Official Baja SAE Forums Homepage
Forum Home Forum Home > General > Design Discussion
  New Posts New Posts RSS Feed - Preferred CVT
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Preferred CVT

 Post Reply Post Reply Page  <1234>
Author
Message
adrive7 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Oct/19/2008
Location: Lancaster, CA
Status: Offline
Points: 711
Post Options Post Options   Thanks (1) Thanks(1)   Quote adrive7 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/23/2009 at 1:39pm
If you are a new team, I would recommend trying to get a CVTech and working with that. You only need to pay shipping, the unit is free to Baja teams, and requires no modifications for use on a baja car. The driver mates right up to the Briggs, and the driven uses a key.

The P90 is going to be a big headache, I promise.
-Joe
Chief Organizer, Baja California 2016, 2017, 2019
Ohio State Baja 2005-2009
Co-Host, Science... Sort Of
http://www.sciencesortof.com
Back to Top
BroncoBaja View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Oct/23/2009
Status: Offline
Points: 12
Post Options Post Options   Thanks (1) Thanks(1)   Quote BroncoBaja Quote  Post ReplyReply Direct Link To This Post Posted: Nov/05/2009 at 5:41pm
A headache? Just tuning issues? Polaris has recommended weights and spring is it not just plug and play?

Anyone use EBS belts on the P90 and what mods are required?  My guess would be just adjusting the spacing of the sheaves.
Boise State University
Mechanical Engineer Major
Newb
Back to Top
adrive7 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Oct/19/2008
Location: Lancaster, CA
Status: Offline
Points: 711
Post Options Post Options   Thanks (0) Thanks(0)   Quote adrive7 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/05/2009 at 5:58pm
The headache is making it hook up to everything. There is a lot of custom machining required to mate the driver to the engine, and the driven requires splines.
-Joe
Chief Organizer, Baja California 2016, 2017, 2019
Ohio State Baja 2005-2009
Co-Host, Science... Sort Of
http://www.sciencesortof.com
Back to Top
iwm View Drop Down
Bolt Sorter
Bolt Sorter


Joined: Jul/09/2009
Status: Offline
Points: 23
Post Options Post Options   Thanks (0) Thanks(0)   Quote iwm Quote  Post ReplyReply Direct Link To This Post Posted: Nov/13/2009 at 9:40pm



Edited by iwm - Nov/14/2009 at 12:20am
Back to Top
jeiB View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Jul/17/2009
Location: Montreal
Status: Offline
Points: 604
Post Options Post Options   Thanks (0) Thanks(0)   Quote jeiB Quote  Post ReplyReply Direct Link To This Post Posted: Nov/14/2009 at 12:10am
Hey,

Its true that the CVtech is pretty ridiculous in terms of shift range, close to 7:1, when in reality anything under 6:1 would work (calculated for torque to climb a 35incline and a top speed of 40mph). Whats good about that thought is that you can try different ratios (test for more torque or more top speed) and not get penalized. Thats the main reason i really like the CVTech this year, it really enables you to explore a bit in terms of acceleration and top speed. The only i would see not to try it is the pretty extreme overdrive ratio but im pretty sure the guys at cvtech know what they are doing.

You say that rotating mass of gearbox increases etc...but the cvtech is also considerably smaller than the previous year's one, so you save quite a bit as well.

We have a 9:1 gearbox from 2 years ago and a gearbox of 15:1 for this year and i can tell you that the weights are pretty close (we improved our weight relief in the gears thought)

Jeremie B.
McGill Baja Racing
2009-2011 Captain
minibaja.mcgill.ca
Back to Top
jeiB View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Jul/17/2009
Location: Montreal
Status: Offline
Points: 604
Post Options Post Options   Thanks (0) Thanks(0)   Quote jeiB Quote  Post ReplyReply Direct Link To This Post Posted: Feb/14/2011 at 1:13pm

So apparently they are a lot of jr dragster cvt that I didnt know about !

  1. Shockwave clutchs by jr race car (http://www.jrracecar.com/pages.asp?pid=5)
  2. Polar ATAC (http://www.polarracing.com/catalogue/index.html)
  3. Supreme Tool clutch (http://supremetoolinc.com/cart/junior-dragsters-c-22.html?zenid=4d1710aa137da8fe1daf2426984f052a)

Anymore?

Now my question is: Is it really worth it spending 1000$ for these?

Looking at the results from 2010 in

Carolina accel event







1

Universidade de Sao Paulo

4.675

comet

2

Universite Laval

4.709

cvtech

3

Centro Universitario Da FEI

4.718

cvtech/polaris hybrid

4

Instituto Maua de Tecnologia

4.734

comet

5

Tennessee Tech Univ

4.838

gaged

6

Ecole De Technologie Superieure

4.892

cvtech

7

Univ of Maryland - College Park

5.015

gaged/polar hybrid

8

LeTourneau Univ

5.022

?

9

Universidad De La Salle Bajio

5.033

?

10

Universite de Sherbrooke

5.093

cvtech





Washington accel event







1

Universite Laval

4.957

cvtech

2

Univ of Maryland - College Park

5.018

gaged/polar hybrid

3

Ecole De Technologie Superieure

5.048

cvtech

4

Univ of Wisconsin - Madison

5.099

gaged?

5

Univ of Maryland - Baltimore County

5.151

?

6

Wichita State Univ

5.192

?

7

South Dakota Sch of Mines & Tech

5.242

comet

8

North Carolina State Univ - Raleigh

5.263

gaged

9

Oregon State Univ

5.273

polaris

10

Univ of South Florida

5.282

gaged

 

Im not sure about some of the teams cvts. I can modify the post if someone knows.

