OS3 TFX “Modified” Class Rules

The spirit of OS3 TFX “Modified” class rules are intended to permit modifications to the “stock” TFX platform that may allow it to compete with slightly restricted ECHORR or Fray-style T-Jet platforms at Stewart Raceway.

PLEASE NOTE: Dash motor magnets and/or non-commercially available components are not allowed for use in T-Jet racing at Stewart Raceway. Red Text indicates latest changes.

The allowed modifications to the OS3 TFX “Modified” car are as follows:

  1. The width of a fully assembled tire/wheel/axle assembly shall not exceed 1-5/16 (1.3125) inches.
  2. Only OS3 Grey or Black Dragon motor magnets are allowed. Magnets must be OEM painted and clearly identifiable.
  3. Spacing between magnets shall be no less than .700.
  4. Magnet shims may be used as long as they are made of non-ferrous material. No shims are allowed either under or on top of the magnets.
  5. Any flat top and bottom carbon/copper motor brushes are allowed. Brushes may be scored with one score line or an X. Brush Tensioners may be slightly “dimpled” to prevent brush spinning. No exaggerated deep cuts or crevices are allowed.
  6. Only original Aurora 2 Lam T-Jet pancake gray armatures, Dash Motorsports 3 Lam armatures, or OS3  Tornado/Typhoon armatures may be used. The arms must be used with their original commutator and all of their original unmodified windings. Armatures may be balanced and trued.  A shim may be used between the armature and the top plate to prevent the motor windings from contacting the top plate.
  7. Each armature pole is to be measured across two separate commutator segments. The AVERAGE of all three poles must be 16.0 ohms or greater at 70 degrees. This armature is LEGAL. All measurements are to be taken at the current available room (ambient) air temperature. The warming of either the commutator or the armature is not allowed before/during the measuring. (The combined total ohm reading of all three armature poles must equal or exceed 48 ohms.)
  8. Only commercially available front wheel, tire, and axle assemblies may be used, with two exceptions. The front and rear axle diameter must not exceed .065″ and the front tire diameter must equal or exceed .300″. Front axle washers (small spacers) are allowed. All front axle spacers/washers must be located outside the chassis or chassis frame rail. Maximum lateral movement in the front wheel assembly is 0.031 (1/32).  Any unmodified commercially available front wheel, tire, and axles parts may be mixed and matched.
  9. Rear wheels must be plastic or Delrin with a dished center. No axle weights, wheel weights, or hub caps are allowed on the rear axle or inside the wheels. Note: A small Delrin retainer (ie. front wheel retainers) will be allowed on either side of the rear axle for the purpose of adjusting crown gear mesh with the 9T rear pinion. The diameter of the retainer must not exceed 0.125″ with a thickness not to exceed 0.0700″.
  10. Rear tires shall be commercially-available solid silicone, rubber, or urethane replacement tires. Rear wheels shall be commercially-available double or single flanged replacement wheels/hubs.
  11. Spacers may be used on the rear axle inside the chassis only.
  12. Any stock or approved replacement pickup shoe may be used. These shoes must have a factory-formed step and the step must be unaltered except to allow flat pickup shoe contact with the track rail. Ski shoes are not allowed.
  13. rules_clip_image004The “step” in the pickup shoe must remain at a minimum height of .010 from the top of bend #2 to the bottom of bend #3.  The first bend in the step, (Bend #2), may be changed slightly so that proper “pickup shoe” to “rail” contact can be achieved. No attempts to “flatten” the “step” are allowed. The area between Bend #1 and Bend #2 may be “flattened” to achieve better contact with the “rails”, however Bend #1 must remain as stock. The front vertical slotted portion of the pickup shoe may be bent to limit shoe travel. The rear hook portion of the pickup shoe may be bent to limit shoe travel and adjust shoe tension. The chassis’ copper pickup retainer may be bent slightly to improve electrical contact.
  14. Pick-up shoe springs may be cut, stretched, shimmed, or compressed but must maintain stock shape and configuration.
  15. The body must be painted and rear wings/spoilers may be added for aesthetics only. Overall height of the car and mounted body cannot exceed 3/4″ (.750″). This height will be measured with the body mounted on the car as it sits on the track.
  16. The body must cover the chassis, tires and wheels when viewing the car from above except through legal openings (i.e., windows, etc.). No body material removal is permitted except for wheel openings and track/rail clearance.  Open-wheel bodies are allowed in open-wheel events only, mixed open-wheel and full-body cars cannot race together.
  17. Bodies may be plastic, resin, or any thickness of Lexan-like material.
  18. Only OS3 adhesive-type removable body mounts are allowed.
  19. Any car without a body or with an interfering body will not be allowed to continue racing.
  20. Track voltage will be set at a minimum of 18.1 volts or a maximum of 20.1 volts for this class.
PLASE NOTE: These rules are an enumeration of what can be done.  Doing something not listed above as allowed is NOT allowed.