Track speed gearing and clutching debate.

[mynewuseddoo]

go 8" across the clutch where you would get the 1:1, if you take 8" and multiply it by 3.14 you get 25.12". So if you stuck a 8" wheel and turned it one revolution it would travel 25.12" then multiply that by 8000 =200960" a min. divide it by 12 to convert to feet =16746.666666 divided by 5280' =3.171717 multiply by 60 to get from min. to hrs = 190.303mph. Then take a 1:1 of 80mph divide 190.303mph divided by 80mph = 2.378788 for a ratio. (the first time I did it I was off on the mile and had 5260' when I should have had 5280')

But this is a ratio if you have 8" drivers, if you factor in the height of the track then the height of the lug it can really change. this is a ratio if you only count the driver size. So if you take the 2.378788 gear up then the 2.24 gear down at 8000 rpm and 60/60 gears in a 1:1, then subtract the two and you get = .138788 then multiply it by 80 =11.10 and because its a gear up you add it to 80 to get 91.10mph 57/63 gears 82.42mph 55/65 = 77.08mph

I could be way off on this but its making sense to me.

So then if I am only able to pull 48 MPH it does make sense to gear down in order to bring my clutches closer to the target 1:1 ratio with the available power I have in my sled. As per the calculations, there is no way I can be at 1:1 at 48 MPH with 57/63 gears in my DD, correct?

 

[Jeff K]

go 8" across the clutch where you would get the 1:1, if you take 8" and multiply it by 3.14 you get 25.12". So if you stuck a 8" wheel and turned it one revolution it would travel 25.12" then multiply that by 8000 =200960" a min. divide it by 12 to convert to feet =16746.666666 divided by 5280' =3.171717 multiply by 60 to get from min. to hrs = 190.303mph. Then take a 1:1 of 80mph divide 190.303mph divided by 80mph = 2.378788 for a ratio. (the first time I did it I was off on the mile and had 5260' when I should have had 5280')

But this is a ratio if you have 8" drivers, if you factor in the height of the track then the height of the lug it can really change. this is a ratio if you only count the driver size. So if you take the 2.378788 gear up then the 2.24 gear down at 8000 rpm and 60/60 gears in a 1:1, then subtract the two and you get = .138788 then multiply it by 80 =11.10 and because its a gear up you add it to 80 to get 91.10mph 57/63 gears 82.42mph 55/65 = 77.08mph

I could be way off on this but its making sense to me.

OK, I see how you are trying to calculate it, but where does the 8" across the clutch number come from? Are you assuming that when the clutches are 1:1 that the belt is 8" in diameter in the primary and secondary?

 

[WyoBoy1000]

So then if I am only able to pull 48 MPH it does make sense to gear down in order to bring my clutches closer to the target 1:1 ratio with the available power I have in my sled. As per the calculations, there is no way I can be at 1:1 at 48 MPH with 57/63 gears in my DD, correct?

Go back to the beginning, you can hit any gear with the cvt clutching with out actually changing gears, higher gears just expand the range of that gear, what every is thinking with a 1:1 is that you can get the best belt grip at a 1:1, but with the right clutching you can do the same thing with out being in a 1:1. But it is this theory that helps, with bad clutching its a good thing because it greatly increases grip, but for good clutching it wont change anything.

OK, I see how you are trying to calculate it, but where does the 8" across the clutch number come from? Are you assuming that when the clutches are 1:1 that the belt is 8" in diameter in the primary and secondary?

Yep. I just started punching numbers, and it made sense so if you can find a fault lets figure it out. I would like to get this figured out because its obvious no one has really figured it out before.

 

[mynewuseddoo]

Go back to the beginning, you can hit any gear with the cvt clutching with out actually changing gears, higher gears just expand the range of that gear, what every is thinking with a 1:1 is that you can get the best belt grip at a 1:1, but with the right clutching you can do the same thing with out being in a 1:1. But it is this theory that helps, with bad clutching its a good thing because it greatly increases grip, but for good clutching it wont change anything.

