TubaForum.net

I want to check my piston valve height alignment, but I don’t have a Borescope or inspection mirror that fits inside of the neighbor valve casing. There are several valve positions that I cannot see when pulling the slides.

Is there a different way to check piston height, or do I need a mirror or scope?

The old-school way is with a sliding gauge with a hook (to catch the top of an open-instrument casing port) and an extended plank on the sliding part (which is rested on the top of the casing, locked in place, and measured (or laid onto the piston)...

...With the old-school method, there's also some arithmetic do with with calipers:
- measuring the width of the top male threads on the casing, measuring the depth on the inside of the top cap, doing a subtraction problem, and adding that amount to the amount discovered via the gauge/piston height subtraction problem

OTHERWISE...
IF you are ABSOLUTELY CERTAIN that the felt washer (under the FINGER BUTTON) is supposed to be FLUSH with the finger button's skirt, measure the throw of the piston (port-to-port caliper measurement) and mess around with UNDER-CAP washers until the exposed throw on the exposed valve STEM matches the measured throw on the piston.

If this all reads like goobledegook, you might have someone do it for you.

I probably could post pictures, but I have to pull a sousaphone body out of the acid bath, right this minute (really).

(Bore scopes - along with anything with batteries or bulbs - are nuisances.)

OhTubaGuy wrote: ↑Sat Apr 13, 2024 8:35 am I want to check my piston valve height alignment, but I don’t have a Borescope or inspection mirror that fits inside of the neighbor valve casing. There are several valve positions that I cannot see when pulling the slides.

Is there a different way to check piston height, or do I need a mirror or scope?

You don’t need a scope but a 45 degree mirror would be helpful …. made from a pice of bent wire and a small plastic mirrored disc bought off of eBay. You’ll also need a small torch to shine down the bore. I’ve also used probes to check valve throw from the adjacent valve casing too. Long piece of wire with a 90 degree bend and a section extending the width of the valve casing.

Good luck; it isn’t hard and it is worth it, but it is also time consuming.

I opted to buy a mirror for $5.
https://a.co/d/4B7geHR
A 00 or 000 dental mirror would have more clearance.

The visual inspection confirms the original components are ok, but I will need to get some different felt and maybe a longer valve stem to use the new valve top cap and finger button.

Thanks for the suggestions!

OhTubaGuy wrote: ↑Thu Apr 18, 2024 3:04 pm I opted to buy a mirror for $5.
https://a.co/d/4B7geHR
A 00 or 000 dental mirror would have more clearance.

The visual inspection confirms the original components are ok, but I will need to get some different felt and maybe a longer valve stem to use the new valve top cap and finger button.

Thanks for the suggestions!

An ALTERNATIVE to "longer valve stem" is LOWERING the center riser on the top valve caps.

IF all the top caps, finger buttons, and washers are the same - YET you believe that you need ONE stem to be different...
...something ain't right.

OK...if your "new" cap/button are different...I could believe that a different stem would be in order.

=================================


I put a King front-action valveset onto a tuba body, didn't like how far the stems extended, swapped out the King "donut" top caps for Olds/Bach top caps (same threads) and was able to chop 1/8" off all the stems.

YES, I KNOW I'M WANDERING OFF TOPIC !!!

You are paying close attention!
I have a King sousaphone that was modified by the previous owner to graft a non-matching 4th valve onto the block. I am changing to larger finger buttons and decided the King 2341 buttons were both cost effective and comfortable. The original valve caps for 1-3 were machined to remove the flange/ring that would contact the large buttons. No problems there.

On #4, the original cap is short as you suggest, but the new button hits the valve cap when the valve is properly aligned in the bottom position. I have a new valve cap that matches the others, including the taller center riser. The new cap changes the top and bottom alignment.

In the photo, you can see the 4th stem is shorter than #3.

So, it looks like I need to adjust the open valve alignment for the new valve cap (new valve felt), then size the stem and button felt.

Does that make more sense and sound like a good plan?