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The double sides pads do introduce mirror vibration so the pucker mesh pars are the best and do not use superglue or Araldite unless you want to replace the screen. Either they crack during the hardening process or you return to the car a few days later and the screen is well busted. Regards Peter
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Apprantly araldite is ok - that is if you're willing to hold it in place until cures.
www.honestjohn.co.uk/forum/post/index.htm?v=e&t=28...0
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Not So, Araldite is not flexible enough and the coeficient of expansion is not that of glass so placed great strain on the glass and suddenly crack it's busted one guy busted his screen using the rapid version due to apparently thermal shock. Regards Peter
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You are more likely to cause a problem if you stick the mirror back on during a cold winter's day. The reason is that the metal will expand, and place the glas under tension for the remainder of the year.
Glass does fail at lower stress when that stress is applied for a long period of time, and that stress must be tensile, not compressive. So, putting the mirror on in Summer is fine, because for most of the time, the glass will be under compression - which is safe.
The co-efficient of expansion of the glue itself is only a secondary issue. The fundamental CTE mismatch is that between the glass and the metal, which are also by a large margin the stiffest materials in the joint - hence these are the materials which attract the highest stresses. The best way to avoid these thermal stresses is to make sure sufficient thickness of adhesive is used between glass and metal - the use of a fine mesh to ensure a minimum joint thickness is thus recommended. I would aim for a bond line thickness of 0.3 - 0.4 mm.
Some typical figures from a joint design I have been working on are included below.
CTE steel - 16 microns per metre per degree C
CTE glass - 2 microns per metre per degree C
CTE epoxy - 100 microns per metre per degree C
Young's modulus steel - 210 GPa
Young's modulus glass - 90 GPa
Young's modulus epoxy - 5 GPa
As a first approximation, the glass doesn't move much under a change of temperature, but the steel does. Although the CTE of the epoxy is much larger, the epoxy is also much less stiff, so, it cannot easily apply stress to the glass or steel itself. The steel is stiff, and this is dominant means of stressing the glass. Another way of saying this is that at a boundary, the strain must be the same in each material, and so, the resulting stress is proportional to the elastic modulus in that material.
Number_Cruncher
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Need to use special type of glue that dries with Ultraviolet light (ie sunlight). One can buy it from B ana Q etc. I think it is called glass bond. Had same prob with Cavalier after windscreen replacement. This is what dealers use. Will break off with impact (with your head) as you would want in an accident.
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will try that AM thanks
i pay £3.50 a shot at my motor factors for window glue at the mo in a one shot application and a bit of fuzzy material to goes between glass and mirror (expensive i think)
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Got to be the Ford dealer then!!!
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Number_Cruncher
That's fascinating stuff that I don't really need to know. All the mirrors I've ever had have been on metal stalks screwed to the top, or bottom, of the windscreen frame. They never fall off.
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Not So, Araldite is not flexible enough ....
Not according to AR-CoolC, who just so happens to know a thing or two about windscreens.
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I'll be approaching my local ford dealer this weekend, i'll let you all know what happens. Thanks for your help guys:-).
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Its not what you drive, its how you drive it! :-)
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I'll be approaching my local ford dealer this weekend
guns ready? ;-)
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Brought a sticker pad from the main dealer this morning, it works a dream (so far) thanks everyone for your help & wish you a happy & prosperous new year!!
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Its not what you drive, its how you drive it! :-)
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Damn thing has fallen off again!!! :(
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Its not what you drive, its how you drive it! :-)
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Windscreen fitters, speak to lads in workshop & beer tokens, job done.
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Did you clean off the old one completely with white spirit or meths? I've not had mine come off yet after making sure both surfaces were squeeky clean and dry.
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Mike Farrow
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I agree with Mike. Cleanliness of both surfaces is vital or the sticky pad fails within hours.
White spirit, meths or lighter fuel (petrol) works well.
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Get both surfaces completely clean and dry. In this weather add a bit of heat, not a lot, just a wave over with a hair drier.
Tip of the week: put a drop of oil in the ball and socket part of the mirror, this takes the strain away from the sticky pad when adjusting the mirror.
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I'm still trying to work out why manufacturers don't simply screw the mirror to the car's roof, as Nissan (used to?) do.
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why manufacturers don't simply screw the mirror to the car's roof...
Safety reasons. In the event of an accident the mirror is designed to come away from the windscreen. Can't do that so easily if screwed in place.
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White spirit leaves deposits, use meths, isopropal alcohol or cellulose thinners. Regards Peter
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