Which gives slower upshift.

popcorn popper

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I have a xm with a 48/36 secondary helix. I find my rpm is fairly close but in some deep powder i have be on 3-4 on clickers. I like to stay down in lower numbers do you think a 50/33 would slow it down a smidge. Or should i go to like a 47-33?
 

+SLEDWRECKS+

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Steeper the angle = faster upshift / slower backshift
Shallower the angle = slower upshift / faster backshift
 

X-Treme3x

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I have a xm with a 48/36 secondary helix. I find my rpm is fairly close but in some deep powder i have be on 3-4 on clickers. I like to stay down in lower numbers do you think a 50/33 would slow it down a smidge. Or should i go to like a 47-33?

48 start is rather aggressive if you are running a mountain sled and may not backshift well which is why you drop. You can try a slightly less finish to take some load off you may have to drop pin weight. I would try a purple/purple secondary spring first, before getting a new helix.

higher the start number to quicker the upshift and vice versa.... 47 will upshift slower than the 48 or the 50.
 

Dynamo^Joe

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If you can't measure it, you can't see it.
If you can't measure it, you can't manage it.

Take your helix and break it down into its component angles.
Example; a 50/40 has 11 angles. 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40.
Take your gearing and known full shift overdrive speed and divide that speed by 11 angles.
Say your gearing is for 80mph full shift overdrive
80mph / 11 angles = estimated 7.27mph per helix angle.

You said "have to be on clicker #3~4.
Ok then IF in clicker #4, THEN what track speed is this happening at where you want quicker backshift?
Lets say 40mph the backshift is slow and you need to be in clicker #4 to have decent backshift, but you want clicker #3 to produce the same backshift strength in clicker #4.

  • What track speed are you having a problem at? What helix angle is being used at that track speed?

Question; What angle is being used at 40mph track speed in clicker #4? [with this 50/40 helix]
Answer; 50(7.27) 49(14.54), 48(21.81), 47(29.08), 46(36.35), 45(43.62)
Ok then, at 45 degrees, at that position on the helix, you need to have at least 1 degree lower angle "At that track speed".
45 degrees at that track speed, the upshift is too fast, the backshift too slow = need clicker #4.
Then lower the helix angle at 43.62 track speed.

Question; what helix angle(s) will you use now to get 44 or 43 degrees at 43.62mph? You have to figure that out now.

If you can't measure it, you can't see it.

More information
 
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Dynamo^Joe

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the difference between a politician (political) answer and me answering with a question is; the politician speaks their answer with a question to avoid answering an uncomfortable question. "When the going gets tough.....QUIT"
vs....
I answer w/a question showing error in playing musical chairs with helix angles. "When the going gets tough....work harder" Dont be a parts changer, rather, solve the problem.

What is the difference of changing helix angles where you dont know what angle is giving you a problem with - compared to shooting a dart at a dartboard with a blindfold on, after i spin you around 3~4 times?

Boils down to me saying
Dont ask people what helix angles you need to use, rather learn to "Ask the helix" what angles you need to use.

What angle are you using at X track speed yer having a problem at?
Now that you know the angle, then...
Apply the theory of what +sledwrecks+ says
...to come up with a new angle that reduces or eliminates the problem at-that-track-speed.
Apply the theory of what X-Treme3x says
...higher number vs lower number etc...

change the helix angle at the track speed yer having the problem at". :geek:
 
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1709

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Take the guess work out and go with a straight angel helix. like BRP brings out in their Mountain sleds.
 

dragonweld28

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I think the main issue is the helix. Its to much helix in the mid/top end. With a 48/36 you are almost never in the first or last number, so it acts like a 47/37. In deep snow you are trying to pull to much angle. Those full progressive helix's are also notorious for slow backshift. Ideally, you should run a 48/36.36. This shifts from 48 to 36 over .36 of your shift and leaving the 36 for the remainder of shift. This will hold rpm better and offer faster back shift. What secondary spring are you currently using?
 
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