|
Post by ettingtonliam on Oct 5, 2019 22:20:57 GMT
Admittedly I'm tone deaf, but I thought it sounded pretty good!
|
|
|
Post by Roger on Oct 5, 2019 22:21:57 GMT
Hi Roger, Sorry, your 'very wobbly video' didn't do it for me. When I try my own whistles on my big compressor at 60 psi they don't over blow jumping an octave but give a clear loud note without sounding asthmatic like yours did in the above clip. I should add that lest one suspect plastic provides a poor note quality consider any penny whistle. "2 out of ten, go to the back of the class" I say tongue in cheek, and know you will come up with something far more resembling full size in due course. And of course all GWR locos ought to have 2 whistles... see the first few minutes of the Ealing film Titfield Thunderbolt. I personally consider the pressure valve unnecessary, but Roy Amesbury was very keen on them on his last 2 steam locos. Cheers, Julian Hi Julian, Fair enough, but unless you sample a real whistle and play it back electronically, you're not going to make it sound like the real thing. Personally I rather like it, the tone is nice and deep and it's not shrill and jarring. To me it's just a whistle, nothing to get overly excited about so I'll probably use it or a variant that's a better print. It's a lot better than most I've heard! I might make a second one with a different tone at some point, but at the moment I can't really be bothered. I quite like the idea of a servo valve, it allows for a near scale valve on the turret and miniature piping which is easier to hide or at least pass off as scale. I don't think you could make a passable scale looking whistle valve to fit the turret and still pass enough steam to supply the whistle. I find it technically pleasing too, and it's interesting to design and make.
|
|
|
Post by steamer5 on Oct 5, 2019 22:26:24 GMT
Hi Roger, Don’t forget to check out Pete’s research on whistles.... modeleng.proboards.com/thread/12436/whistles-again?page=1I particularly like the idea of an steeped increased in diameter of the barrel? Would maybe easy to do in 3D print, which if I understand it correctly will drop the note down the scale, or is it up....either way make it deeper rather than the normal screacher! Cheers Kerrin
|
|
|
Post by Roger on Oct 5, 2019 22:41:57 GMT
Hi Roger, Don’t forget to check out Pete’s research on whistles.... modeleng.proboards.com/thread/12436/whistles-again?page=1I particularly like the idea of an steeped increased in diameter of the barrel? Would maybe easy to do in 3D print, which if I understand it correctly will drop the note down the scale, or is it up....either way make it deeper rather than the normal screacher! Cheers Kerrin Hi Kerrin, Gosh, that's a long and involved thread, I'm not sure I have the energy or enthusiasm to wade through all that. Yes, printing a different shape is easy enough, changing the diameter progressively or in steps is not a problem. Knowing what to design is another thing. There's a limit to how big it can be and still fit under the cab. I could manage a larger diameter, but not anything longer. Would is sound right with an even deeper tone? It's deeper than most I've heard. I'm usually the first to dive deep into R&D for this sort of thing, but I'm afraid it just doesn't interest me enough to do more than I absolutely have to.
