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earthing
jabbahutt - 14/9/06 at 05:26 PM

If I have a powder coated chassis am I correct in thibkibg that to create a decent earth I just need to remove the power coat and attach the relevent lead to the bare metal?
What is the best method of securing, I was thinking of drilling a small hole and using a self taping screw then a smear of petroleum jelly.

Am I barking up the wrong tree?

caber - 14/9/06 at 05:34 PM

Yes remove all traces of powder coat but I would not use a self tap. You could use a nut sert or drill all the way through and use a nut and bolt. If youare powdercpated the option of welding a nut onto the chassis is a non starter. Basically you should aim for the largest area of contact through the entire assembly and tighten it down hard.

caber

nitram38 - 14/9/06 at 06:26 PM

Another option is to use a rivnut and bolt.

jabbahutt - 14/9/06 at 06:31 PM

does anyone know if the demon tweeks rivnut gun £45 approx can handle steel rivnuts as at present I'm only using aluminium which isn't a good conductor is it?

StevieB - 14/9/06 at 06:35 PM

Regardless, you'll get a rivnut gun cheaper elsewhere anyway!

graememk - 14/9/06 at 06:46 PM

aluminium is a better conductor than steel, i've used a rivnut and a big bolt

tks - 14/9/06 at 07:14 PM

if we not take the expensive materials into acount then

its Coppper
Aluminium..

in that order..

Power cords are many times made of aluminium because they weight less!!

Tks

MkIndy7 - 14/9/06 at 07:23 PM

Wouldn't drilling and tapping the Chassis give better contact that a rivnut?

k33ts - 14/9/06 at 07:33 PM

quote:
Originally posted by MkIndy7
Wouldn't drilling and tapping the Chassis give better contact that a rivnut?


i agree much better way

StevieB - 14/9/06 at 07:45 PM

quote:
Originally posted by k33ts
quote:
Originally posted by MkIndy7
Wouldn't drilling and tapping the Chassis give better contact that a rivnut?


i agree much better way


I'd have thought this would only be the best way where you can get a nut onto the other side to give a tighter, more secure connection (and alos increase the contact area for a good earth). If not, then surely rivnut is the best (if you take up all the powder coating so the whole rivnut is in contact with the chassis)

wilkingj - 14/9/06 at 07:48 PM

Just weld a short piece of 2mm x 12mm of a suitable length and drill a hole through it then use a Nut and Bolt.

Look in my archive under Earth strap.

For the odd earthwires, I use steel Rivnuts. I would not use Alluminium it forms an oxide coating. We tried Alluminium cables on BT many years ago, and in the end ripped them all out. The joints were a major problem due to said oxides. Even using special jelly filled serrated crimps it was still a long term isssue.

Drill and Self Tappers are OK, but use a decent blob of heavy grease. Also Dont site your earth points where they can get wet, ie spray from the wheels etc.. find a dry corner and run the wire to there. Less water means better joints and more reliability.

MkIndy7 - 14/9/06 at 07:58 PM

quote:
Originally posted by MkIndy7
Wouldn't drilling and tapping the Chassis give better contact that a rivnut?



I'd have thought this would only be the best way where you can get a nut onto the other side to give a tighter, more secure connection (and alos increase the contact area for a good earth). If not, then surely rivnut is the best (if you take up all the powder coating so the whole rivnut is in contact with the chassis)


When you Tap the Chassis you have the surface area of the threads in complete contact with the chassis and also the area under the bolt head.

caber - 14/9/06 at 08:18 PM

DO NOT use alluminium rivnuts or nutserts for earth! There is a strong electrolytic reaction between aluminium and steel as soon as the metals get wet and you try and drive a current through them you will get very rapid corrosion and very quickly no aluminium rivnut. In my original post I suggested nutserts, these are steel rivnuts!

Caber

nitram38 - 14/9/06 at 08:31 PM

I have used bzp steel rivnuts as earths (they don't rust). When you put them in, the back of the rivnut expands and grips the unpainted, inside of the box section.
I have n't had any earthing issues.
You can even get stud rivnuts so that you have a thread to put a nut on.
I bought my setting tool for £80 from capital supplies in croydon. It came with tools for 4mm, 6mm, 8mm & 10mm rivnuts and rivnut studs.

JoelP - 14/9/06 at 08:52 PM

i would always where possible weld a bolt in head first before powdercoating. Surely unbeatable?

davew823 - 14/9/06 at 10:43 PM

The trouble or problems with using a rivnut for electrical grounding usually does not surface for several years. Typically it is at least 2 or 3 years before the oxide or corrosive effects will start causing electrical problems. That's why it took Ferrari five years before they issued a recall. If you have an older build that should be one of the first things to verify if you start having electrical problems and the electrical system is grounded thru rivnuts. Grounded thru bolts Dave

nick205 - 15/9/06 at 08:01 AM

jabba

After thouroughly cleaning the paint away, top and bottom I drilled a 10.5mm dia hole through the Indy chassis engine mounting plate, which s 3mm steel plate well and truly welded by MK over the 2 lower engine bay chassis rails. I've then used an M10 nut and bolt with star washers to tie all my earths to the chassis and covered with a blob of petroleum jelly for protection. I don't have any earth problems at all with this set-up.

IMO the rivnut and self tapping method do not provide good reliable long term earth bonds.

HTH
Nick