why are "A" arms better than trailing?
sled...@hotmail.com
be better than trailing arm suspensions?
what is the significance of "unequal"
length A arms?
any insight is appreciated!
Josh
on this topic.
Adrenaline Grin
> why are "A" arm suspensions supposed to
> be better than trailing arm suspensions?
As the trailing arm suspension moves up & down through it's travel, the
spindle angle changes. On an A-Arm, spindle angle never changes. The rake
& trail angle of the spindle is critical, if it changes, you end up with
"bump steer". Anyone that knows about motorcycle frame/fork rake&trail
geometry will know what I'm talking about here.
The early automotive engineers abandoned it in the early 1900s, because they
realized how it's design limitations will affect handling & tire wear. You
still see the trailing arm designs in automotive applications, but usually
only for non-long travel applications. It can be very durable & heavy duty,
that's why you'll still find it on Ford's 'I-Beam' front ends. But if you
want long-travel, that's where the problem magnifies.
Arctic Cat realized the design limitations, and abandoned it just like the
early auto manufacturers did. That's why whenever I ride a trailing arm
sled, it feels more like a truck, than AC's race car feel. It's about time
the other brands are jumping on the A-Arm bandwagon.
I have a bad feeling that for the last 20 years or so, the trailing arm sled
manufacturers have been riding on their loyal consumer's faith/loyalty
blindness all along. Because they could easily have adopted the A-Arm 20
years ago, taking the cue from early automotive lessons just like AC did.
AC claims 'Indy Car' front end, but the fact is A-Arms were around half a
century before Indy cars existed. AC can claim no more credit than only
being first to bring it to production sleds. Because there were other
prototype A-Arm sleds in the '70s that never made it, due to the extinction
of many of the more than 100 brands that once were.
There was no need to force trailing arms onto their faithful PolYamDoo
consumers. As a result, you have some consumers really believing trailing
arms are superior because of brand loyalty blindness, and the company's
advertising propaganda. I've always liked the other brands, the only thing
that ever kept me from buying one was that after riding an AWS sled, there
was no comparison. My goal is to own one of each company's fastest sled.
A-Arm sleds only of course. So it looks like I may one day have the best of
each brand. I can't wait!!!
> what is the significance of "unequal"
> length A arms?
As the suspension compresses, the spring rate doesn't increase. If they
were the same length, the spring would get harder and harder as the arms
reach their compressed end of the travel. Unequal length A-Arms allow a
constant spring pressure throughout the entire travel stroke. If you
represented it on a graph, the spring rate would remain a straight line.
Adrenaline Grin
Magnus Stålnacke
Well..better?
First of all, and maybee most obvius, it is a stronger and not
so crash sensitive construction, espcially on the race track
where you may bump into each other, you dont win races whith
bent trailing arms.
Then there is the question of unequal arms, not nessecerily
just A arms, you can have unequal rods on the Polaris type too.
The reason to have unequal arms is an effort to get constant
width between right and left ski. If you look at an an old
Polars you see that they get wider when the suspension is
compressed, look on the trailer when you tie it down.
And the roll center vill also get effected by different
angels and length of the rods, rollcenter is the point that
the chassis leans around when you are turning. The old
Yamaha´s had the roll center at ground level, and thats wy
they felt as they had a high c of gravity and most likely
the reson to why they abandoned that construction. If you
in theory could get the rollcenter above the C of gravity
you get a chassis that leans inward when you turn, comfortably
but easy to tip over.
There is a lot more to it than this, but time and my english
wont allow me to explain it properly. Maybee someday i make a
webpage about it, where i can have some drawings.
Magnus Stĺlnacke
http://w1.970.telia.com/~u97007522/
Rob Pilgrim
sled...@hotmail.com wrote in message news:<3c58b9be....@news-server.twcny.rr.com>...
FormulaPro
mixgreg
The other three sled manufacturers would have to buy a patient to be
able to use "A" arms. If they had a patient they all would be using
it. Yamaha had to buy it from FAST for their new sleds. "A" arms are
much better. The cost of buying patient rights from AC or someone else
stops them....... AC, I've been told, has sued and won, to keep "A"
arms off other sleds.
Adrenaline Grin
> I agree with what Adrenaline Grin said, he explained it very well.
Thanks dude! I learned about some of these issues when I went through the
learning curve while building FrankenSled.
> The other three sled manufacturers would have to buy a patient to be
> able to use "A" arms. If they had a patent they all would be using
> it.
Really? I was unaware of that. I thought patent stuff on A-Arm tech would
have long been over since the automotive industry adopted it many years ago.
Oh well... Ya learn something new every day! :) Thanks for enlightening
me!
Too bad the 'other three' didn't seize the opportunity while AC was
non-existant in the early 80's! That would have been their window of
opportunity.
> Yamaha had to buy it from FAST for their new sleds. "A" arms are
> much better. The cost of buying patient rights from AC or someone else
> stops them....... AC, I've been told, has sued and won, to keep "A"
> arms off other sleds.
Abslolutely wild!!! I was totally unaware of the legal 'behind the scenes'
stuff. I had no idea!
