Courtois AC420BO vs Bach 42BO rotary valves

[rptbone]

Would anyone happen to know if the standard rotary valve on the Courtois AC420BO is more open (or same valve) than one on the Bach 42BO?

[tbonesullivan]

I don't know about the dimensions, but the valves they use on the 420 and 440 look to be "traditional" rotors, much along the lines of the Bach 42B, and other trombone designs developed in the 60s and 70s. I don't know how large they are though, or whether they have better designed ports than the old designs.

[Burgerbob]

It's much, much better than the stock Bach valve.

[LeTromboniste]

Yep, it's better and I think, a significant part of what makes the Courtois an improved version of the 42. Although it's interesting that like the Bach, the Courtois still benefits a lot from the Hagmann valve, which goes to show that there are perhaps other aspects of the 42 design that just work better with more open F attachments (beyond just the valve itself being bad).

[rptbone]

Thanks for the replies. So it appears then that perhaps the Courtois rotary valves are improved vs the standard Bach valves. Exactly what the improvements are we may never know, but that’s okay, as I trust the input from those who have tried both.

[Burgerbob]

They're bigger, and not designed in the '30s. Doesn't take much to improve on them.

[rptbone]

Did you make any measurements to compare?

[Posaunus]

Did you make any measurements to compare?

From what I understand, it's not just the Bach 42 valve's (relatively) undersized dimensions that make is such an unpopular choice, but the entire valve design. Almost all of the newer valves are reputedly much better in several ways. An impeccably-dimensioned engineering drawing will not reveal those differences!

[Burgerbob]

No... there's no need to measure. Just play 'em.

[rptbone]

BurgerBob, would you mind expounding on your comment “ It's much, much better than the stock Bach valve”?( e.g. more open feel, etc.)

[Burgerbob]

They feel and play better.

[Posaunus]

rptbone,

Do you care only about how "open" the valve is, or do you want an all-around better valve than the Bach 42's?

The best way to find what you want is to play the candidate trombone(s) and compare to the Bach 42, not to measure or look at design drawings.

[rptbone]

My question about the valve is borne from the multitude of comments about the Bach rotor valve being “stuffy” or “not sized properly”, etc. There are indeed measurements involved here, however I do realize that what also is affected is the entire F-attachment system tubing sizing. There is a reason why there design drawings at the factory, rather than blind faith. There’s a reason why one is better than the other, not “it’s better because it’s better”.

[Burgerbob]

Yes, the valve is better. We went over this!

[Posaunus]

Since none of us have these manufacturers' detailed specs or design drawings (which in any case are not particularly accurate predictors of playing performance), I guess you'll have to take Aidan's word for it or try them out yourself.

It's not rocket science - it's harder!

[rptbone]

What do you mean by “better”? That is very subjective. It is better because …? “It’s better because it’s better” is meaningless which is why I prefer to include an engineering approach. No need to reply since we are going around in circles here. You said at one point the Courtois valve was bigger. How do you know that? You likely don’t know, so no worries. Moving on.

[GabrielRice]

rotbone, you're on a trombone forum, not an engineering forum. If you ask trombone players what plays better they'll tell you, and they won't be able to prove it to you empirically by telling you about the design of the valve unless they happen to also be instrument designers.

Burgerbob (Aidan) happens to be a really fine trombone player who loves gear and has tried a lot of trombones. His opinion means something.

That said, how a valve plays is not just about the design of the valve; it's about how it's mounted in the instrument, how carefully the assembly was done, and the design of the instrument around the valve as well.

I happen to own a Bach 42B with a standard valve. It started as the standard Bach closed wrap, and somebody (I don't know who) did a nice open wrap job to it. It plays great in and out of the valve register; better than other Bach 42s with fancier, newer, "better" valves that were in the same well-stocked store at the same time. It's not even from a particularly prized vintage. Maybe the open wrap conversion included opening up the ports of the valve? I don't know and I honestly don't care.

[Matt K]

The Bach 42 valves are notoriously... well... awful. All it takes for them to be better is to not be awful. In the case of the open wrap 42BO you can even visibly see that the design uses the wrong part for the exit port completely unaided by any measurement device.

[rptbone]

Ok

[Burgerbob]

I'll apologize, my answers were not very helpful. They're true answers but not giving enough information.

The 42 valve is undersized, with smaller ports than the .562 valve tubing used in the wrap, so there's a constriction there. Despite that, random 42s with rotors (both open and closed wrap) can play very well, as Gabe noted.

Almost every rotor since then has been better in some small way, even the Conn rotors from the same period. You just have to make them a bit bigger, design the core in a smarter way, use modern machining, the list goes on, and you get something better than most of the 42 rotors out there.

I couldn't tell you the exact difference that Courtois made to that part of the instrument, but it's going to be a significantly more thought out design (with several decades of improvements to draw on), better clearances, consistent parts, etc.

It's also, sadly, apples and oranges at the end. The AC420 is obviously a 42BO clone to a degree, but it will never be a real 42. I think the Courtois tend to play better on average, but the Bachs will have THE Bach sound in the end.

[rptbone]

Makes sense, thanks

[hornbuilder]

Here is a picture of a Bach 42B rotor, with .562" ball sitting in the port. You can see quite clearly that there is a portion of the ball protruding beyond the diameter of the rotor, thus, the bore is constricted by that amount through the valve. Twice when it is activated. Speaking very simply, all you have to do to make the valve "better" is to design the rotor so that less of the ball sits outside of the rotor diameter.

[rptbone]

Matthew, thanks for the demonstration photo...it's worth a thousand words. I wouldn't doubt the standard rotary valve on the Courtois AC420 is the same one used on the B&S Meistersinger Stolzing, as it's f-attachment section is advertised to be 0.570". And both are made in the B&S factory in Germany. I will also rely on previous comments from experienced players who have tried both the Bach and Courtois.

[Posaunus]

There's a lot more to the difference than the F-attachment section tubing diameter. It's also how the valve internal flow passages are designed and how smooth they are, with no sudden changes in flow shape or size, how tight the assembly tolerances are, how the valve attaches to the inlet and outlet tubing, how much flow resistance is in the valve and tubing wrap configuration, whether the solder junctions are carefully smoothed, whether there are any leaks in the joints, etc, etc, etc. In other words, lots of aspects of engineering (and intuitive) design and construction. And a fair amount of proprietary know-how!

[harrisonreed]

Just my two cents, make sure you actually play test a Courtois for a good bit before you buy one. At first blush, they play miles above your average 42. The valve is obviously better.

But, something that might not become apparent until later:

Screenshot_20240111_201129_YouTube.jpg

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Are the short slide barrels. Not a deal breaker by any means, but not something you want to discover after your hand suddenly looks like picture 2, above.

[rptbone]

Looks like in those photos he doesn’t know how to hold a trombone properly.

[ZacharyThornton]

The person is having to hold the trombone differently to keep from getting their fingers cut by a returning slide.

[harrisonreed]

Looks like in those photos he doesn’t know how to hold a trombone properly.

Sure. It's two different guys. Amongst the top players in the world. They figured out ways to make it work, is what it is.

Look, they're good horns. Just don't buy sight unseen, give em a good go at a conference so you can see. The ergonomics are really bad on them, despite playing nice.

[rptbone]

I had that problem with short barrels on my Conn 88H and a 6H, so got rid of them. My Courtois AC420BOR feels great in the hand with no issues, using a common or traditional hand grip. Ergonomics are excellent.