Helix angles, quick question.
Jere
those 2 angles on the helix?
Is the 55 degree part near the tip, or is the 55 degree part near the
base?
It would make more sense to me if the 55 was near the base because it
would correspond to less belt pressure when the belt is slid down in
the secondary clutch, which is what I understood you wanted?
Looking at this helix we have here in the garage it looks like the
steeper part is near the tip? This doesnt make sense to me, what am I
missing? Steeper angle would mean less belt side pressure in the
secondary at a given torque right?
David Courtney
You're not missing anything... you're the smartest guy to ever post a
clutch tuning question on RSS since I started reading it several years ago
(I mean that).
First of all, you're right. Normally you need much more belt side
pressure when you're starting out than after you are up to speed and
shifting out. Here's the "birth" of the multi-angle helix as I remember it:
The multi-angle helix was originally a "crutch" to help the old Polaris
Storm (which had a ton of torque and a crappy track) hook-up. The only way
to get traction was to lug the motor until the sled got really moving... so
someone came up with the multi-angle helix.
Basically, it would be like if your car had bald tires... and you
shifted into second gear too early to keep from smoking the tires; rather
than getting better tires!
Unfortunately, the best way to make a multi-angle helix is to machine
one using a CNC machine instead of casting it like traditional helixes were
made. The CNC helix is more efficient than a cast helix because the ramps
are much more uniform (which distributes the load better) and smoother
because castings are porous, while the solid aluminum billets used to make
multi-angle helixes are very dense and uniform.
But, nobody ever bothered to make a straight angle, CNC machined, billet
helix... so everyone was fooled into thinking that the "multi-angle" was
responsible for the increased efficiency and better backshifting. That was
marketing, not science or engineering that sold all those multi-angle
helixes.
Virtually every multi-angle helix is "backwards"... they apply less belt
tension at low shift ratios where you need more (which would let the Storm
"hook-up" by upshifting too early) and more belt tension when the clutch is
shifted out... when you need less. (The Storm also had to run the goofy,
special "TopCog" belt with grooves across the outside, to try to keep the
belt from getting hot and exploding at high shift ratios... because it had
too much side pressure once it got up to speed!)
If you read between the lines in Olav Aaen's clutch tuning book,
especially the older releases of the book before it was "edited" to be more
marketing friendly... you'll find a huge "void" where the explanation of how
and why multi-angle helixes work (because Olav knows they don't) while the
rest of the book is very detailed about the theories behind each component
and it's affect on the system.
In fact, the brief explanation that is in there contradicts nearly
everything else in the book!
If you have adequate traction, like most any sled you can buy these days
does, I believe a multi-angle helix and any goofy weights you can come up
with will put less horsepower to the ground than an equivalent straight
angle helix and the proper stock-style weights will. Fortunately, there are
people making straight angled, CNC machined, billet helixes now.
Anyway, I'm not going to fight about this again... it's a very unpopular
opinion, but I think you are well on your way to becoming a clutch tuning
expert.
Having the common sense to really look at something like a helix and
understand what it actually does (or is supposed to do) and realizing that
most of the clutch kits are a sham; means that you will be able to
outperform everyone who blindly follows the magazine articles and
advertisements... and wastes their money on crap that doesn't work!
Good luck,
David
"Jere" <lbz...@email.com> wrote in message
news:5f8febfa.02021...@posting.google.com...
Doug Miller
> responsible for the increased efficiency and better backshifting. That was
> marketing, not science or engineering that sold all those multi-angle
> helixes.
Racers, hill climbers, OEM's, and yur basic redneck are all famous for
buying marketing hype and letting the other guy win in order to
maintain the big multi-angle conspiracy.
I don't know how to clutch a stock 95 XLT. Why don't you admit you
don't know how to clutch something with over 120 horsepower?
-Doug Miller
Doug Miller
> Ok when you have a helix stated as I dunno 55-51 helix, where are
> those 2 angles on the helix?
It starts out in the 55, then the buttons move to the 51 area.
> Is the 55 degree part near the tip, or is the 55 degree part near the
> base?
On Polaris that is true.
> It would make more sense to me if the 55 was near the base because it
> would correspond to less belt pressure when the belt is slid down in
> the secondary clutch, which is what I understood you wanted?
Step one, the goal is to have "enough" clamping force the belt doesn't
slip in the secondary. But actually, when starting out, for a variety
of reasons, clutch slipping is probably more prevelant in the primary.
But that isn't the reason....
> missing? Steeper angle would mean less belt side pressure in the
> secondary at a given torque right?
All else being equal, yes. But starting out, there is more belt
surface area on the secondary then once the belt starts moving down
into the secondary.
More importantly, the sled accelerates faster from 20 to 50 then it
does from 50 to 80, just picking numbers. Because it accelerates
faster, the clutch has to SHIFT FASTER. You can help the clutch do
that by using multiangle helixes, or you can do it by running weights
(eg heel clickers) that throw LOTS more load at the motor at lower
MPH.
