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Author Topic: firewall forward frame design  (Read 10279 times)
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JackD
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« Reply #15 on: October 23, 2007, 03:36:34 PM »

Track width is commonly the distance from center to center if the tire.
There is an aero trick used on modern cars with a feature around the fender well that gets the air by smoothly without skirts and allowed adequate movement for maneuvering.
They spend a lot of time and money on it and you can copy it for free.
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« Reply #16 on: October 23, 2007, 04:13:58 PM »

Track width is commonly the distance from center to center if the tire.
There is an aero trick used on modern cars with a feature around the fender well that gets the air by smoothly without skirts and allowed adequate movement for maneuvering.
They spend a lot of time and money on it and you can copy it for free.

     

John talked to one of the guys with Blowfish and that little lip there deflects the air around the opening and it is suppose to reattach behind the wheel opening.  But there again they developed it with wind tunnel time.  You can make some guesses and hope you are right or use Hooley's Okie wind tunnel and blow air at the area with your air compressor and throw baby powder in the air and see where it goes,

Sum
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JackD
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« Reply #17 on: October 23, 2007, 05:36:29 PM »

1. Wet the surface down and see where it sticks.
2. Film it at El Mirage and see where the dirt goes, doesn't go , and stays.
3. Only use NEW powder. the old stuff sticks to anything.
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Jonny Hotnuts
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« Reply #18 on: October 23, 2007, 05:58:25 PM »

I was able to get in contact with J. Miller today and have a WAAAAY better understanding now about what the SCTA's intent is for the MS class and an understanding of how the process works. Funny thing is that he was aware of some of the things I was considering doing to the car…..odd how word gets around!!!

I get it now….and D.W. is in fact not the enemy of creativity after all!  (Joking Dan)

The idea and proposed changes were not entirely original on my part but rather a combination of things that had already been allowed to run, currently and in the past on many different cars. In the conversation with Miller I had even mentioned the design aspects of the “Saab Sonnet” without knowing any of its history and eventual outcome. Without getting into details I understand that I should not take design references from a past car and assume that it is ok because it was done before….because there were many things about the Sonnet that were NOT ok….then or now.


I think that setting a minimum track width is fine….but personally would like to see more than 3” per side. 6”per side would allow for enough clearance for a 22-30” tire to have an acceptable turning radius and still have covered wheel wells as allowed in the class without having to take compromises in tire width to gain the ability to effectively turn. This is just my opinion however and while I can agree that there are cars out there with covered wheels that likely have 3” from OEM there are also cars currently running that will not meet this proposed spec..
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« Reply #19 on: October 23, 2007, 07:06:43 PM »

As Jack said, rotating a square tube 45° improves its bending resistance considerably (but a PITA to work with, all miter cuts). The off-axis (across the flats) is almost completely immune to bending stress except in a wreck.
IIRC the change is +41.4% to the side length (the stressed axis being the diagonal rather than 1 side).
Where S = length of 1 side, and 1.4142 is 1 ÷ SIN (45°), the new stiffness (assuming equal execution) is:

(S*1.4142)^4 ÷ S^4
Example only; if S = 1":
(1*1.4142)^4 ÷ 1^4
1.4142^4 ÷ 1 = 400% (+300%)

Nice improvement with no weight or material change, just more work!
Note: a smaller change will still occur if the tube is a rectangle, substitute the sine of the diagonal angle in the values.
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JackD
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« Reply #20 on: October 23, 2007, 08:07:11 PM »

Too much information.
Turn it 90 deg, and press on. wink
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Unkl Ian
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« Reply #21 on: October 23, 2007, 08:08:38 PM »

We will be cutting it close on the Berkeley.  I guess it is up to us to provide the documentation to prove the legality.  The Berkeley workshop manual calls out a "track width" of 42".  Depending on how you interpret track width will determine if we have to make any changes. Are they referring to outside to outside, or tread center to tread center, or hub to hub?

Text books usually define Tread Width as center to center on the tread.

Some racing body rules define Tread Width as outside to outside.

Some rules just specify max or min tread width,
without defining how it will be measured.
« Last Edit: October 23, 2007, 09:30:31 PM by Unkl Ian » Logged

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« Reply #22 on: October 23, 2007, 08:10:10 PM »

Double post.Sorry.
« Last Edit: October 23, 2007, 09:29:57 PM by Unkl Ian » Logged

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« Reply #23 on: October 23, 2007, 08:47:40 PM »


Quote
We will be cutting it close on the Berkeley.  I guess it is up to us to provide the documentation to prove the legality.  The Berkeley workshop manual calls out a "track width" of 42".  Depending on how you interpret track width will determine if we have to make any changes. Are they referring to outside to outside, or tread center to tread center, or hub to hub?



The spec of the Berkeley track 1.12 meters (44.0 inches) unless you have a narrower one or maybe this was for the rear wheels if they were diffrent from the front.

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dwarner
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« Reply #24 on: October 24, 2007, 07:34:03 AM »

"Some rules just specify max or min tread width,
without defining how it will be measured."

Page 19.

DW
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Sumner
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« Reply #25 on: October 24, 2007, 10:05:33 AM »

"Some rules just specify max or min tread width,
without defining how it will be measured."

Page 19.

DW


Dan that does define how it will be measured:

"Tread is defined as the measurement from the centerline of one tire to the centerline of the opposite tire of paired wheels".

Is the new rule going to just effect MS or CC and others??

Thanks,

Sum
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dwarner
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« Reply #26 on: October 24, 2007, 10:14:21 AM »

MS - the point is to keep the cars looking like cars. The rewritten MS rules, after the demise of the original class, was to keep the cars looking somewhat like streetable cars like Gas Coupe.

DW
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JackD
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« Reply #27 on: October 24, 2007, 10:39:04 AM »

In the days of the real Modified Roadster, Tread was required to be a % of the wheelbase.
The longer you made it, the wider it had to be.
Now with the stretch jobs, we have reinvented Sports Racing.
Hang a replica body on a Streamliner and you can have a Modified Sports, Modified Roadster. or a Comp Coupe.
The flexibility is remarkable and has improved the ability to bend over.
I guess it is OK if that is what you want.
« Last Edit: October 24, 2007, 10:53:55 AM by JackD » Logged

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« Reply #28 on: October 24, 2007, 02:37:44 PM »

Is it too late to return Modified Sports to some semblance of what the cars originally were? At least one of the stretched Berkeleys has a Berkeley nose. I can see the necessity for safety of allowing chin spoilers, but why not stop it at a stretch and a spoiler? Does anyone have a car that would need to be scrapped?
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« Reply #29 on: October 24, 2007, 03:19:32 PM »

Turk's old car would require a new suspension and a new front clip, Bonner would a new front clip, and believe it or not ours is an original clip but has enough modification that it would be easier to start with a new clip rather than convert it back to original.  I wonder if our local Berkeley dealer has one in stock?

Are the changes coming out going to be mandatory for the '08 racing season?
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