More Do-It-Yourself Projects!
As always, excellent reading. Keep up the
diversity of AutoSpeed and I will certainly remain a loyal subscriber. I’d like
to suggest some possible electronic projects for keen AutoSpeeders. The first
and most desirable is an accurate wideband air/fuel ratio meter. I know this
has already been looked at by AutoSpeed and I assume the project was abandoned,
but looking at the capabilities of some of the other projects (like the DFA, DPA
and IEBC) surely these challenges can be met? The other is a servo-motor based
Digital Cruise Control. Obviously anyone with a turbo or supercharged car runs
into problems with the vacuum driven cruise control systems that are available.
And given the price of some of them, a Do-It-Yourself system could be hugely
beneficial. Anyway, keep up the good work.
Howard Hartman
Australia
More on Pivot Points and Chain Drive #1
In Response of 15 October, 2006
Response, Russell Hocken
rightly points out that a chain running through the suspension pivot point will
ensure the chain force has no effect on suspension vertical movement. HOWEVER,
there are two more forces at work that affect suspension movement - (1) the
horizontal force at the tyre contact patch and (2) the vertical force at the
tyre contact patch that is a result of ‘weight transfer’ when accelerating.
So, looking at the big picture, you need to run
the chain along a line that generates a moment about the suspension pivot that
cancels out the moments generates by the forces (1) and (2) mentioned above.
There are two ways to do this - using diagrams and calculating forces and
moments, or by experiment. Both are the clever way to get a great result -
AutoSpeed used the latter. The alternative is copying the 'conventional wisdoms'
or mistaken beliefs of others or taking pot luck - definitely not the philosophy
of AutoSpeed.
Please print my letter for all or at least pass it on
to Russell. I know he will be happier once he takes the 'big picture' view!
Rick Dathan
Australia
More on Pivot Points and Chain Drive #2
Regarding the email by Russell Hocken on your HPV
chain reaction force – Response...
The effect you're talking about is a well known
property in the Motocross world. When landing from a jump you can get more shock
absorption holding full throttle as opposed to backing off before landing.
There are also other effects on the bike due to
inertia of the wheel if you apply the brake and/or gas it up whilst in the air.
The combination of the two effects can be used to change the trajectory of the
bike in mid-air to some extent.
The reaction force also used when going over rough
ground (whoops, ruts etc.) to make the bike 'skip' across the top much faster.
About 20 or so years ago there was a guy in the US who put a fair bit of effort
into eliminating this effect to make suspension tuning on dirt bikes more
linear. The guys name was Horst Leitner and he designed a unit called the "AMP
Link" (among other things) which was fitted as a standard part on his MX bikes
under the brand name of ATK. The unit fitted around the pivot point of the
swing-arm and made the chain run parallel to the swing arm to eliminate the
'torque' effect. Another method was to make the centre lines of the swing-arm
pivot point and the drive sprocket co-linear.
I think that’s where Russel is getting confused as
the point he is making would be true if the centre lines of the swing-arm pivot
point and the drive sprocket were co-linear. Usually, the drive sprocket is
located some distance forward of the swing-arm pivot point hence the torque
reaction. Shaft drive motorcycles also do not have this problem as the shaft has
a uni-joint type unit that is inline with the swing-arm pivot point to allow for
the arc of the suspension travel. One benefit (some think) is that when you back
off or accelerate mid-corner, the bike doesn't want to sit-up or dive into the
corner because of the torque effect. A lot of bike riders get used to and like
the torque effect and feel very uncomfortable when this doesn't occur. I guess
it depends on what sort of bike you either learnt to ride or ride most often.
A friend of mine had the AMP link fitted to his MX
bike which he ended up removing because of the control over the bike he 'lost'
when riding MX or especially SX type tracks as you need to alter bike trajectory
as a matter of course if you want to go fast.
Darren Roles
Australia
Modification Certification
I am in the process of doing an engine swap and
starting to look for an engineer to provide the all-important certificate so I
can register my creation. I was wondering if you have had any dealings in this
area. I'm sure some of the mods you have performed over the years would have
required engineering. Adding turbos and superchargers for instance? I realise
that the process is different in each State but a general overview of what is
involved could be quite relevant and interesting to us AutoSpeeders. Keep up the
good work.
Ross Goddard
Australia
We haven’t covered this topic in AutoSpeed due
to, as you say, different requirements in each State – not to mention in
different countries! We suggest contacting your local Department of Transport
and some performance workshops..
Re the XU6 Loophole #1
As you probably already know, I read your magazine
regularly and enjoy it immensely. Although I will never get or do a highly
modified car like you often feature, I still find the articles interesting and
some of the ideas are good even for the minor mods that I do. That being said, I
really dislike featuring when people do things that are not legal. I am sure
(you have said) that nitrous is not legal for the road anywhere, so it should
not be applied to a road car (especially noted in the article about P platers in
Victoria). I find these articles very boring to read for that reason and I
think, in this instance, the car could have gained similar improvements with
other legal mods. Just my two cents.
Craig Dunn
Australia
Re the XU6 Loophole #2
Re: "stickin' it to the man” –
HSV XU6 - The P-Plate Loophole!... Advocating
that inexperienced drivers should buy a car that juuust scrapes in to what is
legal for them to drive, then promoting modifying it (so that it would clearly
be illegal for them to drive) is not only irresponsible but potentially lethal.
Legalities of the mods aside (though I assume the nitrous would only be used at
the drags... yeah right, who am I kidding?), the fact that young drivers make up
a disproportionately large number of road accident victims is a bloody good
reason to keep them out of high powered vehicles until their skills (and
attitude) develop.
As an alternative, why not promote ways to either
get fast driving off the streets (onto the track where it belongs) or at least
present a few articles on good (fast but safe) driving techniques? Maybe a
review of one of the advanced driver training schools?
Matt King
Australia
We can appreciate your position but, in this
case, we’re more comfortable with a P-plater driving a late-model car such as
the XU6 (with traction control, airbags, competent suspension and brakes)
compared to an old car with similar performance and inferior safety. Just think
of something like a Mazda RX3... Perhaps the Victorian P plate regulations
should take into account the passive and active safety built into each vehicle.
And, yes, anyone who – regardless of age - uses nitrous on the street is asking
for trouble. See Look - No Hands!
and Drive Right Buy for
articles on driver training.
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