broken lawn mower
Stephen
I've got a green Bosch lawnmower ARM32 which seems to be broken. When
I press the buttons I get a loud hum from the motor but the blade does
not spin. I've noticed if I press the switch on and off, there is a
metallic clunk every time I press the switch in to start the mower.
I've looked and there are no blockages and -when unplugged!- the blade
spins freely by hand.
Is it time to buy a new one or can I or an expert fix it?
Thanks.
www.GymRatZ.co.uk
> Hello,
>
> I've got a green Bosch lawnmower ARM32 which seems to be broken. When
> I press the buttons I get a loud hum from the motor but the blade does
> not spin. I've noticed if I press the switch on and off, there is a
> metallic clunk every time I press the switch in to start the mower.
>
> I've looked and there are no blockages and -when unplugged!- the blade
> spins freely by hand.
My initial thoughts are you've wound the bottom plate up too tight.
If you are winding the helical blade backwads the blades will ride over
the bottom "blade" but when the motor tries to power it the leading edge
of one of the helical blades will catch on the corner of the bottom blade.
slacken off the adjustment screws untill the blade doesn't jam when
rotated in a "forwards" motion i.e. from sky to grass.
You can adjust the centre of the bottom blade if it's not cutting by a
couple of subtly "firm" hammer blows.
Then re-adjust both adjustment screws to get the blade to the same "gap"
all the way along.
I may be wrong...... but I'll bet a beer on it I'm not.
:¬)
HTH
Pete
Andrew Gabriel
Sounds like it's an induction motor with a dead start/run capacitor.
The test for this is to see if it starts if you give it a spin, but
this is rather dangerous, obviously, so it's up to you if you think
you can do this safely without removing fingers. (Don't spin it with
your hand!)
--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
Stephen
>My initial thoughts are you've wound the bottom plate up too tight.
>If you are winding the helical blade backwads the blades will ride over
>the bottom "blade" but when the motor tries to power it the leading edge
>of one of the helical blades will catch on the corner of the bottom blade.
Hello, If I have understood correctly, you seem to be suggesting that
there are two blades, one on top of the other and they are catching.
is that right? If so, I don't think this is happening because as far
as I am aware there is only one blade. There is a diagram at:
http://www.mtmc.co.uk/prodtype.asp?cookiecheck=yes&PT_ID=12725761
It's not quite the same model because the one in the diagram talks
about batteries, so I assume it is cordless/rechargeable model,
whereas mine is mains corded.
Thanks.
Stephen
Gabriel) wrote:
>Sounds like it's an induction motor with a dead start/run capacitor.
>The test for this is to see if it starts if you give it a spin, but
>this is rather dangerous, obviously, so it's up to you if you think
>you can do this safely without removing fingers. (Don't spin it with
>your hand!)
Thank you. I think you may be right. When I bought the lawn mower I am
sure that the marketing emphasised that it had an induction motor,
saying that induction motors were quieter than other types of motor.
Is that true? I have had a quick look on wikipedia to find out what an
induction motor is but I didn't see anything about noise or power
compared to other (synchronous ?) motors. The neighbours' mowers do
seem louder, so are induction powered mowers rare?
I don't think that the exploded view I quoted in my other reply shows
a capacitor. Is it an integral part of the motor? I hope not because
that web site prices the motor at more than thrice the cost of the
mower! I presume the start cap. is easy to identify being the
largest/only capacitor? If I buy one of the same capacitance and same
voltage rating, should everything be ok?
What would cause the cap to fail: is it age? I bought the mower about
eight years ago, is that good for a lawn mower/start cap? How long
should they last?
Why does the motor get louder when the cap fails, and why is there the
clunking noise? Have I understood wikipedia correctly, is it that the
cap is broken so it does not supply enough current to get the motor
started?
Thanks again.
chris French
<inv...@invalid.org> writes
>On Sat, 25 Apr 2009 19:04:53 +0100, "www.GymRatZ.co.uk"
><discount-fitn...@gym.shop.com> wrote:
>
>>My initial thoughts are you've wound the bottom plate up too tight.
>>If you are winding the helical blade backwads the blades will ride over
>>the bottom "blade" but when the motor tries to power it the leading edge
>>of one of the helical blades will catch on the corner of the bottom blade.
>
>Hello, If I have understood correctly, you seem to be suggesting that
>there are two blades, one on top of the other and they are catching.
>is that right? If so, I don't think this is happening because as far
>as I am aware there is only one blade.
Pete thought you had a cylinder mower by the sounds of it.
--
Chris French
Stephen
Thanks for the explanation. Are cylinders better than rotaries, should
I need to buy a new one?
I found this:
http://www.mtmc.co.uk/prodtype.asp?PT_ID=12725746&strPageHistory=cat
which is nearer the mark to what I have but even that has a motor for
£80, which I am sure is more than I paid for the mower, that's
inflation for you. I guess if it needed a new motor, I would be best
to buy a new mower; let's hope I can just swap the cap though.
BTW I notice what I call the blade, that site alls the knife, is
looking a bit worse for wear. Can these be sharpened on a bench
grinder or is there a better way?
Thanks again.
The Natural Philosopher
>> Pete thought you had a cylinder mower by the sounds of it.
>
> Thanks for the explanation. Are cylinders better than rotaries, should
> I need to buy a new one?
>
Nothing gets out of whack faster, that a cylinder and wood, stones or
children's toys.
