850 gone down already??

[dboivin]

Doesn't Polaris offers 4 year warranty on this 850 engine?

i dont believe they did back when dan was offering it on his motors. now yes.

when i had my 15' my warranty was 1 year thru polaris and then 2 or 3 years through a crappy secondary company which was a pain to deal with. the 4 year came soon after i think 16 or 17?

 

[andrew90]

I skipped thorough some of this because the good info was getting sprinted in drama. I know I say can put out an extreamly good product and is full of knowledge. When you look close the pistons in his picture of the coating you can’t clearly see rub marks in the horizontal direction Simone was trying to make it lol worse. After this when someone else took pictures of their pistons Dan replied that it will be the intake side but his picture of of the exhaust side. Seems a bit off to to me

 

[kanedog]

I've got a snappy one - especially for only have a couple hours on it. But..... running SLP clutch kit (spring and weights). The all stock one we have definitely feels different.

Post a vid of your snappy monster. One mans snappy is another mans dawg.

 

[jim]

Some metallurgy on this topic regarding the floating bearing. It is tough to argue Dan's information on this one. When you have a very solid bearing material (hardened carbon steel) which expands at a different rate than the aluminum clamping material with heat, you will absolutely see the dimensions of the aluminum case material expand more than the steel, even if somehow they are kept at the same temperature. Aluminum will expand at a rate of 21-24 (10-6 m/(m K)) versus steel at 11-12.5 (10-6 m/(m K)) given the same temperatures. Even these numbers point to issues with an expansion difference...now throw in the real-world fact that aluminum has a much faster heat transfer, or absorption rate, of this heat (how fast it moves the heat into the material) at 125 (Btu/(hr F ft)) versus steel at around 20 (Btu/(hr F ft)). This is a major challenge in matching these materials when heat is applied fast (which would mean any moving of the sled at all). What this all means is that you have cases that absorb the heat 6x faster and grow 2x more than the steel...that means the "clamping" of the cases on the bearing loses force really fast. Add the hammer affect of the clutch and it is not the most absurd notion to conclude that the bearing could be moved. More material evidence? Aluminum does not bond well to such a dissimilar material...the molecules simply don't align, fit and bond...they move. The galling is from the mismatch of molecules and material tearing/shredding and failure on a microscopic level. We are all too familiar with this with the piston to cylinder interface (which, by the way is fairly closely matched in expansion rates), but it applies to the bearings in a much more significant way. Warm up to me is less about pistons than bearings. And even with perfect warm-up, the bearings to case are a natural weak point. Not having a method to keep them in-place is haphazard for this clutch hammering application. No side load...no biggy...actually helps keep things in place. With a slide load...better have a back-up retainer method...or the ring. Sorry for the nerd-out...but there is a reason these materials walk with respect to each other. The science backs up everything Dan says. As a matter of fact, there is nothing that I see as an argument to his point. And I will call it out in a tactful argument if I disagree. It all makes sense.

 

[Mafesto]

There's a saying that goes... People who think that they know it all really p_sses those of us that actually do.

It's fun reading this thread and all of the knowledge some of you have. It reminds the rest of us that we only THINK that we are smart, and humbling how it reminds us how little we actually know!

Damn it, I didn't wake up wanting to learn today....and then you guys trick me into learning.
Sneaky basstards!

 

[tdbaugha]

Some metallurgy on this topic regarding the floating bearing. It is tough to argue Dan's information on this one. When you have a very solid bearing material (hardened carbon steel) which expands at a different rate than the aluminum clamping material with heat, you will absolutely see the dimensions of the aluminum case material expand more than the steel, even if somehow they are kept at the same temperature. Aluminum will expand at a rate of 21-24 (10-6 m/(m K)) versus steel at 11-12.5 (10-6 m/(m K)) given the same temperatures. Even these numbers point to issues with an expansion difference...now throw in the real-world fact that aluminum has a much faster heat transfer, or absorption rate, of this heat (how fast it moves the heat into the material) at 125 (Btu/(hr F ft)) versus steel at around 20 (Btu/(hr F ft)). This is a major challenge in matching these materials when heat is applied fast (which would mean any moving of the sled at all). What this all means is that you have cases that absorb the heat 6x faster and grow 2x more than the steel...that means the "clamping" of the cases on the bearing loses force really fast. Add the hammer affect of the clutch and it is not the most absurd notion to conclude that the bearing could be moved. More material evidence? Aluminum does not bond well to such a dissimilar material...the molecules simply don't align, fit and bond...they move. The galling is from the mismatch of molecules and material tearing/shredding and failure on a microscopic level. We are all too familiar with this with the piston to cylinder interface (which, by the way is fairly closely matched in expansion rates), but it applies to the bearings in a much more significant way. Warm up to me is less about pistons than bearings. And even with perfect warm-up, the bearings to case are a natural weak point. Not having a method to keep them in-place is haphazard for this clutch hammering application. No side load...no biggy...actually helps keep things in place. With a slide load...better have a back-up retainer method...or the ring. Sorry for the nerd-out...but there is a reason these materials walk with respect to each other. The science backs up everything Dan says. As a matter of fact, there is nothing that I see as an argument to his point. And I will call it out in a tactful argument if I disagree. It all makes sense.

