November 20, 2008
building a Tunnel
When it comes to building a great mountain sled, too often snowmobilers overlook one important element that can either make or break a good powder sled … the tunnel.
Since the time and effort to replace a tunnel is rather significant, not to mention the cost, most snowmobilers opt to keep the stock tunnel and make changes all around it to cover some of its inadequacies.
However, at Timbersled in Ponderay, ID, they know that if you truly want a great mountain sled, then there are just some things that can’t be compromised … and the tunnel is often one of those things. On the 2009 SnoWest project sled, as we worked with Allen Mangum of Timbersled to design this year’s sled (a 2009 Yamaha Nytro MTX), one of the important ingredients to complement a Stage 2 Supercharger was a Timbersled tunnel. The combination of function and weight savings was more than enough to make this modification well worth the effort.
When you’re trying to make the most out of a Yamaha Nytro, there is certainly a lot of things you can do … but perhaps two of the most important basics are: increase power and decrease mass.
Finding more power in a four-stroke is easy to do. Bolt on a turbo or supercharger and away you go. But eliminating weight can be a little bit of a challenge. It’s not just a matter of figuring out what you can live without.
As you shed weight, you can change the handling characteristics, i.e., balance and weight distribution. You can also compromise structural integrity. So you better have a good plan to begin with.
Although there are a lot of impressive products being installed on this year’s project sled (that story will be coming in the next issue), we want to focus on the merits of changing from a stock tunnel to the Timbersled custom-built tunnel.
First, let’s look at the weight savings—we’re talking 18 lbs. coming off the sled even though we’re stretching it from a 153 out to fit a 162-inch rear skid.
The Timbersled tunnel features straight and smooth running boards which will provide superior flotation. The tunnel is one-piece, meaning there are no rivets holding it together. This provides a clean finish. The tunnel is also one-inch deeper than the stock tunnel, offering more clearance for the track.
Running boards and foot pockets are designed into the tunnel to provide better traction, rider grip and ease in eliminating snow build-up. The Timbersled tunnel is designed with a rear taper, meaning the back end of the tunnel is about 1.5 inches narrower than the front. (It’s amazing what 1.5 inches means when it comes to being able to avoid getting wedged into one’s own trench.)
There are also two distinct advantages to the taper: First, it gives the sled a real streamline look. Second, when you’re cutting a sidehill, the taper tends to keep the side of the sled out of the snow. You never get to the point where you’re losing traction because the end of your sled is dragging into the side of the hill.
The tunnel comes powdercoated in any color or unpainted with a semi-polished finish.
We asked Mangum if there is any advantage to powdercoating a tunnel, since it does add a little weight to it. “We find that snow won’t stick to a powdercoat finish nearly as quickly as it sticks to aluminum,” he explained. “Not only is polished aluminum hard to maintain (with a shiny finish), but with the snow build-up, it will actually be considerably heavier than a powdercoated finish.” The powdercoat finish is basically like covering your tunnel with a thin layer of plastic. “Snow doesn’t stick to plastic like it does to a cold piece of metal,” Mangum explained.
Also, when you can powdercoat your tunnel to match the paint scheme of your sled, it really gives it that custom look that sets your snowmobile off from other sleds.
Timbersled tunnels are hand built, starting from a flat sheet of aluminum. Mangum marks out the bends from a set of blueprints he designed and then sends the sheet to a shop in Coeur d’Alene, ID, which has specialized tools that can make unique bends. From there the tunnel goes back to Timbersled for some final cuts and drilling before being shipped to Post Falls, ID, for powdercoating.
Tunnels can be custom built for most popular brands of snowmobiles. The cost of the tunnel kit (which includes the tunnel, tube cooler, mountain bumper, gas mat, foot traction, suspension mounting brackets, bolt hole supporters, foot pockets, toe hooks, trailing arm mounts if needed, chaincase guards and other necessary parts and brackets for the model) is $1,575.
For more information about the Timbersled tunnel, call (208) 255-5644.