Gary L
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Post by Gary L on Mar 27, 2021 23:28:54 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 Thanks Malcolm, I’ll look that up when we can get back in the club library again Gary
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dscott
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Post by dscott on Mar 28, 2021 1:07:52 GMT
And by way of modern Technology you can get an Enlargement. Then send it Round the World. Lovely progress Gary. David and Lily.
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Gary L
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Post by Gary L on Mar 28, 2021 1:15:57 GMT
Soldering on the little brackets to the Tank Filler Manholes went quite well, considering how light they are, and how awkwardly shaped. I could see no way of securing them in position, so it would have to be our old friend gravity, aided by some carefully placed packing. So first, the beaky brackets: The steel wedges are just for a bit of weight, to make sure the filler body sits squarely on one of the flats of the oval. The piece of copper tube is turned to half a diameter minus half the thickness of the bracket, and holds the bracket nice and square, with the lowest corner aligned to the rebate ridge of the manhole body. As well as the visible piece of solder, there is a corresponding snippet in the same position on the other web of the beaky bracket that can't be seen. The flame is applied to the job from inside the manhole body, taking care to point it at the join location and nowhere else. This is because the bracket is itself silver soldered together with the same grade, as is the seam in the body. This is not as risky as it sounds, so long as the torch is removed immediately both solder snippets have melted. After that the front bracket is positioned: The bracket slopes downwards, so it is propped in position upside down, and since this makes the join vertical, the solder snippets are bent into U-shapes that can be seen hooked over the apex(?) of the joint. Lateral alignment was by eye; if I wasn't confident of getting it near enough right, I would have had to make a complicated jig; YMMV. Again, the same solder, and the same indirect heating from the inside of the oval body of the filler. Repeat for the second filler of course. And after a clean-up we get these: The reason why it is possible to do all this with the same grade of solder is twofold. (1) by some useful metallurgical happenstance, it takes more heat to melt the solder out of a joint than to melt it in in the first place and (2) The metal sections are all quite thin, so although brass is a good conductor of heat, it is also radiating it away like mad, so as long as the torch is kept pointing at the joint being made and nowhere else, the other joints stay cool enough to not be a problem. If the metal was heavier, and the joints closer together, 'step' soldering would be better, where you do the first joints with high-melting point solder and work your way down. The downside is that higher melting point silver solders (or at least the ones I have!) are appreciably less keen to flow, so not great for fine work.
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Gary L
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Post by Gary L on Mar 30, 2021 0:26:01 GMT
Still doing the Tank Filler Manholes. These are complex beasties; today its the lid, which have a flat top and a narrow rim at 90 degrees. Having re-ordered them from Ed at MEL, due to my getting the radii and diameters in a muddle in my CAD program, I found I had still miscalculated, and the lid former was a little too big. So the first job was to take 3/64" off all round in the mill. The oval shape is a bit of a pig; I did dit it by zeroing on the laser-cut edge before every pass with an endmill, taking off a chord of 3/64" max depth, and working around till I had made a rough decagon of it. Then it was a matter of hand filing the corners to make it oval again. Then, with the profile right, the hard edge on one face needs to have a tiny radius filed to remove the sharp edge. The rest of the job was pretty ordinary: The former is out of sight in the photo above, under the annealed brass blank; The plate on top is one of the (smaller) formers from the body, with a bit of card underneath it to prevent bruising. The whole lot is held together with a 10BA screw (because there will be a 10BA thread on the special pin that will eventually hold the lids in place). It is a weak thread, but it doesn't have to do much. The top plate is to prevent too much deformation of the flat part of the lid from the biffing that the protruding edge is going to get. The photo shows the small amount of deflection after a round or two with the planishing hammer, and ready for the second annealing. For anybody who hasn't done this sort of thing before, the art lies in lots consistent gentle tapping, not a few big whacks. I find it helpful to give a sort of sliding blow with the hammer in the direction you want to bend, which seems to give less bruising. In the next photo, we are about half way there, and set up for the fourth or fifth annealing. It is best to hurry slowly, and anneal often: Like with spinning you don't want to have more metal to form than is absolutely necessary, and if it starts to ripple, smooth the ripple out before going any further. (An expert will make lots of ripples deliberately, which I think is called 'raising' but the method shown here works for me.) All that is required is a ⅛" rim, but here I'm beating down about ¼", which makes significantly more work. On the other hand, you don't want to end up with too little; 'too much' and it can be easily trimmed off. After quite a few more rounds of annealing and tapping, the brass is sitting snug to the former, and it is time to remove the excess metal on the rim. In the photo below, the assemblage is upside down on the rotary table, gripped in the jaws by the top plate, with parallels under it to make sure both lids get trimmed to the same measurement. With the oval profile of the lid, combined with the oval profile of the top plate, there is little hope of centralising anything, so the X-axis of the mill has to be constantly adjusted to keep the slitting saw engaged at roughly the right depth of cut. Light cuts are necessary because there is only a 10BA screw holding it all together... It is scarcely possible to cut to the right depth all the way round, but any residual bits can be cut through carefully with a junior hacksaw to release the lid, and a few strokes on some emery paper on the surface plate gets rid of any flash on the bottom edge. So after a light filing round the edge and some more emery to get rid of the oxide etc, we end up with this: Now it is just necessary to make some pins tomorrow, and now that measurements can be taken accurately from the job, drill the last few holes in the links...
