Track Clearance discussion

[byeatts]

Best clearance for performance, Many of the Mod shops wont go with less than 3/4 inch?.I,m staying with 7 tooth with the 3 inch to get over one inch clearance.Lets hear everyone's thoughts and experiences?

 

[winter brew]

I think the gains are from the shallower attack angle (generally a good thing for the deep) and being able to run a bigger driver might add a little efficiency/reduced rolling resistance.
I am not sold on "just" the additional clearance being of any measurable benefit......but when someone goes "all-out" with a dropped or extended chaincase they are generally also accomplishing these other things which are, without a doubt a benefit for a deep snow sled.
I have heard talk of air pressure being built up and possibly slowing track speeds.....I don't buy into that at all. In my "normal" job we have done several tests that I can relate to this, and what it takes to build up any sort of air pressure or resistance and from what I have seen using huge volumes of air and sensitive equipment, it is just not going to happen.... way too many escape routes for air on the sides of the track and through the driver windows. No more resistance than it will see just from the nature of the paddle/air friction....if that makes any sense.
Given the choice I think the added clearance has more benefits than drawbacks....the big factor is the effort and expense involved to accomplish this.

Another thought....many years ago I had helped build some sleds with huge clearance....like 2"+. Depending on your cooler configuration, what I generally saw was huge amounts of snow/ice buildup in the tunnel and the track would carve a path through the snow....so in reality the clearance was virtually zero most days....plus the added weight. With the right cooler layout this would not be a factor.

 

[byeatts]

I think the gains are from the shallower attack angle (generally a good thing for the deep) and being able to run a bigger driver might add a little efficiency/reduced rolling resistance.
I am not sold on "just" the additional clearance being of any measurable benefit......but when someone goes "all-out" with a dropped or extended chaincase they are generally also accomplishing these other things which are, without a doubt a benefit for a deep snow sled.
I have heard talk of air pressure being built up and possibly slowing track speeds.....I don't buy into that at all. In my "normal" job we have done several tests that I can relate to this, and what it takes to build up any sort of air pressure or resistance and from what I have seen using huge volumes of air and sensitive equipment, it is just not going to happen.... way too many escape routes for air on the sides of the track and through the driver windows. No more resistance than it will see just from the nature of the paddle/air friction....if that makes any sense.
Given the choice I think the added clearance has more benefits than drawbacks....the big factor is the effort and expense involved to accomplish this.

Another thought....many years ago I had helped build some sleds with huge clearance....like 2"+. Depending on your cooler configuration, what I generally saw was huge amounts of snow/ice buildup in the tunnel and the track would carve a path through the snow....so in reality the clearance was virtually zero most days....plus the added weight. With the right cooler layout this would not be a factor.

What is the clearance on the 12,s with the 2.5 stock track?

 

[winter brew]

I have not measured it. Not alot.

 

[CBX]

I agree with winterbrew on the snow build up. I don't know if it works better, i've seen and done both. I do know the more space, usually means more buildup.

I'm not a huge fan of the 7T driver. Ran avids on the rev. My bro has them on both yammi's. I know for a fact the rev drivers were undersized, and weren't actually round between the teeth. Thats how they accomplished the clearance. By shortening the distance between drive teeth.

You pretty much have to use a 7T to run a 3" lug track.

They work on the yammi's. Dont know it its a dimension difference, or because the yammis run a way steep aproach, and it basically has less track wrap around the driver.

Maybe thats the key? I know that the yammis he has both have 2.5 tracks, no clearance and run like dirty mothers in the steep and deep.

 

[byeatts]

I agree with winterbrew on the snow build up. I don't know if it works better, i've seen and done both. I do know the more space, usually means more buildup.

I'm not a huge fan of the 7T driver. Ran avids on the rev. My bro has them on both yammi's. I know for a fact the rev drivers were undersized, and weren't actually round between the teeth. Thats how they accomplished the clearance. By shortening the distance between drive teeth.

You pretty much have to use a 7T to run a 3" lug track.

They work on the yammi's. Dont know it its a dimension difference, or because the yammis run a way steep aproach, and it basically has less track wrap around the driver.