|
|
Gary L
Elder Statesman
Posts: 1,208
|
Post by Gary L on Oct 5, 2019 23:01:20 GMT
Nah! I disagree. It is not far off the required note to my tin ear. It is 3 or 4 octaves high, but that can't be helped, it is down to the laws of physics- you can't scale sound. Under steam the note will be a bit different. Pretty good for a first attempt I would say, remarkable in fact. I don't think even Roger will opt for an electronic sound system to get a truly accurate sound Roger, if you arrange to drive it with your venturi device (using pure air?) you will need to recalculate the bell length. On the plus side, there has been lots of work done on organ pipes, so the tables can be relied on, whereas the steam calcs use a conversion factor and steam atmospheres can vary. -Gary If I blow it really hard, it whistles like this... 20191005_170008 by Timothy Froud, on Flickr ... but that doesn't seem to be the natural frequency. That's more like you get when you blow really hard on a recorder.... I'm sure we've all done that! Good point about the venturi though, I hadn't thought of that. I think I'll leave it at that, maybe try another print when the smaller nozzles I've ordered arrive. Hi Roger There is a condition called 'overblowing' which is what happens in your recorder example. It happens when the pressure supplied to the whistle is greater than it cope with, and you get a kind of nasty harsh shriek. But this video doesn't sound like overblowing to me. I think it is an approximation to the volume (if not the note) that you will get when you supply your whistle with steam. I guess your full airline pressure in the second video is a lot closer to the eventual steam pressure that you will get at the whistle than the first video was. The width of the steam slot ( not the mouth) has a role in this. You can correct a tendency to overblow by making the slot narrower (which usually means making a new whistle!) but you can control it by throttling the whistle valve a little when you blow. However if you make the slot too narrow, you will strangle the sound when you try to whistle at low boiler pressure (of course we never struggle for boiler pressure do we?) So as ever, the slot width is a compromise, and you don't have much scope to change it in the design of brass tube whistle which I sent you. It is largely by luck that thin brass tube happens to be available with a wall thickness that suits the average model engineer's steam whistle requirements! It is also by luck that the slot width is not terribly critical; you will only notice a problem if it is grossly wrong. I'm glad that you decided not to go with driving it by air. It is a feature of the 'variableness' of steam that it allows you to get different sounds by 'quilling' the valve, to get a 'crow' for example. There is a also a characteristic slight whoop when a steam whistle starts to blow which is caused by the whistle warming up. I don't believe either is possible with air, or not to the same extent (though organists among us might correct me). In fact these characteristics are noticeably absent in the first video, where you are 'quilling' (sort of) using the airline trigger to vary the pressure. I have a reservation about your whistle servo valve on this score; it will probably reduce the fine control of the sound that you need in order to get a really satisfying and realistic whistle blast. To be successful your servo needs to open proportionately to the pressure supplied from the manual valve, without fluttering and without going straight from full closed to full open. It will be interesting to see if it will do this. Great experiment though! Since whistles are a black art to many otherwise highly skilled model engineers, perhaps we will see a range of standard plastic whistles appearing on the market? Whoo nose? -Gary
|
|
|
Post by Roger on Oct 6, 2019 7:25:57 GMT
If I blow it really hard, it whistles like this... 20191005_170008 by Timothy Froud, on Flickr ... but that doesn't seem to be the natural frequency. That's more like you get when you blow really hard on a recorder.... I'm sure we've all done that! Good point about the venturi though, I hadn't thought of that. I think I'll leave it at that, maybe try another print when the smaller nozzles I've ordered arrive. Hi Roger There is a condition called 'overblowing' which is what happens in your recorder example. It happens when the pressure supplied to the whistle is greater than it cope with, and you get a kind of nasty harsh shriek. But this video doesn't sound like overblowing to me. I think it is an approximation to the volume (if not the note) that you will get when you supply your whistle with steam. I guess your full airline pressure in the second video is a lot closer to the eventual steam pressure that you will get at the whistle than the first video was. The width of the steam slot ( not the mouth) has a role in this. You can correct a tendency to overblow by making the slot narrower (which usually means making a new whistle!) but you can control it by throttling the whistle valve a little when you blow. However if you make the slot too narrow, you will strangle the sound when you try to whistle at low boiler pressure (of course we never struggle for boiler pressure do we?) So as ever, the slot width is a compromise, and you don't have much