Track extension math

[Dewaddict]

After fighting with an overly tight track when I did a 121 to 144 in extension I was thinking about the math while in my shop. I measured the axle to axle distance of the extension and it was exactly 12 in but the track is essentially a triangle in the way it travels to the rear of the sled because the top is at an angle. And the angle side is always longer. So if the flat side moves back 12" the top side would have extended 12 and 1/2" or maybe 13"? So in that respect instead of going from a 121 to a 144 I would have gone from a 121 to a 145 or 146, wouldn't i? I would think it would be closer to the 146" because if both the top and bottom of the track were extending straight back to 12" that would be 24" which would make it 145" extension anyways. That would explain the reason for the track being so tight.

 

[earthling]

As you extend the base (if I understand your description) the length of the slope will grow linearly with the length of the base, but not by as much. In other words, for every inch of length you add to the base you will add slightly less than that for the long (sloped) side of the triangle. This is because you are only changing the length of the base and the height is fixed. from 121 to 144 is 23" and the track is wrapped around the wheels so your extension for the base would have to be less than 12" to get the same fit.

 

[Ding]

Do what I did when this happened. I just swapped drivers to 2.86 pitch and ran a 146 track. Worked great. This was with a skid change and I couldn't go any further forward with the front mount. You can use an online tool to draw the shape and measure circumference. Or do it like I did and just use geometry (before the day of online tools).

 

[Stubbs]

I’d like to bring this back around again. I’m working on a project and looking for some input. The Cole’s notes version is using a Mono skid stretched out and I’d like to use the 146” track currently on the sled. I’m shooting for tipped up rails to maintain decent handling. The rear upper carrier wheels will be located in the stock 136” Mono II location. At this point I’m trying to decide between 121” rails with stock Tracks USA tipped up extensions, or go all out for custom rails. Any thoughts? I’m not new to stretching out Mono skids, I’ve done several over the years. I’m currently using a 136” Mono II skid wrapped in a 137” Rip II track on my Nytro. The 137” track was a touch long, but I had just enough track adjustment to make it work. My fear using the rail extensions designed to stretch to 144” will come up too short when using a 146” track. This decision has been keeping me up at night lately. Lol

 

[earthling]

If you imagine the tracks as circles, the diameters will be;

144/3.14159 = 45.836"
146/3.14159 = 46.473"
46.473-45.836=.637" difference in diameter, meaning you will need to find just over a half inch everywhere to make up the difference. Doesn't sound like too much to overcome, maybe start with oversize wheels if that's possible?

 

[Stubbs]

If you imagine the tracks as circles, the diameters will be;

144/3.14159 = 45.836"
146/3.14159 = 46.473"
46.473-45.836=.637" difference in diameter, meaning you will need to find just over a half inch everywhere to make up the difference. Doesn't sound like too much to overcome, maybe start with oversize wheels if that's possible?

Thanks for doing some math for me bud. I always run oversized wheels on my Mono skids. Larger rear wheels are an option, but I don’t want to take away from the tip up if I can help it. Hope you’ve had a good summer, and I’ll text you some pics of my latest victim. Lol

 

[earthling]

Thanks for doing some math for me bud. I always run oversized wheels on my Mono skids. Larger rear wheels are an option, but I don’t want to take away from the tip up if I can help it. Hope you’ve had a good summer, and I’ll text you some pics of my latest victim. Lol

Look forward to it. We almost have the attak back together so one less doo in the group and one more apex. Got the rails/brackets powder coated and the skid is back together with the shocks rebuilt all around so just looking for some free time to make a trip over to Arts for a replacement cooler.

 

[Ding]

I have learned that math will only get you close. I do all the math I can to start with, but then there is no substitute for mock-up and pre-fitting. Remember tracks can vary from nominal size especially in actual inner circumference by several inches. What should fit using math, sometimes doesn't and vice versa. Try it before you drill .

 

[earthling]

It’s not the math that’s wrong then, it’s the fact that the track is or may no longer be 146”. That should be easy to measure outside the sled.

 

[Stubbs]

I need to get the Nytro out of the garage and sold before the big Ape can come home and I start to measure anything. Lol