OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Reel-Type Mowers MODEL 45 - 17 & 20 rebuilds

Hello all,

I don't see how Sid Bowditch was involved with the 45 at all!
Sid retired in 1958; the 45 was released in late 1967.

Sid's last projects were the 30" Queen and the ill-fated second
version of the Spincut, the 18" (with twin height levers!).

The closest progenitor to the 45 is the Bonmow 33, released in 1960,
also after Sid's retirement.

I don't think the frame issues on 45's can be attributed to a design defect.
The cracks are only showing up some 3 decades after manufacture, well after
the expected life cycle of a domestic lawnmower. In this light, the frame
is just plain worn out rather than suffering a premature fail.

It may be fair to say the single rail was a better design in not suffering,
or suffering less catastrophically, than the later twin rails in the way that
Grumpy described. I'd still have a twin rail machine any day - easier to clean
and inspect - particularly for cracks - and nicer to look at (in my view).

Cheers.
---------------------------
JACK

Thanks for those clarifications, Cyberjack. I had regarded the 33 as one of Bowdich's designs, and the 45 as a revised 33.

We probably differ regarding whether the twin-rail modification of the 45 was a good piece of engineering design, but given that people are still restoring and using them after several decades, they couldn't be described as an incompetent one.

Hello Grumpy,

It's a broad church we minister to
I would take it though, that we don't disagree with the 'idea' of twin rails.
After all, the rails just replaced the iron or steel rods, or tubes, that used to
connect mower side frames together since 1830. Perhaps a more robust specification
of the thickness or design of the channel would have made all the difference
down the rail road...

In any case, here's a story that you might find somewhat amusing:-
In a forum - possibly this one - many years ago, a member said this:

"I heard a rumor (sic) that the SB 430 and 590 are slightly different because both
brother's (sic) had different opinions on how it should work. Hence they still
have most of the same parts and cutting width."

That the Diplomats were released in 1976, Scott Bonnar retired in 1947 and sprung
his mortal coil in 1961; and Mick Bonnar did likewise in 1975, seems problematic
for the veracity of the rumour. If only the rumour involved Sid Bowditch as well; it
would have made perfect cow yard confetti.

All very interesting.
-------------------------------
JACK

I think the SB45 could have been built with rails in a way that I'd like, Jack, but in practice it wasn't. The deck or rails had two jobs to do, aside from the elementary ones of holding the frame together and aligned whenever the soleplate was removed, and keeping the engine from falling onto the reel. The first of these more subtle jobs was to restrain the engine torsionally, by providing a reaction to the pulsating torque delivered to the clutch by the PTO each time the engine fired. The second was to withstand the vertical and horizontal vibrational forces created by the engine. Nearly all small single cylinder engines are "half balanced", meaning that the crankshaft counterweight is increased from the size needed to balance the crankshaft itself, by half the weight of the piston, gudgeon pin and the little end of the connecting rod. The reason for half-balancing the engine in that way rather than fully balancing it by applying the full weight of the piston, little end and gudgeon pin to the counterweight, is that to do so would create a horizontal shaking force of the same magnitude as the vertical shaking force created by the piston. Hence single cylinder engines shake like crazy, and the best that can be done without using a pair of counter-rotating shafts or a reciprocating mass like the larger Briggs engines did, is half-balancing and letting the engine, its mountings, and the associated machine also shake like crazy. The mower designer's art, therefore, is to cope with that situation in a way that at least doesn't break anything.

In the case of most vertical crankshaft mowers, the solution is to attach the engine to a quite substantial disk: the mower deck. With a horizontal crankshaft mower, the traditional - especially among the British manufacturers - solution was a set of rather substantial cross-tubes with a bolt through the middle, forming an extremely strong, and given a sensible tube diameter, very rigid, engine mounting. Nobody I can immediately recall but Scott Bonnar chose instead to attach the engine to a pair of very flimsy open channel-sections. It doesn't look as if it would work, and sure enough, it didn't work. They turned an initially fairly competent design into a latter-day Victa 2 stroke: a uniquely Australian design the country cannot be proud of.

Hi Grumpy,

I totally understand exactly where you are coming from, thus my appreciation of the solid deck design over the twin rail concept. I could understand if they used material of the same calibar as the angle iron used on the Supercut as have you ever seen a Supercut with failed rails ? No.

The later model 45 was all about cutting costs and looking a tad more modern than the original styling of the 1968 45. The series 2 units certainly did look a bit more modern, but I'm sure that they never expected these machines to be around in 2015.

So taking that into account I guess the design did serve it's purpose at the time to be around for 10 years or so, but 40 years on, NO. Planned obsolescence has clearly failed if that's what they were thinking back in 1972 ~73.

How do you feel that sounds ?

Cheers,
BB

They do seem to have had some field problems though BB. They released that strange little balance weight to attach to the clutch, and they redesigned the engine-side clutch half, so it seems to me they had some inkling that all was not well in that system. The B&S engine did not vibrate any more (or less) than other single cylinder engines of the same size, AFAIK, but on their mower it shook things to pieces. However I don't know how many customer complaints they received, how vehement the dissatisfied customers were, or how old the mowers were when the complaints arose.

