American Motorcycle Dealer AMD 230 September 2018 | Page 55

TECH EXTRA
DOT BRAKE HOSE AND BRAKE
LINE ASSEMBLY TESTING
Part 2 - The Torture Tests
Scott Hurwitz, founder and CEO of Pittsford, New York based
Magnum Shielding, continues his two-part series examining the
very particular challenges of the motorcycle brake hose business.
s mentioned in the last article,
Motorcycle Brake Lines Part 1,
published in the June edition of
AMD Magazine, brake hoses
and brake line assemblies are
among the most regulated components on
a motor vehicle and all manufacturers of
brake line assemblies for highway use
must be registered with the Department
of Transportation (DOT).
In addition, these brake hoses, fittings and
assemblies must conform to FMVSS-106 and SAE
J1401 standards, both of which outline grueling
and demanding tests, which are designed to
exceed what a vehicle will actually experience in
the real world. This intentional overcompensation
is necessary to protect us considering real life
variables in manufacturing, installations and
usage.
This standard ensures that brake hoses stay flexible
in a wide range of temperatures while having a
predictable expansion rate, so that the pedal feel
and ABS response is the same in winter as it is in
the summer. It also requires that the hoses are able
to bend and twist at certain angles without
fatiguing, collapsing, kinking or bursting and that
the critical crimp joint, where the hose is
permanently connected to the end fitting, is robust
enough to withstand all mechanical, chemical and
temperature influences.
Let’s now talk about the testing itself. It is no
surprise that the sophistication of the testing
equipment usually requires that manufacturers
send brake hose assemblies out to third party
testing labs for DOT validation, along with formal
supporting documentation. This can be very costly
- in excess of $20,000 each time a complete
validation is conducted.
As a Tier-1 Supplier to Harley-Davidson P&A,
Magnum Shielding takes rider safety very seriously
and has placed this at the top of its priorities. Our
brake line manufacturing expertise, process and
quality controls ensure brake line compliance with
all DOT requirements, i.e. NHTSA’s FMVSS-106
Compliance Standards.
To support this initiative, Magnum Shielding has
duplicated the majority of the equipment needed
to conduct the tests described below at their
Upstate New York facility in accordance with the
TP-106-10, U.S. Department of Transportation
National Highway Traffic Safety Administration
Laboratory Test Procedures for FMVSS-106 Brake
Hoses. Per Magnum’s Quality Management
System, all brake hoses and assemblies are tested
on an ongoing basis to guarantee both compliance
and consistent product quality.
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www.AMDchampionship.com
Reviewing the entire standard can be quite time-
consuming, so it has been distilled down for the
sake of this article - let’s get started.
Volumetric
Expansion
FMVSS-106
Standard Tests
Labeling
Depending on whether the hose assembly is OEM
or NON-OEM (aftermarket), there is more than
one alternative for labeling compliance. The
Standard requires a visual inspection of the hose
and/or fittings for proper labeling requirements as
previously discussed in Part 1.
Constriction
This is a "go" or "no go" test where a drop ball,
such as a metal ball bearing, is inserted in the
upper end of a vertically held hose assembly and
expected to drop down by gravity through the
hose and out of the other end fitting. For 1/8”
I.D. brake hose, the size of this sphere is .079”.
This is an important test to ensure that the end
fittings are not over-crimped and that there are
no other possible blockages in the assembly that
might be created as a result of the manufacturer’s
assembly process.
Volumetric Expansion
This is a test of the true strength of the brake
hose’s construction. The lower the brake hose’s
volumetric expansion, the better the braking
response (and feel) will be. On very long OE
routing applications, sections of the assembly
have metal tubing incorporated to reduce this
expansion. This is one of the reasons braided
brake lines are preferred over rubber hoses,
whether they be braided with stainless steel or
better yet, high tensile aramid fiber, which is
sometimes referred to by DuPont’s trademarked
name, Kevlar.
In both scenarios, the hose’s expansion rate is
directly related to the tensile and elongation
characteristics of the braided materials used,
along with the specific construction of the braid.
Braid construction is also controlled by the gauge
and number of wires or strands used, along with
the tightness of the weave. The Standard states
that the maximum expansion of a low expansion
(LE) hydraulic brake hose assembly shall not
exceed the values specified in its referenced “LE”
table at three particular pressures, 1,000 psig,
1,500 psig and 2,900 psig.
The fixture which tests for this requirement
pressurizes an isolated brake hose that has an
upper valve connected to a graduated glass
cylinder. Prior to the hose being pressurized, the
level in the graduated cylinder is set to zero. After
pressurizing the hose, the valve is opened and the
fluid level is allowed to rise into the cylinder,
which then measures the amount the hose
expanded at that pressure level. Testing for hose
expansion rates can be especially important given
the combination of today’s sensitive computerized
ABS controller modules with aftermarket extended
length brake lines required for tall “Ape hanger”
handlebars. If the brake line construction exhibits
high expansion levels, the readings may be outside
the controller’s functional range to actuate the
ABS as originally intended and programmed.
Tensile Strength
This test consists of subjecting the hose assembly
to a gradually increasing tensile load at two
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