20th June 2017
We received a call saying that this mower had begun throwing its drive belt off and the owner had refitted it a few times but then the last time the owner stopped to refit it they noticed one tyre has moved forward and actually contacted the bodywork for long enough to wear a groove around the tyre.
So we set off to collect, not really knowing what to expect, but with thoughts revolving around a physically broken gearbox, securing bolts fallen out or snapped or broken axle brackets, also hoping that it will actually be possible to push it to the truck in order to winch it on, it definitely couldn't be driven anymore.
On arrival, after a reasonable walk it was plain to see the left hand axle bracket had given out completely, the axle now sitting in front of it and jambed there solid. The machine still had its powered grass collector attached so we dropped that off and then removed the cutting deck. Finally with a bit of jiggling and a bit more brute force we got the axle back under its bracket, at least it was now pushable so we moved our truck as close as possible and pushed the machine to it, very glad I had asked Mandy to come with me!
Back at the workshop it didn't take long to get it up on stands, get the wheels off and unbolt the gearbox, now the reason for the catastrophic failure became clear, the bracing bar that fits to the front of the gearbox to transmit the turning forces from the gearbox to the frame didn't have a bolt fixing it to the gearbox! Meaning the gearbox had been transmitting all the torque from turning the wheels through those two axle mounting brackets, twisted them downwards in reverse and upwards in all forward gears - no wonder they snapped!
Once the gearbox was cleaned down we could see the threads had been worn out of this bracing bar bolt hole, which is a bit of a problem, there was also an untapped drilling on the top of the box which I thought we could use so I tapped this out to m8 but wasn't happy to rely on this smaller bolt to stand up to all the forces on its own. My only option was to drill out the original hole and thread it at 7/16unf which I did succesfully, I then made a v bracket to fix the now extra fixing on top of the gearbox to the anchor bar.
I then modified the bracing bar to fit, the hole now needed to be bigger to take the larger bolt, it also needed an additional hole to take the extra bracket as below.
With any luck this should stand up to any use it may be put to, I have now welded and reinforced the axle brackets, given them a coat of paint tonight so its dry and I can reassemble it in the morning, update to follow.......
So today the repaired and strengthened axle brackets are refitted along with the modified gearbox brace.
The support brace has undergone another modification since yesterdays picture, once assembled on the front of the gearbox I realized the top of the v bracket was just going to contact the lower edge of the drive belt which would cause premature wear, so decided to weld the extra bracket to the the support brace instead of it being a bolt on part, as below.
Now I can refit the gearbox to the tractor, which went in very well except for a bit of levering to get the bolt holes to line up in the axle brackets.
The rope you see in the picture is looped around the spring which is part of the deck lift assembly to add a bit of assistance when lifting the deck and had to be removed in order to get a hand past it to fit the top bolt for the gearbox brace where it bolts into the mower frame, it was later refitted by means of a metal bar levering on the rope to pull the spring back in place.
Next was to reconnect the gear selector and brake rod and refitting the deflector under the gearbox.
All that remained now was to refit the drive belt, check the adjustment and operation of the clutch and brake, refitting the deck once a few holes have been patched and welded.
This picture is just to show the damage caused to the tyre during what was a very short space of time and only travelling at grass cutting speed. It will be a constant reminder for the owner of the day the gearbox almost parted company!