How to figure rollout
02-25-2004, 11:13 PM
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How to figure rollout
I know we have talked about this before but too lazy to search.
How can I figure my car's rollout?
How can I figure my car's rollout?
02-26-2004, 08:55 AM
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Re: How to figure rollout (REDGAR)
Ugggg..
Not sure if this will help, but I know it has to do with WHERE you stage, front tire height, and VRT (Vehicle Reaction Time....)..
I think these are all factors... However, it may just be where you stage & front tire height.
Not sure if this will help, but I know it has to do with WHERE you stage, front tire height, and VRT (Vehicle Reaction Time....)..
I think these are all factors... However, it may just be where you stage & front tire height.
02-26-2004, 09:00 AM
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Re: How to figure rollout (YO-EL)
I would have to think that the vehicle setup might have an impact. I thought I saw a formula but cannot remember where
02-26-2004, 11:16 AM
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Re: How to figure rollout (REDGAR)
02-26-2004, 11:49 AM
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Re: How to figure rollout (REDGAR)
When I first saw the question, I thought ou were looking for an answer in inches. Now, it looks like you're looking for a time, to set up a practice tree. That link, MMarquez, posted is super. I wish I had the hardware to duplicate that method. Thinking in inches, these thoughts come to mind. They relate equally well to time as they do distance. Front tire diameter affects rollout. It can be altered with air pressure changes. Your rollout will vary from track to track, if not day to day at a given track. One big varible there, is the height the photo cells are mounted. The higher the beam, the more tire that passes through it from "break" to "make". NHRA has a spec for this, but there is a tolerence in that spec. The higher the beam, the longer the rollout. And drag racing is a simple, "stab and steer" sport. HA !
RACE ON!!!
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02-26-2004, 10:40 PM
#7
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Re: How to figure rollout (CFI-EFI)
...One big varible there, is the height the photo cells are mounted. The higher the beam, the more tire that passes through it from "break" to "make". NHRA has a spec for this, but there is a tolerence in that spec. The higher the beam, the longer the rollout.
And don't check the beam's height AT the photo-cell/laser; if the track has a 'dip' in the groove (where the tire ACTUALLY SITS), this means the beam 'sees' an even WIDER 'slice' of the tire.
Good point, CFI-EFI !!!
02-26-2004, 11:29 PM
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Re: How to figure rollout (Glensgages)
...One big varible there, is the height the photo cells are mounted. The higher the beam, the more tire that passes through it from "break" to "make". NHRA has a spec for this, but there is a tolerence in that spec. The higher the beam, the longer the rollout.
Few racers understand this important factor; that the 'height' effects the 'chord' (math/engineering-term), or 'slice-across' the tire that the beam 'sees'.
And don't check the beam's height AT the photo-cell/laser; if the track has a 'dip' in the groove (where the tire ACTUALLY SITS), this means the beam 'sees' an even WIDER 'slice' of the tire.
Good point, CFI-EFI !!!
Few racers understand this important factor; that the 'height' effects the 'chord' (math/engineering-term), or 'slice-across' the tire that the beam 'sees'.
And don't check the beam's height AT the photo-cell/laser; if the track has a 'dip' in the groove (where the tire ACTUALLY SITS), this means the beam 'sees' an even WIDER 'slice' of the tire.
Good point, CFI-EFI !!!
But for the typical foot braker like myself, I think that the variance in human reaction time is the bigger variable. Enough that you can pick a working roll out based on your own tires. I really do believe in a statistical model for the HRT and getting the distribution as tight as possible (consistency) is the hardest part. :cheers:
02-27-2004, 08:19 AM
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Re: How to figure rollout (MMarquez)
But for the typical foot braker like myself, I think that the variance in human reaction time is the bigger variable.
Foot-brake racing isn't nearly as tight as 'box-racing', where racers routinely change 'delay' a few thousandths for lane variance.
Where ANY racer, foot-brake/hand-shake OR 'box'-racer, will see wider variances is going to various tracks, where timing equipment set-up, and even SYSTEMS, vary...
Enough that you can pick a working roll out based on your own tires. I really do believe in a statistical model for the HRT and getting the distribution as tight as possible (consistency) is the hardest part. :cheers:
Set your practice tree with .325-seconds of roll-out, and religiously practice this technique. You should soon be in the .51-.53 range.
Once THIS is accomplished, work-on various things (tire PSI, launch RPM, chassis-squat, converter, gearing, and 'WHERE' you stage) to get the CAR'S Reaction Time into that .325-second window.
02-27-2004, 07:02 PM
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Re: How to figure rollout (MMarquez)
But for the typical foot braker like myself, I think that the variance in human reaction time is the bigger variable.
RACE ON!!!
02-27-2004, 07:41 PM
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Re: How to figure rollout (CFI-EFI)
But for the typical foot braker like myself, I think that the variance in human reaction time is the bigger variable. I agree. But both RTs have to be addressed. *I* have my spot on the tree. How accurately *I* hit that spot, is my HRT. If you read my response under the thread, Where Do You Stage, or something similar, I wrote that I stage, "where I have to be". Case in point. I like to stage as shallow as possible. This works pretty well at my home track. At the NHRA Division 7 Bracket Finals in Tucson, last fall, a new track to me, I couldn't cut a light. My first 4 RTs were, .051, .049, .059, and .043. That reflects a difference of .010, which is made up in my HRT and VRT, combined. The varience isn't too horible, but the RTs were too slow. I decided to adjust my VRT by bumping in. My next 2 RTs were .012 and .012. I was confident I had the VRT under control. To me, it is much less disruptive to alter the position of the car than it is your focus on the tree. Of course, positioning of the car is subject to human error, too. Two cents worth from a foot braker.
RACE ON!!!
RACE ON!!!
Very good "foot" work! And you are obviously a skilled racer to make the correction. :D
Because you were so consistent that was a good move. If your RTs had been for example .500, .530, .510, .520 then staging a little deeper wouldn't have done anything but put you more at risk for redlighting especially if you are used to shallow staging.
I always shallow stage so that my RTs are reproducible leaving the main variable to be my HRT. I need more practice as I am the weak link. However recently at a Texas Muscle Car Club Challenge while staging / torque braking my car crept forward just a bit. I was able to make a slight adjustment in my internal timing and was able to cut a good light and get the win.
One last comment on RT philosophy since we haven't mentioned it is to run your own race. I cost myself a win by trying to "push it" and blow out the other driver off the tree. Instead of cutting a good light like I had been that day I ended up redlighting and took myself out. I guess like you said, it's better to stay in your rhythm. :cheers:
02-27-2004, 07:55 PM
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Re: How to figure rollout (MMarquez)
One last comment on RT philosophy since we haven't mentioned it is to run your own race. I cost myself a win by trying to "push it" and blow out the other driver off the tree. Instead of cutting a good light like I had been that day I ended up redlighting and took myself out. I guess like you said, it's better to stay in your rhythm. :cheers:
RACE ON!!!
