National Capital Area Council - BRD Cubmobile Derby

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BRD Cubmobile Derby

Event Details

  2016 Bull Run District Soapbox Derby

  Date:     Saturday May 14th, 2016 (rain date 15th)

  Location: Victory Elementary School, 12001 Tygart Lake Dr, Bristow, VA 20136

  Times:    8:30          Setup (Volunteers Needed)
   9:00          Registration and Impound
   10:00-1:00 Race

   Cost:  Registration is by the Den's car ($20 per car) plus the number of scouts taking part at $1 per scout in the Den (Den's Racing Team) .

Uniform:  Bike helmet (Mandatory.  No racer will be allowed to participate without a helmet)
BSA Field Uniform (Class A) with long pants. 
Recommend long sleeves.

Video from the 2015 Cubmobile Derby (9 minutes, 20 seconds):

 Vehicle Requirements:   

·         Unique car per Den/Rank. Can have multiple cars. All boys will drive twice  (Please keep it to about 5-8 boys per car)

·         See Diagrams.

  • Note 1 – use two-sided brake.  Brakes with one handle on one side of the center frame will cause fish-tailing.
  • Note 2 – install steering blocks almost flush to either side of front beam to limit steering. 
  • Note 3 –Bearing wheels are permitted (recommended)
  • Note 4 – Keep wheels between 5-8 inch diameter.  Wheels taller than 8 inches can make the car more top-heavy.
  • Note 5 – Boys steer with their feet, not the rope.  Do not block access to the front axle when using a car body.

 Volunteers Needed:

  • 4 Timers (with stopwatches or smart phones)
  •  Clerk of Course Assistants (order behind the start)
  • Lane Managers (keep the kids reasonably on the track)
  • Ramp Managers (put the cars on the ramp)
  • Setup (brute labor)

Prizes:  TBD.  Awards for 1st, 2nd and 3rd fastest average time, as well as 3 Design awards.

Bull Run Cubmobile Specifications:
The Bull Run Cubmobile is a modified version of the standard Cubmobile as seen in the Bear Handbook. It has been reduced in size to control costs, improve portability and make storage less burdensome on suburban scouters.

  1. Dimensions are no more than 22 inches wide by 46 inches long. The vehicle must fit on the ramp.
  2. Wheels can contain bearings or not
  3. Wheels must be at least 5 inches in diameter and not more than 8 inches.
  4. Steering limiters are placed on the front axle to either side of the frame not further than 1/8 inch from the frame of the car. (Safety – cars that over steer flip their drivers.)
  5. The car must have a rope steering bridle. Not used for primary steering but in conjunction with the feet.
  6. The driver’s feet must reach the front axle. The car is steered by the feet.
  7. Wheels may use either lag bolts and washers mounted into the axles, or a solid axle at the leader’s discretion. Cars with lag bolts will be inspected for cracks in the axles for safety. A cracked axle will not pass inspection.
  8. Wheels may use any lubricant the leader chooses.
  9. Minor changes to the design are permitted provided they do not compromise safety. The Red Toolbox kits previously used remain a valid design.

Parts List for Chassis only: (body is optional)

1 @ 10 foot piece of 2x4

4 @ Wheels (8inch or smaller)

4 @ Lag Bolts (size dependent on wheels used)

1 @ ½ ” bolt with locking nut (4inch)

11 @ washers (size dependent on bolts

8 @  1 ½ ” wood screws (for the seat)

24 @ 2 ½ ” wood screws (for back axle and re-enforcement blocks)

1 @ 2’x2’ cut of ¾ inch plywood (for the seat)


  1. The body is constructed of common 2x4 lumber.
  2. The front axle is connected by a single 3/8” wide bolt. Separate the frame from the axle by inserting a washer between the two boards and use washers on either end too.
  3. The rear axle is attached with four screws or bolts to the frame.
  4. The seat is attached with four screws to the frame.
  5. The seat back is attached to the frame by means of the 6in @ 2x4 piece cut in half at a 15% angle
  6. The brake handle straddles over the center of the frame and the brake itself straddles under the center of the frame, with connecting levers on either side. A center brake is key to prevent fishtailing.
  7. Wheels may be attached using either a heavy bolt (lag) directly into the axle itself. However, a solid axle is recommended.
When & Where
Bull Run District Cubmobile Derby
Victory Elementary
Saturday 05-14-2016 11:00 AM ET to 3:00 PM ET Past
More Information