"SERVICE AND TECHNOLOGY" MAY 2023

Technical Corner: Can suction cup mounts on a motorhome damage the metal or the bodywork?

Tilt and fixed

Text: Karsten Kaufmann, May 28, 2020

Suction cup mounts allow you to attach almost any accessory to your motorhome: from a Wi-Fi antenna to a towel rack or clothesline, all the way to a small side table. But how does this powerful suction affect the sheet metal or sandwich panels of the body?

Are there any risks of deformation or cracking? "Absolutely not," explains Walter Roth, Managing Director of Sichtschutz-Roth. He has been developing and producing high-quality suction cup holders with an indestructible stainless steel housing for years. "It's not that the vacuum created with the toggle lever generates the actual holding force," Roth adds, referring to basic physical principles.

Once the vacuum is created, there is essentially only minimal pressure between the suction plate and the vehicle wall. The truly strong holding force is then generated by the normal ambient pressure, which presses the suction plate against the vehicle. The strength of this holding force therefore depends on the existing atmospheric pressure; it is greater the higher the difference between atmospheric pressure and the vacuum in the suction plate.

At the same vacuum, the suction cup's holding power is noticeably higher at sea level (ambient pressure 1,013 mbar) than when the camper is parked in the Himalayas at an altitude of over 4,000 meters (606.3 mbar). Therefore, the suction cup doesn't "suck" itself to the vehicle's exterior wall, but is instead pressed against the contact surfaces of the suction cup by the ambient pressure.

Owners of vehicles with vinyl wraps should be particularly aware of this effect. The suction cup mount presses the wrap firmly against the vehicle for the first time, creating a ring around the edge of the mount. However, deformation of the thin sheet metal or the body of a camper van is not a concern – provided the accessories attached are reasonably loaded. The pressure also does not create small cracks in the laminate, as a reader recently feared. The editorial team can also reassure readers on this point.