Bad OHS Example!
Building a Human-Powered Vehicle, Part 6. Whoever is doing the
TIG welding has got no welding protection like gloves and long sleeve shirt. Not
setting a good example for OHS!
Tony Goodlich
Australia
More re HPV Part Six
I’ve enjoyed the technical side of the articles on
building an HPV, but I have a few comments on the most recent one. In Building a Human-Powered Vehicle, Part 6, the following
statement is made...
“If the chain alignment is not correct, the pull
of the chain will cause the rear suspension to extend or compress with each
power stroke.
"The conventional wisdom appears to be that to
avoid this, the chain’s tension path should be through the rear suspension’s
pivot point. In other words, the chain pulls along the same path as a line
joining the axle to the suspension pivot point. This is then claimed to place no
resulting vertical force (up or down) on the wheel.
But this is wrong."
However it's not.... The vertical force is not
placed on the wheel. It is placed between the cog and its pivot. The bearing
opposes this force and nothing moves. I don't have a diagram, but it may be
easier to show what is wrong with what was proposed may be easier.
What was proposed is that the chain force should
run parallel to the suspension arm. However, the chain force and the reaction
force are thus separated by the cog radius. The resulting force vector is zero -
ie the suspension isn't pushed in any direction, however the torque force
required to counter the chain force and arm reaction force is not zero. When
summing the forces on an object, one always ends up with a resultant vector from
a reference point and a torque which has no reference point. I'd have to review,
but I don't think you've mentioned the torque (twisting) component in earlier
articles either. This torque force acts on both the wheel AND the suspension
dependant upon the wheel radius. I could draw a diagram and use some force
equations and justify myself if you'd like.
A complication with the system is that it is a
critically balanced one. So long as the chain passes through the pivot point,
there is no net torque on the rear suspension – however, as soon as it shifts up
a fraction, there is. This force tries to droop the suspension which most likely
will make the chain move further away and generate more and more drooping
force.
Russell Hocken
New Zealand
Perhaps we didn't make it clear enough in the article: we tried the chain line through the pivot point and it compressed the suspension with each torque application to the pedals. A very light suspension spring was fitted so that suspension movement would be obvious and torque was applied to the pedals with the rear tyre in contact with the ground. To give the least suspension movement, the chain axis most definitely was not positioned through the suspension pivot point.
Answer This...
Great magazine - keep it up. You have answered so
many questions that have bugged the sh#$ out of me for ages!
Mark Leerberg
Australia
Super-Lean, Economical Ford
Regarding your article Electronic Ways to Improve Your Fuel Economy... I have a 330,000km
stock five-speed EA Ford Falcon which has an aftermarket EMS-8860 specifically
installed to improve fuel economy. With the wide-band Lambda auto tune feature,
it allows you to do very accurate tunes quickly (especially around the cruise,
light load areas). On the stock ECC4 computer on the same route I used to do
around the 13.5 – 14 litres per 100km with granny driving style. Tuned to around
15.8:1 air-fuel ratio at cruise and light load and with ignition advance at
around the 40 to 45 degrees, the economy on the same route goes down to about
8.5 - 9 litres per 100km (still with granny driving). I've also tried the same
mod with an auto and found it didn’t respond any where near as well as the
manual. I think with a fresh engine with higher compression, extractors and a
few other tricks it’d be achievable to get low 8 litres per 100km.
Tony Goodlich
Australia
Combined Forces
I am fascinated by the two different avenues
pursued to cut fuel usage - the direct injection turbo diesel route and hybrid
technology.
It would seem that combining both would be even
better, given that diesels are very efficient at part throttle on the flat,
where the hybrid batteries may not be needed, or being charged. Have you heard
of anybody working along these lines?
Robert Lawrence
New Zealand
See Torque Overload: the GM Allison Hybrid Bus for
a diesel hybrid bus. It’d be great to see such a combination in commuter cars –
but we’re yet to see any examples.
Can’t Find the Technology
Just looking at an article from December 1999 – Giant Muffler Comparison - Testing Procedures... To your knowledge,
is the company ‘Exhaust Technology’ still in existence? A can’t seem to find
their products on the web. I was very impressed by your test and the results
that you obtained. Excellent job!
Curt Swan
USA
Exhaust Technology’s contact details are +61 8
8272 7500,
www.exhausttechnology.com
$15k Fun
I've been reading all your previous articles for a
while now and I gotta say that I’m impressed by your guys' honesty and that you
say what needs to be said. Ass-kissing outa the way... At the moment I’m after a
new car and would value your opinion and experience greatly. Basically, I’m
after a car that is RWD, turbo (would consider non-turbo), decent handling and
less than AUD$15000. Do you have much experience with cars that fit my criteria?
I was looking into S13s, MR2s, R32s and had thought about a NA Supra. Do you
have any experience with these cars and do you have any preferences or other
options?
Daniel
Australia
Depending what you’re after, all of the cars
you mentioned are great value in that price category. Don’t forget the Soarer
and, if you want something with four doors, Ford V8/XR6 and Holden
V8/supercharged V6.
Groovy
I was just thinking maybe it would be worth
looking into combustion chamber 'grooving' to promote greater engine efficiency.
See somender-singh.com His ideas
are patented but he likes everyone to experiment with them and report their
results. So far the news is good. A worthy tech article maybe?
T.Manganas
Australia
Interesting idea – do any readers have anything
to offer on the subject?
Memcal Hunt
My son is chasing a memcal for a Holden Commodore
VS Series 2 manual. He has converted the car to manual from auto and needs a
manual memcal. Is it possible to exchange (or reprogram) an auto memcal for a
manual unit?
Ian Peady
Australia
We suggest contacting a workshop that uses
Kalmaker programming software for Delco ECUs. Try Adelaide’s Awesome Automotive
- +61 8 8277 3927
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