V1 Steering Rack Modification

The steering team was given the task of trying to correct several issues involving improving upon an existing steering system while keeping spending to a minimum. The main concerns with the existing steering system being

  • the structural integrity of the steering system,

  • repairing the damaged tie-rods,

  • and bump steer.

Another issue of less importance, but still to be investigated by the team is the position of the steering wheel to aid driver comfort and control.

In order to be able to modify and quantify the concerns for the steering system, proper measurements of existing parts and geometry had to be done first and modelled with CAD software to get a better idea of how to implement corrections.

 

Bump steer was seen as a big issue, so the toe angle of the front tires was measured through the full range of travel of the suspension, and it was found that the bump steer was excessive with a change of approximately 15 deg. This was seen as unacceptable, so CAD models were made with virtual measurements to compare to the real life ones ending with similar results; because of the agreement in virtual and real life bump steer measurements, different repairs could be tried on the CAD model and decisions could be made about the best option to correct the problem. After many iterations and stress calculations, the best solution was agreed upon: the tie-rod ends connected into the top end of steering knuckles would be flipped and tied into the bottom to better match the planes of the A-arms with that of the tie-rods. With this simple change, a maximum theoretical bump steer is seen to be around 3 deg — a huge improvement over the existing range!

To improve the structural integrity of the steering system, it was decided to insert support blocks as far out on the steering rack as possible. The best solution decided upon was using medium gauge sheet metal and making brackets with a bore large enough to fit a bushing and the rack. The support will be mounted to thicker gauge plates that will be welded to the frame of the baja vehicle via nuts and bolts. This should help considerably to limit the amount of bending stresses experienced on the rack as well as lower the forces acted upon the steering rack base.

Tie rod replacements have not been decided upon at this moment, but hexagonal extruded profiles seem to offer the best fit with very reasonable prices. Another issue still waiting to addressed is steering rack extension which should take place soon, and will employ tapped holes on the rack end and spherical ends and a threaded rod as the joining method.

In the coming weeks, part development and installation will ramp up with

  • the manufacturing of the support blocks, mounting plates and tie rod extensions,

  • welding of the mounting plates,

  • ordering of the new tie-rods

  • machining of steering knuckles to allow tapered studs on ball joints to be fastened on the bottom end, and

  • revised real life measurements of the baja vehicle steering system with all the improvements installed

 

-Eric