Why does lower total force primary spring allow more top end

[Frostbite]

Ok, send me to school. It sounds like I have been going about this all wrong. I tend to go with the highest total force primary spring I can find using the theory that the higher total force allows me to throw heavier clutch weights in the primary. I was always taught, throw weight at the primary until the motor can't take it any more. When I reach this point I will typically add a shim or two under the primary spring and I'm right where I need to be.
First off I ride mountain sleds. In this case an RX-1 Mountain and previously a 141" Muntain SRX. Where I live I ride a lot of wide groomed trails that go down along wide sweeping rivers in the mountains and we go like hell. There are airstrips in the mountains we tend to migrate to, to see whos "mountain sled" is the fastest. Then we'll turn around head up the mountains and climb and boondock in the deep powder the remained of the day and then it's a race back to the trucks.
No wonder I'm confused. Trying to clutch best for all these different aspects of sledding can be more than a little complicated. I see many people use the G/G/G or the G/Y/G primary springs because they say "They give you better top end speed". I tend to go with the O/S/O and P/G/P or maybe a P/S/P spring. Am I blowing holes in my own feet? Should I be focusing on lower total force springs? Send me to school. Powder Blue

 

[black john]

springs

yes i thout this to untill i tryed to clucth this thing and found that it likes to rev for a stock set up i would try o/s/o in the primary and a silver secondary that should work not to bad for top speed note that the scondary spring in the stock rx 1 binds and does not let it open . hope this helps

 

[LazyBastard]

Your weight and spring cancel each other out. Your top speed is found by achieving a balance between them. You can use the secondary settings to raise or lower the balance in order to achieve more or less belt squeeze (ie tighter secondary allows lighter spring or heavier weight which will cause increased belt squeeze and lower belt slippage).

If you're changing your spring to very soft, then you can lighten up on the weights and achieve the same squeeze.

 

[black john]

hay there lb dont knok what works . i did 119.3 on radar with my set on my black rx 1 .[fast color] :wink:

 

[LazyBastard]

who's knocking what?

 

[Frostbite]

LB, I do understand it's all about balance. When you've been doing this as long we have you can feel when all is right with the universe but, I'm balancing my secondary to a O/S/O and using heavy clutch weights to do it.
Is there an advantage to be had by going to a lighter total force spring , lighter weights and less wind on the secondary? I know that with less wind on the secondary the sled will shift up faster but remember in the mountains especially I need a good backshift.
I have some heavy hitters to try for next season too. The 8DN-00 weigths I am running now weight in at 56 grams. The "prefered" setup for the Heavy Hitters weigh in around 64 grams. It will be interesting to see how that extra weight relates to the rest of my setup. Powder Blue

 

[Buckeye]

Weights

The profiles of the weights have alot todo with how they will interact with the springs and helix. I would guess you will want to be down around 62 grams if you plan to run the o-s-o spring. Ofcourse, it will all depend on the helix and altitude you will be running at.

 

[1xr]

Powder Blue, You have tried the 8bu-00. To my understanding of what yuo want is a fast reving ramp for mountian use,I have never sleded in the way you do. I'm a flat lander with a 136 track. I use 89a not 89a-10 they are just old ramps that would'nt work in anyhing else. With nothing to lose I welded 4.5 grams to the under side at the begining put 4.5 gram pin and ground .5 of and ground .5 from the tip, making them weigh 56 grams. Profile of ramp is'nt as steep as 8bu-00, but works good I left the factory primary spring and chaged secondary to silver and stock cam.this set up I only got to try a few trips out at the end of year. It is night and day to the 73 gram straight edge ramp. Has anyone tried to machine a more agressive profile on the giant flat slugs?

 

[BlueByYou2000]

A wise man once told me to clutch your sled starting with your primary. The theory is to essentialy throw as much weight as you can without pulling down top shift RPM. As you know, every spring has different characteristics with regards to force. So a spring change warrants a change in weights (in alot of cases). Ideally you want your primary to spool up as quickly as possible. There are many different ways to accomplish this. As LB points out, you need your spring and weights to work in harmony to acceive a good balance. I can not comment on an exact spring for mountain applications as I am a flat lander, however the argument doesnt change regardless of surface. I prefer throwing weight at my primary, others do it working with there secondary. You may want to check out the Purple spring from Maxx Perf in conjunction with Heavy Hitters. Flatlanders with SRX's know all about that spring. Good Luck to you and I wish I could be of more help on a tested setup for MTN. RX-1's...BBY

