Jim. You can do your own thing with the exhaust on the Wyvern, my version shown in the picture, I used a Hall sensor for my ignition by Minimag Link , however you can use points and coil ignition.

I run my Wyvern on petrol, you can use propane but I am not up on that method but it would be worth looking into.

Hope this helps.

MichaelR.

I have a ollection of engines,gas with hot tube ignition,gas or petrol with low tension ignition, petrol engines with HT magneto ignition, petrol engines with low tension ignition. they range from a 3/4 ton National to a Stuart 600. If you require good runnng and starting then go for petrol, Propane gas which is the best substitute for coal gas requires a lot of fiddling to get the engine running ,plus a rubber diaphram old type gas bag/regulator,I have 2 gas Gardeners with hot tube ignition,the gas setting is critical there is no rich or lean running with a gas engine,the mixture must correct.Regarding ignition,the normal type of ignition for the small vintage open crank engine was a battery powered trembler (buzz) coil with a wipe type contact mounted on the side shaft. Stuarts on their 600 (similar in style to the Wyverne) engine used coil and battery and offered at lot extra cost a magneto ,mounting bracket, and 2:1 chain and sprocket drive from the side shaft ,the magneto was geared up to engine speed to improve the spark but of course there was a "dead" spark after two of the four strokes,quite common practice at the time, the Stuart was offered as a gas or petrol engine.The buzz or trembler coil is a Ht coil with an attached pair of contacts,when electricity is supplied to the coil contacts they "buzz"and produce a shower of sparks all the time the electric is switched on,the wipe contact mounted on the sideshaft is simply a rotary switch to supply current to the coil for a short period to fire up the spark plug. The trembler coil has adjustable contacts with a built in condenser and is usually housed in a small wooden box mounted under the engine. The trembler coil is probably the most appropriate style of ignition for the Wyverne, As for fitting a modern system,its up to the owner ,its their engine and they can do what they like,though I feel its like fitting LED lights to an Austin Seven. Replica trembler coils are available.

Jim, I have some info that may help you, drop me a message and I'll send it over….

Edited By Henry Brown on 26/05/2020 13:36:58

I produced a quite acceptable exhaust for a motor cycle by drilling two sets of holes, equal in total in cross sectional area to that of the pipe, and separated by a blanking plug. This allowed the gas to pass into a small expansion chamber to by pass the plug and back into the outlet pipe. It sounded quite like a post WW2 motorcycle, so the owner was well pleased.

Another silencer for a single cylinder engine was simply a 2 pint Castrol oil tin clamped by the neck to the end of the exhaust pipe, with a series of holes drilled through the base of the can.

A lot of single cylinder stationary engines seem to exhaust by a short pipe into a smaller version of two frying pans bolted together, with a series of holes drilled around the rim of the base of the outer one.

Stationary engine preservationists will no doubt be able to provide a photo of such a silencer.

For a model engine, the two parts could probably be turned from bar, and the necessary holes drilled for outlet and fixing the two halves together.

Howard

The motor cycle exhaust was a double ended megaphone, externally.

My object was to reduce the energy in the exhaust without producing too much back pressure, which would increase pumping losses. The slower the gases can expand, the less the "bark" will be. The objective was to maintain a constant cross sectional area, and to allow expansion. But the extremely simple exhausts for the small stationary engines are unlikely to allow this, if they are to look prototypical.

These are simple exhausts., Higher frequencies can be absorbed, and lower frequencies tuned out, but these methods require space and weight which is not not always acceptable.

If you want further detail, PM me.

Howard