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Post by doubletop on Aug 25, 2023 20:49:30 GMT
Here's the number plate for the Smokebox with the White background oversprayed Black, and the masks removed. Even though this was a struggle to get the mask off the Transfer Tape, it came out really well. The Whistle Servo Valve has undergone a few changes as a result of the failed tests recently performed. I wasn't happy with the PTFE Cone shaped valve and the lack of a guide. Here I've made a fluted guide with channels for the Steam and a 1mm section O-ring with a 3mm ID for the valve. The valve now seats on a 45 degree 0.5mm long chamfer, and the guide has been given a 5mm AF hex to make it easier to hold it while screwing the M1.6 bolt the holds the Diaphragm in place. I also noticed that the valve worked fine for the first few operations, and then became slow to come on. I think what's happening is that Steam is condensing in the 1.6mm copper pilot tube, and that has a much greater resistance to flowing than Steam. My potential solution is to have a permanently open vent on the Diaphragm cover which is much smaller than the Pilot Steam pipe. The idea is that plilot Steam can flow right through the small tube and escape to atmosphere, carrying the condensate away. There's a needle valve that can be adjusted so that there is enough pressure to move the Diaphragm. It might be possible to make the valve movement progressive by doing that. Whether it will still be possible to bleed a little Steam into the Cosmetic Whistles remains to be seen. I'll probably make the Whistles with an adjustable needle valve inside them so I can control how much comes out.  Servo valve assembly sectioned3 by Billy Roberts, on Flickr I'll give this a try tomorrow, Roger How did the test go? Looking at your picture above I can't help thinking that for it work the area of the diaghram on the actuating side needs to be larger than the main steam inlet side. Otherwise the lower volume, and possibly slightly lower pressure,steam will struggle against the higher volume of the main steam inlet. I can see that the area of the main steam side is reduced to some degree by the fluted shaft, but not by much. What you may experience is a lazy opening of the valve but not the sharp opening you would like. Maybe just reduce the diameter of the cavity on the main steam side? With the bleed you are suggesing I doubt whether it would work at all. If you are going to do that you may want to think about a ball bearing valve like used in automatic drain cocks. Good to see the vinyl cutting is looking promising. My cutter head and blades arrived yesterday I plan to try them on my Prusa 3D printer Pete |
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Post by Roger on Aug 26, 2023 20:54:32 GMT
Here's the number plate for the Smokebox with the White background oversprayed Black, and the masks removed. Even though this was a struggle to get the mask off the Transfer Tape, it came out really well. The Whistle Servo Valve has undergone a few changes as a result of the failed tests recently performed. I wasn't happy with the PTFE Cone shaped valve and the lack of a guide. Here I've made a fluted guide with channels for the Steam and a 1mm section O-ring with a 3mm ID for the valve. The valve now seats on a 45 degree 0.5mm long chamfer, and the guide has been given a 5mm AF hex to make it easier to hold it while screwing the M1.6 bolt the holds the Diaphragm in place. I also noticed that the valve worked fine for the first few operations, and then became slow to come on. I think what's happening is that Steam is condensing in the 1.6mm copper pilot tube, and that has a much greater resistance to flowing than Steam. My potential solution is to have a permanently open vent on the Diaphragm cover which is much smaller than the Pilot Steam pipe. The idea is that plilot Steam can flow right through the small tube and escape to atmosphere, carrying the condensate away. There's a needle valve that can be adjusted so that there is enough pressure to move the Diaphragm. It might be possible to make the valve movement progressive by doing that. Whether it will still be possible to bleed a little Steam into the Cosmetic Whistles remains to be seen. I'll probably make the Whistles with an adjustable needle valve inside them so I can control how much comes out. Servo valve assembly sectioned3 by Billy Roberts, on Flickr I'll give this a try tomorrow, Roger How did the test go? Looking at your picture above I can't help thinking that for it work the area of the diaghram on the actuating side needs to be larger than the main steam inlet side. Otherwise the lower volume, and possibly slightly lower pressure,steam will