An Interesting Question about the Morris Cowley 1932 coil ignition conversion
I have a 1932 Morris Cowley two seater tourer. That model and year was when the Cowley first used coil ignition. Years ago (like 1970) I wrongly believed that the coil conversion was a botched job and could not be original. I now know that it was not and that the so-called 'botch' was in fact Morris's first attempt at a coil ignition system.
Sadly, at that time I discarded that coil system and purchased an appropriate magneto for later installation. This, of course, would prove to be incompatible with the ignition switch on the dashboard since a magneto does not use a switched 12v supply. So, when after many years I came to get the car working again around the year 2000, I had to modify the wiring slightly to use a relay which earthed the magneto when the ignition was turned off and which removed the earth when the ignition was turned on.
That worked surprisingly well and the car recently demonstrated this by succeeding at the 2014 Kop Hill Climb. Nevertheless it is of course 'wrong'.
I have therefore been trying to reinstate the coil ignition of some 40-50 years ago after discarding it but of course no longer have the parts. I have acquired a selection of appropriate distributor parts from which I hoped to rebuild this but an interesting query emerged which was whether or not the original coil ignition adaptation did or did not use a through drive which connected to the drive from the camshaft or whether it used some additional gearing inside the adapter.
The manual (above left) shows the unit with the coil centred in an 'alloy' block and clamped by the same mechanism as was used by the magneto before it. This appears to show the distributor offset towards the front of the car but of course it might be that the centre of the assembly is actually offset towards the rear. A picture I have of a coil-converted 1929 Cowley (above right) shows what this looks like in practice. Again the appearance is that the distributor drive is offset towards the front.
The question was this, does the distributor drive pass straight through to connect via the Morris brass 'butterfly' connector to the fabric-based camshaft drive or is it displaced to the front of the car perhaps with a 1:1 or a 1:2 gear connection inside the 'alloy' block?
The unit DOES contain a 2:1 gearing system. It is designed to replace a magneto and these have a 2:1 gear inside (to permit four stroke operation) so the replacement has to do the same. Thus, the drive shaft that emerges from the engine operates at crankshaft speed, the internal rotor of the magneto operates at crankshaft speed but the distributor part of the magneto (and that of the coil conversion incidentally) is reduced by 2:1 to accommodate the four stroke engine cycle. To add somewhat to the confusion (!) It should be noted that the drive that comes from the engine is taken from the camshaft which itself turns at half engine speed but that is increased by gearing of 2:1 inside the engine so as to make the external drive operate at engine speed.
The whole is further confused for those investigating this problem by the fact that the pulley wheel at the front that drives the fan on Cowleys is actually driven from the camshaft and not the crankshaft - that is to say it runs at half engine speed. Then, as if that s not enough to get your head round, the starting handle acts on a gear so that as it is turned clockwise viewed from the front the engine turns anticlockwise...Phew!
I have now purchased a coil conversion from
Mr W McKenzie
Austin Reproduction Parts Ltd,
Unit 29 Glenmore Business Park,
Poole, Dorset BH16 6NL
(T:01202 625242, W: www.austinrepro.com)
This device connects to the same fabric connector and butterfly and utilises a Bosch 009-like distributor with centrifugal advance but no vacuum advance. It can be supplied with a fitting to permit manual advance/retard in which case the centrifugal system can be partially or completely disabled - see http://www.austin7.org/Technical%20Articles/Distributor%20Set%20up/ A points gap of 0".016 seems correct.