have learned enough to nail it the next time. This is the sort of thing that I really enjoy, battling against the odds but finally coming out on top. I don't think extracting a mandrel is going to be impossible if you need to do that. Boring a really large hole in the middle will allow it to be collapsed into that space with care. Keep up the good work, it's most interesting. Hi Roger No, it's a scrapper. The softness of the former/mandrel/chuck (call it what you like) is what caused the failure. When you have formed the metal dead to the surface of the chuck, you can feel a vibration in the tool. It was the lack of vibration that made me keep pressing with the tool, not realising that I had gone significantly under diameter and was still going when the chuck broke off. Newcomers to spinning will be quite surprised at how tightly the metal will grip the chuck, even when there is a significant 'draw' on it as here. But the odd scrapper is all part of the fun... never try spinning without some spare blanks though, we amateurs are not likely to get everything right at the first attempt. Gary Hi Gary, Sorry, I was referring to the process and the experiment being a success, even though the part ended up not being useful. The finish looks good, and you've clearly managed to deal with the work hardening. I'm sure you'll be able to do this.
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Gary L
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Post by Gary L on Mar 25, 2021 20:35:14 GMT
Would a good soaking of thin laminating Epoxy Give the MDF a more stiffer structure prior to the finishing of the form ? Really enjoying your thread Chris Hi Chris I would say not. It would toughen up the surface a certain amount, as I did with the PVA, but the spinning tools (which are really levers) would still crush the substrate. Normal spinning tools can be up to about 3ft long, with wooden handles which the operator often fits under his arm to apply full bodyweight. We don't need those for the little bits we need on our locos, but this bonnet was the largest spinning I have attempted to date, and my rather puny tools were working at their limit. Consequently I had not made allowances for the amount of extra force that would be exerted on the former. But this was the final nail in the coffin for the MDF. It is very weak in shear, and that is what caused the final break-up. We live and learn... sometimes! Gary
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Post by Gary L on Mar 25, 2021 21:03:15 GMT
Hi Roger No, it's a scrapper. The softness of the former/mandrel/chuck (call it what you like) is what caused the failure. When you have formed the metal dead to the surface of the chuck, you can feel a vibration in the tool. It was the lack of vibration that made me keep pressing with the tool, not realising that I had gone significantly under diameter and was still going when the chuck broke off. Newcomers to spinning will be quite surprised at how tightly the metal will grip the chuck, even when there is a significant 'draw' on it as here. But the odd scrapper is all part of the fun... never try spinning without some spare blanks though, we amateurs are not likely to get everything right at the first attempt. Gary Hi Gary, Sorry, I was referring to the process and the experiment being a success, even though the part ended up not being useful. The finish looks good, and you've clearly managed to deal with the work hardening. I'm sure you'll be able to do this. Yes, it wasn't a total failure, and I thought readers would enjoy the story! Spinning is an oddly satisfying process, so I quite look forward to the odd job. The downside is the amount of preparation needed; everything depends on the chuck, and in the case of this bonnet, there is a huge amount of material to cut away, which is why I will use Nylon next time, rather than going to steel or aluminium. Many people would use wood, but the dust makes such a mess, and you have to be really selective with the grain. The actual spinning doesn't feel like metalwork; it has more in common with raising a pot on a wheel, except that you are using tools, not fingers. You can watch and feel the marks made by the tool flowing across the surface of the work, and then you finish off with a flat tool to planish the marks away and get a smooth surface. You can get quite involved in at and then get annoyed by the interruptions caused by the need to regularly dismount the work and anneal it! People who spin for fun like to use pure aluminium, because it flows well and work-hardens less. Gary
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Post by Gary L on Mar 26, 2021 1:07:20 GMT
Some great stuff going on in this topic! Sympathies for the spinning failure, it looked like it was going well and was getting a good result. I was confused as to the shape that was coming out near the top of it until you explained what happened. [Snip] I probably should have explained that I was following the C R (Roy?) Amsbury method printed in ME 2.2.1973, which involves making two spinnings with a spigot joint just below the top flare. It would probably be possible to spin the shape from one piece of metal, but it would involve a multi-piece chuck and some pretty skilful work which goes beyond what most of us could manage. Incidentally, on admittedly slender evidence, it seems to me that the factory did not spin these items but beat them to shape. (There is a sequence in the Stan Millard 'Castle Class' film of one of these being turned after being shaped, but it appears to be a burnishing operation, not spinning). But that method is surely impractical in miniature.
