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The Horn goes in

Updated: Jan 21, 2019

If you recall an earlier post the horn bolt I’d located was unfortunately too short and so I’d parked the installation pending sourcing a bolt.

In the meantime I’d researched the sort of bolt I needed and sourced an A4 Marine grade stainless steel alternative M8x50 hex head bolt. I’d figured this would be better than the stated CC bolt. I know I could have spoken to Derek at CC, unfortunately it’s been half term and Derek is taking a well deserved break from us builders :-)

I also sourced x1 titanium bolt out of interest. I’ll post about that later.

Installation of the horn was relatively straight forward although I did make one tiny mistake which created a little inconvenience.

The first step was to drill the mounting hole, remember I’m building a 420 with the modified dry sump setup. I actually taped up the underneath of the steering rack cross member and measured half way between the existing bolts and then out towards the front edge of the member. I marked the drill site on the tape.

There is no precise statement as to where to drill and you are left with a best guess from the diagram. I took the logic not to get too close to the edge. If I’m wrong and my hole is too close to the centre I’ll source replacement brackets for the horns, should that happen.

Once I had my spot I used a punch to mark the metal so as to guide the drill. I then removed the tape and punch a few more times to get a good mark.

Caterham 7 S3 420R Horn location
Drill site

I drilled with a 4mm metal bit followed by the required 8mm bit. I’m not sure if the smaller hole followed by a larger hole is required but it worked for me and gave a good clean hole. I did use cutting compound on both bits too.

Next up is to drop the bolt and washer down through the hole. Oops here is my mistake.

Drilling up I’d not taken account to provide sufficient clearance of the steering rack. When trying to drop the bolt through it clashed so so slightly. Solution was to remove the rack clamps and lift the rack. Simple but a bit of a bind.

So if you are reading my blog and looking at the horn yourself remember to ensure you have clearance of the rack.

Afterwards fit the collar underneath (see previous blog post on horn) followed by the horns and nyloc.

You must ensure the electrical connectors are close together which requires rotating the horns, and that requires releasing the nut on the rear of the horns. I found the nuts were pretty tight, leaving you wondering if they should be released, but there isn’t another way.

Caterham 7 S3 420R Horn
Connectors too far apart, need to be rotated after releasing nuts on the back of the horns.

That’s it really, then torque everything up.

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