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Tech/maintenance My new "DIY" pads...

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David, came to the thread late, and I've read most of the posts, but it occurred to me, with your new pad arrangement, have you done a "pop" test, running down the sax closing the pads in turn down the instrument? How does that sound compared to a standard instrument?
Having read the comments about level tone holes, I would have thought the main advantage of your idea is that with level tone holes, you have a very level pad, so the seating IS very easy to get right. I suggest your system does need level tone holes to work, because the pads are by definition very flat and stay that way.
I suspect that if you can get the combination of materials at the pad interface right, with just the right amount of compliance and bounce, you can probably make the dynamic feel as the pad seats very similar to the traditional feel. That might mean it can't be very thin though, because the pad will need some distance to compress slightly as it seats.
I think you still need the pad cups to protect the position of the pad. It might be self-leveling, but that's no good if it is not level the first time it is lowered and has to play a note, i.e. if a pad gets bumped while playing it probably won't be acceptable?
Very interesting project though! Please keep us updated.
 
Yes, the pop test is a useful part of testing, as with any new set up. I have an identical alto with traditional pads to compare pop and feel with the prototype.

Sealing materials so far work well in the 0.7-1.2mm range. A traditional pad can accpmodate an uneven tone hole to some degree as can a medium compression set material such as some neoprene foams. I'd have thought 0.5mm unevenness would be an absolute maximum in either case. Flat tone holes are of course ideal.

The magnets take up 2mm of the available depth in a key cup which leaves 2-2.5mm for backing disc, seal, and adjustment room.

Waiting on more discs with clinched centre threaded inserts in order to reduce overall pad thickness. Then more material testing for seals.
 
This type of "pop test" is new to me. Does it mean to close each pad firmly one at a time when you go down the stack keys and expect a "popping" sound with each? If so I'm going to have to try that. My system has always been to check the air tightness of the entire saxophone fingering low Bb and then "popping" the F or D key and listening for a "ring" in the sound.

https://soundcloud.com/jbtsax%2Ffingering-low-bb-popping-f-key
View: https://soundcloud.com/jbtsax/fingering-low-bb-popping-f-key?si=5572d9822c354872a0a38365a9f9c8de&utm_source=clipboard&utm_medium=text&utm_campaign=social_sharing
 
Update...

Testing different synthetic sealing materials meant getting duplicate sets of stainless backing discs from a local laser cutting firm.

I also experimented with the pad height adjustment and found the best way to adjust height is with M3 shim washers in 0.1, 0.2, and 0.3mm thicknesses. A wavy lock washer stops the adjusted height from moving.

I did the first set of seals by punching out seal discs of the correct diameter using two sets of various sized hole punches. Spray adhesive on the discs secures the seals. A tiny PEM nut holds a standard Music Medic domed reso to each seal and onto the M3 screw behind the disc.

Regulating the first set involved trying to keep the pad cup parallel with each tone hole as a reference from the 2nd identical (traditionally padded) Jupiter alto, then swapping out shims until all keys interacted perfectly.

A bit on my findings/theory regarding the importance of parallel pads to tone holes:
If the key cup pivot point is too high the pad (in my system), although self-levelled when it meets the tone hole, will be swept across the rim from the opposite side, i.e. dragged slightly toward the pivot point as it closes. This dragging adds minor unnecessary friction.
If the key cup pivot point is too low the pad will be pushed slightly away from the pivot point as it closes. Again, undesirable.
With traditional pads having a deep seat tone hole rim impression this sideways movement could also cause sticking as the pad has to defeat the steep sides of the seat whilst moving sideways slightly, friction again.
Whilst almost impossible to keep every cup to rim relationship parallel, it's something I'm keeping in mind when adjusting and regulating pads.

Still have an issue with G sounding a little quiet, sharp, and wispy - see my other thread of today's date.

The first seal is a smooth faced, low compression set, "space age" foam sheet. I have it in various thicknesses and softness. This one was fairly soft and 0.8mm thin.

I'm going to try a more spongey looking neoprene sheet next, as a comparison.

More soon, but not that soon...

Oh, and I may pop into TruSeal to say helli when I'm over there next month.
 
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Hmmm...

What ARE they made of?...

s-l1600-7.webp


Screenshot 2022-05-16 at 12.10.45.webp



If we assume the ARE "rubber", that itself won't make them "easy to replace and use without damaging the surface of the saxophone."

That they are "not easy to deform" doesn't bring a lot of hope to their claim that...

Screenshot 2022-05-16 at 12.14.29.webp


I've asked them:

"Hi,
What type of rubber are they made from, e.g. Neoprene; EDPM; Nitrile; Silicone?
Is the rubber solid, or a foam sheet? If foam is it open cell or closed cell?
How do these install, is the pad still glued into the key cup?
Many thanks,
David"

It may be interesting to buy a set to see what "the Chinese" have come up with to replace leather. My rubber partner 🙂rolleyes🙂 asked a Chinese manufacturer to replicate a branded foam sheet they stock. The Chinese version was as good if not better than the original. But when asked to tweak the spec of the foam slightly to give different properties the manufacturer didn't have a clue. Very good at copying, but not creating was his verdict.