I was kind of looking forward to one day owning a top end A-Arm sled, one of
every brand. I hope this patent stuff doesn't get in the way.
Adrenaline Grin
Andy Dragon
"Adrenaline Grin" <%20h...@canada.com> wrote in message
news:G_d68.402$gH5....@newscontent-01.sprint.ca...
> Really? I was unaware of that. I thought patent stuff on A-Arm tech
would
> have long been over since the automotive industry adopted it many years
ago.
> Oh well... Ya learn something new every day! :) Thanks for enlightening
> me!
Patents are quite silly. If you change the application enough, you can
re-patent it. The adaptation from wheels to skis and cages to sleds was
enough of an application change to warrant a new patent.
--
~Andy
'01 Kawasaki KX 250 / '01 Honda CR 125
'02 Skidoo MXZX 800 / '00 Skidoo MXZX 600
'99 Seadoo GSX Limited
and more...
David Courtney
isn't too difficult to get zero bump steer if that's what you think you
want. Although typically you want a small amount of "toe-out" on landing to
help stabilize the sled.
There should actually be slightly less "scrub" with the trailing arm
(but it's about the least important of all the design considerations) than
with the A-arms simply because the radius rods on the trailing arm set-up
can usually be made longer than the A-arms can. It has more to do with the
fact that the A-arms concentrate the suspension loads in a smaller area, so
the bulkhead has to be more massive and rigid than on a trailing arm
set-up... requiring the mounts to be spaced further apart normally.
The main reason for unequal length A-arms or radius rods is that you can
design in a "gain" in camber as the suspension compresses... so that when
the sled leans "out" in a corner, the outside ski will remain more vertical
instead of tipping "in" when the body rolls. This keeps the ski bottoms and
carbides planted on the ground for better cornering.
However, if you do something dumb like Polaris did with the CRC front
end... you end up with a roll center that moves all over the place, and the
sled will feel "unpredictable" during hard cornering. It looks like the
ADBovin front end kit would actually correct a lot of that instability, and
make the sled more fun to ride hard.
With equal length a-arms or radius rods... you had to start out with
excessive camber, so that when the sled leaned the carbides would still be
pointing "outward", otherwise the sled would push in the corners.
The main advantage of the trailing arm (I believe) is that it spreads
the suspension loads out further on the chassis... which is probably equally
offset by the main advantage of the a-arm which is that the caster angle
doesn't increase as you compress the suspension the way it does with a long
travel trailing arm.
Personally, I think any advantages are in marketing, cost and weight.
There is a myth about the "Indy Car" style a-arm suspension being so far
superior. You have to realize that aerodynamics are a huge part of Indycar
racing and moving the shocks and springs inboard and using bellcranks to
actuate them makes the car much more aerodynamic... but we aren't going fast
enough to realize that benefit.
These are only my opinions, based on what little I know about front
suspension designs.
David
"FormulaPro" <malatestaREMO...@mediaone.net> wrote in message
news:3C595F1A...@mediaone.net...
RBTool
> I'm willing to bet very few can answer you correctly.
>
So Rob, what are you waiting for?? let us know!!!!!!!
Everbody listens to your comments!! Atleast I always do!!
Randy
RBTool
Sasquatch
>
>
>
"Andy Dragon" <andy_drag...@hotmail.com> wrote in message
news:a3brgt$173se1$1...@ID-105861.news.dfncis.de...
Bobby Greene
http://216.37.204.202/Skidoo_OEM/skidoo.asp?Type=13&A=62&B=17
--
Change "at" to @ to reply.
Damned Spam!
Bobby
"mixgreg" <mix...@isu.edu> wrote in message
news:3C59650D...@isu.edu...
Snowjacks
one out.
It's all about caster and camber. In a trailing arm suspension, or an EQUAL
length A-arm suspension (aka the simple parallelogram), the camber angle of
the ski spindle (or wheel) changes with body roll that occurs during
cornering. This effectively moves the center of contact of the ski (or
wheel) toward the inside of the turn, reducing surface contact and loading
the edge of the tire or ski. This in turn causes the ski or wheel to push,
or understeer. Unequal length A-arm suspensions provide a camber
correction, which maintains optimal ski (or wheel) contact forces along the
centerline under all conditions.
With any A-arm suspension, the caster angle (or rake) will constantly change
as the trailing arm and spindle centerline move through an arc. This causes
the suspension designer to compromise and design for the worst case caster
rather than the optimum. The design for worst case is driven by the fact
that adverse caster will cause horrible and uncontrollable front steering
oscillation (the reason that many large trucks use massive steering
stabilizers). Caster is important for steering stability, on-center feel,
and steering effort. With any A-arm setup (equal or unequal), the caster
angle is relatively constant throughout the limits of suspension travel and
the designer is better able to optimize caster, in turn optimizing effort,
feel, and stability.
