Monday, 28 August 2017

Electronic distributor

I decided to address the power issue on my Austin Seven, it does not have much but I suspected the distributor was responsible as the higher rev's the power was erratic.  I decided to look at the Lucas distributor. I took off the top plate to find one of the weight pivots was destroyed and effectively had no or at best random mechanical advance.

The simple answer I thought was a new electronic distributor. Asking around the paddock at various hill climb meetings I got mixed reviews of such a change. Some said it was good and others said they reverted to the old one with points because of timing/starting issues.

I decided to buy one at the Austin Seven Guildtown Rally (as it was on offer) and had it fitted at the show. I went on a run with the device but I was plagued with misfires and lack of power at higher revs. The dealer offered to change the unit and in fact he tried another unit which had exactly the same charicteristics. I was  fairly convinced it was due to the application in my car as numerous others had complete success, so I decided to purchase the unit on approval.
It is a nice looking part, I have taken it apart looking for the source of my problems and it all looks well designed and put together. I even tried using similar  advance springs to my original unit.  I put an Oscilloscope on the feed to the coil but I could not discern any abnormal behaviour in the waveforms. The Timing light when connected to the engine when running shows a random timing mark unsteady at any speed. The tick-over is rough. There is no appreciable mechanical slack in the drive to the distributor.

I had a eureka moment after competing at Forrestburn recently and decided the unit may be sensitive to noise from the generator/regulator. I have had problems in the past trying to put electronics in a car due to noise issues. In fact I had the same problem with my cooling pump timer. I decided to make a filter with a few bits lying about in my spares box. The theoretical cut-off frequency of the filter of this type is 1/(2*PI* SQRT(L*C)) in this case about 1.5KHz. It has a toroidal coil capable of 5A. The capacitor is an 12V electrolytic type so don't get it around the wrong way.

This completely cured the problems. These bits are readily available on either ebay or RS components.
Before potting it in Silkoflex
My times on a hill climb can only improve. See you at Bo'ness revival.

Here is an Index page for the build

Monday, 14 August 2017

Brakes binding

Despite rebuilding the brakes from scratch the brakes are not that good and they have a annoying habit of binding. This can be dangerous on the road when wet as you suddenly go into a skid as one corner bites when they others are still free.

I originally made a jig for truing up the drums on the lathe unfortunately I made a schoolboy error when turning it and I managed to insert a runoff. This was due the fact I was having trouble machining it so I put the backplane blank on backwards to machine it. Transferring it around  frontwards introduced a runoff error. This inserted effectively an offset into the drum when trying to tru them up. The error was only a few thou but magnified by the drum diameters caused a real problem

I discovered the error modified the jig and retried the drums on the car. This has stopped the binding issue now completely.

Lathe jig without runoff error

Here is an Index page for the build

Thursday, 27 July 2017

Accesory power

One consequence of fitting my tool storage is the pump needs 12V power. There is no room to fit a stirrup pump so power is needed. I had no intention of fitting a 12V cigar lighter socket in the middle of the dash so I concealed it under the dash (mostly).

Here is an Index page for the build

Wednesday, 26 July 2017

Tool storage

I am going to a car show soon where they have organised a road run. I thought I had better create a tool storage area for a few spanners and the like just in case! There is no possibility of storage within the cockpit so I guess it will have to be the engine compartment. There is dead space above the passenger foot well, but the tools need to be constrained in some sort of box.

The idea I came up with uses the bonnet as a lid thus doing away with any cover for the box.

Cardboard model
Final fabrication
It is more than enough space for two tool rolls, a jack, electric pump and a torch.

Here is an Index page for the build

Friday, 14 July 2017

Starting issues

The Austin had an original  6V starter and a 12V low capacity race battery installed (to save weight). The problem with this setup is it presents the battery with an abnormally heavy load on starting especially when cold. The result is the engine frequently fails to start even on a fully charged battery  The problem at car  trial  events is there is a lot of stop starting and this rapidly canes the battery as you don't get enough charge on a run to replace the starting power lost.