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Post by ianholder on Mar 31, 2021 18:41:53 GMT
More years ago than care to remember I spun the safety Valve bonnet for a 1400 class ( not a Dart, a proper one )and started with a piece of brass tube. It needs to be the size of the bottom of the cone part of the bonnet. First operation is to turn a tapered former that fits inside your tube, the length of the taper the same as the taper on the bonnet and a parallel section the size of the small end, then with the tube and former held in the three-jaw you spin the tube down onto the former. The next stage requires a split rectangular block with the shape of the bonnet hollowed out inside it. The two halves of the block are bolted together, held true in the four jaw and a tapered plug with a drawbar used to pull your tube hard into the former. You can then spin the base out to size. I must admit that after all this time I cannot remember exactly how I held the block for the next operation, but I think it was held back on a faceplate with the base of the bonnet clamped between the block and the faceplate and the tapered plug wedged in to support the inside of the bonnet while the top was spun over. Reading the above it all sounds easy, but it took a long time, lots of dismantling set ups to re-anneal and then setting up again, but it worked for me. That is it did after I managed to get rid of the beautiful wood grain that I had spun into the brass! Hope this is clear and it helps but of course you have to make it fit the tapered boiler!, regards Ian
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Gary L
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Post by Gary L on Mar 31, 2021 23:03:04 GMT
More years ago than care to remember I spun the safety Valve bonnet for a 1400 class ( not a Dart, a proper one )and started with a piece of brass tube. It needs to be the size of the bottom of the cone part of the bonnet. First operation is to turn a tapered former that fits inside your tube, the length of the taper the same as the taper on the bonnet and a parallel section the size of the small end, then with the tube and former held in the three-jaw you spin the tube down onto the former. The next stage requires a split rectangular block with the shape of the bonnet hollowed out inside it. The two halves of the block are bolted together, held true in the four jaw and a tapered plug with a drawbar used to pull your tube hard into the former. You can then spin the base out to size. I must admit that after all this time I cannot remember exactly how I held the block for the next operation, but I think it was held back on a faceplate with the base of the bonnet clamped between the block and the faceplate and the tapered plug wedged in to support the inside of the bonnet while the top was spun over. Reading the above it all sounds easy, but it took a long time, lots of dismantling set ups to re-anneal and then setting up again, but it worked for me. That is it did after I managed to get rid of the beautiful wood grain that I had spun into the brass! Hope this is clear and it helps but of course you have to make it fit the tapered boiler!, regards Ian Thanks for that explanation Ian. It goes to show that there is always another way to skin a cat, a very superior cat in this case! I’m committed now to the Amsbury method, having got the materials all ready for a second attempt, but your description will greatly help an adventurous builder who wants to avoid the joint that is unavoidable otherwise. So thanks for sharing it. Gary
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Gary L
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Post by Gary L on Apr 4, 2021 0:22:28 GMT
Not much to show for the last few days sporadic effort on the Tank Filler Manholes, but they are at least both finished: Top of the photo shows all the parts before assembly. The lid has a U-shaped bar silver soldered in place; its job is to maintain alignment of the lid. The pivot bolts that hold it all together are all specials; stainless rod with the ends threaded 10BA and brass nuts silver-soldered on one end. The small parts are metal-blacked; the lid and body will be painted eventually, with the tanks. The metal black solution has also blackened the stainless to my surprise, though I suspect it will rub off quite quickly. (It doesn't matter, because only the heads and nuts will be visible). The strongbacks are mild steel, blacked by heating to red heat and quenching in oil. I shall have to remember to keep them oily. The gasket (far left) is cut from a sheet of Butyl Pond Liner. It is retained by the nut and washer that secures the central lid pin, and doesn't seem to need anything else to keep it in place. Unfortunately, due to the simplification of the inboard profile of the tanks, whereby the hidden skin is a segment of a cylinder, not tapered like the prototype to match the boiler, this means that there is quite a lot of empty air between tanks and boiler at the front end where these Fillers are mounted. This will call for a certain amount of cheating, because in the scale position, more than half of the filller aperture will be 'blind' since the tank frame falls more or less under their centrelines. This is not apparent on the Adams drawing, but if I had followed that exactly, my boiler would not fit between the two tanks Another cheat will be needed for the vent pipes, which can only be positioned about ¼" further outboard than they should be. It is not the end of the world; I would rather have them working, and in a slightly wrong position, than have them correctly sited but dummies. This will be a working locomotive after all, not a glass-case model.
