Rotating weight reduction

[Cinno]

Really Cinno, you may have a good understanding of physics principles but you set up this problem with the wrong assumption that the track is coupled to snow and no slip is occurring. Your logic may be true if you're ripping across a lake at 60 and punch it, but not from a dead stop in deep snow.

In reality, the sled moves forward because of the amount of snow the track is propelling backward. The more snow thrown by the track, the faster the sled will move. So the faster the track accelerates, the better and more responsive the throttle will feel.

Its easier to discuss the rotating mass issue by itself by setting other variables constant (traction). Once that is settled we can move on. Shall we? OK.

Your statement "In reality, the sled moves forward because of the amount of snow the track is propelling backward. The more snow thrown by the track, the faster the sled will move". It sounds like your saying its "jet thrust" like water through a nozzle. I don't believe that. I would simply set the traction coefficient somewhere between 0 to 1. 0 = no traction and 1 = maximum traction. Maximum traction couples all the force from the track to the snow. The sleds reflected inertia to the motor is rotating inertia of all the drive train components plus a portion of the total weight of the sled based on the traction coefficient. So the effect of a 5 pound reduction in track weight maybe "felt" by the rider if the traction coefficient drops significantly . So you get that zippy feeling in soft fluffy snow, lower lug heights, shorter length tracks. SO the math proves it! Can we be friends again?

So my opinions on track selection. longer, taller lug tracks are heavier so you give up inertia to gain traction. However increasing the pitch reduces weight so you get back a little zippiness without giving up traction. Some believe the longer pitch reduces the fracturing of the snow which gives better traction.

Another thing when Polaris raises the gear ratio on longer length and taller lug tracks the reflected inertia drops even though the tracks are heavier because of the 1/gear ratio squared function. Any comments from those that have changed ratios without changing the tracks and how that effects the zippiness?

Cinno

 

[tdblakes]

...

So my opinions on track selection. longer, taller lug tracks are heavier so you give up inertia to gain traction. However increasing the pitch reduces weight so you get back a little zippiness without giving up traction. Some believe the longer pitch reduces the fracturing of the snow which gives better traction.

...

Cinno

No, not like jet propulsion as there is no nozzle... just a little logical application of newtons 3 laws of motion. That coefficient of traction is always closer to 0 when you are on and off the throttle in powder. You are right that the pitch, lug geometry, and lug height play a key role in its value... Thank you for finally agreeing tho!

 

[Indy_500]

Polaris 155 Series 5.1: 46.25lbs
Polaris 155 Series 6: 44lbs
Polaris 156 Series 7: 49lbs
Camso 156 X3: 56lbs
Camso 156 X3.2: 51lbs
Camso 156 CE 2.5: 51lbs
Camso 154 2.5 Peak: 56lbs
Camso 155 Conquer:
Camso 154 Conquer:
Arctic Cat 153 2.6 PC: 57lbs
Arctic Cat 153 3 PC: 53.8lbs


Polaris 163 Series 6: 49.5lbs
Polaris 162 Series 7: 53.1lbs
Camso 162 X3: 58lbs
Camso 162 X3.2: 54lbs
Camso 162 CE 2.5": 55lbs
Camso 162 2.5 Peak: 59lbs
Camso 162 Conquer: 45lbs
Camso 165 Conquer: 42.5lbs
Arctic Cat 162 2.6 PC: 59lbs
Arctic Cat 162 3 PC: 56.2lbs
Ski Doo 162x16x2.5: 60.2lbs
Ski Doo 162x16x3: 59lbs
Ski Doo 165 3: 49lbs

This needs to be stickied

 

[Teth-Air]

Okay, I have a couple lugs missing on my 2015 163 2.4" lug track. This thread makes me want to cut off every second lug so I can experience a couple things. First thing will be what the sled feels like with a track that is way lighter and secondly what a track feels like it has a pitch of nearly 6 inches. I have a spare newish track on the shelf so it would be an interesting experiment.

I am pretty sure I would be disappointed but I wonder if there would be anything I liked about it.

 

[himarker]

It would be interesting to see what happens. I think with that kind of space between lugs it may be detrimental to overall performance but I'd be willing to bet that there will be a noticeable increase in responsiveness. Keep us informed.


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[summ8rmk]

Okay, I have a couple lugs missing on my 2015 163 2.4" lug track. This thread makes me want to cut off every second lug so I can experience a couple things. First thing will be what the sled feels like with a track that is way lighter and secondly what a track feels like it has a pitch of nearly 6 inches. I have a spare newish track on the shelf so it would be an interesting experiment.

I am pretty sure I would be disappointed but I wonder if there would be anything I liked about it.

Do it!
Report back

GS6

 

[olymon]

I know this really doesn't apply to the big tracks and big power, but I did something like this on a 136" x 1 1/4". It was on a phaser and I wanted to let it move the track easier. I cut at least half of the lugs off in a pattern. A lot lighter, rolled easier and really bit in the snow.

