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Post by 92220 on May 23, 2020 7:57:17 GMT
Hi Don.
Crafty way of doing it!! Looks good though. Yes you will need a rolling road to run the loco on air. If you just jack it up with the wheels hanging down, the coupling rods will bind in their bearings, at front and rear dead centres, around the crank pins. When I first tried mine, I couldn't work out why there was a tight spot when rotating the wheels. I assumed it was the coupling rod bearings being tight and somehow I had maybe made errors in measuring the axle centres, and opened them up until the wheels would rotate. You can't just push it along unless it's on rails because of the centre wheels not having flanges. When I realised what was going on I also realised that I had to remake all the bearings that I had opened out, as they had been made right in the first place!!
Bob.
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Post by 92220 on May 21, 2020 18:39:02 GMT
Hi Roger.
That's an idea! I'll look at making a couple of different size silver steel jets, just to see how long they last. With glass beads I am guessing a lot longer than aluminium oxide grit.
Bob.
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Post by 92220 on May 21, 2020 9:27:03 GMT
Hi Roger.
I'll have to have a look at how I can do that on mine. When you think about the Badger grit blast gun, there must be ways of reducing air and pressure requirements on our units. The Badger gun is just their cheapest bottle feed airbrush, with a tiny ceramic nozzle fitted instead of the paint spray head. I'm sure that if the nozzle of our standard blast guns were reduced to around 1/8" (3mm) the air requirements would be much reduced, and the blast cone would also be more concentrated for working on smaller items. The biggest problem would be trying to find a smaller blast nozzle commercially.
Bob.
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Post by 92220 on May 21, 2020 8:38:54 GMT
Hi Roger.
No problem. Your modification may help you use less air, but you may need to reduce the size of your blast gun nozzle. For mine to work as it should, I have had to up the compressor output to around 10CFM and work with a pressure of 80 to 90psi. At that it works fine. A lower CFM and the compressor is struggling to keep the grit flowing. A lower pressure and beads struggle to clean the surface. Grit can work at a slightly lower pressure because it is a much harsher abrasion.
Bob.
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Post by 92220 on May 20, 2020 17:32:22 GMT
Hi Roger. Here are those photos of the grit pick-up in my grit blast cabinet, as promised. Sorry it's taken a time, but I had to 'un-bury' the cabinet and then clean out the beads to get the photos. Hope they help. EDIT:- There are 2 tubes making up the suction pick-up, but I don't see why there are 2. The one seems to be just a tube going from top to bottom. Bob.
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Post by 92220 on May 20, 2020 8:03:05 GMT
Hi Adam.
That looks like the beginnings of a very nice model!! I will email you a copy of my Livery Data Sheet for City of Truro. The NRM used it to do the lining out of City of Truro when Tony Filby was in charge. Somewhere I have a copy of the drawing register at Didcot, showing all their archived GWR drawings. I will see if I can find it and send you a copy of that too.
Bob.
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Post by 92220 on May 19, 2020 8:02:29 GMT
Very nice job Steve!!
Bob.
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Post by 92220 on May 17, 2020 13:16:53 GMT
Hi Eddie.
Yes it does, if you do it right. I made my frames back in 1971, and grit blasted them to remove the rust patches. Since then, over the years, I have added numerous mild steel parts to the loco, many of which had rust patches on/in the steel when I got it out of the company scrap skips, before I started the paint business, and these have also been grit blasted until I changed over to bead blasting some 10 years ago. It still works, but leaves a smoother surface to the metal, though deeper patches of rust need to be grit blasted, not bead blasted. If there were any patches of rust left on any of the mild steel parts of the loco, there is not a scrap or trace anywhere, and much of the loco is still unpainted. Yes, it is always in a permanently warm workshop, but rust, once present will continue to corrode steel more and more over time, even in a warm dry atmosphere. Rust does not start INSIDE steel. It starts on the surface and in contact with air, and corrodes inwards. The rust we come across in our model work, is only surface rust. It is not deep into the metal, or we wouldn't even consider using it, so grit/bead blasting will clean it all off if done properly.
As well as using a grit blaster for years, for my model engineering, I've also had plenty of experience in the process while working as a design draughtsman, for Delapena Honing Equipment, where we had to grit blast most parts that were not machined, for the small, and large honing machines we built. You refer to rust under rivet heads. If there is rust under any rivet heads, you will not get rid of it with blasting, but neither will you neutralise it chemically. The rivet should be tight enough that the underside of the head is sealed against the surfaces being riveted. If chemicals can get to the rust, the rivet isn't tight enough. Also, liquids should NEVER be used on a riveted assembly as they will creep in by capillary action and then creep out again, by capillary action, when next painted.