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Post by Roger on Apr 4, 2021 8:32:00 GMT
Not much to show for the last few days sporadic effort on the Tank Filler Manholes, but they are at least both finished: Top of the photo shows all the parts before assembly. The lid has a U-shaped bar silver soldered in place; its job is to maintain alignment of the lid. The pivot bolts that hold it all together are all specials; stainless rod with the ends threaded 10BA and brass hex heads silver-soldered on one end. The small parts are metal-blacked; the lid and body will be painted eventually, with the tanks. The metal black solution has also blackened the stainless to my surprise, though I suspect it will rub off quite quickly. (It doesn't matter, because only the heads and nuts will be visible). The strongbacks are mild steel, blacked by heating to red heat and quenching in oil. I shall have to remember to keep them oily. The gasket (far left) is cut from a sheet of Butyl Pond Liner. It is retained by the nut and washer that secures the central lid pin, and doesn't seem to need anything else to keep it in place. Unfortunately, due to the simplification of the inboard profile of the tanks, whereby the hidden skin is a segment of a cylinder, not tapered like the prototype to match the boiler, this means that there is quite a lot of empty air between tanks and boiler at the front end where these Fillers are mounted. This will call for a certain amount of cheating, because in the scale position, more than half of the filer aperture will be 'blind' since the tank frame falls more or less under their centrelines. This is not apparent on the Adams drawing, but if I had followed that exactly, my boiler would not have been able to fit between the two tanks Another cheat will be needed for the vent pipes, which can only be positioned about ¼" further outboard than they should be. It is not the end of the world; I would rather have them working, and in a slightly wrong position, than have them correctly sited but dummies. This will be a working locomotive after all, not a glass-case model. Hi Gary, Those look superb. Even following the tank outline, you still end up with the filler opening looking down onto the inner sheet. As long as you can get water in, that's all that matters. Nobody is going to notice small positional errors of features on the tanks, it's going to look great. The eye is drawn to the detail itself, not precisely where it is.
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JonL
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Post by JonL on Apr 4, 2021 14:19:24 GMT
Excellent work Gary. Hats off.
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Gary L
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Post by Gary L on Apr 7, 2021 0:44:17 GMT
Thanks Nobby and Roger The bits and pieces that decorate the tanks are almost done now, except the cross-stays, which I think I will leave till the tanks have been skinned and mounted, in case they need any small adjustments to fit snugly around the boiler without actually touching. I'm glad I did it this way round, as having visualised the positions, there is some machining to do on the framework components, which is much easier done before they are finally assembled. First, there are through-holes to bore for the tank vents, which as noted already need to be about ¼" outboard of the 'true' position, or they will break into the tank side. They are big holes, so they need to pass through the centre of the frame inner top stringer to avoid weakening them more than necessary. Then some slots where the filler manholes will fit, to avoid blanking off the aperture too much. As Roger says, they are quite big, so we don't need all the available area for water filling purposes. Even so I've a suspicion that these also might benefit from moving outwards a little, but that decision doesn't need to be made yet... I have the option of cutting the webs to create a bigger opening at the expense of weakening the frame. I suspect this wouldn't matter, because if the frame wasn't there at all, the tanks would still form a very strong box with a stressed skin, but these inner frame stringers have the subsidiary function of making the joint for the 'inspection panels' which make up the inner tank sides, so I don't want to do anything silly. Not visible in the picture is the LHS lower stringer which needed to be swelled out by silver-soldering on some extra material in way of the Injector water valve, otherwise the hole would have been half-in, half-out of the stringer making it very difficult to thread for the valve. ( Note to self: that's another hole I must remember to bore while I'm at it!) Moving on to the front panels of the tanks; there is a 5mm structural bulkhead that takes lots of small countersunk screws in its edges to secure the skins. There is also quite a lot of detail that needs to go on this face as well, without making lots of leak points; a handrail and three steps. The David Adams solution is to mount these on a 16g fascia plate or false front, which in turn is screwed to the main bulkhead with a mutltiplicity of CSK screws. So the first job was to clamp both plates accurately together and spot through the various mounting holes. These will be used as guides for recesses in the 5mm plate to clear the spigot fastenings of the detail. Then, without moving the clamps, drill and countersink tapping holes for the 8BA screws that will secure the false front: I managed to snap off no less than three of these carbide drills in the course of these operations, for reasons that are not clear, as I know only too well how delicate they are. They seemed to take a dislike to the thick brass plate and jammed on the swarf. I can live with the breakages, but getting out the tips is going to be a struggle. One had shattered almost to powder and just needed some encouragement with a scriber point, but two are more firmly stuck. I can't use the Alum standby, because carbide contains no iron, so I will need to think up another way.
