Lotus Elan

Earthing

PostPost by: richard sprint » Wed May 27, 2009 11:04 pm

I have just finished applying POR 15 to a new lotus chassis (i.e. in storage for 20 years) and it came to mind that I need to gain good earthing to the chassis. I will need to grind away some of the POR to get back to clean metal - what is the best way to tackle this? Should I fit a brass post to which earth cables can be attached?
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PostPost by: gerrym » Thu May 28, 2009 12:50 pm

Richard, ideally the earthing connections (ie your post) need to be welded to the chassis. This minimises the number of electrical junctions.

I have welded on two studs to the chassis; one close to the starter motor and the other close to the battery in the boot.

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PostPost by: richard sprint » Thu May 28, 2009 9:32 pm

Gerry

What studs did you use i.e. if mild steel how do you stop these from rusting?

What diameter stud did you use?

Do you happen to have the dimensions where they are located - my chassis is off and bare so difficult to assess the accessability without everything in place - hope this makes sense....

Thanks

Richard
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PostPost by: memnon » Sun Jun 07, 2009 7:07 am

A period solution would be to braze / silver solder a brass stud. It's a good conductor and stays rust free.
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PostPost by: alan71 » Sun Jun 07, 2009 7:54 am

I would go with the Brian Buckland recommendation of using the rear suspension turret as an earth point. I haven?t done it myself (not had any earth problems) but it is clearly better to bolt to a threaded hole in the chassis rather than rely on a bolt in a bobbin in the body.

Alan.
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PostPost by: RichardS » Sun Jun 07, 2009 5:10 pm

Richard

God to see anther Richard with a Sprint.

If you look through the thread on my Sprint rebuild elan-f14/elan-sprint-out-hibernation-t14711.html I described how I have earthed my Sprint - haven't yet got the car on the road but the indicators and lights all glow nice and bright!

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PostPost by: gerrym » Sun Jun 07, 2009 6:53 pm

Richard, see my post May 6th of this year for some details of the earthing complete with sketch.

Basically I have a additional stud welded to the chassis pointing upwards into the body, located between the two rear- most threaded bobbins. A hole was drilled in the chassis ( suggest 7/16UNF bolt) to suit the bolt, and the bolt head welded to the underside of the chassis. This goes into a plain hole in the body (hint suggest tapering the end of the bolt then it acts a a stab-in locator and guides the body into correct orientation wrt to chassis). A normal zinc plated bolt is fine, just grind the zinc on the head of the bolt before welding. Inside the body, metal to metal contact is helped by using a metal type of shake-proof nut (eg Philadas), vaseline will stop corrosion. The idea is that the corrosion prone connection is now a thread inside the relatively dry boot, at least compared to the underside of the car.

Further earthing studs are just simple studs inside engine compartment. welding a bolt by it's head achieves this. A good coat of POR 15 to waterproof the weld should finish the job.

Don't try and braze, you are likely to get a dry joint unless using oxyacetylene. Brass is also very weak and will probably break at some stage in the future, just what you don't want with a permanent fastener.

Regards

Gerry

Note, using the rear turret bolt, threaded into the chassis is a P.I.T.A as its not simple to access (at least in the Plus 2), plus lining up the bobbin hole with the chassis tapped is not guaranteed depending on how chassis and body are supported.
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PostPost by: richard sprint » Mon Jun 08, 2009 10:45 pm

Thanks for all the suggestions...

Richard

I have viewed your project though not specifically for the earth connection, I think yours will be back on the road before mine being as it is a full restoration with new chassis - I reckon I'm about 25% through the project, it is proving to be very satisfying. A major landmark today in that after months of stripping down, shot blasting and painting - I actually started putting things back on in the shape of two new lotocones! small steps but a step forward none the less!

Richard
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PostPost by: RichardS » Tue Jun 09, 2009 6:07 pm

richard sprint wrote:Thanks for all the suggestions...

Richard

I think yours will be back on the road before mine being as it is a full restoration with new chassis -

Richard


I've set myself a target - would like to drive to the Gold Cup at Oulton Park at the end of August. I'm not too far off now. I have decided to leave the respray and concentrate on getting back on the road. The paintwork is pretty awful so the Sprint will look rather tatty - but underneath all should be spot on.....!!!!!

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