i'm with don here cause we did alots of test on polaris ,artic cat and yammy and radar run and race 600 and 1200 and the way to go fast is to run without overdrive or minimum possible
i think people should not run more than 10% in overdrive but i'm sure don know how to calculate how mutch overdrive your running i forgot how to calculate that overdrive in %
Hi Mac, I will try and explain it like this, I dont want to say "percentages per foot" because I dont have and I know nobody here has that information.
Anytime you gear the sled down(lower numeric number) you take the load "OFF" the engine, the engine does not work as hard because the gearing helps to pull the load by multiplying torq from the engine, we all can agree on that.. right?? However, the steeper gearing also does not increase your mph the same as it lowers your elapsed time, it will quicken the sleds elapsed time but not necessasarly its mph. I will also say again from other previous post ,you need MORE MOTOR HP to run taller gearing, if your down on HP then ,yes, steeper gearing will work better then taller. If you have alot of power, taller gearing will be faster! Gearing taller does have its drawbacks per say to the hp to weight ratio of the sled. For the most part we ALL have something done to our sleds, no matter if its triple aftermarket pipes, porting, bigbores, bigger carbs whatever, some kind of power adder, so we all will fall into the "added hp" percentile for this.
This is very easy to see when you race asphalt, the time slips you get every pass shows you exactly what has happened with changes. You can see your 60ft time drop with deeper gearing, your 330ft time will also improve because of the shorter distance but you will lstart and progress LOSE your 660ft and 1000-1320ft MPH because the clutch basicly is shifted out faster and you are transferring less power, the clutch can easily get ahead of the engine this way. If you overshift the sled the engine can easily be pulled from peak till the engine catchs up with the clutchs. The less time you are on the track for whatever distance the less time you have to build mph. So in very short races, "yes" deeper gearing is the way to go WITHIN reason. I will provide another example of how a "too deep" for a short race can also bite you back.
Lets jump to 500ft grass racing, ever seen a sled dart out of the hole and hold the lead till about 350-400ft and then another sled will creep by that didnt have the holeshot, and take the win?? That was because most likely the sled that got the best holeshot was geared too deep, he transferred more torq(which moves the load easier from a stationary spot), the machine now moving, needs maximum hp (transferred) to keep the mph gaining, the sled that didnt get the same holeshot passed it because he was transferring more hp to the ground for a longer time within the race track length! The gearing being taller, loads the engine more and makes the engine work more productive in the terms the clutch and engine work together, the clutch is not ahead of the engine nor is the engine ahead of the clutch, having a straight shift curve and being in a better part (more efficient)of the shift curve was able to gain more mph within the distance(its faster!). It still goes back to being able to hang onto the largest part of the belt(most length clamped by the sheaves) in both the primary and the secondary clutch. The more belt length you can hang onto the more power can be transferred to the drivetrain. If the sled is light enough with a good amount of HP the acceleration actually INCREASES because less time is spent revving the engine and more time is spent moving forward, simply because your in a better more efficient part of the shift curve!
Anytime you gear the sled down(lower numeric number) you take the load "OFF" the engine, the engine does not work as hard because the gearing helps to pull the load by multiplying torq from the engine, we all can agree on that.. right?? However, the steeper gearing also does not increase your mph the same as it lowers your elapsed time, it will quicken the sleds elapsed time but not necessasarly its mph. I will also say again from other previous post ,you need MORE MOTOR HP to run taller gearing, if your down on HP then ,yes, steeper gearing will work better then taller. If you have alot of power, taller gearing will be faster! Gearing taller does have its drawbacks per say to the hp to weight ratio of the sled. For the most part we ALL have something done to our sleds, no matter if its triple aftermarket pipes, porting, bigbores, bigger carbs whatever, some kind of power adder, so we all will fall into the "added hp" percentile for this.
This is very easy to see when you race asphalt, the time slips you get every pass shows you exactly what has happened with changes. You can see your 60ft time drop with deeper gearing, your 330ft time will also improve because of the shorter distance but you will lstart and progress LOSE your 660ft and 1000-1320ft MPH because the clutch basicly is shifted out faster and you are transferring less power, the clutch can easily get ahead of the engine this way. If you overshift the sled the engine can easily be pulled from peak till the engine catchs up with the clutchs. The less time you are on the track for whatever distance the less time you have to build mph. So in very short races, "yes" deeper gearing is the way to go WITHIN reason. I will provide another example of how a "too deep" for a short race can also bite you back.