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Post by Roger on Apr 7, 2021 7:55:47 GMT
That's the only downside with Carbide PCB drills, they are brittle. It doesn't look like you had the plate clamped for that operation. Maybe you did, but I'd definitely always clamp it so it can't grab. I'd also always use a handwheel to feed it, never a lever type handle. It's just too difficult to move it smoothly and slowly enough with a lever.
I avoid using PCB drills for anything deep because if you break them off in the job, it's probably going to be very difficult to remove them. That's another reason to feed the drills very slowly indeed. The slower you go, the more likely you are to be able to get any broken bit out.
So for a 1mm hole that's more than 1mm deep, I spot it and get it started with a PCB drill, then switch to a HSS one.
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Gary L
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Post by Gary L on Apr 7, 2021 17:51:21 GMT
That's the only downside with Carbide PCB drills, they are brittle. It doesn't look like you had the plate clamped for that operation. Maybe you did, but I'd definitely always clamp it so it can't grab. I'd also always use a handwheel to feed it, never a lever type handle. It's just too difficult to move it smoothly and slowly enough with a lever. I avoid using PCB drills for anything deep because if you break them off in the job, it's probably going to be very difficult to remove them. That's another reason to feed the drills very slowly indeed. The slower you go, the more likely you are to be able to get any broken bit out. So for a 1mm hole that's more than 1mm deep, I spot it and get it started with a PCB drill, then switch to a HSS one. Thanks Roger, that is a useful rule. Drilling down ¼” depth was probably pushing it too far. The plate is indeed clamped, but the vice is gripping on the 5mm plate which is concealed by the false front clamped on top of it. This is another possible cause of the grabbing, though maybe not in the way you mean. The plates are clamped firmly at the edges, but there is a tiny amount of possible movement up and down in the centre, and this tends to happen when drilling through two sheets, if a burr can grow at the interface between the two. The movement is slight, but typically just off the vertical, which might be enough for a momentary check on the drill. With a heavy motor whirling it at 1500 revs, a slight check is all it would need. I don’t think I can agree about the wheel versus lever control though. Besides, even if I did, my mill/drill only has levers! The three levers are removable from the hub, and I usually only have one mounted, which can be quickly shifted as necessary if it fouls the job, which happens quite often. If I need a lighter touch, I grip it at the hub. Gary
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Post by andyhigham on Apr 7, 2021 20:35:04 GMT
I've found that since I fitted power feed to my mill X axis I don't break small slot drills when cutting keyways
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Gary L
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Post by Gary L on Apr 8, 2021 10:48:54 GMT
I've found that since I fitted power feed to my mill X axis I don't break small slot drills when cutting keyways Luxury! I do find winding away on the X-feed handle for long cuts is surely the most mind-numbingly boring part of model engineering. Haven’t broken any slot drills though, never, so I can’t use that to justify the purchase. Usually I can’t even hear the radio for a bit of light relief... Gary
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stevep
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Post by stevep on Apr 8, 2021 14:37:44 GMT
Sorry for hijacking your thread Gary, but this reminds me that the other day, I had my bandsaw going (which has an automatic cut-off), the mill was working away under power feed, while I was working away on the lathe. Couldn't hear Classic FM!
