Mods to trailing arm suspension
Discussion
I have long thought about changing the way in which the trailing arm suspension on my Tasmin is attached to the chassis. I have read on here about “boxing” the end in a new bracket design and had even seen grainy photo,s showing different brackets at the earth end, but nothing clear and no description of the modifications. Being the end of the sprinting / hill climb season I have decided to fit new brackets along with spherical bearings in the arms. I hope this will help others who are considering making a similar change.
If you have read this far you will know the design of the current system which is basically a pin fitted into a rubber bush which is cantilevered off the chassis. The trailing arm then pivoted on the pin, so any large loads moved the pin and bush thus allowing the camber and toe in of the rear wheels to vary.
Paul Forrest, at X Works Services, and I had discussed this before and decided to design new mounting brackets to hold the pin / bolt in double shear and fit large spherical rod ends to the arms.
The bearings used we used were 0.625” bore with a 0.75” UNF thread. A sketch was produced of the assembly and Paul removed the existing suspension and pins and fabricated a bracket and welded it to the chassis (see photo 1). A similar bracket was made and fitted to the nearside of the car.
The distance from the centre of the hole in the rod end bearing to the actual end of the threaded portion was then marked on the trailing arms, and they were then cut accordingly. We left a small allowance that could be removed later if necessary. Two rectangular plates were then made from 0.625” steel plate and cut to fit inside the ends of the cut arms. Holes were then bored into the plates and headed threaded bushes made to fit into the holes. The threaded bushes were then welded into the plates and the plates subsequently welded into the arms. (see photo 2)
The arms complete with adjustable, spherical rod ends were then trial fitted into the newly fabricated brackets and packers fitted to locate the arms to give the approximately correct camber and toe in angles. The final adjustments can then be made by rotating the eye ends. Conical spacers were manufactured and fitted to allow lateral rotation of the spherical bearings without binding.(See photo’s 3 & 4) Before fitting of conical spacers.
I will report back after a test session on the track at 3 Sisters as to how it feels.
Many thanks to Paul Forrest at X Works Sevices who turned ideas into reality! And my friend Sean Bourne who manufactured the end plates, threaded inserts and conical spacers.
If you have read this far you will know the design of the current system which is basically a pin fitted into a rubber bush which is cantilevered off the chassis. The trailing arm then pivoted on the pin, so any large loads moved the pin and bush thus allowing the camber and toe in of the rear wheels to vary.
Paul Forrest, at X Works Services, and I had discussed this before and decided to design new mounting brackets to hold the pin / bolt in double shear and fit large spherical rod ends to the arms.
The bearings used we used were 0.625” bore with a 0.75” UNF thread. A sketch was produced of the assembly and Paul removed the existing suspension and pins and fabricated a bracket and welded it to the chassis (see photo 1). A similar bracket was made and fitted to the nearside of the car.
The distance from the centre of the hole in the rod end bearing to the actual end of the threaded portion was then marked on the trailing arms, and they were then cut accordingly. We left a small allowance that could be removed later if necessary. Two rectangular plates were then made from 0.625” steel plate and cut to fit inside the ends of the cut arms. Holes were then bored into the plates and headed threaded bushes made to fit into the holes. The threaded bushes were then welded into the plates and the plates subsequently welded into the arms. (see photo 2)
The arms complete with adjustable, spherical rod ends were then trial fitted into the newly fabricated brackets and packers fitted to locate the arms to give the approximately correct camber and toe in angles. The final adjustments can then be made by rotating the eye ends. Conical spacers were manufactured and fitted to allow lateral rotation of the spherical bearings without binding.(See photo’s 3 & 4) Before fitting of conical spacers.
I will report back after a test session on the track at 3 Sisters as to how it feels.
Many thanks to Paul Forrest at X Works Sevices who turned ideas into reality! And my friend Sean Bourne who manufactured the end plates, threaded inserts and conical spacers.
wellyone said:
I will report back after a test session on the track at 3 Sisters as to how it feels.
Not sure on the pro's and con's but would you be able to place a small camera in the area looking at the trailing arm pin and joint and then we would see the stresses if any at work...If its pushed on the track then that would pass for road cars....
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