Plate design

[Dicemanb]

Hi Gents,

Couldn't help noticing that they were brass PLATED (probably on steel) and that they are being replaced with bronze alloy.

'Currently under developement. The new model lineup will have an improved design of the form to ensure even better sound. Also all brass plated parts are being replaced with bronze-based alloys, due to the environmental hazards of brass plating processes. All prices are estimates until new manufactirung process has been finalized.'

They do look tasty though.

Dice

[congalou]

Hey !

Some news about my futur plates, the first model in resin is OK, next step : the mold.

G.

[Dicemanb]

Awesome Congalou,

You say, you do.... respect.

Dice

[blavonski]

Mechanically, to minimize the stresses on the shell, I think this is a better design than the Cuban plates which have 2 bolts on top and one on the bottom. Also to minimize shell stress, you want the distance to be a short as possible from the shell surface out to the axis of the tuning rod. You also want to make sure that a wide variety of wrenches will fit easily for tuning, without hitting the heads of the mounting bolts. For that reason, you may have to space the two bottom bolts further apart than it looks like in your drawing. Not a problem for fiberglass shells where you don't have to worry about drilling the shell through a stave joint, but too wide could be a problem for stave wood shells.
CAD is nice, but you might want to weld up a rough prototype of your best design to test the wrenches and shell-to-tuning rod distances before you go to the work of casting a whole set.

Jorge/ Congalou,
For what it's worth,
Because the stress on the plate is all in the same direction, (upwards),and not being pulled away from the shell; it actually makes no difference how the plate is appleid with regards to the two holes being on top or reversed, there are still three bolts fixed with in the same area,(triangle). And because these plates are made to resist tension, Brass is not neccessarily a bad choice, but it has a lower tensil stength than carbon or stainless steel, and high quality carbon steel is stronger and doesn't bend as easily. Also, Brass is not as elastic as say structural steel, that means if by putting the plates for example under constant, repeated tension, the nipple on the plate may stretch over time. But, that could be a long time with this application.

To ultimately minimize shell tress at a lug plate point, ideally a larger plate could be used, whereby, for instance, the 3 points/holes of the triangle plate would each have there own stave to be bolted into, that way, not only one stave is bearing the stress from each plates' tension. Multiply that by four or five plates, that would be 12 -15 staves carying the stress instead of four or five staves.
It might not look as sleak as the one you have there, or what has been traditionally used on Congas for ever to pleasing and lasting results, but theoretically speaking, it is more structurally sound.

Good luck with your project!

Godd vibrations,
Blavonski

[congalou]

Hi guys !

Here is the plate in brass just out of the mold. I just try a gloss finish on the nose.

Hi Blavonsky !
I think you are right about the one stave for one hole, it's the better way for a heavy construction. But specially for my drums, I prefer made a smaller plate with the design I want and more light compared to a big plate. Because I fiberglass the drum outside and I have a super solid shell capable to recieve that, it's not a big problem if I have all the holes on 2 staves.

But concerning the 2 holes on the bottom, I really think that it's better compared that 2 holes on the top. Shure It's not a super big difference but I feel it's better, and I like the look !!!

G.

[KING CONGA]

Man that really looks nice. Can't wait to see the finished product. Great job congalou.

[blavonski]

Hi guys !

Here is the plate in brass just out of the mold. I just try a gloss finish on the nose.

Hi Blavonsky !
I think you are right about the one stave for one hole, it's the better way for a heavy construction. But specially for my drums, I prefer made a smaller plate with the design I want and more light compared to a big plate. Because I fiberglass the drum outside and I have a super solid shell capable to recieve that, it's not a big problem if I have all the holes on 2 staves.

But concerning the 2 holes on the bottom, I really think that it's better compared that 2 holes on the top. Shure It's not a super big difference but I feel it's better, and I like the look !!!

G.

Hey congalou,
yeah, I hear what you're saying concerning a solid shell. my theory was for staved drums in particular. It makes sense what you write regarding the 2 hole placement...we generally feel good about what looks good to us, but structurally speaking, it makes no difference...purely an aesthetik choice.
They look nice, look forward also to seeing them at work.

good vibrations,
B-

[jorge]

Mechanically, to minimize the stresses on the shell, I think this is a better design than the Cuban plates which have 2 bolts on top and one on the bottom. Also to minimize shell stress, you want the distance to be a short as possible from the shell surface out to the axis of the tuning rod...

Jorge/ Congalou,
For what it's worth,
Because the stress on the plate is all in the same direction, (upwards),and not being pulled away from the shell; it actually makes no difference how the plate is appleid with regards to the two holes being on top or reversed, there are still three bolts fixed with in the same area,(triangle)...Blavonski

It is not true that the stress is only upwards. The plate acts as a lever, with the lever arm being the distance from the shell surface out to the center axis of the lug. As the lug pulls upward, there is a compression force exerted on the shell at the top bolt and a tension force exerted on the bottom bolts (in addition to the shear forces exerted on all bolts). The system is stronger in compression than in tension, so two bolts bearing the tension at the bottom are better than one. Regarding the shear forces, it makes no difference if the two bolts are on bottom or top, but regarding the tension forces, Congalou's proposed configuration should be superior to the two bolt on top design.

