Bearing edges - shapes, sounds, questions

[taikonoatama]

Bearing edges

I'd like to learn more about something about which I am sorely naive: bearing edges.

I've owned many types of congas and seen a lot of differently-shaped bearing edges, and the only thing that is clear is that nothing is clear. JCR, Skin on Skin, Junior Tirado, classic Gon Bops, King Congas, Mambiza - they're all quite different. Some have the high point in the center of the shell and cut down sharply at a 45 degree angle toward the inside of the drum. Some have the high point more toward the outside of the shell. Some the inner. Some go flat straight across after the rounded edge and then down 90 degrees on the inside. Others continue the round all the way to the inner edge and then down 90 degrees. Some are simply round on both sides of the high point. And there's a big range of curvature on the outside of the bearing edge across all the drums, and probably more variations I'm not thinking of.

So what's the deal?

There's not much information out there specific to congas, though there is for snare drums.

Snare drums bearing edges are most commonly cut one of two ways:
1. The high point in the center of the shell, with 45 degrees slopes to either side.
2. The high point along the outside edge with a single 45 degree slope down toward the inside

60 degree slopes are also done, as is a slight rounding of the high point of the rim.

I'm not sure how much this applies to congas, as the desired sound characteristics are so different, as is the head material (even when using synthetic conga heads, I'd imagine) and, by necessity, the rounded outer edge of the conga shell, amongst other things.

This brings a question to mind, though: Following the skin from the center of a conga to the metal rim, once the skin touches the high point of the conga shell bearing edge, does it make any difference what the shape of the shell is after that point? In other words, the severity of the outer curve of the bearing edge? The skin remains in contact with the wood throughout that curve regardless of shape.

My intuition says that the sharper the bearing edge the sharper the tone/attack, and the flatter/more rounded the edge the more dampened/rounded the tone, but if this is true I'd like to understand why. For a snare I can understand it, because I believe the head only contacts the bearing edge at the highest point, and doesn't not remain in contact with the shell after that point, but congas are different.

Also, I would think the edge shape would vary with the size of the drum to some extent, but I haven't seen it to much, with drums from the same maker.

Membraphonically yours,

~Taiko



Edited By taikonoatama on 1182202148

[Tonio]

Taiko,
interesting topic. It seems most mass produced tubs have a some somewhat flat bearing edge centered, with a tapperd curve on the outside.
I remember depending on size of the drum, old Gon Bops had a round bearing edge to the outside, or it could be on the center. The inside didn't have much of strick angle, more rounded out.

EDIT; I just remembered I had quinto 9 3/4 with rounded eadge , not much contact on the outter edge, same w/ a tumba. But I later got a 10 3/4 quinto and it has the angled inside with hardly any outter contact.

The LP (classic ) has a rounded outter curve, and a sharp inside, with the bearing edge on the center, somewhat flat. The outter curve has alot of skin surface attachment.

Maybe attributes do have a priority of " the sound" the drum produces.

I have had LP Gen 1 bongos w/ round through out the top structure, and the Gen II is sharp as heck on the outside.



T



Edited By Tonio on 1182205708

[bongosnotbombs]

Just to apply my construction knowledge to congas,
a rounded edge would be stronger, sharp wood corners,
especially and acute one which would be a bearing edge are not very strong and would be prone to chipping.
It is true a round edge would have a larger contact patch. A larger contact patch would also put less stress on the skin.
One method or the other would probably creat a more precisely round shape, which may allow the skin to seat more evenly.
Also the rounder shape might allow the skin to pass over it more easily as well when tuning.