Edgar Westbury Wallaby ignition

I think i will stick to oiling stuff that i can see, seriously though theses explanations are excellent and not something i would glean from reading books. So thanks all again.

The ignition system system is what has been named after its inventor - Kettering.

It was used on millions of vehicles until electronic systems replaced it. Most electronic systems used to use exactly the same coil as the Kettering system.

Back in the 1970s I made an electronic system according to the circuit provided in ETI magazine of the day. The points on that system (capacitive discharge) passed only milliamps, not amps. The disadvantage of that particular circuit was the limited inverter power and it tended to run out of power on a 4 cylinder engine above 6000rpm as I recall. I modified it such that it started easily but allowed better operation beyond 6000rpm.

The electronic systems now use a HALL effect device to trigger the system.

In the future i might convert this to electronic ignition when i am feeling brave.

I now have the said engine so looking at purchasing the coil etc but was wondering about the below thoughts:-

1. Planning on using a 6v dual HT output coil specific to points setup ( as advised above for resistance matching. Is there any possibility to use a single output coil and wiring 2 HT leads together from the output. I am assuming this might make the spark very weak or non-existent ? would 12v coil make this possible.

2. If i convert to CDI i was thinking of using 2 CDI units sharing the sensor input ? again not sure if this is feasible.

3. On another subject i believe this engine uses 30 SAE oil.

4. Planning on using E5 unleaded fuel with some redex added, not sure if this is necessary i.e. the redex lead replacement ?

You can get CDI units for two cylinder engines. I have one by S/S though currently not being made and Minimag also have one for two cylinders, saves buying two and less bulky as well.

Thanks, i had a look at Minimag and they say that their CDI can be triggered by hall sensor or points so the dual unit for points only at the moment might be perfect. I assume i still need the capacitor across the points with a CDI unit ?.

It would be rather pointless (!) using points with a CDI system instead of a Hall effect device. However, if points are used the capacitor is not needed, as the points act as a trigger and do not see the inductive flyback voltage that can cause arcing in a conventional ignition system.

Andrew

Agree on it being pointless but its quick to get it running and nice and small then i can add the hall effect sensor later on when i figure out the timing. Not too sure how to wire a CDI to points as a trigger but hopefully instructions are provided

As I recall, my little box of tricks simply discharged about 3-400V stored on a 1/2 microfarad capacitor via a thyristor/power transistor, triggered by the points. I used my normal rev counter, but apparently on that particular unit the current to the system was linear and peaked at 1A @6000rpm for a four cylinder engine.

The main problem was the inverter ran out of power at high rpm or suffered from poor starting energy - the spark duration was not as long as the ‘ringing’ in the Kettering system. Basically, I needed a better inverter circuit than a couple of BC108/9 transistors and 2N3055 power transistor(s)… but it was far better than the Kettering system most of the time. There were, I believe, one (or two) switches on the unit which could be flicked over to change between the electronic or Kettering system. Electronics have moved on since the early 1970s, so modern ones should give no trouble with a slow(ish) revving engine.

The unit may be small but a set of points on a model of that size are very cumbersome. Most CDI ignitions can be triggered by just a contact which is what I use most of the time which is small, discrete and in many cases can be made as per the full size contacts. I've only used hall sensors on two of 15+ spark ignition IC engines that I have built.

It's also a lot easier to arrange for one of the contact points to be movable while the engine is running so you can advance and retard the timing

On the CDIs that I use you just make use of two out of the three wires that would go to the hall sensor. Looks like Minimag is the same may need to alter the cam (or at least it's position)that actuates the points as the CDI fires when contacts are closed

Edited By JasonB on 20/09/2022 07:18:42

Ok your last line is something i will check on with Minimag. Now to a more mechanical head scratcher, i am awaiting some info from the previous owner but while i do i have some thinking to do regarding the cooling setup. The engine mounted on a board and there is a large brass tank which is taller than the engine, there is a pipe coming from the bottom of the tank to the bottom of the crankcase and another pipe from the top of the tank to the cyclinder head. No pump etc. The pipe from the top of the tank connects through the tank and there is a pipe inside the tank with slits cut. I guess this could be a simple sprey allowing the water to drop down and cool back to the top of the water level ? that might make sense but how the water gets around the engine and up to the top of tank is a puzzle as there is no pump. I could get water into the engine just by the level of the tank but how it circulates is a mystery as im not aware the wallaby has a water pump only oil. Anyone seen a similar setup ? when i can figure things out i will post a photo.