Both caster and camber changes are aggravated in a long travel trailing arm
suspension, and become more critical on vehicles that carry a higher
front/rear weight bias. In the early days of trailing arm suspension, total
travel was only 3-4.5 inches, so there was no significant advantage to be
had with unequal length A-arms that would justify the higher cost. Now, as
companies push front travel to higher numbers to keep up with the
ever-increasing rear suspensions, the advantages of unequal-A start to
become significant. The move to unequal-A clearly signals the beginning of
a new era of ultra-long travel front suspensions, especially in front heavy
four-stroke sleds, IMHO. It was no accident that Yammie threw out the
trailing arms for the RX-1.
<sled...@hotmail.com> wrote in message
news:3c58b9be....@news-server.twcny.rr.com...
Andy Dragon
"Sasquatch" <Sasqua...@excitenospam.com> wrote in message
news:a3ctcf$dns$1...@news.dryden.net...
> Then explain why is Yami and Doo going to A-arms? Are they going to be
sued?
Patents expire after 30 years. Watch, everyone will adopt A-arms within 2
years.
--
~Andy
Doug Miller
This saddens me, and makes me question my sanity, but I agree mostly
with Mr. Courtney.
> No. You can design more or less bump steer into either set-up... and it
> isn't too difficult to get zero bump steer if that's what you think you
> want.
He's right on the above.
> There should actually be slightly less "scrub" with the trailing arm
> (but it's about the least important of all the design considerations) than
> with the A-arms simply because the radius rods on the trailing arm set-up
He's mostly wrong on the above. You can design no scrub into most of
the systems, but there are compromises.....
> can usually be made longer than the A-arms can. It has more to do with the
This is important.
> The main reason for unequal length A-arms or radius rods is that you can
> design in a "gain" in camber as the suspension compresses... so that when
> the sled leans "out" in a corner, the outside ski will remain more vertical
> instead of tipping "in" when the body rolls. This keeps the ski bottoms and
> carbides planted on the ground for better cornering.
The above is true.
> However, if you do something dumb like Polaris did with the CRC front
> end... you end up with a roll center that moves all over the place, and the
> sled will feel "unpredictable" during hard cornering. It looks like the
I don't know about the above here. I do know the blade sucks in this
regard. Rollcenter moves about, which is why they compensate with
their falling rate swaybar (which is probably patentable I'd think).
Look at their very short A-arms, and super long travel, and the fact
they have maintained camber and some scrub pretty much guarantees
their RC wanders about a bit. Solving that with a sway bar that chases
the RC around is a very creative approach to a very old problem.
> With equal length a-arms or radius rods... you had to start out with
> excessive camber, so that when the sled leaned the carbides would still be
> pointing "outward", otherwise the sled would push in the corners.
Exactly right. If you think about the sled leaning out in a corner,
the unequal length a-arms help keep the ski perpendicular to the
ground, instead of the skis leaning out. this gives them more bite.
> The main advantage of the trailing arm (I believe) is that it spreads
> the suspension loads out further on the chassis... which is probably equally
> offset by the main advantage of the a-arm which is that the caster angle
> doesn't increase as you compress the suspension the way it does with a long
> travel trailing arm.
One major thing about the trailing arm. Everyone is ALL excited about
the a-arm over the trailing arm.
In reality, the trailing arm is a SUPER LONG a-arm suspension. Caster
is not as significant a concern for skis as it is for tires, so the
trailing arm is very successful for sleds, where it wouldn't be as
successful for race cars. Longer arms are for sure an advantage.
> Personally, I think any advantages are in marketing, cost and weight.
I think there is an advantage in suspension, or can be.
> There is a myth about the "Indy Car" style a-arm suspension being so far
> superior. You have to realize that aerodynamics are a huge part of Indycar
Also, spend some quality time looking at the rear of a formula car.
they often have a pseudo trailing arm system, albeit using two links,
that attach almost at the main hoop.
Back to A-arms for a minute. There are a bunch of things you trade off
in suspension design.
1 - Packaging - the final product has to be able to be made.
2 - Simplicity - see above comment
3 - Camber gain - the camber change in the ski/tire camber angle has
to at least exceed the body lean. I would bet this is much more
critical on a racing slick then a ski.
4 - Roll center - roll center cannot move right left, and should move
very little up and down through the full range of motion.
5 - Scrub - Scrub should be maintained at a minimum. Probably more
important in a snowmobile then most folks think.
6 - Travel - Pretty easy to do all the above with 3 inches of travel.
Harder if you are after 10 or so.
7 - See 1 and 2, and start over.
The traditional simple trade off has been camber, roll center, and
scrub. When all done, you always end up with a shorter top rod then
bottom, and often have the top and bottom rods parallel at mid travel,
and there is a ratio of the differences in length of rods combined
with distances between them combined with mounting points on the ends
which is calculated by computer programs for given design paramters.
And then you go back to 1 and 2.
After that, you have to mount the shock/spring. Hopefully linear if
not rising rate. Finally, figure out some ackerman in the spindles,
and then mount the rack, then figure heighths/lengths to get rid of
bump steer and maintain your ackerman.
One thing you find early on in this process is that the longer you can
make the a-arm legs, the easier it is to control all the angles, and
add travel.
YMMV.
Doug Miller
Boise Idaho
Willing to be rodereport tester
Stevem...
Thanks for that informative reply... I know it takes a lot of time and
effort for all that...
