Roll out consistancy

[Casey Miles]

This past weekend at Rockingham, I personally couldn't hit the tree with both hands. So during the rain delay I went out with a ruler and measured the roll out to be 8 inches . It would be nice if NHRA would and should keep the roll out consistent with a specific number that they should keep at every points race. Make it the same no matter where you race.

Casey Miles
248H Stock

[James Perrone]

Casey the problem is you drive with 3 feet.
Most of us use 2. Lol

[Jeff Stout]

I thought 8 was short. Should be good lights or alot of red lights. I thought we set ours at 11

[Lenny5160]

Originally Posted by Jeff Stout

I thought 8 was short. Should be good lights or alot of red lights. I thought we set ours at 11

There's more to it than just measuring the distance between the two beams with a ruler.

It's a 22" wheel rolling 11" between beams, and that is set by adjusting the distance between beams, height of the beams, the width of the actual beam of light, etc.

[Greenlight]

Cut and pasted from Portatree's Timing System Installation Instructions

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A Drag Track Starting Line must be setup accurately so that left and right lanes have the same performance level. When a race vehicle leaves the starting line, it must leave from the same position every time and both lanes must have the same starting beam locations. The vehicle starts the timing clocks when the front tire rolls out of the stage beam (stage light on the tree goes out). The vehicle’s tire must rollout of the stage photo cell beam in the same manner and position for both lanes every time.

In order to setup an accurate starting line, you must measure how far the vehicle’s tire rolls out of the staging beams and you must set the photo cells and light sources so that the rollout is equal in both lanes. This guide will give you insight into how rollout can be changed to meet the accuracy required for any drag track layout.

Rollout is affected by the height of the photo cell beam off of the track surface. The photo cell beam should have a consistent height off of the track surface all the way across the track. Photo cell beam height can be measured by finding the beam center and sliding a triangle (30 – 60 degree) under the beam and marking the point where the beam is blocked. The starting line beam height should be 2 inches off of the track surface. Diagram 1 will show you how a triangle is used to determine the beam height.

Measuring the rollout of a wheel through the beam should be tested with a rollout wheel. The rollout wheel should be 24 inches in diameter and of solid construction. A trailing arm should be attached to the axis of the wheel and should have a marking block on the opposite end for placing on the track surface and marking beam position. Diagram 2 shows the construction of a rollout wheel and Diagram 3 shows a rollout wheel in use.

In order to simplify the procedure and finish your job with accurate results, only work on one beam at a time. We recommend starting with the stage beam first. The rollout should be tested in the racing groove on the track surface. We like to test the rollout in several locations but rely only on the results taken in the groove. The rollout wheel should be rolled into the beam in the direction of travel of the vehicle. When the beam is blocked, a mark should be placed on the track surface. The wheel should be rolled in again until the beam is unblocked and again the track surface should be marked. The distance between the two marks should be 12 inches but can vary either way be ¼ inch. It is always best to get the best accuracy possible, but the last little bit can take many hours of work..

In order to adjust the beams for rollout, you must raise or lower the light source and or photo detector. You may also have to limit the light source or detector viewing area. This can be done with light shades or screens or even duct tape. We do recommend that the manner in which the light source is blocked off be a permanent block.

After the stage beam has been positioned and the rollout has been measured and adjusted, the prestage beam can be tested. Position the prestage beam 7 inches before the stage beam. Measure the
beam height using a triangle as performed on the stage beam. When you are working on the prestage beam height, it is best to block or shut off the stage beam light source or reflector. You must now establish the prestage beam height and test the rollout with a rollout wheel. When you have the rollout set at 12 inches, you can now test the distance between the prestage and stage beams. Unblock the stage beam light source and make sure that there is no crosstalk between the prestage and stage photo detectors. This is done by going over near the light sources or reflectors and blocking each light source separately to make sure neither light source has an effect on the other. We usually take a 4 inch square object and move it through the beams at the light sources or reflectors. This will immediately tell if there is any crosstalk.

The rollout wheel should now be placed in the racing groove and should be rolled into the prestage and stage beams. Each time a prestage light or stage light goes on or off on the christmas tree, make a mark on the track surface with chalk. Roll in - - prestage on - - mark track - - roll in - - stage on - - mark track - - roll in - - prestage off - - mark track - - roll in - - stage off - - mark track. Take your ruler and measure the distance between marks and you should have 7 inches - - 5 inches - - 7 inches. If you have done your previous work correctly, then these measurements should be obtained.

The layout of your entire track can now begin. The starting line is the most difficult to setup and must be square and true with the rest of the track and photo cell layout. If you know where your stage beam line is located due to past surveying, then the rest of your track can be measured per our track layout drawing.

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[1347]

I thought roll out being inconsistent from track to track was just another part of making adjustments as a class racer. In D1, Cecil is looser than any other D1 track, which is why people put smaller front tires on, bump, go higher on 2 steps to compensate. It would be great in a perfect world to have every track the exact same, but it isn't, and I'm sure many people who have raced all over the country have good data of which tracks are better or worse than others.

[Jeff Stout]

Originally Posted by Lenny5160

There's more to it than just measuring the distance between the two beams with a ruler.

It's a 22" wheel rolling 11" between beams, and that is set by adjusting the distance between beams, height of the beams, the width of the actual beam of light, etc.

We used a bicycle wheel and front fork with handlebars. With handlebars resting on ground that was our reference to measure. Stage beam on and roll forward to get stage beam off. Would be around 11 inches.

[Mike Pearson]

Originally Posted by Casey Miles

This past weekend at Rockingham, I personally couldn't hit the tree with both hands. So during the rain delay I went out with a ruler and measured the roll out to be 8 inches . It would be nice if NHRA would and should keep the roll out consistent with a specific number that they should keep at every points race. Make it the same no matter where you race.

Casey Miles
248H Stock

I didn't notice anything being way off on my reaction times at Rockingham last weekend. I did screw up first round but that was just me missing the tree completely. Happens once in a while. The guy in the other lane was .001 so he wasn't complaining. Other than the bad run my trees were between .00 and .30 which is OK for me. I did chip it up a bit to get to the .00 but again that is the norm. maybe you were just off an bit that day. I have had those days.

[M Brand 505B]

The roll out was loose. Had to jack up the rpm by about 600 and raise the front tires 20# from Norwalk.

[HR9121]

I wasn't there but typically I run close to the same set up there as I do at Cecil County.