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Post by delaplume on Feb 7, 2021 2:49:35 GMT
Hello Gary....
Ah yes cavitation--- the Submariner's arch enemy !!
I wonder if using Heavy Water would make a difference to Roger's experiments ??.........LoL
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Post by Roger on Feb 7, 2021 10:59:56 GMT
Another day, another cone... Here's a couple of new ideas I've not tried before. This design is attempting to get the overflow in as narrow a band as possible while reducing the resistance to the flow of steam and water. The first row has four holes of 0.6mm, the second row has four holes of 0.5mm tucked in closely. I've made them different sizes because I want the biggest possible size without the edges overlapping. The holes further upstream are on a larger taper diameter so they can be bigger. The biggest difference though are the pocket clearances behind the holes. Conventional cones have a narrow gap between them, but the rest of the cone is then cut away to give a much wider space for the overflow. I can't do that because the cone would end up in two pieces. However, I can give more space using pockets because that leaves material to hold it all together. I've done this to all of the holes, including the ones at the delivery cone end. In reality, that end could be necked down instead because the taper is much smaller at that end. However, I can do it very easily with the same tool, so I might as well use it. I've shown the bottom of the pockets as being flat, but they will actually be 120 degrees from the drill point.  Cone34 by Georgia Montgomery, on Flickr |
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Post by RGR 60130 on Feb 7, 2021 13:19:55 GMT
Rather than sticking to round holes, would it be possible to use something like a very small slitting saw fed in at 3 points 120 degrees apart? I suspect the O ring groove would prevent the spindle of the saw getting close enough though.
Reg
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Post by Roger on Feb 7, 2021 14:37:15 GMT
Rather than sticking to round holes, would it be possible to use something like a very small slitting saw fed in at 3 points 120 degrees apart? I suspect the O ring groove would prevent the spindle of the saw getting close enough though. Reg Hi Reg, I thing you could do something along those lines, or cut slots using small PCB burrs. I'm hoping to boil this down to something that anyone can make though, so I'll probably stick to drilled holes. |
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stevep
Elder Statesman
Posts: 1,073
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Post by stevep on Feb 7, 2021 18:11:46 GMT
SNIP I'm hoping to boil this down to something that anyone can make though, so I'll probably stick to drilled holes. Anyone can make! That is, anyone with your skill, a 20,000 RPM auxiliary head for the mill, plus a 4th axis CAM attachment! Well done Roger - keep going. It's all fascinating stuff. |
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Post by Roger on Feb 7, 2021 19:08:37 GMT
SNIP I'm hoping to boil this down to something that anyone can make though, so I'll probably stick to drilled holes. Anyone can make! That is, anyone with your skill, a 20,000 RPM auxiliary head for the mill, plus a 4th axis CAM attachment! Well done Roger - keep going. It's all fascinating stuff. Well, hopefully I can get it working on something that won't need all that kit. We'll see. |
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Post by keith1500 on Feb 7, 2021 19:56:23 GMT
Making this style of injector is an interesting thought. The bit that would flaw me would be making the tapered D reamers.
Mind you in a way I am surprised that sets of injector reamers are not available commercially ?
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Post by delaplume on Feb 7, 2021 20:59:26 GMT
My head spins at 20,000 just trying to understand the programming !!.......... but keep on Roger.
As General Melchett said to Blackadder}---"I'm right behind you"...
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Post by David on Feb 7, 2021 22:06:02 GMT
The CNC and 4ths axis aren't necessary for making 2 of them in non-scale bodies. Anyone making a more conventional injector would have everything required, probably even the rotary table/divider for the holes.
A few PCB drills from eBay so you can drill the radial holes are easy to get, but would take some care in use. Making the reamers is probably the worst of it, as it might be for the usual type.
Roger, the results of some of your experiments suggest you already have the equal of some commercial injectors. Why do you say the results aren't good enough yet? More range is better, obv, but would you take your current best result out on the track? I'm talking with the non-scale body, most of us couldn't make scale bodies anyway. Either we don't know what they look like or it wouldn't be worth the effort to make them.
Like Dave, I look forward to the updates with my morning coffee!
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Post by Roger on Feb 7, 2021 22:39:07 GMT
Making this style of injector is an interesting thought. The bit that would flaw me would be making the tapered D reamers. Mind you in a way I am surprised that sets of injector reamers are not available commercially ? Hi Keith, It's no different whatever style of Injectors you decide to make. The reamers are delicate, but you can contrive ways to make them with a little ingenuity. I guess the people who might sell you the reamers are the same folk that would prefer to sell you the finished product. |
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Post by Roger on Feb 7, 2021 22:45:08 GMT
The CNC and 4ths axis aren't necessary for making 2 of them in non-scale bodies. Anyone making a more conventional injector would have everything required, probably even the rotary table/divider for the holes. A few PCB drills from eBay so you can drill the radial holes are easy to get, but would take some care in use. Making the reamers is probably the worst of it, as it might be for the usual type. Roger, the results of some of your experiments suggest you already have the equal of some commercial injectors. Why do you say the results aren't good enough yet? More range is better, obv, but would you take your current best result out on the track? I'm talking with the non-scale body, most of us couldn't make scale bodies anyway. Either we don't know what they look like or it wouldn't be worth the effort to make them. Like Dave, I look forward to the updates with my morning coffee! Hi David, It's all about stability and repeatability. Yes, some of the setups have been pretty good, but they are too fragile. By that I mean they don't always pick up cleanly or they require very fine setting of the regulation gap. Some work pretty well but the output is very unstable, even if they keep feeding with a dry overflow. What I'm looking for is a more robust setup where there's more flexibility in the adjustment and it still works smoothly over the full operating range. Somewhere in amongst these designs is a set of parameters that give the required performance, but I'm yet to find it. Most designs work after a fashion. If all you needed was 90-60PSI then that's accomplished by almost all the designs. As always, the devil is in the detail. |
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Post by chris vine on Feb 8, 2021 8:14:13 GMT
Noise:
Hi Roger, I think the basic singing sound from injectors starts from the steam condensing on the water. If you put a steam pipe into water, it makes a lot of noise, so there must be some sort of unstable way in which the steam condenses onto cold water. In a series of bangs, perhaps 2 or 5000 times a second. You can try it with a posh coffee machine which uses a jet of steam to froth the milk.