Bob.
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Post by 92220 on May 17, 2020 8:46:41 GMT
Hi Julian.
Bead blasting, or grit blasting, gets rid of every last spec of rust on steel, and as we model engineers use a lot of the stuff, it is always a problem, which this route gets over. It can also be used to remove old paint coatings on riveted assemblies without the problem of liquid stripper getting ito the joints and ruining future painting. It also gives a uniform finish on dis-similar metals for paint to adhere to. I'm sure you will have noticed that a thin coat of paint on a sheet of steel, looks different to a coating on a sheet of brass, due to a difference in surface finish. Not a lot of difference, but it is there. Bead/grit blasting gets over that problem. Hope that explains the reasoning.
Bob.
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Post by 92220 on May 16, 2020 7:57:07 GMT
Hi Bob, Sorry if I confused you. It’s wasn’t me running minimal media & 40 psi, it was Ray of Rays Garage on YouTube. The surging occurs as the vacuum in the media supply pipe fills & empty’s via the gun.....just thinking about it I should try a 3/8 tube instead of the 1/2 one. My blaster is the bench top model, yes it has sloping side BUT only the front & back, the pickup tube used to lie in the bottom & sucked the media from just around it. When we first got it & was blasting with it the media would always end up as far away from the pickup as possible! On my to do list is to get a new 4 way sloping base made, but it would probably be better & maybe cost the same to get a whole new cabinet! Cheers Kerrin Hi Kerrin. Sorry I was misunderstanding. Now I understand what you are describing. I had one of those bench blast cabinets. It used to work well when it was full of media, but I did find that I was always having to go into it and move the media to the suction pipe because there was no means of making it flow naturally. I could have cut the bottom out of the cabinet and made up a conical, or inverted pyramid shape bottom, but then it wouldn't have fitted on the bench I had it on, so I bought a floor standing unit that already came with the better shaped base to the cabinet. The bench blast cabinets are fine if you just want to work on small items for short lengths of time, but anything large is a bit beyond it's capability unless it is modified. Bob.
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Post by 92220 on May 15, 2020 9:29:45 GMT
Hi Roger.
I'll see what I can do about some photos. I will have to do a bit of clearing. It is in the garage part which currently is chock-a-block. This might be an excuse to get tidying up!!!!
Bob.
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Post by 92220 on May 15, 2020 8:45:15 GMT
Hi Kerrin.
I'm not sure why there should be any surging. My bead jet doesn't surge. It's a smooth, constant, blast of beads. I do note that you are using a very small amount of beads, and only 40 psi though. I don't know what cabinet design you have, but the base of my cabinet is formed into a large funnel so is always full of the beads, which are sucked up from near the bottom of the funnel. There is a large, heavy gauge, mesh over the top of the funnel, for parts to be supported on. I use between 90 and 100 psi, and around 8 to 9 CFM air, and the smallest gun nozzle.
Bob.
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Post by 92220 on May 15, 2020 8:30:49 GMT
The greatest problem with using one of these new super-strong adhesives to fit structural parts is that, as yet nobody knows for sure, if the adhesion will degrade over time. I have some of the adhesive they use for attaching supercar bodies to the chassis. It is quite expensive, as you would expect! Interestingly though it is a 2-part mix, you don't have to mix it manually like you do 2-part Araldite. It comes in a 2-part syringe and has a detachable convoluted nozzle, that mixes the 2 parts together, in the correct proportions, as it is dispensing it.
The nozzles vary in price dramatically, depending on where you buy them from. I have seen them advertised for £13.00 a dozen, and have bought them from somewhere else, for £3.00 a dozen. As well as buying mixing/dispensing nozzles, you have to initially, buy a hand held unit for operating the syringe. I can't remember how much that one was but I seem to remember it was something over £20.00. I 'bit the bullet' and spent the money, to see just how good the adhesive was, and how easy to apply, after I had seen a TV program, last year, about how Pagani supercar bodies were assembled. It is certainly easy to use. I still have quite a bit left and will be interested to see if it has solidified over time, in the applicator, so that it is no longer usable. I did try to use it 6 months after the first trial, and I was still able to clean up the dried glue on the end of the nozzle, and start applying new glue. I would still be very wary about using it to hold anything structural on a loco though. The only time I have used superglue is to hold something in place, that I can't clamp, to drill and tap for the proper fixings.
Bob.
