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

Hi All,
Been looking for a 20" model 45 since the last reno and was lucky enough to pick one up last winter. Condition was fairly poor and without and engine but reel and sprockets appeared to have a bit of life left in them. My son also had another 17" so we have decided to restore them side by side with a view to them both being used regularly. Have posted a couple of pics of the 20" for comment.

Hi Mr Jones, Unfortunately we did not get a chance, from the pics, to asses the sprockets and chains..... but even without pics, I can give you this advice....If ANY of the sprockets have really pointy teeth, it is time to replace the sprocket and the chain that drives it.

the front rail is substantially cracked, in fact its in two pieces!

Certainly looks that way from my eyes as well!

Thanks Deejay,
Will add a picture of sprockets when mower is re-assembled hopefully soon. Thanks to those who noticed the small crack in the rail. Have attached attached a pic of the fix. Would also like any ideas on a ball bearing front roller for the mowers. This is the one thing that lets down the mowers a little. Have looked at installing a conveyor roller? Would appreciate any suggestions as I think I have seen at least one on the site before.

Hi Mr Jones,

Can you please take some more close up photos of all around the repaired rail area ?

Cheers,
BB

As parts are back from paint here is a better picture of the repair. A little overlap on inside edges but wont be seen from height and with engine installed.

Hi Mr Jones,

The more I look at that gusset welding job the more I like that idea. It's most unintrusive.

I have to ask, what formulation did you use for the colour or was it custom mixed at a crash shop ? As it looks pretty much spot on for the mid to late 1970's mowers.

Cheers,
BB

Did you weld the cracks in the rails as well as fitting the gusset plate, or just fill them with bog?

The way the gusset itself has been attached seems to give good prospects of avoiding heat distortion of the frame. How did you restrain the frame while welding, and/or gauge the frame for straightness after the repair?

The process was to first straighten the rail as best as possible with a press done very carefully. Next the gusset was tacked into place to secure the shape. This was then followed by grinding out the crack and carefully welding them up. The gusset was then fully welded in place and some light grinding for a decent finish. Hammered paint takes care of the rest. Have to say happy with the result but haven't put an engine on it yet. The paint has been a bit of a nightmare. Its a Protec 311 hammertone mixed to a sample taken from under the handle grip of a model 38 edger. Its close but the first coat had a few runs and had to be sanded back and repainted. It also took about a week to be anywhere near hard so you could handle any parts. Wont be using it again as its too thin in the can.

Hi Mr Jones and Grumpy,

Well I'd say that you'll never have any issues with those rails again as that's probably been the best remedy that I've seen done and as you said you'll never really see it unless you're a roller.

Did you by any chance get the formula that was used to make up the colour ?

Cheers,
BB

i just love how a sandblast and paint brings these objects back to new from such very old tired worn states.

Will respond on paint but need to visit the supplier for code. Will follow up. Have posted a bit of progress so far. Jnr is a bit ahead on his 17" but we need to tackle the front roller problem. As shaft is 5/8" could use a cutter bearing and machine some end caps to use with original size roller tube. This would let us revert to plastic end caps if required. Would prefer to have front rollers with bearings. Have also been able to source a 6.5hp Vanguard engine brand new at a very reasonable cost but I am a little concerned that it will be too much for the 20" mower frame. Should run at a little over tick over though! Thoughts on roller and engine appreciated.

Generally, the greatest demand on the drive train of a reel mower, is when mowing up a steep slope or powering it up a ramp onto a trailer or terrace. I agree that if you only limit your ambitions for climbing ramps and kerbs to whatever stalls the engine, the 6.5 hp engine could be a problem.

In normal mowing the engine weight and the rotating inertia are important, but within reason, extra power in itself should do no harm. The drivetrain can only be harmed by too much engine power if the mower meets resistance and therefore the drivetrain has to transmit all of that power. If you pick up a bolt between reel and bedknife for example, the engine will be stalled immediately, more or less regardless of its power, since the governor will not even have time to open the throttle before all rotation ceases. The factor which will cause damage in that situation is the momentum of the rotating parts. Hence in routinely mowing flat lawn, the main thing to avoid is an engine with a cast iron flywheel, rather than one with a moderate amount of excess power.

Hi Guy's,

These two machines are looking better and better every time I see them, especially with that fabulous colour which makes these machines so striking in appearance.

Is that a brass height adjuster or a painted die cast version ?

Really looking forward to the formula of the paint.

BTW I'm wondering if making those gussets a bit longer would be a strength advantage or would it just place more stress on the weld joints securing the rails to the side plates ?

Cheers,
BB

in regards to power, even the 1979 model original 3HP on my 17" seems excessive. going up the rise on my front lawn it has no hesitation and on the flatter back lawn i use the clutch to get it moving but then its momentum keeps it rolling just fine. thats all on half throttle too.

BB, fwiw suggesting a change in the gussets at this point of his build(post weld, post paint, post assembly) only puts more doubt into the repairers mind as to the best guess anyone has ever taken so far to repair a twin rail SB. Only time will tell.........

My thoughts are the same on the engine. An original 3hp 80202 with auto choke is high on my shopping list for restoration and this would be plenty of power for a 20" on flat ground. I may initially fit my 3hp 90112 for the purpose of a test drive but hard to turn down the 6.5hp for the price. Jnr,s adjuster is a brass item and would assume came from an earlier solid deck.

Hi Mikeo,

I'm not for one moment suggesting for Mr Jones to jump ship at this point, it was merely an observation for any future repairers to consider as this problem would be encountered by around 8 out of 10 17 inch machine owners and 10 out of 10 for the 20 inch units.

This topic has come up so many times on this forum that every improvement can only be a step in the right direction.

Cheers,
BB

the materials in these machines have a design life thats for sure. if only Sid had some FEA.

I have a spare 80202 that i intend on cleaning up and returning to new having run the other 80202 on the 17" for a couple of weeks now, they are impressive engines!

I don't think you can blame Sid Bowditch for the design weaknesses of the twin rail machine, I believe he only designed the single deck version, which was quite good from the fatigue life point of view. To critique that design we'd need some pictures of cracked single decks.

The source of the problem with the twin rail design may have been vertical resonant vibration of the engine and rails as a mass-and-spring system. That is not a mistake Sid seems likely to have made, particularly if the rail resonance was the source of the excessive vibration so many twin-rail SB45 owners complain about. There must have been a reason for the complex construction of the single decks, and overcoming a resonance problem observed during product development may have been that reason. Of course if cracks developed the vibration would have increased in amplitude.

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?