struggle against the higher volume of the main steam inlet. I can see that the area of the main steam side is reduced to some degree by the fluted shaft, but not by much. What you may experience is a lazy opening of the valve but not the sharp opening you would like. Maybe just reduce the diameter of the cavity on the main steam side? With the bleed you are suggesing I doubt whether it would work at all. If you are going to do that you may want to think about a ball bearing valve like used in automatic drain cocks. Good to see the vinyl cutting is looking promising. My cutter head and blades arrived yesterday I plan to try them on my Prusa 3D printer Pete Hi Pete, I think there are a few burrs on the moving element, I need to tidy that up a bit more, The Diaphragm is also a bit worse for wear, so I'll make another. The first couple of actuations were fine, then it got stuck closed. I too wondered about the areas, but so far it doesn't appear to be a problem. That's not to say that it will be reliable as designed. I've based the idea on an article that someone kindly sent me, so presumably they got it to work. I need to get it made properly and do some more tests before plotting the next course of action. The bleed is only supposed to be a small amount, so it will be interesting to see how that works out. I don't think you can make a diaphragm with a different OD on the inside. I think the only way to improve the force is to increase the diameter of the central valve. I can certainly do that. I've wound a softer spring for the Vinyl cutter and calibrated that into a new pressure table. I've designed a small test piece to prove the alignment targets, so hopefully I'll do that tomorrow. Good luck with the 3D printer. The cutting forces are really small, 50g for 0.2mm Vinyl seems about right. I've received the low tack Transfer Tape now, so I can hopefully get the patterns onto the work and make then stay there this time! All good fun. |
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Post by doubletop on Aug 26, 2023 21:16:27 GMT
Of course isn't it the size of the fixed area that defines the force exerted so a large washer on the actuator side and a small washer on the main steam feed side? I'm trying to be a cheapskate and not purchase the F360 plugin but use Inkscape and use the free Laser extension with Prusa Mk3s Vivyl cutter tweaks (https://cults3d.com/en/3d-model/art/prusa-mk3s-vinyl-cutter). I'm having a devil of a job trying to get them to work together, but in a dialogue on Github with the Laser extension developer. Otherwise it is cough up the $10 for the F360 plugin. Pete |
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Post by Roger on Aug 27, 2023 7:05:45 GMT
Of course isn't it the size of the fixed area that defines the force exerted so a large washer on the actuator side and a small washer on the main steam feed side? I'm trying to be a cheapskate and not purchase the F360 plugin but use Inkscape and use the free Laser extension with Prusa Mk3s Vivyl cutter tweaks (https://cults3d.com/en/3d-model/art/prusa-mk3s-vinyl-cutter). I'm having a devil of a job trying to get them to work together, but in a dialogue on Github with the Laser extension developer. Otherwise it is cough up the $10 for the F360 plugin. Pete Yes, but you can't have a different fixed area on two sides of a diaphragm. Putting a different washer just spreads the same load differently. A larger valve is the only way to remove area from the high pressure side. Looking at the drag knife, it's only a 0.25mm trailing offset, so for rounded features you can ignore it as long as the radius is more than say ten times that. For sharp corners, it's easy to extend the line on the sketch and then add an arc back to the next line. Obviously, if you're going to use it for a lot of compex small work, that's going to be painful though. |
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Post by doubletop on Aug 27, 2023 8:40:06 GMT
Yes, but you can't have a different fixed area on two sides of a diaphragm. Putting a different washer just spreads the same load differently. A larger valve is the only way to remove area from the high pressure side. Looking at the drag knife, it's only a 0.25mm trailing offset, so for rounded features you can ignore it as long as the radius is more than say ten times that. For sharp corners, it's easy to extend the line on the sketch and then add an arc back to the next line. Obviously, if you're going to use it for a lot of compex small work, that's going to be painful though. Of course I'm under thinking this, I'll shut up. I've got the Inkscape software extension working and an initial lash up of the cutter head in the Prusa. I went to the local craft shop and got some Cricut vinyl but they had rolls of cheap stuff on offer so I'm using that as a starter. The software doesn't have the fancy swing out to deal with sharp angles and doesn't seem to need it. I think the swing out version is for cutters using Stanley knife like blades. I'm coming to the conclusion that these blades with 0.25mm offset trail OK for our purposes and don't even need aligning for the initial direction of travel the first step gets then aligned before they've cut anything. I'll save cluttering up your thread with my efforts and be following yours with interest. Pete |
