Decoding suction mount ratings
 

So I'm spec'ing out a homebuilt suction-based car rig and I'm having some difficulty understanding the different weight ratings. On one hand, Bogen/Avenger makes the F1100 (http://www.bhphotovideo.com/c/produc...with_Baby.html) that is rated on their website at 4.4lbs. Then other vendors, ones I've never heard of, have items that look identical (Visual Departures | Suction Cup Mount - 6" | SM6 | B&H) and are rated an order of magnitude higher around 75lbs. They look like they came off the same assembly line. What's the deal?

Hi Jad.................
 

Unfortunately, there is no "standard" by which suction devices can be measured.

Because of the multitude of different surfaces and attitudes they can be used in, with the different forces they are subject to, giving an accurate figure for their "fail point" is impossible.

As an example: Those 6" suction mounts have, roughly, a suction area of about 29 square inches (piRsquared).

Assuming you could pump all the air out of the mount (a big ask) and thus allowed static air pressure at ground level (about 14 lbs psi) to work, this gives a "pull off" figure of 406 pounds of force.

In reality it would be impossible to remove all the air (ah, but how much is left?), the surface may not be perfectly sealable and thus leak or may be pliable enough to allow the surface to flex outwards under the pressure, thus removing even more "stick".

Given that something reasonably heavy could be attached to this suction mount, and the results (in the States at least) of said heavy object landing on some poor sods head if and when it did fall off, with resultant large legal/ medical fees etc etc etc, you may be able to appreciate why any vendor would give the most conservative figure for support load they could.

My advice is work on the figures I've given above, bearing in mind the surfaces to which you wish to attach them and ensure the "poor sod" situation cannot ever come about by judicious use of passive restraints.


CS

I have been toying along this same line. I came to the conclusion that if it is my expensive camera attached... I will have enough fail safe straps etc that no "poor sod" (I loved that term) or my poor wallet, would suffer.

I think the advice is sound. On an automobile I would wash and wax the area to be used before securing anything valuable to the mount, straps or not.