From the outset I always thought that if my invention was any good it would get copied by China, and there's nothing I could do about that. A Worldwide Patent doesn't protect you, it just gives you the ability to spend ten or hundreds of thousands on law suits against people the other side of the world who would likely side step production into a different legal entity.

These pads look to install with glue. That won't make them easy to level whereas mine self-level and height adjust. My mechanism is now in its final version and it's "only" the sealing material I'm still experimenting with. Maybe the Chinese have gone through a hundred different synthetics and got it spot on with this one. I haven't perfected this yet, although I feel I'm close.
 
DavidUK said:
A bit on my findings/theory regarding the importance of parallel pads to tone holes:
If the key cup pivot point is too high the pad (in my system), although self-levelled when it meets the tone hole, will be swept across the rim from the opposite side, i.e. dragged slightly toward the pivot point as it closes. This dragging adds minor unnecessary friction.
If the key cup pivot point is too low the pad will be pushed slightly away from the pivot point as it closes. Again, undesirable.
Read more…
I'm not sure I completely understand the point you are trying to make, but it reminded me of a graphic I made a while back comparing the difference of the key rotation with different hinge tube heights.


Measuring key height different key axes..webp
 
@jbtsax - the point was... that it would be easy to assume that just because my pads self-level it doesn't matter whether their surface is inline with the key's pivot point. They could be higher or lower but still seal as they will adjust to the tone hole level on closing.

But it does matter as it reduces friction from the pad being dragged over the TH as it opens/closes if the pivot point is out of line. It's a very small amount of drag, but best avoided if possible.
To get all pads perfectly aligned with their pivots, AND with each other, would be just about impossible on an off the shelf horn.
 
this is great david, i'd really like to buy some. it seems similar to the concept of the 'toptone' alto i have, made in holland i believe, which uses little foam discs or cylinders behind flat synthetic pads, also very thin. these are very light and the action is startlingly light and fast. however your theory is superior in using magnetic linkages because the foamy bits can break down, are difficult to repair and to adjust for height. there are other self-levelling pad systems in the world. i'm sorry but how do you fit the socket (or whatever it it) in the key-cup to hold the magnet? this would be the bit that requires the greatest accuracy by the home repairer.....
 
The 2mm thick nickel plated neodymium magnet, countersunk one side, has it's flat side glued directly into the clean and lightly abraded key cup centre. I have established the correct loctite and 3M glues for brass/nickel/silver (cup) to nickel (magnet) but for the prototype used contact adhesive, wet, to position the magnet then superglue to keep it there. I got a few wrongly positioned and had a hell of a job removing them. Now I position a bare backing disc which just fits inside the key cup and mark it's centre through the disc's 3mm centre hole with a thin gel pen. The magnet has a 3mm hole too so I can line it up with the mark.

I spec a pad 1-2mm smaller diameter than the cup unless the outgoing pad shows a tone hole rim impression right on its edge. The new pad has to be able to tip so as to self level so there needs to be at least 0.5mm clearance all round it.

You might have a cup that's 40mm diameter inside and its tone hole measures only 35mm. So you'd perhaps think a 37mm pad would do. But the key cup will be off centre to the tone hole 90% of the time and a 37mm pad could still sit right on the edge of the tone hole.

I'm a little conscious of dirt accumulating behind the pad, through this gap, but of course it takes around 5 minutes to remove all the pads to be able to clean them periodically. Whilst out you could replace any worn/damaged ones. A 2 minute job.
I'm trying to choose a pad material which is extremely hard wearing. Most synthetics have this formulation.

There are a couple of keys which need a rod screw undone to remove but on the Jupiter alto all the main stack and bell keys come out with no disassembly so thankfully there's little to stop the knowledgeable home user replacing pads. They may well want a trained tech to do the first installation, including checking tone holes are level (as they would anyhow for an overhaul). I would offer NAMIR techs free training in my system, it's not difficult. Pad replacement is likely to remain in the tech's domain, as most owners want a proper set-up, but would be so much quicker. No glue or shellac required. The magnet is already there. The home replacer would need to check the individual pad's adjustment shims remain on the mechanism's bolt as they dismantle and swap out the pad (comprising the backing disc and sealing material attached), then just replace the tiny nut in the centre of the resonator. There may be some re-regulation necessary but I'm trying to avoid this by using a pad material with low compression set - in other words it doesn't form a permanent depression over the tone hole rim. 50/50 on whether this will be successful.

So... it's really just down to finalising the perfect synthetic pad material. I'm on it...
 
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Similar threads... or are they? Maybe not but they could be worth reading anyway 😀

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