Maybe thats the key? I know that the yammis he has both have 2.5 tracks, no clearance and run like dirty mothers in the steep and deep.

good discussion . I have extended chaincase and will have over 1 1/8 clearance with 7 tooth and 5/8 inch with 8 tooth with the 3 in paddle.my approach angle will be awesome with 8 tooth however will require a 19 top gear and a dogleg in the chain. If I run the 7 tooth I can run a 21 top and no dogleg in the chain.Have both size drivers on the shelf. I also have wondered about large clearance ,it must build up with ice and wish i had looked in there last year on one of those days when sled was already up side down.hmm

 

[winter brew]

Are you already at 51 on the bottom gear?
That brings us to the dogleg in the chain debate. LOL

 

[byeatts]

Are you already at 51 on the bottom gear?
That brings us to the dogleg in the chain debate. LOL

07 with Straightline extended case.8.5 center/center will only hold a 48 bottom and 19 top gets me to 2.52 and then the reduction of that final number since drives size is 24 inch[8 tooth].Ive never run the 8 tooth x3 pitch and not sure how much they perform over the 7 tooth. The icing is a real issue, The only tight spot is on top of the driver at 5/8 inch. I hate to run a 19 top!.no easy way here

 

[winter brew]

Have you seen any negative effects running a 19?...besides the theoretical accelerated chain wear from a sharper bend?

 

[byeatts]

Have you seen any negative effects running a 19?...besides the theoretical accelerated chain wear from a sharper bend?

no havent had issues just the 19 tooth theory , also run 15 wide chain ,I will change the chain out at 1500 miles regardless,The dogleg does bother me a tad and will eat energy,how much is a good question. Mod shops have always looked for the larger clearance and Doo with the 2.5 has little.[Hence the main reason for this thread}I,m not certain anyone has really studied this in a controlled situation.Perhaps as you suggested its really not a big issue as the icing will occur to the paddle contact point anyways.The 8 tooth does appeal more for the reason that I will be able to lower skid one inch and achieve a flat approach angle. A taller sled tips with ease and totally changes the handling which I prefer.looking for a smoking bullet but it aint there.I want a 21 top no dogleg and 8 tooth with 2.35 to 2.4 finale gearing.

 

[byeatts]

no havent had issues just the 19 tooth theory , also run 15 wide chain ,I will change the chain out at 1500 miles regardless,The dogleg does bother me a tad and will eat energy,how much is a good question. Mod shops have always looked for the larger clearance and Doo with the 2.5 has little.[Hence the main reason for this thread}I,m not certain anyone has really studied this in a controlled situation.Perhaps as you suggested its really not a big issue as the icing will occur to the paddle contact point anyways.The 8 tooth does appeal more for the reason that I will be able to lower skid one inch and achieve a flat approach angle. A taller sled tips with ease and totally changes the handling which I prefer.looking for a smoking bullet but it aint there.I want a 21 top no dogleg and 8 tooth with 2.35 to 2.4 finale gearing.

I does bother me that all this talk about clearance has never been supported by any study that i know of.? hopefully someone can educate me with evidence

 

[turbo800]

If it was me I would go with the 8T drivers. Better approach, better rolling resistance. If not having a dogleg in the chain is that important, knock a few links out and put it back together, or buy a new chain. Buddy of mine went with the Avid ext. chain case on his XP, with the 3" lug 3.0p track he has just over 1/2" clearance w/ 8T drivers. If ice is just gonna form there with added clearance, your not gaining much of anything IMO.

 

[byeatts]

If it was me I would go with the 8T drivers. Better approach, better rolling resistance. If not having a dogleg in the chain is that important, knock a few links out and put it back together, or buy a new chain. Buddy of mine went with the Avid ext. chain case on his XP, with the 3" lug 3.0p track he has just over 1/2" clearance w/ 8T drivers. If ice is just gonna form there with added clearance, your not gaining much of anything IMO.

Chains come in even numbers [Pitch{ cannot go shorter.I,m at 78.9 so must use a 80 pitch chain.I,m also leaning towards the 8 tooth now.

 

[turbo800]

Hmm, sounds like you will only have a slight bend anyway. IMO the tradeoff with larger drivers vs the shorter straighter chain are 10:1. I'm not sure I'm a fan of the flats between the teeth of the Avid either. Seems the 15w and 19t sprocket are holding up just fine. Can you make a 20t with any combination length chain fit your agenda?