Lets jump to 500ft grass racing, ever seen a sled dart out of the hole and hold the lead till about 350-400ft and then another sled will creep by that didnt have the holeshot, and take the win?? That was because most likely the sled that got the best holeshot was geared too deep, he transferred more torq(which moves the load easier from a stationary spot), the machine now moving, needs maximum hp (transferred) to keep the mph gaining, the sled that didnt get the same holeshot passed it because he was transferring more hp to the ground for a longer time within the race track length! The gearing being taller, loads the engine more and makes the engine work more productive in the terms the clutch and engine work together, the clutch is not ahead of the engine nor is the engine ahead of the clutch, having a straight shift curve and being in a better part (more efficient)of the shift curve was able to gain more mph within the distance(its faster!). It still goes back to being able to hang onto the largest part of the belt(most length clamped by the sheaves) in both the primary and the secondary clutch. The more belt length you can hang onto the more power can be transferred to the drivetrain. If the sled is light enough with a good amount of HP the acceleration actually INCREASES because less time is spent revving the engine and more time is spent moving forward, simply because your in a better more efficient part of the shift curve!
Last edited:
yep all that theorie is good :-))) different set up in different race ....
Mac
Member
Don, I have read your replies several times and am having difficulty separating the issues. Possibly others are asking from a strickly drag race point of view. I think I’m personally trying to achieve two goals.
1. Faster 0-100 speed using a lower gear.
2. Faster top end using overdrive because I'm running out of gear.
Would I not see another 8-10mph on top end?
It appears to me that my clutch is slammed closed at 110 mph and preventing me from further advance. Overdrive seems to be the answer where I can have my cake and eat it too. Don if I go with the taller gear I will achieve higher MPH but won't have the low end speed.
We seem to agree lower gearing is faster.
Faster until when? Won't it be faster all the way till the primary is fully closed?
Does 1 to 1 occur when the primary is slammed closed or does it occur sooner? Where is the engineer in the family? Wheres Gary? LOL
Not meant to be argumentative. Its just not making sence to me from an engineering point of view. Wish I had timers.
1. Faster 0-100 speed using a lower gear.
2. Faster top end using overdrive because I'm running out of gear.
Would I not see another 8-10mph on top end?
It appears to me that my clutch is slammed closed at 110 mph and preventing me from further advance. Overdrive seems to be the answer where I can have my cake and eat it too. Don if I go with the taller gear I will achieve higher MPH but won't have the low end speed.
We seem to agree lower gearing is faster.
Faster until when? Won't it be faster all the way till the primary is fully closed?
Does 1 to 1 occur when the primary is slammed closed or does it occur sooner? Where is the engineer in the family? Wheres Gary? LOL
Not meant to be argumentative. Its just not making sence to me from an engineering point of view. Wish I had timers.
I think what i'm getting from all this is that an overdrive shieve will only give you results if you gear down, wich will give more hp to the ground. But then your really not achieving anything on the top end because of the lower gear. So really an overdrive shieve is useless unless your making a ton of HP to overcome the tight belt radias and loss of power to the ground on the top end.
Mac
On my 780 Viper (I believe thats what you run) I've done quite a bit of testing using a primary with overdrive (obtained by cutting .050 off the bottom of both sheaves) against a stock primary. I saw basically 1-2 MPH difference in top end speed (on the speedo) with all other variables remaining constant. Yes, I took the weights, rollers, and spring out of the cut primary and put them in the stock one. I also experimented with gearing down that day and what I found was that the sled wanted to be quicker out of the hole but in reality I just couldn't hook up that gearing. You may think that gearing down is going to help but if you can't hook it up it's not going to help at all. No, I didn't have a weight transfer or traction problem as I was running a 136" Expert-X with 1 1/4 track and plenty of picks. I chalked up the fact that I couldn't gain any more top speed to the fact that you can only spin a track that size and weight so fast. Now for the result that I'm sure Buffalo Bob will want to argue about. I geared the sled up one tooth. It was better out of the hole with less spinning and it improved my short run times. It was better in the mid range pull. There was NO change in top end speed. Think outside the box. End result was that the 780 made more power and could therefore handle more gear and that's what I gave it. Hope this helps. By the way, I no longer use the clutch that I had cut because it developed some nasty hair line cracks near the bottom of both sheaves where it was cut.
