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Excessive braking calculation? #2735525
01/22/20 10:32 AM
01/22/20 10:32 AM
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SportF Offline OP
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So last fall I raced a car dialed 8.00 which he said would run in the high sixes. He ran over at 7.868 at 140.56. Looking at calculators a 7.86 should be about 185 mph.

His 1000 ft time was 6.427. Is that 1000 ft mark indicate he was still wide open at that point, or does that indicate he was already off the gas and perhaps on the brakes there?

After thinking about this, if he dropped 45 mph in the last 2-300 feet that sounds like a lot of speed to drop?

Can somebody who runs that fast clue me in here. Really just curious. He took the stripe by about 5 cars and it was an easy win, but none the less, is that excessive braking?

Re: Excessive braking calculation? [Re: SportF] #2735574
01/22/20 12:44 PM
01/22/20 12:44 PM
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Tulsa, Oklahoma
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If your question is should he have been disqualified, I would say that depends on tire smoke.

No tire smoke I would say he is golden.

If there is tire smoke enforcement is all over the map.

I remember one the the Emmons brothers being disqualified for rather modest tire smoke but after at least one warning.

I also remember one of Dan Fletcher's sons completely looping a Camero after excessive braking and I think all he got was an "ata boy". However I don't remember if he actually one the race, but I think he did.

Re: Excessive braking calculation? [Re: 340Cuda] #2735589
01/22/20 01:28 PM
01/22/20 01:28 PM
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Park Forest, IL
slantzilla Offline
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If there was no smoke, no excessive braking as said above.

That said, it's really hard to knock off a lot of ET just slowing and braking at the big end. I've scrubbed 30 mph off a 130 mph bike and only lost .3. Trying to slow down a fast car over a second is a big order.


"Everybody funny, now you funny too."
Re: Excessive braking calculation? [Re: SportF] #2735591
01/22/20 01:33 PM
01/22/20 01:33 PM
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Minn
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SportF Offline OP
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I wasn't looking for a disqualification, I won the round. The question I am asking is "was there a lot of hard braking" in the last 2-300 feet? Or did he let off the gas prior to 1000 ft.

I never saw smoke.

And, would a race director or other official be able to look at that and say too much loss of mph. Purely a curious question.

I've seen the spin around in the aforementioned post, got lucky there.

Re: Excessive braking calculation? [Re: SportF] #2735593
01/22/20 01:38 PM
01/22/20 01:38 PM
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Keymar, MD
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I'm not up on all of the safety requirements, but was he limited to dial 8.00 due to not having something required to go faster? Not sure why he would purposely hold .4s. I know guys that hold, but .4's is alot.

Re: Excessive braking calculation? [Re: SportF] #2735595
01/22/20 01:43 PM
01/22/20 01:43 PM
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Fulton County, PA
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He was too far down track when he tried to get it slowed down predictably. Obviously he left after you. His tactics were lousy. He should have caught you mid-track somewhere and fender raced you.


If the results don't match the theory, change the theory.
Re: Excessive braking calculation? [Re: CMcAllister] #2735618
01/22/20 03:00 PM
01/22/20 03:00 PM
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I was 10.50. He was relatively new to the car, and I believe, but don't know, it was the first time at that track.

I had heard his previous 2 time trials were both spin fests, so when I found I was matched with him it wasn't with regret. He had already told me the car was high sixes capable, but turned down for this track, max et limit of 7.50. So, I am guessing the 8.0 dial was guessed, with some spin thrown in.

If you use a Wallace calculator the 7.86 is way off from the 140.56mph. His 1/8 mile mph was 150.05, which in the calculator shows up to be a 7.18 at 185. Also, his 1000 foot was a 6.427 and the calculator shows that to be a 7.80 and 170mph.

So, some speed was scrubbed, when did that happen, in the last 300 feet? And, has somebody who runs that kind of ET, how hard on the brakes does that take?

Re: Excessive braking calculation? [Re: SportF] #2735663
01/22/20 07:06 PM
01/22/20 07:06 PM
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central ohio
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nss guy Offline
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Did he pull the chute?

