Ag Track Talk: Friction vs. Positive Drive

There are two types of agricultural track systems – friction and positive drive. Both have benefits and drawbacks, and manufacturers have created different designs of each. I asked four track manufacturers to explain the differences between the two types of track systems and their opinions of each. Here’s what they had to say.

CamsoDavid Graden, Operational Market Manager – Agriculture

The Friction Drive system is as it sounds. Typically, these are seen in pairs (as opposed to 4 tracks) on a machine. The tracks are elongated and put under tension and, of course, driven by friction. Additionally, the track curves 180 degrees around two wheels; the drive wheel at the rear and the idler wheel at the front.

The Positive Drive system is triangular shaped with two idler wheels at the bottom corners and a drive wheel, or sprocket, at the top. There is less tension on the belt, and it is technically pushed by the sprocket, whereas drive lugs on the underside of the track fit perfectly with the sprocket.

Trackman by LocDan Fullenkamp, Business Development Director

The Friction Drive and Positive Drive tracks have unique structural and functional differences that separate their strengths and weaknesses from each other.

Friction Drive Benefits

The friction drive system is a less complicated and more cost-effective design. Friction tracks incorporate “guide lugs” on the inner or wheel path side of the tracks to help ensure that the track maintains its position on the undercarriage system. The size of the guide lug differs from manufacturer to manufacturer. Trackman typically utilizes a greater number of guide lugs for increased efficiency, reduced stress, and longer life on these lugs as they transition around the drive and idler wheels of the friction drive system.

 Friction Drive Drawbacks

When friction is lacking, it is in muddy, frosty, or wet conditions, when the belt could slip. This is one of the most significant drawbacks of the otherwise reliable design of the friction drive.

Positive Drive Benefits

The drive wheel of a positive drive system engages with the track drive lugs, preventing track slippage from occurring. This can be a better option when working in a wet or slippery environment and is often utilized in higher horsepower equipment.

Positive Drive Drawbacks

The engagement precision required with this set up is more costly but more reliable.

Soucy TrackMarc McDonald, Territory Manager

Friction Drive

A friction drive belt, as implied by its name, is a track that is tensioned to smooth rubber wheels much like a conveyor belt. The tractive force generated for propulsion is the friction between the drive wheels and the roller path of the track.

Most friction drive machines are used for general agriculture whereas positive drive track machines are used where more tractive force is required.

Positive Drive

The positive drive track is primarily a friction drive belt (most of the time) with metal sprockets that are interlaced with rubber blocks. At the point the friction drive is overwhelmed, the sprocket catches the rubber blocks for a positive engagement without any noticeable difference.

Both Track Types

a. Are similar in construction.
b. Have an integrally wound main cable (zero cable) continuously from one side to the other, for strength.
c. Rubber outer drive lugs for traction.
d. Have a smooth roller path for the wheels to transfer weight of the machine to the ground.
e. Have differing layers of steel and synthetic fabrics for strength in different applications.

Difference

a. Friction drive tracks have guide blocks; positive drive tracks have drive blocks.

Friction Drive Benefits:

a. Fairly simple. Two guide wheels, two drive wheels, a track, and bogey wheels to support.
b. Typically have less problems with the undercarriage.
c. Last much longer as there isn’t as much adverse contact between the components.

Friction Drive Drawbacks:

a. Friction drive tracks (two tracks) are harder to ballast front to rear with cyclically loaded equipment.
b. Friction drive tracks lose much of their internal traction when moisture levels are too high (mud and/or water) resulting in difficulty maintaining forward direction or steering at times.

Positive Drive Benefits:

a. More torque to the ground in difficult or high traction situations.
b. Better control maintaining direction and turning in wetter conditions.

Positive Drive Drawbacks:

a. Much lower lifespan than friction drive.
b. Typically more problems with the undercarriage.
c. Drive lugs are the workhorse of this track. Damage to the drive lugs from alignment, material ingestion, or over pulling greatly diminishes life expectancy of the track.

Zuidberg Group of CompaniesReint Bannink, Manager Assembly, Coating & Rubber

The most important difference between the two types is the method of submitting power from the machine to the track and vice versa. In a positive drive system, the power is exchanged by a set of sprockets in a so-called sprocket-wheel. The sprockets pull the track ahead like a chain is pulled by the chainwheel. Doing so, a large amount of force is placed on the lugs with high torque on the track. The inner lugs, also called ‘drive lugs’ need to deal with these huge forces and power. The forces applied to the inner lugs are transferred into the carcass of the track. The enormous amount of energy needs to be adapted in such a way that the carcass remains stable and delivers the power to the outer lugs and into the soil for the required traction. In order to keep the track in place, and to avoid hopping of the track over the sprockets, some tension is given to the track with a small hydraulic cylinder in the track frame.

Where the positive drive track is driven by sprockets, the friction drive track is, as named, driven by friction by the wheel on the rear. To apply high friction, an extremely high tension in the track is demanded. This is applied by heavy hydraulic cylinders in the track frame. The tension in such a system is 10 to 15 times higher than in a positive drive system. The lugs on the inside of the track in a friction drive system are for guiding only- they do not have any influence on traction.

 All information is provided solely to provoke thought. All deductions made from provided information must be confirmed by Certified Ag Track Dealer before use. Ag Track Talk does not recommend anyone conduct track service work with exception of Certified Ag Track Dealer Professionals.