Last week, returning from our lengthy road trip south, My youngest boy told me "I think the hedge cutter motor has burnt out Dad". Two days ago we were child minding again so I brought it home with me. This morning I decided to investigate.
There was no obvious signs of anything having burnt out and the fuse in the plug was still OK - rang him and he had not fitted a new one. As I have an RCD on my garage plug I risked plugging it in and briefly pulling the trigger. It made that sort of buzzing noise that stalled electric motors often make and I could see the armature turning just a little.
OK. That may mean that it's a mechanical rather than electrical problem so I whipped the cover off the bottom of the gearbox:
Actually this picture was taken as I was reassembling - hence the liberal quantities of moly grease. I tried to move the gears with my fingers and a big screwdriver but it was solid. I thought if I removed the big (13mm spanner) nut on the end of the spindle and the two Allen bolts holding the blade bar in place then I would be able to strip the gears and eccentric blade drive hub out of the casing.
The two Allen bolts came out easily but the nut would not move. It seemed ridiculously tight, but why? What am I missing? Is there some locking tab? Special locking washer? Nope! Ok, have a cup of tea!
Sitting with my cup of tea I thought "with the blade bar bolts slackened if it's the blades that are jammed it should now spin?" so I triggered the motor again (No, it was not plugged in whilst I was working on it!) Still jammed! B****r! But at least the main gear did move by a couple of teeth! Hang on though, it was trying to turn ANTICLOCKWISE. I bet that nut is a left hand thread! So it is, it came off a treat once I put a clockwise force on it! You know, 50 plus years of earning my living and generally messing about with cars. motorbikes, horticultural machines, etc, etc, and left hand threads still catch me out!
So now the nut and blade bar are out of the way all I have to do is lift the big drive gear/eccentric hub out of the casing. But no! The black thread inserts on either side of the casing are in the way:
Whipped them out and removed the gear. Triggered the motor and it spins enthusiastically! whoo hoo! In the bottom of the gear is a separate bearing housing which engages with the tang of a spring and can be just pulled out leaving the spring behind:
Trying to understand what's going on here I stuck this bearing housing back into the casing:
Immediately noticed that there's a metal peg sticking up from the bottom of the housing which now stops the bearing and housing from being able to rotate. Why? Oh, some sort of safety interlock maybe? Yes, When you compress the handhold and trigger at the same time two things happen simultaneously, The metal peg is withdrawn into the bottom of the casing so the bearing and housing can rotate and the power is switched on:
Releasing either of the controls kills the power and lets this peg pop out. So it's a quick stop control for the blade? Now I understand what the spring in the main gear is for, it tries to take the shock out of this quick stop. Now take a look at the bottom of the bearing casting:
Oops, bits missing? In fact there were shards of metal stuck under the bearing casing which was forcing the main gear/eccentric cluster up and pinching it against the bar which is held in place by the big nut (that one with the left hand thread) So the main gear cluster was jammed and unable to turn - in fact there was pickup and galling visible on the face of the gear and on the support bar which I had to grind off and polish up with some fine emery cloth.
Slapped lots of moly grease on it and reassembled it all but left the bottom cover off. Triggered the switch, with safety interlock compressed, and it leapt, enthusiastically, into life, Hurrah! Went to put the bottom cover on and, It doesn't fit:
Oh no, I've put the thread inserts back in upside down.
So that means taking the blade bar and main gear out again because the inserts slide in sideways from the inside and there's not enough clearance between the mechanicals and the case to do it.
So fifteen minutes (or so) later and after muttering a few calming obscenities the cover is on:
And the hedgecutter is ready to go home:
Don't know how long it'll last with the broken bits on that bearing casting? but I think it'll do for some time yet. Mind you, looking at that casting (bearing housing) with the broken lugs, it just doesn't look robust enough to withstand the forces acting on it does it?
So there we are. Think I've earned the afternoon off. Going to make a nice Lidl/Aldi cappuccino, check if there's a film worth recording on "Talking Pictures" and spend some time in the garden.