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Post by 92220 on May 12, 2020 16:06:08 GMT
I currently use a Dyson DS7 for both dust and swafe, in the workshop. I've had 3 Dysons over the last 20 years. I can use it as a normal upright vacuum on the floor, or use the hose for the machinery. Works a treat considering the harsh works it has to do, and cheap, secondhand, on Ebay.
Bob.
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Post by 92220 on May 11, 2020 14:57:02 GMT
I would tend to agree with Roger's comments. One thing I learned very early on though....right back in my apprenticeship days....ALWAYS lubricate when using a die, for ANY size thread, even when lubricant is not normally used with a material, like brass. Nowadays I rarely tear a thread, and then it is always because I forgot to lubricate the die. It saves a lot of heartache!! Incidentally, this helps my modified dies to cut perfectly, too. By 'modified' I mean that I have ground off the backs of my dies until the threads finish as a full thread diameter and the conical entry that the manufacturers put on both sides of the die, is removed on the back, to allow me to cut the thread full depth, up to a shoulder. I cut the thread with the die the normal way around as far as I can, and then finish off, up to a shoulder, by turning the die around in the holder, to finish the last few threads. The lubricant I have always used is, like others have mentioned, Rocol RTD compound (for those unfamiliar, RTD = reaming, tapping and drilling).
Bob.
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Post by 92220 on May 10, 2020 11:06:20 GMT
Hi Norm.
Yes, ideally I needed 10 CFM or more, for my cabinet, and fitted the gun with the smallest nozzle that it comes with. I use glass beads almost exclusively now, and just change over to grit if I have to blast anything that the glass won't touch. I have a Hydrovane 501 but eventually had to add a second, smaller compressor to get the total air flow up. The set-up is just coping with the demand now. You can get away with having a lower airflow, but the compressor is working non-stop, and you have to stop blasting every half minute or so, to let the pressure build up again. As far as cyclone extraction goes, maybe a cheaper version would be a second-hand Dyson. I have one in the workshop for collecting swarf chips off the machines and floor.
Bob.
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Post by 92220 on May 10, 2020 8:37:44 GMT
Hi Roger.
Use the Medium grade beads...150-250 micron. Any smaller and it won't have a lot of effect on steel. That seems a good price. I also have a bag of aluminium oxide powder which I occasionally swap over to, for cleaning badly rusty steel. It is much more aggressive than glass beads, so shouldn't be used for delicate bits. It also leaves the surface chemically clear and any dampness in the air and steel will 'flash rust', getting a slightly rust coloured surface within around 15 seconds!!
Hi Jem. I have tried using sand. It only works well for a very short time. The sand crystals break down very quickly due to the pounding they get from the blasting.
Bob.
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Post by 92220 on May 9, 2020 13:02:35 GMT
Hi Roger.
I bought one of the floor mounted cabinets off Ebay 3 or 4 years ago, because it has a door in the end so longer items ould be blasted. It wasn't expensive, I thought, at £156.00 delivered, though I've just looked on Ebay and, at the moment, they are selling at around £250, for the same cabinet (eBay item number:254494553194). I must admit that when I blasted my frames assembly to get the old, incorrect paint scheme off, I did it outside but I bought a Badger mini sand blast gun, which is just like their cheap airbrush but adapted to spray fine grit. It actually worked a treat but was very very slow as the spray pattern is very tight. The cabinet might sound a bit expensive, but I use it a lot, to finish off parts. Also, it gets rid of those microscopic spots of rust that are not easy to remove, and are present on almost any piece of steel.
On siting the cabinet...mine is outside the workshop, in what was the garage part before I built the workshop inside it. I wouldn't have a sand blast cabinet anywhere near my machines because, despite the blasting being done in a cabinet, you still get very fine dust in the air from leaks around the boor, and the air vent. Also, if anyone does any blasting outside the cabinet for any reason, DO were a face mask!!
Bob.
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Post by 92220 on May 9, 2020 8:28:32 GMT
Hi Tim.
Yes I blast most steel parts that I make. I use glass beads, 1mm and smaller, at an air pressure of around 90 psi. I use glass beads because they don't damage the surface like aluminium oxide does. It takes a bit longer to clean a surface but it is a much better finish. It is surprising how small a part you can blast. Although the air is at 90 psi, it doesn't seem to have a great wind effect on the item being blasted.
Bob.
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Post by 92220 on May 9, 2020 8:22:49 GMT
Hi Andy.
Actually, in those days, vermillion paint was made from Mercuric Sulphide or Mercuric Oxide. The oxide gives it a slightly more orange shade. Nowadays they use other chemicals though, that are not toxic like Mercuric compounds. Oddly enough, Mercuric Oxide can be used to make Vermillion and a bright golden Yellow.
Bob.
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