Engineering blog: Steering Dampner Pair Screw Renewal (Teverun Fighter)

It was observed over several thousand kilometres of use that the steering damper develops play (wobble) on Teverun Fighter 11+ and Supreme around the rear pair screw (pin). This article shows a renewal procedure.

It appears the design flaws is that the head on the bolt in the pair screw presses against the softer casting of the bracket, thus introducing play. Due to what is likely thread locker or other factory bonding, the pair screw is difficult to tighten or loosen. In this scenario disassembly is difficult.

The Fighter Supreme 7260R has introduced a grub screw on the front bracket to further support the front pair screw. It is possible that a similar approach could be adopted for this rear bracket to further compliment this renewal proceedure.

This video shows the issue (play/movement) before renewal was undertaken.

During renewal, it was identified that the sleeve that accommodates the pair screw is not sufficiently secured within the casting - visible movement in this video. Additionally the hole for the LHS of the casting appears to be somewhat countersunk. Subsequent photographs reveal the countersink in casting is from the bolt head of the pair screw. The bolt presses against the sleeve, thus is "tight" but is not resting against the bracket casting (similar to issue in front bracket on the 7260R damper).

The outcome of the work results in a much firmer mount.

Here is the renewed mount, left hand side (inner). The use of the decorative deck washer is much more supportive on the casting and the socket head much less likely to strip. Also inserted a flat washer to support the load on the decorative washer.

Renewed mount, right hand side (outer), much the same as original but with washer inserted.

Photo's showing the renewal process. The pair screw (pin) comprises of a hollow rod with bolts in each end. The LHS (inner) bolt needs be removed. In this instance the RHS (outer) was removed first.

The left (inner) was more difficult, would not unscrew with heat or using torx head bit to improve purchase. Interestingly although this bolt is "tight", it does not appear to be holding the pair screw tight against the bracket, there is movement as shown in the 2nd video earlier.

You can see a small gap (0.2mm) around the outside edge of the bolt, shown with a shadow.

Bolt was removed by boring with drill, then tapped out as shown.

Bolt removed. You can see the bevelled edge on the bolt head which matches the pressing in the casting of the bracket.

Re-thread the pair screw to recover from damage when drilled out.

Took three high tensile bolts to restore the thread.

Here is the bracket, RHS (outer) with the sleeve looks OK.

Looking trough, looks OK.

LHS appears to show a bevelled edge, almost countersunk, from the tapered head on the bolt. The countersinking progresses all the way to the edge of the sleeve, suggesting the bolt was factory tightened to the sleeve. Over time, the harder (high tensile) bolt has pressed into the softer casting on the bracket, thus introduced play/wobble.

Renewal was to apply a conical washer (deck washer) to square up the pair screw and ensure it tightens against the bracket casting rather than the sleeve, which secures the pair screw into the bracket and "squares" up the pin, retaining centre position without movement. An adhesive Polyimide tape was also applied (did not have adhesive Nickel strip tape or similar on hand).

Now sits much firmer, as shown in the earlier photos.