Asymmetric Angles on Clamp-Band Flanges

[Treetoedsloth]

Hi,

I have some drawings for two flanges meant to be held together by a Marman clamp-band, and the drawings specify that one flange should be a different angle than another, e.g. one flange is at 16 degrees while the other is at 10, instead of both flanges being 16. Does anyone know why this is done? It seems like the clamp band would end up applying more force to one flange than the other.

I am asking because I need to design a very similar band and flange, and not sure whether I should follow these dimensions or make my flanges symmetrical angles.

If anyone out there has experience and knows why this would be done, it would be great to find that out! Bonus points for references/sources. Thank you!

 

[monkeydog]

Check with the supplier you are using, Aeroquip, Voss, Eaton etc.
They are also called v-band clamps. I have not seen flanges specified asymmetrically.
The clamp manufacturer will specify the flange design you need.

 

[Compositepro]

Regardless of the angles, the clamping force on the two flanges is always equal.

The possible reasons for assymetry are:
Proprietary design to be sole source.
Make it so the band can only be installed in one orientation, rather than two.
To adapt two different proprietary flanges together.

 

[IRstuff]

Seems to me to be a bad idea; the band could accidentally be installed backwards, possibly reducing the "true" clamping force because the clamp is compressing correctly.

Additionally, there might be a temptation to use similarly sized clamp if the purpose-built one was damaged or lost, also resulting in possibly a different clamping force than intended

TTFN (ta ta for now)
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[Treetoedsloth]

Proprietary design to be sole source.
Make it so the band can only be installed in one orientation, rather than two.
To adapt two different proprietary flanges together.

Thanks composite! that makes sense

 

[Sparweb]

Just curious, since this is a forum for spacecraft...
I once saw drawings of a v-band clamp used as part of a payload jettison mechanism.
Is the band clamp you are looking at secured with an "explosive bolt" or more generally a pyro fastener for jettisoning?
You're probably talking about a fluid line coupling, so this is probably a moot point...

 

[Treetoedsloth]

I once saw drawings of a v-band clamp used as part of a payload jettison mechanism.
Is the band clamp you are looking at secured with an "explosive bolt" or more generally a pyro fastener for jettisoning?

Actually yes, that's what it is for. Potentially using some kind of frangible nut or bolt, here are two similar examples below

 

[Sparweb]

Oh, OK then. It wasn't my imagination.
In that case, many details of the means of separation, such as freedom of movement and retention of the parts that are not being dropped, etc. are factors critical to the assurance of a successful jettison.

I remember reading a paper about launch failures in a number of historical cases - not so much about the dramatic explosions but the mundane failures to properly deploy the payload that led to mission failure. Galileo not opening its high-gain antenna, for example. And the Gemini Agena crocodile. If you're too young to remember these missions you can google them. Anyway, the paper may have had some references to mechanisms for jettisoning boosters and fairings from satellite payloads, noting cases where certain pieces failed. Maybe I saw it in the same place as the drawing (fuzzy memory, still). It opened my eyes to the number of ways people say "Space is hard" and that an agency like NASA has to be very creative, even about common things like hardware, when driven by a reliability requirement with no second chances to count on.