 EDIT: updated list



Edited by jeiB - Feb/14/2011 at 5:42pm
Jeremie B.
McGill Baja Racing
2009-2011 Captain
minibaja.mcgill.ca
Back to Top
CLReedy21 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Nov/30/2008
Location: Marysville, OH
Status: Offline
Points: 736
Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/14/2011 at 1:44pm
I can definitely confirm your guesses for Oregon and USF at Washington, and I think you got SDSMT correct as well.

The only note that I would make is that our 2010 car was somewhat of a porker.  Curb weight was something like 430 lbs for Carolina what with all the power steering and such.

Also for anybody wondering what was up with us at RIT we failed big time in accel due to a number of factors, most of which were my fault.  Lessons learned for this year I suppose.
-Chris Reedy
TTU Alumni
Fourwheeler Drawer



"Quick with the hammer, slow with the brain."
Back to Top
Greenreed1936 View Drop Down
Bolt Sorter
Bolt Sorter


Joined: Aug/31/2009
Location: Rapid City
Status: Offline
Points: 24
Post Options Post Options   Thanks (0) Thanks(0)   Quote Greenreed1936 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/14/2011 at 2:05pm
Hate to break it to you, but for SDSMT that was not a Gaged CVT on that car.  
SDSMT BAJA SAE
Back to Top
CLReedy21 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Nov/30/2008
Location: Marysville, OH
Status: Offline
Points: 736
Post Options Post Options   Thanks (0) Thanks(0)   Quote CLReedy21 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/14/2011 at 2:17pm
Like I said, I just thought it was a Gaged.  The new car was a Gaged right?  Was that the old car?
-Chris Reedy
TTU Alumni
Fourwheeler Drawer



"Quick with the hammer, slow with the brain."
Back to Top
Greenreed1936 View Drop Down
Bolt Sorter
Bolt Sorter


Joined: Aug/31/2009
Location: Rapid City
Status: Offline
Points: 24
Post Options Post Options   Thanks (0) Thanks(0)   Quote Greenreed1936 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/14/2011 at 2:29pm
Originally posted by CLReedy21 CLReedy21 wrote:

Like I said, I just thought it was a Gaged.  The new car was a Gaged right?  Was that the old car?


Yeah, the new car was Gaged.  But the old car was Comets all the way around
SDSMT BAJA SAE
Back to Top
jeiB View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Jul/17/2009
Location: Montreal
Status: Offline
Points: 604
Post Options Post Options   Thanks (0) Thanks(0)   Quote jeiB Quote  Post ReplyReply Direct Link To This Post Posted: Feb/14/2011 at 4:23pm
Originally posted by Greenreed1936 Greenreed1936 wrote:


Yeah, the new car was Gaged.  But the old car was Comets all the way around


So which car was it that got 7th in acceleration at Washington?
Jeremie B.
McGill Baja Racing
2009-2011 Captain
minibaja.mcgill.ca
Back to Top
Red_Beard View Drop Down
Organizer
Organizer


Joined: May/14/2009
Location: Bellingham, WA
Status: Offline
Points: 269
Post Options Post Options   Thanks (0) Thanks(0)   Quote Red_Beard Quote  Post ReplyReply Direct Link To This Post Posted: Feb/14/2011 at 4:35pm
Originally posted by jeiB jeiB wrote:

Originally posted by Greenreed1936 Greenreed1936 wrote:


Yeah, the new car was Gaged.  But the old car was Comets all the way around


So which car was it that got 7th in acceleration at Washington?


The old polished turd (2009 build) running the old crusty comet 790(?) series


Edited by Red_Beard - Feb/14/2011 at 4:36pm
SDSM&T 09-10 Team Lead
2nd & 9th Baja West

Project Engineer
Matrix Service - Bellingham, WA
Back to Top
João Araujo View Drop Down
Milling Master
Milling Master


Joined: Feb/07/2009
Location: Brazil
Status: Offline
Points: 61
Post Options Post Options   Thanks (0) Thanks(0)   Quote João Araujo Quote  Post ReplyReply Direct Link To This Post Posted: Feb/14/2011 at 4:59pm
USP uses COMET 790 
MAUA i'm pretty sure that they uses comet too
UFPBaja Team - Brazil
Back to Top
Akron 1998 to 2004 View Drop Down
Welding Master
Welding Master
Avatar
Thread Hijack Champion

Joined: Jan/20/2011
Location: WA
Status: Offline
Points: 327
Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/14/2011 at 6:03pm
I can tune a Comet 790 like a piano.
 
Back to Top
Invincible mechanics View Drop Down
Milling Master
Milling Master


Joined: Apr/24/2011
Location: INDIA
Status: Offline
Points: 46
Post Options Post Options   Thanks (0) Thanks(0)   Quote Invincible mechanics Quote  Post ReplyReply Direct Link To This Post Posted: May/01/2011 at 1:43pm
I am new to the topic CVT and working on it to use it in BAJA. I am reading Olav Aaens handbook but i have some doubts related to your writing. First of all i want to know what this line of yours mean( the speed you will be at when your CVT engages is 7.79 mph.). Does this line means that CVT engages with the engine when our vehicle has some speed. If it is so then how our vehicle start moving. Also how we can calculate the engagement speed. And from my point of view the conclusion according to you is that if we have an overdrive we will have more acceleration. Is it right. Please help.

