[batadunbata]

Hey,
So I came up with a device which can tune the Djembe up or down in a matter of seconds,
and I wonder what people think of the idea?
I know some folks will understand why this would be useful, and some will wonder what the point is. It would be useful for humidity/temperature changes, and imagine being to play high pitched for a solo, and tune down to sink into the background. And you could tune down for safer transport.

Anyway, the device is simple. It's an inflatable band, which fits under the verticals.
It tunes by expanding, which effectively shortens the distance between the top and bottom rings.
Provides a full range from the lowest useable pitch to the highest.
Yet it's fairly discreet. It doesn't need to expand much to adjust the pitch considerably.

It's easy to install: simply loosen the verts until you can slide something under them with a little effort (this only requires them to be low tuned, but not at all loose).

To tune up, simply inflate the band until the drum is at desired pitch. I would use one of those hand pumps that nurses use to inflate blood pressure arm bands. This would be very fast and has a release valve built in.

The band would be made of canvas, coated with latex on the inner face. Laid out flat it's the shape of a thin rectangular box, but the outer side is slightly longer than the inner, i.e. trapezoidal at the ends. It has a valve attached for inflation/deflation at one end. The two ends meet between the vertical seam (the gap where the verts begin and end).

I would also glue thin bamboo slats or wood veneer on the outer face, to give the verticals something stiffer to press against, and distribute their pressure/force. Wood veneer would match the drum nicely. The canvas or wood can be dyed with natural wood pigments to match the drum wood.
I can provide a drawing/diagram if that would be helpful?

[djembefeeling]

That actually sounds like a totally cool idea! The only critical point might be that I guess that skin is likely to break much faster when it is tuned back and forth often?!

[batadunbata]

Oh I didn't think of that, thanks Djembefeeling.
Much better to know ahead of time than to find out the hard way.
Now that you mention it, I recall a post by Michi about how skins can break when repeatedly tuned up and down.
So it wouldn't be for frequent tuning, but still saves having to pull diamonds, and can help with humidity changes and travel.

I got the idea when I wanted to tighten my Djembe without having to pull another row of Diamonds. It's a lot of exertion and I have a physical ailment.
I ended up wrapping/wedging the spare rope around the bowl under the verticals to push them outwards, and when I'd used that all up, I wedged some coins (quarters and pennies) into each pair of verticals to make it even tighter. It worked, but I'd like to tune it up just a little more, and now the verticals are too tight to push any more coins in by hand.
Viola or Cello pegs might work (they're tapered like wedges), but then I had the idea of the inflatable band, which would be more discreet, streamline, and quick to tune.
I might say goodbye to pulling diamonds once and for all, if it works as I imagine.

[the kid]

I can't really imagine this working.

It's a good idea but i would think the pressure from the ropes is too much to allow a chamber inflate under them.

If tuning is too hard a more elaborate roping system could be developed like a secondary rope system over the first set of normal ropes. Then pull secondary verts on pulling rack.

Also beat the rings down with a mallet is a quick and easy way to tune a drum.

What tool is used to tighten the verts and pull diamonds would be a factor as well.

[michi]

You'd need a huge amount of air pressure to perceptibly move the verticals. I suspect more than you could achieve with a simple hand pump. And, even if that were possible, the device would quite likely be dangerous: a puncture could result in an explosion that might take out someone's eye with some small plastic fragment.

In theory, I think it would work, but making it work in practice seems unlikely to me. It would be a very high-tech solution to a very low-tech problem

Michi.

[djembefeeling]

I go with that low tech problem, cause I hardly ever need tuning down. And if I do, the one or two additional diamonds are undone in no time. But I still think it'll work. Such an inflatable band would run under all diamonds and would lift all at once. Even a little uplift would have a noticeable effect. Go for it, it's worth a try...

[michi]

I'm skeptical. The amount of force required is huge. Even if you can exert that much pressure on the verticals, what would that do to the bowl? There would be a large amount of inward force onto the side walls. Not sure whether all bowls would be able to take it…

Michi.

[batadunbata]

Sure, you can pull and remove diamonds, but this is faster and easier. I'm not a fan of diamond pulling, I have health problems and it's draining.

And those are understandable concerns.
I did consider them myself while designing it, and here's what I thought:

1. Pushing the verticals outward works. I did it with rope and coins. It's the same concept as diamonds, i.e. you shorten the rope by making it travel at an angle instead of a straight line.

