A Vintage Design Question

[gary_in_neenah]

OK guys, put on your Thinking Caps and see if you can answer this one. This is a picture from a Vintage Show a couple of years ago that I attended. It's a 69 Arctic Cat Panther with a 19 Horse Rockwell JLO. This was the exact same sled that my Dad had delivered Christmas Eve 1968, our families first snowmobile.

Here's my question (s) When did the manufactures move the Chaincase to the right hand side and add the shaft to connect with the secondary. Did they all make the change at about the same time (year?)and what was the purpose of the having the chaincase on the left? I know a lot of the sleds of that era had the engines much further back on the chasis and having a shaft transferring the power would not have been possible. But that wasn't the case with the early Cats as they had the engine way forward as in this picture. Any thoughts? First hand knowledge? Wild guess?

 

[Team Elkhorn]

I believe Cat started putting the chaincase on the right on their redesigned models in 1975. But left it on the left on their older models (Panther and Cheetah) through the '70s. When they redesigned the Panther in 1980, they finally moved the chain over to the right.

 

[snoluver1]

Well, this falls under the "wild guess" category but I would think they were originally on the left because there was no need to put them on the right. Any time you change drive direction and add shafts/bearings/gears/rotating mass, etc, your going to get frictional losses and take more power to get everything turning. Moving the case to the right side may have been necessary as sleds got bigger and more powerful. The secondary clutches got bigger and machines required better brakes. With the addition of disc brakes with a large rotor and a big caliper, they needed to spread stuff out and balance the weight of all those parts more equally. Also, I think the use of a jackshaft has a lot to do with belt life and drive line vibrations. As the engines got more powerful they flex more under load, and the jackshaft allows the secondary to "float" a bit.

 

[skiroule]

I really have no idea but I’ll throw out a couple of things just to provide some humor for the mechanical engineers. I agree with Snoluver1 (which should make him nervous) in that weight distribution and strength figured in.

When the entire assembly was integrated into the chaincase, it took all the loading on a very short shaft in a single assembly. If you think about side loads, having a longer cross-shaft would seem to handle the loads better because the bearings were separated over a distance, providing some mechanical advantage. This may have been driven by the fact that the engines were becoming more powerful and increasing these loads.

The other thing (and this is kind of off the wall) is that when the driven clutch was mounted on the inside of the chaincase, as most were, it had to be located above the tunnel. With the jackshaft it could be mounted lower on the outside of the tunnel, thus lowering the center of gravity.

As far as years, I don’t think everyone went at once but I’m pretty sure that by the late 70’s the major manufacturers had adopted the jackshaft approach or were heading in that direction.

 

[gary_in_neenah]

Thanks for the input guys it very well could be "all of the above". I imagine there was a day when an engineer had an Aha Moment and said, "we'll move this over there and put that down there" and we'll go faster and further than the other guy.

 

[polarisrider1]

Space or the lack of? Not really sure

 

[bearrassler]

I think a lot of it had to do with the engine horsepower, as the horsepower increased the jackshaft helped control the torque of the engine. A vintage guy that I know has a 68 Panther with a 600 Hirth that has a jackshaft, and he also has a 1965 Polaris Mustang that has a jackshaft. Most of them changed in the late
70's as Skiroule said above.