[blavonski]

Mechanically, to minimize the stresses on the shell, I think this is a better design than the Cuban plates which have 2 bolts on top and one on the bottom. Also to minimize shell stress, you want the distance to be a short as possible from the shell surface out to the axis of the tuning rod...

Jorge/ Congalou,
For what it's worth,
Because the stress on the plate is all in the same direction, (upwards),and not being pulled away from the shell; it actually makes no difference how the plate is appleid with regards to the two holes being on top or reversed, there are still three bolts fixed with in the same area,(triangle)...Blavonski

It is not true that the stress is only upwards. The plate acts as a lever, with the lever arm being the distance from the shell surface out to the center axis of the lug. As the lug pulls upward, there is a compression force exerted on the shell at the top bolt and a tension force exerted on the bottom bolts (in addition to the shear forces exerted on all bolts). The system is stronger in compression than in tension, so two bolts bearing the tension at the bottom are better than one. Regarding the shear forces, it makes no difference if the two bolts are on bottom or top, but regarding the tension forces, Congalou's proposed configuration should be superior to the two bolt on top design.

Ok, Jorge,Allmost all.... but it is the tension stress that is primarily the issue with this type of structure and the pull, (tension) on the nipple/plate through the Lug is almost all unidirectional and upwards. Sure there is some lateral movement at the sides of the plate, because all solids when under stress and strain have it, but because the plate is so small and thick it is extreme minimal, and one may never see or feel it unless that nipple really loses it elasticity.
Compression deals with pushing, Tension with pulling and shearing deals with sliding. Because the longitudinal force is unidirectional upwards, how is the plate going to slide and or twist in order to work at exacting enough shear force on the bolts to weekend them? Even if the plate was loosened enough to create excessive lateral movement, I believe the wood would crack at one of the holes before a bolt would ever shear off. And, incidentally, it is the Lug threads that are under the greatest, true shear force in this set up. It's always a problem egineers have deciding what materials to use when fitting ends to two points being tied together. That’s why lugs strip before any other part goes. It’s the threads shearing away from sliding against an eaqually hard or harder material under tension and or compression force.

Also, the compression that you refer to is actually happening at all bolt points not just the top. But it is the wood, not the bolts that bears the brunt of that compression when the bottom of each plate hole is pulled and compressed against the bottom of its corresponding bolt, then transferred, upwards to the edge of the hole in the shell. Wood is softer than the bolts, so it will react to that compression before the bolt does from the plate.The Bolts main role is for fastening the plate to the shell. When holes are put into any material that material is weakened; therefore, it is recommended to put only as many holes that will hold the thing firmly in place. That’s why in my opinion, even though the shell solid, a slightly wider or longer plate would help to displace the load on the weakened whole area.


“Regarding the shear forces, it makes no difference if the two bolts are on bottom or top, but regarding the tension forces, Congalou's proposed configuration should be superior to the two bolt on top design.

That's sort of a contradiction isn't it? for is it not due to the load on the nipple and plate caused by the tension from tightening the lug that in turn creates compression on plate holes, bolts and shell holes? Shear stress is Tension and Compression acting together. Moreover, because the main area of strain concentration here is on the nipple itself, if there’s any shearing going to happen, it will be the nipple that can theoretically shear away from the plate body. It is actually the nipple acting , to use your term, as a lever, and the plate body is a jig for the nipple to have someplace to be to do its’ work. It’s the nipple and where it meets the plate body that is under the greatest amount of tension stress in this area not the plate itself, nor the bolts. And, in my humble opinion, the plate could actually be a vertical rectangle and half the thickness of Congalou’s with only two bolts securing it to the shell and I’m sure it would be fine. I’ve personally seen Congas that have a two bolt, rectangle plate that have had there skins stretched over 20 odd years, and those plates are in tact, but nipples show signs of creeping,( Stretching ). Or, the lugs have been replaced because of stripping over time. Also, if, as you assert, two bolts on the bottom/one on top are superior than the other way'round, then why do congas with this type of construction continue to be made and lasting? As I wrote before, it’s an aesthetic choice and I think history supports that thought. But, with all that said, I do believe that what Congalou has made will stand the test of time and use; not withstanding the holes in the wood.

Good Vibrations,
Blavonski

[jorge]

Blavonsky, your post has too many mechanical conceptual errors to attempt to correct point by point. Your terminology suggests you have some knowledge of static mechanics. If so, try drawing a freebody diagram of the lever with the fulcrum at the top bolt, and then with the fulcrum at the bottom bolts and you will see the tension and compression I am referring to. There is actually no single point fulcrum, but that will give you a qualitative idea of the lever effect.
There is no contradiction in my statement about the shear forces not being much different between the two configurations. In this situation, the shear stress is not the tension and compression acting together, the main shear force vector is parallel to the drum shell surface, whereas the main force vectors for the tension and compression are perpendicular to the drum shell surface, so they are basically orthogonal and don't interact.