Making JIS screws into junk

 

[goridedoo]

This thread sucks. Somebody take 2 stock identical sleds, and put light rotating stuff on one, make some comparisons and take some video, until then all the fancy math and theorys are worthless, and your arguing is pointless. Thanks

 

[Cinno]

This thread sucks. Somebody take 2 stock identical sleds, and put light rotating stuff on one, make some comparisons and take some video, until then all the fancy math and theorys are worthless, and your arguing is pointless. Thanks

So were are supposed to stop talking about something we are passionate about because you don't like it! I for one have learned something in this thread. We can all learn from each other If we bother to listen. If you don't like it go start your own thread . Cinno

 

[goridedoo]

So were are supposed to stop talking about something we are passionate about because you don't like it! I for one have learned something in this thread. We can all learn from each other If we bother to listen. If you don't like it go start your own thread . Cinno

I really dont actually care, argue all you want

 

[omernikski]

Here is my primary after adding the ZRP cover and having Indy Dan balance it.

Seems like a significant amount of new holes. Might want to consider having it balanced.

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I'll get it done eventually. I had Indy Dan build the motor 2 years ago and only put 7 miles on it since then. I'm gonna have both clutches balances and the primary recut

 

[omernikski]

I built most of my sled around battling rotating weight, and thankfully I didn't start this thread, reminds me of Christmas dinner with the family

 

[omernikski]

Either way, still good stuff to read

 

[omernikski]

After I put 7 more miles on it this year I'll part it out lol

 

[Teth-Air]

Do it!
Report back

GS6

It feels like I am on a rooftop and you are saying

"JUMP , JUMP!"

 

[SNWMBL]

So our engineer is saying that reducing track weight does not make much difference in acceleration/responsiveness, and that reducing the sled weight anywhere else(the same amount as a lighter track) will give equal performance gains?

How is it then, that you can put 20" wheels on a 1/2 ton gas truck and immediately notice a significant performance loss, but keep the factory 16" rims and put a few sandbags in the bed(equal to 20" wheels weight difference) and you'll never know they're there?

Or go strap a 10 lb weight to your bicycle seat and ride it, then put a 5 lb lead weight on each wheel and go for another ride. Still think rotating weight only makes a 1.6% difference?

I don't think Cinno is an engineer, just someone's alter ego that's throwing absurd math out.

 

[Cinno]

So our engineer is saying that reducing track weight does not make much difference in acceleration/responsiveness, and that reducing the sled weight anywhere else(the same amount as a lighter track) will give equal performance gains?

How is it then, that you can put 20" wheels on a 1/2 ton gas truck and immediately notice a significant performance loss, but keep the factory 16" rims and put a few sandbags in the bed(equal to 20" wheels weight difference) and you'll never know they're there?

Or go strap a 10 lb weight to your bicycle seat and ride it, then put a 5 lb lead weight on each wheel and go for another ride. Still think rotating weight only makes a 1.6% difference?

I don't think Cinno is an engineer, just someone's alter ego that's throwing absurd math out.

Well your changing the overall drive train gear ratio of the truck by changing from 16" to 20" wheels ! This increases the reflected inertia of the complete weight of the truck back to the engine by 1.56 so if had a 5000 lb truck it would feel like 7800 lbs when you accelerate it and makes first gear actually increase by 20/16 or 1.25. Doubly bad!

On your second example:

If you distribute the 5 lbs per wheel (2.5 lbs 180 deg apart so it doesn't wobble) x 2 wheels, total of 10 lbs then yes it will feel the same as 10 lbs on the seat. TRY IT!

By feel I mean accelerate, this does not include gyroscopic effects.


You did mean 16 to 20 total diameter change of the tire or did you mean 16 to 20 wheel with a lower profile tire so the diameter did not change?

And by the way I'm a basic member so once this thread hits 100 I'm out it, so FLAME away.

Cinno

 

[SNWMBL]

I said wheel, not tire. The wheel thing is metal thing inside the rubber thing, in case you didn't know. Therefore outer diameter does not change.

And yes, you absolutely notice the weight at the wheels, same with the bicycle.

You can argue math all you want, but you're wrong. Real life experience > engineering degree.

 

[Dbook]

Ever put a 4 oz flywheel on a dirt bike before?

 

[Cinno]

I said wheel, not tire. The wheel thing is metal thing inside the rubber thing, in case you didn't know. Therefore outer diameter does not change.

And yes, you absolutely notice the weight at the wheels, same with the bicycle.

You can argue math all you want, but you're wrong. Real life experience > engineering degree.

The outer diameter does change a little (~+0.75") on a typical larger diameter wheel with a lower profile tire. If you felt any deceleration effect it was due to the diameter change and its effect on reflected inertia to the motor and the torque change. Not the minor change in inertia of the wheel. 3/4 inch dia. change on the tire will add about 250 lbs to the reflected inertia on a 5000 lbs truck, about the same as adding an additional passenger! Thats what science and math does, points you in the right direction and away from the snake oil! I'm out of here, good luck and I hope you enjoy living in a fairy tail land where the sky is pretty shade of purple.

Cinno.