scope to change it in the design of brass tube whistle which I sent you. It is largely by luck that thin brass tube happens to be available with a wall thickness that suits the average model engineer's steam whistle requirements! It is also by luck that the slot width is not terribly critical; you will only notice a problem if it is grossly wrong. I'm glad that you decided not to go with driving it by air. It is a feature of the 'variableness' of steam that it allows you to get different sounds by 'quilling' the valve, to get a 'crow' for example. There is a also a characteristic slight whoop when a steam whistle starts to blow which is caused by the whistle warming up. I don't believe either is possible with air, or not to the same extent (though organists among us might correct me). In fact these characteristics are noticeably absent in the first video, where you are 'quilling' (sort of) using the airline trigger to vary the pressure. I have a reservation about your whistle servo valve on this score; it will probably reduce the fine control of the sound that you need in order to get a really satisfying and realistic whistle blast. To be successful your servo needs to open proportionately to the pressure supplied from the manual valve, without fluttering and without going straight from full closed to full open. It will be interesting to see if it will do this. Great experiment though! Since whistles are a black art to many otherwise highly skilled model engineers, perhaps we will see a range of standard plastic whistles appearing on the market? Whoo nose? -Gary Hi Gary, Thanks for that explanation. I'm starting to get the impression that I'm one of the few people that isn't overly bothered about what a whistle sounds like, so long as I've got one and it works. Maybe that's because the club locomotives I'm used to have hopeless whistles that barely work at all, and if they do they're so high and shrill. I'm not sure how the servo valve will perform, but without one, there's no way to use the semi-scale valve on the turret. It may well be that it does open proportionally, I won't know until I try it. It may be that the two distinct tones of my whistle are due to the natural frequency of the plastic tube being a harmonic of the note it's tuned for. Maybe changing the diameter and the height of the opening would change that? Anyway, the main purpose of doing all this is to move on with the chassis, so I need to finalise the position of the whistle, servo valve and piping so I can get any additional holes in the frames before painting. It doesn't really matter at this stage what the exact construction of the whistle is, I can deal with that later. Until it's all up and running, I won't know what I've got.
|
|
Gary L
Elder Statesman
Posts: 1,208
|
Post by Gary L on Oct 6, 2019 10:05:35 GMT
Hi Roger Changing the height of the opening will (other things being equal) raise the note of your whistle a little, because it would effectively shorten the bell somewhat. It would also increase the mouth area away from equality with the cross-sectional area of the bell (tube). This ‘unity mouth’ is widely (but not universally) accepted as optimal for sound production. There is a school of thought that says a slightly taller mouth than unity is more traditional and may give a better tone. So there you have it- the ‘formula’ is a starting point. In my experience it produces a whistle that works well every time, as yours does. But it might be possible to optimise it further... or not! Your plastic whistles give plenty of scope for controlled experiments. Best of luck Gary
|
|
|
Post by springcrocus on Oct 6, 2019 11:39:46 GMT
Hi Gary, Thanks for that explanation. I'm starting to get the impression that I'm one of the few people that isn't overly bothered about what a whistle sounds like, so long as I've got one and it works. Maybe that's because the club locomotives I'm used to have hopeless whistles that barely work at all, and if they do they're so high and shrill. I'm not sure how the servo valve will perform, but without one, there's no way to use the semi-scale valve on the turret. It may well be that it does open proportionally, I won't know until I try it. No, there's at least two of us. Regards, Steve
|
|
|
Post by ettingtonliam on Oct 6, 2019 13:15:03 GMT
Yep, me too. So long as it doesn't wheeze or croak, its fine for me.
|
|
JonL
Elder Statesman
WWSME (Wiltshire)
Posts: 2,976
|
Post by JonL on Oct 6, 2019 15:16:30 GMT
I didn't even know 08's had a whistle.... anyway...
That whistle servo valve is very elegant. One small thing I've taken away from hanging around the club locomotives is that the drier the steam the better the sound. A lot of the damper sounding whistles sound awful. I suspect this would be served by a combination of keeping the whistle hot and the steam pipework short? Of course I'm guessing.
|
|
stevep
Elder Statesman
Posts: 1,072
|
Post by stevep on Oct 6, 2019 18:36:21 GMT
Roger,
I had a thought (whilst mowing the grass today). Have you got a steam outlet on the whistle side of the diaphragm of your whistle valve? I would think there is the possibility that you will admit steam, which will open the larger valve feeding steam to the actual whistle, but it will remain open until the steam has leaked away from the valve side of the diaphragm.
