Drone Reeds

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Re: Drone Reeds

Postby pipemakermike » Thu Sep 20, 2012 3:34 pm

Here is a first pass at gathering data. I have processed 2 apparently identical reeds but clearly there are some differences! The column at the left is both inches WG and pitch in cents. The row along the middle is the sample number. I measured the pitch at each half inch watergauge from 17" which is the top limit for my rig (set by a relief valve) down until the reed stopped sounding. For reed 022 (the red line) this was at around 13"WG and for reed 025 (the yellow line) this was at 10"WG.
I didn't select a special reed, just a couple out of the box. I would guess that it would be possible to optimise the reeds for a lower pressure but it does look as though one reed (022) is happiest at 15" to 16"WG and one (025) is happiest at 13" to 15"WG.
One interesting thing to note is that one of the reeds (025) got slightly sharper as the pressure dropped and the other one got flatter

reed pitch chart 022-025.jpg
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Re: Drone Reeds

Postby andymay » Fri Sep 21, 2012 12:03 pm

Hi Mike
rt
This is really interesting, thanks!!

Would it be possible to produce a simpler chart of your data with pressure on one axis and pitch on the other? Just might be easier to read for numpties like me!!!

Another thought - is it also possible using your rig to test the reed's response in the drone? It would be interesting to see what difference that would make to stability.

Cheers
A
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Re: Drone Reeds

Postby pipemakermike » Fri Sep 21, 2012 12:52 pm

Ask and it shall be given. I need to do more samples to get a real grip of what is good and what is bad.
I am testing the reed in a drone. and powering it from my test rig to give me control. I use the sliding part to set the desired pitch at the 17.5"WG playing pressure then lowering the pressure in 1/2"WG increments and recording the amount in cents that the note moves from the original setting.
EDIT:
I have been thinking that it might be a more useful measure if I set the drone in tune at a specific playing pressure say 15" WG then record the pitch changes for a couple of inches WG above and below that pressure

reed pitch chart 022-025-2.jpg
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Re: Drone Reeds

Postby Richard Evans » Sat Sep 22, 2012 8:22 am

A quick check of the low g reed currently in my own set shows a drop of about 10 cents for a 3" reduction in pressure, very similar to the blue line on the graph. That's not necessarily significant in any way, a sample of one and I'm always swapping them about in my own sets. If/when time allows, I'll do some more detailed tests on a range of reeds.

So, the question is, if Mike's reeds are apparently identical, why is one much more stable than the other?

Cheers
Richard
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Re: Drone Reeds

Postby pipemakermike » Sat Sep 22, 2012 9:38 am

I think that the difference is probably because the blue one is set at a higher pressure - it stops sounding at between 14 & 13.5" WG. The actual setting of the reed tongue is quite sensitive to the gap under the end and I would like to do some more accurate measurements of this. I plan to tweak the blue reed until is stops sounding at the same pressure as the orange line reed i.e. <10"WG and take a second set of measurements. The main reason for doing all of this is to see if I can identify the design elements that are driving both the good and the bad features.
I will need to make some changes to my test rig as I also want to discover the maximum pressure that the reed will play at.
I am currently making a new batch of 10 G drone reeds and making a special effort to make them identical and I will report later.
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Re: Drone Reeds

Postby andymay » Sat Sep 22, 2012 9:56 am

Thanks Mike, that's great!

So just to be sure i'm reading it properly -

Your orange reed looks to be within 2 cents between 12 and 17 1/2 inches water pressure? Impressive. And basically no change between 13.5 and 15.5 which should encompass most people's playing pressure (not all, but)

Am i right in thinking then that the blue reed at present isn't that great? - It doesn't appear to have the flat area of stability that the orange one does?

Or am i still reading the graph wrong?

Fascinating to see these results written down in this way i think. I'd be curious to try some different kinds of reed on your rig some day.

Cheers

A
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Re: Drone Reeds

Postby pipemakermike » Sat Sep 22, 2012 10:55 am

Hi Andy

You are reading the graph right. I think that the sweet spot of the blue reed is set at too high a pressure. I will be messing with one this later. I am still in the "when in doubt, do something" area of the testing and data gathering. I am hoping that I will be able to home in on a set of good parameters and this is helped as much by the ones that dont conform as by the ones that do. If I can just discover why these two reed are different I will have learnt something.
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Re: Drone Reeds

Postby pipemakermike » Sat Sep 22, 2012 9:33 pm

I have now tweaked the 022 reed to lower its playing pressure sightly. I have also revisited the numbers setting the starting point at 15"WG and getting numbers for above and below this pressure. One difficulty has been that, because the pitch change is so small it is quite hard to get precise numbers especially as the first decimal place is changing very rapidly. I have now measured 4 reeds and it does look as though the pitch stability is very good.
Here are the latest measurements:-
Attachments
reed performance 020 to 026.jpg
reed performance 020 to 026.jpg (30.64 KiB) Viewed 2336 times
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Re: Drone Reeds

Postby pipemakermike » Sun Sep 23, 2012 10:05 pm

I have now gathered data on a few more reeds and here is the collected data. I have found a number of features that make getting accurate data a little more difficult and time consuming. The general pitch of the reed changes slowly when it is first started and it takes some 5 to 10 mins before it is fully stable. The change is small but so are the pitch changes due to pressure changes. One of the reeds (021) is different to the rest and that reed has a narrower carbon blade (about 3.3 wide) compared to the 4mm wide blades of all the others. All of the reeds played with the drone length set within a couple of mm of each other. It is probably worth mentioning that these reeds are concert G reeds designed specificaly for use in the School Pipes. The reeds will also fit traditional sets but I don't have much experience of them in traditional sets except that I have a G and a small d carbon reed in a Nigel Barlow standard concert F set and I am very happy with both the sound and the stability of them. The sound seems to be the closest to a traditional all cane reed but without the tricky making and setting that is a feature of the traditional item.
Attachments
carbpn G reed stability data.jpg
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Re: Drone Reeds

Postby pipemakermike » Mon Sep 24, 2012 10:51 am

Another thing that I have found is that the bore of the outlet end of the reed seems to be important. I have made 9 reeds using a different tube that was 1/8" internal diameter and found that, using the same bend position and blade positioning, the pitch was nearly a semitone sharp (G#). I also think that this reed was more pressure sensitive than any of the previous tested reeds. I then bushed the tube using the 1/8" o/d pipe that I used as the outlet for the reeds use in the tests above and the pitch returned to what I would have expected (G). So it seems possible that the bore of the outlet tube is an influence on the performance of the reed. I will need to do some more testing and I will report later.
edit: testing a second identical reed was also sharp but sleeving the bore didn't change the pitch.
Here is a picture of the latest design of the G drone reed (without the bore reduction) The square section is 4mm square and 30mm long. The bend is 18mm from the end and the end is bent down 0.5mm. The outlet tube is 3.2mm inside diameter and 15mm long.

The outlet tube on the 8 fully tested reeds was Ø3.2 o/d x Ø2.5 i/d and this is the size that I used to bush the bigger tube.

The tophat bush is only used for fitting to the School Pipes.

Image
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