I think the chirping noise is hearing this sound, but modified by water moving inside. So you have a continuous high pitch sound, but with a drop of water inside the overflow or near it (IE between where the noise is made and the overflow) which is then sucked into the injector flow until another drop forms. How this happens I haven't got a clue!!!
Chris.
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Post by Roger on Feb 8, 2021 9:42:04 GMT
Noise: Hi Roger, I think the basic singing sound from injectors starts from the steam condensing on the water. If you put a steam pipe into water, it makes a lot of noise, so there must be some sort of unstable way in which the steam condenses onto cold water. In a series of bangs, perhaps 2 or 5000 times a second. You can try it with a posh coffee machine which uses a jet of steam to froth the milk. I think the chirping noise is hearing this sound, but modified by water moving inside. So you have a continuous high pitch sound, but with a drop of water inside the overflow or near it (IE between where the noise is made and the overflow) which is then sucked into the injector flow until another drop forms. How this happens I haven't got a clue!!! Chris. Hi Chris, I think this is the source of the harsh noise you hear at high pressure, and I agree that it's possibly a modification of that noise. However, I'd contend that the modification is to do with the ball seating and unseating. However, this noise subsides as the flow rate decreases, and below about 50psi, mine runs silently. One day I'll have to do some experiments with a traditional injector and find out once and for all. Removing the ball or pressing down on it while it's running ought to prove the point. |
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Post by chris vine on Feb 8, 2021 11:42:35 GMT
I have one injector which runs from 110 ish psi right down to a few psi. the gauge on the loco isn't registering at the low pressure it still feeds at.
Yes, it goes silent at the low pressures.
If you look at the overflow when it is like this, there is water in the overflow pipe and it either gets sucked in very slowly or runs out slowly, it depends on the setting of the water valve. You can get a drip to dangle on the end of the pipe and make it get bigger and smaller!
I wonder if when they go silent, there is a slug of water filling everything inside and around the cones so that you don't hear anything. Clearly there is less energy to make noise anyway at these low pressures.
Keep up with your wonderful experiments!
Chris.
PS, some of your mistakes in sizes etc, might shed light in unexpected ways! Don't forget the swiss clock maker who discovered stainless steel...
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Post by Roger on Feb 8, 2021 12:18:50 GMT
I have one injector which runs from 110 ish psi right down to a few psi. the gauge on the loco isn't registering at the low pressure it still feeds at. Yes, it goes silent at the low pressures. If you look at the overflow when it is like this, there is water in the overflow pipe and it either gets sucked in very slowly or runs out slowly, it depends on the setting of the water valve. You can get a drip to dangle on the end of the pipe and make it get bigger and smaller! I wonder if when they go silent, there is a slug of water filling everything inside and around the cones so that you don't hear anything. Clearly there is less energy to make noise anyway at these low pressures. Keep up with your wonderful experiments! Chris. PS, some of your mistakes in sizes etc, might shed light in unexpected ways! Don't forget the swiss clock maker who discovered stainless steel... Hi Chris, Does the injector you mention run dry without adjusting the water valve from 110 to a few psi? I have a clear hose on the overflow, so I can see the sort of thing happening that you describe with water stopping and moving briefly upwards as the Injector picks up. The overflow valve seems to seal really well, it doesn't continue to pull water back up the overflow once it's picked up. You may well be right about the whole body filling up around the cones on my design, but I don't think that can be happening on the Delivery overflow of a conventional one since it's open to the atmosphere. I think it's doubtful it would happen on the Combining Cone area too, but I suppose it could. |
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Post by chris vine on Feb 8, 2021 12:25:11 GMT
Hi Roger,
No, I have to regulate the supply of water at the lower pressures.
Interesting that you can see the same thing.
Even though it is open to atmosphere, I think it can fill up and just not fall out of the overflow. Just like a drinking straw holds liquid when you put your finger over the end.
None of this really helps with your vital internal cone dimensions, however if it adds to a thought process, then that might be useful.
Chris.
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Post by delaplume on Feb 8, 2021 14:55:45 GMT
quote}-------"You can get a drip to dangle on the end of the pipe and make it get bigger and smaller!"........Interesting how experiments always seem to throw-up useful by-products ....... lol !!
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Post by andyhigham on Feb 8, 2021 16:51:26 GMT
The way to answer the question of air drawn in being the cause of the chirping. Push a tube onto the overflow and immerse the end in a jar of water, just like bleeding brakes
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Post by Roger on Feb 8, 2021 18:16:33 GMT
Hi Roger, No, I have to regulate the supply of water at the lower pressures. Interesting that you can see the same thing. Even though it is open to atmosphere, I think it can fill up and just not fall out of the overflow. Just like a drinking straw holds liquid when you put your finger over the end. None of this really helps with your vital internal cone dimensions, however if it adds to a thought process, then that might be useful. Chris. Hi Chris, What sort of pressure does it go down to before you have to regulate the water? I see what you're saying about the finger over the straw. As you say, this all helps with modelling what's going on in our imagination. |
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Post by chris vine on Feb 8, 2021 21:13:21 GMT
exactly Roger,
I would say that it probably goes down to around 50 or 60 before regulating with the water valve.
I will try to run an experiment for you...
Chris.
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