I'm also thinking that a spring under the diaphragm may enable you to actually control the opening of the slave valve by varying how much you open the valve on the turret.
|
|
|
Post by Roger on Oct 6, 2019 19:41:42 GMT
Roger, I had a thought (whilst mowing the grass today). Have you got a steam outlet on the whistle side of the diaphragm of your whistle valve? I would think there is the possibility that you will admit steam, which will open the larger valve feeding steam to the actual whistle, but it will remain open until the steam has leaked away from the valve side of the diaphragm. I'm also thinking that a spring under the diaphragm may enable you to actually control the opening of the slave valve by varying how much you open the valve on the turret. Hi Steve, That's how it's intended to work, the valve on the turret that's feeding the diaphragm also feeds the dummy whistles. When the whistle valve on the turret is closed, the steam leaks away quickly and the diaphragm relaxes. Don't forget there's steam pressure pushing against the diaphragm, trying to close the valve. I think the spring force is tiny by comparison. My impression is that you could balance the steam pressure using the valve on the turret so that the diaphragm moves a proportional amount to the opening. That's because the amount going to the dummy whistle can be overcome by the steam coming from the whistle valve on the turret.
|
|
jma1009
Elder Statesman
Posts: 5,913
|
Post by jma1009 on Oct 6, 2019 20:08:52 GMT
Well, I must disagree!
Every decent locos ought to have a decent whistle in my book. Very few do in my experience, even Gold medal winners in the ME exhibitions.
For the public and especially the kids, they expect a decent whistle. Plus you can do quite a considerable bit of 'one upmanship' over other loco builders with locos with feeble whistles, and boy do they get annoyed!
When you do public running you ought to observe fullsize practice, and a decent whistle is part of this. Guard waves his green flag, so you whistle to acknowledge. Waiting for points to move and signals to change you sound the whistle. Etc etc...
The punters enjoy a decent whistle, and if you have a GWR loco it will of course have 2 whistles.
I personally regard having a decent whistle as important as getting the valve gear right and smokebox draughting and working injectors and the shape of the chimney and dome and safety valve cover right.
You haven't done a 'Caution' plate for inside the cab yet Roger.
Cheers, Julian
|
|
|
Post by Roger on Oct 6, 2019 21:22:02 GMT
Well, I must disagree! Every decent locos ought to have a decent whistle in my book. Very few do in my experience, even Gold medal winners in the ME exhibitions. For the public and especially the kids, they expect a decent whistle. Plus you can do quite a considerable bit of 'one upmanship' over other loco builders with locos with feeble whistles, and boy do they get annoyed! When you do public running you ought to observe fullsize practice, and a decent whistle is part of this. Guard waves his green flag, so you whistle to acknowledge. Waiting for points to move and signals to change you sound the whistle. Etc etc... The punters enjoy a decent whistle, and if you have a GWR loco it will of course have 2 whistles. I personally regard having a decent whistle as important as getting the valve gear right and smokebox draughting and working injectors and the shape of the chimney and dome and safety valve cover right. You haven't done a 'Caution' plate for inside the cab yet Roger. Cheers, Julian Hi Julian, I won't rule out having two whistles, there will be two working valves, so I'll plumb those to the dummy whistles as well as down below. I can't say I share your passion for them, it's just not on my radar as something of importance at the moment. I may return to it at a later date when I know the servo valve works. At the moment there's no point making two until I know that one works. There's a huge amount still to be done on the cab, the caution plate is already modelled, as are the sliding screens.
|
|
|
Post by Roger on Oct 6, 2019 21:28:39 GMT
Not much to show for a lot of odds and ends jobs, but I've not been idle. I've modelled the fittings for the 1.6mm copper tube for the servo inlet and made the nipple for that. I don't have the tap for that, so I've ordered that today too. The small fittings for the servo valve and brake cylinder are too small to use even a 1mm section 'O' ring, but I don't want to use fibler washers and gunk to seal them. To that end I've found some 0.5mm section 'O' rings with an ID of 2.8mm and 0.7mm section with 3.5mm ID for those two. They're on the slow boat from China, so I'll have to wait to fit those. I can machine all the parts though. Here are the 4mm nipples to match the nuts, and I've made another one of those. The nipples are done on the mill and finished on the lathe. 20191006_114412 by Timothy Froud, on Flickr I didn't have the split bush for these, so I had to make that too. 20191006_115317 by Timothy Froud, on Flickr Lot's more coming soon...