Goal is to let the clutches shift fast enough to keep up with the
motor accelerating the snowmobile at lower MPH. This is a problem with
snowmobiles over 120 or so horsepower. If you don't load the motor
hard enough, the motor overrevs, and you lose go. Lose go, and your
buddy beats you.
Backing up for a second, a properly clutched motor produces nearly
identical torque and rpm figures for every MPH, assuming the throttle
is wide open.
-Doug Miller
Jere
try and understand it... I have a green spring on the secondary which
is a pretty stiff one I think. The spring was in the softest hole
when I got the sled and pulled about 8500 rpm. I moved the spring one
spot tighter and now it pulls 9000 rpm which is what I expected, same
helix, more spring tension equals more sidepressure on the belt and
with the same weights up front would result in the belt riding lower
in the primary and the higher rpm... ok thats fine.
I also understand that more spring tension in the secondary results in
quicker backshifts when coming off the gas then back on like in a
corner, more spring tension combined with a high degree helix would
allow the secondary to close much quicker when the track tension was
relaxed (ie braking). I think thats what I want beacuse its a sno-pro
and thats how I ride, full throttle, corner, full throttle again, I
like it like that.
So I think I prefer the new spring position in the secondary, now I'd
just like to get the rpms down a little because I think the motor is
best around 8700. It engages at 5000-5500 right now so I want to keep
that.
That being said I was thinking keep the stock primary spring and add
some weight to the tips of the weights... reason being adding weight
to the tips would move the centre of gravity inward when the weights
are folded in (less outward force because the radius is smaller) but
there is a little more weight so I thought they would cancel out
(higher weight = higher force, smaller radius to center of mass =
lower force) and I would have the same engagement rpm.
Now when the weights are flung out, the end result would be the same
radius to center of gravity as before but more weight, equaling more
force, rqualing more belt pressure and slightly lower rpms when the
machine is shifted out.
Make sense?
:-)
"David Courtney" <adv...@powercom.net> wrote in message news:<a4os5m$1ovnk$1...@ID-70857.news.dfncis.de>...
David Courtney
secondary spring tension and weight in the primary costs you a LOT in terms
of clutch efficiency.
That's fine for snocross or drag racing where you don't run for any
great distance shifted out... but will result in lower top speed, shorter
belt life and reduced fuel economy for trail riding or oval and lake racing.
Also, don't worry too much about adding weight to the "tail" of the
weight... just going to the next heavier weight will have very little effect
on the engagement rpm, but it will lower your shift rpm.
David Courtney
single exhaust pipe, nothing too complicated... and learn the fundamentals
of scavenging, compression, combustion, carburetion, port timing, intake
tract resonance, expansion chamber design... and especially clutching and
gearing.
Then come back here and run your mouth when you actually know
something... so you don't look like such an asshole all the time.
David
"Doug Miller" <dmi...@foresightpartners.com> wrote in message
Doug Miller
> You should go find a stock XLT... no exhaust valves, no reed valves, a
> single exhaust pipe, nothing too complicated... and learn the fundamentals
> of scavenging, compression, combustion, carburetion, port timing, intake
> tract resonance, expansion chamber design... and especially clutching and
> gearing.
the 3 cylinder thing with a single pipe always confuses me. how do you
make the pipe efficient?
> Then come back here and run your mouth when you actually know
> something... so you don't look like such an asshole all the time.
> David
But we're both so good at it!!!!!
So waddya think about my argument that clutches need to shift faster
at lower MPH then at higher mph?
Waddya think about the fact that straight angle helixes don't work
with bigger horsepower motors with roller secondaries (friction is
less of an issue).
Waddya think about the mass distribution of cat weights vs polaris
weights when compared at different mph's?
My take on it is that cat's run more weight at lower mph, which is why
they get away with less helix differential. What do you think about my
hypothesis?
I guess I originally thought that you were a pompous know it all that
I would learn nothing from.
I was wrong. I've learned several things while discussing things with
you.
I'm willing to back up, and be civil. You?
-Doug Miller
David Courtney
that's not really the point.
The point is that if you want to actually LEARN something it's much
easier, quicker, and cheaper to modify one pipe and test the results... than
to modify 3 pipes and hope you get them all the same.
You just don't get it! I don't have to ride an old XCR... I choose to
because I don't want to have to deal with variables like reed valves,
exhaust valves and digital ignition when I'm experimenting with airbox
tuning, porting and squish bands.
For $79/month any moron can buy a fast sled... but you have to
understand the fundamentals before you can modify one successfully.
David
P.S.
I already told you what I think about your ridiculous clutching and
gearing theories... no sense in starting that all over again.
"Doug Miller" <dmi...@foresightpartners.com> wrote in message
news:32b6c9cc.0202...@posting.google.com...
sledhead
> P.S.
> I already told you what I think about your ridiculous clutching and
> gearing theories... no sense in starting that all over again.
