Jump to content

How to move tuba valves remotely


GridGirl

Recommended Posts

One of my musicians came up to me today with an interesting one; he's a brass repairman as well as a tuba player, and was contacted by a magician who wants him to rig up a tuba so the valves can move by themselves (as if a ghost is playing the instrument). He's a bit stumped, and asked me because he knew I come from a theatre background. My first thought was servos - the issue is they have to fit in a small diameter cylinder. They only have to move 3-4cm; anyone have any suggestions?! They also need to be relatively quiet!
Link to comment
Share on other sites

Provided that the tuba does not need to be actually played then the size and shape suggests replacing the valve piston with a solenoid and making a false button which looks like the original. You'd need a rubber or felt stop to damp out the sound of the valve. Nice little project for someone with a lathe. What are the dimensions of a tuba valve?

 

Edit: The challenge with solenoids would be finding one with adequate stroke length. An alternative might be a miniature stepper motor with a lead screw. It would need to have a coarse pitch to make it operate quickly enough but there are some surprisingly tiny steppers out there.

Dave

Link to comment
Share on other sites

Ooooh this sounds right up my street! :)

 

Servo's will be a struggle - they'll require plenty of space around them to allow that kind of throw. Linear servos do exist but their throw is pretty short. Solenoids again may work but their throw length might be a bit short. It's very possible to thread wires around a brass instrument - I know, my parents currently have a trumpet for a reading lamp!

 

There's plenty of space elsewhere in a tuba, so maybe you could stash servos etc. in the bell and then use bowden cables to drive the valves. With the springs removed and a regular dose of valve oil they should move very freely so whatever is used shouldn't need much power.

Stepping up the complexity slightly, but another thing that comes to mind is that the valves are, by their nature, sealed. With some plumbing you could maybe either use air or vacuum applied below or above the valve to make it move. Stash either a vacuum reservoir (with an external pump that you plug in just before the act to evacuate) or a small air cylinder (I've used airbrush propellant cans to good effect before) and the tuba may well do most of the work for you. 3 solenoid valves and an arduino driving the sequence and you're home and dry.

Link to comment
Share on other sites

You have a tuba you can wreck is my first question? Knowing a tuba player I know he'd rather have an operation with no anaesthetic than allow anyone to stuff something inside his valves! I've never even seen a second hand one for anything less than silly money. Bit like Baritone saxes - they're not common, none are cheap new and second hand ones that are unplayable because of damage might be your only solution. Good illusion though and if damaging the thing is OK and it doesn't have to play again, then external mechanics and fishing line through drilled holes could be a possibility. If you put something inside the valve housings, you still need access for the control/power?
Link to comment
Share on other sites

Done it (to other brass instruments) for magicians.

 

1) it's going to completely destroy the instrument, it will never play a tune again

2) the effect and movement is really small and subtle when compared to the workload and cost involved - 5 rows back in the audience and they won't be able to see the movement.

 

In a nutshell you can get small pnumatic pistons that are round and about the same size as valves, fix a mushroom head on them and spray with brass colour paint. Then just bolt/cable tie them on to the instrument roughly where the old valves were, run external pipes (also painted appropriately) either to a bank of solenoids hidden in the table or mounted inside the horn. There's so many pipes and detailed metal bits on most brass instruments that it's a waste of time hiding pipes inside pipes. It all gets expensive though, £500 for a cheap battered instrument, £300 for the pistons/tube/solenoids/controller and 2-3 days labour is the sort of price point it would be in the UK

Link to comment
Share on other sites

How close are the audience? Make some pistons (think hypodermic syringe design as a starting place) and attach them to the side of the existing valves (unscrew and remove as much of the originals as practicable to reduce their footprint)operate them with air. Probably no need to harm a good instrument. If the pistons are small enough they may be able to be installed in the vacated valve void. Animatronics are operated with pistons.
Link to comment
Share on other sites

Likely non of the audience really know a tuba, so maybe some rebuilding is reasonable, invent a pipe or two to contain the works.

Tubas can have rotary valves or piston valves and some may have up to six valves.

 

However, the sound of a tuba is initiated by the player's lips. I'm unsure of the concept of driving a tuba without a player, unless someone also wants to make a reed assembly. You don't just "blow" a tuba, you have to blow it a rasberry (under strict control!). So currently I don't see how an unattended tuba will play a tune, no matter what animatronics.

 

Ultimately the effect has to be worth the serious money involved. Ebay does offer some half reasonably cheap instruments.

Link to comment
Share on other sites

However, the sound of a tuba is initiated by the player's lips. I'm unsure of the concept of driving a tuba without a player, unless someone also wants to make a reed assembly. You don't just "blow" a tuba, you have to blow it a rasberry (under strict control!). So currently I don't see how an unattended tuba will play a tune, no matter what animatronics.

 

From what I understand, there'll be a speaker placed nearby that the sound is coming from - the tuba itself won't be producing the sound. I gather that the magician has bought a second hand piston valve tuba from somewhere (rotary valve would be even more difficult to rig up, I think) and it will never need to be played again, so wrecking it isn't an issue! My engineer husband also suggested solenoids - the trick is going to be finding ones with a long enough stroke. Thanks all for the suggestions - I'll pass them on to the guy who asked me the question! And if I see photos I'll try and get hold of them to post here :)

Link to comment
Share on other sites

My engineer husband also suggested solenoids - the trick is going to be finding ones with a long enough stroke.

 

Might organ drawstop solenoids be an option? 25mm stroke is fairly common, would that be enough? Although you may have trouble fitting it inside due to the size. Putting it further inside the instrument with some sort of flexible mechanical linkage to the actual valve 'button' might be an option though.

 

On the plus side though they are fairly reliable units since they are designed for years and years of constant bashing and moving by organists!

 

Here is the sort of thing I mean Kimber Allen Drawstops.

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.