Rule change proposal- weight sheet as part of scrutineers

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BIG GAZ
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Rule change proposal- weight sheet as part of scrutineers

Post by BIG GAZ » Mon May 04, 2015 10:37 pm

The Committee has floated the idea of requiring weight distribution, Centre of Pressure and Centre of Gravity as mandatory information to be provided by the entrant on the scrutineers tech sheet for vehicles over 200mph. This should be verified with a weight sheet printed out and supplied at scrutineering.
It is well known that the above determines how stable a vehicle is at speed and the Committee feels that any effort made to make vehicles safer is well worthwhile. Vehicles that spin at speed that is not due to driver error or mechanical malfunction must be minimised.
I will post a link shortly to explain the above.
This is now open for discussion.
GAZ

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Re: Rule change proposal- weight sheet as part of scrutineers

Post by BIG GAZ » Mon May 04, 2015 11:33 pm

Here is the link:
http://scienceenvy.com/race-car-enginee ... -on-track/
CG and CP can fairly easily be determined. Anyone following the Shaguar on the build forum will see the pictures from the corner scales. Weight distribution front to rear is calculated and displayed.
If I can convince the co-owners of the corner scales we may take them to the salt next year and offer a weighing service (all fees to the DLRA of course!)
GAZ

momec3
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Re: Rule change proposal- weight sheet as part of scrutineers

Post by momec3 » Tue May 05, 2015 9:11 pm

Takes no convincing here Gaz, if we can help building safe fast racecars then I will bring the scales. A donation to the club is all I will ask.
Knowing the weight balance gives you a starting point. Unfortunately you have to finish the car to find out the corner weights before you can adjust it. Most of us get to this point the week before we leave for racing.
It is simply maths and physics. If racers take the time during their build to give this some serious thought it WILL make the difference. If anyone requires help figuring this out contact Gaz or myself.
Chris

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Greg Watters
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Re: Rule change proposal- weight sheet as part of scrutineers

Post by Greg Watters » Wed May 06, 2015 8:52 am

Is this fact finding to help people understand the cog/cop relationship ? or is there a cutoff point for unbalanced vehicles in mind ?

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gennyshovel
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Re: Rule change proposal- weight sheet as part of scrutineers

Post by gennyshovel » Thu May 07, 2015 3:40 pm

Anyone who does not realise the importance of CG/CP relationship may need to watch this Terry Nish interview :-
https://www.youtube.com/watch?v=a7aa_Tc ... e=youtu.be
Tiny DLRA# 484
Postiebike Racing , created & funded by TwoBob Engineering

BIG GAZ
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Re: Rule change proposal- weight sheet as part of scrutineers

Post by BIG GAZ » Thu May 07, 2015 4:06 pm

Greg,
The Committee is committed to increasing the safety level of all race vehicles/bikes. The risks seems to be greater over 200mph and as the Rule Book uses this threshold for a number of other rules it seems convenient to adopt this speed, but again open to discussion. There is no talk of a 'cut off' point of any sort for any vehicle to date. The Rule Book already allows for any unbalanced vehicle, possibly demonstrated by a spin, to return to tech and be checked. It is the drivers responsibility to ascertain why the vehicle spun out and show to the satisfaction of the Chief Steward what has been changed to mitigate the possibility of another spin.
If racers who are building >200mph vehicles do not know corner weights at least we believe that the club has the responsibility to inform and educate those individuals. This is the purpose of this discussion at present.
Thanks
GAZ

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Re: Rule change proposal- weight sheet as part of scrutineers

Post by DLRA » Fri May 08, 2015 1:24 pm

Just found this today, makes interesting reading

http://www.onallcylinders.com/2015/05/0 ... ag-racing/
Keep the shiney side up........
DLRA WebMaster / Editor

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Greg Watters
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Re: Rule change proposal- weight sheet as part of scrutineers

Post by Greg Watters » Fri May 08, 2015 7:30 pm

Thanks for the explanation Gaz
i dont think its a bad thing , but want to be sure there is a science to it
Some of the comments in Gregs link seemed just scary to me, my experiance in ballast and speedway sedans would suggest anything added much behind the axle as a pendulum , but thats only one form of racing and we have a wide range of experiances to draw from

I did like this comment

There has been a lot of writing about finding the center of gravity in a race car, but the reality is, this “science” is, at best, a guess.

The only way you’ll determine the proper ballast location is with testing.

momec3
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Re: Rule change proposal- weight sheet as part of scrutineers

Post by momec3 » Sat May 09, 2015 12:10 pm

The only purpose of a drag race chassis setup is to plant (hook) the rear tyre off the line and continue that weight transfer as long as possible down the strip. This is often at the expense of high speed stability.

The part of their setup that I think applies to salt racing is left to right balance.
As we progress down the track the air pressure load increases. To counter the torque reaction more static weight bias needs to be on the LH side. Providing we have adequate ballast/traction this should even itself out at max load.
Max load in our case is when we are pushing maximum air (speed) as opposed to drag racing when its in the first 60ft of the track.
Given a choice this is better done with increased preload on rh springs easy with adjustable coilovers but the same result can be achieved with ballast and ride height adjustment.

Agreed Greg, testing. From a scrutineers standpoint interviewing drivers of good handling cars and bad. Keep a database. By helping racers know what they have under them before they leave the line ie access to scales and knowledge of CP data , then more realistic conclusions can be drawn.
Bob does an excellent job now so adding this info would only help.
Chris

michael240
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Re: Rule change proposal- weight sheet as part of scrutineers

Post by michael240 » Wed May 13, 2015 3:30 pm

On the Black Mastec Ute we run the following weights

LF 1416.5 POUNDS
RF 1372.4 POUNDS
TOTAL WEIGHT FRONT = 2,788.4 POUNDS

LR 1583 POUNDS
RR 1543 POUNDS
TOTAL REAR WEIGHT = 3,126 POUNDS

TOTAL VEHICLE WEIGHT = 5,915 POUNDS

OUR FRONT TO REAR SPLIT IS APPROX 47% FRONT AND 53% REAR

In 2014 after checking our data we found the FL was lifting even though it was 44 pounds heavier than the FR.
To counter this we increased the Pre Load on the RR x 4 full turns approx 4ml. Did another run checked data and it fixed the problem.

I still think we need more weight over the rear as traction is still a problem. In 2014 we had 35% wheel slip (BAD SALT). In 2015 albeit we only ran 1 mile before I melted 2 pistons we had 15% wheel slip (good salt)

I have put this forward as other races may find it helpful.

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Rocket
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Re: Rule change proposal- weight sheet as part of scrutineers

Post by Rocket » Mon Jun 29, 2015 1:22 am

Thumbs up for the info on CP & CG for the scrutineers to see, possibly even marked on the car wouldn't hurt?
Any more thoughts on this??
CHEERS,
Rod. #811

www.rodsandrelics.com.au

BIG GAZ
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Re: Rule change proposal- weight sheet as part of scrutineers

Post by BIG GAZ » Tue Jun 30, 2015 8:24 pm

Sorry guys, I have been flat out at work. The business has been purchased by a large listed Wa company so there has been lots of distractions for me.
I am still keen to have something available as guidance for 200mph plus vehicles. Markings (CP and CG) on the car are a great idea Rod.
GAZ

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