Clutching theory
- Thread starter devilrmk
- Start date
4
440dart
Well-known member
as for this thread for the dummies like me maybe somebody can make a list of some sort exsplaining what each thing does and how it affects the sled and maybe make it a sticky. for the longest time i had guys tell me this and to run that but i had no idea why i couldnt find anybody to take the time to go through the secondary numbers with me. if somebody makes list as a sticky list some common problems that guys ask on here. example sled go's to 8000 rpm but on a long hill power slowly falls off to around 7800 you need to do this, this and this ect. not the best with words maybe iam confuseing some. but this would save alot of clutching questions on snowest. make it a sticky in every section,xp,m-series,iq,iqr ect ect
It is a sticky, and it does try and explain what each thing does. You just have to read it from the beginning.
Very valid point though, and good reasoning for cleaning this thread up.
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440dart
Well-known member
i think .46 to .36 is a valuble question, i was just useing my sled as an example. i still think somebody should gather this imformation put on one page instead of scattered thru 3 or 4 pages once this "theory" page is ending
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440dart
Well-known member
It is a sticky, and it does try and explain what each thing does. You just have to read it from the beginning.
Very valid point though, and good reasoning for cleaning this thread up.
haha i know i read through it some people i tried to understand just not that smart
keep checking every other minute to see if somebody posted anything thing new starting to like this clutching stuff
Agreed, it is a valuable question, sorry, I wasn't trying to single you out, just noticed the thread direction has changed since the beginning. Again, not trying to single you out, timing is all. I happened to be looking through it and you were the last person that posted.
Not trying to be a dick, but I come off like that sometimes..
Its hard to stick with theoy with out using examples,
So when it comes to the secondary things get alittle harder due to the fact
from brand to brand they vary in how they work, the winding of the spring vs some of the new ones that just use compression.
I found the link spiderman posted that showed the lb of force on the belt from the secondary with diff springs and helix's very odd. it did not go up in lb of force with the flatter angles like I thought it would. So here is the question, I understand you can have to much grip "force" in the secondary but what do you do when you are not getting GOOD back shift. ??? just dropping cam weight makes sence but at the same time that will effect the speed of your shift, even taking weight from the tip of the cam will help but not enough, So whats the theory on "tuning" a perfect shift someone must has a bit of a step by step tuning the clutches. Myself Ive always enjoyed and have had good luck with clutching many machines until this one right now has me guessing. Im under the belief the CVT it the perfect clutch but when your having a hard time getting close to perfect,,,,,,,,, I will watch for someone to post some knowledgeable tuning help. IMO clutching for drags is easy, clutching for top speed is not trying to get the best of both worlds is even harder.
So when it comes to the secondary things get alittle harder due to the fact
from brand to brand they vary in how they work, the winding of the spring vs some of the new ones that just use compression.
I found the link spiderman posted that showed the lb of force on the belt from the secondary with diff springs and helix's very odd. it did not go up in lb of force with the flatter angles like I thought it would. So here is the question, I understand you can have to much grip "force" in the secondary but what do you do when you are not getting GOOD back shift. ??? just dropping cam weight makes sence but at the same time that will effect the speed of your shift, even taking weight from the tip of the cam will help but not enough, So whats the theory on "tuning" a perfect shift someone must has a bit of a step by step tuning the clutches. Myself Ive always enjoyed and have had good luck with clutching many machines until this one right now has me guessing. Im under the belief the CVT it the perfect clutch but when your having a hard time getting close to perfect,,,,,,,,, I will watch for someone to post some knowledgeable tuning help. IMO clutching for drags is easy, clutching for top speed is not trying to get the best of both worlds is even harder.
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How much spring force on the start and finish of the secondary spring does 1 delrin washer add? Does that number double and triple when you add 2 or 3 delrin washers respectively? I assume its minimal, but might change some when you have 2 or 3 in there?
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The best way to get a fundamental understanding of clutching is to read Olav Aaens Clutch Tuning Handbook. Then read it again, then read it again.
One of the most basic things to understand about clutching is the primary is rpm sensing whereas the secondary is torque sensing.
Generally speaking the primary will shift based on rpm where the secondary will shift based on load at the track.
On the Derlin washers adding washers will add preload because you are compressing the spring but the finish rate wont change.
