The Bed Of Nails Analogy: Too Many Studs?

Bed of nails analogy to snowmobile stud quantity

 

The bed of nails is a common analogy for running too many studs in your track. Too many studs in the track will cause less traction, like if you lie down on a bed of nails. While it does paint a good picture in your head, the math behind it shows it's an apple to oranges comparison.

 

There is not enough real estate on today's tracks to over-stud a machine to lose traction when it comes down to it. Don't get us wrong; you can over stud your Mom's lower horsepower 550 fan machine. Still, any 800+ two-stroke or four-stroke turbo, there simply is not enough room to overstud with our recommendations.  

 

Let's break it down with the most common track. A 137" x 15" track has a surface area of 2055", including the windows. Instructions from the University of Pittsburgh on how to build a bed of nails require a 56" x 26" piece of wood with a surface area of 1456". The recommended amount of nails for the wood is 1375, and the maximum amount of studs we recommend running on a 137" track is 192… The bed of nails has a surface area of about 1.06" per nail. The snowmobile track has 10.7" of surface area per stud at the highest quantity. At 144, it goes up to 14.3"!  

 

Now let's look at weight per stud and nail. Let's assume our rider is 200lbs and the snowmobile's wet weight is 500lbs for a total of 700lbs. The same rider lays on a bed of nails; at 1375 nails, each nail would be supporting about 0.15lbs. Here is where it gets fun that 192 studs in the track, only about 40% are on the ground at a time, bringing it to about 76 studs. Each stud is supporting 9.2lbs. That doesn't look like that big of a difference, only 9lbs, but when you divide 9.2lbs by the 0.15lbs, you realize it's over 61 times greater than the weight of the nail. At 144 studs, the number goes to about 12 and over 80 times greater.

 

Are we having fun yet? Now let's look at horsepower, the most significant factor! Let's assume 170 hp two-stroke for now, and we somehow turned the bed of nails into a track. 1375 nails with only 40% on the ground come to 550 nails. That put's each nail handling at 0.31 HP. With the 192 kits, you are at 1.77 HP per stud. With a 144, that moves to 2.93 HP per stud.

 

While the bed of nails seems relatable, it's not the case with modern push-through studs and tracks. There were studs mounted to track plates in the old days, and you could load up tracks with hundreds of studs and get to that tipping point of losing traction. It is where the analogy initially came from. Those studs have long been retired from recreational use, and the bed of nails should follow!

 

Bed of nails source: https://www.pitt.edu/~dwilley/Show/NailBed2.html