Ok I see where you are coming from now. I get the infinite adjustability with the clutches and the range they will allow within a certain gear ratio. I just think that with a lower gear set and the power which my set up currently produces will allow the clutches to bring my track to a higher speed over all, under loaded conditions as compared to the stock gears I am running. Or if I cranked the boost up to 15 psi to produce higher power, the 57/63 gears I currently have will allow my track to spin faster also because they may work better with the extra power. And like wise with the lower gear set with the higher power, if I was running 15 psi with the 54/66, I might find that there is not enough gear to allow the transmission to bring the track up to its full speed potential, ie; out of range.

54/66 may work best up to 10-12 psi boost?
57/63 may work best up to 15-16 psi boost?
60/60 may work best with 18+ psi boost?

That's all I'm trying to get at, where is the happy spot?

I haven't noticed any belt slippage or excessive clutch heat and my shifting up and down are both good. I am assuming that my clutches are set up correctly then....yes I'm still the clutch greenie

The only other thing I can think of doing would be to lighten the secondary spring to allow the primary to overcome and pull the belt lower into the secondary sheaves and bring the track speed up that way. This would hurt back shift though and put a lot more stress on the belt. This could also bring the RPM down as well so now I lighten my primary weights to compensate and now there is not as much force pulling the belt into the secondary.....and around and around and around. Trial and error I guess

LOL, I can't wait to get home and start tinkering!!! Damn over seas work!

Anybody got the winning lotto numbers for next week?

 

[Jeff K]

OK, I see how you are trying to calculate it, but where does the 8" across the clutch number come from? Are you assuming that when the clutches are 1:1 that the belt is 8" in diameter in the primary and secondary?

Yep. I just started punching numbers, and it made sense so if you can find a fault lets figure it out. I would like to get this figured out because its obvious no one has really figured it out before.

I don't think you can equate 1:1 to any actual number because there are too many variables (ie. Belt Length, Belt Thickness, etc). This is what I was trying to explain earlier, but I guess it didn't come out right.

Lets say your belt is X" long and at 1:1 you know it is 8" diameter in both clutches. What happens if you put a belt on that is 1" shorter? or longer? Now at 1:1 the diameter in both clutches is not 8", but the track speed will be exactly the same, because it is still at 1:1.

What I am trying to say is that it does not matter what the diameter is in the clutches when talking about clutch ratios, and that is why the formula from the Aaen Clutch Tuning Handbook referenced in my earlier post does not try to figure it out. At 1:1, the secondary is turning the same speed as the engine and the only things that effect track speed at that point are Diamond Drive gearing and the Driver Diameter.

 

[CATSLEDMAN1]

So to focus on more track speed from good clutch tuning , assume all other variables are a constant:
track length lug height and suspension drag
snow conditions
angle of hill and length of inrun
200 hp sled that weighs 480 lbs with 190 lb rider
and we get 52 mph track speed

NOw what?

We have to determine what is limiting us to 52 mph.
Is the belt slipping. Engine might have enough hp for 60 track speed, but hot clutch 90% of time is a slipping belt, so? OK more tension on the secondary spring if its slipping there, does speed go up due to less slip or does the speed go down because the primary doesn't have enough power to pull the belt back up to the baseline ratio ?

If the clutch's are cool at baseline speed then less secondary spring tension may allow the primary to pull up to a higher ratio and more track speed. So you have to try that. stock cat clutch thats a shop tear down, that why I favor the adjustable spring tension, its a 5 minute stop. So 1/3 turn looser is more track speed. Good adjustment.

But if you go looser and it feels better then gets hot clutchs, what now ?
More track speed is less spring, but heat is belt beginning to slip ?

So, the adjustment left, lower gearing, that will give you less belt to clutch stress, it will take less spring tension to keep the rubber belt maintaining traction on that aluminum sheave face. M sled, too bad, another shop tear down, Old cases, easy to do n the hill in ten minutes to test theory.

So when cat made more HP for the M in 2010, but use the same clutch's, same belt, same drivetrain, some bright engineer decided to make the adjustment to head off belt issue, they dropped their gearing from 57/63 to 55/65. I say they didn't go far enough for where I ride. But a good step.

Any, something to think about. If engineering studies come up short, sometimes you have to resort to trial and error. By trail and error, I have found, riding cat up hill in close quarters, I have always had better clutching results being a little to low geared than being a little to high geared.

