BasOlij
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| posted on 23/1/03 at 03:57 PM |
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Attack
Hi everyone,
Just got this URL posted by a frield of mine:
http://www.euroworksltd.com/Attack/Attack-IT.htm
Seems to be a MR-kitcar, very nice looking but I was very surprised at the frame. Comparing it to mine and most other frames that have been posted
here the past few days it seems to me it is loads simpler in design.
Anyone got any ideas about this? I'm thinking about simplyfing my frame and incorparating some of this into it.
Greetz,
Bastiaan Olij
1984 Porsche 944 type 2
1981 Delorean DMC-12
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Rorty
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| posted on 24/1/03 at 01:44 AM |
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That looks like a well designed chassis, and not TOO cluttered.
Without wanting to dig up any old bones, I note the outriggers are relatively diminutive items.
What's going on with the rear suspension though? Looks like a cross between double wishbone and McPherson. It seems they could have saved quite a bit
of weight there alone.
It's difficult to see clearly, but they obviously want to keep a large area clear in the nose section, like someone else we know! However, I don't
think much of the manner in which they've located the bottom/inner mounts for the shocks.
I would prefer to see a higher waist too. 
[Edited on 24/1/03 by Rorty]
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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ProjectLMP
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| posted on 24/1/03 at 02:57 AM |
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Definately a lot simpiler. They are using a lot bigger size tubing than my design. It would be interesting comparing a more complicated small tube
chassis vs a simpler heavier tube chassis. I agree with Rorty about the sides. Not much in the way of side protection.
The way I look at it if you over triangulate the worst you get is an overly complex and potentially heavy chassis. Doing the opposite you could end up
with a death trap or a poorly handling car. I recently spoke to a guy who has a lot of experience designing space frame race cars. In his opinion a
lot of space frames he has seen have too much space and not enough frame. He said my frame was sound but not optimal in terms of strength/weight
ratio. He also said without FEA its very hard to optimize as some of the load paths are not intuitive.
Home of the Astronomicalcost Mid engined LMP project
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BasOlij
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| posted on 24/1/03 at 04:35 PM |
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Hey Rorty,
The rear suspension looks like what is described on the following page as a multi-link suspension and is the newest idea in suspension make-up.
http://www.fernblatt.com/longhurst/suspension_bible.html
LMP, I've found it touchest so far to deside on how far to go with the frame. It is very hard from my stand point as a total amature to know what is
good and what isn't. I'm going to complete the frame I have in 3D and then first build a scale model just like others here have done. That will
hopefully give me an idea if I am on the right track:-)
Greetz,
Bastiaan Olij
1984 Porsche 944 type 2
1981 Delorean DMC-12
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kb58
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| posted on 26/1/03 at 05:08 AM |
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Not new technology unless you count what Honda's been doing for the last 10 years or so. The entire rear suspension was taken straight from the
Honda and just dropped in. Look at their list of required parts:
http://www.euroworksltd.com/Attack/Attack-IT.htm
The Accord uses upper a-arm and lower trailing link + lower lateral links, with the shock/spring connected to the lower arm. It was just convenient
for Honda to run it through the upper a-arm.
Odd that they decided to make the front rocker-arms a "feature" rather than have the radiator exit out the top of the front bonnet. This would have
provided more downforce by not feeding all that air below the car (unless it exits out the wheelwells.)
It's also odd that they use the Accord power steering rack but don't include the pump in their list. I suppose it could work since there isn't
much weight on the front end...
IMHO, I have a hard time believing the claim it exceeds NASCAR specs. Have you seen the massive grid of tubes in the door way of a stock car? That
is certainly missing here...
[Edited on 26/1/03 by kb58]
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BasOlij
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| posted on 26/1/03 at 08:53 AM |
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Hey KB,
Are you sure? The accord is a FWD machine so it wouldn't make much sence to use its rear wheel suspension as the attack is an MR layout. I can't
find the reference to the rear suspension being used but could be overlooking it. In the donor car overview they only mention using the front
suspension as is.
Also from what I've read this suspension system is only used on the latest Audi's but I don't know if that info is trustworthy or correct (or old).
Bottom line, maybe the info I got is old an outdated but I find it a bit strange why you would use the rear suspension of a FWD car if you are
building an MR layout. The read suspension of a FWD car is usually not usefull as it doesn't take the drive train into account nor the extra weight
it has to carry cause the engine is right on top of it.
But hey, I'm just an amature:-)
Greetz,
Bastiaan Olij
1984 Porsche 944 type 2
1981 Delorean DMC-12
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Alan B
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| posted on 26/1/03 at 01:35 PM |
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Bas, I think that KB meant that that the entire rear of the Attack was taken staright from the FRONT of the Honda.....
Apologies if I'm wrong, but that was my interpretation.
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BasOlij
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| posted on 26/1/03 at 02:42 PM |
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Hi Alan,
Could very much be so. Again I'm no expert in this:-) It would certainly be the simplest approach.