Back to Top
SDTech View Drop Down
Milling Master
Milling Master
Avatar

Joined: May/13/2009
Location: Rapid City, SD
Status: Offline
Points: 68
Post Options Post Options   Thanks (0) Thanks(0)   Quote SDTech Quote  Post ReplyReply Direct Link To This Post Posted: May/02/2011 at 12:08am
Originally posted by Invincible mechanics Invincible mechanics wrote:

I am new to the topic CVT and working on it to use it in BAJA. I am reading Olav Aaens handbook but i have some doubts related to your writing. First of all i want to know what this line of yours mean( the speed you will be at when your CVT engages is 7.79 mph.). Does this line means that CVT engages with the engine when our vehicle has some speed. If it is so then how our vehicle start moving. Also how we can calculate the engagement speed. And from my point of view the conclusion according to you is that if we have an overdrive we will have more acceleration. Is it right. Please help.



Think about what you are saying a little bit and you'll answer most of your own questions.  Unless you have some weird form of dual transmission setup on your car or are always parked facing downhill, then obviously your clutch has to engage in order for the car to start moving, how else will power get from the engine to the wheels?  Calculating your engagement speed will take quite a bit more work than just trying it on your car and adjusting springs and weights from there to get whatever engagement speed you want.  Overdrive is good for top speed, not for torque.  Torque is good for acceleration.  Look at the ratio's on the cvt's and figure out whether overdrive will give you more torque to help acceleration...
SDSMT Baja SAE
Car #'s 4 & 6 - Oregon
Car # 14 - Wisconsin

#4 & #79 - Western Washington

2010-2011 SDSM&T Team Lead
Back to Top
jhu42 View Drop Down
Welding Master
Welding Master
Avatar

Joined: Jan/27/2009
Location: Columbus, Ohio
Status: Offline
Points: 145
Post Options Post Options   Thanks (1) Thanks(1)   Quote jhu42 Quote  Post ReplyReply Direct Link To This Post Posted: May/02/2011 at 11:26pm
Originally posted by Invincible mechanics Invincible mechanics wrote:

I am new to the topic CVT and working on it to use it in BAJA. I am reading Olav Aaens handbook but i have some doubts related to your writing. First of all i want to know what this line of yours mean( the speed you will be at when your CVT engages is 7.79 mph.). Does this line means that CVT engages with the engine when our vehicle has some speed. If it is so then how our vehicle start moving. Also how we can calculate the engagement speed. And from my point of view the conclusion according to you is that if we have an overdrive we will have more acceleration. Is it right. Please help.



Hi I.M. 

So the quote, ( the speed you will be at when your CVT engages is 7.79 mph.) Simply means this.  I classify the CVT engaging as when it begins to shift, or change ratios.  Everything up to this engagement point is the engine reving up, going from 100rpm to 200 rpm all the way up to your engagement point.  For Baja applications you want your engagement point to be like 3200-3400 rpms.  You want this because if you refer to the torque curves it is the point where the vehicle is producing maximum Horsepower.

Now you reach your engagement rpm of lets just say 3200 rpms, ( i say this because I did not have enough time in testing to find out what the perfect rpm was, I hypothesized that higher ones would be  better because the engine is producing more power, but not hard numbers to prove that :( ) Now at this rpm the weights in the CVT will reach a centrifugal force that will over power the drive spring and the main clutch will begin to compress, moving the belt up the main pulley and down on the secondary pulley.  This is when your ratio begins to change.  When I was captain I used the CVTECH CVT which has a low ratio of 3:1 and high ratio of 0.43 :1 ,  So when your drive clutch compresses your ratio will shift.  3:1, 2:1, 1:1, all the way to 0.43:1.  It is important to note that during this change in ratios of your CVT your engine will stay at the engagement RPM.  The Clutch is varying itself to keep the engine at that speed, this is why it is important to make it be a ratio that is a good HP value for your engine. 

Consider what would happen if your weighs in your CVT prompted the CVT engagement speed at 2000 rpms.  the effect would be going through the same CVT ratios but with a drop in HP.  this is because at 2000 rpms the engine produces less power than the engine at 3400 rpms


- Hope I'm not boring you but getting the most out of the CVT unfortunately requires a fundamental understanding of the forces at work, I'm still learning this stuff too so this is by no means infallible...

Ok I.M. ! Now getting to your core questions , CVT engagement speed can be calculated by looking at your engagement RPM and then seeing how fast your car will be going when you are engaging the CVT.  So when I said 7.79 I was looking at the engagement rpm and then seeing how fast the car would be going at that rpm.  This speed is important because it is the speed where the engine goes into its full HP rate.  At any speed above this speed the engine will continue to have the same HP as when you engaged.  At any speed lower the engine power will be reduced because rpms will drop.

There is a calculation theoretically to find your engagement speed, but its not accurate.  The math of the CVT is much too complex and prone to errors due to a lack of measurement.  I would recommend using a tachometer ( similar to what the briggs techs use at comp) ( find them here http://www.tinytach.com/tinytach/gasoline.php) connect it up and run the car and use a digital camera to take pictures as the car is driving.  As the engine is shifting it will be @ the engagement RPM. To adjust this rpm, you need to modify the CVT weights. This is where weight in the CVT is so important.  The heavier the main pulley weights are the lower your engagement rpm will be because there will be a higher centrifugal force to push in the pulley at an earlier rpm. If RPM is too high then weight must be increased.



- Side note, this ( CVT Weight tuning)  is very hard to do, and is one of the black arts in Baja SAE CVT design. 

Picture of kittens to break up boredom of this reply, sheesh !

AWWwww !!!



- Ok now, phew, last question.

Yes i do advocate the use of an overdrive.  As I previously mentioned the CVT I ran had a ratio of 3.0:1
for low and 0.43:1 for high.  0.43:1 is a pretty high overdrive almost 2:1.  Now going to get technical for a bit but the shift range for this CVT is 6.97.  That's really high. 

So since you are quoting it I'm assuming you've read my other long post about my CVTech CVT vs. a hypothetical CVT proposed by another user.