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Post by Roger on Mar 26, 2021 8:03:19 GMT
Some great stuff going on in this topic! Sympathies for the spinning failure, it looked like it was going well and was getting a good result. I was confused as to the shape that was coming out near the top of it until you explained what happened. [Snip] I probably should have explained that I was following the C R (Roy?) Amsbury method printed in ME 2.2.1973, which involves making two spinnings with a spigot joint just below the top flare. It would probably be possible to spin the shape from one piece of metal, but it would involve a multi-piece chuck and some pretty skilful work which goes beyond what most of us could manage. Incidentally, on admittedly slender evidence, it seems to me that the factory did not spin these items but beat them to shape. (There is a sequence in the Stan Millard 'Castle Class' film of one of these being turned after being shaped, but it appears to be a burnishing operation, not spinning). But that method is surely impractical in miniature. To be honest, I would have thought it more difficult to make the joint between two pieces than to make the tooling and spin it in one.
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Post by Cro on Mar 26, 2021 9:47:38 GMT
I started drawing one of these up a few weeks ago to have printed and cast for a chap doing a 7 1/4” 47 (I think) and my City. I have no doubt you’ll do a great job with the spinning but if you get stuck you know where I am!
Adam
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Post by Gary L on Mar 26, 2021 15:53:31 GMT
I started drawing one of these up a few weeks ago to have printed and cast for a chap doing a 7 1/4” 47 (I think) and my City. I have no doubt you’ll do a great job with the spinning but if you get stuck you know where I am! Adam Thanks Adam, but you and others might be surprised to know that I already have a casting, (though I’m certain it is nowhere near as fine as yours will be!) I’m not keen on castings for this part, because to me they just don’t have the same ‘presence’ as a sheet metal product. The full size ones soon became a bit battered, and in view of the method of manufacture might not have been perfectly round and smooth from the beginning. When polished the difference stands out a mile, and is one of the most characteristic aspects of GW loco practice. That said, it is one of the most difficult items on the whole loco to get right, and one of the most obvious if it is wrong, so I don’t blame anyone for taking an easier route! I can’t help thinking that an expert spinner might find a profitable sideline here! Gary
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Post by Gary L on Mar 26, 2021 16:11:42 GMT
I probably should have explained that I was following the C R (Roy?) Amsbury method printed in ME 2.2.1973, which involves making two spinnings with a spigot joint just below the top flare. It would probably be possible to spin the shape from one piece of metal, but it would involve a multi-piece chuck and some pretty skilful work which goes beyond what most of us could manage. Incidentally, on admittedly slender evidence, it seems to me that the factory did not spin these items but beat them to shape. (There is a sequence in the Stan Millard 'Castle Class' film of one of these being turned after being shaped, but it appears to be a burnishing operation, not spinning). But that method is surely impractical in miniature. To be honest, I would have thought it more difficult to make the joint between two pieces than to make the tooling and spin it in one. I wouldn’t be so sure of that Roger, though ‘other methods are available’ besides spinning. P Stevenson described a method using a series of forming tools and a rolled cone in EIM September 2011, but that requires brass welding so I ruled it out. The makers and repairers of brass musical instruments use a somewhat similar approach, planishing freehand over a conical metal former. But AFAIAC, spinning is just about attainable, but these other methods require degrees of specialist skill and equipment that I will never have. I’m probably not alone! Gary
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Post by mbrown on Mar 26, 2021 16:39:29 GMT
Many years ago, Geoff Nicholson wrote an article in EIM describing the traditional "raising" method of sheet metal work. If you go back far enough to when the Midlands Exhibition was held at Birmingham University, you may remember him demonstrating this and making numerous domes, top feed covers and, yes, GWR safety valve bonnets, from gilding metal.
I followed his methods to make the dome for the Burma Mines loco and, although it took two goes to get it right, I found it quite straightforward if somewhat time consuming. I had to get some kit to do it - an egg-shaped mallet, a raising hammer and a planishing hammer, all of which came from Walsh's who supply jeweller's equipment (and they weren't expensive) - and made myself a leather sand bag.
Somewhere on the What I did Today thread is my description of trying to make the bell for my steam operated bell, first by spinning, which was a dismal failure because I couldn't get traction to drive the disc against the pressure of the tool, and secondly by raising, which sort-of worked, although really needs doing again with a better former.
If I can find the relevant EIM edition over the weekend, I will put the reference on this thread. I certainly think raising is the method Swindon would have used rather than spinning.
Each to their own, of course, but it's always good to have another skill under one's belt....
Malcolm
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Post by stevep on Mar 26, 2021 16:57:57 GMT
I remember seeing his demonstrations at exhibitions, and managed to follow his processes (using copper, rather than gilding metal) for the top feed cover and dome on my Stanier.
