suction mounting failure

[w0krb]

Any idea of how to renew the suction mounting so it will stay on the special disc - Unit falls off - sets off car alarm and last time it cut the power cable as it fell

 

[Andy_P]

Spit on it?
Clean it with detergent?

Where did you get the disk from? Is it completely flat?

 

[w0krb]

renew mount

I used alcohol pads, windex, and it still falls off. The disc is the one tht comes with the unit and it is mounted to the dashboard per instructions. Unit will stay on for 8-10 hours and then at random times will come loose and fall off.

 

[Andy_P]

Must be different in different countries..... I've never seen a TomTom supplied with a dashboard disk in the box in the UK.
Maybe because one or two states have banned obstructions on the windscreen?

 

[dhn]

Not even on your 720, Andy?

 

[Andy_P]

Nope, just came with this simple windscreen mount.

 

[stumper]

problem with mount

I,too,am having the same problem with my mount. I clean both surfaces, mount and sticky mount surface. But a strange twist, when it falls off I find the the mounting knob in the unlocked position even though I had turned it until the click when I mounted it, Any ideas here ???

 

[Andy_P]

Vibration may cause it to "unclick"? Do you drive a car that rattles as much as mine?

 

[stumper]

I think I found a solution ti this problem. Chew a piece pf gum before licking the suction cup .Mine has been on for over a week. Used to fail overnight. :blabla: :thumb:

 

[stumper]

Vibration may cause it to "unclick"? Do you drive a car that rattles as much as mine?

It is in a pickup truck.....ya probably there is some vibration but it was falling off at night when I was not driving it.......I think the gum was the fix...............

 

[Steve83]

These captions describe how I fixed this problem:

.

 

[alfie67]

Nicely done, Steve83! Very much appreciate you sharing that info - hope that others with similar problems have a go at trying your solution!

 

[canderson]

Then there's the situations where the ring locks, but the silly thing still won't stay in place. Removing and replacing a suction mounted device all the time isn't a good idea for several reasons, but I was explaining one of the more obvious winter issues to my wife at dinner last night: Boyle's Law.

Suction devices operate on a differential in pressure between the outside air pressure and that created under the cup. At this time of year, many users will be attaching their devices in the morning when it's ice cold, and over the course of their commute/whatever, what air remains under the cup will warm up.

Boyle's Law: PV = nRT

You can ignore "n", and just understand that R is the amount of air under the cup, which stays more or less constant (until it falls off!). Here's the real rub, then:

PV = T

P = pressure
V = volume
T = temperature

Raise the temperature of the air inside the cup as your car warms up, and look at the other side of the equation. Ooops. While the cup and the device that deforms the cup tries to hold the volume constant, the pressure goes up .. and up .. and finally is too close to the ambient for the difference to hold the device's weight, and plop.

 

[Andy_P]

These captions describe how I fixed this problem:

I'm guessing "BB" = ball bearings, yes? (not "BB gun" pellets!)

 

[- et -]

These captions describe how I fixed this problem:

I'm guessing "BB" = ball bearings, yes? (not "BB gun" pellets!)

I don't see why it could not be "BB gun" pellets - in this particular application.

In some ways they might even be a better choice than ball bearings - you could save a penny or so on cost. :thumb:

Seriously - a BB pellet would not have the tightly controlled dimensions and better surface finish of a ball bearing, but I don't think those would be needed in this case. I see no reason why a functional latch of this design could not work adequately using BB pellets. Done properly, it would work even better using ball bearings, but there is an old saying among engineers - "Better is the enemy of good enough."

With best wishes,
- Tom -