Madmatt
On my 780 Viper (I believe thats what you run) I've done quite a bit of testing using a primary with overdrive (obtained by cutting .050 off the bottom of both sheaves) against a stock primary. I saw basically 1-2 MPH difference in top end speed (on the speedo) with all other variables remaining constant. Yes, I took the weights, rollers, and spring out of the cut primary and put them in the stock one. I also experimented with gearing down that day and what I found was that the sled wanted to be quicker out of the hole but in reality I just couldn't hook up that gearing. You may think that gearing down is going to help but if you can't hook it up it's not going to help at all. No, I didn't have a weight transfer or traction problem as I was running a 136" Expert-X with 1 1/4 track and plenty of picks. I chalked up the fact that I couldn't gain any more top speed to the fact that you can only spin a track that size and weight so fast. Now for the result that I'm sure Buffalo Bob will want to argue about. I geared the sled up one tooth. It was better out of the hole with less spinning and it improved my short run times. It was better in the mid range pull. There was NO change in top end speed. Think outside the box. End result was that the 780 made more power and could therefore handle more gear and that's what I gave it. Hope this helps. By the way, I no longer use the clutch that I had cut because it developed some nasty hair line cracks near the bottom of both sheaves where it was cut.
Madmatt
u can't be fast everywhere
Ya
Like Mod said.........when it comes to clutching there is not such thing as having your cake and eating it too!
Madmatt
Like Mod said.........when it comes to clutching there is not such thing as having your cake and eating it too!
Madmatt
well if u follow those race you will see they are not clutch and gear the same for eatch differente race depend how long the race ..........
mac,
I will say 1;1 ratio is well before the clutch closes the sheaves together.1:1 is with the belt about 1/2 to 5/8 up the sheaves in the front, you can see exactly what ratio your in if you use this formula: engine rpm x sprocket pitch diameter divided by your MPH x gearing x 336
Lower gearing is faster on take off but only out so far and that depends soley upon the traction available! In the grass race example we are talking 60ft times, some sleds gain more by gearing taller in the 60ft because less time is spent spinning the rpms and more time spent moving the sled forward.
Like madmatts sled example, he got better traction from the taller gearing which improves your 60ft time(take off) if you have more engine power taller gears can be even faster if the sleds power to weight ratio is in check.
The trick is too gear as tall as you can without losing your acceleration, thats your decision on how far you go, remember the steeper the gear the less traction youll most likely get from excessive spinning of the track.
I will say 1;1 ratio is well before the clutch closes the sheaves together.1:1 is with the belt about 1/2 to 5/8 up the sheaves in the front, you can see exactly what ratio your in if you use this formula: engine rpm x sprocket pitch diameter divided by your MPH x gearing x 336
Lower gearing is faster on take off but only out so far and that depends soley upon the traction available! In the grass race example we are talking 60ft times, some sleds gain more by gearing taller in the 60ft because less time is spent spinning the rpms and more time spent moving the sled forward.
Like madmatts sled example, he got better traction from the taller gearing which improves your 60ft time(take off) if you have more engine power taller gears can be even faster if the sleds power to weight ratio is in check.
The trick is too gear as tall as you can without losing your acceleration, thats your decision on how far you go, remember the steeper the gear the less traction youll most likely get from excessive spinning of the track.
Mac
Member
Overdrive answers Thanks Everyone
I'm convinced - I give up. My overdrive quest is over. Lots of answers thanks to Mad Matt & Mr. Viper. Those are the answers I was looking for. Matt the cracked clutch remark took all the fun out of this thread. Also 1-2 mph gain didn’t help. The 1-1 ratio happens much sooner than I would have guessed. All this engineering fun and Gary never showed up shouting and yelling at us?
I'm convinced - I give up. My overdrive quest is over. Lots of answers thanks to Mad Matt & Mr. Viper. Those are the answers I was looking for. Matt the cracked clutch remark took all the fun out of this thread. Also 1-2 mph gain didn’t help. The 1-1 ratio happens much sooner than I would have guessed. All this engineering fun and Gary never showed up shouting and yelling at us?
No Gary and his wild stories,that did take some of the fun out of it didnt it....LOL 
mac, if you want to feed your brain a bunch of engineering information pick up a Aaen clutching book, you may need to read it 2 or 3 times to get a hold of all the information but its worth it.
mac, if you want to feed your brain a bunch of engineering information pick up a Aaen clutching book, you may need to read it 2 or 3 times to get a hold of all the information but its worth it.
bufalobob
Member
mrviper:
this thread started by vintage srx simply asked if the hauck overdrive sheave was worth buying. i responded & gave him another option - that works quite well.
i've stated twice that i have a bunch of hours in r&d with radar & timers & lots of notes but you still persist with an extended diatribe of theories & conjecture of why o.d. does not work?? so the only conclusion that i can draw is you think i am not being truthful?? how about asking how i got it to work instead of purporting yourself to be the clutching god. you just may learn something.
bob
this thread started by vintage srx simply asked if the hauck overdrive sheave was worth buying. i responded & gave him another option - that works quite well.