This has gone on long enough. Just for the sake of the poor slobs in RSS who
might believe this David Courtney diatribe... (Sure posts a lot of it these
days)
He doesn't know jack!
Doug, who this was directed at simply does... and if he has to learn
something goes straight to sources that have already forgetten more than
David will probably ever know. (I have met and ridden with Doug)
Bullwinkle Moose
> You probably can't make a single pipe "efficient" on a triple, but
> that's not really the point.
> The point is that if you want to actually LEARN something it's much
> easier, quicker, and cheaper to modify one pipe and test the results...
than
> to modify 3 pipes and hope you get them all the same.
> You just don't get it! I don't have to ride an old XCR... I choose to
> because I don't want to have to deal with variables like reed valves,
> exhaust valves and digital ignition when I'm experimenting with airbox
> tuning, porting and squish bands.
> For $79/month any moron can buy a fast sled... but you have to
> understand the fundamentals before you can modify one successfully.
> David
>
> P.S.
> I already told you what I think about your ridiculous clutching and
> gearing theories... no sense in starting that all over again.
I would like to see your theories applied to a domestic Polaris twin. If I
brought an XC700 and a basketful of springs, weights, and straight helixes
to Appleton, you wanna give it a try and post the results?
Personally I think you'd have to have some radical (unconventional) weights
to use a straight helix and out-do a setup of conventional weights and a
compound helix.
IMveryHO, helixes became compound to overcome the limitations of
conventional flyweight designs. Those limitations don't really come into
play on a Fuji 600 monoblock, whether 1 pipe or 3. Applying your theory to
a big domestic twin would be a great idea.
David Courtney
Normally I would be happy to help anybody with their sled set-up... to
whatever extent that I can. But it's hard for me to respect the fact that
you switched to an anonymous e-mail address just in time to throw some trash
at me... maybe Michael and Doug can help you out.
Besides, they aren't my theories... they're Olav Aaen's and he put them
in a book that you can read just as easily as I did. If you come away from
reading the book 25 or 30 times cover-to-cover, with a different opinion of
what he meant than I did... then you'll have to try to apply the information
for yourself.
I tried to explain what works for us, but I don't see any great benefit
for myself in helping you make your sled perform better... so I'm afraid
you'll have to take your chances with Mikey and Doug.
I'm not afraid to explain what I believe, and I don't expect anyone to
jump in on my side... but I really don't need to prove anything, either.
Good luck with your new sled,
David
"Bullwinkle Moose" <bullw...@earthlink.net> wrote in message
news:kB8d8.5240$ZC3.4...@newsread2.prod.itd.earthlink.net...
sledhead
> You should go find a stock XLT... no exhaust valves, no reed valves, a
> single exhaust pipe, nothing too complicated... and learn the fundamentals
> of scavenging, compression, combustion, carburetion, port timing, intake
> tract resonance, expansion chamber design... and especially clutching and
> gearing.
> Then come back here and run your mouth when you actually know
> something... so you don't look like such an asshole all the time.
> David
So David... would that exercise on a poorly piped piston port motor really
apply to the motors everyone is using today? Or likewise would digging up an
old OMC case reed twin apply to today's motors?
BTW just for the record even the ancient stock '95 XLT responds well to a
multi-angle helix... for both acceleration and economy. Been there done
that and it works! As does the old piston port 440 I run. Tried straight
cuts and it's a real dog never really warming the pipe. Toss out your
Aaen/OMC training and move up about a decade.
Last I checked - Doug sold off his 1050 Cat he's been running some modded
case reed stuff and has the help of one of the most respected tuners in the
industry.
Bullwinkle Moose
> Don,
> Normally I would be happy to help anybody with their sled set-up... to
> whatever extent that I can. But it's hard for me to respect the fact that
> you switched to an anonymous e-mail address just in time to throw some
trash
> at me... maybe Michael and Doug can help you out.
I can see how you'd think that, but that wasn't the reason. If it was, I
wouldn't ever sign my posts. It is for spam control. It works.
> Besides, they aren't my theories... they're Olav Aaen's and he put
them
> in a book that you can read just as easily as I did. If you come away
from
> reading the book 25 or 30 times cover-to-cover, with a different opinion
of
> what he meant than I did... then you'll have to try to apply the
information
> for yourself.
I have a copy. I've read it many times myself. As you have posted, the
section on compound helixes is not very helpful. It says something like
"try a few and see if they help".
> I tried to explain what works for us, but I don't see any great
benefit
> for myself in helping you make your sled perform better... so I'm afraid
> you'll have to take your chances with Mikey and Doug.
Spare me the misunderstood good guy story. Theories are great. But when
facts/proof have been called for, you have come up empty. When you couldn't
answer a challenging question, you changed the subject, often attacking or
ridiculing the person asking the challenging question.
> I'm not afraid to explain what I believe, and I don't expect anyone to
> jump in on my side... but I really don't need to prove anything, either.