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Post by Roger on Aug 27, 2023 9:23:54 GMT
Yes, but you can't have a different fixed area on two sides of a diaphragm. Putting a different washer just spreads the same load differently. A larger valve is the only way to remove area from the high pressure side. Looking at the drag knife, it's only a 0.25mm trailing offset, so for rounded features you can ignore it as long as the radius is more than say ten times that. For sharp corners, it's easy to extend the line on the sketch and then add an arc back to the next line. Obviously, if you're going to use it for a lot of compex small work, that's going to be painful though. Of course I'm under thinking this, I'll shut up. I've got the Inkscape software extension working and an initial lash up of the cutter head in the Prusa. I went to the local craft shop and got some Cricut vinyl but they had rolls of cheap stuff on offer so I'm using that as a starter. The software doesn't have the fancy swing out to deal with sharp angles and doesn't seem to need it. I think the swing out version is for cutters using Stanley knife like blades. I'm coming to the conclusion that these blades with 0.25mm offset trail OK for our purposes and don't even need aligning for the initial direction of travel the first step gets then aligned before they've cut anything. I'll save cluttering up your thread with my efforts and be following yours with interest. Pete Ok, that's useful to know. Agreed, for most of our work you don't need to worry about the offset. I did need it for the numbers on the mask for the number plate on the smokebox though, to get a sharp corner that could be weeded neatly. I'm using a 45degree plunge which I think helps the cutter swing round as it goes in. Do let me know how it turns out, I'm sure other members will be interested. |
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Neale
Part of the e-furniture
5" Black 5 just started
Posts: 283 
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Post by Neale on Aug 27, 2023 11:50:00 GMT
...at least one other following with interest!
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Post by Roger on Aug 27, 2023 12:06:18 GMT
Here's the result of reducing the force on the blade. The Vinyl is staying down on the backing, whereas before it was coming away in places. The cutting force required is very low. This was done with around 50grams, and it looks like you could go slightly lower. One person on a forum said he uses 30grams, so I might go down a little further.  PXL_20230827_095215141 by Billy Roberts, on Flickr Anyway, it was easy enough to weed. This is a test pattern to get a feel for lining up one mask with another, and to test how long I need to leave the paint to dry between coats and how soon the mask can be removed. The first mask is the one on the left. The idea is to leave the alignment rings in place when the rest of the mask is removed. When the subsequent masks are laid down, there's a hole in them for the alignment ring which is 0.2mm larger than the original mask. The reasoning is that I don't really want them to touch, and it's easier to see the differences in a gap.  PXL_20230827_100754240 by Billy Roberts, on Flickr Anyway, I tried transfering this with the new Low Tack Transfer Tape, and that's hopeless for the opposite reason to the High Tack one. It doesn't stick to the Vinyl at all, even though it sticks well to other things and to itself. I've just ordered some Medium Tack Transfer Tape, so hopefully that will do the trick. Rather than wait for that to arrive, I thought I'd have a go with the High Tack tape, but that's never going to work. This is the key to getting masks to work. You have to be able to peel them off when you need to, without stretching or pulling them out of position. We'll get there in the end. |
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Post by Roger on Aug 27, 2023 15:46:10 GMT