Thunder 101 on the backshift focus on the secondary not the primary. The idea is balance between the spring rate and helix angle. Too much side force it wont upshift, too little it wont back shift. As far as the "perfect shift" it doesnt exist because conditions and variables are not constant. The best we can hope for is a combo that works well in a range of conditions that match your riding style
Dart on the .36 shifting faster then the .46; All this means is that the secondary will be in the first angle a 10th of an inch less. It will shift into the second angle a 10th of an inch sooner. Its likely that it would slow the upshift to a marginal degree, but thats not necessarily a bad thing. You are trying to match the side pressure requirements of the belt for upshift and bachshift. You will probably not even notice the difference on the upshift but by doing this change it will probably help in loaded/deep snow conditions. Specifically when you let off the gas and get right back into it you will be in the shallower angle of the helix sooner or the 10th of an inch difference may be enough to keep it out of the steeper angle all together (in this example.)
I know this isnt the best explanation, but I hope it makes sense
One of the most basic things to understand about clutching is the primary is rpm sensing whereas the secondary is torque sensing.
Generally speaking the primary will shift based on rpm where the secondary will shift based on load at the track.
On the Derlin washers adding washers will add preload because you are compressing the spring but the finish rate wont change.
Thunder 101 on the backshift focus on the secondary not the primary. The idea is balance between the spring rate and helix angle. Too much side force it wont upshift, too little it wont back shift. As far as the "perfect shift" it doesnt exist because conditions and variables are not constant. The best we can hope for is a combo that works well in a range of conditions that match your riding style
Dart on the .36 shifting faster then the .46; All this means is that the secondary will be in the first angle a 10th of an inch less. It will shift into the second angle a 10th of an inch sooner. Its likely that it would slow the upshift to a marginal degree, but thats not necessarily a bad thing. You are trying to match the side pressure requirements of the belt for upshift and bachshift. You will probably not even notice the difference on the upshift but by doing this change it will probably help in loaded/deep snow conditions. Specifically when you let off the gas and get right back into it you will be in the shallower angle of the helix sooner or the 10th of an inch difference may be enough to keep it out of the steeper angle all together (in this example.)
I know this isnt the best explanation, but I hope it makes sense
S
shortstop20
Well-known member
Good points by Rocky.Mtn.Kris.
IMO, and many others(but not all), you should tune the RPM with the primary and the shift with the secondary, as a rule of thumb, not an absolute. There are always exceptions.
The depth of the delrin washers is so small I would be very surprised if it makes any noticeable difference on spring rate. I bet the manufacturing tolerances aren't even within the depth of 3 delrin washers.
Its hard to stick with theoy with out using examples,
So when it comes to the secondary things get alittle harder due to the fact
from brand to brand they vary in how they work, the winding of the spring vs some of the new ones that just use compression.
I found the link spiderman posted that showed the lb of force on the belt from the secondary with diff springs and helix's very odd. it did not go up in lb of force with the flatter angles like I thought it would. So here is the question, I understand you can have to much grip "force" in the secondary but what do you do when you are not getting GOOD back shift. ??? just dropping cam weight makes sence but at the same time that will effect the speed of your shift, even taking weight from the tip of the cam will help but not enough, So whats the theory on "tuning" a perfect shift someone must has a bit of a step by step tuning the clutches. Myself Ive always enjoyed and have had good luck with clutching many machines until this one right now has me guessing. Im under the belief the CVT it the perfect clutch but when your having a hard time getting close to perfect,,,,,,,,, I will watch for someone to post some knowledgeable tuning help. IMO clutching for drags is easy, clutching for top speed is not trying to get the best of both worlds is even harder.
IMO, and many others(but not all), you should tune the RPM with the primary and the shift with the secondary, as a rule of thumb, not an absolute. There are always exceptions.
The depth of the delrin washers is so small I would be very surprised if it makes any noticeable difference on spring rate. I bet the manufacturing tolerances aren't even within the depth of 3 delrin washers.
Whats the theory on the sec spring, for back shift do you want a medium spring and "crank" it up tight or a stiff spring. I always worry that a stiff spring will have to much belt queeze towards shift out ? traditional cat secondary
Once over 100mph things start getting harder.
Im trying to get dialed in, its fast in 660, 1000 and in 2000' it starts to hit a wall unless thats all Im going to do,,,,, but I want to ride it as a regular ride and Im struggling trying to get a back shift.
