OutdoorKing Repair Forum Forums The History Forum Model Histories SCOTT BONNAR Models MODEL 40 - 14" Reel Lawnmower - c1961

Hello ODK History Lovers
The Model 40 was a 14-inch self-propelled reel mower made by the Scott Bonnar Company.
Released in about 1961, it would be made in petrol and electric variants. It would be the
first Scott Bonnar to introduce the Cordless-Electric, a battery-powered machine.
The Model 40 would be made in Cordless, Mains, and petrol-powered versions.

We should not underestimate the importance of this small reel lawnmower. It sold in
volume and it was a good design. It corrected the defect(s) of the previous 1953 -
Model 19 - design; in that that older design had an 'open' transmission, with chains
exposed to dirt ingress. But ...

Most importantly, the main defect of the Model 19 is that it offered no primary clutch
to isolate the reel for engine starting. The Model 40 corrected this, and it would feature
a new rubber-friction Primary Clutch [for isolated engine starting], and a separate
landroll clutch. The small, domestic, Scott Bonnar had come of age.

This machine copied the 'new theory' of the larger Model 33, released a year before,
in 1959. It is not unfair to say that the Model 33 and Model 40 would be the precursor
models that would morph into the highly successful Model 45 Range of 1968.




TO BE CONTINUED ...

PART TWO - Models & Specification
This was a highly successful model, taking up design elements from the larger
Model 33, and vastly improving on the original post-war, domestic Model 19.

This was a modern machine, with fully enclosed chain transmission, and a
unique-to-this-model, primary friction clutch. It had a hair-trigger operated
plate landroll clutch.

This was a 14" machine with steel plate frame, 6-blade reel, and a single piece
rear roller. No differential action on this model.

It was, ultimately, made in three variants: petrol, mains, and battery.
MODEL 400119 - Mains Electric
MODEL 400215 - Battery Electric
MODEL 400418 - Villiers 75cc Petrol Spec. 2015X
MODEL 400426 - Briggs & Stratton Petrol 60102 0302-01

PETROL
The petrol machine was fitted with a small Villiers four stroke.
It was advertised as having 'Whisper-Quiet Power'.




TO BE CONTINUED ...

PART THREE - Models & Specification - Electrics
Special mention must be made of the electric variants.
Yes, the Mains Electric version reflects Scott Bonnar's historical commitment to
electric lawnmowers. But the Battery Electric was something revolutionary and special
... perhaps before its time ...



TO BE CONTINUED ...

PART FOUR - Transmission

The Model 40 Petrol machines had an unusual transmission arrangement.
It was a great improvement over the Model 19 Bonmow - to offer dual clutches.
I point out at this juncture that the Model 40 used two petrol powerplants in
its history: originally a Villiers 4-stroke; then a Briggs and Stratton 4-stroke
[that would later be used on the first 14" Model 45].

For reasons - that are not clear - Scott Bonnar decided on not using the 16"
Model 33 transmission design released a year or so before. Instead, the primary
clutch was of a steel drum energised by making contact with a rubber wheel bonded
to a crankshaft boss. This clutch was encased in a safety housing and engaged by a
small lever [see 5a below].

Note that the instructions said that the lever was to be left disengaged when not
in use. I guess this was to prevent 'flat-spotting' of the rubber drive wheel during
storage.



Of particular interest, also, is the chaincase arrangement.
Note that there are only two chains. The Model 33 [and Model 45] used 3 chains
[or 1 belt, two chains]. How was this possible?

I feel that this may explain, somewhat, the different preferences of the 14" and
16" designs. It was clever. The drum and rubber wheel ['friction roller'] provided
a significant reduction ratio to the output shaft [5], that permitted the designers
to remove the need for an extra intermediate sprocket and chain, as used on the
Model 33.

The Model 40 did adopt, however, the reel bearing carriers and setting method of the
Model 33. A good system, but a little more awkward for setting than the one that
would be adopted for the Model 45.

Finally, I point out that The Model 33 and Model 40 had a friction plate clutch
mounted axially to the landroll. The Model 40, however, moved the engaging mechanism
into the chaincase - an improvement.