i've stated twice that i have a bunch of hours in r&d with radar & timers & lots of notes but you still persist with an extended diatribe of theories & conjecture of why o.d. does not work?? so the only conclusion that i can draw is you think i am not being truthful?? how about asking how i got it to work instead of purporting yourself to be the clutching god. you just may learn something.
bob
2ooosrx
VIP Member
- Joined
- Oct 2, 2004
- Messages
- 2,414
- Age
- 35
- Location
- Gurnee, Illinois
- Website
- www.cbperformanceparts.com
Bob,
Amen..............to that brother, we have had tons of luck with our Overdrive setup aswell and it continuously outperforms the stock sheeve. The overdrive sheeve is not just bolting and go though, there are things you must do to the secondary aswell in order to get them in harmony and to outperform the stock setup.
Amen..............to that brother, we have had tons of luck with our Overdrive setup aswell and it continuously outperforms the stock sheeve. The overdrive sheeve is not just bolting and go though, there are things you must do to the secondary aswell in order to get them in harmony and to outperform the stock setup.
Last edited:
How about YOU just pick up a book and read it? Would that be too much to ask?? Or is it easier to sit there and cut something down with no information to validate you? I will send you one if you cant afford one, send me your address. Then you can read it and apply the information and you might actually just gain some knowledge instead of just cutting down something you dont even understand, no theories here, real information! Your the one who is hard headed and cant stand anything that is "against what you think is the way", its always Bob's way, Benders way or the highway with you. I am not gonna argue with you, its pointless as always. You brought up invalid points(excuses and examples that didnt apply) and I supplied answers, you dont like that. The track dyno clearly shows your losing power up there, and again its all in the book written by Olav Aaen, I am sure you know more then him as well so I just say read the book. When your done reading it and learning something, send it to Bruce so he can read it. You have the offer here to get the book if youll read it.
Send me your address..........
Send me your address..........
bufalobob
Member
2000srx:
sounds like you've done your homework!
ski doo clutches are 17% o.d.. i guess they didn't read olav's book.
bob
sounds like you've done your homework!
ski doo clutches are 17% o.d.. i guess they didn't read olav's book.
bob
mrviper700 said:Scott, We already know that overdrive will lose approx. at least 10% of the power output, so if you have a 100hp engine , 1;1 will be about 90hp to the track in your example srx to the ground, running in overdrive youll be applying 80hp, so 80 hp would be faster then 90hp to the ground across the lake???
You need MAXIMUM HP to attain topend, down 10hp... your not going to beat the other at 90hp to the ground.
thank you for proving me right, you forgot that the one with od was geared down one tooth so it is putting more hp to the ground right up through the ratios because they both have the same power. when the one with od finally goes into that part of the clutch it has put more power to the ground for a longer period of time and will be ahead of the other sled.
on the trail i run od for this reason that i have not seen anyone mention.
trail riding clutching works different than lake racing, if you watch your belt at top speed it is pulsing up and down as the load changes, up and down, bouncing up the clutch and down as you hit bumps and the suspension changes load on the clutches. on the trail i will gear my sled with stock gearing or as on my viper up one. this alowed me to get the track to hook up. mechanicly with 23/38 gears in my viper there is no way i could take advantage of od, right???, wrong. a marked line on the clutch showed me that indead the belt will on long runs bounce up past the stock height into the od i cut into it. if i had not cut it, the belt would bounce up into this spot and have not side presure, thus slipping the belt at top speed.
im sure it doesnt happen like that cause it doesnt say it in a book.
man this thread must have od cause it sure moves fast.
Come on guys, you are arguing over nano-differences and decimals. Can't you agree to disagree before everybody's all PO'd? There's too much good info passed along on this forum to have any posters lost IMO. Man do we need snow or what?
Besides, life's too short - really
Besides, life's too short -
really
Last edited:
I'm not arguing!
Hey, I'm not arguing.....just trying to report what I found in my testing. I would be interested in how Buffalobob and Matt made their overdrives work so well. If you guys dont want to give away your secrets on the board then PM them to me if you would! I'll try anything!!!! BY the way Mac......I've seen lots of stock clutches develop cracks down low too. I'm not saying it was because they were cut.........but I'm sure it didn't help!
Madmatt
Hey, I'm not arguing.....just trying to report what I found in my testing. I would be interested in how Buffalobob and Matt made their overdrives work so well. If you guys dont want to give away your secrets on the board then PM them to me if you would! I'll try anything!!!! BY the way Mac......I've seen lots of stock clutches develop cracks down low too. I'm not saying it was because they were cut.........but I'm sure it didn't help!
Madmatt