|
|
|
Post by doubletop on Oct 7, 2019 2:58:29 GMT
Roger You may be interested in something I did a while back. modeleng.proboards.com/thread/12436/whistles-againHopefully of some use to you? You'll see that the key is the slot width. The rise in pitch you are getting is overblowing, for whistles to be used at our pressures blowing by mouth it should not work that well, if at all. Don't guess the frequency, get one of the spectrum analyser apps for your phone Pete
|
|
|
Post by Roger on Oct 7, 2019 7:16:46 GMT
Roger You may be interested in something I did a while back. modeleng.proboards.com/thread/12436/whistles-againHopefully of some use to you? You'll see that the key is the slot width. The rise in pitch you are getting is overblowing, for whistles to be used at our pressures blowing by mouth it should not work that well, if at all. Don't guess the frequency, get one of the spectrum analyser apps for your phone Pete Thanks Pete, I've got one of those analysers, I'll use that.
|
|
jma1009
Elder Statesman
Posts: 5,913
|
Post by jma1009 on Oct 7, 2019 20:01:40 GMT
Hello Roger,
The 2 whistles on a GWR loco are a 6th apart, the higher whistle being something like an F note an octave above middle C, and the lower whistle being A above middle C, though my piano is about half a tone flat.
The lower note was little used (it was to get the attention of the Guard for screwing down the brake in a brakevan on unfitted freight), but many Drivers used both whistles sometimes to give a 'cuckoo' or more tunes.
As I mentioned previously, you can hear both whistles in use in the first few minutes of 'Titfield Thunderbolt'.
In both cases it should be a relatively clear loud note without too many harmonics.
I've made LOUD whistles work from 30 to 90 psi without any 'overblowing'/jumping an octave, and with no 'servo'/reducing valve being required. A search on here will provide all the information required from Pete (doubletop) to some of my own.
Cheers,
Julian
|
|
|
Post by Cro on Oct 7, 2019 20:38:54 GMT
I've made LOUD whistles work from 30 to 90 psi without any 'overblowing'/jumping an octave, and with no 'servo'/reducing valve being required. A search on here will provide all the information required from Pete (doubletop) to some of my own. But I doubt these were through a "scale" whistle valve? Where as the purpose of the servo valve allows for a small, scale valve to sit perfectly in the cab and feed the the servo valve with a small volume of steam to control a large volume to the whistle itself. I would love to see a video of your two scale whistles working as described above though Julian, possibly on the Dean was it, they sound fantastic! Please do share. Adam
|
|
|
Post by Roger on Oct 7, 2019 21:38:45 GMT
Hello Roger, The 2 whistles on a GWR loco are a 6th apart, the higher whistle being something like an F note an octave above middle C, and the lower whistle being A above middle C, though my piano is about half a tone flat. The lower note was little used (it was to get the attention of the Guard for screwing down the brake in a brakevan on unfitted freight), but many Drivers used both whistles sometimes to give a 'cuckoo' or more tunes. As I mentioned previously, you can hear both whistles in use in the first few minutes of 'Titfield Thunderbolt'. In both cases it should be a relatively clear loud note without too many harmonics. I've made LOUD whistles work from 30 to 90 psi without any 'overblowing'/jumping an octave, and with no 'servo'/reducing valve being required. A search on here will provide all the information required from Pete (doubletop) to some of my own. Cheers, Julian Hi Julian, Gary L has sent me the lengths of the whistles for both. The one I've made is the higher one G#, the lower one being D#. However, there's no way I can fit the lower one under the footplate, it's way too long. I'd have to find another way to get the lower one, or cheat and make the lower one the whistle I've already made, and make the other one even higher. Obviously they wouldn't be the right note though. Out of interest, how were these used in practice? Boats use a pattern of blasts on a single whistle. How would someone know whether they were hearing one whistle or the other? Were they always sounded singly, or used in sequence?
|
|