> Good luck with your new sled,
> David
I'm not afraid to read and think about what you believe, either. I think
you're wrong, you do need to prove something. As in, put up or shut up.
I'd like to see proof that your theories work on a Polaris domestic twin.
I don't want any help clutching my sled. I just wanted to see some proof.
I think you are a smart technical engineer type guy. I bet your XCR is
clutched really well for your objectives, and you learned a lot in the
process. I bet you know more about clutching than me. But you posted long
and loud about how the rest of the world is off base and you have the
secret. It's quite a stretch to get from clutching your XCR well, to having
the secrets of the universe.
I don't have an Aaen catalog, so I don't know if he's developed any stuff
for new sleds. If he had a clutch kit for Polaris domestic twin, I bet it
would have a compound helix in the kit.
Here's my bottom line:
If you haven't clutched a domestic Polaris twin, I think you're out of the
loop, and you should not be so quick to throw stones at compound helixes.
It's not the same as a monoblock Fuji. Have you clutched a Polaris domestic
twin?
-Don
David Courtney
I think you're full of crap... how would putting your name at the bottom
of your post have increased the amount of spam you got... Moose?
You guys all tried to explain how and why a multi-angle helix works...
and all you did was contradict each other and stumble around with marketing
hype.
You can get a real good idea about how much somebody knows about
clutches... by how they refer to Aaen's clutch tuning handbook. People who
didn't understand the book or didn't even read it, usually don't understand
clutching either... and they try to dismiss it as worthless or outdated.
People who read and understood it, understand clutching... and learn
something new from that one book every time they read it. They also realize
that the physical laws and principles involved don't change with time, and
that they apply to every engine and every clutch.
Now, did you ever wonder why there isn't a good explanation of how or
why multi-angle helixes work, in the single best source of clutch tuning
information ever published? Do you really think Olav isn't smart enough to
figure out what would happen if you had a 50 degree helix or a 36 degree
helix for either half of your shift curve?
Maybe Michael can tell you... he's really sharp on clutch tuning, can't
you tell? Ha Ha Ha!
I'm not going play hypothetical games about "What would happen if...";
because there are too many variables and it would take way too long. If
that means moving on to the next subject or point of discussion... then so
be it. If you think that because I won't clutch your sled for you, it means
I don't know how... it's fine with me, too.
Besides, I don't think anyone else even cares how clutches really work,
and I'm not going to get into any more arguments about them... so run
whatever you want, Nonni.
David
"Bullwinkle Moose" <bullw...@earthlink.net> wrote in message
news:PKdd8.6055$ZC3.5...@newsread2.prod.itd.earthlink.net...
Doug Miller
> IMveryHO, helixes became compound to overcome the limitations of
> conventional flyweight designs. Those limitations don't really come into
> play on a Fuji 600 monoblock, whether 1 pipe or 3. Applying your theory to
> a big domestic twin would be a great idea.
I agree with you on the flyweight design limitations.
Another way to think about it might be that the flyweights were
designed for low output motors, and things have progressed in the last
10 years.
-Doug Miller
Bullwinkle Moose
> Don,
> I think you're full of crap... how would putting your name at the
bottom
> of your post have increased the amount of spam you got... Moose?
You misunderstand.
I use this address for newsgroups because then I don't get newsgroup-mined
spam at my main address.
> Besides, I don't think anyone else even cares how clutches really
work,
> and I'm not going to get into any more arguments about them... so run
> whatever you want, Nonni.
> David
Just for the record, don't be picking on A. Nooni Moose. That's somebody
else, with a more clever name than I picked. :-)
I probably missed the answer somewhere, have you clutched a Polaris domestic
twin, or a 2000-something liquid twin of any make?
-Don
David Courtney
>;-}
They make a different kind of horsepower and torque than all the other
motors that we play around with. A 130hp Cat twin or a 130hp Ski-doo twin
running at the same rpm doesn't have anywhere near as much torque as those
big, scary domestic built Polaris motors! Ha ha ha! >;-}
I will answer your question if you can tell me what difference it would
make, since my '88 Wildcat had more torque and horsepower than your XC500
has now. Do you think the clutch knows if the motor was built in the U.S.
or Japan... or is it just PFM that makes the Polaris motor so hard for you
to clutch?
For the record, I've never clutched a Thundercat or a '70 Nordic 250...
but the principles apply to both of them equally. Only the numbers
change... the formulas are constant! >;-}
David
"Bullwinkle Moose" <bullw...@earthlink.net> wrote in
<snip>
mmar...@isd.net
David,
Curious, is there a computer program that you run for this or is
it a pure number crunch with the calc? Either case is Aaen's
clutch book what you recommend to learn this art?
Thanks,
Mark
Delano, MN
Dan
I have a serious question. No heckling, no arguments just an honest
question (or two). I've been reading this post and it seems like their
are some extremely knowledgeable clutch tuners here. If this is the
wrong post for this please tell me and I will start a new one on this
specific topic.