Thermo syphon is what makes the water move, as the engine heats up what is in the cooling cavities the hot water rises and draws in cooler water from the bottom of the tank.

I doubt you will get much of a head to lift the water in the return pipe above the level in the tank so best to fill it upto the return pipe or a bit above

Thankyou....some real physics at work. For now what i have been doing on the Gannet with water jacket is manually pumping water with a garden pressure bottle 5L. This sounds very interesting so will give it ago and see what happens. Once i have tested all is well i will probably get a chinese kit with radiator etc.

JB,

I’m not understanding your comment re water level. The thermo-syphon system ideally requires a closed loop of coolant such that the inlet side of the radiator is hotter than the water percolating through the radiator, cooling as it goes. The difference in density between the engine outlet (hotter) will be less dense than that in the radiator (at the same level), so will rise in the inlet pipe. Practically the effective temperature/density difference will be much extended towards the lower parts of the engine.

The problem arises with water (cooling) distribution around multi-cylinder engines. There is little trouble with single cylinder engines without a water pump.

Some single cylinder barn engines simply used a large tank as as a cooling radiator and some had a cooling fan - when less coolant and a tubed & finned radiator was employed. Some then utilised a separate water pump, but usually combined with at least the same drive belt as the fan.

Earlier single cylinder barn engines simply employed a hopper above the cylinder head and relied on evaporative cooling ie needing regular top-ups as the water boiled away - if the engine was working hard. Not many stationary engines at rallies/shows are actually run hard these days, of course, often not even to the boiling point.

Even some multi-cylinder engines with pumped circulation used to suffer from scale build up at the rear of the engine. I’ve knocked out cylinder liners which have been almost completely devoid of any cooling, due to being virtually encased in lime scale deposits (I expect owners drained their engines in frosty weather and re-filled with temporary hard water - often not from the cleanest of supply, either).

My comment about water level was that I doubt there will be much chance of the water being lifted above the level in the tank to provide the "spray effect" that the OP mentions.

Most tank cooled engines and the models of them that I have made have the level in the tank at about the same level as the return pipe as you would really need the water bubbling and boiling to lift it to any head difference.

I was just explaining how the tank was intended to work and how a flow developes, as you say the passages in this engine may not allow for a good flow unlike the typical single cylinder engines that have a wrap around water jacket with few restrictions. It may well need a pump adding and maybe a better means of dissipating heat than a plain tank which will depend on length and speed of runs and if under any load. The reason the tanks are often tall or mounted on legs is to encourage a flow of water in the vertical or sloping pipe as it exits the engine

The other popular method with the open crank engines was to pump the water through a spray bar or head and onto a wire screen above an open tank which increased the area for cooling the water, I've done a couple of models with this, both used pumps, one belted off the crankshaft the other with a piston type pump similar to a loco axle pump.

Talking of loco axle pumps, does anyone know how Westbury arranged the cooling in 1831 that the engine was intended to power?

i dont think the cooling setup is good so i will be looking at adding a pump to force circulate the coolant. i will give it a brief run 30secs un-cooled. i would love to stick this in a 3 1/2 loco radio controlled.

I have checked with Minimag and their dual output CDI unit will trigger when the points open so thats good. Whats the general opinion on suitable oil for such an engine, i believe the spec was originally SAE30. I have some Castrol 10W-30 lawnmower oil for 4 stroke use, which i think would be ok or should i stick with just SAE30 ?

I am thinking that as being in the UK and the small size of the oil pipes pump etc that 10W-30 might be the better choice for initial cold starting.

Old Fordson TVO tractors had a semi evaporative cooling system, they worked best when they were at or near boiling, and had a big oval filler so you could fill them up from a bucket. fordson

When I were a youth I earned money to buy first motor bike by haytiming on farms in Yorkshire Dales. They only needed one tractor most of the year, but at haytime old wrecks would be dragged out to increase the fleet, so I've been paid to drive tractors older than me. The spring seat took some getting used to, try using clutch/brake when you're bouncing up and down over a rough field