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Bonnet Rattle by Brian Richards

At the 2011 concourse I spoke with a number of members who suffered from the dreaded TR bonnet rattle. As a lot of you know, this can be very annoying and there have been many attempts to fix it, mostly involving a rubber washer fitted over the plunger that lifts the bonnet to the safety catch when the dutz are released. This is done in the belief that it is that part of the mechanism that is causing the problem.

I have found that while the problem does involve the plunger, it is the plunger moving at the bottom of the Ú shaped spring holder that causes the rattle. This being the case, no amount of work at the top will fix the problem. I have been able to completely eliminate the rattle by working on the lower part of the plunger, not the top.

It is a simple fix and involves fitting a plastic (nylon in my case but any durable material will work) bush that prevents the plunger from contacting the steel spring holder. It is the plunger contacting the spring holder at this point that causes the rattle. Yes, it is caused by the bonnet moving and causing the plunger to move but it is at the bottom of the plunger the noise is created, not the top where most people concentrate their efforts.

This can be done in any number of ways but this is how I did it. First I made a thin steel washer with two tags pointing out opposite each other. The size of the washer is such that it just fits into the spring holder with the hole where the plunger fits, about 2-3mm larger than the plunger. The two tags are folded up so that the spring and spring holder hold it in the centre of the spring.

A plastic washer is then cut to just fit inside the new steel washer and under the spring but the hole for the plunger is just big enough to allow the plunger to move freely. Now the hole in the spring holder where the plunger slides is enlarged to about 2mm larger than the plunger. Reassemble the mechanism with the steel washer, tangs pointing up, and the plastic washer inside it and under the spring.

The steel washer holds the plastic washer in place and the plastic washer prevents the plunger from contacting the spring holder………….no rattle.