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Scott Bonnar Centenary Model
Drag this out over the weekend
I'm only calling it 'Centenary Model' because that is what is cast on the side of the mower Scott Bonnar most likely had a model for it
What year is it and what is the centenary for???
Ian






What is this on the side of the head

Hi Ian,
Information on the 'Centenary' is very thin on the ground.
From my research, I cannot tell you the reason for naming it the 'Centenary', but in came in 2 versions, a 16" and an 18" and was first introduced in 1936.
The 1st (early) (what we shall refer to as the Series 1) I have an advert for:

Unfortunately Ian, I don't have an image of your later(Series 2) model to show you, but your pics will be great for the archives.
Thanks for showing us Ian,

I was told it was for the Centenary of South Australia 1936
but never followed up to prove it
Ian

Hi Ian,

From all that I have been able to find, the Scott Bonnar Centenary was indeed named for the SA State Centenary in 1936. I have two of these and have had one running. They are very strong machines but the gearing is a bit quick. The knob on the side of the head is a decompression valve which is a common feature on Villiers engines of the time - Atco had decompression valves on the cylinder head for many of the larger engines until the 1930's. I believe these mowers were fitted with a variant of the Mk XI C (or XII C) Villiers - a 148cc engine that was introduced in 1931 and had a 53mm x 67mm. The Centenary mower appears to have been in production between 1936 and 1951. I am aware that Villiers were producing engines with fully covered flywheels as late as 1952.

I suspect that your machine, like mine, was produced post war from about 1949 - 1951.

Cheers,
Sir Chook

Hi Sir_Chook and Ian,

Well that is splendid news, we now know why is was named the 'Centenary' and many thanks for the update.
Sir_Chook do you have any pics of your machines and if so,
could you please post them here....?

I would suggest that the Centenary may have been the forerunner of the mighty Model 17 'Supercut', first introduced in 1950

Hi to Ian, Sir_Chook and ODK members,

Here is another pic of the 'Series 1' with the metal cooling shroud..Notice the change in the fuel tank position....

Hi All,

Just a couple of photos of my Scott Bonnar Centenary mowers. As you can see they are in "as found" condition. I have provided a view of the drive gear as well to show the chain and gear combination. They are numbers C647 and C538.





Cheers,
Sir Chook

Hi Sir_Chook, and ODK members,
Thanks for posting mate, what an awesome pair of mowers from circa 1936....awesome...and you said one runs..Just brilliant...
Thanks for posting the images, great for the archive,

Hi Deejay and ODK members,

I am glad to be able to share these machines with you all. From all of the sources that I have been able to find so far it looks like these two are probably from about 1949.

There are several key differences between the early and late Centenary mowers. In particular the engine is oriented in the opposite direction (i.e. the magneto is on the inbound side on the early machines and on the outboard side on later machines - consequently the cooling fans are on opposite sides), the clutch is different (lever operation versus rod and linkage), the fuel tank is located on the cross bar of the handle bars on the early machines and on the engine cowl on late machines, the drive cover is tin on the early machines and cast aluminium on later mowers. The last detail whilst not a major change to the mower it (and the aluminium cooling fan cowl) does give a bit of a clue to the date of manufacture. The use of aluminium in manufacturing became quite prevalent in the late 1940's. With the end of World War 2 the need for vast amounts of aluminium for aircraft and other military uses also came to an end, thus resulting in a large amount of aluminium being available for other uses.

With respect to the lineage of successor models, the Supercut shared some key design elements such as the handlebar design, clutch design and operation, crank start and other minor details. In some respects the Supercut could be considered the refined version of the Centenary.

Cheers,
Sir Chook

Hi Sir_Chook, and ODK members,
They can be dated by the engine flywheel number some are easy to read but I don't how to read this one
My number C552 is between your two
Ian

Hi All
Has anybody come across 'Ron Wiley' he runs the Australian Villiers records and has lots and lots of info on Villiers and can date all Villiers engines he also does Cooper engines
Anyhow this is what he sent me on my Scott Bonnar
Ian
Hi Ian.
Your Scott Bonnar mower; it is a Century model that came out in 1936 to celebrate the first one hundred years of SA. It was replaced by the Super Cut in 1950; I used to have a Centenary # C831 dating from 1949 so not that many were made in 14 years. The magneto with a date of 12/6 (December 1946) means you have a 1947 model. The engine is a 147cc Mk.11-C that first appeared around 1931/32, the 11-C was replaced by Mk.25-C in 1949. My centenary has a Mk.27-C q 25-C minus the metal cowl, it had a cast iron flywheel and fan on the drive side crank with cast alloy cowl to direct air over the cylinder and head.
Regards,
Ron

Hi Ian and ODK members,

The month/year dating system on Villiers flywheels is only able to be used on post war engines. What needs to be understood though is that the date only provides an indicator of the year of manufacture of the engine and it is only relevant where the flywheel has not been replaced or exchanged. Both of the flywheels on my Centenary mowers are dated 10/7 or October 1947 so it is possible that these were from the same shipment of engines. Given that Ian's flywheel is dated December 1946 and his Centenary is numbered between both of mine it raises the question of when were these mowers actually assembled. The answer to this cannot be easily answered and can only be assumed to be somewhere between 1947 and 1949.

Cheers,
Sir Chook

Hi Sir_Chook and ODK members,

Here is a little snippet of info on SB centenary mowers: (Courtesy of Willingworker (Grant Simpson)

Letter from Malcolm.C. Bonnar to Claude Dewar (Company Secretary)

18th July 1939

Dear Claude,
We went to see the Briggs and Stratton 4 Stroke mower at Knock and Kirby's.
Reg Marsten (Sydney Manager) was disgusted with Sid Bowditch's attempts at the 4 stroke on the Centenary and said Sid was too old fashioned and behind the times. I told him strongly I would not stand such criticism of anyone.
Yours,
Malcolm.

So it seems that SB were at least trying to place a 4 Stroke on the Centenary way back in 1939 before WW2.

I know Knock and Kirby's (Wollongong) that was my first job as a tool salesman
Ian

HERE IS A SCOTT BONNER I PICKED UP YESTERDAY, VERY SIMILAR, DIFFERENT EXHAUST

Hi bunipper,and on a good score there mate, and a catcher to go with it....
Are you contemplating doing a restore on it?
It would come up a treat!

not sure as yet, its in working condition, so I will keep it dry and give it some thought. never even seen or used one of these before. so its something new. I will either restore it or sell it. ????

is it worth while as a resto project

cheers

chris

Hi Chris,

Having had a look at your photos and those of my two mowers I do not think that they are different. I have a sneaking suspicion that the cylinder head and exhaust have been reversed on yours at some stage. This is very easily done as it is only a few nuts to undo. From all of the photos that I have ever seen of these mowers and the two in my possession all have the exhaust and decompression valve to the front and the carburettor to the rear.

If you have a go at starting your Centenary take care as it could take a few goes and be careful of the crank handle when the engine fires. Once running it should pull along like a train.

Cheers,

Sir Chook

thank for that information, I will let you know how it goes

cheers

chris

Hi All,

Just a small addition to the Centenary story. Please find below some pics of a recent auction item - a Centenary with an Amplion engine. It should be noted that the Amplion engine was a copy of the Briggs and Stratton Model I. An interesting machine and one worth preservation.

Cheers,

Sir Chook