So yeah as you can see you have a situation where you reach your engagement rpm of engine at a lower vehicle speed.  This means that your car will be at full power quicker, which will lead to faster acceleration.   The key to this all is that the Briggs Intek 20 produces more power at higher rpms.  There is nothing to be gained by being at a lower rpm, the motor produces less power. 

Ok so see the post and if you have questions please let me know, I still find it pretty cool

Anyways though I would like to take it step further, In the Aaens hand book the author discourages the use of an overdrive saying that they are not good for CVT's.  It is important to remember the application that Aaens is writing about, snowmobiles are running at rpms of about 10K for their engagement rpms.  If you had a cvt that was a 0.5:1 overdrive, it would mean that you would need to turn 20K rpms into a gearbox.  The friction loads and heat loads would increase exponentially and this would be no good for a snowmobile

Fortunately Baja engines run much lower, only 3400 at full tilt.  So a 0.5:1 overdrive means that you are at max having 6800 rpms on your main gearbox entry.  This does cause a loss in efficiency, but this full overdrive only comes in at full tilt and this is the time when a loss in efficiency is ok! why because you are only to be going for top speed for a short part of the course, after you finish that straight away and need to climb a large hill, you will be glad you kept the torque a lower speeds by pushing down your lower ratio. 

Ok so I.M. I hope that answers your questions, if not please let me know, trying to help out teams is what veteran members like me can do to give back to the community.

Later,
Adam



Edited by jhu42 - May/03/2011 at 11:25pm
Adam Baumgartner
Social Media Director, #BajaMaryland
Test Driver, Honda R&D Americas Inc
Hopkins Baja, '07-'10
Back to Top
Akron 1998 to 2004 View Drop Down
Welding Master
Welding Master
Avatar
Thread Hijack Champion

Joined: Jan/20/2011
Location: WA
Status: Offline
Points: 327
Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: May/03/2011 at 11:27am
Originally posted by Invincible mechanics Invincible mechanics wrote:

I am new to the topic CVT and working on it to use it in BAJA. I am reading Olav Aaens handbook but i have some doubts related to your writing. First of all i want to know what this line of yours mean( the speed you will be at when your CVT engages is 7.79 mph.). Does this line means that CVT engages with the engine when our vehicle has some speed. If it is so then how our vehicle start moving. Also how we can calculate the engagement speed. And from my point of view the conclusion according to you is that if we have an overdrive we will have more acceleration. Is it right. Please help.

I can't think of a transmission that doesn't slip when a car starts from a dead stop.

Calculating the full engagement point wasn't really a priority.

 

A CVT is most efficient when its ratio is approximately 1 to 1.  A CVT with overdrive has a bigger range near the max efficiency point. 



Edited by Akron 1998 to 2004 - May/03/2011 at 11:31am
Back to Top
p.lewis View Drop Down
Welding Master
Welding Master
Avatar

Joined: Oct/05/2009
Location: Greater Detroit
Status: Offline
Points: 296
Post Options Post Options   Thanks (0) Thanks(0)   Quote p.lewis Quote  Post ReplyReply Direct Link To This Post Posted: May/03/2011 at 12:41pm
To use Aaen's terminology, "engagement speed" is where the CVT starts grabbing with some slippage to begin accelerating the car  (like feathering the clutch on a manual transmission) and "shift speed" is the point where the sheaves start moving to control engine speed to the optimum.
 
Engagement speed is generally set with the preload on the primary's spring. Shift speed is set with the spring and weight combination in the primary. On the Polaris CVT you can grind the flywheel cam profile to make a detent to control engagement speed (explained by Aaen), but there is no way to do this on the CVTech CVT and maybe not on the Comet CVT either.
University of Rochester Alum
Back to Top
schooter View Drop Down
Organizer
Organizer
Avatar

Joined: Feb/22/2010
Status: Offline
Points: 224
Post Options Post Options   Thanks (0) Thanks(0)   Quote schooter Quote  Post ReplyReply Direct Link To This Post Posted: May/03/2011 at 7:36pm
To quote the book theory of ground vehicles. During the initial engagement period when a clutch is slipping, whether it's a CVT or manual clutch you can assume max torque is being delivered. This is an ideal situation meaning that you have the CVT so it engages at max torque which in the weird world of SAE Baja is around 2500 rpm. Like others have already said though. Calculating engagement speed is very involved and unless you have someone dedicating allot of time to modeling and testing don't even try to calculate it. Hopefully the manufacturer of your CVT provided you with some reference material that give you a table of different springs and where they engage at.

Edited by schooter - May/03/2011 at 7:38pm
Chase Schuette
https://www.linkedin.com/in/chaseschuette/
Back to Top
Kumar Kislay View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Apr/22/2012
Location: Ranchi, India
Status: Offline
Points: 2
Post Options Post Options   Thanks (0) Thanks(0)   Quote Kumar Kislay Quote  Post ReplyReply Direct Link To This Post Posted: May/04/2012 at 11:48am
I am a first timer at BAJA SAE INDIA. My team has decided to go with CVT. But choice for CVT is becoming a problem. The choices i have in mind are Polaris and CVTech. Since a briggs and stratonn 10 hp engine is being used i need to find a compatible CVT. Kindly help me by pointing out the pros and cons of using above brands. Also a little help on compatible gearboxes will be very helpful.
 
