mranlet
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| posted on 29/7/03 at 03:00 PM |
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Rorty-
I'm going to have to find the notes sheet where I have the arethmetic written. I wasn't able to figure it out myself - I sought the help
of my Calculus professor (who happens to be the Engineering professor). The comparison was made with the ATV weighing an estimated 500lbs with rider
and being subject to falls of 3ft from the ground (not unlikely, especially with those residing in the northeast US). The Car was estimated to weigh
1500lbs with driver when completed and have 4" Jounce and 4" rebound built into the suspension.
The final calculations put the car's force at somewhere around 80% of the ATV's force. I wish I could remember specifics but this was at
least 5 months ago, and I'm on working vacation so much of my plans are not with me.
Of course, this is going on theory without practice, but I do trust this Professor in his conclusions. If the ATV arms really won't work, it
will be important to know that - would I still be able to use the spindles/uprights and brake mounts though?
I am learning a lot about suspension forces and setup, but by no means am I an expert. One of the prime reasons that I come here is to learn more
about things which I know little...
Thanks for the input
-MR
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GO
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| posted on 29/7/03 at 03:37 PM |
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Davef,
Looking good!! Well done mate.
Is that an anti-rollbar you've got on the front there?
Cheers,
Graham
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splitrivet
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| posted on 29/7/03 at 03:57 PM |
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Davef,
Real nice looking job ,a credit to you
Bob
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leto
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| posted on 29/7/03 at 08:51 PM |
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quote:
Originally posted by Rorty
<snip> There's no reason why you can't obtain less than 1mm of misalignment.
Ultimately though, the car's handling will only be as accurate as the points the suspension is attached to (asuming the wishbones, at least, are
accurate!).
You could build a asymmetrical chassis, but as long as the car's footprint is symetrical, all should be well.
First: "Accurate" is a expression that belong in mathematics. In "the real world", a workshop for example, it can't be
used if it isn't followed by a "within".
This is a very important key to understanding engineering and misuse makes me a little upset. Sorry for the outburst.
I agree that you can, but I don't see any reason why you should obtain less than 1mm of misalignment. Except of course for the fact that you
can. That is: it makes you feel good and I respect that reason.
We were discussing the frame here. A car standing on grid waiting for for the race to start is another story. And as you say the thing that really
matters then is "the points the suspension is attached to". To be of any real value these points have to be measured on a fully loaded
chassis suspended on its springs, accurate within a mm or two and in a way that can be repeated with the same accuracy. This is a tricky operation
that very few locost builders have the resources to carry out. Actually it is tricky to carry out on the frame alone, as the "point" turns
out to be two holes with a gap between them and somehow, the centrelines from the drawing are not there 
Most builders have to rely on using jigs and do their best. Luckily this seem to be good enough.
I fully agree to what you say, except the "accurate" wishbone. Do you have any suggestions on how to apply any of this on a lococt
chassis?
Cheers Leif.
[Edited on 29/7/03 by leto]
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Stu16v
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| posted on 29/7/03 at 09:45 PM |
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Striving for the perfect chassis suspension accuracy is extremely important and cannot be stressed enough.
But TBH, I have raced cars with bent chassis before now, and have still been competitive, and anybody that has watched any disipline of motorsport
have have all seen examples of this to a greater or lesser degree before now.
What I am trying to gabble is this. If a racecar being driven on the limit can be relatively unaffected by obviously serious misalignment of
suspension pickups, should the ideal of building to within 1mm be important, or just a goal to merely strive for? I personally feel it's the
latter. As already mentioned, production cars, especially up until a few years ago, were generally built to be within 5mm, sometimes a lot more. Look
how much adjustment is usually given on door catches? Wouldnt be necessary if they they were put together properly....
Throw the 0.5 mm buckle in each wheel, a bit of play in the wheel bearings, the slight discrepancy in the hub flanges, the twist of the wishbones,
flex of the suspension bushes, the flex in the steering rack bushes, and the twist in the chassis and it's a wonder the car even goes in a
straight line!
But the more you can knock off (or at least lessen) in the above list, the better the car will handle. Accuracy is very important, but not at the
expense of never getting the car finished! After all, most of the builders here will not be driving the car at 10/10ths in race conditions, they just
want a decent handling sports car. With such low weight and centre of gravity, it would be hard not to improve on your average tintop.....
Dont just build it.....make it!