I have been wondering something though for a long time. Why is it that
motocross bikes have a suspension on the front wheel that is like the old
Yamaha pogo stick front end. It seems to me that if there was something
better for motocross they would have used it by now. Is there a
possibility of something else that could be developed that would be better
for bikes as well as sleds ? Something like a combination suspension. Like
a pogo stick front end along with a A-arm type. Something to say distribute
the shock loads to different points at the chassis. Like you said something
about how the trailing arm is basically a long A-arm. Thoughts ?
--
L8tr...
Steve m...
web page: http://www.telerama.com/~stevem52
L.H. Club page: http://www.geocities.com/yosemite/7925
"Doug Miller" <dmi...@foresightpartners.com> wrote in message
news:32b6c9cc.02013...@posting.google.com...
Snowjacks
radius. Since we are neither braking nor accelerating with the skis on a
snowmobile, plus we are not generally dealing with split-coefficient
surfaces, I for one fail to see how scrub radius is that critical. Since
the inclination steering angle of the spindle (aka the kingpin angle) tends
to be small and the distance from the ski pivot to the bottom of ski is
small, and the centerline of the spindle is coincident with the centerline
of the ski, the scrub can be very near zero on either a trailing arm or
unequal-A arrangement.
Please explain your view on why scrub is important.
"Doug Miller" <dmi...@foresightpartners.com> wrote in message
news:32b6c9cc.02013...@posting.google.com...
sled...@hotmail.com
everything I wanted and needed to know
about A-Arms!
Thanks to all!
Magnus Stålnacke
>
> Doug,
> Thanks for that informative reply... I know it takes a lot of time and
> effort for all that...
> I have been wondering something though for a long time. Why is it that
> motocross bikes have a suspension on the front wheel that is like the old
> Yamaha pogo stick front end. It seems to me that if there was something
> better for motocross they would have used it by now. Is there a
> possibility of something else that could be developed that would be better
> for bikes as well as sleds ? Something like a combination suspension. Like
> a pogo stick front end along with a A-arm type. Something to say distribute
> the shock loads to different points at the chassis. Like you said something
> about how the trailing arm is basically a long A-arm. Thoughts ?
>
sides, left and right and this causes the rollcenter problem.
The old Yamaha´s had the rollcenter at ground level and a constant
camber angle, not good.
Pogo stick combined with A arm is called MacPherson and the
MacPherson type suffers also from a low RC. On a personal car
it is ok with a low RC you compensate that with a pretty stiff
swaybar. But in a terrain vehicle you dont want that, on a
snowmobile you want left and right to move as freely as
possible compared to each other without the body roll when
cornering, that calls for a bit higher RC. The snowmobile
also have the problem of the rear RC moving 38 cm from side
to side of the track at groundlevel.
I think we will see Polaris radius rods in different lengths
and different angles, even defferent on different models in
the future. Most things you can acheieve with A-arm you can
do with the trailingarm type too.
Magnus Stĺlnacke
Adrenaline Grin
In my original post, where I mentioned spindle angle, I wasn't referring to
camber, roll center, etc. Rather, I was referring to the front to rear
angle of the spindle. As long as you have a trailing arm, the
forward/rearward angle of the spindle changes throughout the travel stroke.
This is what I was originally referring to in my original comment about rake
& trail geometry. And of course, camber & roll centers are important too,
and the other posts claiming that it can be designed accordingly are for the
most part correct.
If trailing arms can be as good as A-Arms, I welcome the day where I can
witness it for myself when playing 'trade a sled' with my buddies. So far,
there hasn't been a single trailing arm sled to date that I've ridden that
has matched AC's front end. And that's since I started riding way back in
'67. I've ridden just about everything out there, and would welcome equally
good handling choices from other brands. But to date, this has not yet
happened.
Check into Bike rake & trail geometry specs/info, by looking at motorcycle
specs regarding fork & frame geometry. It's not as critical to skis in the
same way it is for a wheel. But the fact remains that when you have a
trailing arm, the rake & trail of the front spindle changes drastically
front/rear from the ideal when you apply long travel.
As long as that trailing arm draws an arc throughout it's travel, you're
going to get some bump steer. If they could have designed it as close to
zero as AC did, then why haven't they done it yet??? I have a funny feeling
it's an inherent design limitation just like the AC engineers claim.
Someone mentioned in this thread about rear wheels on some Indy cars having
a trailing arm setup, and it works perfectly. I agree with that. Mainly
because as long as the wheel doesn't have to steer, and run inline with the
chassis only, it never will be a problem. My '67 GMC pickup had a trailing
arm type of setup in the rear. It worked great! No bump steer at all!!!
: )
Adrenaline Grin
David Courtney
ski moves in or out when you move the suspension up and down.
David
"Snowjacks" <snow...@provide.net> wrote in message
news:M6p68.241374$TC1.16...@bin5.nnrp.aus1.giganews.com...
Adrenaline Grin
> good handling choices from other brands. But to date, this has not yet
> happened.
Correction...
