July 12, 2024

SS Rules

ECHORR SS Rules – effective 08/03/20


Complete Car Regulations:

The complete car must weigh at or between 19.0 grams and 24.0 grams.
The complete car must freely pass through a standard 1.3125 (1 and 5/16) HO tech block.


Body Regulations:

Body: The body must be a copy of a 1:1 car and concept cars.
Bodies must be manufactured by either the process of casting or injection molding and be made of resin or plastic. No feather-light resin allowed.Bodies must be originally manufactured with the intention of being mounted with the use of two (2) screws via two (2) body-mounting posts on a/an: Aurora Model Motoring (which includes: Vibrator, Thunder Jet, Wild Ones, Tough Ones and Xlerators), Bachmann, Faller, Model Motoring Thunder Plus, Marx, Eldon or Tyco S series HO chassis.

Bodies with cast-in handling pans or exaggerated details – such as unrealistic or inappropriate hood scoops, oversized windows, side pipes, sloped sides, or snow plow noses – are not allowed.

No Indy style Formula 1 or Formula style open-wheel bodies will be allowed.

No ballast or fillers, other than color pigment, are allowed in the plastic or resin.

Maximum overall body width is 1.200. Accordingly, the body must pass through our 1.2 body-tech device.  The maximum thickness of the lower portion of the sides of the body, including items such as fender flares, and running boards must not exceed 0.125.

With the body mounted securely to the chassis and viewed from above, the body must cover the chassis except through windows and vents. Unrealistic overly large windows and vents are not allowed.

With the body mounted securely to the rolling chassis and when viewed from the rear window opening, the upper edge of the top-plate, minus rails, cannot be above the top of the body as measured at the rear window opening.

Bodies must be fitted with all of the manufacturers original   or exact-replica bumpers, heads, rollover bars, etc. in their stock locations.

Cracked or broken body-mounting posts may be repaired or replaced with the use of glue and/or a plastic sleeve around the original post or a plastic rod/tube in place of the broken post.

Other than the plastic post reinforcements, stated in Body Rule 11, no additional weight may be added to the body.

The body may be lowered and lightened by removing material through the process of grinding or scraping as long as Body Rule 9 is not violated. Bodies cannot be heated or reshaped from the original cast of the body.

Bodies that have a separate roof and windshield casting/molding, and have molded-in interiors (also known as Hardtops, e.g. Aurora’s ’65 Mustang), may completely remove the interior portion of the body.

Front and rear wheel wells may be opened up for tire wheel well clearance. This opening may be no larger than a 1/8-inch drill bit (.125″) around the entire wheel well and tire.

Wheel wells must not be modified in such a way as to allow the use of any other wheelbase than that which was originally intended by the manufacturer of that body.

Any mounting screw may be used. Non-magnetic screws are recommended so that a loose screw will not be picked up by a passing car, thus causing damage to the car and/or the track.

Both front and rear screws must be used and must secure the body to the chassis except when body is broken a race, in which case a track call will be made and the team is allowed to replace it with a body already teched in the box and the race must be finished with existing chassis.

The front windshield must be plastic or resin, clear or painted, may be glued in place or molded in, and must fill the frame. Tape windshields are not allowed. Side and/or rear windows may be removed. Rear windshields are optional, but must adhere to this same rule if used. Windshields made form Testor’s Window maker are not allowed.

Any new bodies must be submitted to ECHORR at least 60 days before the ECHORR Challenge to be legal for the event. Bodies previously approved and no longer on market will be grandfathered in as approved, these include: Fandango, Moonstone, GoGo, BRP, Bubba Shells, etc. as long as they meet all of the other body requirements.

Thunder Jet Rolling Chassis Assembly Regulations:

Original Aurora Thunder Jet chassis assemblies with non-plated copper electrical components are allowed, including silver color solid rivets, after market rivets are  allowed. Commutator brush springs may be bent to alter brush tension. Pickup shoe hanger plates may be bent. Wizjet Chassis are allowed. Aurora top plates are permitted on Wizjet Chassis and Wizjet top plates are permitted on Aurora chassis. 

