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Drivers on 850 turbo

T
Aug 8, 2011
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What are you guys using for drivers? 6 tooth avids or going up to 7 tooth?

I have to have the track fiddle string tight and it still ratchets if I hit something and load the track hard in boost

Thanks
 
F
Nov 27, 2007
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medicine hat
Got myself a set of seven tooth, seams to be pretty common with boost, even on NA it's gotta be pretty dam tight.. Lots of loss to friction with stock drivers and brutal attack angle.. Way to go brp
 

Chadly

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Aug 28, 2013
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I run the 6 tooth Avid drivers with about a half inch of sag off the rail. They have never ratcheted. Before I had them I ran the track banjo tight and it ratcheted anytime I landed under power.
 
T
Aug 8, 2011
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So with the loss of .55 inch of clearance with the 7 tooth driver how tight does that put the clearance of paddle to tunnel?

Anyone care to ponder what is more effective...a smaller driver that bends the track tighter but has additional tunnel clearance, or a larger driver for less rolling resistance but less clearance in the tunnel?

Thanks
 

madmax

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Probably not a question we will ever get a legit answer to. I only know when you put a 3” track in a proclimb Cat with 8t drivers there is very little track to tunnel clearance and the sled performs a lot better than with the 2.6 lug track and 8t that has over .5” clearance.
 
T
Aug 8, 2011
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It has Stock extroverts but the teeth are rounded over and with the single ply flexible tracks and only 6 drive teeth it wants to ratchet bad
 

rab

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Dec 15, 2007
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if I was to surmise,

I would say that the bigger wheel with less clearance and looser track would be more efficient on lighter snow and hard pack

I think that the smaller wheel with more clearance and the tighter track is only more efficient when the track is evacuating heavy spring snow out the front .

also as the speed of the wheel changes the efficiency will change on each scenario.

I think
 

Chadly

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Thank god my turbo makes enough power that I don't give a rat's arse about the supposedly inefficiency of a 6 tooth compared to a 7 tooth. Pretty sure you guys are splitting hairs here....
 
T
Aug 8, 2011
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Not sure on wahls....avids are better and by all accounts an avid 6 tooth won't ratchet. I just can't help but wonder if a 7 would be a little better is all
 

Ox

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Well of course it would. I don't know the approach angle to calc exactly, but just using 45* as a value (135* of contact) you would only have 2.25 teeth engaged at a time.

A 7 tooth driver on the other hand would have 2.625 teeth engaged.


So the amount of time that the track is out of contact with 3 full teeth is:

75% of the time for the 6 tooth

and

37% of the time for the 7 tooth.


To go with a smaller driver for the sake of air pumping - and sacrificing driver contact seems like a poor equazsion to me. If you were a lake racer - sure, but you're never gunna bring a full paddle's worth of snow on up and over the back axle, and what track speed doo you carry at best? 50mph up the hill? 60 on the outside? (I really don't know as I am in need of a newer machine)

Sure - there is air moving through there, but I doubt that you would ever see much "pressure". Just volume...


Aren't the tracks on the 850's a 3.5" pitch? (not that it changes the math) But that get's to be a large driver....


.
 
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