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Post by andyhigham on Apr 8, 2021 14:49:10 GMT
Sorry for hijacking your thread Gary, but this reminds me that the other day, I had my bandsaw going (which has an automatic cut-off), the mill was working away under power feed, while I was working away on the lathe. Couldn't hear Classic FM! Tune into Planet Rock and turn it up to 11
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Gary L
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Post by Gary L on Apr 8, 2021 22:31:28 GMT
Sorry for hijacking your thread Gary, but this reminds me that the other day, I had my bandsaw going (which has an automatic cut-off), the mill was working away under power feed, while I was working away on the lathe. Couldn't hear Classic FM! Tune into Planet Rock and turn it up to 11 Says the man who has no neighbours-? Gary
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Gary L
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Post by Gary L on Apr 8, 2021 22:35:33 GMT
Sorry for hijacking your thread Gary, but this reminds me that the other day, I had my bandsaw going (which has an automatic cut-off), the mill was working away under power feed, while I was working away on the lathe. Couldn't hear Classic FM! You are not hijacking anything Steve, always glad to hear from you. (Not sure I would want to try and hear you in your workshop though!) Gary
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stevep
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Post by stevep on Apr 10, 2021 17:53:55 GMT
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Gary L
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Post by Gary L on Apr 11, 2021 11:53:01 GMT
Thanks Steve, that's a brilliant video- it shows everything I was trying to say. In fact he could very well be spinning a GWR bonnet, at least in the smaller scales! He uses a very small lathe for spinning, but it illustrates how the kind of lathe many of us have is easily adapted to the purpose. It is only the tool post that would cause much difficulty, and even there, the traditional spinner's toolpost with multiple peg holes is not really essential. As long as you can improvise a single vertical post, (ideally extending below the lathe centre), you can adjust its position by moving the cross-slide and saddle, which proper spinning lathes don't have. Note his method of proceeding. He doesn't flatten the rim until the job is almost finished. Instead he leaves a rim protruding at about 90 degrees all the time, but uses the spinning tool to flow it to the left as the work progresses. This seems to help with stability, but it also allows you to work a tight grip at the right-hand side between the 'chuck' and the workpiece, from the very beginning. This is very important because if you don't do this from the start, it is hard to replace the workpiece exactly concentric after every annealing. And that leads to a minor mystery. If the video is to be believed, he didn't anneal the work once. I looked hard for evidence of a jump cut at intervals but I couldn't find one. I think it must be very skilful editing, because I can't imagine you could work copper that much without at least half-a-dozen annealings. I certainly wouldn't recommend a beginner to try it that way. It is (or should be) easy to release the job from the 'chuck' at intervals, so there is no good reason not to... if in doubt, anneal it! I am writing 'chuck' in quotes, because what spinners call a chuck is what we would probably call a mandrel or a former. In the video, you can see two chucks: the normal one that holds the former and the one that the work is formed around. Very confusing! Incidentally, the 'chuck'should be made to exactly the size and profile of the inside of the finished job. There is no 'springback' to allow for, and when the job is finished the spun shape will grip the 'chuck' very tightly. I've said elsewhere that spinning is essentially about stretching. The experts can compress the metal as well, and even a non-expert can thicken the metal a bit by moving the tool left-to-right instead of the normal right-to-left, but it takes practice. For the unskilful (like me), compressing can easily lead to rippling which is very hard to correct. You might as well start again! You can see how much stretching has occurred as the rim is moved to the left. Compare the radius of the blank disc he starts with, with the height of the finished product. All this stretching means that the metal gets thinner as you progress, so the rim of the vessel could easily be only half as thick as the blank he started with. A real risk is that the metal gets too thin and breaks apart. (He uses a tool to thicken up the rim a little at the end of the video- this is advanced work!) For that reason it is a mistake to start with a blank that is too thin, or of too large a diameter. A diameter that is too great makes the metal hard to work, though you can of course trim it, with care, as you proceed. I find a sharp parting tool with a short but very narrow blade (1/32" or less) works best for me. You will need one of these for the final trim to size anyway. In the video, the spinner judged his diameter perfectly and didn't need to do this, but that is exceedingly difficult to achieve and you run the risk of ending up short. -Gary PS. I realize all this knowledgeable-sounding advice leaves me nowhere to go if I don't get a perfect result when I get round to my second attempt at Paddington's bonnet! I've got plenty to do on the tanks at the moment, so my second attempt is well down the road, and maybe you'll all have forgotten by then!
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