 

[POWERHAULIC]

I thought has crossed my mind of grinding a real profile on the stock ramp. Lack of extra time has prevented this senerio from taking place. :lol:

 

[Frostbite]

I just knew you guys would have some valuable insight into this question. I think the bottom line is: I have found the "balance" you speak of between my primary and secondary. I believe this balance can be found using light, heavy, aggressive or less than agressive clutch weights. I just chose to use the heavier components (to load the motor) in my clutching "Recipe".
I have found the Yamaha silver secondary spring at 80 degrees and a Dalton 54/42 progressive helix to work the best in my secondary.
What is the spring rate of the Maxx. performance "Purple" primary spring? I could use a 150 total force spring I guess (if the engagement isn't TOO high). In the powder a high engagement can have you digging out repeatedly.
You know what's funny? In my modded MSRX I found the best setup was an O/S/O or P/G/P with the same 8DN-00s (with less total weight) than I'm using in the RX-1M. In the secondary I was using a Kinetic custom cut 54/42 progressive helix with the silver Yamaha spring but at 50-60 degrees (in place of the 70-80 the Rx-1M seems to like).
Am I just trying to replicate what FEELS most familiar to me or is it REALLY the best set up? I will try to get a set of 89As and 8BU-00 for testing next season as well. Although, the 8BU-00 weights (with the bird beak tips) certainly don't look like a top end weight. The club like tips on the ends of the 8DN-00 weights are what originally drew me to the them after racing guys (while I had the Dalton weights installed) with the stock weights and seeing them go by me on top. I KNEW I needed more tip weight for a larger topend. I'd kill them out of the hole with the Dalton's but they'd run me down everytime.
Dalton used the 8DN profile in building their weights. There are more aggressive profiles but traction constraints sometimes turns one away from going with them. For me and my mountain/trail application (and a 2" track) an 8BU profile with a tip like the 89A or the 8DN-00 would be the ticket. Powder Blue

 

[LazyBastard]

The notion of torque is actually misleading. The peak torque zone only amounts to peak acceleration under constant gear ratio. At optimal gear ratio, peak horsepower leads to peak acceleration. You can actually see this in the DEFINITION of horsepower... 1 horsepower is that which is needed to lift one pound 1 foot in one second. Lifting is a purely acceleratory procedure - 32 feet per second squared is acceleration due to gravity which you are counteracting with that horsepower.

Now torque... Thats in foot-pounds, or Newton-meters if you like metric. It is the instantaneous straight line force off an imaginary paddle mounted on a circularly moving shaft at a distance of 1 foot from the center. If you gear-reduce that shaft 2:1, then the instantaneous straight-line force is doubled, ie double the torque.

Back to horsepower... that is independant of RPM. To use a direct example, gear down that lifting mechanism and give it something that weighs 2 pounds, and it will lift it 1/2 foot.

If at 9000 rpm, the engine produces 100% of its torque, and at 10200 rpm, it produces 95%, then think of this; by the change in gear ratio to allow that engine up to 10200 rpm, you increase torque AT THE SECONDARY by 10% while you reduce torque AT THE PRIMARY by 5%. Thats a net gain of 5% torque at the secondary clutch.

It is the torque at the secondary clutch that matters. It can be directly converted into force being transmitted into the track. Force on track is directly proportional to acceleration (assuming perfect traction).

 

[snowbeast]

LB thats a little deep for most of us,i do understand thrque vr hp and my sled runs better top end at 10,500 most all the time,now thats just mine all sleds r not created equal,r they!

 

[LazyBastard]

What I just said is that torque at the primary clutch is totally irrelevant. What you want to do is set it up so that you have maximum HORSEPOWER at primary clutch, then the clutches (if properly set) will automatically give you the best possible torque where it counts.... at the track.

 

[Frostbite]

Ok, now we're getting some where. Not really where I intended to go but alas somewhere. LB I guess that's why I like 10,500 better too. The accelerometer in my butt says the sled is pulling harder and is happier there than at 10,200.
How come we haven't installed accelerometers on our sleds? I worked on Jet fighters and they all had them (to measure for stesses). The aircraft I work now have one and an FDR-CVR (flight data recorder) that measures acceleration in all phases of flight. We down load the data and study it for any potential over stress situations.
Yes, torque multiplication is our friend
No one has answered the original question yet. Why would going to a lower total force primary spring give me a higher top end? Powder blue