Rear Suspension Prototype

Project Specifications:

The suspension will connect the axle housing to the frame rails. The axle “housing” will be an 8” section of 1” diameter keyed shaft, made from McMaster-Carr part 1497K281. The frame rails will be parallel, 1” wide spaced apart 6” on center. The rails will have ¼-20 threaded holes, 1” spaced on center running down the centerline of each frame rail. All suspension mounts must contact the frame rails only within the 8” long, 1” wide region indicated on the drawing. Any or all of the ¼-20 mounting holes may be used but no other means of fastening the suspension to the frame shall be permitted. Socket head cap screws or hex head screws (7/16” wrench) may be used. The centerline of the axle shall lie halfway between the fourth and fifth mounting hole +/- 1/8” when the suspension is supporting a load of 10 lbs. When supporting the 10lb load the center of the axle housing must be 2 ¼” below the bottom of the frame rail +1/2” / -1/4”. The orientation of the keyway on the axle housing is optional. 1” long ¼” square keys will be available but keys may also be made integral to the components designed to mount the axle. The suspension must entirely remain within the 7” between the outsides of the parallel frame rails, leaving ½” of axle housing exposed on each side. There is no restriction on the number or size of axle mounting points that may be used within the 7” between the frame rails.


Performance Requirements:

All components must remain connected if the suspension is picked up by the frame (i.e. if the “vehicle” is jacked up by the frame such as to change a tire, etc.) and must return to their proper position when the load is reapplied without outside intervention (you don’t want to realign your car after you jack it up).

The suspension must support a 10lb load without failing. The load will be applied over the centerline of the axle housing.

With the suspension supporting a 10lb load, the suspension must be capable of deflecting an additional ½” without bottoming out (i.e. run out of suspension travel). The load required to do this is not specified other than that it must be greater than the 10lb alone. The suspension must do this without failing.

Without the 10lb load, the suspension must be able to support the impact of 5lb falling from 1ft. The suspension may bottom out in this test but should not fail.

The suspension must be able to support the reaction torque created when the vehicle is driven by the wheels. The reaction torque will be 10in-lb which must be supported without failure. Rotational deflection shall be less than 20 degrees (too much deflection could cause a drive shaft to pull out, bind or cause other problems).

For all tests, failure will be defined as a break or plastic deformation that prevents the successful repetition of any test previously passed.