I have a 94 Cat ZR580 carbed sled. The engine is stock, stock single
pipe, stock gearing, 192 studs. I have done the carb/jet work and it
runs fine for my temp and altitude (below 1000' in Michigan). I have
been trying to get the clutching right. I have tried a couple different
clutch kits plus a lot of combo's of my own. I have good bushings,
buttons, pins, A arms etc. Both clutches are in good clean working
order. I have a Comet 108C and the stock open face style Cat secondary.
I have been using Cat belts (XXXX-012) and it is in good shape.
I have proper belt drop and clutch alignment.
> The engine is supposed to run at 8200-8400 rpm from what I have been told. I wish I could tell you what combo I have in there right now but can't unless everything is taken apart.
I want it to engage below 5000 rpm and run at 8300 rpm when hammered.
Can you give me a clutch combo to achieve this? I am looking for max
acceleration with as good as possible back shift. I ride on groomed
trails, secondary roads and an occasional lake. I don't plow through
deep snow nor do I do any high mark hill climbing. I am a flatlander
riding flat "hard" snow conditions. I am more of a corner to corner and
drag race type rider. These old ZR's really do corner well, my Fox
shocks are in good shape, recently recharged.
My suspension is set the way I want it. The only thing I'm not happy
with is my clutching.
I have a new 2002 ZL600 EFI. Ideally, I know I can't have it, but,
ideally I would like it to run like my new ZL. I know the engines have
different power delivery curves etc. Here is what I like about the ZL so
much. It engages low, extremely smooth, and can be puttered along at
10-20 mph through the nasty stuff without the feeling that you are
burning a belt. Yet, even with the low (below 4000) engagement it will
pull very hard whenever it is hammered whether you are at a dead stop,
putting along at 10 mph or cruising along at 50-60 mph. It always pulls
hard. My ZR 580 feels like the clutch just isn't squeezing the belt very
hard while puttering through the bumps. It doesn't have the snap or
grunt when the throttle is tickled like the ZL. The ZR doesn't "feel"
fully engaged until about 30 mph. The ZR will run pretty good, and pull
pretty hard from a dead stop when hammered, but just doesn't seem right
puttering along slow. It engages now about 5000, it revs at about
6000-6500 rpms while putting along at 15-20 mph and will rev to about
8000 when hammered from a slow roll. If hammered out of the hole it will
rev to 8200, but not from a roll. My limited knowledge tells me the back
shift isn't right (helix ?) and I probably don't have the correct A arms
because of the vague feel while going slow.
What should I change first? Then second etc., or do you know what set
up I can install to give me positive feel while going slow, smooth
engagement, and consistent rev WHENEVER hammered regardless of sled
speed (like the ZL does).
I have toyed with the idea of pulling both clutches and belt off the ZL
and slipping them on the ZR and see if that is the magic combo I'm
looking for, but, since the ZL has more power and torque plus power
valves, I thought it could be a waist of time (something I don't have to
begin with). The ZL revs to 8300 when hammered, cruises along at under
5000, engages below 4000, yet pulls and runs great WHENEVER you nail it.
Please help me out.
Thanks.
Dan
David Courtney
book... just to get an idea of the relative importance of the different
parts and their effect on different parts of the shift curve.
For instance, on any given sled... a 36 degree helix provides 1.5x as
much belt side pressure as a 46 degree helix. No matter how much or little
torque you apply, the relationship is the same.
The "magic" if there is any; is in determining how much side pressure
you actually need!
David
<mmar...@isd.net> wrote in message
news:u7mof52...@corp.supernews.com...
Doug Miller
> I have a serious question. No heckling, no arguments just an honest
> question (or two). I've been reading this post and it seems like their
Fair enough. I really try to stick to DISCUSSSIONS. I figure I've
"won" when the other guy starts calling me names....
;-) ;-)
> I have a 94 Cat ZR580 carbed sled. The engine is stock, stock single
I've owned 2 different 580zr cats, and ridden several others. One that
I spent some time on won several pro class snocross races, and
specialized in Hole Shots. A killer snocross setup sucks IMHO for the
normal rider though.
> > The engine is supposed to run at 8200-8400 rpm from what I have been told. I wish I could tell you what combo I have in there right now but can't unless everything is taken apart.
8200 max. No more. You should be able to read the helix angle if you
roll the sled forward carefully and watch the helix. I bet it is
something like a 50 or so.
> I want it to engage below 5000 rpm and run at 8300 rpm when hammered.
> Can you give me a clutch combo to achieve this? I am looking for max
Sure. Make sure you DO NOT have notched weights. If you do not have
notched weights, you set the engagement with the primary spring. Used
to be we ran the yellow/green on everything. It might engage a little
higher then you want though. Great starting place is engagement. Set
it with spring. Your dealer should have a chart.
Actually, a better place to start is primary clutch. If you are
running anything other then a 9 tower clutch on a cat twin 580 or
larger, IMHO you are on borrowed time before the clutch explodes and
takes out the belly pan, hood, crank, and guard. They are like 250
bucks or something, and all your internal parts interchange.
