Military Lightweight Forum

I've now installed a new galvanised and painted bulkhead on my Landy and about to install the relays and terminal box etc. However, i'm in danger of replacing wrong with wrong. The old bulkhead has seen some good botches in past ownership and I cannot find many pictures showing what goes where. In some models, the Coil is located on the Rocker box as was ours but I have seens pics with the coil mounted on the bulkhead - it seems a better place, less vibration etc. Where should the Starter Solenoid be mounted and did the 2A have a floor mounted dip switch? Does anyone have any definitive pics of what the layout should be for a 2A our are there any 2As down here near Stevenage I could take a look see. Any help gtreatly appreciated.
Thanks
John

Gyrojon wrote: ↑

Wed Jan 10, 2024 7:25 pm

I've now installed a new galvanised and painted bulkhead on my Landy and about to install the relays and terminal box etc. However, i'm in danger of replacing wrong with wrong. The old bulkhead has seen some good botches in past ownership and I cannot find many pictures showing what goes where. In some models, the Coil is located on the Rocker box as was ours but I have seens pics with the coil mounted on the bulkhead - it seems a better place, less vibration etc. Where should the Starter Solenoid be mounted and did the 2A have a floor mounted dip switch? Does anyone have any definitive pics of what the layout should be for a 2A our are there any 2As down here near Stevenage I could take a look see. Any help gtreatly appreciated.
Thanks
John

Hi John,
2A's had floor mounted dip switch, coil mount for a 12v I cannot advise because my 2A was a ' 71 24v FFR but I believe it was on the rocker box top same as. Somebody on here must know. Solenoid mounting same as S3.
Regards
Bob

Thanks Bob, I think I will mount the coil on the bulkhead, it might not be “correct” but it feels a better engineering solution

I think the coil on the bulkhead is good place for it rather than being roasted by the engine beneath. The thing is that the effectiveness of the insulating properties of the oil in the coil deteriorates significantly with temperature. I have measured this fall in insulation on many coils and if insulation drops too much the HT will drain away & no spark will result.

This is why sometimes you can breakdown wondering whether you have a fuel or an ignition problem, but by the time you have thought about it & had a poke around under the bonnet the coil has cooled sufficiently to allow a spark & you can continue on the journey. Often there will be an association with cooling effect of raising the bonnet & the conclusion drawn is that it was a fuel evaporation problem.

To further reinforce this assumption the coil is presented to an automotive expert or professional who will test the coil resistances with a meter & pronounce the coil as being satisfactory. What they fail to do is test the insulation with a high voltage tester at the temperature of a running coil or even when cold & extrapolate down that this insulation will drop further when the coil becomes hot. Because they have never grasped the concept of insulation deterioration with heat. You only have to search the internet looking at specialist parts suppliers & car forums etc to find nothing useful or just drivel.

Incidentally painting the coil black will help radiate heat better than an unpainted coil. Matt finish is preferable to gloss. If that sounds nit-picky bear in mind generator panels used with 'B Series' Rolls Royce engines were originally gloss black, later panels were improved with a matt finish. The heatsinks on electronic equipment will generally be painted matt black for this reason.

Yes I know on FFRs the coil is mounted above the rocker cover, but it was not always like that. On 40A FFRs the screened coil & filter were mounted on the bulkhead. The problem with that is that the filter box with the resistors had to be mounted sideways, as hot air rises it will not directly exit through the ventilating slits that are sideways.

So the filter box was mounted above the engine so that hot air from the 44 watts of heat from the ballast resistors could disperse better with the vents uppermost but it meant that the coil had to follow it to minimise the length of cable between it & the filter box. To leave the screened coil on the bulkhead would entail three long screened cables that would increase the chance radio frequency interference (RFI) being radiated along these cables. The outer mesh screening of cable is not a complete barrier to RFI.

The only thing with coil on the bulkhead, try to make it so that the king lead (HT) is not further away than it need be, many sets of 5 ignition cables have a rather short king lead for many applications.