Take care all
regards
Jock
There was no obvious signs of anything having burnt out and the fuse in the plug was still OK - rang him and he had not fitted a new one. As I have an RCD on my garage plug I risked plugging it in and briefly pulling the trigger. It made that sort of buzzing noise that stalled electric motors often make and I could see the armature turning just a little.
OK. That may mean that it's a mechanical rather than electrical problem so I whipped the cover off the bottom of the gearbox:
Actually this picture was taken as I was reassembling - hence the liberal quantities of moly grease. I tried to move the gears with my fingers and a big screwdriver but it was solid. I thought if I removed the big (13mm spanner) nut on the end of the spindle and the two Allen bolts holding the blade bar in place then I would be able to strip the gears and eccentric blade drive hub out of the casing.
The two Allen bolts came out easily but the nut would not move. It seemed ridiculously tight, but why? What am I missing? Is there some locking tab? Special locking washer? Nope! Ok, have a cup of tea!
Sitting with my cup of tea I thought "with the blade bar bolts slackened if it's the blades that are jammed it should now spin?" so I triggered the motor again (No, it was not plugged in whilst I was working on it!) Still jammed! B****r! But at least the main gear did move by a couple of teeth! Hang on though, it was trying to turn ANTICLOCKWISE. I bet that nut is a left hand thread! So it is, it came off a treat once I put a clockwise force on it! You know, 50 plus years of earning my living and generally messing about with cars. motorbikes, horticultural machines, etc, etc, and left hand threads still catch me out!
So now the nut and blade bar are out of the way all I have to do is lift the big drive gear/eccentric hub out of the casing. But no! The black thread inserts on either side of the casing are in the way:
Whipped them out and removed the gear. Triggered the motor and it spins enthusiastically! whoo hoo! In the bottom of the gear is a separate bearing housing which engages with the tang of a spring and can be just pulled out leaving the spring behind:
Trying to understand what's going on here I stuck this bearing housing back into the casing:
Immediately noticed that there's a metal peg sticking up from the bottom of the housing which now stops the bearing and housing from being able to rotate. Why? Oh, some sort of safety interlock maybe? Yes, When you compress the handhold and trigger at the same time two things happen simultaneously, The metal peg is withdrawn into the bottom of the casing so the bearing and housing can rotate and the power is switched on:
Releasing either of the controls kills the power and lets this peg pop out. So it's a quick stop control for the blade? Now I understand what the spring in the main gear is for, it tries to take the shock out of this quick stop. Now take a look at the bottom of the bearing casting:
Oops, bits missing? In fact there were shards of metal stuck under the bearing casing which was forcing the main gear/eccentric cluster up and pinching it against the bar which is held in place by the big nut (that one with the left hand thread) So the main gear cluster was jammed and unable to turn - in fact there was pickup and galling visible on the face of the gear and on the support bar which I had to grind off and polish up with some fine emery cloth.
Slapped lots of moly grease on it and reassembled it all but left the bottom cover off. Triggered the switch, with safety interlock compressed, and it leapt, enthusiastically, into life, Hurrah! Went to put the bottom cover on and, It doesn't fit:
Oh no, I've put the thread inserts back in upside down.
So that means taking the blade bar and main gear out again because the inserts slide in sideways from the inside and there's not enough clearance between the mechanicals and the case to do it.
So fifteen minutes (or so) later and after muttering a few calming obscenities the cover is on:
And the hedgecutter is ready to go home:
Don't know how long it'll last with the broken bits on that bearing casting? but I think it'll do for some time yet. Mind you, looking at that casting (bearing housing) with the broken lugs, it just doesn't look robust enough to withstand the forces acting on it does it?
So there we are. Think I've earned the afternoon off. Going to make a nice Lidl/Aldi cappuccino, check if there's a film worth recording on "Talking Pictures" and spend some time in the garden.
Take care all
regards
Jock