Measuring Mouthpiece Cup Depth

[davewerden]

This one has puzzled me for a while, and I still don't have a method that could be considered "standard" except for me. The bottom of the cup is quite "curvy" as it gets close to the throat. If one used a flat-ended tool wide enough to not go into the throat, then depending on the rate of drop toward the throat, you would end up with misleading measurements.

So for today's test I used a mechanical pencil. It has a tapered tip, which will extend into the throat a little. So two mp's of similar depth would measure differently this way if one has a larger throat. BUT a larger throat can make a mp FEEL larger or deeper, so I thought maybe it's a fair way to test them. If you use your own pencil, you'd probably get different measurements. So this may be useless for obtaining any absolute standards, but might still be interesting.

I measured 4 today, all with pretty similar cup diameters and that might be thought to have similar depth and throat. I measured the distance the pencil went "in" compared to the top of the rim's curve. Here's what I got:

Wick Ultra SM4U: 1.94"
Wick Heritage 4AL: 1.85"
Wick Classic 4AL: 1.85"
Wick SM4: 1.83"

And for comparison, here's a 5th sample of a slightly larger mp, just for fun:

Wick SM3.5: 1.885"

So there you go. I think I haven't accomplished much today in the mouthpiece measurement arena, but it's something I wanted to try for a while. It's interesting to me that the Ultra swallows more of the pencil than the SM3.5, but I'm not sure what it really means.

My next idea is to somehow block the throat of each in a manner consistent with the general shape just before the throat. Then fill the cup with fluid and somehow measure the volume/weight of the fluid. The problem that might vex me there is surface tension. If I were using an eyedropper to fill the cups, how would I know when to stop? I could squeeze a few more in because of surface tension (the surface would be a little convex).

Surely there is a better way! Can one of our engineer types speak up and tell me if there is an accepted way to do this? I don't think I've seen a specification anywhere to make me think someone is currently measuring in a way that can be replicated.

[davewerden]

Oh, and to show how my mind works, I've also thought of stuffing a mp with liquid something that would harden, or using clay. Then I would remove the "stuff", round off the throat area of the stuff so the curve stays consistent (big factor for inaccuracy there), and then weighing them. Or using water displacement or some other way to compare the molded clay/whatever.

I suspect in these days of computer measurement and CAD that there is already a good way to do this. So why can't I find these measurements anywhere???

[TexEuph96]

Interesting measurements dave, which do you think is a greater factor in playing? The depth of the mouthpiece or the volume of the cup of when you fill it with water and measure the carrying capacity? It seems a piece with a larger throat feels larger when playing, making it once the largest factors.

[davewerden]

Originally posted by: TexEuph96 Interesting measurements dave, which do you think is a greater factor in playing?

I'm not sure I know the answer. Everything is about balance. Another factor that can have a huge effect is the backbore. Oh, and shape of the rim can affect your perception of cup size.

Cup depth is very important, and so is throat size. I used to rely on the 4BL (shallower version of my 4AL) when I had a tiring concert or a solo with lots of brilliant high playing. The shallower cup was coupled with the same cup diameter and throat, but it gave a smaller sound and more high-range edge - also more endurance. So certainly that one factor mattered a lot. The Heritage 4ABL I have is like the 4AL but with a tighter backbore. It is less tiring, but makes it tougher to get a big sound in the high range.

So in summary I'd have to say... What was the question again?

[carbogast]

Silly Putty?

Ice?

Try searching for "laser metrology". Is it possible that the mouthpiece manufacturers would share the dimensions with you?

- Carroll

[dkstone]

The best method to find the total volume of the entire mouthpiece is to fill it with water, then pour the water into a graduated cylinder to find how many milliliters it took (1ml = 1cc). If you are worried about the effect of surface tension, you could try sealing the large end of the mouthpiece with waterproof tape on a flat surface and pour the water in through the shank. The smaller opening in the shank would produce less of a bulge on the water's surface. Another option might be to add a surfactant to the water that will reduce the surface tension. Dish soap might be a good option for this. Of course, this does not compensate for those mouthpieces with longer shanks (like the older Schilkes) or those with rounded rims, both of which would hold more water. If you don't want the shank involved in the measurements, you could fill it with melted paraffin and let it harden before filling the cup with water.