> hard while puttering through the bumps. It doesn't have the snap or
> grunt when the throttle is tickled like the ZL. The ZR doesn't "feel"
Part of that feeling is the lower grunt of the EV motor. Also, because
it is EV, you get away with lower engagement.
Part of it is the roller secondary. The Roller secondary really makes
sleds feel snorty. On my 800zrt, when I changed from a button to a
roller, the sled went from a big lazy overpiped triple to a snorty
hang on out of the corner instant rocket.
When going from button to roller, back up 2 degrees helix. If you now
have a 51, try a 49. Also, don't be afraid to run a stiffer secondary
spring at the same time - whatever spring is in the 600 would be a
GREAT place to start.
Used to be a roller cover was about 100 bucks, and used helixes were
20 bucks. Best money you could spend.
> What should I change first? Then second etc., or do you know what set
> up I can install to give me positive feel while going slow, smooth
> engagement, and consistent rev WHENEVER hammered regardless of sled
> speed (like the ZL does).
Two approaches. Try a softer primary spring. This will lower
engagment, and make it more "civilized", but lazier then it is now.
Then try just swapping secondaries. I bet by this point, it is
snortier, but won't rev up high enough. Then try dropping 2 grams
weight, and see where you are at.
> begin with). The ZL revs to 8300 when hammered, cruises along at under
> 5000, engages below 4000, yet pulls and runs great WHENEVER you nail it.
That is the goal. I don't think you will get there with button
secondary. And I don't think your 580 will ever be as snorty as the
600. But you for sure can improve the 580.
If you want to try something really lazy, and easy, and cheap, try
tightening the secondary spring one or two holes. This is NOT a cure
all, but should up your RPM a tad, and help backshifting some. Not as
good as a good roller setup, but still might help some.
Good luck, and let me know if this helps!
-Doug Miller
Karl Shoemaker
I'm not the expert; but I'll tell you what I've been running;
and thanks to the others for input on this, here, fine newsgroup.
New (4 months) 9-tower, new yellow/green spring, new 49.5 gram weights,
original secondary is yellow spring, middle hole, original non-roller
type.
From a stop and punch it engages at 4500, then runs right up to 8200 all
the way to 75, then I chicken out. (will go faster). Folks tell me the
roller secondary is better, but I'm ok for that, for now. Only one
change is I geared down one. Now running a ratio of 2.15 with 19/20
gears.
Only non-stock is the fact I'm still running the heaver wieghts combo
with the
higher sping, but I like the effect. In deep powder (and getting
unstuck)
I don't wanna spin the track at that point. I set this up for hill
climbing, but this'll give you an idea what mine does on the flats,
around 3000-6000 altitude. One change I *might* do later is go lighter
on the primary weight, 'cause most of my screaming is done above 5000
feet, and with current wiidghts my rpm drop to 7800-7900 at that
altitude, which is expected with a 580 engine.
This doesn' mean much for your application, but my track speed in the
deep
powder going up hill is 42 mph. I think I've reached the limits of my
sled,
and I'm happy with it, for what it is :) :)
Karl
'97 Powder Special- carbed.
for info and email click on:
http://www.dalek.org/srg
David Courtney
The big difference between your two sleds is that since the whole
snowcross thing has gotten to be so popular; clutches are being set-up to
give the illusion of better backshifting that the magazine writers love.
By using stiffer secondary springs, they make the clutch less torque
sensitive... which keeps it from shifting up under light loads; so it is
always ready to "rev" like you describe. This is similar to driving around
town with your automatic transmission car in "2" instead of "D"... it feels
more responsive, because it can't shift up under light loads.
There is a downside... which is that it's not a very efficient way to
run either vehicle. You sort of get away with it on a snowmobile because
eventually the weights will force it to shift as your speed increases; but
at light loads it revs more than it needs to. The bad thing is that at high
speeds when the clutch is shifted out and the spring is wound even
tighter... there's a lot more side pressure than you need to keep the belt
from slipping; which gets turned into heat.
I guess the bottom line is that if you're willing to give up some belt
life, top speed and fuel economy in exchange for the "revvy" feel... then
you can run a stiffer secondary spring and higher helix angle, to make the
clutches less torque sensitive.
The most important thing to realize is that there's a big difference
between actually "backshifting" and simply not "upshifting". A sled with
good backshifting will not lose rpm's when you run off the beaten path into
some wet snow; but it won't necessarily be "rev'd up" at part throttle and
low speeds. The Snowcross style clutch setup actually forces the clutches
into a lower ratio than necessary, in order to make them more responsive out
of the very slow speed corners... not a bad thing unless you spend a good
portion of your time cruising or running at high speeds.
Also, if the ZR engages at 5,000 rpm... the belt can't fully engage
until about 20 mph; but with a 4,000 rpm engagement the ZL would fully
engage the belt at about 15 mph. There isn't much you can do about that,
unless the ZR has the grunt to pull from down at 4,000 rpm.