Here's a revised version of the Servo Valve with the valve element increased from 4mm to 6mm diameter. I've also increased the O-ring section from 1mm to 1.5mm because there's more force on it now, and I've moved the return spring to the outlet side which I think is a better option. This should require much less pressure to operate, so I think it will be more reliable. Let's find out!  Servo with 6mm valve by Billy Roberts, on Flickr |
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Post by Roger on Aug 28, 2023 16:19:46 GMT
The body needs a new larger valve, so it's been bored out and tapped M8 x 0.75 (fine) so a piece of Brass bar can be threaded and held in with High Temperature Loctite.  PXL_20230827_194231963 by Billy Roberts, on Flickr This is the new Valve Guide with clearances for the Steam to pass by.  PXL_20230828_111112514 by Billy Roberts, on Flickr That was inverted and the hex added.  PXL_20230828_112939100 by Billy Roberts, on Flickr I'm using a 4mm x 1.5mm section Silicone O-ring for this test.  PXL_20230828_113448432 by Billy Roberts, on Flickr Again, this worked great for a few times and then stuck open. When forced into the closed position, it still leaked. I think this may be due to the 0.5mm thick Silicone sheet being used for the diaphragm. I can't do the centre bolt up much because it squashes the Diaphragm into an odd shape. I've ordered some of this 0.4mm Nitrile/Nylon sheet which is designed for the purpose. However, that's not ideal because the temperature is a bit high. Anyway, I'll give it a try, and if that's not any good, I'll knock up a simple press tool and make a metal Diaphragm from some Shim material. I've got some Brass, Stainless Steel, Beryllium Copper or Titanium Sheet to experiment with if it comes to that. I don't need much movement so I think that would work. |
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Post by Roger on Aug 28, 2023 19:50:38 GMT
While I'm waiting for parts to arrive, I'm going to have to address some issues with assembling and disassembling the Locomotive. Here's a shot of the underside with some unions that need to be reached with spanners so that I can get the Boiler on and off. The pipe that comes across above the Eccentric fouls the Blowdown valves, so that needs to come off. You can reach the Inline Clack Valve with a spanner, but you can't get enough travel to get it on and turn it to get another flat.  PXL_20230828_193013091 by Billy Roberts, on Flickr I tried to find a suitable spanner online, but couldn't see anything. In the end I decided to just make what I want. So here's a 7.5 degree / straight spanner to complement the usual 15 degree pattern. That should allow me to unscrew anything with just 7.5 degrees of available movement. If that isn't enough, I'll split that in half again, and make one that has 3.75 degrees and 11.25 degrees  10mm AF straight and 7.5 degree spanner by Billy Roberts, on Flickr Anyway, here's the setup on the usual 2x4x6 blocks to raise it enough to reach with the small cutters. I'm going to make two of them.  PXL_20230828_192118587 by Billy Roberts, on Flickr I'm making them from 4mm Gauge Plate, so it's not the quickest of processes. Here's a wobbly video to show the sort of feed and speed I'm using. I'm rouging them out with a 3mm 4 flute Carbide End Mill, finishing up with a 2mm to get into the corners a bit closer. This is exactly the sort of job that I needed the Cutting Oil Pump for, you need to keep it well lubricated if you don't want to blunt the cutter. I've used 6 nibs x 15mm long and 1mm high to keep the part in the stock .  PXL_20230828_192744309.TS by Billy Roberts, on Flickr |
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Post by Roger on Aug 31, 2023 20:58:26 GMT
Here is the first of the 10mm AF spanners with straight and 7.5 degree ends.  pxl_20230829_071447426 by Billy Roberts, on Flickr ... both finish machined...  pxl_20230829_152738251 by Billy Roberts, on Flickr ... you can see the Nibs from the underside.  pxl_20230829_152743386 by Billy Roberts, on Flickr I need to finish the handles by thinning them down with a file. I'll sort that out later.  pxl_20230829_211345326 by Billy Roberts, on Flickr Anyway, useful though those will be for maintaining the more difficult to reach Union Nuts, I decided that the feed from the Axle Driven Pump had to be re-routed else it was going to be a nightmare to assemble and maintain. Here you can see the new pipe from the middle of the Tee going down to another union nearer the bottom of the frame. This view is from the top.  PXL_20230830_163502568 by Billy Roberts, on Flickr Here's a similar view, but you can just make out the Inline Clack valve at the end of the pipe heading down from the Tee.  