Once over 100mph things start getting harder.
Im trying to get dialed in, its fast in 660, 1000 and in 2000' it starts to hit a wall unless thats all Im going to do,,,,, but I want to ride it as a regular ride and Im struggling trying to get a back shift.
O
onlyridesrmks
New member
clutching
Can someone explain to me why on a drive clutch spring, the manufacturer will say for higher peak RPM, increase the 1.25 compression rate, to lower peak rpm, decrease it. So if you increase it, then it's stiffer right? then won't it take more weight to overcome that heavy spring at the same rpm for full shift out? or more rpm with the same weight? well if i'm running 8100 and I need to get to 8300 won't a stiffer spring just keep the primary from full shift out? if I needed to get to 8300 and the belt is still 1/2 inch from the top of the primary then won't a spring with a little lower 1.25 compression rate allow the weights to swing all the way out?
Can someone explain to me why on a drive clutch spring, the manufacturer will say for higher peak RPM, increase the 1.25 compression rate, to lower peak rpm, decrease it. So if you increase it, then it's stiffer right? then won't it take more weight to overcome that heavy spring at the same rpm for full shift out? or more rpm with the same weight? well if i'm running 8100 and I need to get to 8300 won't a stiffer spring just keep the primary from full shift out? if I needed to get to 8300 and the belt is still 1/2 inch from the top of the primary then won't a spring with a little lower 1.25 compression rate allow the weights to swing all the way out?
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clutching related to track speed
Some basic questions...
Let's say there are two sleds that are identical except for clutching changes and one can get to 42mph and the other only to 36mph. Both hitting the same peak RPM. The first thought is that the one at 36mph is not shifing out all the way, correct? Is it possible that both of them ARE shifting out the same amount, but the one at 36mph is just slipping the belt that much more?
Are there any other factors I am not considering?
Why don't more people focus on track speed? Out of 100 posts I read on clutch setups, maybe 5 talk about track speed. Wouldn't high track speed be your number one goal and then maybe back shifting. I guess I am assuming everyone on this site rides in powder.
Some basic questions...
Let's say there are two sleds that are identical except for clutching changes and one can get to 42mph and the other only to 36mph. Both hitting the same peak RPM. The first thought is that the one at 36mph is not shifing out all the way, correct? Is it possible that both of them ARE shifting out the same amount, but the one at 36mph is just slipping the belt that much more?
Are there any other factors I am not considering?
Why don't more people focus on track speed? Out of 100 posts I read on clutch setups, maybe 5 talk about track speed. Wouldn't high track speed be your number one goal and then maybe back shifting. I guess I am assuming everyone on this site rides in powder.
Joe, I would say yes to both of your first questions.
I think the most efficient clutches = the most track speed. I think most of us try to optimize our clutching to get the effieciency which in turn creates that high track speed.
If your belt and clutches stay cool you have efficient clutching
I think the most efficient clutches = the most track speed. I think most of us try to optimize our clutching to get the effieciency which in turn creates that high track speed.
If your belt and clutches stay cool you have efficient clutching
Clutch alignment question. I've figured out that my jackshaft flexes enough for the secondary to move about .250" forward under full load. What's the theory on how to line up the clutches while planning for that kind of deflection? Standard 1" jackshaft with a .200" spacer between the bearing and the clutch.
I have never heard of a jackshaft flexing....at least not a measurable amount, yet 1/4"!! That's huge and something is seriously wrong if that's the case. Everything related to the jackshaft should be solid.
The engine does move alot though.
I do alignment the same on any sled with any combination of clutches. The belt should just kiss the inner sheave on the primary with all belt-sheave clearance to the outer sheave and no visible "dogleg" in the belt. C-C set for belt length and belt just above the secondary sheaves.
I think you are right about the motor moving. I got 7 motor mounts so I wasn't expecting it to move quite that much. My jackshaft is supported by dual bearings on the clutch end. The actual motion is the Primary moves about .250" back and towards the chassis about .150"
You are talking at rest right? So you are saying with the belt starting against the inner sheave where it bends around the primary, it's just touching the surface as it passes the face?
Would this give me the best alignment at full shift out? My clutches run cool until they shift out. All the heat seems to be generated by the secondary. I initially let the secondary float to find the alignment point(not under full load). Then under normal riding it was hot. Put in a .100" shim and it was noticeably cooler.
