Chainmail
Motorcycle Jacket
chain maille
motorbike shirt
Updated
03/Oct/2008 erm…
only 5% of the way there!
I’ve
been making chainmail on and off for several years now. Mostly from spring
steel lock washers, although a few projects from mandrel wound wire. I favour spring
washers because they’re cheap, strong and have a clean cut.
I’ve
also been riding motorcycles for about 9 years and a few years ago I had the
idea of making a chainmail jacket. Well it stayed an idea and progressed no
further; no point in committing to new projects when I hadn’t even finished my
hauberk after 5 years. Then in time for my 30th birthday I pushed
ahead and finished the hauberk. The armpits were a bloody struggle, especially
with the low aspect ratio of the washers. I’m really pleased with it. 20,000 M8
rounded-square-section spring washers and ~20kg! God knows how many hours,
perhaps 200? I then gave up chainmail!
(The pot-helm was simple in comparison. Made of 2mm mild steel sheet,
took about 16 hours)
Spring
washers aren’t that authentic if you want to do re-enactment, but for me it’s
the making and creation that’re fun. And they’re super-strong
& cheap!
As
I’m going away around
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Japanese 4-2 (Hitoye-Gusari) |
Japanese 6-2 (Hana-Gusari)
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Top images from http://artofchainmail.com/
Trawling the internet for information revealed
very little other than a few suppositional opinions until I came across an
article on mailleartisans.org posted by Jason
http://mailleartisans.org/articles/articledisplay.cgi?key=9612
He’d
apparently hit a deer on his bike at a fair whack while wearing a European 4-1
vest with 8mm rings. His arms and legs were ground into the tarmac but his
torso ‘merely’ pummled. Certainly no worse than a sleeveless leather jacket. Although my mum has forbidden
such a venture this is all the encouragement I needed. Having read various
discussion threads I’ve adapted my design to hopefully address all the possible
issues. This is a work in progress and I estimate it will take ~90 hours.
Chainmail
Motor Cycle Jacket
Material: zinc plated spring steel washers M12 and
M6
Pros: cheap (M12@£12.14/1000
and M6@£2.99/1000
www.screwfix.com)
Clean
cut and super-strong spring steel for butted mail. The M6 washers deform (pull
test) enough to let an M12 ring slip through at ~40kgs. I’m not strong enough
to pull the M12s apart but guesstimate ~160kgs from the cross section (they are
effing strong!).
Cons: fairly heavy*. Estimating about 10-12kgs
for the shirt (heavier than I initially hoped it would be.) ~4800 M12s and
~14400 M6s.
* turns out extra mass is necessary to absorb heat energy and
reduce temperature rise.
Design: I just started making sheet! Plan is to
draw the panel sizes from my leather jacket onto card and make maille panels to fit, and then join it all together.
Worries:
- M6s
protrude vertically and could dig-in in a crash.
It hurts more than European 4-1 if I stamp on a sample of the material with my heel!
Solution: 1) wear my armour jacket underneath (nylon thing
with pads)
2) double up the M6s on the elbows and shoulders
to give more surface area at impact points.
- Removal
of jacket by ambulance crew.
Solution: I was going to make a 1 piece jacket with luggage straps to pull it tight, but now I plan to use several luggage straps as buckles up the front and have some overlap. This will allow for extra jumper or me getting fatter!
Better to thread the straps around the inside of the jacket to
stop them snagging in the event of a slide [pointed out by Mogg
(John Morgan Rook)]
- Rain.
Solution: carry a waterproof jacket
- Baggy
arms.
Solution: try to figure a way to taper Japanese 6-2! Maybe use M10 and then M8 rings near the wrist or knit a long triangle for the arm and join the two long edges. Add a couple of luggage straps as necessary to pull things tight.
- Zinc
on skin.
Solution: wear a long sleeve t-shirt underneath.
- Attracting
too much attention.