It has happened... Doo & Yam may by worthy choices, and even the little
OEMs, like the Blade now have A-Arms. But I won't make the jump unless it
has more than two cylinders with FICHT DFI.
Adrenaline Grin
Doug Miller
Like David said, I was talking about center to center distance changes
with the skis facing forward - not scrub where the thing is turning.
I really don't know how important scrub is. Seems like though that if
you were to launch into a snocross corner, and the outside ski were to
hit first, then the suspension start to collapse, it might kinda load
the suspension arms pretty hard if the center to center got wider as
the suspension collapsed - hit something harder then soft snow, and
something is gonna have to give.
In an offroad race buggy you've got tire sidewall to take some of the
movment.
But that is mostly conjecture no my part, and a fleeting comment that
someone who knows more then me made a while ago. I thought the same as
you. He disagreed, and he is in a position to know, and I listened.
I'd be very interested to here another point of view, and why.
-doug miller
Stevem...
roll-centers.. I wonder if the Snow Hawk has taken advantage of one part
of that with the curved track in the rear. To make it handle more like a
bike would due to the curved (more like a wheel track). In our ever ending
quest for the perfect suspension setup we seem to have appreciated the A-arm
front ends more than the trailing arm system. As always, the best selling
design wins out of the technologically superior design. (or does it in this
case ? ) I have ridden all brands with varying designed front ends over the
years and I think that each has it's benefit in certain applications. But
there is no perfect one. So, is there any chance that one exists ? Maybe
the vehicle that we use in the future will look more like a bike or a car or
??? We don't know. I'd like to think that someone is thinking about these
things though...
--
L8tr...
Steve m...
web page: http://www.telerama.com/~stevem52
L.H. Club page: http://www.geocities.com/yosemite/7925
"Magnus Stĺlnacke" <jem...@telia.com> wrote in message
news:3C5A9011...@telia.com...
Doug Miller
> I'll try to answer since I live in Monroe, MI. Some of you will figure that
> one out.
I live in Boise Idaho. Some of you will figure that one out too.
Personally, I don't know what is in Monroe. Please forgive my
ignorance.
> It's all about caster and camber. In a trailing arm suspension, or an EQUAL
> length A-arm suspension (aka the simple parallelogram), the camber angle of
> the ski spindle (or wheel) changes with body roll that occurs during
> cornering. This effectively moves the center of contact of the ski (or
> wheel) toward the inside of the turn, reducing surface contact and loading
> the edge of the tire or ski. This in turn causes the ski or wheel to push,
> or understeer. Unequal length A-arm suspensions provide a camber
> correction, which maintains optimal ski (or wheel) contact forces along the
> centerline under all conditions.
The above is a GREAT explanation, IMHO. There are a gazillion ways to
explain it all, and that one sure works for me!
> With any A-arm suspension, the caster angle (or rake) will constantly change
> as the trailing arm and spindle centerline move through an arc. This causes
Hmmm. here I depart. Trailing arm length determines the minimum caster
change on a trailing arm suspension. But is more caster as the
suspension collapses a bad thing? More caster has almost no bad
qualities. It provides camber gain for the outside in a corner, and
camber loss(more positive camber) for the inside, both good things.
> that adverse caster will cause horrible and uncontrollable front steering
> oscillation (the reason that many large trucks use massive steering
> stabilizers). Caster is important for steering stability, on-center feel,
> and steering effort.
Cool thing about snowmobiles is you can make simple changes to the
skis to correct some of this.
> With any A-arm setup (equal or unequal), the caster
> angle is relatively constant throughout the limits of suspension travel and
> the designer is better able to optimize caster, in turn optimizing effort,
> feel, and stability.
Here's an interesting thought. Can you design caster gain into an
a-arm suspension? Make the inner a-arm chassis mounting points
nonparallel, and have the upper outer a-arm tie in point further back
then lower outer? Is this what Cat did on new buggy? I haven't looked
that close, just curious.
> Both caster and camber changes are aggravated in a long travel trailing arm
> suspension,
For a snowmobile, I believe you can control the camber entirely with
the control rods. Caster you have an argument, but I'm still not
convinced caster gain is a bad thing. I don't know though. great
thought.....
> and become more critical on vehicles that carry a higher
> front/rear weight bias.
I don't get the above, but I could believe that FWD cars might have
torque steer issues.....
> become significant. The move to unequal-A clearly signals the beginning of
> a new era of ultra-long travel front suspensions, especially in front heavy
> four-stroke sleds, IMHO. It was no accident that Yammie threw out the
> trailing arms for the RX-1.
I still come back to the fact that the longest possible a-arm
suspension you can design on a snowmobile is what is currently called
"trailing arm".
Btw, the old pickup and the Nascar boys use a trailing arm suspension,
but they also have solid axles and get something called Roll steer out
of it.
-doug miller
Doug Miller
back and forth.
One thing I've kinda wondered though - Offroad long travel buggies
have the RC up high so they can use less sway bar and get less body
roll. But, on a snowmobile, having one ski up in the air is a real
possibility. So should the RC be somewhat lower so that the transition
is more gradual? Once the inside ski comes up into the air, the RC
become the base of the outside ski.
just thoughts....
