 The Clarinet BBoard
|
Author: KSCop
Date: 2017-01-26 08:21
I've been tearing down several clarinets tonight in preparation for overhauls. The pads were all in such bad shape I couldn't get measurements, so I went to measure the cups instead.
I recall learning at some point that a good way to calculate the pad size, at least for stepped felt pads, was to take the outside cup measurement, subtract .3mm, and then round the result down to the nearest .5mm.
I usually have a stock of most sizes and could use those to verify, but I'm running a bit low at the moment.
So, that all said, I created a quick and dirty spreadsheet that will calculate the pad size based on the actual pad cup measurement. No more math for me!
The formula seems to make sense on the few I've been able to test.
Am I on track or is my formula off?
|
|
Reply To Message
|
|
Author: Tony F
Date: 2017-01-26 09:20
Your method for stepped pads is the one that I use. Your spreadsheet sounds useful.
Tony F.
|
|
Reply To Message
|
|
Author: KSCop
Date: 2017-01-26 16:56
Can't post the spreadsheet but PM if interested.
I'm working on an app..
Post Edited (2017-01-26 16:58)
|
|
Reply To Message
|
|
Author: Chris P
Date: 2017-01-26 17:41
On most clarinets the inside diameter of the pad cup is usually around 1mm narrower than the outside diameter as the side walls are usually around 0.5mm thick.
(On saxes there's usually around a 2mm difference as most pad cups are stamped from 1mm thick sheet brass)
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
|
|
Reply To Message
|
|
Author: KSCop
Date: 2017-01-27 06:34
I've seen two methods of measuring to get the pad size, short of measuring the pad itself (which has it's own issues).
One says measure the outside diameter, subtract .3 and round that down to nearest .05.
Another says measure the inside diameter, add 1.5mm and round that.
I think the second method is off..
Using a measure pad cup. I had 10.27 outside and 8.91 inside, giving a wall thickness of .68 which is pretty average.
Based on the first formula, it would call for a pad size of 9.5
Using the second formula, it would yield a pad size of 10
Now, if I took the first pad size and subtracted 1.5, that would indicate an inside cup diameter of 8 instead of the 8.91 (or 8.5 if rounded down).
So clearly, using the two methods yields different results.
From my testing, the closer calculation is the first formula for pad size.
To 'calc' the inside diameter, subtract 1.5 from the outside diameter and round that down.
In that case, it would show a 9.5 stepped pad and a 8.5 for a pad that sits entirely in the cup. Now that seems to match what I'm finding.
More testing is in order, and I'm sure I'm making more of this than need be. Short of a stock of pads to test I think this will show the best results.
All of that being said, this entire calculation assumes to always round down to the nearest .5 mm. My current beta version of the app has added fields for rounding UP.
Testing to continue..
Post Edited (2017-01-27 08:12)
|
|
Reply To Message
|
|
Author: Johan H Nilsson
Date: 2017-01-31 13:01
And when all the calculation is done and the order has been sent you will find that the delivered pads are oversized by 0.15 mm...
Mostly applies to leather pads which seem to be regular pads with skin added.
|
|
Reply To Message
|
|
Author: Matt74
Date: 2017-02-01 03:38
There really isn't any way to calculate pad sizes. I wish there were. The main problem is that the dimensions they give you aren't the ones you want, and all the manufacturers are different. They tell you the outside diameter, but you need the cardboard diameter (hence, the desire to calculate). Then they tell you the overal thickness, but you need the felt thickness. Some manufacturers give a rule of thumb, like subtract .5mm, but it's not always the same rule. Then the step that fits over the cup edge is more or less sharp or curved, which means that you can use a smaller pad when it's curved, and a larger one when it's sharp. Then, especially if it's curved, depending on how thick in needs to be you can use a larger or smaller pad to adjust thickness. There is also preference. If everything is level you can put a larger pad in so that the outer edges come out to the edges of the cup, which looks neat, or have them somewhat inside the edges of the cup, which allows more adjustment. Also, the edges of the pad cups are not necessarily the same thickness. Sorry if that's pedantic, I have a lot of angst about it.
However, I would suggest the following for a spreadsheet:
1. Take thickness into account. Some thicker pads won't fit some places at all. Where they do, for the same cup, you may need a smaller diameter when using thicker pads, and a larger diameter for thinner. (I am told some guys use all thick woven pads on student horns, but I don't know how this is possible - unless they are using smaller diameter pads and/or they're not in straight, or they squish a lot, or something...)
2. I found that the difficult ones are F# ring key, A/D ring key, and 3 ring key, because you have to have the right size for the mechanism to work. The large ones are difficult to seal, but there is more "fudge" room with size.
3. The smaller the key cup, the easier it is to find the right size, because only one or two sizes "fit", and they are easy to level. The larger the key cup the more options you have for sizes. This makes sense because .5 mm (the difference in sizes) is a larger fraction of 9.5mm, than of 16.5mm. For a small one you might be able to use a 9.5 or a 10, and one will definitely fit better than the other. For a large one with an inside diameter of 16mm, you might be able to easily use a 16.5, 17, or 17.5mm.
4. For some keys, you can use a thicker pad to make it "look" right. The LH G#/C# can take a thick pad because venting isn't an issue and it makes the key cup sit tangent to the body.
5. I think pad cups are generally oversized, round down to the nearest 0.5mm. A cup that is nominally 11.5mm will probably measure 11.75, or something like that. It might be easiest to just use an engineer's rule. The cup won't measure exactly the same all the way around, but the 11.75mm shouldn't be smaller than 11.5 anywhere, unless it's bent.
- Matthew Simington
Post Edited (2017-02-01 03:54)
|
|
Reply To Message
|
|
The Clarinet Pages
|
 |
.jpg){kind=small}
.jpg){kind=small}
.jpg){kind=small}
.jpg){kind=small}
.jpg){kind=small}
.jpg){kind=small}
