A good bodge or a terrible idea? (Starter Cable)

[stevek]

I had a new main starter cable made to order for the 924 but upon fitting it I was having problems. The original cable had a flag terminal at the starter motor end and I just had a normal ring terminal put on the replacement. I didn't foresee that being a problem but it was. To get the direction of the cable required I had to space it forward with washers on the terminal in order to clear the other terminal. There isn't enough space to have the cable exit in a different direction and loop around because of the block and manifold...


Unfortunately that was compounding the already minimal clearance for it to go behind the heat-shield (I don't think it would have taken long to wear through)...


I came up with a 'bodge' solution to adapt it to a 'flag' terminal. Its a 15mm water pipe squashed with a 'mending plate' inside for some strength...




Fitted in place it looks like this...


I have also bent the edge of the heat-shield slightly to help too...


I have not tried it yet but do you think its up to the job? I guess the amount of copper is up to the current load and I think its rigid enough but have a missed anything obvious?

-Steve-

[usedabused]

From that angle it looks very close to the manifold,

[stevek]

The picture is maybe exaggerating it but it is pretty close to the manifold. The cabling and starter motors on 924's often have problems because they get cooked by the manifold and down pipe.

I have loaded up another picture showing a different angle. The cable is now in nearly the same position as the original one, about 8mm closer to the manifold at a guess...

[Dorset_Clive]

It might be worth doing a quick cross section calc for the pipe and compare it with the starter cable. My gut feel is that with the steel inside, electrically it would be fine.

Just did a quick Google, and if you can believe the internet, 'normal' copper water pipe is 0.7mm thick, meaning 15mm dia has a cross section of just over 30mm2. A quick look on the VWP site (http://www.vehicle-wiring-products.eu/VWP-onlinestore/cable/batterycable.php) shows starter cable at 25mm2 carrying 170A and 35mm2 can carry 240A, so 30mm2 will be good for about 200A...plus the steel inside!

Probably of more concern is, is there *any* chance the 'extension' could move and short out against the engine...that would be a best a bit smokey and potentially a big bang!

[composimmonite]

I wouldn't feel happy about that on my car. It you had seen how fast a battery short destroys a car then you would understand why I would never have such a large exposed amount of live wire / terminal. Closeness of manifold precludes insulation so why not remove cable and get auto electrician to fit a proper flagged terminal ? Another suggestion would be a short lead with the proper flagged terminal and join the two cables together at a junction box -

In fact you could use an isolator switch as the junction ?

[stevek]

Dorset_Clive - Top work on actually calculating the cross sectional area of the water pipe! Quite an easy calculation now you point it out but I didn't think of actually working it out.

15mm x 3.14 = 47.1 mm (circumference) x 0.7mm = 33mm2 (I'm aware this isn't the 100% mathematically correct way to work it out but its gonna be pretty close)

Like you say plus the steel it should be OK from that perspective. It almost seems specced for the job!


It can't physically move more than a few degrees, but even if it could move right round there is no way it could touch anything else (engine/block/starter can't move in relation to each other) so it should be fine from that point of view too.


composimmonite - I appreciate your concern, as much as it looks like its quite suitable for the job it maybe isn't the best idea. It can't touch against anything else but it does seem a bit exposed for a live terminal (especially unfused!). Also it could be prone to vibration loosening it off after a while which would be a worry. I think there is enough length in the cable to have a flag terminal fitted, so I will find a place to do that for piece of mind I think. I'm not keen on the junction box idea. I would want to fit a cut off up by the battery on the bulkhead if following that idea, though I like your sideways thinking with that one.






...maybe it was a terrible idea

-Steve-

[stealthstylz]

Looks fine to me, though you could always shrink wrap it then cut out the contact areas.

[DavidB]

Is it touching anything metal and does it move freely?
If not, it'll be fine.

[Colonelk]

I don't think Id run it as a permanent fix, maybe a temporary solution, just because as said a battery short can be catastrophic. I cant see anything bad with it except the danger it may clock itself round with vibration.

[monkeep]

My only concern would be the amount of thread in the nut, I would suggest either using a thinner washer on the outside or not bothering with a washer at all...

Then you'll be able to get a better thread contact which will resist vibration better. The nut will also hold more torque before the thread gives out on either the nut or the stud.

[scott15]

Perfectly fine.

Take it you boys aren't really into car audio, as this is done on almost every decent build. Search Google for 'Car audio bus bar' and you will find thousands of results of people running much bigger bars, with multiple runs of 0 AWG wiring, with absolutely 0 problems, and 0 concerns.

[stevek]

scott15 - I must admit I haven't looked into high power car audio. I googled 'Car audio bus bar' but they seem to be rigidly mounted at both ends normally and also on fused feeds so a bit less risky in case of a failure.

monkeep - I had to connect another cable for the alternator onto the terminal too so I have got rid of both the washers and the bolt is now on the full thread again, Cheers.

Colonelk - I think your right, its good enough to get me going but should really only be temporary.

DavidB - No & No so fingers crossed it'll do for now.

stealthstylz - I don't have any heat-shrink big enough! I don't intend this to be permanent.

[Colonelk]

I wouldn't say 0 problems, I know of one big audio car from back in the day that got destroyed by fire when someone dropped a tool across the bus bars

[chairchild]

nothing's foolproof in the grand scheme of things - but that's a fix I'd be happy with