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Post by Roger on Dec 21, 2020 9:29:20 GMT
I haven't been around for a while, but I thought I'd look in to find out what the “Froude” has been up to. I wasn't disappointed, the thread as always is fascinating but now we are on to injectors ! So once you have reached ‘Base Camp’ (to use your climbing analogy) can you play around with pressures and the range of the injector. I have some that will pick up at around 40 psi and others that won’t go below 60. Each injector has around 40 psi of working range. It makes me wonder if the ‘Range’ could be extended ?? Hope this will lead to the knowledge to enable them to work in the 100-150 range Indeed there's a lot that can be done to change the pressures Injectors work at. Bob Bramson's book shows a graph of the various throat sizes for higher pressures as well as lower ones. The throat of the Steam Cone needs to be smaller to accommodate the higher pressure. There's a very long way to go in the experimentation of my design, it's not going to be a short process. Making something that works under specific conditions isn't too hard. However, making something with a really wide working range is much more challenging when you've introduced a whole load of new variables.
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Post by Roger on Dec 21, 2020 22:25:59 GMT
This is the split collet fixture for holding the two different spacers so I can adjust their lengths more easily. 20201221_120245 by Roger Froud, on Flickr The pocket this end is only 0.4mm deep but it's plenty to get a good hold of the spacer. I've since increased the ID of the spacer at this end because it's easier to fit into the body if it's sitting on the nose of the One Piece Cone. 20201221_151123 by Roger Froud, on Flickr It's been a slightly frustrating day due to a number of things. The sleeve with the gap in the side appears to want to turn when the end caps are screwed up tight, so that's caused it to block the water inlet on at least one occasion. Clearly that puts the results of a lot of the tests into question. It looks like if I assemble the parts in a particular order that this doesn't happen, but it's not very satisfactory. I may make the spacer into a lantern shape so it doesn't matter which way round it goes. That will cause some restriction, so I'll have to weigh up the options. Obviously that would be a lot more time consuming to make. If I can develop the design using a simpler one and then just make the ones required for the real thing, then that would help. We'll see. 20201221_145814 by Roger Froud, on Flickr I also found some debris in the throat of the cone, and also the feed water hose was leaking again, although not a great deal. However, any leaks are bad news, so I'm making a longer Copper pipe for that so it doesn't get so hot where the plastic pipe is, and I'm beefing up the end with a barbed sleeve so the pipe doesn't get crushed like it's done now. So I haven't got it to pick up once today, even though I've revisited the spacer length that worked before! Until I can reproduce that repeatedly, I can't really make any progress. Still, on the positive side, I now know how to go about getting the cones and spacers in and out without having to remove the injector. I've also created a spreadsheet that helps me work out the spacer lengths and Regulation gap. It certainly hasn't been a wasted day, but it would have been good to have got a little further in figuring out the design parameters rather than fire fighting.
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Post by David on Dec 21, 2020 23:01:45 GMT
Making something that works under specific conditions isn't too hard. However, making something with a really wide working range is much more challenging when you've introduced a whole load of new variables. But you don't need a *really* wide working range. Given many people have pumps of one sort or another an injector that works from 60 - 100 psi, or even pick up from 70 psi would be good enough, as long as it does work and is not intermittent or otherwise prone to failure. If you start using one below that you'll kill the pressure anyway and it will stop working and you won't be going anywhere on track under steam power. I get the challenge of making a really good one. But I wouldn't let it stop you getting out on track because it's not the world's best injector. If it works when you need it to, that's way more useful than working when you don't need it or not being reliable. One of mine sometimes picks up at 40 psi, which is nice because I don't have a pump, but at that point my run is over anyway.
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Post by Roger on Dec 21, 2020 23:13:28 GMT
Making something that works under specific conditions isn't too hard. However, making something with a really wide working range is much more challenging when you've introduced a whole load of new variables. But you don't need a *really* wide working range. Given many people have pumps of one sort or another an injector that works from 60 - 100 psi, or even pick up from 70 psi would be good enough, as long as it does work and is not intermittent or otherwise prone to failure. If you start using one below that you'll kill the pressure anyway and it will stop working and you won't be going anywhere on track under steam power. I get the challenge of making a really good one. But I wouldn't let it stop you getting out on track because it's not the world's best injector. If it works when you need it to, that's way more useful than working when you don't need it or not being reliable. One of mine sometimes picks up at 40 psi, which is nice because I don't have a pump, but at that point my run is over anyway. Hi David, I don't think it would be acceptable as it was, the range was very limited and I could see that the flow was unstable. I need to figure out what elements of the design work and what don't. If it covers 50-90psi that would suffice, but I'm nowhere near getting it to that at the moment. I'm just going to have to be patient and methodical in figuring out what that issues are.