mod note: merged from another thread


Edited by Mod Squad - Apr/25/2013 at 11:44am
Back to Top
jeiB View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Jul/17/2009
Location: Montreal
Status: Offline
Points: 604
Post Options Post Options   Thanks (0) Thanks(0)   Quote jeiB Quote  Post ReplyReply Direct Link To This Post Posted: May/04/2012 at 12:10pm
Do some searching/reading before you post please! We like to help but personally, I hate to repeat things that have already been said Smile

http://forums.bajasae.net/forum/cvt-selection-for-indian-engine_topic718.html
http://forums.bajasae.net/forum/preferred-cvt_topic140.html
Jeremie B.
McGill Baja Racing
2009-2011 Captain
minibaja.mcgill.ca
Back to Top
Kumar Kislay View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Apr/22/2012
Location: Ranchi, India
Status: Offline
Points: 2
Post Options Post Options   Thanks (0) Thanks(0)   Quote Kumar Kislay Quote  Post ReplyReply Direct Link To This Post Posted: May/04/2012 at 12:23pm
I am considering using a polaris CVT. But the problem arising is that polaris wont disclose the gear ratios for its trans-axle and according to our calculation estimate we need a max gear reduction of 40-45 for the hill climb test where a 45 degree incline will be present. If you have any idea of polaris CVTs and their compatible gearbox , please let me know :)
Back to Top
jeiB View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Jul/17/2009
Location: Montreal
Status: Offline
Points: 604
Post Options Post Options   Thanks (0) Thanks(0)   Quote jeiB Quote  Post ReplyReply Direct Link To This Post Posted: May/04/2012 at 12:30pm
http://www.polarissuppliers.com/sae_team/faq.htm

"· What is the overall ratio of the P90 clutch?
· The ratio starts near a 3.83:1 underdrive and will top out near a 0.76:1 overdrive."


Remember that you have to make modifications to the Polaris driver to fit on the Briggs engine.

· How should we mount the P90 clutch to our engine?
· I would recommend boring the clutch to the correct diameter and depth (1” dia X approx. 3.75” depth) and then broaching the ¼” keyway. The 1” bore will not clean up the entire original taper, but if you hold the diameter tightly, you will have plenty to pilot on. I like this method better than making an adapter or modifying the crankshaft.
Jeremie B.
McGill Baja Racing
2009-2011 Captain
minibaja.mcgill.ca
Back to Top
Ayrton-de-Pegasus View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Apr/25/2013
Location: INDIA
Status: Offline
Points: 2
Post Options Post Options   Thanks (0) Thanks(0)   Quote Ayrton-de-Pegasus Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2013 at 7:58am
hello everyone,
i am a BAJA enthusiast, and am doing Baja for the first time.
could you please help me out to select a good CVT??Smile
 
mod note: merged to this thread. post originally placed in a competition subforum


Edited by Mod Squad - Apr/25/2013 at 11:43am
Back to Top
collinskl1 View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Jan/21/2009
Location: Saginaw, MI
Status: Offline
Points: 1056
Post Options Post Options   Thanks (0) Thanks(0)   Quote collinskl1 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2013 at 8:10am
No.

This is a dumb question and  you are in the WRONG SECTION!
Kyle Collins
Lipscomb University Alumni
2x Project Manager

Nexteer Automotive
Product Engineer, Electronic Power Steering

... and the 8th simple machine: a bigger hammer.
Back to Top
Ayrton-de-Pegasus View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Apr/25/2013
Location: INDIA
Status: Offline
Points: 2
Post Options Post Options   Thanks (0) Thanks(0)   Quote Ayrton-de-Pegasus Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2013 at 8:16am
Yeah, for the greats in this filed, like you, will find this question dumb, and i am really sorry, that my question is  dumb towards you.
but for a first-timer like me and my team, even selecting a bolt and the required dimension is a big thing. and we are here to learn.
please guide us.
and here in india we dont have any FNR options.
so we are planning to import one.
and to import, whatever money we are gonna need is from our own pocket.
so please guide us...
Flying Horse...!
Back to Top
Soccerdan7 View Drop Down
Organizer
Organizer
Avatar

Joined: Sep/22/2010
Location: CA
Status: Offline
Points: 780
Post Options Post Options   Thanks (0) Thanks(0)   Quote Soccerdan7 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2013 at 10:37am
No it is a dumb question. It all depends on what you want, what you can tune, what ratios you need, etc.

The commonly used ones are:

CVTech
Polaris (P90?)
Comet (I don't know the model)
Gaged Engineering GX7 or GX9
Team Industries
Polar

Do some research and come back when you have an intelligent, specific question to ask.

Danny

Cornell

(fall'07 - spring'12)
Former Captain / MEng / that guy with all the carbon
10 races, 7 top ten's, 2 overall wins
Back to Top
cujdubs View Drop Down
Welding Master
Welding Master


Joined: Sep/25/2012
Location: Potsdam
Status: Offline
Points: 116
Post Options Post Options   Thanks (0) Thanks(0)   Quote cujdubs Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2013 at 10:52am
The first thing you should do is search the forum for other threads about clutch selection. There are many and they will provide you with some good places to start
John Hannum
Clarkson University
Steering Leader
Back to Top
Akron 1998 to 2004 View Drop Down
Welding Master
Welding Master
Avatar
Thread Hijack Champion

Joined: Jan/20/2011
Location: WA
Status: Offline
Points: 327
Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/25/2013 at 1:05pm
Originally posted by Ayrton-de-Pegasus Ayrton-de-Pegasus wrote:

whatever money we are gonna need is from our own pocket.
so please guide us...
 
CVTech has a SAE Baja sponsorship program with a CVT gear specifically for the competition at a cheap price. Like $200.  I have no experience with it.
 
