Free Isaac system!
- Thread starter gsbaker
- Start date
racer14itc
New member
Gregg,
Maybe if you stuck it on the doors in shear, but wouldn't the mount on the roof be in tension?
MC
MC,
Wise guy.
You are, of course, correct sir. However, the tensile strength is roughly twice the shear strength for this material so--downhill with a tailwind and a little luck--you are probably looking at a load carrying capacity north of 5,000# (each) in tension. Less in shear.
Hey, maybe we could pick up an Excursion or Hummer as a demo.
Wise guy.
You are, of course, correct sir. However, the tensile strength is roughly twice the shear strength for this material so--downhill with a tailwind and a little luck--you are probably looking at a load carrying capacity north of 5,000# (each) in tension. Less in shear.
Hey, maybe we could pick up an Excursion or Hummer as a demo.
racer14itc
New member
Originally posted by gsbaker@Nov 4 2005, 03:29 PM
MC,
Wise guy.
You are, of course, correct sir. However, the tensile strength is roughly twice the shear strength for this material so--downhill with a tailwind and a little luck--you are probably looking at a load carrying capacity north of 5,000# (each) in tension. Less in shear.
Hey, maybe we could pick up an Excursion or Hummer as a demo.
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Now THAT would be cool!! I didn't realize the tensile strength of the adhesive was so good.
MC
ITS48Datsun240Z
New member
I can see how the opposition would have trouble with the offset test, probably as a result of the displacement of the "collar" sideways under the belts.
...But I've got to play the devil's advocate, and ask for the results of the straight ahead 70G impact, and why you're not quoting those figures?
Because we don't have a specific value. Frontal loads are always lower than offsets, so if the offset is below the frontal limit, why bother running frontal tests?Originally posted by ITS48Datsun240Z@Nov 5 2005, 11:23 PM
...But I've got to play the devil's advocate, and ask for the results of the straight ahead 70G impact, and why you're not quoting those figures?
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(Isaac frontal loads would run 1,500N-2,000N. The HANS device will come in around 1,600-1,700N, although one can tune a 4-belt harness with a HANS to get under 1,000N, but that's not the SFI protocol.)
ITS48Datsun240Z
New member
To prove that the Isaac will prevent someone from breaking their neck in a frontal collision?
How can it be an absolute that offset loads are always higher? Wouldn't that vary with the design of the system? If a system was better at limiting the side to side motion of the head than forward and back, wouldn't the neck loads decrease as the imapct was offset?
The offset load is not a combined 68G frontal impact and an additional side impact, It's a 68G impact at a 30degree angle, right?
Whether the tension and shear loads were greater or less in the offset impact are determined by the design of the device, not the laws of physics.
Are you saying that you did not test the Isaac in a frontal test?
Whether the tension and shear loads were greater or less in the offset impact are determined by the design of the device, not the laws of physics.
Are you saying that you did not test the Isaac in a frontal test?
944-spec#94
New member
The ONLY reason to do a frontal impact is marketing.
Gregg and the boys are smart enough to calcuate the worst case and if they say the 30 deg offset is worse than I bet it is.
And with limited testing budget... why do an expensive test that is less stressfull than the one you just passed. <_<
Make 100% sense form and Engineering prespective.
Now from marketing perspective you are not comparing apples to apples and thus that really is the ONLY REASON to run a 70G frontal test.
Then again even without that I consider ISAAC
!
Hell I am even ready to buy... the ONLY thing that I am concerned with is if the racing bodies start Mandating SFI 38.1 If they do that and I have an ISAAC... well .... :angry:
I am feeling a little
by the man right now...
Gregg and the boys are smart enough to calcuate the worst case and if they say the 30 deg offset is worse than I bet it is.
And with limited testing budget... why do an expensive test that is less stressfull than the one you just passed. <_<
Make 100% sense form and Engineering prespective.
Now from marketing perspective you are not comparing apples to apples and thus that really is the ONLY REASON to run a 70G frontal test.