 

[CBX]

Dont sweat the small stuff Yeatts. I'd just run the 20/48. Thats 2.4. Or hog out the lower end of the case just enough to fit a 49 gear in there For 2.33 . Solves all your problems.

You wont get your birthday taken away or have the boogey man beat you up if you run a 19 or 20 top gear, i promise. lol.

Go with the 8T drivers. Man i am just not a fan of 7's. Or better yet, run a 2.86 track and don't look back.......... i know i know, that doesn't work for you. Have to have the biggest one.

If it were me, 7T would be the last resort on a Rev. After my experience with them, never again. Without going to town and modding the case, 20/48 is as good as it gets on 8T, or go 7 and the options are endless.

 

[byeatts]

Dont sweat the small stuff Yeatts. I'd just run the 20/48. Thats 2.4. Or hog out the lower end of the case just enough to fit a 49 gear in there For 2.33 . Solves all your problems.

You wont get your birthday taken away or have the boogey man beat you up if you run a 19 or 20 top gear, i promise. lol.

Go with the 8T drivers. Man i am just not a fan of 7's. Or better yet, run a 2.86 track and don't look back.......... i know i know, that doesn't work for you. Have to have the biggest one.

If it were me, 7T would be the last resort on a Rev. After my experience with them, never again. Without going to town and modding the case, 20/48 is as good as it gets on 8T, or go 7 and the options are endless.

yep the chaincase is already ported to fit the 48, might be able to fit a 49 with a little more work.20 top kills my ratio, But back to the real topic has anyone looked above the drivers to see what kind of snow buildup they have?

 

[mountainhorse]

The 2010 XP 800 Summit X in my shop right now has the stock drivers /track.

With the XP having front bulkhead heat exchangers and full length U-coolers in the roof of the tunnel... I'm not at all worried about ice build up there from "too much" clearance.

It has 1" front clearance and 5/8" at the top...with the stock 2.33" lug.
The top is the tight clearance spot.

The 7 tooth, 3" pitch drivers increase clearance by .30" (about 5/16")
A 3" track lug on the 7 tooth drivers will take the clearance down to 5/8" front, and 1/4" on the top.

A 3" wont rub on the top unless you run the track loose.

Running the 3" track at anything less than factory tension will, IMO, lead to early track failure and delam from from the excess heat buildup.... not to mention diminished performance from more friction across the hyfax and the paddles "laying down" because, without proper tension, the leverage of these tall paddles will flex the track belting and lay down because there is not enough tension to keep them standing up

"Not Rubbing" and giving proper performance are not necessarily the same thing.

The XP has pretty good clearance for a modern mountain sled.

Drag from lack of clearance is more of an issue in heavy/wet snow than light/dry snow.

A 3" paddle will move more snow thru the tunnel than a 2.5" paddle. More snow, less clearance... more drag.

Here is my take on the topic from another thread in the Poo section... but it applies here IMO.

In order to run a taller track you not only have to maintain the lug tip clearance, but you have to increase it (on stock tunnel/skid/drive). Simply put, a taller lug will move more snow. The more snow you have to move out the front of any given tunnel-opening, the more parasitic loss you will have ( “pumping-loss”).

To illustrate this, look at any action pic, in the pow, where someone is on a "wheelie" for whatever reason... you will see gobs of snow spraying out the front of the tunnel. The tighter the opening is, the more power it takes to push the snow past the restriction (the opening at the front of the tunnel at the bulkhead)...

Getting a track to fit, and having it run well are not necessarily the same thing. If it comes close to rubbing, IMO (as well as Mark Holz, Mike Vanamburg and others) it has no place on a properly set up deep-snow sled.

People riding in light champagne powder will have a whole lot easier time getting thru the snow with little clearance than wet heavy pow... like we get on the west coast.

It is not the snow that is "packed up" inside... which, with the full length coolers on the Dragons is very minimal... it is the snow that you physically have to get pumped thru the tunnel...

Snow is pumped thru the tunnel like water down a river... you may get some minor buildup of ice in the nooks and crannies... but it doesnt get packed up there and stay. If it did...you're sled would stop.. Were talking tons of snow per minute here.