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Post by Roger on Dec 22, 2020 11:53:42 GMT
I'm going to make a few changes to give me more options for testing and solve the issue of the water inlet becoming blocked if the gap in the spacer moves when it's installed. It makes it more complex at this stage, but it can be stripped down to a simpler design later when I know what's needed and what isn't. I've made the spacer slightly shorter, made the flange on the Steam Cone thinner and used the room saved to include the Blue spacer. That means I only have to make the Squirrel cage type spacer once. You'll also notice that I've added another Red O-ring on the One Piece Cone. More of that below. I'll probably take liberties with the scale body and move the water inlet another 0.5mm to the left. It's already a little further along than it should be, and a little more won't really show. Sectioned injector with squirrel cage by Roger Froud, on Flickr The bars are pretty slender, the slots are 1mm wide, leaving 0.3mm at the ends. However, it's made from Stainless Steel so it ought to be strong enough in compression for this purpose. I just want to minimise the water resistance at this point. It may well turn out that I can just have a ring of holes. Squirrel cage spacer by Roger Froud, on Flickr Another area I'd like to experiment with is whether a separate valve for the Combination Cone gap is necessary. At the moment there isn't one, and I really don't want to split this into separate cones to add one. So my thought on that is to use a Silicone O-ring in a U-shaped goove with enough clearance over the outside for it to lift and allow water and steam to escape. Obviously, without some sort of containment, the O-ring would just shoot down the neck towards the overflow. Again, this may be completely unnecessary or the implementation could later be simplified. However, at this stage it's all about discovering what works and what doesn't. If I leave the O-ring off, I'm essentially back to what I have now. It just allows me to try out the idea. One piece cone with valve by Roger Froud, on Flickr This is a closeup of how that looks. I've been looking one of the Chiverton designs, and it's clear that you don't need a huge cross section for the valve. You want to avoid a restriction down at the diameter of the throat, but the volume increases massively as the radius increases. My feeling is that the O-ring would hardly lift at all to allow for a considerable release of water and steam. O-ring valve by Roger Froud, on Flickr Anyway, this is the stuff I live and breathe for, so please humour me while I play.
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Post by delaplume on Dec 22, 2020 20:36:03 GMT
Hi Roger,
When I left school I wanted to go into the R & D at Swindon or Crewe----- but the winds of fate took me elsewhere........I'm following this with great interest....keep it up !!
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Post by andyhigham on Dec 22, 2020 21:13:35 GMT
I did my first year apprenticeship "off the job training" at college across the road from Horwich Loco Works
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Post by Roger on Dec 22, 2020 22:41:37 GMT
I heated up the old flange and pipe assembly to save the flange, then turned the register back into it. Here it is again, with the usual bucket of Tippex to keep the Silver Solder where it's needed. 20201222_174852 by Roger Froud, on Flickr I've given it a little over a turn of wire this time for a slightly larger fillet since it's now longer and needs to be stronger. 20201222_174904 by Roger Froud, on Flickr 20201222_214821 by Roger Froud, on Flickr I've fitted all M1.4 bolts this time. 20201222_222329 by Roger Froud, on Flickr Back to the new One Piece Cone with the O-ring as a valve. This is the 3D model for the 1mm diameter Form tool. I've shown this before, but here you can see that the machining is not following the profile. The Solid model is actually created at 8 degrees from the X/Y plane and the profile projected onto that plane. The Form tool is set up at 8 degrees on my standard wedge made for this purpose, and the profile is machined at that angle. The semi-circle in this case is obviously not a semi-circle any more, it's an ellipse. However, when it's used flat, it creates a semi-circle while giving the front the necessary clearance. It took a bit of time to figure out how to do this the first time, but I now have a standard model that I copy and save with the new profile each time I make a new one, and it takes next to no time to do. I've just shown the finishing pass here, there are more roughing ones done first. O-ring valve form tool by Roger Froud, on Flickr Here I've just run a Diamond needle file across the top to knock off the small burr. 20201222_220435 by Roger Froud, on Flickr And here it is hardened and tempered. 20201222_222250 by Roger Froud, on Flickr So not huge progress today, but it's coming along.
