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Post by delaplume on Dec 5, 2019 11:43:15 GMT
Fear not, young Striplar ...The night is darkest just before dawn !!
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Post by andyhigham on Dec 5, 2019 11:47:54 GMT
Tabs not strong enough?
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Post by Doug on Dec 5, 2019 12:35:55 GMT
Oh no that’s really bad, thanks for posting the wobbly videos though they have confirmed my concerns that I have been trying to run too fast on my CNC (things seem to go so much better when I am not rushing the cuts) She is looking superb though keep up the excellent work 😊
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Post by simplyloco on Dec 5, 2019 13:13:27 GMT
Why haven't we got a 'commiserations' tab?
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Post by Roger on Dec 5, 2019 14:59:59 GMT
I don't like to waste opportunity of a cockup, so here's an improvement to the clamping system. This wasn't at fault, it was plain stupidity not to clamp the inside when cleaning up and removing the tabs! I made a fine job of securing the scrap frame though... Anyway, these are the blocks that were used under the plate. The Tee slots aren't accessible when you're trying to grip work that's large in the 'Y' axis, so these clamp to the bed using the Tee slot and an M8 cap screw. Then you can swing them round to any angle and use the M8 hole as a further attachment point. The problem with this arrangement is that you're not clamping directly onto the parallels, so you can't do them very tight unless you put packing under the bolt. So my improvement to that is to grind them all so they're the same thickness... 20191205_121135 by Timothy Froud, on Flickr .. and then grind some spacers so that they make up exactly 35mm thickness which is the same as one pair of parallels. I use a second two pairs that make up 35mm when put on top of each other. Now I can tighten onto this arrangement knowing it will be flat. I can take bigger cuts then. 20191205_145050 by Timothy Froud, on Flickr
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Post by Roger on Dec 5, 2019 15:03:59 GMT
Oh no that’s really bad, thanks for posting the wobbly videos though they have confirmed my concerns that I have been trying to run too fast on my CNC (things seem to go so much better when I am not rushing the cuts) She is looking superb though keep up the excellent work 😊 Thanks Doug. One of my reasons for running slowly is that the spindle speed is limited on the big spindle, but it also generates a lot less heat and chatter if you just find that sweet spot where it seems to be making light work of it. I have to run the high speed spindle quite a lot faster and it's much less rigid. For small cutters, say 2mm or less, that's fine and I can run quite a bit faster. That does produce a lot more noise and chatter though.
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dscott
Elder Statesman
Posts: 2,437
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Post by dscott on Dec 6, 2019 1:06:57 GMT
I had 3 weeks work in Plymouth in September so managed to coordinate a purchase of an Abwood machine vice £70 on Gumtree. 6 inch of epic proportions and grip and of course weight. Nice when you can achieve a balance. Oh yes I discovered I needed a foot of lead sheet for one of the windows! And at least the rest came in handy to balance the car on the way back home. Yes the property is 4 1/2 miles from the Plymouth track! Before you ask.
I am getting quite practiced at filling in bits of frames to make them into more scale locomotives with the mig! Yes including my Speedy! She has just got a set of Horns and Gunmetal axle boxes with keeps donated from the Big Prairie project. Hardly seen but super scale. I know that they are there.
David and Lily.
