SLP (BDX) helix for mountains 44/36 (Radiused) or 44/36 (Progressive)

i am curious to know as well. i also just ordered and recieved a 42-38 bdx diamond drive helix from slp. how do you tell if it is a radius or progressive cut by their part numbers? the box just says 52-42/38 helix 07-09 cat diamond drive.

i am testing the theory, you can use the small spread 42-38 and give up a little, super high, and super low, and have a great mid elevation set up. and not have to switch the secondary when switching elevations.

ski

what is the difference, I though I had a 44/36 progressive, but I bought it straight from slp for my pipe setup.

the progressive is a very smooth transition and the other has a very shory first angle and then changes to the next and you can see where the angles change,

then I don't have a progressive

All I can tell you is the slp 44/36 helix on my ported 09 M8 works awesome.

I've posted this before, but here it is briefly. I tried the 46-36P on my M7 coupla years ago and didn't like it. It was just too much helix for climbing...wouldn't hold rev's with my spring (Goodwin blue/white, almost identical to AC orange, and gold up front with 75g.). To see what was going on, I traced helixes on paper. At hillclimbing speeds, the 46-36 was still in a steep angle. Helixes I liked had already shifted out to shallower angles. It will depend on your gearing, but you need some torque, or more secondary spring to pull that much helix angle while climbing. I would like to try the radiused...how long does it take to transition to the shallower angle, and where does that happen?

John

Frostbite said:

John, if I'm not mistaken, the duration of the initial 44 degree angle on the helix is very short lived. It's just to initally load the motor and then almost abruptly drops off to the 36 degree finish angle. The "abruptly" part is what I have found I don't like on a trails but, in when climbing mountains, it's probably a better option?

Where the progressive helixes have a nice transition from inital to finish angle the radiused or stepped happen much more quickly. Basically if your sled is moving around in the mountains, you are pretty much running on a straight 36degree angle helix.

I have to wonder if that is optimum? Easier to clutch yes, but optimum?

Click to expand...

That is correct the 44 is a very short duration but it is enought to give you one heck of a launch to get track speed up very quick. For the mountains I love my 44/36 radius cut. Also I have not noticed the switch from the 44 to 36 as being harsh on mine.

in mountain riding, there is almost always a "best" angle for a particular engine/gearing/snowcondition problem...the problem is that no one wants to change for every situation....i like to get my clutching set, and mostly forget about it....those who ride in both the plains and mountain on the same sled will have to have two set-ups....sooo, what i do is (mostly thru experience), come up with a helix that my sled climbs with the best for most of the winter, and accept the fact that during spring conditions, it will work, but may not be optimal....on my 09 1000 that is a 40 degree helix, on my 2010 m-8, find the 38 works well (although it's early yet, and i may switch to a 40)...as to dual cut or progressive helixs, i far prefer the dual cut, because i can control where on the helix i do my climbing....with a progressive, it is constantly moving across different loading, i.e. from 39 to 38 to 37 and back again, which causes the rest of the clutching and engine to have to compensate....so in a rapidly changing load situation, you have too many variables occuring, not to mention the throttle being a big variable also...i like dual helixs, with anywhere from 4-8 degrees more than the finish angle, i.e. a 44-40, or a 46-38, but an absolute key, is that the steep angle must be short, if you were to measure it, it would be about .350", or about 1/3 of an inch....to show how critical this is, if the initial cut has a .450" duration, it will make a significant detrimental change for mountain riding....so when i order my helixs from bd, i specify what i want....now what frostbite has deduced is correct....a dual helix, with the first angle being steep and short, to launch the sled hard, and a more shallow, long finish angle to climb with...the finish angle is most important because that is what loads the engine and makes it pull...in conjunction with the helix, you need enough back shift to let it run up the hill at a constant rpm, the stock orange spring is good for this.....the rpm to be set by the front spring/weight combination....i find that the stock orange driven spring in the cats, is a good backshift spring, and that by adding a shift assist, makes for a good driven set-up with the proper helix (steeper than the stock 36)....i do not recommend a gearing change for either the m-8 or the 1000...while m-8 gears on a 1000 will give a decent hole shot even with poor clutching, it is an inferior hill climbing solution, as compared to stock gearing with good clutching, as i have demonstrated to a couple of riding buddies many times....i then select a drive spring that engages at the rpm i want and has a shift out rate that is close to the stock....for my 1000, i use an engagement of 120 lbs, for a 3600 rpm engagement and a shift out of 310 lbs....then i adjust the rpm with weights, adjustables work ok, although i use stock weights which i then notch and finish to the final weight by testing and grinding, (i start with stock weights, and then usually use the next heavier ones so that i can modify them to my preference....i ride mostly7-11k.....finding the best clutching solution isn't easy, but if you work at it methodically, one step at at time, it's worth more than $2-3000 in engine/exhaust mods....but of course, you can do that also..

my helix from bdx (ordered from slp) just has the stamp on the side 42-38.

it doesnt have an R or P with the numbers at all. i am assuming a progressive cut would have the P, and the stepped cut would just be the numbers. but, that is just me thinking. can anyone elaborate? heading to togwotee thursday, going to take the straight 36 with me but i am hoping the 42-38 does a good job up there. ski

the 44/36 R I have made a huge difference in my clutch. I have managed to get amazing launches and apply a lot of force to the ground and with the stock 36 the extra grip would hold keep the drive bound until the drive clutch forced it open and it would then sling shot it to far and then backshift to quick and cause a bind and drop my rpms so far the drive clutch would over come it. the 44 lets it get moving and then vary with better optimal rpm. But I have done a lot changes this year. If you could find a straight angle that worked the best for climbing and then add the pre angle to the radius it should put it on the money. Would also like to try a triple cut, but start out with a 44 break it into a 40 with a radius cut and then go from 40/36 progressive.

It will be good to here the comparison. My dealer tells me my 44/36 wont work in cooke, I think he is going to learn something, or maybe I will.

to bad I wasn't still in the area we could just switch secondary's and see the diff.

ran the 42-38 at 8500-9500 feet yesterday, found it held back rpms too much on up shift. it backshifted slower and funny. it made the belt and sheeves hot, and seemed to have goofed up the belt deflection (be;t squeeling after pulls in the deep), even though i had already removed an adjuster shim to properly set the deflection on the bdx helix. the stock helix did need a deflector shim, the bdx did not but with it removed, it still seemed the bdx was too tight for deflection.

swaped the straight 36 from cat back in her, we'll see where she lands. running 68 gram cat arms, stock springs. i am low on rpms 76-7750 on trail, in the deep and pulls, 73-7400 max and it struggles to get there. need more primary spring total force.

does anyone know the colors and part numbers of the next stiffer total force spring from either cat or a/m supplier? hopefully i could order something or pick it up near jackson hole to fix the rpms while we are here. would rather running heavier weight and more spring, than drop weight from the arms.

any help appreciated, ski