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burgessj
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| posted on 29/7/03 at 10:28 PM |
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I know I will not be able to achieve a tolerance of less than 1mm. TBH, I'm dead chuffed that I have managed to get the bottom section true and
the overall length measures exactly right. I'm not going to get any better with the basic tools that I've got. The only thing that
concerned me was when I cut pieces to the lengths given in the book and they didn't fit. Thanks to the advice given in these posts I now know
there are mistakes in the book and I'm a lot more comfortable with it. I'm doing diagonal checks all along the way to make sure
it's square and I'm making sure the outside dimensions are right. So I'm pretty confident of ending up with a decent frame for my
first attempt.
I'm crap at maths anyway!
JohnB
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Rorty
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| posted on 30/7/03 at 01:47 AM |
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Davef, well done, you're on the right track!
mranlet, theory can be a dangerous commodity.
quote:
would I still be able to use the spindles/uprights and brake mounts though?
yes, if you can attach better ball joints, and are certain the brake mounts will accept larger calipers.
Leto:quote:
First: "Accurate" is a expression that belong in mathematics. In "the real world", a workshop for example, it can't be
used if it isn't followed by a "within".
Semantics! Why not encourage people to strive for perfection. If you have the attitude that "it's only out by a few mm....just
like the big production companies", then all the discrepancies add up, and compound, to a botched job.
Mr SVA is also going to be more impressed with a car that looks as if some care and attention has gone into it.
quote:
Actually it is tricky to carry out on the frame alone, as the "point" turns out to be two holes with a gap between them and somehow, the
centrelines from the drawing are not there
Why not? If you set your chassis stand up propperly from the start, and add registers to various crossmembers as you go, it's hard not
to be accurate.
quote:
Do you have any suggestions on how to apply any of this on a lococt chassis?
Yes! Build accurate Jigs! It's not rocket science, and perfectly in keeping with the Locost tradition....fiddling and building at
home.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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davef
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| posted on 30/7/03 at 06:30 AM |
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Hi all thanks for the positive complements, and yes GO that is an anti-rollbar up front 14mm dia also Spax adjustable shocks. cheers davef.
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leto
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| posted on 30/7/03 at 08:00 AM |
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Rorty/
Don't have time to answer you right now, sorry  Going to visit a friend for a cupel of days 
See you all, later 
Leif.
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Viper
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| posted on 30/7/03 at 12:16 PM |
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quote:
Originally posted by leto
I make my living out of designing welded structures. If I was to hand out a drawing of something that was over 2m long, 1m wide and 0,5m high, made
out of 60 segments of pipe, welded together and ask it to be right within 1mm....actualy it is a little hard imagining what might happen but it is not
a good career move. A professional welder would probably say it is impossible,
I wish the people i have worked for in the past had your attitude, if your profesional welder says its imposible i would sack him and get someone in
who can do the job.
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Mark Allanson
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| posted on 30/7/03 at 12:47 PM |
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I agreement with Viper there, perhaps that is why Volvo's are so big?
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leto
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| posted on 3/8/03 at 08:55 AM |
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Rorty:
Think we have entered the "Ways to look at the world"-department, where you find politics, religion, sport-fan-ship and such.
quote:
Semantics!
Yes and..? We are, to a very high extent, dependent on the language to express our thoughts, intentions, views and ideas. Sloppy use of language,
especially technical language, will just cause unnecessary confusion.
I don't want to discourage people from expressing themselves just because they don't know "all the right words". If you
don't use the words you have you will never find out what the right words are. Use your tools as good as your ability allow you.
If "accurate" is used without any "within" in a technical context i will read it as "accurate within zero" and
that will turn your statements into nonsense. You will never know if something is accurate within zero because there is no way to measure it without
errors.
I would really like to know how accurate your "accurate wishbone" actually is.
quote:
Why not encourage people to strive for perfection.
"The perfect is the ultimate and the ultimate is death" [C.N.Parkinson,
my translation from Swedish, as I don't have a original.]
Perfection as a goal, is a dead end and will hamper creativity and curiosity. You start with a fix image of what you want to achieve and have no need
to explore anything new. There is only one small point of success and it is very hard to get there, so you most probably end up with a failure. If you
achieve your goal of perfection the result is useless as every thing you do will spoil it.
I want to encourage people to strive to do better, to improve things, to find new ways, to see different solutions. I want people to allow themselves
to end up with something that is better than they imagined possible.
quote:
If you have the attitude that "it's only out by a few mm....just like the big production companies", then all the
discrepancies add up, and compound, to a botched job.
Mr SVA is also going to be more impressed with a car that looks as if some care and attention has gone into it
I fully agree. Do your best.
