What are Continuously Variable Transmissions CVTs : Autos -- Car Tires and Maintenance  -- Cars Discussion Forum and Review What are Continuously Variable Transmissions CVTs : Autos -- Car Tires and Maintenance -- Cars Discussion Forum

  parts   |   manuals   |   discussion   |   photos   |   podcast   |   reviews   |   specs   |   dealers   |   classifieds   |   contact   |   faq   |   myProfile   |   home          Login Now | Sign Up


FAQ:   What is a tractor?

Forum Index
New As Posted | Active Subjects



www.emerichsales.com - New & Used Equipment
          View Tractors For Sale!


www.partsbynet.com - Lawn and Garden Equipment Parts


Bernardsville Landscape Lighting
Click to Post a New Message!

Discussion Boards > Active Subjects > Messages as Posted > Autos -- Car Tires and Maintenance Forum

Page [ 1 ] |
Reply | Pop Up Window Reply | Add PhotoAdd Photo
 06-18-2009, 11:55 Post: 163490
kwschumm



View my Photos

View my Photos  Pics
Join Date: Feb 2003
Location: NW Oregon
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster
Posts: 5764

2
Filter by User
 What are Continuously Variable Transmissions (CVTs)

My mental picture of a CVT involved a belt driving two piece conical shaped pulleys. The variable ratios were controlled by moving the two pulley halves closer or further apart.

Early CVTs seemed to be used only on the smallest of low powered cars.

Now they are becoming more common and I was astounded to hear that they are being used on heavy equipment. Furthermore, someone here mentioned that JD had a CVT design that was essentially a gear based transmission.

I'd sure like to understand how a gear based CVT would work. You can't vary the teeth on a gear. You can vary the number of gears but you can't have an infinite number of them and it seems they could never be continuously variable in the true sense of the term.

What was the big breakthrough design that allowed CVTs to become more successful?






Reply to PostReply | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo




Bookmarks: Digg It | Del.icio.us | Technorati | Furl | Stumble This

 06-18-2009, 17:04 Post: 163493
auerbach



View my Photos

View my Photos  Pics
Join Date: Sep 2007
Location: West of Toronto
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster
Posts: 2168
 What are Continuously Variable Transmissions (CVTs)

I don't know but they've come a way since the DAF. There are now eight different types being used in cars, including some bigger and heavier brands -- all outlined in Wiki.






Reply to PostReply | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo




Bookmarks: Digg It | Del.icio.us | Technorati | Furl | Stumble This

 06-18-2009, 20:17 Post: 163495
hardwood

TP Contributor

Join Date: Dec 2002
Location: iowa
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster
Posts: 3582

2
Filter by User
 What are Continuously Variable Transmissions (CVTs)

The CVT design I'm familliar with all goes back to Henry Ford's planetary gear design with a few modifications.
OK, picture in your mind the common planetary gear arangement.

Sun gear in the center.

Planet gears in mesh with teeth on the sun gear and in mesh with teeth on the inside of the ring gear.

Ok, now if the ring gear is held in a fixed position and the sun gear is spinning in the center at a given RPM, the power is being sent out thru a bracket and shaft holding the planet gears in place. The
RPM of the output shaft connected to the planet gears will be less. The "RATIO" of input shaft to output shaft determined by how many teeth are on the sun, planet and ring gears.

Now same design as I described above only now what happens if the ring gear is not held in a fixed position while the gearset is running and can be spun in either direction at varying speeds by means of teeth on the outside of the ring gear? You are varying the ratio of the gearset while in use = CVT. The ring gear is being spun in either direction at varying speeds by a hydraulic motor to get the travel speed, (RATIO), you want.

OK, put two or three of the systems I described in series sending power from the first to second to maybe even a third gearset with the variable speed ring gear, pretty simple basic design.

Some may argue that the hydraulic motors are transmitting some of the power, perhaps they are but it would be minimal compared to the power being transfered thru the gearsets.

Clear as mud. Frank.






Reply to PostReply | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo




Bookmarks: Digg It | Del.icio.us | Technorati | Furl | Stumble This

 06-18-2009, 21:50 Post: 163497
kwschumm



View my Photos

View my Photos  Pics
Join Date: Feb 2003
Location: NW Oregon
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster
Posts: 5764

2
Filter by User
 What are Continuously Variable Transmissions (CVTs)

Thanks Frank, that makes sense. It's sort of funny, shortly after posting this Subaru's latest newsletter arrived in my inbox. With their 2010 models they are rolling out CVTs on some of their models. It seems to have increased highway mileage by 15% or so over previous models. They included a link to a video and it shows the design that I was familiar with, two two-piece conical pulleys with a belt. There's something about that design I just don't trust.






Reply to PostReply | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo




Bookmarks: Digg It | Del.icio.us | Technorati | Furl | Stumble This

 06-19-2009, 07:39 Post: 163500
hardwood

TP Contributor

Join Date: Dec 2002
Location: iowa
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster
Posts: 3582

2
Filter by User
 What are Continuously Variable Transmissions (CVTs)

KW, before hydros came along combines used the variable speed belt design you describe. WE never had much trouble with them, but more maintenece was involved than hydros.






Reply to PostReply | Quote Post Reply to PostQuote Reply | Add PhotoAdd Photo




Bookmarks: Digg It | Del.icio.us | Technorati | Furl | Stumble This

Reply | Pop Up Window Reply | Add PhotoAdd Photo


Page [ 1 ] |

Discussion Boards > Active Subjects > Messages as Posted > Autos -- Car Tires and Maintenance Forum

Thread 163490 Filter by Poster:
auerbach 1 | hardwood 2 | kwschumm 2 |




Most Viewed

+ Torque Specifications for most Makes and Models
+ Extended warranties on cars and trucks
+ Car Fuel Economy and the 55 MPH speed limit
+ Winter Tires for 4WD SUV
+ What are your favorite SUV Tires
+ 2000 Dodge Intrepid Disc Brake Drag
+ Tanners Preserve Review leather cleaner and condit
+ TIRED OF TIRES
+ CVT Automatic Transmission Review
+ welding on newer cars

Most Discussion

+ Torque Specifications for most
+ Car Fuel Economy and the 55 MP
+ Winter Tires for 4WD SUV
+ What are your favorite SUV Tir
+ Extended warranties on cars an
+ TIRED OF TIRES
+ welding on newer cars
+ 2000 Dodge Intrepid Disc Brake
+ CVT Automatic Transmission Rev
+ What are Continuously Variable

Newest Topics

+ Winter Tires for 4WD SUV
+ What are your favorite SUV Tires
+ CVT Automatic Transmission Review
+ 2000 Dodge Intrepid Disc Brake Drag
+ Car Fuel Economy and the 55 MPH speed limit
+ Tar on the Trailblazer
+ What are Continuously Variable Transmissions (CVTs
+ Car Buying Opportunity
+ welding on newer cars
+ Torque Specifications for most Makes and Models













Turbochargers for Tractors and Industrial Machines
Cab Glass for Tractors and Industrial Machines

Alternators for Tractors and Industrial Machines
Radiators for Tractors and Industrial Machines

Driveline Components for Tractors and Industrial Machines
Starter Motors for Tractors and Industrial Machines