PXL_20230831_185457880 by Billy Roberts, on Flickr The Inline Clack is at an angle so that it misses the moving parts of the Eccentric. The pipe then carries on under the bearing for the Hydraulic Damper and then back up close to the Horn so it misses the Blowdown Valve. Although it looks like it blocks access to the Cap Screws on the bearing, it can actually be moved far enough to get an Allen key in there... just.  PXL_20230831_185429150 by Billy Roberts, on Flickr A quick 'sanity check' to see if it misses...  PXL_20230831_185639870 by Billy Roberts, on Flickr ... and that looks fine now. However, the delicate little Tee for the junction with the Injector pipe is now in the wrong place, so that has to be fixed.  PXL_20230831_190324265 by Billy Roberts, on Flickr I can shorten one of the pipes, but the tricky one with the double bend and the Injector flange is too short. So here's another one of those, the first bend being easy...  PXL_20230831_193014936 by Billy Roberts, on Flickr ... but getting up close to that for the reverse bend is more fiddly.  PXL_20230831_193201924 by Billy Roberts, on Flickr  PXL_20230831_193249544 by Billy Roberts, on Flickr I managed to gingerly desolder the little Tee piece without damaging it. It's been assembled with High Temperature Silver Solder, so it only had to get to a dull Red heat to get the old pipes out. I used the shank of a drill in the side hole to carefully pull that off when it was hot enough. Holding it with pliers would likely have crushed it. Anyway, here are the bits that need to be tidied up and re-assembled.  PXL_20230831_195244553 by Billy Roberts, on Flickr The flange was easy enough...  PXL_20230831_202326012 by Billy Roberts, on Flickr ... but holding the Tee piece for the 5mm reamer needs a fixture really. Here the 3D printed one that took all of 5 minutes to design. It's printing now, so I'll do that in the morning. The print is only going to take 36 minutes, but It's late.  3D printed Tee fixture by Billy Roberts, on Flickr I'm much happier with this now, it's going to be so much easier to get the Boiler off and the Inline Clack is now accessible from the bottom. I'll post some pictures when it's all together. |
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Post by Roger on Sept 1, 2023 22:12:55 GMT
Here's the 3D printed fixture for reaming the Silver Solder out of the holes in the Tee fitting.  PXL_20230901_093658933 by Billy Roberts, on Flickr The fixture can hold it in the three positions needed  PXL_20230901_093852283 by Billy Roberts, on Flickr This is the Injector outlet fitting going onto the new pipe...  PXL_20230901_102813369 by Billy Roberts, on Flickr ... which came out really well, but sadly was on upside down, so that had to be removed and machined again.  PXL_20230901_104607761 by Billy Roberts, on Flickr This is the right way round this time!  PXL_20230901_111119359 by Billy Roberts, on Flickr The setup for Silver Soldering the Tee was a bit fiddly, I was using the blowtorch away from the wooden packing!  PXL_20230901_134515354 by Billy Roberts, on Flickr  PXL_20230901_134734632 by Billy Roberts, on Flickr The Silver Solder didn't run round the bottom as neatly as I would have liked, so that was cleaned up and re-fluxed so it could be heated again, using gravity to encourage it to flow to the underside of the Tee.  PXL_20230901_141600073 by Billy Roberts, on Flickr This is what that looks like once cleaned up.  PXL_20230901_145953483 by Billy Roberts, on Flickr The exact positions of all of the bends and the angle of the flange are all important because there's so little room to play with.  PXL_20230901_150005793 by Billy Roberts, on Flickr This is how it looks from the underside. You can see the Inline Clack is accessible even though it's a bit busy down there. The slimline spanners will make that easier.  PXL_20230901_150428217 by Billy Roberts, on Flickr  PXL_20230901_150437795 by Billy Roberts, on Flickr It misses the Ash Pan which comes further forward than the Boiler Throatplate.  PXL_20230901_150512685 by Billy Roberts, on Flickr This pipe is taking the output from the Axle driven pump, through a non-return valve and feeding it into the Output pipe from the RH Injector. The vertical pipe gous through the Pannier Tank, with the coupling hidden inside the tube,  PXL_20230901_150959186 by Billy Roberts, on Flickr So that was a lot of effort, but well worth it to make getting the Boiler on and off easy. Now I can get back to preparing the Locomotive for the Midlands Show which is fast approaching. |
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Post by Roger on Sept 2, 2023 21:34:25 GMT
