HEMI Technical Info

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CHRISTMAS TREE
The following dimensions are guidelines in timing equipment placement.
• Distance from start line to tree: 40 to 42-feet.
• Height of tree: 94-inches from ground to center of pre-stage bulb.

 LIGHT BEAM PLACEMENT
• Distance between pre-stage and stage: 7-inches. height=1-5/8" 
• Distance between stage and guard beam: 16-inches.  (13 3/8" Brockmeyer- Compulink ) 
• Height of 60-foot beam: 10-inches.
• Height of interval time beams, speed trap beams, and ET stop beam - all 5-inches.(5-5/8)
• All interval increments and quarter-mile finish lines are measured from the guard beam.

 ROLLOUT
• Height of beam approximately 1 9/16” adjusted as necessary (and possible) to provide 11½ to 12-inches of roll using standard dragster wheel/tire (22-inch diameter). Beam height must be low enough to accommodate 3-inch clearance rule as per NHRA Rulebook.
• NOTE: An 11½-inch rollout equal on both lanes may not be possible due to track crown. The single most important thing with rollout is that both lanes be as equal as possible 
NOTE : L.E.D. Bulbs effect rollout .03 to .04 secs -- deduct from your Rollout Time when practicing. .32 on incandescent is .28-.29 on L.E.D.’s ! 

OPTIONAL - additions to timing systems

AUTOSTART – The Autostart System will automatically start the Tree at a random pace within a given window. The starter flips the switch when both both cars pre-stage, activating the system. If one competitor stages and the other does not complete the staging process within 10 seconds the system will automatically red light that competitor. Once both cars have staged for 0.6 seconds, the Tree will come on between 0.6 and 1.4 (full tree = 0.6 to 1.1) seconds later, depending on the class. The system will vary the start sequence by randomly adding up to 0.2 seconds, preventing racers from guessing when the Tree will come on. The starter is able to stop the sequence if necessary, and can activate the Tree himself by over-riding if that is required.

CROSSTALK – This program allows the Tree to be fully shielded, but still allows drivers in Super Pro, Top Comp, and Top Dragster classes to cross-over. CROSSTALK functions by lighting the top bulb in both lanes at the exact same time. This allows both cars a direct hit on the Tree. The slower car’s Tree will continue counting down as normal. The quicker car’s top light will remain lit for the duration of the handicap, plus the normal 0.5 second, before counting down the second and third lights as normal. The driver of the faster car in a pair may cancel the CROSSTALK system by including an “N” behind their dial (example 7.85N). If you have any questions or do not understand how crosstalk works please consult with the Race Director. A dash symbol “-” will appear in front of the dial posted on the scoreboard (-10.05) to indicate that CROSSTALK is not on place. Drivers should check the score-board before staging. There will be NO re-runs for incorrect tree configurations.

SPLIT-TREE – The Bike/Snowmobile class is run on a Split Tree. Each rider can choose either a .4 Pro Tree or a .5 Full Tree. During time trials, riders will be split into two groups. However, during eliminations, the default tree will be the .5 Full Tree. Riders choosing the Pro Tree are required to place a “P” at the end of their dial (10.05P). A symbol will appear in front of the dial posted on the scoreboard before staging. There will be NO re-runs for incorrect tree configurations.

COURTESY STAGING –  As you stage your car, pull forward  until the first light (pre-stage) comes on. At that point, you should wait until the car in the opposite lane has done the same. When both cars have pre-staged, either one may then pull into the second beam which fully stages the car. Once the first car has staged, the second car has 10 seconds to pull into the stage beam. If it does not, the red light will come on in that lane, and the opponent will be given a single lane.  NOTE: The system registers a car as staged if the stage light is on for at lease 0.6 seconds. Therefore, be extra cautious when bumping into the lights.

DEEP STAGING – Some drivers prefer to pull into the beams so far that they turn off the pre-stage light. This procedure is illegal in certain NHRA classes (see rulebook). If you choose to deep stage, you do so at your own risk. 

TYPICAL ROLLOUTS - Time delay for car to react and rollout of stage beam

Jr. Dragster - Gas Motor .40 - .44 Seconds 
Jr. Dragster - Alcohol Motor (sm. front tires) .36 - .38 seconds 
Jr. Dragster - Alcohol Motor (lge front tires) .31 - .34 seconds 
Motorcycle .18 - .22 Seconds
Pro Stock Bike .24 - .28 Seconds 
Pro Stock Car .24 - .28 Seconds 
Super Comp Dragster .18 - .22 Seconds 
Super Stocker (3200 lbs) .30 - .34 Seconds 
Top Fuel -- Dragster / Funny Car .28 - .32 Seconds 

Calculation (Estimate Only): Weight of Vehicle / 10,000
 3200 lbs / 10,000 = .32 Seconds  This estimate does not work for vehicles that slip clutches excessively. 

The Christmas Tree 
1)-1963 for the U. S. Nationals 5 amber .5 delay
2)-1964 for the Winter Nationals 5 amber .5 delay + pre-stage/stage
3)-1971 Pro Tree Added 5 amber only the last was used - .4 delay to green
4)-1971 Tree --> 3 amber- sportsman .5 delay and Pro all 3 on both sides - then .4 to green
5)-2003 NHRA changed to L.E.D. ( reaction time decreassed by aprx .03 sec)
6)-2011 amber pre-stage/stage, replaced by blue and 4 used at charlett (4 Wide track)