Solution: sweatshirt over the top.
- Material
tearing.
Solution: Maths! A lot of people on threads were worrying about the mail tearing and coming to pieces. That may be more of a problem with mild steel wire. I decided to try and compare the strength of the washers to my leather jacket. Here is my back-of-the-envelope scientific consideration of the problem (feel free to point out problems phillipdj@yahoo.co.uk)
Tensile
strength leather: 2000-6000 lb/inch2 I opted for 4000 lb/inch2 as
jacket leather is much softer than boot sole leather and it’s in the middle!
So that’s Leather 2.9 kg/mm2
Tensile
strength ring: I decided to test this for myself. Using a 50kg spring gauge, 
,
the M6 ring deformed enough to let an M12 slide through (2mm) at ~40kgs. The M6
ring is handily ~1mm2
So that’s M6
Ring 40 kg/mm2
Now
leather is continuous and the chainmail full of holes so I decided to work out
the strength over a 3 inch (75mm) length. Good bike jackets often quote thick
1.2mm leather. The chainmail had 10 M6 rings in that length. Many of them are
at 60o due to the pattern - I just ignored this in my calculation! J
So:
Leather:
75mm
x 1.2mm x 2.9kg/mm2 = 261 kg
needed to shear a 3” leather strip
Chainmail:
10rings
x 40kg/ring = 400 kg needed to deform a
3” Japanese 6-1 strip
The mail is stronger than
leather.
Leather is considered safe, and Jason’s jacket held with minimal damage
(admittedly a denser weave, but of softer metal).
- Friction Burns: several people (including my mum)
have suggested that the mail will get too hot and burn me. I don’t see why
really. Ignoring the few extra kgs from the
chainmail over a leather jacket, the kinetic energy before impact will be
the same. As one slides to a halt the kinetic energy will be mostly
converted to heat energy. So the leather and chainmail will have to deal
with the same amount of heat energy. Here is my 2nd
back-of-the-envelope scientific consideration of the problem (feel free to
point out problems phillipdj@yahoo.co.uk)
The
amount a material heats up for the energy (Joules, J) put in is called its
specific heat capacity.
Specific Heat Capacity
Leather: 1500 J/kg/oC
Specific Heat Capacity
Steel: 500 J/kg/oC
So
the steel jacket of the same weight (ok, mass) will get 3x hotter than leather for the same energy input. However… my leather jacket seems to
weigh ~3kgs and if the chainmail is
~10-12kgs so that’s 3-4x the mass to soak up the energy, so the temperature rise should be similar, or
1/3 less. Interestingly I had been thinking that welded stainless steel
European 4-1 would be a lightweight and strong (and hideously expensive)
solution, but maybe you need the mass to soak up the heat. The maille needs to be made of HeavY MetaL!
There may be heat build up in certain areas
like the shoulders as they dig in to the floor, but this would happen with a
leather jacket too. By doubling up the M6s on these areas for extra strength
and to stop them digging in to me, there will also be extra mass to soak up the
heat energy and reduce any temperature rise. Also the armour jacket (made of
some really dense 10mm foam) should be a good thermal insulator.
- Strong
Buckles: Ideally I
want the jacket to be cheap, not too stupid looking, durable and
adjustable. I think luggage straps may provide the solution. Although the
cast metal material the buckle bit is made of will be weaker than the
chainmail, 6 or so of them must be stronger than a zip? The buckles will
be clipped to the chainmail on one side and the 1” nylon strapping
threaded through the mail around to the other side. This will leave straps
that can be pulled to the desired tightness.
Weaving Tips: get a vice, then
you can feed the pliers with one hand and twist with the other. Vice can be adjusted
to suit various ring sizes. Spring washers are tough and need fresh pliers.
Close the M12s and work with open M6s. Although there are 3 times as many M6s,
they are so much easier to work
with. Make a chain of 100 M12s (and 98 M6s) and then build a