-doug miller
> MacPherson type suffers also from a low RC. On a personal car
> it is ok with a low RC you compensate that with a pretty stiff
> swaybar. But in a terrain vehicle you dont want that, on a
> snowmobile you want left and right to move as freely as
> possible compared to each other without the body roll when
> cornering, that calls for a bit higher RC. The snowmobile
> also have the problem of the rear RC moving 38 cm from side
> to side of the track at groundlevel.
>
> I think we will see Polaris radius rods in different lengths
> and different angles, even defferent on different models in
> the future. Most things you can acheieve with A-arm you can
> do with the trailingarm type too.
>
> Magnus Stålnacke
Magnus Stålnacke
>
> Great points. I'd totally not remembered that the RC in teh rear moves
> back and forth.
> One thing I've kinda wondered though - Offroad long travel buggies
> have the RC up high so they can use less sway bar and get less body
> roll. But, on a snowmobile, having one ski up in the air is a real
> possibility. So should the RC be somewhat lower so that the transition
> is more gradual? Once the inside ski comes up into the air, the RC
> become the base of the outside ski.
>
The world of front ends is full of tradeoffs, you just cant have
it all. If you want a constant center/center distance between your
skiis when one ski hits a bump, you will get a bad camber angle when
cornering and the body rolls and vs. If you want a good camber when
cornering you will get a bad camber angle when the chassis is flat but
the ski hits a bump and vs.
If you want a design that not hunts and darts back and fourth trying
to follow every track, go for the old leafspring design.
For now i think that the cats have the best performing front end,
not neccesarily by design, it is just that they have given it some
attention. Maybee they have hired someone from the car industry who
knows what he is doing.
Look at something so simple as the Ackerman princip, this is the
simple princip that says that the inner wheel/ski makes a narrower
radius/circle and thus have to steer more, how many snowmobile
designs have adopted that over the years? This princip is way older
than the automobile!
You just have to get the little steering arm on the spindle to point
at the rear center of the track when the ski is pointing straight
forward. I have done this mod on my old Polaris 500, had to shorten
the steering rods about one inch, and this shortening reduces the
bumpsteer too.
If i look at my outer ski at full turn it looks as it will have a
turning radius of a big bus, and the inner ski looks as if it wants
to go 90 degree. But if i stop looking and just drive, it is much
better, the turning radius is about the same. On ice it turns much
better when one ski dosent push/skid. In loose snow it runs easier,
not as easy to get stuck when one ski no longer plows throu the snow
when i make a sharp turn in low speed.
You can maybee help me here, there is an english word i just cant
find in my head or elsewere.
If you look at an old leafspring snowmobile and think a line throu
the spindle shaft down to the ground, mark the point that this line
hits the ground and then think a vertikal line down to the ground
from the bolt that holds the ski. The distance between these two
points, what is it called in English?
This is the main reason to why those old sleds dosent hunts back
and fourth seeking every little track on the hardpack snow, not
only the low ski pressure as many folks belive.
Magnus Stålnacke
http://w1.970.telia.com/~u97007522/
Bud Flagstad
>From: "Andy Dragon" andy_drag...@hotmail.com
>Date: 1/31/2002 8:23 PM Central Standard Time
>Message-id: <a3cveo$175ut3$1...@ID-105861.news.dfncis.de>
Bud Flagstad
MN
2003 Yamaha RX-1 Blue Snowcheck 1-26-02
2000 Kawasaki ZRX 1100
2000 Yamaha 700SXR
1997 Yamaha 700SX Big-Bore
1996 Honda Magna Deluxe
1996 Honda XR600R
1989 Yamaha Phazer
1969 Road Runner(Runs high 10s)
Magnus Stålnacke
If someone wants to try it, dont overdo it as the
steering rods will hit the springs at full turn then.
Snowjacks
"caster angle" is the angle between the spindle centerline and the vertical
pivot line.
"Magnus Stålnacke" <jem...@telia.com> wrote in message
news:3C5B45F7...@telia.com...
Magnus Stålnacke
>
> Magnus, I believe the term you are looking for is "caster trail", and
> "caster angle" is the angle between the spindle centerline and the vertical
> pivot line.
Caster trail "sounds" to be the right term for the distance
i am talking about, this distance can be accomplished by the
canster angle, but you can have the hole for the bolt that holds
the ski somewhat offcenter to accomplish this distance too.
The "caster trail" will also be affected from caster AND the
distance from the skibolt to the ski base. A car will get a
greater "caster trail" if you mount bigger diam wheels, and thus
need less caster.
This "caster trail" is one more thing i think that the snowmobile
industry has neglected over the years. But i am sure that we will
see much better front ends from all the manufacturers, and that we
can thank Arctic for, they have set the focus on this just by beeing
a little better in this respect.
Magnus Stålnacke
Bullwinkle Moose
Magnus Stålnacke <jem...@telia.com> wrote
> You can maybee help me here, there is an english word i just cant
> find in my head or elsewere.
> If you look at an old leafspring snowmobile and think a line throu
> the spindle shaft down to the ground, mark the point that this line
> hits the ground and then think a vertikal line down to the ground
> from the bolt that holds the ski. The distance between these two
> points, what is it called in English?
