OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Walk Behind Lawn Mower Frames Question On Scott Bonnar Cylinder Mowers SB45 Restoration project

Not to start an arguement, but I aggree with Grumpy. However at the end of the day it really comes down to what you want to use the mower for and how far you want to go with the restoration.

I myself have a Scott Bonnar 45 painted up in Rover Red, with a few late model Rover bits including the catcher. But at the end of the day I wanted a reliable reel mower that presents well. The purist will soon tell that it is not a Rover 45

As for repairs to your chassis, I certainly would not be Arc welding it, as the inherant distortion or risk of poor penetration could be future problems. If it was mine I would be having a go at repairing that Rail, but leave the roller and sold plate attached to chassis while welding to gain as much rigidity in the chassis whilst welding it. Clamp a scrap piece of solid material to the rail, that is the same length to hold it straight. Then I would fit a piece on the underside of the old rail. The piece should not be any thicker than twice the thickness of the rail as you will not get a strong weld and require to much heat, causing distortion. The piece will only need to be stitch welded, but allow time for the rail to cool between each weld and work from the middle out. Tou can then weld the crack on the outside and grind it back.

Overall you may get a slight twist on the chassis and you would have to way up if this is worth the risk, or how critical you will be on the finish the mower gives. I have seen new 17 inch Rover Chassis on Turf Machinery website, but dont know if you will get a 20 inch. Plus the chance of getting one 2nd hand in WA is quite slim.

My Briggs has a deep tank and was the original Orange engine on my 45.

Thanks for that Jarrad. For a use-it-but-don't-collect-it mower, which is probably all this one can ever be now that its authenticity is lost, repairing the rail can probably be done with only modest distortion using the technique you have described. The key seems to be in four points: start from the middle, weld less than 1/4" in each stitch, let it cool properly between stitches, and make each successive stitch at a point diagonally opposite from the previous one, on the plate you are welding in. When I was a kid a good tradesman welder boxed in my car chassis that way to increase its torsional rigidity. Laying it on flat concrete before and after, it only twisted about 1.5" on a diagonal across the complete chassis. However it was a long job, doing it that way. (On that vastly larger car chassis, he used 1" long stitches, and left 1" gaps between them, to minimise heat input.) In the case of the mower frame you can watch the twist after each stitch, and use feeler gauges to measure it under the corners of the frame on a flat bed plate, if you want to get the bad news progressively instead of all at once at the end.

Thank you for the information that you have a deep-tank original engine on your SB45. That seems to make it highly probable that Steve's SB45 still has its original engine, and is a fairly original mower under its disguise.

Okay, now we have it's identity sorted (well sort of!), I think I have decided what to do.

Given the mowers lack of identifying features and therefore lack of collectability I will restore the mower to a useable and presentable condition without worrying about authenticity.

As I don't know how well it will mow because of the twisted chassis I don't want to spend too much money on it so this is what I plan:

1) Strip down to chassis but leave soleplate and roller attached and repair broken rail as per Jarrad's suggestion. Jarrad, you mentioned you have the equipment and you seem to know what you're talking about so would you be keen to have a go at this for me?

2) While the engine is off, determine the condition of crankshaft and keyway etc.... and therefore determine the servicability of the engine. If it seems okay then I will give the fuel tank and carby a good clean and service and see how it runs. If not I will source a new engine, probably a 3.5HP B&S from eBay for $275.

3) When the chassis is repaired I will have the blades sharpened and then put it all back together with a new clutch assembly.

4) At this point I will see how well it cuts. If it cuts well, I will strip it back down and sand/prime and paint and then replace all sprockets, chains and whatever else needs replacing. I will then have a functional mower that should last for years. If on the other hand the cut is no good due to the twist in the chassis, I will then have to see what else can be done to sort out the twist.

What do you think? I know it's not ideal, but considering the current condition and missing ID I think this is probably the wisest think to do.

