Dick Bagleys Steam Whistle
By R. B. Bagley
Southern California Live Steamers
The Miniature Locomotive
One of my favorite subjects is whistles and I am happy to have a request to write something about them. To me, the whistle is a very important part of a locomotive. I would never think of building a loco and leaving off the whistle. That would be like omitting the fire or one cylinder or some other vital part. All of which brings us to the "crux of the mux", or something, and you can easily see what caused me to make a whistle for one of our great living musicians, Dave Rose. It wasn't that I know so much about whistles, (note first, important, word in our title) rather than his poor locomotive was speechless! While I was giving it a general overhaul and pair of goat glands someone, namely Dick Jackson, dropped in to view the proceedings and hit my weak spot. He said that, "Of all the Live Steamers, I shouldn't be the one to let a loco go out of the shop without a tooter."
So, as I said before--fools jump in! Now Dave has one of the oddest Royal Scot locos in the world. It looks as British as ever and still eats Welsh coal from England, thanks to Les Friend, but has a voice that is definitely American. I will not list the four notes used on Dave's whistle because it is nice for him to have his own special tune. The information contained here will enable you to select something of your own choice. I never make two whistles alike; for one thing, variety is too interesting.
The chart gives you notes in the scale and their frequency along with the proper length of stopped pipe to create them. If the pipe length is doubled the same note will be derived, only one octave lower and vice-versa when the pipe is halved. An open pipe must be twice the length of a stopped pipe for the same note.
Notes used on actual locomotive whistles were taken by measurement from the locos as shown, by one of my engineer friends, Hervy Angier of the Southern Pacific. They will help you get an idea as to what is in use. Measure the length of the tubes in your favorite whistle and you can copy it. Very often a whistle one octave higher will serve for miniature work and only needs half the length. For practical reasons some of the notes can be omitted (also you can choose a minor or diminished chord), but I'd suggest the aid of a musical friend.
The diameter of a whistle tube determines the volume of sound. It does not affect the note. You can get all the necessary noise out of a tube 3/8" in diameter. The only concern here is capillary attraction. That is the property which causes water to form in a ball or raise above the surface of a container. Make the tubes large enough so that water will not be trapped in them.
The throat of a whistle is very delicate. Clear tone must be found by test. An adjustment of only a few thousandths makes all the difference between you and your neighbor. However, whistles of the type shown here have been least troublesome in my experience and I sincerely hope they will prove successful for you.
One large tube is partitioned into several chambers by vanes made of flat sheet metal. Construction is fairly simple and straight forward. It is also quite rugged as compared to chimes made with separate tubes. Partitioning need not be done with any particular accuracy except for length of the chambers. Fabrication is open work, easy to get at. The entire unit is silver soldered together and then becomes a simple lathe turning job to fit it to the tube. The problem of throating is greatly simplified being entirely lathe work.
The single tube can be to scale for an air tank on locomotives of 2-1/2" gauge or larger. Not only has the problem of hiding the whistle been eliminated but in many cases an advantage is gained because the air tank allows us more length (deep note) than might be found for a hidden whistle.
Most of my whistles are four chime because it is an easy division to make. Partitions or vanes are made of 1/16" thick sheet brass. All are made full length. A wide vane equal to width to the diameter of the tube plus enough to allow for the turning job later on, gives us two chambers. Two narrow strips form the other divisions. Scribe a center line lengthwise on the wide vane and drill 1/32" holes for 3 or 4 brass dowel pins. use this as a jig to transfer the holes to the narrow vanes. Then put the work together for silver soldering. Stops of the same material are attached in this manner also and should be included at this time. Flow the solder carefully to avoid pin holes as a leak between tubes will spoil the notes. Apply the heat evenly over the entire length but don't worry if it warps a little as no real harm will be done.
The throat disc and pipe connection are turned from round brass. Rough out approximate shape, drill the center hole in the end and cut to accurate length. Any scrap of flat brass 1/4" thick or more and large enough to plug the tube will do for the other end. Neither of these will need pinning. Just clamp the partition assembly in a vertical position in the vise and sit the ends on for soldering, be careful with alignment, of course. Clean up and drill a center hole in the end drum and you are ready for the lathe work.
Hold the throat piece in the three jaw and use a tail stock center for the other end. Rough turn over the entire length to near diameter for a press fit in the tube. Then finish turn the end next to the tail stock. Half the length may be finish turned at this setting. Then reverse the work in the lathe so that the throat is next the tail stock and complete the finish turning. Diameter of the throat disc is most important here. This governs the size of the throat opening. Tolerance for this opening is shown on the drawing and applies to all scales.
