what's inside a piston?

bububassboner · Post by **bububassboner** » Thu Jul 12, 2007 9:04 pm

What is inside a piston valve? I was wondering because I noticed some pistons have "bumps" on the inside of the ports. Like they needed room for something inside the valve. So what is inside a piston valve?

P.S. Is the hole on the bottum of the piston important? Just wondering.

Steve Inman · Post by **Steve Inman** » Thu Jul 12, 2007 11:20 pm

("12" + "13" ) / 2 = 12.5!

"Brilliant!"

(Thanks for the informative post.)

MartyNeilan · Post by **MartyNeilan** » Fri Jul 13, 2007 5:12 pm

what's inside a piston?

A ton of ...

iiipopes · Post by **iiipopes** » Fri Jul 13, 2007 11:37 pm

Hate to burst bubbles, but Denis has retired from instrument making and is pursuing other ventures. It's not just that his valves had no "bumps," that was only the detail. He made his valves of a large enough diameter that he could bore them "off center" or "off axis," and retain both a better flow as well as a shorter stroke. The elimination of the bumps was a result of, not necessarily a cause for, his design.

The Big Ben · Post by **The Big Ben** » Sat Jul 14, 2007 12:40 am

Interesting topic in which I have not given much thought...

How is a piston valve made? Is it a casting which is finish machined? I know that the ones I've seen are hollow so how does that fit into the manufacture of a piston valve?

Jeff "Push the second valve down, the music goes 'round and around" Benedict

andrew the tuba player · Sat Jul 14, 2007 2:16 am

please correct me if I'm wrong, but my understanding is that a piston valve is basically a hollow cylinder with small tubes going through the middle in order to direct the airstream from one piece of tubeing to the next. then, you get different notes with different lengths of tubeing....heres another question for an expert...what is 'hand lapping'? i know that its a stye of lapping the metal so, i guess the better question would be what is the process of lapping a piston valve?

The Big Ben · Post by **The Big Ben** » Sat Jul 14, 2007 2:03 pm

andrew the tuba player wrote:please correct me if I'm wrong, but my understanding is that a piston valve is basically a hollow cylinder with small tubes going through the middle in order to direct the airstream from one piece of tubeing to the next. then, you get different notes with different lengths of tubeing....heres another question for an expert...what is 'hand lapping'? i know that its a stye of lapping the metal so, i guess the better question would be what is the process of lapping a piston valve?

Check out Dan Oberloh's site: http://www.oberloh.com

Herr Oberloh has put together sets of pictures covering many aspects of brass (and woodwind) repair and renovation.

One of the presentations answers your questions.

Kevin Hendrick · Post by **Kevin Hendrick** » Sat Jul 14, 2007 2:13 pm

MartyNeilan wrote:
what's inside a piston?
A ton of ...

... vinegar? (that would explain the old phrase "full of piston vinegar"

)

windshieldbug · Post by **windshieldbug** » Sat Jul 14, 2007 10:12 pm

iiipopes · Post by **iiipopes** » Sun Jul 15, 2007 9:10 am

I like to hear about experiments like yours. No, I'm not being sarcastic. I love to tinker. I've learned more from my foul-ups than I ever did from the very few that I got "right."

For example, I love to tinker with electric guitars and have ever since I got curious about what was under the hood of my first Sears electric I got in the spring of 1974. I've bought and sold dozens since then, always trying to make them "better."

I even bought a cheap Strat-oid for the sole purpose of carving on it and trying all sorts of pickups, wiring, bridges, tailpieces, other hardware, etc.

I still do. I wanted a brighter sound out of my bridge humbucker so I took it apart to unwind one of the coils. No big deal, I thought, since I had done it to other pickups, even real Strat pickups and even, yes, Rickenbacker high-gain pickups with their 44 gauge wire. Well, the wire was brittle, I looked wrong, and I pulled the wrong wire. $75 later I had a rewound coil at the lower spec.

I don't do fretting, as I don't have the tools. I don't do refinishing, because I don't have the tools or a proper booth.

But the upshot of all this is I have a custom fanned fret guitar with custom electronics that fits me like a Saville Row tailored suit I play every week. I haven't been "guitar shopping" in years, and it cured me of GAS in a big way. Better yet, all my friends have me tweak their guitars so they can get the best out of their particular setup.

My custom bass the same way you can hear on the Welk special "Precious Memories."

Cost over time? Too much. Cost compared to having someone else tinker with them, or try to explain it for them to do, and usually get it wrong because it's not conventional -- a fraction. Experience and knowledge gained that couldn't be had this side of an apprenticeship, not available in these parts -- priceless.

So, hang in there with your experiments. It's like the quote from 2001: A Space Odessey -- "Where a million failures wouldn't matter, one success could change the course of destiny."

Next time -- try having your pistons plated with boron nitride and see how it goes. I've been considering that myself. There's a thread around here where I was thoroughly thrashed about on that one.

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what's inside a piston?

what's inside a piston?

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