I feel like this argument is a moot point. Even if it's a 1.6% change most people can attest that 10lbs(1.6% possibly) is a decent change in feel on the sled. Nuff said.
Rotating weight reduction
- Thread starter Bauer112
- Start date
Where I ride the track is constantly slipping. 50mph track speed and 10 mph ground speed is par for the course. Unless I'm riding the trail which I assume we're not talking about?
What I'm really getting at is changing directions. Zig zagging in the trees, skis up then grab the brakes then WOT again, tipping the sled back and forth, etc. That's where the lighter tracks feel way more zippy. Quick is a good word. Heavy tracked sleds feel lethargic. They do generally climb just as high or higher in a straight line. But that's not what I'm looking for.
Well that's different then ! I agree that if the track is slipping on the snow then the tracks reflected inertia back to the motor is dramatically less. The effect of reducing track weight is much higher. The slip will also cause the secondary to up-shift faster further increasing track speed. All this must increase the zippy feeling. BUT does it actually make the snowmobile ground speed increase ?
My 2016 AXIS RMK feels more zippy because of that lightweight crank and the math proves it. I love that zippiness. I don't need any math to justify it. If reducing the track weight gives YOU that same feeling then to each is own.
Cinno
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Other things to consider with "rotating mass".
What is the distance from the center of rotation?
ie: Will a pound of jackshaft weight loss have the same effect as a pound of secondary clutch weight loss?
Does a one-pound change in heavy object like a track change things as much as a one lb change in a driveshaft or Jackshaft/clutch assembly?
How do you separate things that are tied together like the track/driveshaft/drivers/sprockets/chain(or belt)/jackshaft/secondary?
There is also a tipping point with lightening up the engine rotating assembly....at a certain point you can take away too much "flywheel" and change things in a negative way.
Besides the response-ability of rapid increase/decrease in speed of rotation... What affect does the rotating mass have on the gyroscopic influence over the chassis and rider?
Things to ponder.
.
What is the distance from the center of rotation?
ie: Will a pound of jackshaft weight loss have the same effect as a pound of secondary clutch weight loss?
Does a one-pound change in heavy object like a track change things as much as a one lb change in a driveshaft or Jackshaft/clutch assembly?
How do you separate things that are tied together like the track/driveshaft/drivers/sprockets/chain(or belt)/jackshaft/secondary?
There is also a tipping point with lightening up the engine rotating assembly....at a certain point you can take away too much "flywheel" and change things in a negative way.
Besides the response-ability of rapid increase/decrease in speed of rotation... What affect does the rotating mass have on the gyroscopic influence over the chassis and rider?
Things to ponder.
.
F(_)CKING AWESOME!!!
Best response I've seen in a long time. This thread reminds me of dinner table arguments at my house.
Val is the mechanical engineer, masters degree in mechatronics from Stanford, left NASA because she was bored (!!!!)......needless to say, she is the smart one. Loves math, SolidWorks, and FEA modeling.
She loves to call me "shade tree", laughs at the fact that I have a liberal arts degree.... But she also knows I have twenty plus years of working in professional motorcycle Roadracing including five years in the Motogp World Championship and a couple in World Superbike-- working with data engineers, motor engineers, suspension engineers, Factory teams and well funded independent teams. Sometimes it seemed like my job was keeping the engineers from killing each other in the box and trying to get them to actually listen to the rider--the one guy who actually makes a motorcycle go or stop.
Placebo effect doesn't fly with either of us, typically we need to verify through data acquisition--- BUT...... There are instances where "feel" can exist without empirical data.
But I still like your answer better
"Caveman push throttle, make sled go up hill"
Still laughing:rofl:
T
I heard years ago that removing 1 lb of rotating weight was equivalent to removing 7 lbs of stagnant weight. Although I am not an engineer, it seems to make sense that having less rotating weight will have a quicker effect on acceleration and performance then taking weight off of your tunnel.
Someone earlier in this thread said that its too bad that its not the $100/ per lb to reduce weight that it used to be. I don't see that as a bad thing. I think it's great because the manufacturers of sleds and aftermarket parts have pushed the sport which makes it harder for us as the average consumer to drop weight strictly because there isn't as much weight to be lost.
Someone earlier in this thread said that its too bad that its not the $100/ per lb to reduce weight that it used to be. I don't see that as a bad thing. I think it's great because the manufacturers of sleds and aftermarket parts have pushed the sport which makes it harder for us as the average consumer to drop weight strictly because there isn't as much weight to be lost.
C
I'll leave this right here...
