this is a magnesium bike frame magnesium
is a fantastic metal and a criminally
underrated material for making bike
frames but what are its advantages over
aluminium titanium steel and carbon
fiber well in this video that's exactly
what i'm going to tell you it's time
for some science
vast are one of the few manufacturers of
magnesium frames and have agreed to
support this video but don't worry the
points we discuss are based on
scientific fact and seriously
interesting and just to be clear when we
say magnesium it's really just shorthand
for magnesium alloys
reason one magnesium is seriously
lightweight it's the lightest usable
metal so it's lighter than aluminium and
titanium and this is because it's less
dense it's 59
less dense than titanium and 32 less
dense than aluminium
i say lightest usable metal because
there are metals lighter than magnesium
as we move out of the corner of the
periodic table the elements get heavier
so right in the corner you've got
hydrogen very light it's not a metal and
then you have the metals lithium and
sodium these are lighter than aluminium
but they're way more reactive and
they're also very soft to show how
reactive they are here
is some sodium which i definitely didn't
steal from the university of manchester
chemistry department
just to be clear
sodium is very soft you can cut it with
a knife and here's what happens when you
put it in water
it sets on fire
don't try this at home
we also have beryllium above magnesium
but you wouldn't want to make a bite
frame from that or put it on your chips
because it's fantastically poisonous so
next we have magnesium with its atomic
weight of 24. now magnesium 2 is pretty
reactive but it's nowhere near as
reactive as sodium but wait a sec i've
heard of magnesium that stuff can burn
in air it's flammable yeah you might
have seen that experiment in school but
the key thing with that is that was
magnesium ribbon or magnesium powder
magnesium powder and ribbon does burn at
600 degrees c and that's why it's used
in sparklers
the key take home message here is it's
all about surface area magnesium ribbon
and magnesium powder has a high surface
area it's much harder to set a light a
big log of the stuff or the tube of a
bike frame which has a very low surface
area
and to make that point here is a
kilogram of magnesium in the form of a
bike frame which i'm now going to try
and set a light
risking my life
for everyone
[Music]
it's just turning black with soot
it's pretty disappointing
now it's just turning black soot
never mind
[Music]
next it's environmentally friendly
carbon fiber has a dirty secret it's
terrible for the environment the process
of making it involves a lot of steps and
a lot of chemicals some of which aren't
very nice and once it's been made it
can't be recycled magnesium on the other
hand is much better for the polar bears
being 100 percent recyclable
but what about all the other alloys they
can be melted down and recycled too
what's so special about magnesium well
you're right they can but magnesium's
melting point is just 650 degrees which
means it requires much less energy to
melt it down and recycle it which is
again good for the environment if you
say compare it to titanium which has a
melting point of
1670 degrees
polar bears are going to be rejoicing
yes carbon fiber is lighter being 30
less dense than magnesium it also has a
higher tensile strength but it's less
resistant to impacts
than alloys like magnesium
carbon fiber is more brittle and more
likely to crack in the event of an
impact yes it can be repaired but
magnesium is much less likely to do this
unless you're riding in cryogenic
temperatures or
the arctic with them with polar bears
which which there's probably going to be
more of because you're you're riding a
more environmentally friendly bike
this durability means that your
magnesium frame might scratch dent or
pick up scars but it will still probably
be ridable and
we all know scars are cool if you're
going to be going on adventures or
encountering rough terrain alloy frames
not just magnesium make a lot of sense i
mean
i would not dare do that to a carbon
frame
[Music]
but wait magnesium corrodes
what about that well you're right
magnesium does corrode that's partly
down to the fact that it is a pretty
reactive metal as i mentioned at the
start however that's why you don't ride
a bare magnesium frame like this but
instead
you use one that's been surface coated
inside and out like this and then
painted
probably like that one
this is a special ceramic oxide coating
applied using a technique known as
plasma electrolytic oxidation this
surface hardens the outer surface of the
material and provides a significant
barrier against oxidation
if you scratch the frame through to the
base metal that will open up a gap or a
slight fissure whereby corrosion can
then ingress and take place but this is
much the same as an aluminium frame or a
steel frame however according to vast if
you do to scuff the paint you're
unlikely to go all the way through and
take off this ceramic coating layer
because it is so hard in general they
would just advise that you treat it like
any other alloy frame
and while we're on the subject of
destroying your bike if the worst does
happen cost is another advantage
it's a bit more expensive than aluminium
but it's way less expensive than carbon
fiber and significantly cheaper than
titanium and part of the reason for this
is because
it's everywhere it's the eighth most
common element in the earth's crust and
the c is full of it so get this one
cubic meter of sea water is said to
contain 1.4 kilograms of magnesium which
is more than that
mental
also bonus fact for you all life on
earth depends on magnesium because
magnesium atoms are found at the core of
chlorophyll chlorophyll is a complex
molecule found in all plants that's
responsible for photosynthesis
this plant isn't real but if it was it
would have chloroform in it
and magnesium
magnesium is also much cheaper to
extract from the natural environment
than titanium now yes a carbon frame is
lighter and stiffer but with a magnesium
frame you're essentially getting 90 of
the performance for 50 of the price and
the money saved well
that can be spent on whatever you like
that's one of the freedoms that's
afforded to you however i i would
suggest that you perhaps spend it on a
ticket to the global bike festival on
the 16th of june which is happening in
salbac which also happens to be a region
that is very high in in dolomite the uh
the natural ore that magnesium comes
from
next it's much easier to precision
engineer with alloy frames it's well
much better suited to machining and
precision engineering especially areas
such as the bottom bracket of course
there is a caveat to this it will depend
on the exact type of bottom bracket
standard that is employed in a given
frame but the advantage of having a
single piece of alloy which you can then
accurately machine on both sides means
that you can much more easily achieve
perfect alignment of your bottom bracket
on both sides of the frame which results
in a perfectly smooth spinning chain set
this can be achieved on carbon frames
but it's much harder to do so and much
more costly
why does magnesium have these amazing
properties well
it's time for some chemistry inorganic
chemistry to be precise strap yourselves
in and don't worry because i'm going to
explain this in a way that even
non-chemists can understand on an atomic
level metals are crystalline and a lot
of their properties depend on the
structure and shape of these crystals
now magnesium and titanium form a
special crystal known as a hexagonal
close-packed lattice this is different
from the crystal structure found in say
aluminium
or iron and steel and has some key
advantages
the hexagonal lattice of magnesium also
has another key advantage
vibration dampening now to a material
scientist vibration dampening is all
about what's known as the young's
modulus which is the modulus of
elasticity
the lower the young's modulus the more
readily the material deforms
vast uses a special alloy of magnesium
in its frames called
ae81 which has a young's modulus of 44
gigapascals in comparison aluminium 6061
has a young's modulus of 69 titanium 114
and reynolds 953 steel 207 according to
vast this shows that ae81 magnesium will
deform more readily during elastic
deformation and will consequently
dissipate vibrational energy rather than
transferring it through the frame to the
rider
so in non-nerd speak
basically means it's more compliant than
other alloys but this can have a
disadvantage meaning that it's softer
and more flexible but that is why you
don't use pure magnesium to make a bike
frame this is where alloys come in so
there you have it a big bunch of reasons
why magnesium is a seriously underrated
material for making bikes thanks to vast
for supporting this video also cool
detail the bottom of the down tube on
the vast bike it's got a recycling
symbol which i think is pretty nice and
also don't know any of the bikes that
have that on now if you've enjoyed it
you know what to do if you found it
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the next one i'm gonna go now love you
bye