Remove from the lathe and clean up with a fine file. The slight difference between the two cuts as taken from opposite ends can be filed smooth, although in most cases it will not be enough to cause any harm. No increase in diameter is to be allowed for the press fit. The innards will fit right enough if machined to the diameter of the inside of the tube. In fact I generally turn this part one thousandth smaller, but must advise you that it may lead to the extra job of having to soft solder the two sections together in the event that you do not get a snug fit.
I doubt if you will have a press large enough to push the two parts together. My whistles are persuaded along by aid of a large rubber mallet such as is used for automobile tire work. Hold the tube in your hand. Press the vanes in by hand as far as they will go, throat end first. Then still holding the tube in your hand drive it into position with the mallet. If the fit is tight a little oil will help to lubricate. It may be necessary to use a block to hold the tube in the final stages of the struggle. A short length of pipe is good for this. Put it in the lathe and bore it out a few thousandths larger than inside tube diameter then counter bore for about 1/4" depth to outside tube diameter so that the tubing will fit in snug but not tight. Be careful to have the pipe long enough to avoid having the throat strike bottom. When all is pressed together the tube end should be 1/2" from the face of the throat disc. If the facing of this disc became distorted due to heat while soldering or otherwise blemished it may be re-faced by use of a cut-off tool while held in the lathe as before. Only the outer edge needs facing.
The outer part of the throat is a simple turning job in the lathe. Chuck a piece of round brass in the three jaw and turn the outside to dimension. Then center drill and drill to near size for the hole through the center. Finish to size with a boring tool and shape the large cavity. Use a lathe stop for accuracy in facing the bottom of the cavity and the outer rim. Here is an important part of the work. When this part of the throat is pushed in place it should fit snug on the shank and the face in line with the face on the disc. It is also necessary that the center hole and the cavity be bored at the same setting to insure concentricity as the opening for steam is very small. A lock nut on the shank holds this part tightly in place.
Now you can drill the 3/16" hole in the shank for steam passage and drill 1/8" holes crosswise to admit steam into the throat cavity.
The great moment has at last arrived. Your attempt in musical instrument manufacture is ready for a test. Put it together with the lock nut. Just finger tight on the throat. At least 50 pounds air pressure should be used for testing as the whistle is intended for high pressure use. If you do not have an air compressor visit the nearest gas station and surprise the whole world with that first ghastly toot. With air pressure applied you can turn the lock nut to adjust the throat for clear tones. Block off all but one note with your fingers and test to see that each note sounds clear. After locating the throat position measurement can be taken and a facing cut made or place a washer of correct thickness on the shank to hold the outer part of the throat in proper relation. The opening of the throat is made smaller than is ordinarily necessary for high pressure whistles for two reasons: to conserve steam and to discourage the passage of water. Water is the thing to be avoided in a steam whistle. It is undoubtedly the greatest cause for whistle failure in miniature work. Dry steam is an absolute requirement if you are to have success. Even a slight leak in the whistle valve will cause a good whistle to fail because the escaping steam will condense in the pipe and flood your tooter.
Maybe the Angels have something? But I'm having the time of my life and Dave is so happy with his new whistle that he tells me he is going to write a symphony using the four notes of the whistle as a theme.
Tidbits from Chaski
- Thanks for the post Ken, that was one article of Dick's I did not have. This is basically the background article Nelson used for the chapter on whistles in So You Want To Build A Live Steam Locomotive and is the origin of the 4 chambered whistle you often see offered by LS vendors today.
- FWIW, the SP whistle information listed in the article is a combination of folklore and printing/proofing errors.
- For those that choose to use these drawings, beware that the note charts given for chamber lengths are totally incorrect. Both Nelson's and Bagley's charts were drawn based on using air and not steam. Therefore the chamber lengths are off by as much as 4.5" on the low side (middle C) and 2" on the high side. Nelson's also shows a list of SP whistles that never existed. He says they came from Bagley. I've always been a little perplexed as to why they published these charts but it is what it is. Just a little tip from someone who's been there. The spreadsheets available on the Yahoo group can help you determine the actual lengths.
- Here is a quick edit I did to the original Bagley note table. He left out a lot of notes but at least now it's edited to reflect real world chamber lengths.
Bagley's Chime Whistle casting from Cole Power Models. Courtesy of Tim "765nkp", Chaski.org