David
"Dan" <dsto...@ford.com> wrote in message
news:3C7B98C2...@ford.com...
>
Doug Miller
> I guess the bottom line is that if you're willing to give up some belt
> life, top speed and fuel economy in exchange for the "revvy" feel... then
Could you explain the above? I don't see where you have described why
a motor burns more gas, goes slower, or eats belts with the proper
helix?
IMO, you can have your cake and eat it too. You can have a hole shot
without overrev, and still have backshifting with the proper clutch
setup. That is what a multiangle helix is all about for the bigger
motors.
Very probably a 580 cat does not need a multiangle helix, and I didn't
recommend one. I think the cat, which has about 25 more horsepower
then a stock XLT and better clutch weight selection, can be very happy
with a straight helix, especially with a cat roller secondary.
-Doug Miller
Doug Miller
> Years ago, I ran a bunch of spreadsheets using the formulas in Aaens
> book... just to get an idea of the relative importance of the different
> parts and their effect on different parts of the shift curve.
> For instance, on any given sled... a 36 degree helix provides 1.5x as
> much belt side pressure as a 46 degree helix. No matter how much or little
> torque you apply, the relationship is the same.
> The "magic" if there is any; is in determining how much side pressure
> you actually need!
> David
That's the easiest part of all. You need enough belt pressure that the
belt doesn't slip in the secondary or primary. Too much makes the
belts run too hot.
-Doug Miller
David Courtney
You don't understand what the various parts of the clutches actually do,
you don't understand what the various portions of the shift curve are
supposed to look like, and you don't really even understand what all of the
common terminology really means.
You've chosen not to read Olav Aaen's book... and you don't understand
how clutches actually work; that's not a big surprise. But, it's not my job
to re-write that book in kindergarten level terms just so you can follow
along without having to think for yourself.
I suggest you either read the book, or don't waste your time reading
what I write here... but either way I'm not going to play your game. You
don't need to keep telling me what you don't understand... it's called
clutching and I'm not going to teach you!
David
"Doug Miller" <dmi...@foresightpartners.com> wrote in message
news:32b6c9cc.02022...@posting.google.com...
Daniel Stolarczyk
torsion (or both) ? I have the yellow sec spring now. What color would this
"stiffer" spring be?
Dannews:a5gou8$78adn$1...@ID-70857.news.dfncis.de...
Bullwinkle Moose
I believe this is all about a difference in personal preferences. (And the
method of advocating those preferences, to be sure).
You prefer efficient, "all-purpose" clutching, for lack of a better term.
And there's nothing wrong with all-purpose clutching. Aaen's book is a
bible for that style of clutching.
(Some, many?) others prefer what you derisively call "snocross" clutching.
I first crossed swords with you when I questioned the priority you placed on
belt efficiency. You seemed to think that questioning the goal of having
the best belt efficiency was absurd. I wondered if belt efficiency was a
false god.
This week when you gave the example of diving off into deep snow, you said
the clutching should not lose any rpms. That's when I realized you are
clutching for efficiency. (OK, so I'm slow. I thought there was some
deeper clutching secret being offered). It is a worthy goal, but there are
compromises in all clutching setups.
My "snocross" clutching probably does not get the best MPG. It probably
does not have the best belt efficiency, I would admit that I don't really
know and don't care. I may have too much belt squeeze, also don't know,
don't care. I don't dive off into deep snow very often, and when I do, I
don't care if it loses 200 rpms. I can take care of that with my right
thumb. So, those are my compromises, or at least they might be. I'm not
sure that I'm not having my cake and eating it too. But I'm willing to
accept those possible inefficiencies, because...
On the other hand, it is a blast to drive corner to corner. And I have
out-dragged sleds of 10, 15, and even 20+ HP more than mine with similar
weight riders. Which caused me to grin till it hurt. My snocross clutching
must have been better than their clutching, for the purpose at hand.
Instead of ridiculing people and assuming they are ignorant for not
listening, maybe you should listen to what they are trying to tell you.
You have apparently mastered one style of clutching. There are other styles
and whether you or Aaen like them, they "work" for certain preferences.
Miller doesn't want you to teach him anything. He wants you to stop acting
like you know that his style of clutching doesn't work, when in fact it
works for him and many others but you just_don't_like_it.
Someday you're gonna want to use a multi-angle helix, and Doug Miller's not
gonna let you.
:-)
I think I'm done. I've figured out what you were trying to say.
-DON
David Courtney <adv...@powercom.net> wrote in message
news:a5h8od$7ckjj$1...@ID-70857.news.dfncis.de...
Doug Miller
> angle on the race truck and got rid of that stiff green spring in favor of
> the stock yellow one. By making the clutch more torque sensitive... we
> reduced our lap times only slightly; but our belt life went from under 40
> laps to over 400! >;-}
More likely you had too much belt squeeze at lower MPH, and you were
wearing the belt out due to this.
yeller spring on cats works fine for button clutch up to 700cc twin,
is marginal on roller for 700cc twin, and will not work for 800cc
triple roller setup in the mountains.