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Post by timb on Dec 22, 2020 22:52:54 GMT
Meanwhile back in the real world, I grind tools on my Quorn that I made to questionable accuracy! Excellent work Roger, truly superb, well done!
Tim
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Post by jma1009 on Dec 23, 2020 0:38:11 GMT
Roger:-
"I've been looking one of the Chiverton designs, and it's clear that you don't need a huge cross section for the valve. You want to avoid a restriction down at the diameter of the throat, but the volume increases massively as the radius increases. My feeling is that the O-ring would hardly lift at all to allow for a considerable release of water and steam."
I haven't a clue what you are attempting to explain here Roger!
As with valve gear stuff, you do have to be clear and precise.
As an aside, I would consider a proper water inlet valve to be a prerequisite. For a multitude of reasons. And you are correct that any air being drawn into the water feed will cause serious problems.
Cheers, Julian
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Post by Roger on Dec 23, 2020 8:58:03 GMT
Roger:- "I've been looking one of the Chiverton designs, and it's clear that you don't need a huge cross section for the valve. You want to avoid a restriction down at the diameter of the throat, but the volume increases massively as the radius increases. My feeling is that the O-ring would hardly lift at all to allow for a considerable release of water and steam." I haven't a clue what you are attempting to explain here Roger! As with valve gear stuff, you do have to be clear and precise. As an aside, I would consider a proper water inlet valve to be a prerequisite. For a multitude of reasons. And you are correct that any air being drawn into the water feed will cause serious problems. Cheers, Julian Sorry about that Julian, here's a better explanation. I think this is a picture Don9F sent me of a Chiverton Injector, apologies if I've got that wrong. The direction of flow is from left to right, so the disc valve on the left is for the gap in the Combining Cone and the one on the right is for the delivery overflow. Neither of these are very large. 3Y4muaA by Roger Froud, on Flickr The point I was making about the free flow of overflow will hopefully make more sense if you look at the section below. The red arrow showing Air going in is where the overflow in the middle of the Combining Cone comes out of. The diameter of the throat there is pretty small and you really need a good sized clearance just above that diameter to make room for the overflow. This is why conventional cones don't look like the picture below, but spread out just above the gap. However, the total volume you need to get rid of isn't that great, there's just that pinch point to worry about. Step 4 by Roger Froud, on Flickr In this section, the gap is created by drill ways but the O-ring is pretty close to the middle. I've already seen it pick up when the conditions were right, so I don't think there's a problem with the amount of volume I can pass. If there is, I can always drill slightly larger holes that stop short of the throat diameter. That's more complexity that I'd rather avoid though. The main thing is to get it working satisfactorily first and then pare back on the more complex features of the design to end up with the simplest form that works. O-ring valve by Roger Froud, on Flickr This is why I don't think the proposed O-ring valve will have to lift very far, because the volume of water and steam isn't that great. Hopefully that's a bit clearer. It may turn out that I don't need the valve at all, but I have a feeling I probably will need it. I've just got confirmation of the dispatch of the water valve and fittings, so hopefully I'll be able to get this all back up and running in the next day or two.
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Post by Roger on Dec 23, 2020 10:14:44 GMT
Meanwhile back in the real world, I grind tools on my Quorn that I made to questionable accuracy! Excellent work Roger, truly superb, well done! Tim Thanks Tim, I think a Quorn is a very useful tool indeed. You could certainly grind a tool like this on one. Alternatively, a hole drilled in a piece of Gauge Plate then cut in half and sharpened would make a female form tool with which to make a male version. You certainly don't need to do it the way I did. However, that makes perfect sense for me since the machine is sitting there.
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Post by delaplume on Dec 23, 2020 11:11:43 GMT
With regards to air being drawn in}---- no more "Chirpy--chirpy----cheap-----cheap"...........never did like that song anyway LoL !!