 

[WyoBoy1000]

I don't think you can equate 1:1 to any actual number because there are too many variables (ie. Belt Length, Belt Thickness, etc). This is what I was trying to explain earlier, but I guess it didn't come out right. Thats what I said from the beginning, and I also stated thing in a hypothetically correct, as if in a perfect world these would be your numbers to get a base line

Lets say your belt is X" long and at 1:1 you know it is 8" diameter in both clutches. What happens if you put a belt on that is 1" shorter? or longer? Now at 1:1 the diameter in both clutches is not 8", but the track speed will be exactly the same, because it is still at 1:1. like said in a perfect world

What I am trying to say is that it does not matter what the diameter is in the clutches when talking about clutch ratios, and that is why the formula from the Aaen Clutch Tuning Handbook referenced in my earlier post does not try to figure it out. At 1:1, the secondary is turning the same speed as the engine and the only things that effect track speed at that point are Diamond Drive gearing and the Driver Diameter.

^^^ This statement basically defeats the purpose of the CVT system all together. You are basically saying that if you put the primary and secondary in a gear and lock it up they will both be make the same rpm, but rpm in the CVT doesn't mean chit, rpm is only useful if you are shooting for maximum HP. So let eliminate thats and just say 8000rpm and leave it at that.

Maybe it would be useful to go back and re read the thread as I feel like I have already explained the fact that no matter which of the gears mention above you have in your sled I can still hit the same gear ration with the CVT system.

Going off of gear to hit clutching is just not how it should be done, you should pick some gears then build your clutching, Most people don't realize the importance of the way a clutch weight is loaded to get engagement and total force. If you have taller gears but will never see that much speed while climbing then you want the total force to be applied at your climbing speed, if you build the weight to give you this effect then drop gears you will shift past the sweet spot of the weight and start loosing performance. Basically I am saying if you focus on gear you might get lucky, if you build your clutching for your sled and the way you ride, thats what counts.

 

[mynewuseddoo]

So a 200 hp sled with a 63/57 DD can be clutched to perform, back shift, up shift and maintain track speed as well as a 54/66 DD in an identical steep climb in deep heavy snow conditions?

 

[never enough snow]

I have found the more you load a turbo with gearing the faster the track speed. That said you need to change your clutching as well. I have found if you gear down you will lose track speed . No math real world testing and a box of parts !

 

[WyoBoy1000]

Yes.

 

[Tonysnoo]

Hey guys, not trying to ruffle feathers here, but I see some of this getting off on a tangent.

My math is coming up with the some different answers, so I’d like to present something that works for me. I like to work from the final drive back in. For some of you this is well known, sorry to be a bore. I am going over this for some of the rest who want to know how all this works.

First off, most of us have 8 tooth drivers and 3” pitch 3X8 = 24”(2ft) circumference driver.

Now our diamond drives have two ratios in side of them. The input/spur gear and the planetary ratio. The planetary is fixed at 2.24, so we just have to figure out the input ratio and divide the fixed by it.

A 60/60 is easy to figure 2.24/(60/60) = 2.24 / 1 = 2.24
Now the 57/63 ……2.24 / (57/63) = 2.25/.905 = 2.47

Now the MPH at any given SECONDARY clutch RPM can be figured by the following formula:

RPM / final ratio X 2(circumference of driver) X 60(min in hour) / 5280(ft in mile)

Example M8(57/63)
8000 / 2.47 X 2 X 60 / 5280 = 73.6
Example M8 (60/60)
8000 / 2.24 X 2 X 60 / 5280 = 81.2
Example M1000 (60/60)
7400 / 2.24 X 2 X 60 / 5280 = 75.1

Now the other side of the debate here is the clutch ratio. I hear most of you all saying about the same thing, so bottom line….. if we have a 1:1 ratio in the clutches, then we match the engine RPM to the secondary clutch RPM so we then can assume track speed.

I don’t know if 1:1 in our clutches is actually 8” to 8” but I think we all agree it needs to be equal diameter to equal diameter to be 1:1 and be most efficient. Mr Aaen did a lot of work in that area and I gotta believe him.

I agree with many of you. Gearing is best matched to you, your sled, and your needs. I like low gears for 90% of my riding. I run high gears for messing with my buddies when I don't care about belt wear. I don’t really care which is for you. I just wanted to clear up some of the math to help with the decision.

Sorry for being so long winded, but I hope this helps for part of the question.