PARTS GALLERY



TO BE CONTINUED ...

PART FIVE - Operator Manuals
A copy of the Operator Manual for the Petrol Model 40 was supplied to me by
David E in late 2015. Many thanks for David taking the time to do this.



A copy of the Operator Manual for the Cordless Model 40 was supplied to me by
Paul C in late 2015. Many thanks for Paul taking the time to do this.

PART SIX - Parts List - Mains Electric

PART SEVEN - Parts List - Cordless Electric

PART EIGHT - Parts List � Petrol

PART NINE - Analysis & Comment
The Scott Bonnar Model 40 was the second post-war 14" residential lawnmower
made by this great Australian company. It improved on the first, Model 19,
in that the Model 40 offered a primary clutch for starting, and a fully
enclosed transmission cases. This was a well-built machine of quality that
made "lawn-care 'child's play".

What the Model 40 took from the Model 19 was the brilliant hair-trigger
secondary, landroll clutch. Otherwise, its main design cue was the 16"
Model 33,released in about 1959.

The biggest criticism I have of the Model 40 was the lack of a split rear-
roller with differential action. It is completely understandable, though,
why that had to be the case. This was a machine that had to be priced within
a specific market segment.

There was little change in the model over its production lifespan.
All machines would have a colour change to Hammertone paint (over the original
aqua green). The petrol version would receive a change of engine - a Briggs 2 hp
60102 - in its later years. There would also be a change to a folding-chrome-handle
design on the Cordless and Petrol versions.

The model 40 sold well, with many example surviving today. The biggest challenge
at the moment is the finding of replacement parts - particularly the rubber drive
for the primary clutch. This is not an insurmountable issue.

I have argued in these records that the early-to-mid domestic range of Scott Bonnars
lacked scalability - with three cut sizes involving three different design approaches.
This would be, finally, corrected with a single scalable design, the great Model 45s
of 1968.

The rest is history.

[1] MAINS ELECTRIC
The Mains Electric Model 40 was made for the duration of the model range.
Little change appears to have been made to the design. Note the aqua green and
Hammertone finishes, and the three separate maker's plates on the motor cowling.
A great design. These are auction images ...






On The ODK site:-
https://www.outdoorking-forum.com.au/forum/ubbthreads.php/topics/72890/Scott_Bonnar_Model_40_Mains_El.html

[2] CORDLESS ELECTRIC
The Cordless Electric Model 40 was a bold move by Scott Bonnar for the day.
Certainly, they were observing and then following 'trends' happening overseas.


SOURCE: 2015 auction image

The following images come from the Paul C Collection.
Note the Scott Bonnar branded battery charger...





https://www.outdoorking-forum.com.au/forum/u..._Bonnar_Model_40_Cordless.html#Post68960
https://www.outdoorking-forum.com.au/forum/ubbthreads.php/topics/38205/1.html

[2] PETROL POWERED
The Petrol-powered Model 40s were powered by a 75cc Villiers Lightweight,
and then a 60102 Briggs & Stratton.

The first images are from a 2015 auction, and they show an early Model 40
with aqua green paint. Note the round fuel tank and compare it with the
squarish one in the advertisement in Part Two and the Operator Manual in
Part Five. All Model 40 Petrols I have seen have been fitted with the round
tank. Also note that the early machines did not have folding handles.




The next set come from a 2012 auction and they depict a later machine with
Hammertone paint and chrome folding handles.



The final set also come from a 2012 auction. The chassis has been repainted,
but I believe the 60102 2hp Briggs is original. That engine would later be used
on the 14" Model 45. Again, folding chrome handles.





https://www.outdoorking-forum.com.au/forum/ubbthreads.php/topics/33702/Re:_Scott_Bonnar_Mk_40.html
https://www.outdoorking-forum.com.au/forum/ubbthreads.php/topics/18917.html

SCOTT BONNAR MODELS


Would you like to comment on the Model 40?
Simply create a new topic in the Old Soap Box HERE.