Comet Model 790 (Low 3.38 High 0.54) is my Preferred CVT. About $700.  
Comet Model 780 (Low 3.71 High 0.69)
Comet Model 770 (Low 3.95 High .76)
Get it from QDS  P.O.  BOX 6910 , ALHAMBRA , CALIFORNIA  91802 TEL. ( 626 ) 293-5770 
They also sell F-N-R and other stuff to SAE Baja at discount.
Back to Top
Manlone View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Apr/19/2013
Location: Canada
Status: Offline
Points: 5
Post Options Post Options   Thanks (0) Thanks(0)   Quote Manlone Quote  Post ReplyReply Direct Link To This Post Posted: May/06/2013 at 2:47pm
Guys I have got an old CVTech CVT from my garage. I think my seniors used that. Me and my current teammates do not know the model and the specifications of the CVT like centre to centre distance, low and high ratio. I am attaching some photos of the CVT, can anybody tell me something about it?

Back to Top
Nick914 View Drop Down
Organizer
Organizer


Joined: Jun/16/2010
Location: U Laval
Status: Offline
Points: 256
Post Options Post Options   Thanks (0) Thanks(0)   Quote Nick914 Quote  Post ReplyReply Direct Link To This Post Posted: May/06/2013 at 3:15pm
This is the model currently offered to students
Info is in the form available below:


Nicholas Lefebvre

Universite Laval
Back to Top
Manlone View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Apr/19/2013
Location: Canada
Status: Offline
Points: 5
Post Options Post Options   Thanks (0) Thanks(0)   Quote Manlone Quote  Post ReplyReply Direct Link To This Post Posted: May/07/2013 at 9:33am
Thanks bro  Big smileBig smile
Back to Top
TaLampe77 View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Sep/10/2012
Location: Wichita KS
Status: Offline
Points: 1
Post Options Post Options   Thanks (0) Thanks(0)   Quote TaLampe77 Quote  Post ReplyReply Direct Link To This Post Posted: May/07/2013 at 3:19pm
Originally posted by jeiB jeiB wrote:

So apparently they are a lot of jr dragster cvt that I didnt know about !

  1. Shockwave clutchs by jr race car (http://www.jrracecar.com/pages.asp?pid=5)
  2. Polar ATAC (http://www.polarracing.com/catalogue/index.html)
  3. Supreme Tool clutch (http://supremetoolinc.com/cart/junior-dragsters-c-22.html?zenid=4d1710aa137da8fe1daf2426984f052a)

Anymore?

Now my question is: Is it really worth it spending 1000$ for these?

Looking at the results from 2010 in

Carolina accel event







1

Universidade de Sao Paulo

4.675

comet

2

Universite Laval

4.709

cvtech

3

Centro Universitario Da FEI

4.718

cvtech/polaris hybrid

4

Instituto Maua de Tecnologia

4.734

comet

5

Tennessee Tech Univ

4.838

gaged

6

Ecole De Technologie Superieure

4.892

cvtech

7

Univ of Maryland - College Park

5.015

gaged/polar hybrid

8

LeTourneau Univ

5.022

?

9

Universidad De La Salle Bajio

5.033

?

10

Universite de Sherbrooke

5.093

cvtech





Washington accel event







1

Universite Laval

4.957

cvtech

2

Univ of Maryland - College Park

5.018

gaged/polar hybrid

3

Ecole De Technologie Superieure

5.048

cvtech

4

Univ of Wisconsin - Madison

5.099

gaged?

5

Univ of Maryland - Baltimore County

5.151

?

6

Wichita State Univ

5.192

Polaris/Team

7

South Dakota Sch of Mines & Tech

5.242

comet

8

North Carolina State Univ - Raleigh

5.263

gaged

9

Oregon State Univ

5.273

polaris

10

Univ of South Florida

5.282

gaged

 

Im not sure about some of the teams cvts. I can modify the post if someone knows.

 EDIT: updated list


EDIT: Updated List
Back to Top
ballast View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Sep/30/2012
Status: Offline
Points: 28
Post Options Post Options   Thanks (0) Thanks(0)   Quote ballast Quote  Post ReplyReply Direct Link To This Post Posted: May/15/2013 at 9:20am
We have been using CVTech CVT procured through scholarship program for the last two years and managed to get decent results. Now i am eyeing on the CVTech models that does not come under scholarship. But the problem is choice. There are like 4 driver and 4 driven pulleys. I have a problem in deciding which combination would actually work. Guys, if anyone has experience in using unconventional CVTechs please share your knowledge, because the CVTech guy is not really helping. I want to know if trying them is even a worthy attempt or should i just stick to the basic model.
jacking with the screw
Back to Top
Nick914 View Drop Down
Organizer
Organizer


Joined: Jun/16/2010
Location: U Laval
Status: Offline
Points: 256
Post Options Post Options   Thanks (0) Thanks(0)   Quote Nick914 Quote  Post ReplyReply Direct Link To This Post Posted: May/17/2013 at 3:53am
From what i know, the other models are way overbuilt for our use and much heavier too.
The driven are a lot bigger and give you less ratio than the one in the sponsorship.
Nicholas Lefebvre

Universite Laval
Back to Top
Rishabh View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Mar/21/2012
Status: Offline
Points: 30
Post Options Post Options   Thanks (0) Thanks(0)   Quote Rishabh Quote  Post ReplyReply Direct Link To This Post Posted: May/18/2013 at 4:42am
I have a CVTech's sponsored CVT. We tried our hands to tune it last year but didn't the desired results as expected.I have read the clutch tuning handbook plus the discussions in forums related to the CVT. Just wanted to know the parameters of the CVTech's CVT that I can play with. Weights, pressure springs are the two which I can identify at present.We have 3 pressure springs and 1 set of weights which we got from CVTech. I think the CVTech doesn't offer weights and springs of different ranges which other brands do(polaris,comet).So is it advisable to make our own weights of similar profile as stock weights. Do baja teams do that ??I just need an insight to get things started.   