> I know that's not really a clear explanation... but it gets pretty
> complicated when you try to break out individual items, because they're so
> interdependent.
Yeah. We're all stupid, and the magic goes away when you try to
examine it.
-Doug Miller
Doug Miller
Howdy,
> (Some, many?) others prefer what you derisively call "snocross" clutching.
I don't like the term "snocross clutching"....
> the best belt efficiency was absurd. I wondered if belt efficiency was a
> false god.
I think it is.
> This week when you gave the example of diving off into deep snow, you said
> the clutching should not lose any rpms. That's when I realized you are
> clutching for efficiency. (OK, so I'm slow. I thought there was some
> deeper clutching secret being offered). It is a worthy goal, but there are
> compromises in all clutching setups.
The ULTIMATE clutching, IMO, has no compromises except the time
committment to find it. Mebbe it cannot be achieved, the but the GOAL
is no compromises.
> On the other hand, it is a blast to drive corner to corner. And I have
> out-dragged sleds of 10, 15, and even 20+ HP more than mine with similar
> weight riders. Which caused me to grin till it hurt. My snocross clutching
> must have been better than their clutching, for the purpose at hand.
That is the goal. I believe that you can clutch a sled that is mild
mannered on the trail, back shifts like a DREAM, does NOT overrev on
hole shot, engages nicely, and wanders down the trail like a civilized
4 stroke.
I think you can do all this, and have it so that when you launch up in
the air with the throttle WFO, the RPM holds steady, and when you
land, it drops 50 RPM (no more) that no one else notices and holds
steady.
And, when you show up and someone wants to drag race, your buggy
engages nicely but positively, and you gain 2 lengths on EVERYONE in
the first 75 feet. After that, the clutch holds the CORRECT RPM, and
it is up to the motor to pull on by.
When you go to a different altitude, like 4000 feet different, I
change main jets and primary weights and it STILL WORKS AWESOME.
The clutching on my sled does all this. It uses factory polaris
weights. It uses factory springs (not necessarily the ones that came
on the sled). It uses a custom ground helix developed by a buddy named
Jack Struthers, and sold to MANY MANY customers all over the country
with super success. He only builds them for Polaris 700 and 800's. The
2001 and 2002 have different helixes. They work in Utah. They work in
Minnesota, They work in Idaho. They work in Washington. They work in
Colorado. To order, call 208-853-5550, and ask for parts. They take
credit cards.
> Miller doesn't want you to teach him anything. He wants you to stop acting
> like you know that his style of clutching doesn't work, when in fact it
> works for him and many others but you just_don't_like_it.
I think you have this one right.
-Doug Miller
Rob Pilgrim
Do you have any online resources that discuss intake tract resonance in-depth?
I'm referring to airbox design.
Email me off list.
-Rob
"David Courtney" <adv...@powercom.net> wrote in message news:<a4ttlb$32cqn$1...@ID-70857.news.dfncis.de>...
> You should go find a stock XLT... no exhaust valves, no reed valves, a
> single exhaust pipe, nothing too complicated... and learn the fundamentals
> of scavenging, compression, combustion, carburetion, port timing, intake
> tract resonance, expansion chamber design... and especially clutching and
> gearing.
> Then come back here and run your mouth when you actually know
> something... so you don't look like such an asshole all the time.
> David
>
>
>
> "Doug Miller" <dmi...@foresightpartners.com> wrote in message
> >
> > Racers, hill climbers, OEM's, and yur basic redneck are all famous for
> > buying marketing hype and letting the other guy win in order to
> > maintain the big multi-angle conspiracy.
> >
> > I don't know how to clutch a stock 95 XLT. Why don't you admit you
> > don't know how to clutch something with over 120 horsepower?
> >
> > -Doug Miller
tYLER tINGLE
Is this of any help?
If ya get any others I would be interested as well.
Tyler
"Rob Pilgrim" <robpi...@adboivin.com> wrote in message
news:f69299b8.0202...@posting.google.com...
David Courtney
long belt life... as long as you're willing to sacrifice those three things;
you can run the "snowcross/dragrace" style of clutch set-up... like I've
been saying over and over.
Generally, most people who ask clutch tuning questions here are not
willing to give up those three things... in fact one or all of those three
things is usually what they're looking to improve; so that's why I recommend
the things that work to improve those three things.
Unless you actually snowcross or drag race... there's very little
benefit to giving up efficiency just to have a "revvy" feel. In fact,
unless you run very short races or corner at extremely slow (track locked up
like in snowcross) speeds... there's virtually no performance benefit to
running your clutches excessively tight.
But like I said before... run whatever makes you happy,
David
"Bullwinkle Moose" <bullw...@earthlink.net> wrote in message
news:s8Ze8.19172$0C1.1...@newsread1.prod.itd.earthlink.net...