The smaller the opening... the harder the "pump" (read engines and clutches) have to work to get the same fwd motion. This amount of extra work grows exponentialy with the reduction in size.
This could account for upwards of 10- 20 HP worth of parasitic drag when you are ... I dont know of a pipe that give you that much hp.

For an example of this "pumping thru"... have a look at this Youtube video... in particular at :57 seconds into the clip.... you will see huge amounts of snow getting pumped out of the tunnel opening. This is typical of deep snow operation.
http://www.youtube.com/watch?v=eiuzQVlKDvM

On the Polaris sleds this is the weak suit in the design.... lack of clearance.

More material, (weather that is snow, water, dirt, yogurt or electrons) through a fixed opening takes more energy to move through that opening.

If you take the same amount of material and move it thru a smaller opening... it takes more energy (HP) to move it at the same speed.

Opening up the clearance will take less HP run the sled thru the powder.... even more evident in high moisture content snow like we get in the Coastal states.

The ONLY reason. IMO, to switch to a 3" pitch track of the same type would be to be able to run 7 tooth drivers which have the smallest diameter (read tunnel clearance) of any of the drivers out there... there are no 7 tooth drivers for the Polaris shaft other than the Combo drivers. There are no 2.86" pitch 7 tooth drivers either. The additional clearance compared to an 8 tooth 2.86" driver (stock or Combo) is .28"... which would take the clearance from about .15 with the 8tooth drivers & a 2.5" lug to to about 5/8"...

Does the Camo Extreme perform better in most conditions, yes... It could be better if it had more clearance...

I'm running the Arctic Cat Power Claw HCR 153 on my sled this year... We'll see how it compares to the 155 Camo X, 2.86" pitch that I pulled off...it is 9 lbs lighter than the 155" Camo Ext 2.86 P

Point 2.... The RAW chassis with the 2.4" track has the least clearance of the production RMK's... mostly at the fwd roof of the tunnel is where it gets choked off.

Here is a photo of a RAW RMK tunnel (upside down) showing the rubbing of a STOCK 2.4" track on the tunnel... Polaris did not put much clearance for the big tracks in this area. I have seen a lot of Dragons with this rubbing. The Ch Ext 2.5" cuts this already marginal clearance by .10 (actually closer to 1/8" less) on the same drivers.


On sleds with large rear idlers... this rubbing is more apparent as the taller rear idler allows the track to lift off the top idler and go slack when the sled wheelies or comes down hard on the back of the tunnel.

The earlier models had more clearance at the roof of the tunnel... there was no cooler there... it was in the back only.

With D&R's... there is no free lunch as AK pointed out... move it down and back...net change in AOA is not that much... D&R's, IMO, the least amount to gain acceptable track clearance without throwing the balance of the sled off.

My 2 cents

PS... There was a VERY good write by Lane Lindstrom up on the topic of tunnel clearance in the December 2005 issue of SnoWest on page 44. If you still have your old mags.... dig this one out... It has "Saving the 700 class" on the cover with a pic of red 2006 700 RMK wheeling away from the camera. Good imput from some of the best sled builders in the industry.

On the Polaris RAW chassis, ice does not build up of the tunnel like in the days when the coolers did not run full-length. The problem area is at the front of the tunnel on the Dragon models where there is no bulkhead heat exchanger to melt off the snow... The plastic plate on the dragons sheds snow, but the space between that the cooler on the tunnel roof does get ice sticking/building up... I run a 1/16" thick piece of UHMW plastic, full width, in this area... Ice/snow will not stick to UHMW.

Loose track = poor track performance...especially on stiff duro tall lug tracks like the Ch ext. if the track is looser than stock... stabbing is more likely, the track will lean over and cause other problems... Correctly tensioned tracks perform better... dont take my word for it.... Call Bruce Dashnaw at Camoplast or Jack Struthers at Carls cycles. Also, a loose track will further choke off the tunnel opening as the track "balloons" out at speed.

Running loose tracks was necessary on the early M series as that was the only way to get the skid to work... Polaris does not suffer from this problem.