I think it is called "trail", from my dirt bike days. But it's been a long
time since I gave any of this any serious thought. Very interesting
discussion guys.
-Don
David Courtney
I may just misunderstand.
First, you made a distinction between equal and unequal length A-arms;
but not between equal and unequal length radius rods on a trailing arm
suspension. Unequal length radius rods can give exactly the same camber
gain as unequal length a-arms, as far as I can tell... and have been used
for years on the CRC front end.
Second, I can understand how small changes in "caster angle" can make a
big difference in a truck with 36" tall tires... because the actual "caster
distance" (the distance on the ground between where the tire contacts the
road and a line drawn through the ball joints down to the ground) can get
very large or very small as the caster angle changes... because the spindle
is 18" above the ground.
But, on a snowmobile... the "caster distance" is nearly constant no
matter how much you change the caster angle, because the spindle is so close
to the ground. Also, you can make the "caster effect" as great or small as
you want by relocating the ski forward or back on the spindle... which you
can't do on a wheel because it has to be able to go around (the spindle has
to be located in the center of the wheel, but not the center of the ski).
The problem that we had with the "caster gain" wasn't the amount of
"caster effect" on the steering... it was the fact that with the skis
turned, that extra caster really becomes extra camber. In other words, when
you turn the skis in a hard corner... the amount that the spindle is laid
back adds "camber" to the outside ski, making it more aggressive.
The harder you turn, the more the sled leans... and the more aggressive
the carbides get because compressing the suspension adds even more castor as
the angle of the trailing arm decreases.
Anyway, what we found happening was that carbides would start to
"chatter" because they would get so aggressive that they would just tear out
the ice... and then they would "hop" a little ways and bite in again. That
aggressive carbide angle and the "impact" from the chattering would actually
fold the trailing arm up just behind the radius rods... putting a big "bow"
in it and making it impossible to steer or drive.
Just my thoughts,
David
"Snowjacks" <snow...@provide.net> wrote in message
news:VSm68.146098$%b.93...@bin4.nnrp.aus1.giganews.com...
Brian
>I'll try to answer since I live in Monroe, MI. Some of you will figure that
>one out.
---------------------
Since nobody hit on this...
Monroe, MI is the home of Monroe shock absorbers
Brian 2001 XC600SP & 2001 XC120 for the kid
http://www.SnowEtc.com *updated 11-03-01
http://www.SnowmobileGarageSale.com (free buy-sell-swap board)
1965 Evinrude Skeeter for sale
1969 Sno-Prince for sale
http://www.LearnEtc.com
David Courtney
the Edge CRC trailing arm front suspension design patented, having filed it
in October of 1999?
Go to: http://patft.uspto.gov/netahtml/search-bool.html and look up
patent # 6,328,124 if you want to read about it.
The main claim in the patent application seems to be: "This unique
positioning of the radius rods arm has been found to reduce lateral scrub of
the skis as they move upwardly and downwardly through their respective
ranges of motion." or "The improvements of the present invention allow the
ski to move through the same arc length with substantially less lateral
scrub, which therefore provides better handling and less loading on the
suspension components."
David
David Courtney
look up patent # 6,009,966 (also Polaris)... it has an interesting
discussion of how caster angle affects handling and describes their patented
method of allowing the operator to adjust the caster (by raising or lowering
the rear mounting point of the trailing arm on an adjustable link) for
different situations such as oval racing.
I believe that would have helped us a lot, if it had been available.
David
"Doug Miller" <dmi...@foresightpartners.com> wrote in message
news:32b6c9cc.02020...@posting.google.com...
Rob Pilgrim
Don't you worry, my comments are on the way! I'm copy+paste'ing all
of this thread into a Word document so I can read it all and make a
post.
Magnus, Doug and Courtney pretty much have it on the head though.
-Rob
rbt...@erie.net (RBTool) wrote in message news:<d672ea30.02013...@posting.google.com>...
> robpi...@adboivin.com (Rob Pilgrim) wrote in message news:<f69299b8.02013...@posting.google.com>...
> > I'm willing to bet very few can answer you correctly.
> >
>
> So Rob, what are you waiting for?? let us know!!!!!!!
> Everbody listens to your comments!! Atleast I always do!!
>
> Randy
> RBTool
Bob Sullivan
http://www.rqriley.com/suspensn.html
Bob
"Rob Pilgrim" <robpi...@adboivin.com> wrote in message
news:f69299b8.02020...@posting.google.com...
CrnySKIDOO
>Date: 2/1/02 6:37 AM Pacific Standard Time
>Message-id: <fPx68.502$gH5....@newscontent-01.sprint.ca>
><<<<<<<snip>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
>If trailing arms can be as good as A-Arms, I welcome the day where I can
>witness it for myself when playing 'trade a sled' with my buddies. So far,
>there hasn't been a single trailing arm sled to date that I've ridden that
>has matched AC's front end. And that's since I started riding way back in
>'67. I've ridden just about everything out there, and would welcome equally
>good handling choices from other brands. But to date, this has not yet
>happened.