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Post by Roger on Dec 7, 2019 19:49:49 GMT
So, straigth back into making the footplate again... I bought some 1/4" x 6" cold rolled plate which might well have bent like a banana if I machined off one side. So this is a little cave furnace to get the plate Red hot... 20191206_100733 by Timothy Froud, on Flickr 20191206_100817 by Timothy Froud, on Flickr ... after which the spacers were slid out and the top dropped down to keep the heat in. 20191206_100934 by Timothy Froud, on Flickr That was still too hot to hold after 4 hours, but cool enough to have stabilised. I'm using the fine pole magnetic chuck to hold it down. It sit's pretty flat with no noticeable rock this way up, and only very slightly the other way. 20191206_145536 by Timothy Froud, on Flickr The fly cutter tidied up the mill scale in one 0.2mm deep pass. 20191206_150607 by Timothy Froud, on Flickr 20191206_155153 by Timothy Froud, on Flickr I've sketched round the 3D printed part and drilled the holes for the modified clamping arrangement. 20191206_162026 by Timothy Froud, on Flickr The plate was flipped over because the fly cut surface is the bottom of the cab. Here I'm using the drill program for the reverser bolts to get the program aligned. I just jogged to where I was happy with it, and then overtyped the DRO with the relevant coordinated for this hole. Of course I then did a sanity check to see if it was plausible and checked the limits of the profile program to make sure I could reach all round it. 20191206_164357 by Timothy Froud, on Flickr This is a much more satisfactory clamping arrangement than last time because I can tighten up the cap screws properly. Here's a wobbly video of the 16mm ripper in action. Bizarre as it may seem, I think having all that swarf there smothered in cutting oil actually helps to lubricate the cut. 20191207_103535 by Timothy Froud, on Flickr I've marked a spot with a felt tip peb where I'm going to set the zero for each cut. We've roughed out the bulk of the unwanted material already, so this is an 8mm cutter bringing it down to the right finished depth and starting to square up the corners... 20191207_103943 by Timothy Froud, on Flickr ... which are pre-finished with a 2mm cutter, and finally a 1mm cutter just on the corner. The 2mm cutter was run all the way round. 20191207_115805 by Timothy Froud, on Flickr 20191207_121946 by Timothy Froud, on Flickr The clearance slots for the reverser and diverter valve were then machined with a 2mm followed by a 1mm cutter to get a tight corner. Here I've also finished the outside of the angle and thinned edge where it drops from 1.5mm thick to 0.5mm where the cab sides meet. 20191207_181147 by Timothy Froud, on Flickr 20191207_181200 by Timothy Froud, on Flickr So far, so good, I'm just machining the profile, this time in two halves so I can clamp the middle from the opposite side. I shouldn't need this, it wasn't a problem last time and I've still got nibs holding it, but better safe than sorry! With a bit of luck, I should get both of the profile cuts finished tonight and then it will be finished.
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Post by simplyloco on Dec 7, 2019 20:12:53 GMT
SNIP So this is a little cave furnace to get the plate Red hot... 20191206_100733 by Timothy Froud, on Flickr Roger, do you mean to tell us that you don't have one of these for your small annealing/heating jobs? Shame on you... 20191207_200412 by inkaboat, on Flickr
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Post by Roger on Dec 7, 2019 20:30:48 GMT
SNIP So this is a little cave furnace to get the plate Red hot... 20191206_100733 by Timothy Froud, on Flickr Roger, do you mean to tell us that you don't have one of these for your small annealing/heating jobs? Shame on you... 20191207_200412 by inkaboat, on Flickr Hi John, One day I'll have to get one, although I have no idea where on earth I'd put it!
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Post by simplyloco on Dec 7, 2019 21:34:00 GMT
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dscott
Elder Statesman
Posts: 2,437
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Post by dscott on Dec 8, 2019 0:14:42 GMT
I now almost have a super workshop with many lathes and 2 mills!!!!! But my first and most successful, and completed, and run for many hours Locomotive. Was built in snatches of time at work, A tiny space in a one bedroom flat in Enfield, on a cabinet that I found in a skip. And a vice that kept coming undone. Soldering was done on the gas cooker and painting out in the shared garden. This needed clearing first to get into it.
Ever after that with super facilities at work and home progress has been slow. The bigger the house and garden and car. The more work you have to put into them!
David and Lily. back on guttering in the morning!!!