 

[Jeff K]

^^^ This statement basically defeats the purpose of the CVT system all together. You are basically saying that if you put the primary and secondary in a gear and lock it up they will both be make the same rpm, but rpm in the CVT doesn't mean chit, rpm is only useful if you are shooting for maximum HP. So let eliminate thats and just say 8000rpm and leave it at that. We are not trying to defeat the purpose of the CVT system, but we are trying to have it operate in its most efficient range....at or near 1:1. When you need to put the power to the ground, you want the have the least amount of drivetrain loss.

Maybe it would be useful to go back and re read the thread as I feel like I have already explained the fact that no matter which of the gears mention above you have in your sled I can still hit the same gear ration with the CVT system. Sure, BUT again I am talking about 1:1 where the clutching is most efficient.

Going off of gear to hit clutching is just not how it should be done, you should pick some gears then build your clutching, Most people don't realize the importance of the way a clutch weight is loaded to get engagement and total force. If you have taller gears but will never see that much speed while climbing then you want the total force to be applied at your climbing speed, if you build the weight to give you this effect then drop gears you will shift past the sweet spot of the weight and start loosing performance. Basically I am saying if you focus on gear you might get lucky, if you build your clutching for your sled and the way you ride, thats what counts. Agreed. Whatever gearing you choose, your clutching needs to be set up properly to get the most out of it.

Comments in blue.

 

[Jeff K]

Hey guys, not trying to ruffle feathers here, but I see some of this getting off on a tangent.

My math is coming up with the some different answers, so I’d like to present something that works for me. I like to work from the final drive back in. For some of you this is well known, sorry to be a bore. I am going over this for some of the rest who want to know how all this works.

First off, most of us have 8 tooth drivers and 3” pitch 3X8 = 24”(2ft) circumference driver.

Now our diamond drives have two ratios in side of them. The input/spur gear and the planetary ratio. The planetary is fixed at 2.24, so we just have to figure out the input ratio and divide the fixed by it.

A 60/60 is easy to figure 2.24/(60/60) = 2.24 / 1 = 2.24
Now the 57/63 ……2.24 / (57/63) = 2.25/.905 = 2.47

Now the MPH at any given SECONDARY clutch RPM can be figured by the following formula:

RPM / final ratio X 2(circumference of driver) X 60(min in hour) / 5280(ft in mile)

Example M8(57/63)
8000 / 2.47 X 2 X 60 / 5280 = 73.6
Example M8 (60/60)
8000 / 2.24 X 2 X 60 / 5280 = 81.2
Example M1000 (60/60)
7400 / 2.24 X 2 X 60 / 5280 = 75.1

Now the other side of the debate here is the clutch ratio. I hear most of you all saying about the same thing, so bottom line….. if we have a 1:1 ratio in the clutches, then we match the engine RPM to the secondary clutch RPM so we then can assume track speed.

I don’t know if 1:1 in our clutches is actually 8” to 8” but I think we all agree it needs to be equal diameter to equal diameter to be 1:1 and be most efficient. Mr Aaen did a lot of work in that area and I gotta believe him.

I agree with many of you. Gearing is best matched to you, your sled, and your needs. I like low gears for 90% of my riding. I run high gears for messing with my buddies when I don't care about belt wear. I don’t really care which is for you. I just wanted to clear up some of the math to help with the decision.

Sorry for being so long winded, but I hope this helps for part of the question.

Agreed. Your numbers are the same as mine, just calculated differently.

 

[WyoBoy1000]

What is getting me is I thought you got circumference by multiplying the diameter by 3.14. So 8x3.14= 25.12 not 24" But that comes out to about 85mph, not sure on what is going on.

 

[Jeff K]

What is getting me is I thought you got circumference by multiplying the diameter by 3.14. So 8x3.14= 25.12 not 24"

That is how you calculate circumference from a diameter, but for the drivers the "8" is the number of teeth, and the pitch (3.0") is the distance between the teeth on the circumference, so it is just 8 x 3.0 = 24"

 

[WyoBoy1000]

Well, if you look at it that way it changes everything, so the driver size is actually 7.64".

Now tell me this take out everything and tell me the ratio going from the crank to 8" across in the primary. Because I figured it to be 2.37 and you are telling me it should be figured as 2.093. I am assuming What I missed was to factor in 1" diameter to discount the 8" diameter. which would be 3.14x8000=25120 /12=2093.333/5280 x 60= 23.7879mph -- 190.303 =166.5151 / 80=2.08, pretty close to the 2.09 which could be just from carrying numbers over.