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Post by Roger on Dec 23, 2020 13:09:53 GMT
With regards to air being drawn in}---- no more "Chirpy--chirpy----cheap-----cheap"...........never did like that song anyway LoL !! Me too Alan. As I understand it, the Chirp is the ball being unseated by instability in the flow, causing a momentary unseating of the ball while it overflows and restarts. I believe the ball either bounces or rolls around the seat before sitting down. Either way, it isn't happy.
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Post by delaplume on Dec 23, 2020 13:19:04 GMT
Quote}---"I believe the ball either bounces or rolls around the seat before sitting down. Either way, it isn't happy"......Exactly...How many of us can relate to that !!!
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Post by Roger on Dec 23, 2020 22:49:09 GMT
This is the Squirrel Cage type of spacer for the Steam Cone where the inlet water has to pass through. 20201223_121907 by Roger Froud, on Flickr This it turning out to be a useful way to use the High Speed Spindle, ie standing out in front of the main spindle. The 4th axis can use the front Tee slot so it's easy to reach the centre line. 20201223_122004 by Roger Froud, on Flickr This is how it turned out. I'll have to be gentle not to crush it. 20201223_151013 by Roger Froud, on Flickr This is a parting tool being ground down to 1.1mm for the O-ring grooves. 20201223_155501 by Roger Froud, on Flickr I've marked the outside of the diameter with black felt tip so I could see when it first touched. I'm forming the groove before drilling the holes, but that might not be the best strategy. We'll see. 20201223_162656 by Roger Froud, on Flickr I'm making this one from Brass since it's just for experimental purpose. The hole was drilled with the slow helix Brass drill to 16mm, 0.5mm at a time. 20201223_164451 by Roger Froud, on Flickr The 0.8mm holes were drilled into the bottom of the curved groove. 20201223_171543 by Roger Froud, on Flickr 20201223_171554 by Roger Froud, on Flickr 20201223_173432 by Roger Froud, on Flickr Finally, the eight slots for the water to escape were machined with a 1mm cutter. 20201223_213159 by Roger Froud, on Flickr Then it was reamed as before... 20201223_215139 by Roger Froud, on Flickr ... and it ended up like this after finishing the Delivery end. 20201223_222606 by Roger Froud, on Flickr
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Post by jma1009 on Dec 23, 2020 23:43:54 GMT
Hi Roger,
Lots that is fascinating!
I would tentatively suggest a further test piece of the combining cone with delivery cone masterpiece of yours with the drilled holes between the 2 halves of the combining cone made into slots. I think there is a restriction here for self starting on a range of steam pressures (and auto restarting).
Effectively, you have a sort of Sellers type injector rather than the Holden and Brooke type that has become widely used.
Cheers, Julian
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Post by Roger on Dec 24, 2020 0:08:01 GMT
Hi Roger, Lots that is fascinating! I would tentatively suggest a further test piece of the combining cone with delivery cone masterpiece of yours with the drilled holes between the 2 halves of the combining cone made into slots. I think there is a restriction here for self starting on a range of steam pressures (and auto restarting). Effectively, you have a sort of Sellers type injector rather than the Holden and Brooke type that has become widely used. Cheers, Julian Hi Julian, Fun isn't it! Here's a cross section at the middle of the 'gap' in the Combining Cone so you can see the way the drilled holes completely remove the material at the throat. This wasn't really clear on the other models I've shown. You can see that there's actually a clearance all around the throat which I'm hoping will be enough to let the Steam and water escape. The only points that stop this falling apart are the dark blue coloured areas. One piece cone section at gap by Roger Froud, on Flickr
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Post by delaplume on Dec 24, 2020 3:16:29 GMT
It wasn't untill I saw the bottom end of a Tipp-Ex bottle in one of your recent photos that I realised how small these items are ( I just happened to have a bottle in front of me )....
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Post by runner42 on Dec 24, 2020 5:33:26 GMT
Hi Roger,
is my eyes playing tricks on me? Viewing your one piece cone section at gap drawing appears irrational and can't exist in practice. To me the centre spoked part is an isometric view that is at 90 deg to the axis of the remainder of the item.
Brian
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