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JonL
Elder Statesman
WWSME (Wiltshire)
Posts: 2,902
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Post by JonL on Dec 8, 2019 8:35:43 GMT
So is that the process of normalising? Is that because there are tensions in the surface? I'm still a bit novice with metallurgy
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Post by Roger on Dec 8, 2019 9:05:55 GMT
So is that the process of normalising? Is that because there are tensions in the surface? I'm still a bit novice with metallurgy Yes, that's how I understand it, Metallurgy was my worst subject at Poly. The idea is to raise the whole structure above the recrystalisation point and then to allow the crystals to re-form as large ones with the minimum of stress in the component. Quick cooling of Steel traps the needle like structures that form from the Carbon within it. The more Carbon, the more needles and the more hard and brittle the Steel. You don't need much Carbon for this to happen, 0.2%-1.2% takes you through the extremes, with the highest end being Silver Steel or Gauge Plate. You don't want any of these needles, so slow cooling allows them to disperse. Quenching catches them in their needle like state before they've had a chance to disperse. Usuallly this would leave a High Carbon Steel way too brittle to be of any use, hence the need to Temper the piece, effectively 'dissolving' some of the needles by re-heating to very specific temperatures. I'm sure there are metallurgists here why are wincing over my crude description, but it's good enough to grasp what's happening from a practical point of view. As for why the stresses are there, that's easier to appreciate. If you've ever dug a hole and then tried to put the earth back in, you'll know that you can't just pile it all in and end up with it level, even if you pound away at the top layer. The problem is that the force you apply at the surface doesn't get transmitted all of the way through to the bottom layer of earth. To get it all in, you would have to pound very thin layers so it was all the same density top to bottom. So it is when you Cold Roll Steel. The outside surfaces get deformed, but the deeper you go, the less compressed the material is. The result is that you end up with a denser more stressed outer skin. Removing one of those outer compressed layers can result in the job bending, you just can't be certain one way or the other.
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Post by David on Dec 8, 2019 10:11:13 GMT
Sorry to see the result of the first attempt, but it looks like you're well on the way with the second.
Why did you buy cold rolled steel rather than the other?
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Post by Roger on Dec 8, 2019 10:20:21 GMT
Sorry to see the result of the first attempt, but it looks like you're well on the way with the second. Why did you buy cold rolled steel rather than the other? It was what was available in 1/4" thickness, that's all. I'd still have normalised it anyway since it's such a thin section that I end up with. There are stresses in Hot Rolled plate too, although nowhere near the level they are in Cold Rolled plate.
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JonL
Elder Statesman
WWSME (Wiltshire)
Posts: 2,902
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Post by JonL on Dec 8, 2019 14:13:29 GMT
The hole analogy is excellent, thanks. Sorry to divert from the model engineering!
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don9f
Statesman
Les Warnett 9F, Martin Evans “Jinty”, a part built “Austin 7” and now a part built Springbok B1.
Posts: 960
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Post by don9f on Dec 8, 2019 16:36:53 GMT
In my opinion, this subject can be very relevant to model engineering....for instance you can mark out something like a connecting rod, create the holes in each end, machine the profile and finish up with a rod that is longer between the hole centres than it was to start with. Been there and done that!
Cheers Don
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Post by Roger on Dec 8, 2019 17:14:36 GMT
Agreed about Metallurgy, it's something we need to have at least some grasp of if we aren't to get caught out. So this is almost done, just a few more holes and trimming up the front and rear edges. 20191208_112331 by Timothy Froud, on Flickr I made a slight cockup on the 'U' shaped clearance by splitting the program path in half and forgetting that the tool centre will end up level with the end of the line. That's what's added those two semi-circles at the lower left side of the cutout. Had I split the path on an outside corner that wouldn't have happened. Another thing to watch out for! This time I've added four M1.6 clearance holes, two for each plinth so I can bolt them from underneath. Originally I didn't have a base for them, but now there is I may as well tap some holes in that to hold them down. 20191208_170126 by Timothy Froud, on Flickr As it happens, the gouges are of no consequence since it will all be hidden under the chequer plate. There will be more cutouts in the front edge to clear pipes, so I'll wait until all of that is finished before deciding whether to neaten that up a bit. All of the pieces are machined size for size without any clearance, so I'll need to work my way around all of these now and get it all to fit snugly together. The chequer plate along the front will be the last detail to finish when all of the pipework is completed. There's another raised part on the right beyond the reverser where the vacuum reservoir sits. I probably won't be doing anything with that until I've got more of the cab done and the reverser installed with the reach rod in place so I can be sure about what I'm going to do with the vacuum reservoir. The reach rod on 1501 is much lower down so there will need to be a clearance for that. 20191208_170035 by Timothy Froud, on Flickr
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Post by silverfox on Dec 8, 2019 17:18:01 GMT
Roger
My illusions are shattered
you are human!!!
apart from that ricket, excellent work ,stuff i can only dream of, and then only after parktaking of some substances i cannot name ( only joking about the substances)
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