How would you run a lateral acceleration test in a vehicle on twisty roads at no more than 40mph?

How would you run a lateral acceleration test in a vehicle at slow speeds
from 20mph to 30mph on twisty roads and at no more than 40mph?

The issue is discussed in this repair thread:
o Clare - are smaller car tires easier to balance than SUV tires?
<https://groups.google.com/forum/#!topic/alt.home.repair/So4om4fLtmI>

Where I picked up a free graphical tool for testing acceleration:
o Sensors Multitool, version 1.3.2, by Wered Software
<https://play.google.com/store/apps/details?id=com.wered.sensorsmultitool>

Where there are two types of acceleration graphed
o acceleration
o linear acceleration
<https://i.postimg.cc/7hPhBY5b/accelerate01.jpg>

Where I'm not sure yet how to construct the test experiment:
<https://i.postimg.cc/qqZJjcfZ/accelerate02.jpg>

Since what I want to measure is
o lateral acceleration

Any advice for how best to set up the measurement test?

On 22/6/19 4:56 am, Arlen G. Holder wrote:
> How would you run a lateral acceleration test in a vehicle at slow speeds
> from 20mph to 30mph on twisty roads and at no more than 40mph?
>
> The issue is discussed in this repair thread:
> o Clare - are smaller car tires easier to balance than SUV tires?
> <https://groups.google.com/forum/#!topic/alt.home.repair/So4om4fLtmI>
>
> Where I picked up a free graphical tool for testing acceleration:
> o Sensors Multitool, version 1.3.2, by Wered Software
> <https://play.google.com/store/apps/details?id=com.wered.sensorsmultitool>
>
> Where there are two types of acceleration graphed
> o acceleration
> o linear acceleration
> <https://i.postimg.cc/7hPhBY5b/accelerate01.jpg>
>
> Where I'm not sure yet how to construct the test experiment:
> <https://i.postimg.cc/qqZJjcfZ/accelerate02.jpg>
>
> Since what I want to measure is
> o lateral acceleration
>
> Any advice for how best to set up the measurement test?
>
https://www.academia.edu/people/sear...hicle+dynamics

The above link should get you to this book;

Thomas D. Gillespie-Fundamentals of Vehicle Dynamics
Society of Automotive Engineers Inc (1992)

You can then download the full PDF file and that should help you get
started. I have the hardback copy of that book. The content therein
should get you started in the right direction.



--

Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On Sat, 22 Jun 2019 08:46:20 +1000, Xeno wrote:

> https://www.academia.edu/people/sear...hicle+dynamics
>
> The above link should get you to this book;
>
> Thomas D. Gillespie-Fundamentals of Vehicle Dynamics
> Society of Automotive Engineers Inc (1992)
>
> You can then download the full PDF file and that should help you get
> started. I have the hardback copy of that book. The content therein
> should get you started in the right direction.

Hi Xeno,

Thanks for that starting point, where, as you know, the goal is to figure
out first exactly what is going on, geometrically, with the outside
feathering on long very windy (steering lock to steering lock) turns at
slow speeds.

Clare, as you know, had suggested testing lateral acceleration, where he
was positing that the load on the inside tire, even at slow speeds (less
than 40mph) on the downhill curves, could exceed the load range per tire.

The download worked after I gave it a bogus email and password (8
characters was enforced) where I also had to give it a bogus university and
department and matriculation status.

Blue drawing number #8, on page 20 was particularly instructive in the book
"Basic principles of vehicle dynamics", as was blue drawing #2 on page 16.

On 22/6/19 10:40 am, Arlen G. Holder wrote:
> On Sat, 22 Jun 2019 08:46:20 +1000, Xeno wrote:
>
>> https://www.academia.edu/people/sear...cle+dyna mics
>>
>> The above link should get you to this book;
>>
>> Thomas D. Gillespie-Fundamentals of Vehicle Dynamics
>> Society of Automotive Engineers Inc (1992)
>>
>> You can then download the full PDF file and that should help you get
>> started. I have the hardback copy of that book. The content therein
>> should get you started in the right direction.
>
> Hi Xeno,
>
> Thanks for that starting point, where, as you know, the goal is to figure
> out first exactly what is going on, geometrically, with the outside
> feathering on long very windy (steering lock to steering lock) turns at
> slow speeds.
>
> Clare, as you know, had suggested testing lateral acceleration, where he
> was positing that the load on the inside tire, even at slow speeds (less
> than 40mph) on the downhill curves, could exceed the load range per tire.

Not a hope of it exceeding the load range of the tyre. If that were the
case the tyres couldn't possibly grip at normal highways speeds where
the lateral forces *and* weight transfer really come into play. Any
lateral testing, whether at low speeds or high, will not take into
account the effect of any weight transfer. It can be calculated and this
is, IIRC, given in Fundamentals of Vehicle Dynamics by Gillespie. That
said, at 20-30 mph, weight transfer is negligible in terms of the effect
we are seeing on the tyre shoulder. It is the extra positive camber that
is creating the effect and the longitudinal feathering is the result.
>
> The download worked after I gave it a bogus email and password (8
> characters was enforced) where I also had to give it a bogus university and
> department and matriculation status.

I used the college (www.kangan.edu.au) where I once taught even though I
retired from there 18 years ago. It was happy enough with that. I was in
the automotive department (www.aceauto.com.au). Interestingly, of the 43
teachers in my department - motor mechanics - when I first started there
nearly 40 years ago, only 2 or 3 remain, all others have since retired
or shuffled off the mortal coil.
>
> Blue drawing number #8, on page 20 was particularly instructive in the book
> "Basic principles of vehicle dynamics", as was blue drawing #2 on page 16.
>
Yes, that was the point I was making with regard to tyre contact patch
distortion. Thinking of the page 20 diagram, now imagine what the
contact patch looks like with added positive camber. It'll be *curved*
and the tread blocks will be distorting and *scrubbing* - more so at the
outer extremity.

BTW, I have that complete book from which that chapter is excerpted.
Lots of really good info in there though it doesn't delve into the
mathematics as much as does the *Fundamentals of Vehicle Dynamics*.

--

Xeno


Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)