2. The rolling chassis axle, armature, and drive pinion shaft holes may be opened up slightly for increased clearance.

3.  The Truck hole cannot be utilized in any way.

4.  Chassis holes may be closed or opened for proper clearance, the rolling chassis assembly must not be fitted with bushings.

5. The chassis may be trimmed slightly (no more than .010) to allow for crown gear tooth clearance.

  1. Gear plate rails may be cut or sanded only for purposes of lowering the body, and shall only be cut or sanded to the level of the top surface of the gear plate. Rails must remain entirely under the gear plate clip.
  1. Brush springs may be adjusted only in their original configuration to change the tension on the brushes. They may be dimpled or a corner may be altered only to prevent the brush from spinning.
  1. Guide pins shall be original design, must use a full guide pin, guide pin hole may be countersunk for body screw. No metal guide pins.
  1. Guide pins may be glued to chassis.
  1. Guide pins may be shortened in length to accommodate different tracks.
  1. The gear plate clamp may be bent (but not cut or otherwise altered) to improve


  1. Squishing of the idler post is permitted.
  1. Cluster shafts can be made of any material. Bottom of cluster shaft may be cut.



  1.  Original Aurora T-Jet pancake gray armature with a maximum of two laminations, with its original Commutator, and all of its original unmodified windings may be used. Dash and OS3 – 3 lam arms 16+ ohms are allowed. The armature may be balanced and trued. The use of glue between comm gaps is allowed in this class. Shims between the armature and top plate are allowed.
  1. Each armature pole is to be measured across two separate Commutator segments. The AVERAGE of all three poles must be 16 ohms or greater. i.e.: Pole A measures @ 15.8 ohms, Pole B measures @ 16.2 ohms and Pole C measures @ 16.0 ohms 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 measuring. (The combined total ohm reading of all three armature poles must equal or exceed 48 ohms.
  1. 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 allowed; this will be checked for at tech.

No Hand Wound or rewound or de-wound armatures allowed. The tech committee will have privy to comparative arms and other hand wound detecting tools to make an intelligent decision on a case by case basis.

  1. Only stock T-Jet or commercially available stock replacement 14 tooth brass armature pinion gears are allowed.2. Only stock T-Jet or commercially available stock replacement 24 tooth brass idler and driven gears are allowed.3. Only stock T-Jet or commercially available stock replacement 9, 12 or 14 tooth brass drive-pinion gears are allowed.
  2. Only stock T-Jet or commercially available stock replacement 15 tooth crown gears are allowed. The crown gear boss may be trimmed; spacer(s) may be added to adjust for proper gear mesh within the crown gear box. You can add a small delrin retainer to either side of the rear axle for the purpose of adjusting crown gear mesh with the rear pinion. The diameter of the delrin retainer must not exceed 0.125″ with a thickness not to exceed 0.070″. 4 gear specialty chassis crown gears are not allowed.

4a. Minimum top plate gear thickness shall be .045.

  1. The Crown gear shall not be metal.

5a. The Crown gear minimum diameter will be no less than .300

5b. No Chamfering or beveling of the crown gear, must maintain 90 degree angle as originally produced.

  1. The crown gear “boss” may be sanded or trimmed to accommodate different gear ratios.
  1. The crown gear may be shimmed inside and/or outside the chassis.
  1. Gears may be soldered or glued to their respective shafts.
  2. Only metal driven-gear shafts may be used. The driven-gear shaft must not exceed .065″ in diameter and can be any material including titanium.10. Gear-tooth friction surfaces can only be de-burred by polishing, filing, or sanding.11. Gears must not be chamfered, lightened, or relieved.
  1. 10 and 11 tooth pinion gears are not allowed.
  1. Plastic top plate gears are not allowed.

Shims between the gears and the top plate are not allowed.