There's a M1.4 bolt that screws an angle bracket into the Frame, and my Box Spanners are a little too short. So I decided to add a short 2.5AF hex to the end of my M1.4 and M1.6 box spanners so that they can be used to make an extension...  PXL_20230901_202601443 by Billy Roberts, on Flickr ... like this.  PXL_20230902_212026423 by Billy Roberts, on Flickr I also need to fit some M1.4 nuts on the bottom of the assembly, and that was going to be way too filddly. So here's a 2mm AF hexagonal pocket going into a piece of 2mm Steel plate to make a holder for the nut. It was first drilled through with a 1.9mm drill, and roughed with a 1mm cutter. Finally, the pocket was finished with a 0.5mm Carbide PCB cutter using 2mm/min feedrate and 0.025mm depth of cut.  PXL_20230902_125054057 by Billy Roberts, on Flickr That fits a bolt head nicely, so now the profile is worth machining.  PXL_20230902_125030628 by Billy Roberts, on Flickr The 2mm cutter was pretty worn, but good enough to get the job done.  PXL_20230902_164801601 by Billy Roberts, on Flickr  PXL_20230902_201448500 by Billy Roberts, on Flickr This one is easy to get to , but the rear one is close to the frame.  PXL_20230902_171156001 by Billy Roberts, on Flickr Here's one side finished, using 7 x M1.4 and 2 x M1.6 Blacked bolts. This detail isn't to scale because the full size locomotive has angled cylinders. Still, it gives the flavour of what's on 1501.  PXL_20230902_172911231 by Billy Roberts, on Flickr |
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Post by Roger on Sept 3, 2023 15:00:39 GMT
Rather than spend ages with a file to tidy up the Spanners, I decided to just define an elliptical cross section, blend the ends roughly on the CAD model and machine them. This is clocking up the handle to make sure it's parallel to the X-axis...  PXL_20230903_090214941 by Billy Roberts, on Flickr ... and I'm using a piece of HSS on the square end to give something to use the Edge Finder against.  PXL_20230903_090446028 by Billy Roberts, on Flickr Then it was roughed out in 0.5mm depth increments leaving 0.1mm all over...  PXL_20230903_095106512 by Billy Roberts, on Flickr ... at 1mm overlap..  PXL_20230903_110553504 by Billy Roberts, on Flickr ... before finishing with 0.1mm overlap  PXL_20230903_134258793 by Billy Roberts, on Flickr  PXL_20230903_143939278 by Billy Roberts, on Flickr The ends were blended with a file to finish it off. Far from perfect, but it's still more pleasing than the rectangular cross section, and less cumbersome in a tight space. PXL_20230903_143939278 by Billy Roberts, on Flickr Ok, it took several hours on each side, but overall, I spent a lot less of my time on it. |
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Post by Roger on Sept 3, 2023 18:31:51 GMT
This is the Medium Tack Transfer Tape I bought for the Lining Masks. It has handy Blue reference lines on it, which could prove useful.  PXL_20230903_182254006 by Billy Roberts, on Flickr Here's the sequence of masks, left to right.  PXL_20230827_100754240 by Billy Roberts, on Flickr I actually cut out a new one for the first mask because the corners weren't quite right. This came off the Transfer Tape just right. If you fold the Transfer Tape over to give a tight radius, the different parts of the mask stay attached to the job. This is the part I was most concerned about, next to getting it aligned.  PXL_20230903_175635221 by Billy Roberts, on Flickr The registration circles for the following mask have been masked off too, I don't want those lines on the final product.  PXL_20230903_181127182 by Billy Roberts, on Flickr I'll let it go off overnight and see if that's an appropriate length of time before removing the mask. |
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Post by Roger on Sept 3, 2023 19:41:19 GMT
Here's the new 0.4mm Nitrile/Nylon Diaphragm material being turned into the required shape. Step 1 is to punch the OD, then the first bolt hole.  PXL_20230903_102755097 by Billy Roberts, on Flickr Step 2 is to use one of the location pins to stop it from moving while the opposite hole is punched.  PXL_20230903_102829818 by Billy Roberts, on Flickr That has a location pin inserted too.  PXL_20230903_103330089 by Billy Roberts, on Flickr Now it can't go anywhere, the rest of the holes can be punched. I kept the lathe set ip with the OD turning tool set to 1.6mm and a 1mm drill in the Tailstock. Punching the holes with a soft punch damages it each time, so I just tidied it up in a few seconds.  PXL_20230903_104008967 by Billy Roberts, on Flickr  PXL_20230903_110442712 by Billy Roberts, on Flickr I steamed up the Test Boiler and gave it a try, and it worked brilliantly as the pressure came up. However, as it got higher, the valve stuck open. On examination, the centre screw had come undone, and that was stopping the valve from closing. There's a limit to how tightly you can do the centre screw before the Diaphragm starts to extrude outwards, so I decided to add a small spacer in the middle so that I could tighten the bolt up on that.  