But with a 7.64" driver your numbers should be right, If you add the thickness of the flat part of the track you would be pretty close to a 85mph,

I was thinking in my rushed state of factoring I was missing something, but at least we know now, I think?


So your figures would have 55/65 running about 69mph.

Now back to the argument if you need lower gears or not.

 

[Jeff K]

Well, if you look at it that way it changes everything, so the driver size is actually 7.64".

Now tell me this take out everything and tell me the ratio going from the crank to 8" across in the primary. Because I figured it to be 2.37 and you are telling me it should be figured as 2.093. I am assuming What I missed was to factor in 1" diameter to discount the 8" diameter. which would be 3.14x8000=25120 /12=2093.333/5280 x 60= 23.7879mph -- 190.303 =166.5151 / 80=2.08, pretty close to the 2.09 which could be just from carrying numbers over.

But with a 7.64" driver your numbers should be right, If you add the thickness of the flat part of the track you would be pretty close to a 85mph,

I was thinking in my rushed state of factoring I was missing something, but at least we know now, I think?


So your figures would have 55/65 running about 69mph.

Now back to the argument if you need lower gears or not.

Yes, 55/66 gears should be about 69mph at 1:1.

Regardless of whether it is best to gear up or down, we at least can agree now about the rough speeds at 1:1 with the different DD gears. My theory was to gear lower so that my clutches were operating closer to 1:1 at my track speeds in deep heavy snow. It works for me.

 

[WyoBoy1000]

Yes, 55/66 gears should be about 69mph at 1:1.

Regardless of whether it is best to gear up or down, we at least can agree now about the rough speeds at 1:1 with the different DD gears. My theory was to gear lower so that my clutches were operating closer to 1:1 at my track speeds in deep heavy snow. It works for me.

Agreed, I get what you where doing and why everyone thinks this way, at one time I was going to do it, but when some guys did it on piped m1000's and they said it was way better and then I beat them. It was back to square one. There belts lasted longer, but thats just compensating for bad clutching and motor movement. All in All I think I can get just as good or maybe better with clutching, not gears.

 

[Tonysnoo]

Well, if you look at it that way it changes everything, so the driver size is actually 7.64".

Now tell me this take out everything and tell me the ratio going from the crank to 8" across in the primary.

But with a 7.64" driver your numbers should be right, If you add the thickness of the flat part of the track you would be pretty close to a 85mph,

QUOTE]

I would suspect (if I read and understood your post correctly), if your belt was riding in your primary clutch at aproximately 4" from center(8" total diam) you would be in overdrive past 1:1/

This is the first time I actually bothered to try to figure out at what diameter 1:1 was in a clutch system.

Follow with me and make sure my logic is OK.

The belt for our sleds is a little longer than 46" so I am going to round off. The center to center distance of the clutches is 11.5" So visualize if we have both clutches at the same diameter belt print then we would have 11.5 X 2 (23") used up in space between the two clutches. That would leave 23" left over to go around 1/2 of the drive and 1/2 of the secondary. Since we have 2 halves that are equal, then we could just treat them as a whole for calculating purposes. That would tell me that 23/3.1416 = 7.3"

I would have to say that anything outside of that 7.3" diameter(in the primary) would start to get into clutch overdrive. Then the speed calcs above get increased by whatever percentage of overdrive you achieve.

Wow, that hurt my feeble brain.......LOL

 

[WyoBoy1000]

LOL. I did all the math once and came up with 8" as a 1:1, but that was measuring the outside of the belt and saying the outside of the belt would be sitting at the 8" point and then going inward. So the inside of the belt may very well be at the 7.3" diameter. ???

This is where I go back to "there is to many variables"

Something else I was thinking of that kinda makes sense.

When you figure track speed lets say you figure it for the speed at the drivers- like we where figuring speed, but from are math above what if these turbo's , with there "big track speed" that they are more likely to plain out and might be running more on the tips of the track where as the NA sleds are digging and running on the bottom of the lugs rather than on the tips like the turbo. So even if you go 1/2" further out on the lugs puts you a full 1" larger diameter which makes for some serious speed increases. Kinda makes sense.