Leadpipe specific dimensions

[mcjweller]

Hello!

I have a Bach TR300 bought new in 1987. It was an ok horn, but always very limited above the staff, never really slotted very well. It was a student horn after all, and served its purpose.

Years later, I still have the horn and have decided to make it a bit of a test mule for modifications/experiments to see what it would take to make it play better (subjective term). I have done some work on the gap which has yielded frankly incredible improvements in sound, pitch, and access to the upper register. But it still doesn't slot the way I'd like it to and the upper register still kicks out (or clamps down or tightens up, more subjective terms) earlier than it should. I've adjusted the gap to it's optimum by experimentation, now it's time to look at the leadpipe itself.

The stock leadpipe has a venturi of 0.352" This seems a tad on the large side, and would account for some of the challenges I've cited. It also has a stock gap of 0.222" which I have rectified using custom machined inserts (fortunately I have a small lathe and am able to make these at will).

Looking at other bach leadpipes, they have nice numbering like "25" and "43" with flowery subjective descriptions which mean nothing to me really. Bach websites simply list the material they're made from and which horns get which number of leadpipe, and leave it at that.

Surely somebody has actual measurements of the venturi size of these various leadpipes, and for that matter the inside diameter at the tuning slide end. I need to know both of these before buying one to experiment with on my TR300. Hopefully someone here can provide some data!

[Ed Kennedy]

The TR300 is a Bundy student model by another name. The standard leadpipe for that horn is the #6 which is tighter than a 25, 7, 43 etc. The 6 is a good pipe, it was used on the famous set of C trumpets made for the Chicago Symphony. It does soound like the venturi is off. I don't know what the factory spec is for that pipe and horn. I do know that the standard for the ML strads with the 25 piupe is .348.

I used to gig with a guy, Mike Leone (RIP) who preceded Ted Wagoner at the Bach factory. He is my source of info. he was involved in developing special models for pro players like the 72* for Bernie Glow, Al Stewart and many of the other NYC studio players of the 50's, 60's and 70's.

PS perhaps Jim Becker will chime in with some specific knowlege of the 6 pipe venturi.

[James Becker]

Thanks Ed for bringing this to my attention. I'd read somewhere that the Bundy 1530/Bach TR300 pipe was a #7 but could be mistaken, I've never bothered to plot the taper to find out.

Two things I've observed, actually three. First the length is a good bit shorter than a Stradivarius pipe (though it has the same wall thickness) so it's safe to assume it's simply trimmed shorter. Second, the mouthpiece receiver gap is larger by good measure, perhaps to offset the leakier valves and provide greater pitch center/positive resistance. Third, the upper tuning slide receiver is LT proportions .490" I.D. so only a LT Stradivarius receiver will mate with the tuning slide. However, since the tapered pipe is shorter the upper inner tuning slide tube is longer.

If you plan on a mouthpipe upgrade perhaps the Bach TR200 25 pipe would be a good place to start, but I'm not sure about the tuning slide receiver proportions, maybe it will fit? Anyone out there know for sure? If I'm not mistaken the tuning slides are very similar between the TR300 and TR200.

About the venturi size on the TR300. It's not uncommon to come across Bach mouthpipe tubes that are excessively flared out to make the receiver fit snug, compromising the critical small end opening dimensions (typically anywhere from from .345 up to .351) This is one of my pet peeves with Bach mouthpipes.

Now that the TR300 series are made in Eastlake, OH and the they're making their mouthpipes in gold brass to be longer lasting. I haven't experienced replacing the older with the newer. Anybody out there had experience retrofitting the newer pipes? Please chime in with your observations.

I hope this is helpful.
_________________
James Becker
Brass Repair Specialist Since 1977
Osmun Music Inc.
77 Powdermill Road Rt.62
Acton, MA 01720
www.osmun.com

Our workshop is as close as your nearest UPS store https://www.ups.com/dropoff?loc=en_US

[mcjweller]

Hi James, this is great info, thanks.

I don't have a strad to compare but, I can confirm the factory leadpipe on my TR300 is 6.8" between the receiver edge and the tuning slide receiver edge.

The leaky valve part is another topic. I have noticed some valve issues in particular below the staff, and with the third valve in particular, but I assumed thats more of a port alignment issue to be corrected with fine tuning. The valves seem to be actually in good shape, very little wear and of course they are Monel except they have 1-point guides instead of 2. (although it would take nothing to add brass in the casing to capture the left side of the guides...

As an experiment, I may make a sleeve to insert into the venturi (and a tool to get it back out) to reduce the opening. I could make it with thin walls, say 0.005", which would give me a venturi of .340", but it would also mess with the overall taper since this would represent a change in taper rate for the last half inch or so of the receiver end of the leadpipe

a .340 veturi would be pretty small so we'll see.

Ultimately, if I can improve the horn with a better pipe that's the way to go, it comes back to understanding the specifics so I'm greatful for your info plus any other info from other folks who may have tried this or measured different lead pipes.