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Post by Gary L on Mar 26, 2021 17:23:46 GMT
Many years ago, Geoff Nicholson wrote an article in EIM describing the traditional "raising" method of sheet metal work. If you go back far enough to when the Midlands Exhibition was held at Birmingham University, you may remember him demonstrating this and making numerous domes, top feed covers and, yes, GWR safety valve bonnets, from gilding metal. I followed his methods to make the dome for the Burma Mines loco and, although it took two goes to get it right, I found it quite straightforward if somewhat time consuming. I had to get some kit to do it - an egg-shaped mallet, a raising hammer and a planishing hammer, all of which came from Walsh's who supply jeweller's equipment (and they weren't expensive) - and made myself a leather sand bag. Somewhere on the What I did Today thread is my description of trying to make the bell for my steam operated bell, first by spinning, which was a dismal failure because I couldn't get traction to drive the disc against the pressure of the tool, and secondly by raising, which sort-of worked, although really needs doing again with a better former. If I can find the relevant EIM edition over the weekend, I will put the reference on this thread. I certainly think raising is the method Swindon would have used rather than spinning. Each to their own, of course, but it's always good to have another skill under one's belt.... Malcolm I don’t go back that far I’m afraid, but I agree that Swindon seem to have used this method rather than spinning. Actually, because of the boiler curvature and the taper, the spinning in the Amsbury method is not the end of the story, and there is still some beating to do before it is finished. So I’m always interested to hear of other ways of doing it. Gilding metal by the way, is not ideal for this particular item IMHO. It is soft and pleasant to work, but it has a distinctly reddish, coppery colour, not at all what is needed, especially when most of us have to be content with bronze rather than copper for our GW chimney caps- the bonnet might look more coppery than the chimney, and that would never do! Hence I’m using 70:30 brass, AKA ‘cartridge brass’ or CZ106, which is almost as ductile and a better colour. Gary
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Post by Cro on Mar 26, 2021 18:05:20 GMT
Gary,
I’ll pop a photo on my fittings page later as to not take up space here but the aim is to get the thin scale look where possible but I do get what you mean about the used and beaten look is very authentic.
Looking forward to seeing what you produce!
Adam
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Post by Gary L on Mar 27, 2021 1:45:37 GMT
It's back to the Tank Filler Manholes today. I have a collection of little bits and pieces for them, so now to turn to the main bodies. I abandoned thoughts of turning these from solid or from tube as soon as I realised that the original formers I had ordered from Ed were half the size they should have been, because I had got my diameters and radii mixed up at the drawing stage! They are in fact the size of a napkin ring, so I'm going to make them from flat, the way the factory would have done it (-ish). I used 16g brass, cut from sheet and machined into strip on the mill as described earlier. For ease of eventually soldering them into position, I then end-milled a ⅛" rebate along one edge thus: The strip looks endlessly long in the photo, but in fact there were two strips, milled separately, and each was only around 6" long. (They need to be a little bit over-long to assist the bending) After the milling, they were annealed, ready for the next step, which was bending them around a former: The former was made from two ovals, laser-cut from 5mm steel, through-drilled and bolted together using nuts and washers to bring the completed former to about 10 thou wider than the width of the machined strip. (An oval is quite a difficult shape to machine, but dead easy to draw in CAD!) As noted below, an extra oval to fill the gap would have been an improvement. Bending was easy, taking it quadrant by quadrant as shown. Annealed brass doesn't have much springback. Keeping everything tight to the former makes sure the flats of the oval are in the right place, then when removed from the former, the curves can be tightened the small amount necessary by finger pressure. Then with care the two ends are trimmed exactly square with hand tools, so the seam comes midway in one of the flats. Then the seam was closed with a bit of wire (just ordinary galvanised). Note how the twist in the wire lifts it away from the joint, so there is little danger of silver soldering it to the brass! The dabs of Tippex are just to make doubly sure. As an aside, Roger's use of titanium as a solder-proof medium made me realise why Tippex does the same job. What is the white pigment? Why, Titanium Dioxide of course! The penny clanks into place... I avoid using wire as much as possible for this purpose. If it had soldered itself to the brass it wouldn't have been difficult to file it away, but it is rather easy to accidentally overheat wire bindings so they suddenly glow red and fall off. Which is why I set them up on the hearth like this: ...so the wire is protected from the flame, which is directed to the inside of the joint. Then when the solder has flashed, the outside looks like this: ...and after the usual clean-up the two 'napkin rings' look this, with the former behind. With all bending there is a tendency for the outside of the bend to be slightly concave, and that happened here as well; though not by very much. Since the final soldered shapes were within a thou or two of the shape of the former, it was possible to remove some of the concavity by squeezing the former through the rings once or twice. Perhaps if I had filled that gap in the former with an extra layer it wouldn't have happened, but it is hard to know. The next step, tomorrow, is to solder on the various brackets, which is going to be a bit tricky, because they are small and light, and full of odd angles.
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Post by mbrown on Mar 27, 2021 18:22:53 GMT
If I can find the relevant EIM edition over the weekend, I will put the reference on this thread. I certainly think raising is the method Swindon would have used rather than spinning. The article by Geoff Nicholson was in EIM for October 1986. Malcolm
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