Page last updated 13 July, 2007
Ever wondered about trade "secrets" in garages? Well, some are true, some are made up, so this section may be of use to many of you. Also covered are general points to watch when working on cars - there are some nasty hazards!
Hydrofluoric
Acid & Flouroelastomer, and used engine oils
Rubbers
used for seals and gaskets in cars very often are made of fluoroelastomers
- a very versatile and tough material for any situation where a gas/oil/fluid/air
tight seal is required. However, under certain conditions, this can become
hazardous as it changes into hydrofluoric acid. This occurs in temperatures
of 316ºC or higher, but especially over 400ºC. Water or water vapour
has to also be present for the heated seal to change into this dangerous acid,
but if it occurs amputation is the only answer to prevent it spreading in
the event of skin contamination.
So, those latex
gloves you see worn in garages aren't just to keep the technicians' hands
nice & soft, they are also to protect against this type of hazard. Wear
them at all times when working on your car's mechanicals, and these will also
prevent oil/grease soaking into your skin. Used engine oil is a carcinogen,
and therefore another very good reason to wear gloves.
Contact lenses and MIG/TIG/ARC welding may cause blindness
It has been reported
that wearing contact lenses while welding or even being near a welder, may
carry the risk of blindness if the person is wearing contact lenses. Apparently
the lenses can fuse to the front of the eyeball under certain conditions,
when in close proximity to an electric field such as a welder. Removal of
the lenses after this has occurred has been reported to also remove the front
of the cornea. Whether this is true or not, it's adviseable to wear glasses
instead.
Soft metal
can wear out harder metal
Believe it or not, but when a soft metal (eg an alloy) is in contact with
a harder metal (eg steel), in many circumstances the hard metal will actually
wear out more than the soft metal. I found this out when I overused a small
compressor once, and heard the big ends starting to knock. Upon stripping
down the pump I found that the alloy connecting rod was in an almost serviceable
condition, but the crankshaft had 2x 3mm deep grooves worn into the bearing
journal. I'll never forget that time as the cheap compressors nowadays have
no changeable bearing, but instead rely on the alloy con. rod material and
also the oil to provide a low friction surface against the crankshaft. Metal
particles also would have played their part - especially after the wear process
had begun, but I could not believe the good condition of the con. rod. I showed
an engineer friend and he confirmed this strange wear by saying "of course
- don't you know soft wears hard?"!!!
This may explain
also why steel hinge pins wear out, yet the alloy hinges are fine - a simple
pin renewal makes them work fine again.
Strange Tyre Wear Patterns
Not usual with TVRs but a small possibilty....but the rear tyres sometimes
can wear in a diagonal pattern to such an extent that the tyre can have perhaps
5-6mm of tread in some places, whilst wearing down to the banding in other
places. I have seen this occur on some Renaults & Peugeots, and have yet
to work out exactly why this occurs. Tyres wore like this from new, wheels
were perfectly balanced, shock absorbers in good condition, wheel geometry
checked & correct. So far the most likely cause is tyre construction -
as the problem seemed to happen on certain types of tyre. However, if anyone
out there has experienced this problem it would be good to hear from you so
maybe a link could be found to pinpoint the problem. Clues also lead me towards
torsion bar rear suspension, as that is the type I have found it to occur
on so far. Perhaps it's the way the rear axle acts with each side - they are
joined by solid frame and it's possible there is a resonance over bumps which
cause this "phenomenon"! Thanks in advance for any input.
Mark