Steve

It sounds like a viable program Steve, but you can assess the amount of chassis twist with a simple gauge before you put the mechanical parts back on. If the front and rear rollers are on, and the soleplate is in position, you can measure how far out of true the frame is with a piece of half inch square steel with a screw through it. You can get details in this thread:
https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=33428#Post33428

Provided the twist is small (say less than 3 mm with the alignment tester) the mower should perform adequately for almost anyone but a greenskeeper. So, you will know whether it will be satisfactory or not before you even reassemble it. Then if the frame warrants it, assemble the mower. If the crankshaft seems OK, tune the engine.

I wouldn't rush into a new Briggs engine, if the original one is sound. The new one will probably be Chinese, and the quality outcome is unclear at this point. The first few years' production seems to have been erratic, and we don't have enough recent data to estimate whether they have their act together yet. Hence the old 80202 looks like a preferable choice.

Well it looks like a good plan of attack has been reached that may have a satisfactory outcome, Steve.
Please post some pics as you go along as this would be good for the OutdoorKing archives. It may help another member with a rail fracture on their Model 45.

No probs Steve

My mobile number in in my profile. Give me a ring when you are ready.

Jarrad

Thanks Jarrad, I'll get in contact when I'm ready see what we can sort out.

Deejay, yes it does have a catcher.

Jarrad and Steve, if you can take a series of pics as you make the repair, they would make an excellent extension of this thread for the Outdoorking reel mower archive. We've had reports of broken rails on SB45s before (it is a common failure) but have never documented a repair process.

Hi grumpy, please read my post above....

Oh well, what can you expect before 8 a.m. on a Saturday? At least we both asked for exactly the same thing.

I'm hoping we can document the clamping (do you use a long lateral clamp across the side plates to close up the gap in the broken rail?), the way the reinforcing plate fits (welding room around the outside, clear of the flanges?), and several progress shots of the stitch-welding, showing the pattern of welds, and the distance between welds (usually equal amounts of weld and space, but let's see Jarrad's approach). Then some pics of the alignment check with the gauge would be good. If it were me I think I'd do the welding with the front and rear rollers in place, and I'd check the alignment after the first pair of stitches, then every few stitches afterward. If the process is done correctly you should find it is pulling itself back straight whenever the pattern of completed stitches is symmetrical. If I'm doing it, on the other hand, it's out with the angle grinder after the first couple of stitches because it isn't precisely correct.

Yes grumpy...I'm always a bit doughy at this time of the morning as well!!
Mate, I think that a well documented thread will be invaluable as an archive....fractured rails seem to getting more prevalent on the late model Scotties...only a matter of time before the Rover 45's start doing the same.

Referring to an early post in this thread, it was said that the date of Steve's engine, in 1981, was after Rover bought Scott Bonnar. In the remainder of the thread it has been assumed that a 1981 engine could not have been fitted to a green Scott Bonnar mower. This implied that the cowl on Steve's original, orange engine cannot have been the original cowl. I have been reading the archives and it looks as if this was wrong. The issue is covered in this thread:

https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showgallery&Number=14247


From this history it appears that Steve's engine probably still has its original cowl, and the mower was very likely made in 1982. If you want to Steve, you could inspect the cowl closely to verify that like the rest of your engine, it is orange underneath the black paint.

Gee, grumpy, I had forgotten my own post on the history; that was a guy in Brisbane (Rover) who put me onto the guy in Mildura. I have been looking for that info for ages.....that was posted way back in '09.....my memory is not as good as I thought it was!!
I shall add that info to the SB history in the super forum.
It just goes to show that there is a lot of info in the archives, if you just know where to look!

Grumpy, there are definately signs of orange on the engine cowl, you can see it in the photos I posted earlier. I guess this is proof that Scott Bonnar were still producing orange engines in 1981 as discussed in the post you pointed to. If this is the case then it is possible that this is the original engine for this mower.

With regards to the engine, I am not confident that it is in a servicable condition. I still haven't removed the engine but I was having a look at it last night and when I turn the crankshaft forwards there is a horrible noise coming from inside the engine. It sounds like loose metal parts! Also, I don't seem to be able to turn the crankshaft backwards. I will let you know more when I have the engine removed.

Steve

You can't tell what is happening until you separate the engine from the clutch, Steve. There seem to be problems in your clutch, and that could mask what is going on in the engine.