>
...... Forgive me for questioning, but I,ve seen it mentioned a couple times
on this post now insinuating Cat has had A Arm front end from day one.
#1 Cat went to A Arms in 1984 or 85 I believe, when they came back, and on
top of that, Polaris ruled in the handling department for quite a while after
that, before Cat eventually developed/evolved their A arm setup to the point of
bumping Polaris off their best handling perch that they held since about what,
1979?
Even then, the biggest benefits to A arms over the Poo's trailing arms are
under race conditions, and the difference in capabilities would most
certainly(currently) still be arguable.
The biggest benefit to A Arms is in the snocross arena where they aren't as
susceptible to damage, and the fact that as we continue down the road to longer
travel , the A arm starts showing it's strengths.
Also, I don't believe Cats patent, on A arms, if it exists , is what kept
everone else from using it. And if the patent was for 20 years, then it is yet
to run out, and we already have Yammy and Ski-doo using it.
A style front ends were around before Cat, just not on a production sled, as
mentioned, cars have been using it for a bit.
Another poster mentioned Ski-doo used A arms on the original independent
Safari's albeit, a heavy and awkward rendition of it.
When Polaris brought to production the Trailing arm design, (they too weren't
the first) Ski-doo and eventually Yammy saw it as the cheapest, lightest way
to get a good handling light independant susp. as the trade off for an A style
front at the time was a heavier sled due to the extra strength and beefing up
of the front end of the a style design.
Congrats to Cat for putting the developement time into it where they
eventually got it down to comparable weight, and according to the magazines,
benchmark handling. Just as they were behind the 8 ball with power, while Doo
had the Rotary Valve intake Rotax motors, Cat (Suzuki) and the others did the
work and developement on reed valves, until they took the edge away from Doo.
They all take their turn at bringing new good stuff to sleds, and we all
benefit from the competition. :-)
Kevin.......
X6667
between the two is... A-arm styles, by design, arc in one directional plane
where as trailing arms arc in two. As a trailing arm moves through its travel
it forces/accelerates the spindle forward/backward along with the side to side
manipulation created by the radius rods. Backward acceleration would be no
biggy and one might argue the A-arms are 'effectively' also guilty of this.
But, in no way will an A-arm 'lengthen' your overall 'effective wheel base'
like a trailing arm under load. Trailing arms force your ski forward under its
hardest load and bite conditions which creates potential upsetting
characteristics. Grossly simplified, A-arms have 2 pivot points and trailing
arms have 3. Thats my lamen take in a nutshell.
Heres more facts as I see. Could it be that an ideal setup or more real
worldly, an effective setup, based on sled and rider as one is equally
important. As is the relationship between the front and rear suspension. My
point is, that in no way will there ever be ONE suspension style that works
best for everything and everybody all the time which is perfectly ok right.
Trend says we want A-arms and were getting them.
X6667
Robert Veronneau
remember well
That was before my '82 Blizard 5500 MX
Robert
Coaticook
"CrnySKIDOO" <crnys...@aol.com> a écrit dans le message news:
20020203213018...@mb-fa.aol.com...
David Courtney
It might have been sort of a crude single A-arm deal... but I remember
it looked like it had trailing arms in the ads at the time. They looked
similar to a Polaris trailing arm... with the steering tube welded rigidly
onto a long arm that anchored back near the footwell.
I never gave it much thought... but I had the impression it had trailing
arms.
David
"Robert Veronneau" <bob...@hotmail.com> wrote in message
news:91w78.10885$oa.7...@weber.videotron.net...
Robert Veronneau
I'l try to find a pic
Robert
"David Courtney" <adv...@internetwis.com> a écrit dans le message news:
a3mjiu$19crja$1...@ID-70857.news.dfncis.de...
David Courtney
I guess it is sort of a single A-arm... but it looks (or looked) like a
trailing arm in the magazine ad pictures. Looking at the parts diagram... I
can see why it wasn't a great handling machine, although it looks like it
would gain some camber as it leaned in a corner. >;-}
David
"Robert Veronneau" <bob...@hotmail.com> wrote in message
news:XKB78.12568$oa.9...@weber.videotron.net...
CrnySKIDOO
>Date: 2/4/02 5:29 AM Pacific Standard Time
>Message-id: <91w78.10885$oa.7...@weber.videotron.net>
>
>First Cat A-arm front suspension was in '80 or '81 on a trail-cat if i
>remember well
>
>That was before my '82 Blizard 5500 MX
>
>Robert
>Coaticook
>
>
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Ski-doo Blizzard 5500 MX's first year was 1980. ( Although the 82 looked
nicer)
Kevin.......
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
A. Nonni Moose
A arm suspension, the AFS (A Frame Suspension). After Cat came back from the
brink in the early 80's, its first attempt at an independent front
suspension consisted of a lower wishbone oriented approximately in the
horizontal while the upper wishbone was rotated to the vertical and the
inboard end attached directly to the shock. The Ski Doo copied this design,
albeit simplified, on the Safari.
A.M.
"CrnySKIDOO" wrote in message