TromboneChat

Hello Chatters!

Okay, so how accurate and reliable are the little hash marks on rotor valves? I feel like they SHOULD be accurate, but I also feel like I should buy a cheap borescope and have a look at my horns and see. And French horns are difficult to eyeball anyway, so I should probably invest in one.

What are your experiences? I'm especially interested in techs and their experiences.

Get a borescope The timing marks are usually pretty close, but some are closer than others.

borescopes are cheap & fun. Totally worth it even if the marks are good. On the other hand you may not want to see whats inside your instrument.

On trombones, just as easy to sight into the slide receiver to check the rotor registration.

I don't rely on the factory marks.

Boroscopes are cheap, the one I found was under $20 shipped.

Eric

Bonearzt wrote: ↑Tue Jul 31, 2018 11:46 am On trombones, just as easy to sight into the slide receiver to check the rotor registration.

Not always- dependent bass for example

Bonearzt wrote: ↑Tue Jul 31, 2018 11:46 am On trombones, just as easy to sight into the slide receiver to check the rotor registration.

I don't rely on the factory marks.

Boroscopes are cheap, the one I found was under $20 shipped.

Eric

I need one, do you have a recommendation?

timothy42b wrote: ↑Tue Jul 31, 2018 12:05 pm

Bonearzt wrote: ↑Tue Jul 31, 2018 11:46 am On trombones, just as easy to sight into the slide receiver to check the rotor registration.

I don't rely on the factory marks.

Boroscopes are cheap, the one I found was under $20 shipped.

Eric

I need one, do you have a recommendation?

For this type of work, small & flexible is more important than high pixel count. I got mine from Amazon, search for 5mm borescope. there are a variety of connections available; USB, phone etc depending on how you want to view.

One of the things we lost in the first upgrade of THIS site was a thread on borescopes, with pictures. From that, a handy search string for ebay would be:

3.5/2/1.5/1M 5.5mm Android Endoscope Waterproof Borescope Inspection Camera 6LED

This technology is moving along briskly. I'd focus on low price, and be ready to buy another later, rather than try to figure out what is a really good one right now.

The ones (like the above) that come with a right angle mirror can be difficult to use with the mirror. The protection on the mirror needs to be peeled VERY carefully, then the mirror needs even more careful cleaning... often. OTOH the LED itself seems as immune to moisture problems (both mechanically and optically) as one could hope.

Once you get one and look at the alignment in the bore vs. the hash marks, you'll never go back to the hash marks. One thing I have noticed, even on VERY good valves, is that being able to get a well-lit, close-up view of the valve from BOTH directions shows that VERY few of them are dead on. I'm not saying the valve makers aren't doing a good job... I'm saying they deserve a LOT more credit than they get, because there's a LOT more to getting them "right" than a non-machinist would ever guess!

If you get a borescope and see mismatches, don't be surprised. Just be grateful the makers have the skill to keep those mismatches as small as they are!

I think I spent $12 on my borescope off Ebay. Well worth it. Works great with my Android phone.

A lot of times the marks are reliable. A lot of time they're not. Also, things wear, and what used to be reliable may no longer be.

How accurate are the hash marks? That depends entirely on what the tech that made them considers to be "correctly aligned"!



M

Even with a really carefully made hash mark, a couple things come to mind:
1) it's not just the mark for the axle that matters; there's also the mark for the bearing plate
2) on typical trombone rotors, any error in eyeballing the mark vs. the passageways is up around 5 to 1.

Of course, we should keep this in perspective: makers have been laying out these marks LONG before there were borescopes, and built some phenomenal horns. Definitely a "point of diminishing returns" in fussing with getting the alignment "just right." Makes FAR more difference if the valve leaks internally than if the alignment is just right.

hornbuilder wrote: ↑Tue Jul 31, 2018 4:48 pm How accurate are the hash marks? That depends entirely on what the tech that made them considers to be "correctly aligned"!



M

Funny, I was thinking that the valves that seemed best aligned to me came from a certain maker you worked for at one time

I started a "thread" a couple of years ago on TTF about how great it was to be able to use a $10 boroscope to inspect your valves. Unfortunately, like so many other topics of interest, it was lost when TTF "took a dump" ! I'm pleased to see that some remnants of that information has survived and is being taken seriously. A fully open valve is obviously going to produce the optimum result of which the designer intended. I am embarrassed to say that I cannot remember who it was who added great photographs of his personal results with the idea, but it was beautifully done. Carry on ---- boroscopes at the ready ! Cheers !! Bob

I'm glad this topic has been useful - and I just ordered mine.