[blavonski]

Blavonsky, your post has too many mechanical conceptual errors to attempt to correct point by point. Your terminology suggests you have some knowledge of static mechanics. If so, try drawing a freebody diagram of the lever with the fulcrum at the top bolt, and then with the fulcrum at the bottom bolts and you will see the tension and compression I am referring to. There is actually no single point fulcrum, but that will give you a qualitative idea of the lever effect.
There is no contradiction in my statement about the shear forces not being much different between the two configurations. In this situation, the shear stress is not the tension and compression acting together, the main shear force vector is parallel to the drum shell surface, whereas the main force vectors for the tension and compression are perpendicular to the drum shell surface, so they are basically orthogonal and don't interact.

Hey Jorge,
just so you know, this discusion is fun for me...no stress...

What errors are you refering to? I admit, I did mistakenly refer to the nipple as a lever, which like the plate, it is not. It acts more like a wedge. The knowledge that you glean from my termanology simply comes from close to 20 years of working with architects and engineers as a Designer, Welder and carpenter/woodworker working with various materials from steel to ceramic. So, I attempt to share my ideas and interpretation of structures and materials as well as my arguments regarding the mecahnics of them as I have come to understand them.
I'm just a layman.

The contradiction in your statement,"Regarding the shear forces, it makes no difference if the two bolts are on bottom or top, but regarding the tension forces, Congalou's proposed configuration should be superior to the two bolt on top design.", as I interpret it, is that; If Shear stress, as I understand it, is simply Tension and Compression acting together at +45°, then the tension tress plays an integral role in creating the shear force on those bolts; one bolt at a time for each hole. So, that would mean that in any position they are under equal stress caused by tension and compression which = shear. Practically everything that breaks, collapses or falls apart does so from the material shearing due to compression and tension stresses combined. But, it's not on the surface that we notice it, it's an internal molecular reaction that when it as gone far enough reveals itself in a crack or tear on the surface. Then when there's nothing left to shear it comes apart.
Also, to what I wrote yesterday regarding Congalous' plate width and the what I percieve as possible effects on the wood; I would add that, due to his plate being as thick and narrow as it is, it is also very stiff. That can be good, but it can also be a problem, because there's little plate mass to take up some of the tension stresses, therefore all those load stress will go to the bolts/wood and the nipple.

"There is actually no single point fulcrum, but that will give you a qualitative idea of the lever effect."
I have to disagree with you there. Because, as I understand it, the tension stress caused by the compression of the lug nut as it turns and tightens/pulls the lug and top hoop down is tranferred to the Nipple (wedge) to support it. Therefore, there is a single fulcrum point and it is the Lug/nut/ nipple junction. And this junction point or Moment as it is technically refered to creates, as I stated before, the strain concentration point at the nipple; Hence, the fulcrum is at the threaded, nut end of the lug bearing on the Nipple. (All this talk about nipples is making thirsty )

At any rate, the Lug nut turns around the axis of the lug by use of a wrench,(lever), like, for example: If I want to cut a circumfrence from a sheet of plywood with a Router. The router will be attached to a rod/lever at one end, while the other rod/lever end is fastened with a screw in a hole in the plywood that acts as a wedge support in the center of the that circumfrance, which becomes the fulcrum around which the lever and router turns as it cuts.

"... the main shear force vector is parallel to the drum shell surface, whereas the main force vectors for the tension and compression are perpendicular to the drum shell surface, so they are basically orthogonal and don't interact."[/i]

Not quite sure what you're trying to communicate here. But, all forces, Compression and Tension, work together and particularly in this configuration due to it consisting of two ends of a structure being tied and fastened to one or both ends to pull and hold something together with force. As I understand it, the main force vector to which you refer is the Lug that is fastened at the top hoop ring and threaded, Lug nut end and it, (the Lug), is parallel to the drum. The plate is also parallel to the drum. The only thing perpendicular to the drum are the bolts and the nipple, and it is the main strain concentration point here and thus, it is subject to both Tension and Compression forces that = Shear. Now if the Nipple should lose its elasticity and not do its job, then I think the plate bolts will be under excessive force, which will be transferred to the edges of the holes in the wood. But, as I mentioned before, I think the Lugs will begin to strip before the nipple/plate loses ground.

Ok, til next time good vibrations,
Blavonski

[congalou]

Better photos, plate before finish.

Galou.

[congalou]

I think I will make a pair with kind of "satin finish hardware", I have try today, here is some photos.
G.

[congalou]

New photos : the shell I will use with theses plates (Ash and fiberglass outside), hardware (rust and varnish) and a try of gloss finish for the plates.

[Mike]

The design is really outstanding and aesthetically pleasing.
And I see you also have got WD-40 as a little helper