Yes the theory is correct, but the ratio of change is a function of where the weight is in the drive train and of the absolute moment of inertia of each part. One pound on the belt is the same as one pound any where on the sled, if the track is coupled to the snow, therefore the ratio here is 1:1. The sled acceleration is reduced by 1/600 (0.16%). NOW increase the primary clutch by one lb and this may decrease the acceleration by 7/600 (1.16%) because of the increase of the moment of inertia of the primary clutch (Just an example here!). Some of the motor torque is lost at the primary to accelerate it rotationally. Hence the 7:1 ratio that is mentioned. The sled acceleration will be reduced as if you added 7 pounds to the sled. You increase the secondary clutch by one pound and since its diameter is larger its inertia will be larger by diameter to the 4th power. However if your at 1:~3 gear ratio (motor engagement) the reflected secondary inertia added to the motor is only 1/9 of the secondaries actual inertia. As the clutch shifts out to 1:1, all of the secondary inertia is reflected to the motor. So the reflected inertia is a function of gear ratio squared. This occurs because when you gear something down the speed goes down and the torque go up. Put your 10 speed bicycle on a stand and peddle it in first vs tenth. The inertia felt on the peddles is a function of gear ratio and is dramatic.
Cinno
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If anyone has actual questions, about our ZRP rotating performance products please pm, email me, or post then here and I will answer them.
For the most effect the rotational weight loss should be reduced from fastest spinning to the slowest, starting with outside diameter and progressing towards the center line (Axis) of rotation. (In short) A pound off of the outer diameter of the primary (fastest spinning speed and furthest from the rotational centerline) will have more effect on acceleration / deceleration than reducing the weight of the primary clutch bolt the same pound.
I'm not advocating this, but as most Polaris sleds are geared too high stock (theses days) and never fully shift out. Most could probably cut an inch off the outer diameter of the primary without any issues, and loose a pound or more.
I'm not advocating this, but as most Polaris sleds are geared too high stock (theses days) and never fully shift out. Most could probably cut an inch off the outer diameter of the primary without any issues, and loose a pound or more.
This is how my brains thinks about it too.
I
This is why manufacturers are going to smaller track drivers.
I think a track driver is only turning around 400 rpm at wide open. That's why Indy dans billet aluminum drivers are popular with racers, the added weight doesn't matter. I'd guess OEMs are going to smaller drivers to fit larger lug tracks.
WRONG! A 7 tooth, 2.86" pitch driver at 80 MPH is turning ~4220 RPM. Given a flat belt.
I'm going to vent for a second. If you don't know how things work a snake oil salesman can sell you anything. Ever heard of the "placebo" effect? Its real. Knowledge allows you to focus on whats important and ignore what the snake oil salesman is saying. So go ahead and buy the $100 aluminum track driver but I'm telling if you simply ignore the $5 breakfast the morning of the race you'll be ahead. I'm not saying it doesn't make a difference, its just that its so small. You do that and 100 other small changes then together they make a measurable difference. When you make one change and don't know that its insignificant by itself, you jump to all sorts of wrong conclusions. It is very difficult to measure small changes in the snow or on a dyno. You can make a change and say it felt different but was it real? Was the pipe the same temp, was the snow the same, was the air temp the same, belt the same tension, air pressure? same amount of gas in the tank. How many beers did you have after making those changes? OK i'll stop now.
Cinno
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My snake oil looks sooo pretty!
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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
You're all over the page here bud. You're telling me a small change doesn't matter, it's snake placebo oil and all in my head. Then you say I need a lot of snake placebos. Oh and $100 for billet drivers? WRONG!!
There was a thread in an Enduro forum a while back....some young kid just bought a brand new 2015 off road bike and opened the proverbial can of worms by asking "How can I make it better/faster? I have $2000 extra to spend"
A seasoned vet shut it down with once sentence. "Buy gas and ride it"
Point being, powersports produced today are far more capable than the Joey's piloting them. Want to lose weight? Eat healthy and work out. Want to ride better? Ride more. The answer isn't always in the wallet.
Don't get me wrong I love wrenching and opening parts boxes just as much as the next guy....but I've also learned a lot of things the hard way. I work too hard for my money to piss it away making changes that are far less beneficial than those that can be made to the most universal component in the equation: The Rider.
A seasoned vet shut it down with once sentence. "Buy gas and ride it"
Point being, powersports produced today are far more capable than the Joey's piloting them. Want to lose weight? Eat healthy and work out. Want to ride better? Ride more. The answer isn't always in the wallet.
Don't get me wrong I love wrenching and opening parts boxes just as much as the next guy....but I've also learned a lot of things the hard way. I work too hard for my money to piss it away making changes that are far less beneficial than those that can be made to the most universal component in the equation: The Rider.
Cinno,
Ur calculations are correct, ur math is wrong.
20% weight reduction on the track has a huge impact on track acceleration!
Snowmobile tracks will always accelerate faster than the sled.
The amount of snow the track can grab will always weigh less than the sled, therefore the track (path of least resistance) will push the lighter load (snow) rearward at a much faster rate than moving the heavier load (sled) forward.
The load on the track varies so much due to sled angles, speed, and snow conditions, not to mention track length, lug height and design, extremely difficult to quantify!
GS6
Ur calculations are correct, ur math is wrong.
20% weight reduction on the track has a huge impact on track acceleration!
Snowmobile tracks will always accelerate faster than the sled.
The amount of snow the track can grab will always weigh less than the sled, therefore the track (path of least resistance) will push the lighter load (snow) rearward at a much faster rate than moving the heavier load (sled) forward.
The load on the track varies so much due to sled angles, speed, and snow conditions, not to mention track length, lug height and design, extremely difficult to quantify!
GS6
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