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Would this be possible on larger rotor tubas?

The photo shows a Paxman Studenti model compensating double horn. I never saw this solution before.

The wear possibly would be a worse factor on the larger tuba rotors, but then replacements would be fairly easy to make and mount for people with the right type of hands.

I checked with the current version at Paxman’s site:

So I would assume that the nylon rods represent a conversion.

Disclaimer: I will take no responsibility for damages inflicted by home-grown handymen.

Klaus Smedegaard Bjerre

You are asking why plastic materials are not used in more musical instruments. That's a great question.

The Nylon/Delrin rods pictured appear to functionally capable. They could even be plated to resemble silver, although they would not be traditional materials; hence not so acceptable to the public. See the link for a variety of shapes and applications.
http://www.professionalplastics.com/cgi ... /sesent/00

For mass production, even the expense of specialized molds could be justified for making one-piece brackets and levers. However, small production lots would not justify the expense of molds. The alternative to expensive molds would be the present practice of using common-size and shape brass rods and bars. Those common brass materials are fairly easy to order and fabricate.

I would imagine that musicians and musical groups are biased against the appearance of plastic. They would rather have brass or copper that could be plated with a precious metal and polished to a high jeweler's luster.

There's an aversion, especially in expensive consumer items, for artificial materials. For example, plastic shoes--not leather; plastic furniture--not natural wood or fibers.

Dean E wrote:There's an aversion, especially in expensive consumer items, for artificial materials. For example, plastic shoes--not leather; plastic furniture--not natural wood or fibers.

Often, it's for a very good reason. Leather "breathes" better than plastic. The plasticisers in PVC evaporate over time and the structure becomes brittle. That lawn chair you're sittlng in suddenly gives way without any indication (I usually can tell if a wooden chair is going to hold my 240 lbs. without collapsing).

Wool as a fiber is very hard to beat when it comes to durability. A wool rug, if cared for, will last for generations. Not so for one made from milk jugs.

Where a synthetic material is clearly better in all respects than a natural one, however, I say "use it".

In the case of the linkages, it's not the "artificial" material used--one could use lacquered spruce with the same dimensions for the same purpose and it'd look just as "clunky", even though it was "natural".

My original notion despite my disclaimer was directed towards those doing competent renovations on let’s say an older F-tuba, which they could not afford to buy new or to have professionally rebuilt.

RD very competently demonstrated his conversion process, which I found fine. Only I found some of the components being too large.

I do not like the looks of the white "plastic" on that horn. It would have been less offensive, had it been black. King has used black lever arms on some bass trombones.

In my remaining eyesight these white horn levers are not specially moulded for this purpose. They more look like a long standard stick, which has been cut up to the needed lengths. I cannot tell its original purpose. And I don’t know where to get it, but I know where to ask.

The type of tools involved in the process very likely are some, which I have been able to handle and maybe still own. I have not figured out the bearings within the plastic (if there are any at all), but I am convinced about getting a good answer out of this board.

I know about the evaporation of plastic. That is why I do not enter a car, if at all avoidable. I know about the brittleness of older plastic. I have heard the snapping sound of a full plastic tea mug, when it suddenly disintegrates.

But then I also have heard the even harder snapping sound, when one of the hardest steel components in the brass industry snaps: the ball of the ball-and-socket linkages known from B&S among others. I have had no problems with mine, and I think the two cases in question being caused by the linkages taking several blows from kissing chairs and the like.

Klaus Smedegaard Bjerre

imperialbari wrote:...RD very competently demonstrated his conversion process, which I found fine. Only I found some of the components being too large...

...But then I also have heard the even harder snapping sound, when one of the hardest steel components in the brass industry snaps: the ball of the ball-and-socket linkages known from B&S among others....

There are smaller ball joints, including some all-metal joints for those willing and able to fabricate with more precision. They don't work any better, but I'm sure they look better when viewed up close. From any reasonable distance, I doubt the ball ends make much difference in the appearance of the instrument.

I suspect the plastic rods pictured here just ride on screw-in shafts similar to the shafts on S-linkages.

I have seen a number of the factory ball-joint linkages up close, and to be honest I haven't been too impressed by them. The original outer ball on my B&S was quite small, and if the ball is hard enough for a ball joint it's probably too brittle to make a tough shaft for that ball. That's why I prefer the Du-Bro links--the balls are brass instead of steel and they are held in place with through bolts. Those small bolts are bigger and tougher than the base of one-piece balls, and even if you broke one by impact it would be easy to repair.

The brittleness of plastic also comes into play with some of the ball-joint designs. My Miraphone had early factory white plastic links that were brittle and cracked when it came to me at the modest age of 13 or 14 years old. I have more years on the Du-Bro replacements, which show no sign of brittleness at all.

The ball-joint linkages on my Sanders-labelled Cerveny that I bought in 1984 were also assembled from model airplane parts. They were smaller and lighter, using white plastic snap-together balls and 2-56 rod connecting them, with a cheap aluminum tube covering the rod. The Du-Bro links and 4-40 connecting rod were a big step up for that instrument.

And the ball link on the VMI-made Vespro that I owned for a while were steel against steel. That requires grease to operate smoothly. I could never make them fast without them being rattly, and I replaced them.

The manufacturers may know lots about smooth brass and acoustics, but they don't always do their engineering of small parts well.

Rick "who thinks the plastic rods are ugly and not much easier to install than better-looking alternatives" Denney

Aesthetics aside, although important, the thing that concerns me is the wear factor of the screws going directly through the material without being bushed. This might not be an issue, but anywhere there is movement, there is wear, and I would like to see at least some teflon impregnation at the bearing surfaces, if not the entire rod impregnated with teflon to offset any increased surface friction inherent in plastic. To go any further, say with bronze sleeves as is a standard, would defeat the purpose. At this small a scale, I don't know if there is actually any weight savings between the plastic and tubular brass or other lightweight metal linkage. But I appreciate anyone trying a different approach to see if it is better, viable, less expensive without sacrificing quality, etc. I like it.