But there is no point in over doing it, except to make you feel good.quote:
quote:
Actually it is tricky to carry out on the frame alone, as the "point" turns out to be two holes with a gap between them and somehow, the
centrelines from the drawing are not there
Why not? If you set your chassis stand up propperly from the start, and add registers to various crossmembers as you go, it's hard not
to be accurate.
Here we go again. How accurate is "accurate"? Zero, 1/100, 1/10, 1/2, 1, 2, 3, mm, inch? As accurate as your tools? How accurate
are they, then and how accurate is your method of measuring?
quote:
Build accurate Jigs! It's not rocket science, and perfectly in keeping with the Locost tradition....fiddling and building at
home.
Hear, hear! Well maybe not "accurate jigs" more
like, really good and innovative jigs.
Happy building!
Leif
[Edited on 3/8/03 by leto]
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leto
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| posted on 3/8/03 at 09:28 AM |
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quote:
Originally posted by Viper
I wish the people i have worked for in the past had your attitude, if your profesional welder says its imposible i would sack him and get someone in
who can do the job.
And you probably kicked out someone how cared what he was doing, for someone how don't, but knows how to say "Yes, boss.".
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burgessj
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| posted on 3/8/03 at 11:41 AM |
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I have made much more progress with my build these last few days now that I know about the naff measurements given in the book, but it still doesnt
stop me checking and re-checking all my dimensions every time I come across another error. I've found the best way for me to make progress is
to make sure that the external measurements of the frame are correct, and then cut the cross members to fit, making sure that they are in squarely and
that the spacing between them is correct (logditudenally). I had further problems with J1 and J2 though, because I had already tacked them to the
front assembly only to find that they werent parallel to the the botton rails (D).
Anyway the rear is coming on nicely. I managed to rig up a big set square and clamp it to the frame so that I could get the rail exactly 21"
from the surface.
I just hope it doesn't all move when I do the final weld!
Still not sure what to do about wishbones..Luego have them reasonably priced. I'm a bit worried about having to adjust the front to fit
someones wishbones in case some other bits don't fit (nose cone /bonnet etc).
JohnB
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Viper
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| posted on 3/8/03 at 04:04 PM |
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quote:
Originally posted by leto
quote:
Originally posted by Viper
I wish the people i have worked for in the past had your attitude, if your profesional welder says its imposible i would sack him and get someone in
who can do the job.
And you probably kicked out someone how cared what he was doing, for someone how don't, but knows how to say "Yes, boss.".
WHAT? What are you on about?
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Mark Allanson
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| posted on 3/8/03 at 09:17 PM |
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Leto,
I think we must have misunderstood what you mean, Viper and I are both qualified professional welder, and welding a structure to 1mm accuracy is a
mundane day to day task.
Without proper tools and measuring equipment, it may be more difficult, but in a production environment , its just what you get paid for - I am sure
that this is the same in Sweden, they (you) have a good reputation for welding, having one of the best welder manufacturers in the world - ESAB.
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jcduroc
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| posted on 3/8/03 at 10:40 PM |
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quote:
Originally posted by Rorty
Why not? If you set your chassis stand up propperly from the start, and add registers to various crossmembers as you go, it's hard not to be
accurate.
Do you have any suggestions on how to apply any of this on a lococt chassis?
Yes! Build accurate Jigs! It's not rocket science, and perfectly in keeping with the Locost tradition....fiddling and building at home.
This may seem redundant in this discussion but I think (I've already written that) that a Locost build should start by putting the wheels
assemblies in the correct position in a jig and build the wishbones/chassis/etc from there on.
At least that's the way I'm planning to do.
Joćo Matoso
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leto
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| posted on 4/8/03 at 09:51 AM |
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quote:
Originally posted by Viper
quote:
Originally posted by leto
quote:
Originally posted by Viper
I wish the people i have worked for in the past had your attitude, if your profesional welder says its imposible i would sack him and get someone in
who can do the job.
And you probably kicked out someone how cared what he was doing, for someone how don't, but knows how to say "Yes, boss.".
WHAT? What are you on about?
Sorry to have upset you, Viper. As Mark Allanson suspected, I totally misunderstood you. Absolutely no offence intended. Thanks for setting me right
Mark!
My experience comes from a world were 10mm plate is refereed to as thin and something the size of a locst frame is tiny. Here, 1mm accuracy only exist
in some designers dreams.
Stupid of me to interpret this directly to "your world".
Leif
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