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Track VS Power

What makes a sled go through the steep and deep

Published online: Feb 09, 2003 Feature Steve Janes
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If you want to get five different opinions on track length/track speed, ask the same question to five different snowmobilers. It's that simple. And the answer will likely make the same amount of sense as asking your basic argument-starting questions-who makes the best snowmobile.or in more general terms, what constitutes a beautiful woman-blonde hair, brunette, long legs, big.well, you get the point.
It wasn't 10 years ago when track length/track speed wasn't even questioned, let alone a question of contention. When the longest of our long tracks was still around 136 inches, there wasn't any contrast with track lengths. Track speed was only based on engine size-more power, more speed. Everything else was relative. Once we broke out the 141s, the 144s and finally the 151s, then track speed started being discussed. But lately, with the 156s and 159s coming out of the woodwork, we now really have options to consider.
Matt Hasara, general manager at Alpine Powersports, Lindon, UT, told us earlier this year that if we wanted to start a good fight, just get a group of sledheads in a room and ask what makes a snowmobile work in deep snow.
"I like riding small snowmobiles with shorter tracks," Hasara explains. "I like to spin the motor at 10,000 rpm. That translates into rotation speed." Hasara says his preference in riding styles leans toward smaller snowmobiles that are more maneuverable. He says he wants to feel like he's working it, not just hanging onto it. But then, he admits, this year he'll spend most of his leisure time aboard a Cat M1 900. "It's what my customers will be riding. It has great power and a great feel to it."

Stoking The Fire
To consider what makes a snowmobile work well in deep powder, you have to balance six other needs-flotation, hookup, approach angle, power, momentum and maneuverability. After all, the concept of track speed in relationship to mountains sleds inevitably leads to "what will break trail through the steep and deep."
So let's consider each of these six factors.

Flotation-It only makes sense that the bigger the surface area, the greater the buoyancy in snow. On flotation alone, the track that puts the greatest amount of footprint in the snow will always be the best track. But then, we're not just floating through the snow. Flotation only goes so far in this equation. You also have to factor in the per square inch weight factor with flotation. If you have 700 square inches of track surface on the snow packing a 600-pound sled (with fuel and snow packed into the suspension) and a 200-pound rider, you have 1.15 pounds per square inch. But if you have 800 square inches of track surface packing a 600-pound sled and 150-pound rider, you only have .94 pounds per square inch. The longer the track, the more you decrease your square inch weight. This is good going over a flat meadow, but may not be so good going up a steep slope.
Hookup-The actual movement of a snowmobile is generated by the surface of the track either rolling on or pushing off of snow. On hard pack surfaces, the faster the track is actually rolling, the faster the snowmobile is likely to move. Track speed means everything here. In powder conditions, the surface of the snow is very granular. A flat track would spin out. The track actually needs to grip a bunch of snow to push off to generate speed. The greater the amount of snow that can be pushed (through deeper lugs and/or larger contact area), the greater the snowmobile propulsion through the powder.

 Approach Angle-The best snowmobiles tend to run "on top" of the snow rather than through the snow. It's up to the approach angle of the track to get most of the snowmobile out of the snow to eliminate drag (thus increasing flotation). Some snowmobile tracks have a tendency to "trench" rather than climb on top of the snow. Rolled chaincases have gone a long way to improve the track approach and get the weight of the sled up on top of the snow.
 
 Power-Let's face it: it takes a certain amount of power to turn a track at any given speed. The more resistance on the track, the more power required to turn it at that given speed. The greater the mass (size of track) and the greater the hookup (lug size) the greater the resistance. A 440cc snowmobile may have the power to adequately turn a 136-inch track with 1.5-inch lugs at a track speed of 60 mph. But if you throw on a 144-inch track with 2-inch lugs, your track speed will likely decrease by 10 percent or more. A 156- by 2-inch track may decrease your track speed by 25 percent.

Momentum-When you're busting trail in deep snow, momentum is everything. After all, if you were to place your snowmobile in deep, dry snow, regardless of horsepower or track size, and try to start out from a dead stop, you would very likely just spin out. If you were to do the same on a steep slope, you would very likely just spin out. Yet in both situations, if you were already moving at a certain speed, your momentum would keep you on top of the snow and moving forward. Track speed that translates into momentum (if you have a long enough run at it), is a good thing. But we don't always get a long enough run when it comes to busting trail in ever-changing terrain conditions.

Maneuverability-Finally, it comes to having a snowmobile that is easy to control and enjoyable to ride. Some people would rather sacrifice a little flotation for an easier turning snowmobile. Others don't mind "wrestling a bull" if it gets them through the steep and deep. It may make for a great aerobic workout, but it can also wear you out early in the ride. It comes down to what a snowmobiler wants out of his/her sled.

Argument Begins
Some will say that it all comes down to the rider. With comparable power and clutching, a person riding a 136-144 will be able to go anywhere a person riding a 156-159 goes. The increased track speed of a smaller track would make up for the less flotation by increased momentum.
And the guys riding the larger track would respond: "We never see those shorter tracks breaking trail through the steep and deep. If you want to stay in someone's track all day, you might just as well stay on the trails."
Another important factor that plays into the track length/speed scenario is the actual snow density. In the wetter regions like the Pacific Northwest and Sierra/Nevada mountains, the snow contains a greater volume of moisture. This means it will pack tighter with less air. Some refer to it as Sierra Cement. In these conditions, track speed is much more critical that flotation. (It doesn't matter if you're riding on six feet of fresh snow if you're only sinking down six inches.)
Then, when you get farther inland in the dryer regions of the Rocky Mountains, the snow is a lot dryer and there is more air in the snow pack. Here, flotation is more critical. (Now riding on six feet of fresh snow means something-like having to stand up on your sled to see out of the powder.)
Another factor that plays into the argument of track speed/flotation is the shear strength of the snow-the heavier the snow (in density), the greater its shear strength. This means that the snow will hold its shape longer under greater pressure. An aggressive track will create greater propulsion if the snow holds its shape. If the snow is quick to give way to the spinning track, then track speed has less importance than flotation.

More Power
One thing has been constant throughout the historical progression of mountain sleds-power is always a good thing.
If you have 10 different sleds highmarking a steep slope, the sled with the most power, regardless of track width/length is most likely the one getting farther up the face. It's always been that way.
However, if you're boondocking through deep snow in a variety of terrain conditions, that same sled is most likely to be the one creating the biggest holes and creating the most work for the group to dig out. An example here would be to compare the riding efforts between a Vmax-4 and a Phazer. There is no comparison to the power.but most would rather be riding the Phazer (on top of the snow) than digging out the Vmax. After all, power is greatly neutralized when you're crawling between trees through the deep fluff.
Hasara describes two types of mountain riding-the kind where the snow is deep on high elevation mountain plateaus, and the type where the slope is more vertical. For Hasara, the first type of riding requires long tracks for greater flotation. The second type requires more power and track speed. Engines that use rpms to produce horsepower like shorter tracks to produce more track speed.
Over the past five years, more emphasis has been placed on track technology. Tracks have gotten longer and track profiles deeper. Manufacturers have experimented with track width, pattern and length, hoping to find the right combination for today's snowmobiles.
Power has always been and will continue to be an important factor. And hopefully, the weight issue will keep new snowmobiles under the 500-pound size. As technology changes with new suspensions improving maneuverability, manufacturers will continue to search for balance between power, flotation and hookup.
After all, some prefer blondes with long legs, others prefer big twins and long tracks.