PXL_20230903_140804283 by Billy Roberts, on Flickr  PXL_20230903_141800642 by Billy Roberts, on Flickr I punched the centre hole out to 2.4mm to accommodate the spacer, shown here in Yellow.  Servo valve assembly sectioned4 by Billy Roberts, on Flickr That works great at low pressure, but then the valve opens partially by itself as the pressure gets up to 90PSI. I think the problem is that I've used a Silicone Rubber O-ring which is so soft that the Valve assembly moves sufficiently to bottom out on the top cover. I'll address that next and see if that's the issue. It does look promising though. The whistle responds really well to the Scale Pilot Valve, I just need to get it to work at all pressures now. I've ordered some Viton O-rings too, which ought to be a lot more rigid. Hopefully those will seal at low pressures. |
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Post by Roger on Sept 4, 2023 14:26:24 GMT
Here's the thick outer line that will be Grey on the real thing. There's one place at the bottom where the mask didn't stick properly.  PXL_20230904_072334169 by Billy Roberts, on Flickr Here's the mask for what would be the Cream insdie edge. The concentric circles are a huge help for lining up.  PXL_20230904_073931920 by Billy Roberts, on Flickr  PXL_20230904_082143916 by Billy Roberts, on Flickr  PXL_20230904_082336636 by Billy Roberts, on Flickr In the good places, the result is superb, but not satisfactory elsewhere.  PXL_20230904_134901273 by Billy Roberts, on Flickr I think there are two problems with this. Firstly, I think the paint needs to be thinner and only just enough to cover the base colour. You don't want a deep line, and you also want the surface to be very even. Secondly, I've been a bit mean with the amount of border no this test sample, and that's allowed the mask to move slightly. The border line between the two paint colours is precisely on top of each other, and I suspect that you lose a little width due to the cut. I've adjusted the inner line to be 0.1mm further out, so it has a better chance of butting up against the thicker line.  PXL_20230904_134913973 by Billy Roberts, on Flickr Anyway, that looks like it can be made to work, so I'll have another go with a sample with a bigger border and slight overlap. Of course, there's always the other option of just currint the lines from coloured Vinyl and sticking them on. |
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Post by Roger on Sept 4, 2023 21:46:31 GMT
Ok, this is the second attempt at a lining test piece. I've left a more generous border so the sides won't pull in as easily. I've also added 0.1mm to the outside of the very thin line. That may well still need attention, I'll just see how that works out. Obviously getting the lineup on a much longer line is going to be more difficult.  PXL_20230904_190907468 by Billy Roberts, on Flickr This Medium transfer tape is too strong really. I'm wondering if I can slightly weaken that by spraying it with a fine mist of water? I did iron it down good and firmly, so maybe I'll just put it down lightly next time. Anyway, after a bit of a struggle, I managed to get the Transfer Tape off...  PXL_20230904_191538853 by Billy Roberts, on Flickr ... and sprayed it with around 50% thinners. I set the Air Brush to a fairly fine spray that covered well, and did it in one smooth pass. I didn't want to put as much on as last time.  PXL_20230904_194113499 by Billy Roberts, on Flickr I then waited just two hours and pulled off the mask. This is much better than the last time. it's crisper and the paint isn't too high.  PXL_20230904_213252227 by Billy Roberts, on Flickr I'll let that go off overnight and then spray the next part. I'd probably wait several days before overspraying on the real thing. |
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Post by Roger on Sept 5, 2023 9:57:34 GMT
Hmmm... I'm still not happy with the tack of the Transfer Tape. I really need something that's between the Low tack and the Medium Tack tapes I've bought. I tried a few experiments with Low Tack Masking Tape and that seemed to work just fine. So I'm assuming that the adhesion Low Tack provides isn't something that different manufacturers agree upon.
The Low Tack one I bought was a paper backed one, and I don't like that. I've found another clear version which is Low Tack, so I've ordered some of that too. I'll get there in the end.
This is deinitely the key to successfully getting the masks onto the part with as little distortion as possible. I'll wait for this to arrive before doing the next mask in the test part.
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