Taking a long view of it, they made - in earlier days - professional or semi-professional mowers that would last a lifetime. They probably made a conscious decision that they needed to move into home-use mowers, and progressively downgraded the products, more or less in stages. The twin-rail SB45 may have been a step too far to preserve their previous reputation, but it was less dubious a product than the 430 and 590 Diplomats, and as you say, asserting that a home-use mower with a ten year life is unsatisfactory, is not a sustainable argument. The world has seen many organisations decide to cash-in their reputations and move down-market at some point in their histories, and this is just one more example. The irritating aspect though, is that they appear to have saved so little money through their design compromises. On the other hand, people my age tend to say that about many similar cost savings, and if they had achieved what was probably their aim, and increased their volume by a factor of five- or ten-fold when they moved to the home market, the total cost saved could have been substantial.

At about the time of the SB45 the company management could clearly see that the mower buyers were favouring rotary mowers. They had to choose to retreat, or try to compete. At least they chose to try, which I think is to their credit.

Hello all

Getting the conversation back on track, I would like to thank
Mr. Jones for introducing this gusset plate method of extending the
already long and impressive life of some Model 45s that have succumbed
to frame rail cracking.

Mr. Jones, that colour choice is very much to my liking. It's, by far, the
best 'Bonnar green' I've seen. I'm no fan of the lighter shades of green.

This post, intended to showcase your restorations, is one that will help many
folk down the track, not just in frame repair, but in the high standard of
restoration of this iconic Australian design.

WE look forward to seeing the finished machines when done.

Mr Jones: you've got a thing going on.
--------------------------------------------
JACK

Posting a little progress on front roller. Think I may end up plastidipping these to add a black end cap? For ease of bearing size have opted for cutter bearings as the original roller shaft could be used.This can then always be converted back if required.

Hi Mr Jones,

That is the most gorgeous colour and probably the most accurate reproduction of the mid to late 1970's machines.

Can you source the formula make up for it and post it on here as that would make it so much easier for the rest of us and also future restorers that will want to replicate the correct shade of green for that period mower.

I have 3 of them awaiting restoration in that shade.

Cheers,
BB.

Hi Mr Jones,
That is an impressive looking Scott Bonnar. How many hours do you think you have in it? And what would you say was the hardest part about the restoration?

Hard to say xhall. Could be as much as 20-30 hours with an engine but there's always a lot of idle time waiting for paint to dry etc. The hardest part of the resto is hiding how much you really spent from your wife. Really these are simple well designed mowers and if you put them back together right you will hit few problems.

Some pics of progress. Need to flex the chain case a little for a better fit. Also posted a pic of the current running units we have at this point in time. Can post higher res pics as required.

Hello Mr Jones!

They sure do look purdy.
I particularly like the new bearing rollers.
A good idea using cutter bearings too.

I do have a question:
Is the roller tube interchangeable with an original one?
I ask this because of the issue of obtaining original roller tubes.

Supplementary question:
It would be nice to know that paint formula
If only you could remember that secret ingredient...?

Cheers and thanks for the update.
-----------------------------------------
JACK

CyberJack,
Same roller shaft as std but roller is oversize at 76mm. Hard to obtain std size of 70mm in a good finish. With plastic end caps and 70mm roller I can return to std but bearings in the front roller makes a better mower.
Paint.....I will return with the can to supplier and hope they can advise!!!

Thanks Mr Jones,

That's very helpful information.
Apparently shafts and end caps are available.
The issue is sourcing 70mm with good finish then...
It may be that your slightly larger 76 mm ball-bearing
design is a viable option for many restorers.

Cheers & Thanks.
-----------------------------
JACK

Hello Mr Jones,

Just wondering if you've forgotten about the request for the formula of the Apple Green that was used on your marvellous Scotty ?

This formula would help us all out immensely and save a lot of time and angst amongst all the restorers on our wonderful forum.

Cheers,
BB

Hi again Mr Jones,

I've just seen the last line on your last post which explains about the paint formula.

Sometimes I can't see the forest for the trees so please accept my apologies in that regard.

Cheers,
BB

How do rate the 6.5hp vanguard ? I was also looking at one of these for my 20" .

Hi Jim13,
Sorry to say I decided against fitting the 6.5 engine as I felt I may have been to much weight. The mower runs perfectly on 3.5hp and 5hp would kill it stone dead. The 6.5 hp may be more suited to a solid deck or a larger mower. Back to the paint! Protec advise the Hammertone 311 is no longer available so now its a hammerfin product. Have had a 500ml mixed and matched to the previous colour. It came out marginally darker but is close and is a much thicker product. Attached is the formula for 500ml. First item listed is the clear base followed by the tints.

Hi Richard,

On behalf of the ODK, Thank you so much for doing this as it obviously cost you a bit extra to have another 500 ml made up.

We shall keep this on file and recommend it to future restorers to use. It will be nice to have a standardised colour especially when none of the Adelaide paint manufacturers have any records on file dealing with Scott Bonnar in the 1970's.

I've exhausted all avenues here in SB's home state of South Australia so your colour formulation is as close as we'll get.

............again from all of us Model 45 enthusiasts at the ODK, Thank You very much.

Cheers,
BB.