I had a look at various starters but could not find a conventional 12V starter form another car that would fit  without modification. However there is a company called Powerlite that make a AUSTIN 7 1933-onwards BRAND NEW POWERLITE HIGH TORQUE UPGRADE STARTER MOTOR costing a little under £200 from a company called aapoldham on ebay. I have just fitted the upgrade and I am hopeful this is going to resolve some of the problems. It need less power to crank the engine at a far higher speed and is fully compatible with my 12V  race battery. The ultimate solution would be the addition of a generator/alternator conversion but nobody makes one yet. I live in hope. I found a nice starter button on CBS that looks vintage.

Fits seamlessly to the bell housing.

Plenty of room all round.

Vintage start button

Road test

I took it on a road test a total of 18 miles round trip. The car behaved very well on the trip back but I had to stop and fault find a problem with the ignition. A wire to the distributor LT points connection had come loose. After resolving that that the car behaved faultlessly. I managed an indicated 50mph at 3500 rpm. The addition of the high torque starter has transformed the driving experience and ownership. It now starts the car with no drama and hopefully charges the battery between use. I still have reservations about the use in car trials where a lot of stop starting is involved but the car is now very usable.

Here is an Index page for the build

Saturday, 24 June 2017

Battery charging revisited

I took it for a run today after my local car club gathering in the centre of town. To my discomfort I detected a burning smell under the bulkhead (this side of the fire wall).

The wiring harness was installed some time ago along with a 12V (Lucas 3182) regulator feeding the generator. This has the effect of converting the charging circuit to 12V with only one extra part. The only thing you need in addition to the regulator is a 3 ohm resistor to reduce the field coil current to approx. 2A maximum. In reality I found that to get a reasonable rev point where the charging light went out I had to fit a 2.2 ohm resistor. See: (regulator to field coil designated -F).

This probably means it is dissipating in the region of 16W. I had selected a 20W resistor which was 2 x 10 watt jobs glued on to a fiberglass board with epoxy and mounted on the bulkhead. The resistor rating was ok but the heat from the resistor created a foul smell when driving about due to the epoxy being over heated.

Old arrangement
I decided to change the arangement by mounting a single aluminium clad 50W resistor onto an extruded aluminium heat sink and bolted it on it's original location under the dash. This is complete over designed solution for what it is......but I wanted this problem to go away as I hate the smell of burning glue.

I had a standard alloy heat sink extrusion laying about from another project so I machined a lump out of the middle to take the resistor and it's M4 fixings, precision drilled 2 more holes to mount it (where it had been before) and machined some plastic insulators to terminate the wiring connectors (M5 tags either end of the resistor) and secured them in place with rivnuts.

The charging ability of my setup is not great but is now somewhat more reliable and more pleasant to drive with. All I need now is some dry weather to try it out!

New alloy extrusion solution
Here is an Index page for the build

Friday, 5 May 2017



I was not going to add lights as it is mainly going to be used for car trials. However running it on the road would give me the advantage of testing for reliability outside track days. I feel I need road legal lights. I did a 12V conversion on the generator/regulator and I am useing a race battery with limited capacity so I converted all the lights to LED. The battery will not take a charge till above tick over and there is a lot of tick over/starting at car trials. The headlights are 1938 pattern "King of the road" Lucas 4 1/2" headlights. There is no way the generator will support conventional 2 x 35W headlamp bulbs, so I sourced a 2 x high power sop/ tail LED bulbs. The low power (tail) acts as dip and side lights and the high power (stop) gives me main beam.

The indicator pods had 21W bulbs but now have 2W high intensity LED conversions.


The rear was a little more tricky to fabricate, but a lump of cardboard, a box bender, and a little welding att the corners produced the necessary assembly to hold the number plate and lights. The light units are LED indicator + Stop/Side variety are from a vintage motorcycle dealer on ebay. The number plate light was fabricated with a right angle fabrication and a 300mm waterproof LED strip from ebay.

Brake lights

I had a tad of a problem getting the brake lights working despite having all the original hardware so I thought the following worth mentioning. The brake light switch did not align with the tab on the actuating rod. This adverse angle resulted in stiction being applied the switch assembly resulting in the lights staying on after applying the brakes (hysteresis). I had to make an extension to the attachment tab to ensure alignment (and therefore minimising the stiction). I also found the spring tension was critical, I used a brake shoe spring.


I now have a viable lighting setup that will not flatten the battery while ticking over. All side lights (4) take 0.33A or 4W and the side + headlights 1.5A or 18W total. This compares with incandescent lamps which take 20W and 70W respectively.

Here is an Index page for the build