99%+ of all components in a jet engine utilize a primary assembly method of radial interference fit with most using secondary (redundant) assembly method using snap rings, pins, bolts, etc. And there are many different types of metal involved. Service temperature gradients of jet engines are like 4-5X larger than our sleds. Just sayin

 

[MKULTRA]

a jet engine and a mtn sled engine price segment is quite different, just sayin

 

[tdbaugha]

Jet engines also push 500,000 pound planes through the air at 600+mph with essentially 0% failure rate. Just sayin

Point is, interference fit assemblies work fine if properly executed.

 

[2XM3]

interference fit assemblies work fine if properly executed.



Thats the critical statement right there "properly"

 

[High Voltage]

Jet engines also push 500,000 pound planes through the air at 600+mph with essentially 0% failure rate. Just sayin

Point is, interference fit assemblies work fine if properly executed.

Does a jet engine have a clutch slapping it silly? Just asking

 

[tdbaugha]

Does a jet engine have a clutch slapping it silly? Just asking

No, but it is transferring all of the 100,000+lbs of thrust axially through it's bearings and into the wing.

 

[MKULTRA]

Ithis thread was way better with tech bitching then the jet engine comparaison

 

[Mafesto]

99%+ of all components in a jet engine utilize a primary assembly method of radial interference fit with most using secondary (redundant) assembly method using snap rings, pins, bolts, etc. And there are many different types of metal involved. Service temperature gradients of jet engines are like 4-5X larger than our sleds. Just sayin

What's your point?
You're admitting in your post the redundant use of securing methods.
That's openly admitting that their purpose is needed.

 

[sportfire]

If the pto bearing isn't riding on an inner race and assuming the crank is finished to a wider dimension than just the rollers, does this bearing need to be secured with a snap ring? Will crank end play and clutch engagement cause it to shift even though its not aligned to the crank by an inner race? In theory the crank could slap back and forth a 1/4” and not have a significant load applied to the bearing.
Not denying Dan's repair isn't the best locating solution just curious if it's really going to be a problem. The fit must be pretty good if the outer race can weld itself to the crank without spinning in the case. I haven’t been in a current 800 but someone mentioned they don't have a ring either?

 

[snowmobiler]

its like a box of chocolates.did the bearing rub for 75 miles.or did it slid over.

 

[tdbaugha]

What's your point?
You're admitting in your post the redundant use of securing methods.
That's openly admitting that their purpose is needed.

My point was the notion that a "floating" bearing can't work is wrong.

Webster: "Redundant: not strictly necessary to functioning but included in case of failure in another component"

I can't remember the agency, but they require manufacturers to use two methods "securing" on critical engine parts for safety.

Interference fits are the primary method of holding most (if not all) critical rotating assembly parts in place. And they work in the most extreme mechanical environment you can imagine for 20,000+ hours. I was just tired of reading Dan, Jim, and others claim that there's no way for an assembly to work like that in a simple 2 stroke. Not the case.

 

[sportfire]

If Polaris spent $1 for a snap ring and $5? for machining time, we wouldn't even need half of this thread!!! Next years snowcheck option.

Anyone have some theories on the center bearing failure yet?

 

[05900]

Meanwhile back in Medina

 

[summ8rmk]

No, but it is transferring all of the 100,000+lbs of thrust axially through it's bearings and into the wing.

I don't know much about jet engines. But here are what i assume are significant differences.
I assume they always spin in the same direction when running. Always brought up to a certain temperature before any load is applied. Although total power and load are very high, lateral load is low and not variable. Vibration is better controlled. Assembled with a much higher standard and precision.
Operators are all professionals following the operator guidelines to a 'T'.







[emoji12]

 

[Mafesto]

My point was the notion that a "floating" bearing can't work is wrong.

Webster: "Redundant: not strictly necessary to functioning but included in case of failure in another component"

I can't remember the agency, but they require manufacturers to use two methods "securing" on critical engine parts for safety.

Interference fits are the primary method of holding most (if not all) critical rotating assembly parts in place. And they work in the most extreme mechanical environment you can imagine for 20,000+ hours. I was just tired to reading Dan, Jim, and others claim that there's no way for an assembly to work like that in a simple 2 stroke. Not the case.

Are you saying that they are incorrect, and these bearings did not move?
Not being argumentative, just trying to absorb as much info as possible.