Then again even without that I consider ISAAC
! Hell I am even ready to buy... the ONLY thing that I am concerned with is if the racing bodies start Mandating SFI 38.1 If they do that and I have an ISAAC... well .... :angry:
I am feeling a little
by the man right now... Time out, everyone. I just realized the source of the problem. (Took long enough.)
Some of the comments here regarding the loads caused by a pure frontal (zero degree offset) impact compared to the standard 30 degree offset impact would make sense if the joint were the ball-and-socket style, as in your hip joint. But where your head connects to your neck more resembles your knee joint. In fact, those big bumps at the bottom of your thigh bone are called condyles, and the smaller ones at the neck-head junction are also condyles--specifically the "occipital condyles".
It's been while since I studied the specifics of this but, IIRC, the shape of the joint means there is less stress when flexed directly forward than when flexed to the side--similar to bending your knee to the side vs. straight front to back. That may not be the best analogy because your knee isn't really designed to bend to the side at all, but the mechanics are similar in the neck. The greater the angle the more the condyles are forced out of the matching "slots" in the atlas.
Frontal vs. offset loads are well documented in the literature.
The number we want to see is the HANS load value for the 30 degree offset 68G sled test at Delphi, i.e. the same test.
Some of the comments here regarding the loads caused by a pure frontal (zero degree offset) impact compared to the standard 30 degree offset impact would make sense if the joint were the ball-and-socket style, as in your hip joint. But where your head connects to your neck more resembles your knee joint. In fact, those big bumps at the bottom of your thigh bone are called condyles, and the smaller ones at the neck-head junction are also condyles--specifically the "occipital condyles".
It's been while since I studied the specifics of this but, IIRC, the shape of the joint means there is less stress when flexed directly forward than when flexed to the side--similar to bending your knee to the side vs. straight front to back. That may not be the best analogy because your knee isn't really designed to bend to the side at all, but the mechanics are similar in the neck. The greater the angle the more the condyles are forced out of the matching "slots" in the atlas.
Frontal vs. offset loads are well documented in the literature.
The number we want to see is the HANS load value for the 30 degree offset 68G sled test at Delphi, i.e. the same test.
If the device does a better job of limiting motion side to side, than forward and back, the loads will be less in an offset test...think about it.
If you're at delphi anyway, wouldn't it be cost effective to turn the table on the sled straight and do one more pull?
BTW my neck moves side to side, but my knee doesn't, is this unique?
lateapex911
Super Moderator
Gregg, just curious...I remeber discussing this wheN Jay (Wright) passed away, but I can't remeber the specifics. How much does a test actually cost??
There is no connection between head position and head loads. This is an old wive's tale left over from the last millennium. Move your head as far forward as possible. Are you dead?
Sure, if we expected to learn something. But no one is going to bother conducting a test if they know the outcome a priori--any more than you would pay a lab to throw a ball in the air just to see if it would come down.
See post #134.
Not much compared to medical!
A simple follow-up study for a simple medical device will run at least $1 million and take about five years. A full-blown double-blind prospective controlled study for a pharmaceutical is now about 1/2 billion.Crash testing is a comparative bargain, starting at about $2,500 per for the lab fee. Costs go up if one is looking for an unusual set up or instrumentation. And don't break anything; replacing a neck load sensor runs about $10K.
We figure $5K-$12K total by the time you throw in prototype production, travel, etc.
lateapex911
Super Moderator
So, running the second test could have some savings due to the "already there" status, but you're still looking at $6K or so....
And you wouldn't "learn" anything per se, but you could pinpoint a number, which would at least give you an answer for the doubters...
On the other hand, you can give away a lot of product for $6K and make some friends that way, LOL!
And you wouldn't "learn" anything per se, but you could pinpoint a number, which would at least give you an answer for the doubters...
On the other hand, you can give away a lot of product for $6K and make some friends that way, LOL!
