Tuesday, 4 April 2017

Lawnmower Deck Repair ...

Late last week, I gave the lawns a first cut of the year.  It should have been done three or four weeks ago, the grass was long enough then and the weather not bad, but I hadn't managed to get around to it.

We've an old self-propelled petrol-engined mower, which makes the job very easy.   

It's lost its brand decals, but it probably came from one of the big DIY chains originally.  We'd bought it secondhand around six years ago, and in that time I've made several minor repairs including reconstructing the lever mechanism that controls the cut height and rebuilding the self-propel clutch, but generally it's been a great machine and starts first time every time even after standing unused over the winter months.

We've three sections of lawn, two of them quite large, but I can cut the lot in less than half-an-hour with this machine.  If you're ever thinking of buying a petrol mower, go for a self-propelled version - it's well worth the extra money.

Anyway, during mowing, I noticed the engine seemed to be shaking and moving around relative to the deck.  After I'd finished cutting the grass I took a good look at the mower.  

The cast aluminium engine casing has three fixing lugs with M10 tapped holes - the engine sits on a flange on the top of the deck and is secured from underneath with fitted bolts through reinforced mounting bosses in the plastic deck moulding.  Two of the three plastic bosses had completely broken off, and the engine was only being held down by the third, so no wonder it was shaking around.

At first glance the mower looked like a write-off, since there didn't seem to be any practical way to reconstruct the bosses with sufficient strength, even using industrial reinforced epoxy compounds, e.g. Devcon et al.

Luckily however, the threaded holes in the engine casing lugs are tapped through, i.e. they're not blind holes accessible only from underneath, so I decided I could fit short bolts from the top and then make up a couple of new brackets to hold the engine down onto the deck from above.  

I cut, bent and drilled two odd pieces of 3 mm aluminium flat bar I found in the workshop, using a blowtorch to soften the metal before making the bends with light hammer blows.

It was trial and error to form the correct angles between the engine mount and the deck surface, necessary so the brackets would lie flat on the deck when they were fitted.

I initially fixed the brackets lightly to the engine mounts and drilled through the deck using the bracket holes as a jig.  I fitted four M6 stainless screws and nyloc nuts to each of the brackets, and then fully tightened everything  to secure the engine to the deck.

10 year deck guarantee ?  I wonder when that expired ....
under the deck ...
the two new brackets ...

I'm quite pleased with the quality of the repair, and hopefully I've managed to extend the life of the mower for at least another season.

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