Edited by Rishabh - May/18/2013 at 4:45am
Back to Top
ballast View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Sep/30/2012
Status: Offline
Points: 28
Post Options Post Options   Thanks (0) Thanks(0)   Quote ballast Quote  Post ReplyReply Direct Link To This Post Posted: May/19/2013 at 2:03am
what will be the effect if the CVT c-c distance falls short of what is specified by the manufacturer i.e., if the specified c-c distance of a belt is 242mm but while assembling, you get only like say 235mm, what would be the effect on performance. Also is it possible to shift a FNR while CVT is idling, without using a friction clutch like in manuals??
jacking with the screw
Back to Top
Soccerdan7 View Drop Down
Organizer
Organizer
Avatar

Joined: Sep/22/2010
Location: CA
Status: Offline
Points: 780
Post Options Post Options   Thanks (0) Thanks(0)   Quote Soccerdan7 Quote  Post ReplyReply Direct Link To This Post Posted: May/19/2013 at 11:18am
Originally posted by ballast ballast wrote:

what will be the effect if the CVT c-c distance falls short of what is specified by the manufacturer i.e., if the specified c-c distance of a belt is 242mm but while assembling, you get only like say 235mm, what would be the effect on performance.


This would be very bad. Center-center distance is something you want to be able to precisely set and maintain, and you want to be slightly over the manufacturer's number rather than be under.

For the 242 mm example, I would saw you want to be in the 242-245mm range. There is a thread on here somewhere that discusses the effect of c-c distance specifically.
Danny

Cornell

(fall'07 - spring'12)
Former Captain / MEng / that guy with all the carbon
10 races, 7 top ten's, 2 overall wins
Back to Top
ballast View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Sep/30/2012
Status: Offline
Points: 28
Post Options Post Options   Thanks (0) Thanks(0)   Quote ballast Quote  Post ReplyReply Direct Link To This Post Posted: May/19/2013 at 3:15pm
Originally posted by Soccerdan7 Soccerdan7 wrote:

and you want to be slightly over the manufacturer's number rather than be under.

For the 242 mm example, I would saw you want to be in the 242-245mm range
Just curious to know why you'd prefer to be slightly over than the mfr specified c-c than be under it. Wont it put some extra tension on the belt and affect idling behavior of the vehicle.

Btw i went through the other threads regarding c-c distance but did not get what i was looking for.But thanks anyway dude..Tongue
jacking with the screw
Back to Top
Soccerdan7 View Drop Down
Organizer
Organizer
Avatar

Joined: Sep/22/2010
Location: CA
Status: Offline
Points: 780
Post Options Post Options   Thanks (0) Thanks(0)   Quote Soccerdan7 Quote  Post ReplyReply Direct Link To This Post Posted: May/19/2013 at 3:28pm
Yes, it will effect the idle behavior, but we found it very difficult to get anywhere near the full shift out running it per the manufacturer's spec. I can only imagine that running it substantially closer would enhance this problem and also delay shift out behavior and lengthen the amount of time the belt is slipping.

We ran the CVTech with minimal mods in 2009 in this way and had a very fast car... the only drawbacks were additional heat in the casing and belts wanting to wear out faster. Ever since then the Cornell team has not run a very close to stock setup, so comparisons are difficult.
Danny

Cornell

(fall'07 - spring'12)
Former Captain / MEng / that guy with all the carbon
10 races, 7 top ten's, 2 overall wins
Back to Top
Rishabh View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Mar/21/2012
Status: Offline
Points: 30
Post Options Post Options   Thanks (0) Thanks(0)   Quote Rishabh Quote  Post ReplyReply Direct Link To This Post Posted: May/20/2013 at 8:03am
We did shift the FNR while CVT was idling, and we didn't have friction clutches. The engagement was not smooth but it worked for about two months, Right before the event the we had engagement problems of the reverse,we corrected it but during the maneuverability event we had to engage the reverse gear a lot of times during turns( steering design was not proper,high turning radius). Eventually we couldn't run the endurance, the shifting mechanism completely failed.The engagement of reverse without the clutch puts extra load on the shifting mechanism which leads to failure of the components.
One solution is to shift the below the engagement speed of the CVT that is when the belt is not transmitting torque. I haven't checked it's practical feasibility plus the members mention it's difficult to calculate the engagement speed considering all the parameters. CVTECH sponsored CVT which we use gives the engagement loads of drive pulleys.So that information might help us next time. Friction clutches have no reliability issues for sure and worked fine 2 years back in the event.
   


Back to Top
njgedr View Drop Down
Welding Master
Welding Master
Avatar

Joined: Oct/05/2010
Location: Ortonville MI
Status: Offline
Points: 194
Post Options Post Options   Thanks (0) Thanks(0)   Quote njgedr Quote  Post ReplyReply Direct Link To This Post Posted: May/20/2013 at 9:06am
The biggest issue with running the wrong CC Distance is not reaching the high and low capabilities of the CVT. If your CC distance is short. The Primary wont grab until it is shifted farther in, taking away from your low ratio. Also, when the primary is fully shifted in, you will not be shifted fully out on your secondary, taking away from your High Ratio. 

The same issues are true with a CC distance that is too long just opposite, 
Low: The Secondary will be partially shifted out at Idle.
High: The Primary cant shift Fully in because the secondary is all the way open

I recommend using an Aluminum plate mounted to the mounting bolts around the output of the briggs, and the input of your transmission, to maintain good CC tolerances, and alignment. 

