14 OPINION
Heider
From an offi ce curio, to NASA research, to quantifying feelings, the world
of ride comfort continues to challenge automotive engineers, says John Heider
›A fantastic piece of kit sits on a cabinet in our offices,
but in the 10 years we’ve occupied this space and
entertained countless vehicle dynamics engineers,
exactly one person has admitted to seeing one before and
knowing its origins.
The item in question is a Joltmeter, and the commonly
accepted version of the story is that it was a creation of one
of General Motor’s sales and marketing divisions in the 1930s
as a dealer sales tool to demonstrate the superior ride comfort
of GM products of the day. Consisting of a simple spring and
counterweight geared to a pointer on the dial, when a car
was driven over rough surfaces the device would record and
hold the maximum ‘jolts’ wherever it happened to be placed
in the vehicle.
“Look sir, the all-new 1936 Buick Roadmaster only recorded
35 Jolts over this road!” the salesman would presumably
exclaim to the puzzled potential customer.
What is a Jolt? Who knows… but it is apparently related
to the acceleration experienced by the Joltmeter’s spring/
mass system. Does it relate to the ride comfort of a vehicle?
Well, maybe…
My theory about the origins of the Joltmeter is a little
different. Rather than a sales and marketing person devising
such a measuring tool, I suspect it was a frustrated vehicle
dynamics engineer. English-born Maurice Olley, considered
by many to be the father of modern vehicle dynamics, plied
his trade at GM in the 1930s and experimented with a variety
of ways in which vehicle dynamics performance could be
measured objectively.
VehicleDynamicsInternational.com • November/December 2019
Olley quickly made progress in steering and handling
performance via basic skidpad and straight-line tests, but
ride comfort measurements proved to be more elusive.
Old videos show light sources being placed on the front and
rear axles and body of a vehicle, and long-exposure cameras
tracing the movement of the lights over undulating surfaces.
“But how can we possibly measure higher frequency
events?”, Olley hypothetically quizzed his fellow engineers.
Alas, the Joltmeter was conceived as a means of capturing
the level of discomfort experienced in a vehicle, and it just
so happened to be easy enough for a potential customer to
understand at a dealership. When the sales and marketing
department came calling, Olley’s engineer said, “Do I have
an idea for you…”
The above is equal parts fact and fiction, but one reality
has persevered through the last 80-plus years: objectively
measuring the ride comfort of a vehicle and correlating that
data with passenger’s subjective impressions of ride comfort
is extremely difficult. There are many reasons for this, but
most prominent are the range of frequencies and amplitudes
encompassing a vehicle’s ride performance and how an
individual’s body reacts to those inputs. Other reasons include
how best to objectively measure those inputs, and how those
inputs are described by the person riding in the vehicle.
The desire for exceptional ride comfort will continue to
increase as we transition from driver-oriented to passengeroriented
vehicles. Whether measuring with a Joltmeter or
the latest sensing technologies, how to best quantify ride
comfort will continue to be a challenge.
“What is a Jolt? Who knows…but it is apparently
related to the acceleration experienced by the
Joltmeter’s spring/mass system. Does it relate to the
ride comfort of a vehicle? Well, maybe…”
John Heider spent 21
years at Ford in all
areas of vehicle
dynamics. His most
recent Ford position
was vehicle dynamics
manager responsible
for the development,
launch and warranty
performance of all
North American cars
and crossover vehicles.
He is now co-founder
and principal of Cayman
Dynamics
/VehicleDynamicsInternational.com