Tech Talk - Feb 05, 2010 

Torsion Bar Welding

The nature and method of fitting torsion bars permanently to meet with the 2010 chassis rules has brought up a few questions and prompted the issuing of a clarification by Tal-Ko, organisers of the Formula TKM regulations.
 
Let’s give you as much help as we can on the matter.
 
The rule has been created because of the inclusion of any type of chassis may now be raced in TKM providing they comply. It seemed unfair to allow full use of adjustable torsion bars and so put owners of traditional Formula TKM karts at a disadvantage.
 
So the rule is that torsion bars can be used where offered as an option on the kart, but if used, they must be mounted permanently – and this is the real key issue. Some people have just been attaching them with a few tack welds and others securing the clamp but in such a way that the bar can still be twisted to alter its effect.
 
The clarification makes it clearer exactly what must be done – and that is, the torsion bar must be welded at each end directly to the chassis with no clamps used.
 
It goes further in stating that while the type of weld is free, it should be of a nominally continuous type and extend to at least 75 per cent of the circumference of the join. This allowance is to take into account the fact that in some places it may be difficult to weld all the way round with full access.
 
Any type of weld includes tig, mig, braze etc. But let’s make a suggestion here. If you want to do the job with minimum mess and with the possibility of at a later stage of removing the bar to re-attach with clamps for another class, the answer is to use a tig weld.
 
This is neat but effective and will do the least damage to the chassis paintwork or the chrome on the torsion bar. To minimise the heat damage put some wet rag around the chassis tube next to where you are welding. If you then need to remove to sell the kart or switch classes, simply cut around the joint and then file or use a rotary sander on any of the high weld points. This will then allow the original torsion bar clamp to slide into position covering any effected area.
 
By employing this method you end up with a neat job and have the easiest route to restore back to full adjustability if required.

Grahame Butterworth
Formula TKM Co-ordinator