Awell whatever way they did it, it still seems like a pretty cool design to me:-)
Greetz,
Bastiaan Olij
1984 Porsche 944 type 2
1981 Delorean DMC-12
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kb58
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| posted on 26/1/03 at 07:00 PM |
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Sorry, my post was not clear. Yes they took the entire front suspension, a-arms, shocks, axles, engine, and tranny from the Accord and dropped it in
the back of the Attack. I used the Prelude drivetrain arrangement in my project which is similar.
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Rorty
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| posted on 27/1/03 at 06:05 AM |
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That explains the rear suspension then. It does make sense to install the whole kit and caboodle from the one donor.
I obviously didn't read the whole lot, as I didn't pick up about it being on a par with a NASCAR. There's no way the Attack's chassis could have
the same or better specs. It's probably just up to doing the job it's designed for, but without a full cage, there's no way it could match a
NASCAR.
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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BasOlij
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| posted on 27/1/03 at 06:47 AM |
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Hi KB,
Okay now I follow you. I guess my info about the suspension being solely Audi is a little bit outdated then:-)
Greetz,
Bastiaan Olij
1984 Porsche 944 type 2
1981 Delorean DMC-12
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garethpowys
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| posted on 2/2/03 at 02:21 PM |
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Sorry I'm a bit late in on this one, but here's my 2p anyway...
Using donor subframes and suspension is always a compromise. Firstly because a pressed steel subframe and wishbones will tend to be heavier than a
properly designed tubular structure; secondly because the suspension geometry is unlikely to be right for the new application; and thirdly because the
diesign of your frame will be dictated to some extent by the original mounting points of the subframe. This latter can be even more problematic when
rear mounting a subframe originally used in a front engined car.
Using donor components in this way is very "old school" as far as kit cars are concerned. Fine for the budget end of the market, but more upmarket
kit cars (usually the more dynamically able) tend to use as few donor chassis components as possible. As many parts as possible being custom built,
often as far down as the uprights.
Now maybe some structural engineers can help me out on this one, but I always understood the theory behind a spaceframe to be that no tube should ever
encounter a bending load only compression or tension. Using bent tubing obviously makes this impossible. Going up in tube size and gauge to
compensate will only make the structure heavier.
I think both these major design points are about trade offs in your car's dynamic abilities and the ease and cost of construction. I think it all
depends on what you want and expect from your finished car. If you intend to use your car for some serious performance driving, particularly
competition, then you need to follow the harder and potentially more costly route of engineering purity. If you want a fun, cheap and unique road car
then go the easier route of more donor components and fewer and heavier tubes.
You pays your money and takes your choice.
Gareth
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Alan B
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| posted on 2/2/03 at 06:29 PM |
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quote:
Originally posted by garethpowys
........I always understood the theory behind a spaceframe to be that no tube should ever encounter a bending load only compression or tension. Using
bent tubing obviously makes this impossible.............
Yes, that is exactly the theory as I understand it. And, again yes, a bent tube is already pre-buckled and has lost some compressive stiffness.
However, IMO, good bent tube frames will often have other tubes meeting at the bends and the bend is effectively an alternative to a cut and angled
butt joint.
I'm not sure how this applies on the Attack as I haven't looked at it recently.
I'll bet Rorty has some views on this having also built round tube frames.
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kb58
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| posted on 4/2/03 at 03:28 AM |
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Not true on bent tubes being weaker than straight. Picture a bridge with a curved lower span to picture why. The curved span is in compression and
doesn't bend. It's the same technique racecar builders use on door bars. Yes the tubes are bent, but in a crash, they are in compression, in the
direction of bending them toward stright. As oriented they are stronger than if they were straight tubes, which would become weaker as bending takes
place. The curved tubes will better resist bending forces, in the important direction.
[Edited on 4/2/03 by kb58]
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garethpowys
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| posted on 5/2/03 at 07:41 PM |
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quote:
Originally posted by kb58
Not true on bent tubes being weaker than straight. Picture a bridge with a curved lower span to picture why. The curved span is in compression and
doesn't bend. It's the same technique racecar builders use on door bars. Yes the tubes are bent, but in a crash, they are in compression, in the
direction of bending them toward stright. As oriented they are stronger than if they were straight tubes, which would become weaker as bending takes
place. The curved tubes will better resist bending forces, in the important direction.
Sorry, but I think you're talking in a very specific sense there. In your example of the bridge the load on the bridge is attempting to straighten
the curved member, however this member is rigidly located at either end and so cannot straigten out.
In a space frame the forces are being fed into the tube at it's ends. The force will in effect either be causing the tube to straigten or bend
further. This is a simple fact and the reason why the majority of race spaceframes have always used stright members. Even John Cooper stopped using
bent tubes after winning his first F1 championship.
I'm not talking about accidents here, but the normal forces in everyday use.
Gareth
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kb58
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| posted on 7/2/03 at 06:42 AM |
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I thought we were speaking about curved door beams, in the context of accident protection. They work very well for that.
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garethpowys
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| posted on 7/2/03 at 03:48 PM |
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quote:
Originally posted by kb58
I thought we were speaking about curved door beams, in the context of accident protection. They work very well for that.
When I raised the point I was talking about bent tubing in the structural parts of the spaceframe. Specifically as used in the Attack. Sorry if I
caused any confusion.
Gareth
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