Fastest Sled

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Why The Fastest Sled Doesn't Always Win

By Mike Adams
SnoGoer 1973

Itís lap time, not top-end speed, that puts you first across the FINISH

Snowmobile race fans ask at every race, "How fast are they going?" A windowed van containing an elaborate electronic speed trap answered this question at eight races in Maryland, New York and Pennsylvania last year. The "timing lab on wheels" clocked Ski Dooís 127.3 mph world record at the USSA World Speed Trials at Boonville, New York. Also, last February the "lab" had its lights focused for Larry Buarmanís record breaking 87.0 mph on the straights of the half-mile oval track at Marienville, PA. 

The speed trap uses intense spot lights to create two light beams perpendicular to the track. Electric eyes are used to detect when a snowmobile breaks the beams. The lights are placed 100 feet apart where the machines reach peak velocity on the straight stretch of an oval track.

The speed trap operates like this. When a snowmobile breaks the first beam, an electronic stop watch starts clocking. When the second beam is broken, the time required for the snowmobile to travel the 100 feet distance is recorded on the watch. The stop watch is actually a Hewlett-Packard frequency counter that digitally indicates the time required to travel the distance to 100/10,000 second. The time is then translated into mph within 0.1 mph accuracy. For example, if a sled traveled the 100 feet between the lights in 0.9226 seconds, it was traveling 73.9 mph.

The speed trials at Boonville, N.Y., are held on a two mile air-strip. The "time lab" positioned its lights 350 feet apart in the center of the air-strip, one mile from each end. The beams are placed 350 feet apart for speed trials rather than the 100 feet separation used for oval races to insure 0.1 mph accuracy at higher velocities. A sled accelerates one mile before reaching the timing lights. Its speed is clocked only over a 350-foot distance. It decelerates the remaining mile to the other end of the air strip where it receives refueling and minor adjustment. By USSA rules, it is allowed 30 minutes to complete a run through the trap in the opposite direction. The velocity of both passes through the trap are averaged to determine the final result of the "run." For example, if a sled turns 120 mph on its north-bound pass and returns at 130 mph on its south-bound pass, the final speed for the run is 125 mph.

The timing system can be assembled at an oval race in 45 minutes. Parked near the track with the timing equipment mounted inside, the van acts as the timing headquarters during a race. A phone line establishes communication with press and public address boxes. The van is equipped with its own power supply so it can be operated at races where a power line is not available. The system requires 15 minutes to disassemble.

Some interesting facts have been revealed by the "timing van." Women often go faster than men in a given class. The world record for Modified I of 75.7 mph was tied by Mrs. Geraldine Byrd of Redfield, N.Y. at the Boonville trials last February. Dorothy Mercer, the only woman on the Polaris racing team, established the Modified V world record of 109.2 mph. In oval races, a woman will often reach higher top-end speeds than the man who runs the same sled in a stock race the same day. However, the stop watch on board the van saves the manís ego. In the same cases the woman requires several more seconds to lap the track than the man. It seems the manís greater weight costs him a few mph on the straight stretch but allows him more commanding control of the sled on the turns.

On a half-mile track, some unexpected facts have been uncovered. Class A stock sleds generally turn faster top end speeds on a given day than B stock sleds. Class C stock rather than the more powerful D stock class are the fastest stock class sleds. Modified I machines, with few exceptions turn faster speeds on the straights than Modified II sleds. Modified IV machines, despite their smaller engines than the Modified V sleds, generally turn the fastest speeds of any class on a half-mile track. Only the increased weight of the larger engines can be offered as an explanation for this phenomena.

The fastest speed on the straights does not guarantee the driver a victory. It has been recorded many times that the first place sled is going several mph slower than the second place sled. It is true that the second place driver is pushing his sled to catch the leader. But more significantly, it is lowest lap time and not the fastest top end speed that wins the race. If the gearing or maneuvering of a sled is costing a driver seconds in the corners, he wonít win even if heís got 3 mph on the competition on the straights.

When two sleds race side-by-side to the line for a photo-finish, they appear to be traveling much faster than they were in earlier laps. Someone always runs to the van and says, "What were they turning that time? !" The answer is usually a speed several mph lower than those sledsí best performances in earlier laps. At higher velocities the sleds create more drag for each other and slow each other down by several mph.

The electric eyes uncover subtle drama that race fans would otherwise miss. During a race in Pennsylvania three weeks before the 1972 World Series, a competitor in Modified II was clocking turning 6 mph faster than the second fastest sled of the heats and semi-finals of the class. A two second superiority in lap time over all other competitors in the class proved he was not losing time in the corners. Yet in the feature race, his top speed dropped 8 mph and he appeared unable to secure second place. The speeds announced over the public address system alerted the fans to the sudden loss of performance. The driver admitted later that his friend who was fighting for first place in the race needed to place well in the race for the points to qualify for the World Series.

The timing van has discovered gross inaccuracies of some speedometers. At every race, somebody running a stock sled will walk to the van and complain; "You clocked me at 55 and my speedometer read 70...!" Anytime the track of a snowmobile slips on the snow surface, the velocity reading will be higher than the actual speed of the machine. Some speedometers are calibrated by their manufacturers to duplicate the actual velocity of the machines. Not all speedometers are inaccurate. The lights have found some speedometers to be within a few mph at speeds as high as 80 mph. However, anytime the track is slipping, the speedometer reading will be higher than the actual speed of the sled. END


Example of top speeds recorded by the lights during half-mile oval races, by USSA classes:

Class CCís MPH
Stock A
Stock B
Stock C
Stock D
Modified II
Modified III
Modified IV
Modified V
I 0-295


(Sleds travel counter-clockwise)


To me, the most significant factor is that they are all doing 35 mph in the middle of the turns. That's because, you can fight the "LAWS of PHYSICS" but you can not beat them.

In order to stay on the track they had to slow down!!!

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