I know that inquiring minds want to know, but might we all be better off if we spent this time practicing?

[TexEuph96]

Originally posted by: dkstone I know that inquiring minds want to know, but might we all be better off if we spent this time practicing?

Hahaha well said, I should probably be practicing audition music for next year!

[fmanola]

Dave--

A few points:

a. I'm a bit confused by the measurements you're reporting. I've got a Wick Classic 4AL here, and it looks to me that the cup depth is a little over 1"; certainly no way is it anything like 1.8" (a Bach 18 tuba mouthpiece doesn't have that cup depth). Can you describe how you're doing this again?

b. Here's what I tried: I stood the mouthpiece vertically on the end of the shank (IOW, cup up) on my desk. I took an old-fashioned yellow pencil (a Dixon Ticonderoga, if we're going to define a standard!) and stuck it vertically down the mouthpiece until the point rested on the desk and the eraser stuck out of the cup. The pencil is just wide enough so it will slip through, but is thick enough so it stays "pretty" vertical (obviously, if it slants at all, it will affect the measurement, but you could make a measuring stick that would go into a flat-bottomed holder to ensure a vertical stick). I then took another pencil and made a mark on the vertical pencil where I thought the bottom of the cup was, and another mark where the rim level was, and measured between those marks. I get roughly 1.1" for the Wick Classic 4AL. With some "tooling", I think this approach could be made a lot more precise, assuming we could determine exactly what we're measuring (see point d).

b. I don't quite understand how measuring the volume of the cup really helps in this situation, since in order to determine a depth from any volume figure, you have to account for a rather complex solid geometry, and you've already pointed out the "curvyness" at the bottom of the cup. I think just trying to measure what you want to measure, rather than something else, is the best way to go.

c. It seems to me the first step in determining a standard measurement technique for cup depth would be to have some standard for determining where the deepest part of the cup is, since if what you're measuring doesn't have a standard, you don't have anything to base a standard measurement on.

--Frank

[davewerden]

Frank,

My technique is nothing like a "standard" or even an absolute measurement. It's strictly relative and depends completely on my particular mechanical pencil. This particular one has a long thin taper on the pointy end, which is why it went so far into the throat. I'll check my caliper again when I have a chance. It's a dial caliper, so maybe I missed an increment there somewhere.

However, part of my point was to use the pencil's point. So I did not care about the overall measurement - only the difference between two measurements and what different factors it demonstrated.

If I had an exact-size profile drawing of the inside, it would still be hard to measure depth. One would still need to try to "finish off" the bottom of the cup as it would exist without the hole. In the old days I might have used a French curve and eyeballed the proper curve to do this.

But suppose a mostly cup-shaped mp cup takes a steep drop into the throat area (becomes V-shaped at the bottom). How would one figure where the bottom of the cup is?

I like the proposed idea of filling the mp from the shank with liquid. One would have to have an idea of the shortest overall length among all available mouthpieces (I think). If a mouthpiece is longer than that, then I would only fill it to the same "height" as in the shortest mp. Then measuring the volume of liquid might really mean something, because it would take more factors into account, including backbore.

But in my heart I know that there is not way to come up with a number to tell you what the sound and tiring/endurance factor will be, any more than comparing the numbers between two euphoniums will tell you which one sounds better/worse/brighter/darker.

[carbogast]

I'm kind of stuck on the idea of taking a cast of the inside of the mouthpiece. This would be useful for a variety of reasons. Not only can you measure it's diameter height, volume, and curvature, but you have a permanent visible object to compare to other pieces.

There is a foam sealant used to seal small exterior cracks and small holes in houses. It can be gotten at the hardware store. I wonder if that would work? I imagine that plaster of paris can be gotten at the hardware store as well. That might be the ideal material.

Are there any dentists out there? Dentists must be very expert at casting.