Re: Excessive braking calculation? [Re: nss guy] #2735670
01/22/20 07:58 PM
01/22/20 07:58 PM
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Originally Posted by nss guy
Did he pull the chute?



That I don't recall, but I don't believe so. He didn't come around after the run, and getting mine ready for next round I didn't look him up (although he was basically across the pit road from me).

I had went over to talk to him when he fired the car up to pull it out of the trailer. I basically said that he had the badest sounding car on the property, and it was at that point he told me the car was capable of high sixes. I don't believe there was any dragsters that fast there that day, but as I said, the track has a 7.50 max et anyway.

This was a 69(?) Firebird with a blower, a go to town kind of blower, on a tube chassis. I'm sure it was the fastest car there, and the fastest I have ever run.

Last edited by SportF; 01/22/20 08:00 PM.
Re: Excessive braking calculation? [Re: SportF] #2735726
01/23/20 01:46 AM
01/23/20 01:46 AM
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Bend,OR USA
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My N/A single dominator carb E85 motor in my 2750 Lb. S/P bracket car has ran 8.864 at 148 + MPH all out and then by upping the 1st to high gear shift RPM(powerglide tranny) from 7000 RPM to 7300 RPM ran 8.886 at 150.+ MPH shruggy
My message is once you get near 150+ MPH HP comes into play a lot the last 300 Ft. in the 1/4 mile twocents
For him run that quick at 140 MPH tells me he was on the brakes hard before the finish line, not just off the throttle only twocents


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Excessive braking calculation? [Re: Cab_Burge] #2735773
01/23/20 08:45 AM
01/23/20 08:45 AM
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.....and if you’re collecting data it’s always favorable to race it to the 1000ft mark. Not saying he did, but it helps to have the numbers.

Re: Excessive braking calculation? [Re: J_BODY] #2735810
01/23/20 11:59 AM
01/23/20 11:59 AM
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How about this answer. Since you really have NO IDEA what the car can or wqas actually going to run you have zero clue as to how much MPH he killed. Suffice it to say if he was going 150 at the 1/8 he killed PLENTY of MPH. You could say he would EASILY gain 35-40 mph on the back half, typically dragsters do not have the back half mph of a door car why the wide margin I stated is 5mph.

Jay while I agree with you that running it to 1000' is preferable there is NO WAY a car going 7.0/190 is killing 5 tenths in the last 320'. He is simply covering to much ground to quickly, at those speeds he is likely covering 260-270feet per second at the 1000' cone.

Re: Excessive braking calculation? [Re: Al_Alguire] #2735827
01/23/20 01:08 PM
01/23/20 01:08 PM
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SportF Offline OP
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Thanks for the insight. Looking back at it, it was a memorable fun pass for me.

Re: Excessive braking calculation? [Re: SportF] #2735860
01/23/20 03:06 PM
01/23/20 03:06 PM
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Before keystone started running my class 1/8 mile my buddy wth a car that could run 4.60’s in the 1/8th would let off at the 1/8th or 1000 foot stripe and coast the rest of the way. That way he still got the 1/8 the mile info he needed and could still race without packing a chute. He got pretty good at dialing the car that way. Lol.


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Re: Excessive braking calculation? [Re: SportF] #2736402
01/25/20 06:27 AM
01/25/20 06:27 AM
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Aurora, Colorado
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If you have the speed at 1,000 ft, you can calculate the average breaking G-Force in the last 320 feet.

Example Initial velocity @ 1,000 ft (estimate) 170 MPH
Took time to go from 1,000 feet to 1320 about 1.441 seconds
Average deceleration would have been about -1.1762 G? That seems pretty hard braking, but if he was just 160 MPH at 1,000 ft, that is only -0.5435 G ?

Here is the calculator I found:
https://www.omnicalculator.com/physics/acceleration

Re: Excessive braking calculation? [Re: 451Mopar] #2736413
01/25/20 09:22 AM
01/25/20 09:22 AM
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Minn
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SportF Offline OP
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Well, there is some cool numbers. But, don't have the speed at 1000 foot, just the number that suggests a total run of 170mph.

Another interesting number on the slip was his 60 foot time of 1.27. A relatively soft launch for that kind of ET and total speed.

Thanks for all the inputs.







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