I know many California riders that have over 1500 miles on their original hyfax... and that is running stock everything, less bogies add scratchers. Our snow is pretty darn hard and lubrication is less than ideal.

Davy... The rolling resistance between an 8 tooth and 7 tooth is not that big.... there is a big difference between pulling on a track on the stand to judge drag.... and the driver actually driving the track with the weight of the sled/rider on the track. This applies to running big rear idlers, which on the RMK's, if you go larger than 8" you will see more drag and slack track problems.

The boundary layer of water on the coolers keeps the tunnel pretty darn clean, even at slow speeds. The UHMW PE would further add to the snow evacuation... I'll stand firm on my opinion that the snow flows thru the tunnel like water down a river.

Personal experience with the 2.5" ch extreme with 7 tooth drivers.... it works well, especially if you have the track at the correct tension.

Would a bigger driver be possible...yes... is it practical, NIMO... I really want as little or no D&R as possible in my sleds....

The tunnel in the photo ran the stock series 5.1 DUAL ply track from 2008.
Tunnel clearance was about 1/4"....

Find that back issue of SnoWest that I talked about and give it a good look-see.

Good luck with your build...I hope to ride with you this year.

MH.

 

[mountainhorse]

BTW...

This 2010 Xp is getting the AC style Avid drivers and the 174" x 3" paddle track next week. (If the track comes in!!)

 

[sledsrock]

You know your gonna try both set-ups anyhow, and with the delay of that track just go with 8 toothers and the ole trusty rusty CE 2.5 for now and see what the difference is if any from last year.

 

[mountainhorse]

Atcually.. It's a friends sled I'm building for him.

Here is the reply I just gave in a PM.

I do believe that there is some clearance... but not as much as I'd want... Also,But this is for a good friend who has his heart set on the 3".

IMO, the amount of truly deep riding that he does compared to your average great backcountry day does not have him in need of the 3" lug track.. and that the 2.5" would be a better choice for him... It is just plain "more durable".

Time will tell.

I do know that the 3" paddle tracks are great performers...

With the track speed that a turbo can offer and the performance of a 174" track in the first place...I believe that the 2.5" 174" track is a better choice for all but a handful of riders.

Here is a post with my thoughts on the 3" paddles and durability.

These are just my opinions... others have theirs that could be just as valid.

These tracks should be looked at like a tire on a dragster... an expendable, purpose built tool to get some extreme work done outside of what a consumer offering can provide... In the conditions that we are running these tracks in, the Horsepower and speed that we are getting out of these sleds... don't compare them to the the durablilty track with a smaller lug. l. With the loads todays sleds are putting on these tracks..they are actually more durable than Your ole 1.5" paddle.

If you cram 200+ HP into a track and generate 90mph track speeds in the fluff and hit a hard ice chunk, stump or rock... you will loose paddles... If you don't like this, get a shorter lug track that is not so stiff... YES your performance will drop, but your track will last longer and be more durable.

If you must have the higher performance that the tall lug tracks will give you... accept the shorter life of the track... you can't have both, IMO.

Proper tension (not too loose) on these tall lug tracks will give your sled better performance and longer track life as well.

There are some defective tracks just like there are defective computers, tires, snap-on tools ... you name it... But for the most part, Camoplast builds a very high quality product.

If you have a turbo Nitro and are running the 3" lug, well, you should expect to putt along on the trail at 30mph max with scratchers down and expect that these stiff & Tall lugs with all the leverage they can put on the belting will shed some paddles when you are climbing the gnarly chute... or boondocking and snag a rock or ice chunk. ... you should expect this.... and to a certain degree, you should expect this with the 2.5" Extreme if you abuse it with high speeds and/or run over stuff at on a 250-hp+ pull with 80mph track speeds...

The damage to a track that sheds a paddle probably happened earlier in the day/week/month/season.... From that high speed run back to the cabin/trailer or a that 300 ft long sheet of ice we barely make it up fully pinned WFO. The heat that builds up INSIDE the rubber at the root of the paddle is what starts the process of delamination...this heat occurs because the paddle is forced to bend too much at the root ...from the heat of high speeds... in marginal snow... back and forth, like breaking a paper clip by wiggling it back and forth (different physics, I know... but the visual is what I'm going for here)