  1. Magnets must be Ceramic, Aurora Super II (Yellow and blue), Johnny Lightning, Auto World , DASH ,BBT  or Killer Bee magnets may be used. The magnets may be sanded to fit the chassis. The distance between the magnets must be a minimum of .700″; no exaggerated sanding is allowed to close the armature gap. This will be teched using our custom-designed, specially fabricated Plug.

1a. The inside surface of the magnets may not be sanded.

  1. Magnets shall not be affixed to the chassis by any means.
  1. All magnets shall have original factory paint.  In the event of paint shortage on the magnets, they will be compared to magnets in the official tech kit and if still in question they will be measured for strength against like magnets by the designated measuring tool for the event.
  1. Painting of magnets shall not be allowed.
  2. Spacing between magnets shall be no less than .700.
  3. 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.
  4. Downforce of car not to exceed 6.5 on the Doanes calibrated scale.

No “reversed zapped” magnets

Pickup Shoes and springs:

1.Pick up shoes and springs shall be solid copper and manufactured by Aurora, Model Motoring, American Line, BSRT (model 504 only) Slot Tech, Dash or Wizzard, Champ and Dr. Oogan springs are legal.  Ski shoes are not allowed.

  1. Pick up shoe springs may be cut (coils removed) to desired length.

3.Pick up shoe springs may be stretched to desired length.

The “step” in the pick-up shoe must remain intact and be unaltered, except that only the first      bend in the step, (Bend #2), may be changed slightly so that proper “pick-up 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. (Bend # 1) may be adjusted back toward the chassis to allow the shoe to hang on the chassis nipple. The front vertical slotted portion of the pick-up shoe may be bent to limit shoe travel. The rear hook portion of the pick-up 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.

  1. Pick up shoe travel may only be adjusted by 1) bending the front “window” portion of the shoe that hooks to the front of the chassis, 2) bending the rear hook which attaches to the chassis’ copper hardware, 3) bending the hangers on the chassis into which the rear hook of the shoe connects or 4) adding heat shrinkable tubing to the top of the front window.
  1. Shims may be used between the pickup shoe spring and chassis.
  1. The window of the shoe cannot be part of the contact patch. We understand that some of the new DASH PU shoes are bent so that the window slightly becomes part of the contact patch, these will be evaluated on a case by case basis.



  1. Rear wheels may not be made of Brass or solid Delrin.
  1. No axle weights, wheel weights or hub caps allowed on rear axle or inside the wheels.

Note: A small delrin retainer will be allowed on the outsides of rear axle for the purpose of adjusting crown gear mesh rear pinion. The diameter of the retainer must not exceed 0.125″ with a thickness not to exceed 0.070″

  1. Spacers shall be made only of plastic, copper, aluminum, brass, or steel. (Outside diameter cannot exceed 0.125.
  1. All four tires shall simultaneously touch the test track in the static position.
  1. The width of the fully assembled tire/wheel/axle assembly shall not exceed 1 and 5/16″.
  1. Lateral movement of the front tire/axle assembly shall not exceed 1/32″ (.03″)
  1. Spacers may be used on the rear axle both inside and outside the chassis.
  1. Any axle or shaft material in the car is allowed, including titanium. Bottom of cluster shaft may be cut.
  1. The front and rear axle diameter must not exceed .065

9a. Wheel retainers may be glued in place.

  1. All on market weighted Front Ends are legal, i.e. ZomminMotorsports, RTHO, Wizzard , OS3 and BRP. Front ends must use the parts as originally manufactured, Parts may not be modified to accomadate other setups. All new front ends must be sent to ECHORR for approval at least 60 days before the Challenge date.
  1. No mixing and matching of front end parts from different manufacturers. This does not apply to wheels, axles, tires and o-rings.


No “one of “parts allowed on the cars.



***At least one car from each Team Box will be teched regardless of finishing order.



A Final Rule:


If anything is not specifically stated or addressed in the above rules it is NOT permitted.