Rowan Baja 2009-2012
Auburn 09
Peoria 11
Epreuve Du Norde 12
Auburn 12
Wisconsin 12

Mubea Development Engineer
Back to Top
MelkMan View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: May/22/2013
Status: Offline
Points: 1
Post Options Post Options   Thanks (0) Thanks(0)   Quote MelkMan Quote  Post ReplyReply Direct Link To This Post Posted: May/22/2013 at 11:43am
Hi guys

I would just like to know if anyone has a reliability rating for the whole CVT system? Specifically the Polaris P-90 , but any other will do. So eg. 90% reliability etc

Thanks in advance

Back to Top
DrewT View Drop Down
Milling Master
Milling Master
Avatar

Joined: Oct/16/2009
Location: Bellingham, WA
Status: Offline
Points: 102
Post Options Post Options   Thanks (0) Thanks(0)   Quote DrewT Quote  Post ReplyReply Direct Link To This Post Posted: May/23/2013 at 6:00am
We always ordered the Comet 790 series from QDS that was already tuned for a briggs and stratton.  I'm not sure if QDS even offers the comet anymore, I had heard comet went out of buisness, but at the time it was the hot ticket for teams that wanted an out of the box setup that worked well.  One year we put a lot of effort into tuning it and trying different combinations of weights, ramps, springs, belts, c-c distances, and pulley offsets.  We validated the tests with both timed acceleration runs and some pulls on the rolling road dyno (the dyno didn't give very realistic numbers for our low-power application, but it did give a very good indication of relative performance compared with the other setups we tried, and you could get right up to the cvt as it was working to see how it shifted).  What we found was that QDS had already done a very good job setting up the comet for Baja SAE.  We ended up going down one spring rate on the secondary and leaving the primary stock for the best results.
 
The downside to the Comet was always heat.  We burned up belts fast, and sometimes melted all the plastic friction pads out of the secondary ramps.  In Peoria in 08, we changed 2 or 3 belts during endurance and finished 2nd (before being disqualified in post race tech).  In Oregon in 09, we changed 4 belts during endurance, melted the plastic friction pads in the secondary, and even heated up the secondary snap ring so hot it popped out of the groove and let the secondary back sheave grind into our gearbox.  In Washington in 2010, we adjusted the c-c distance and pulley offsets and introduced better air circulation to the cvt cover to alleviate the heat problem somewhat, but gave up initial performance to do it; we ran the entire endurance on one belt and finished 8th, but we still melted the plastic pads on the secondary ramps by the end.
WWU Baja SAE team captain 2009-10
NC Process Engineer - Janicki Industries
Back to Top
ballast View Drop Down
Bolt Sorter
Bolt Sorter
Avatar

Joined: Sep/30/2012
Status: Offline
Points: 28
Post Options Post Options   Thanks (0) Thanks(0)   Quote ballast Quote  Post ReplyReply Direct Link To This Post Posted: May/23/2013 at 12:20pm
QDS still offers comet CVT at a discounted price for universities.  call Roy at QDS and ask him for a catalogue. mails usually attract a very long response time. I prefer phone calls.
jacking with the screw
Back to Top
Akron 1998 to 2004 View Drop Down
Welding Master
Welding Master
Avatar
Thread Hijack Champion

Joined: Jan/20/2011
Location: WA
Status: Offline
Points: 327
Post Options Post Options   Thanks (0) Thanks(0)   Quote Akron 1998 to 2004 Quote  Post ReplyReply Direct Link To This Post Posted: May/23/2013 at 3:22pm
Originally posted by DrewT DrewT wrote:

The downside to the Comet was always heat.  We burned up belts fast, and sometimes melted all the plastic friction pads out of the secondary ramps.  In Peoria in 08, we changed 2 or 3 belts during endurance and finished 2nd (before being disqualified in post race tech).  In Oregon in 09, we changed 4 belts during endurance, melted the plastic friction pads in the secondary, and even heated up the secondary snap ring so hot it popped out of the groove and let the secondary back sheave grind into our gearbox.
 
I've been running the same Comet 790 for 13 years, I only changed the belt because it looked dirty and I had a new one.  You probably needed to increase (not decrease) the spring tension on the secondary to prevent belt slip and possibly a different gear ratio. 
 
When you get your car running we can race at Walker Valley
Back to Top
JeremyB View Drop Down
Organizer
Organizer
Avatar
Last one standing

Joined: Oct/13/2008
Location: Huntsville, AL
Status: Offline
Points: 135
Post Options Post Options   Thanks (0) Thanks(0)   Quote JeremyB Quote  Post ReplyReply Direct Link To This Post Posted: Jun/24/2013 at 2:59pm
FWIW, I'll throw out an updated nugget. Top ten endurance cars @2013 RIT
 
1 - Custom
1 - IBC
1 - Comet
6 - Gaged
 
There's only 9 because I can't remember the 10th!
Back to Top
Mohit Saini View Drop Down
Bolt Sorter
Bolt Sorter


Joined: Jun/12/2013
Location: Ambala
Status: Offline
Points: 3
Post Options Post Options   Thanks (0) Thanks(0)   Quote Mohit Saini Quote  Post ReplyReply Direct Link To This Post Posted: Jun/26/2013 at 10:20pm
sir, thanx for responce. but not i am asking about cvt's not about time measuring accesories

Mohit saini
Back to Top
Pedro UFPBaja View Drop Down
Baja Godfather
Baja Godfather
Avatar

Joined: Mar/03/2010
Location: Brazil
Status: Offline
Points: 886
Post Options Post Options   Thanks (0) Thanks(0)   Quote Pedro UFPBaja Quote  Post ReplyReply Direct Link To This Post Posted: Jun/26/2013 at 11:39pm
...


Edited by Pedro UFPBaja - Apr/03/2015 at 1:29pm
Former Team Captain
Back to Top
 Post Reply Post Reply Page  <1234>
  Share Topic   

Forum Jump Forum Permissions View Drop Down



This page was generated in 0.109 seconds.