2. The trapezoidal shape should prevent contracton inward, and concentrate the force outwardly.
(I agree, a simple rectangular band might compress the shell, although a wood circle would resist distributed compression fairly well)

3. Air pressure is actually very powerful. A thin sack is used to split multi-ton slabs of marble, after being inserted into a thin cut made in the rock.
Consider that 1 PSI is 1 lb per inch.
So a bike tire @ 60PSI contains 60lbs of pressure per square inch.

A Djembe head, according to Michi's post (somewhere in the forums) needs something like 800-1000lbs of pressure.
If you have 26 verticals, that's somewhere in the range of 40lbs per vertical, give or take.
So if you can apply 40lbs to the vertical, you can bring it to tension.
So you only need 40psi, if you can contact 1sq inch worth of the vertical's surface.
This should be possible if the band is wide (~2-3 inches) and has a stiff surface (wood veneer or bamboo skin/slats).

4. Puncture will not cause explosion, and will not send any fragments outward. I know this from researching air powered cars. In cars, the tank is brittle, so you would expect explosion and fragments, but it doesn't work that way for some reason, a puncture doesn't rupture it simply leaks rapidly. The danger with air pressure is in valve pieces being shot like projectiles, but the pressure here isn't sufficient to rupture the metal valve or cap. It would leak like a bike tire. Also, I'd be using heavy duty canvas.

5. The hand pumps may not be powerful enough, but only by a little (they add pressure in increments through a one way valve, and the human hand can compress a 30psi bulb dynanometer)
Here's a hand squeeze pump that's rated to 60psi:

[drtom]

My immediate impression is that for something to be inflatable it has to have give. Anything with give is not going to significantly budge rope that's as taut as steel cable.

[michi]

Well, with enough pressure, anything will move. If you go ahead and try this, it would be really interesting to see the results, success or failure!

Michi.

[the kid]

for something to be inflatable it has to have give.

Yea thats prob true, and the result if there is any give would be bulges between the vert ropes.

I would also glue thin bamboo slats or wood veneer on the outer face, to give the verticals something stiffer to press against, and distribute their pressure/force

A veneer of wood between the ropes and chamber would not be strong enough, i would think, plus the loop of veneer would be expected to expand due to the outside of the chamber increasing in diameter as the chamber expands.

Still the pump is nice, , and the idea is good. It would be possible to get it working with the right materials.

I never really tune down a drum unless it gets a scratch or gets wet or something. Would someone really want to tune down the drum to play support and tune up for solo. Generally a change in technique suffices.

A pulling rack would really be good for someone who hasn't the energy to tune drums with a lever or dowel. Can you can pull diamonds on a rack too? I don't know. Probably.

[michi]

Can you can pull diamonds on a rack too?

Sure, no problem. I do it all the time. No need to sit on the floor, and things are nice and effortless that way.

Michi.

[drtom]

Inflatable tuning systems are used on drums already, but frame drums and zarbs don't require the force that djembes do. And I don't know how reliable these systems are - I've had one person contact me about repairing one.

Problems are good for solving, though. I wish you luck and hope you keep us posted.

[boromir76]

Very interesting concept.

This system would be quick, effordless and handy, no doubt about it.

On the other hand it would probably need more tensioning corrections compared to good old "back breaking" prestrached rope tuning system. Air osmosis(?) or permeation of the band would possibly lower the pressure at least on long term run. This effect would be summed together with fresh skin strech during first few weeks of tuning fresh skin. The tension would be probably corrected with few hand pump squeezes, but this is not my concern. I wonder if and how the skin would be affected with more stretching and pulling...

The second thing that intrigues me, is how much initial tensioning would the verticals need, before they could be air tensioned sufficently. Can this system produce so much volume and tensioning power that the verticals don't need any serious hand/ pulling bar tensioning?

I wish you luck and hope for the best with the tuning system. Update us on this concept, please!

[batadunbata]

Thanks for the support all. Lots of good points were made, very helpful, thank you.
I'll be sure to update if/when I have the device made.
I'd use something stiffer than veneer - thank to The Kid - (I'm surprised I missed that myself but grateful you didn't. It wouldn't stretch and bulge as much as the fabric, but it would likely crack. Maybe multiple layers glued together and sealed in resin, like how archery bows are made)

I've had another idea/invention which I'll post soon, which would make pulling verticals effortless, and thus no need for diamonds, so less need for this belt, though it might still be helpful for making minor adjustments to tension, as humidity changes.