Your choice.
John Rumm
> On 25 Apr 2009 18:10:11 GMT, and...@cucumber.demon.co.uk (Andrew
> Gabriel) wrote:
>
>> Sounds like it's an induction motor with a dead start/run capacitor.
>> The test for this is to see if it starts if you give it a spin, but
>> this is rather dangerous, obviously, so it's up to you if you think
>> you can do this safely without removing fingers. (Don't spin it with
>> your hand!)
>
> Thank you. I think you may be right. When I bought the lawn mower I am
> sure that the marketing emphasised that it had an induction motor,
> saying that induction motors were quieter than other types of motor.
> Is that true? I have had a quick look on wikipedia to find out what an
Yup, much quieter than a universal motor - which is the other common
alternative.
> induction motor is but I didn't see anything about noise or power
> compared to other (synchronous ?) motors. The neighbours' mowers do
> seem louder, so are induction powered mowers rare?
They are getting much more common - since rules about noise emissions
have tightened. They also have a much more suited torque curve for grass
cutting - developing maximum at full speed, rather than maximum when
stalled.
> I don't think that the exploded view I quoted in my other reply shows
> a capacitor. Is it an integral part of the motor? I hope not because
> that web site prices the motor at more than thrice the cost of the
> mower! I presume the start cap. is easy to identify being the
> largest/only capacitor? If I buy one of the same capacitance and same
> voltage rating, should everything be ok?
On many motors they are housed in a bulge on the side of the motor...
> What would cause the cap to fail: is it age? I bought the mower about
> eight years ago, is that good for a lawn mower/start cap? How long
> should they last?
They can dry out, or leak... I had a similar problem on my SIP chip
collector recently. The cap looked rather knackered - the outer case was
leaking and it was a bit soggy!
> Why does the motor get louder when the cap fails, and why is there the
> clunking noise? Have I understood wikipedia correctly, is it that the
> cap is broken so it does not supply enough current to get the motor
> started?
The cap is there to create a phase shifted supply voltage (in effect
creating another phase to create a rotating magnetic field that will
drag the armature around). Once it is spinning, its no longer needed
(the momentum of the armature and the slight "slip" caused by the
mechanical load on it, will keep it moving) and a centrifugal switch
will normally switch the cap out of circuit. You normally hear a clunk
when the switch activates - normally as it is coming up to speed, or as
it spins down. Alternatively you may be hearing a solenoid clicking or
something like that.
There is no reason why it would get louder as it fails - however once it
is failing to spin and just stalling at startup, you will get a loud hum
from the motor as it just sits there with the armature buzzing in the
alternating magnetic field.
--
Cheers,
John.
/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/
meow...@care2.com
easy to grind the blade, and it makes a real difference to
performance. They do get in a sorry state. I always ground in situ,
with an angle grinder. Dont forget the grind should be one sided, so
the grass cuttings are whisked upwards.
NT
R
"The Natural Philosopher" <t...@invalid.invalid> wrote in message
news:gsvru7$6vm$4...@news.albasani.net...
A bit of a broad description, but nearly right.
A good sharp and balanced blade on a rotary will tackle longer grass than a
reel mower and still give satisfactory results, often on uneven ground. The
actual "cut" leaves the grass more susceptible to ingress of disease if not
razor sharp as there is a tearing rather than true cutting action. Clearing
the cut grass from the cutting area is essential to reduce load and throw to
the box (If fitted) this can be achieved by the shape of the rear of the
blade being used to clear the sward from the cutting area. Watching the cut
as it happens and seeing a trail of grass behind often indicates that the
bag is full, the blade clogged or the exit chute is blocked. Reduction in
blade rotation speed then overloads the motor causing premature failure.
Usually heard on a petrol when the engine labours.
A good sharp bottom blade (AKA Bedknife) and reel with "Fag paper" thickness
clearance between the two will give a finer and more uniform cut giving the
nice striped effect from the following roller. Commonest mistake my DIYers
is to have the reel touching the bottom blade, just produces heat and noise
while wearing out both. Backlapping is usually not possible on anything
other than commercial units so cannot be done. Running a file over the
bottom blade front edge a few degrees off vertical can be a quick way of
gaining a "new"" sharp edge before re-mowing the next time.
See diagram 10 on the pdf file at
http://www.peoplepoweredmachines.com/sunlawn-reel/_docs/MM-2_Owners_Manual.pdf
for a description of setting the clearance etc. Works for powered mowers
equally as well.
After 15 years in the trade as a Golf Course machinery mechanic I have tried
all sorts of combinations. It's really a case of "Horses for Courses" with
your own decision based on the size of plot and the effect or cut style
required and whether the area is being prepared for leisure or other
purposes.
650 acres of varying heights and grass types is a lot to mow with a reel
;-)
Bob Minchin
few seconds (10?) after switching off. The noise you hear may possibly
be an automatic brake being released.
Bob
Stephen
<see.my.s...@nowhere.null> wrote:
>They can dry out, or leak... I had a similar problem on my SIP chip
>collector recently. The cap looked rather knackered - the outer case was
>leaking and it was a bit soggy!
Thank you for all the replies. I removed part of the lawn mower body
from above the motor: it was held in place by three clips, one on each
side. Looking into the mower I can see the motor and the capacitor is
bolted onto the side of the motor, so I am hoping I can change the
capacitor without having to change the motor. I'm hoping this way I
can make a cheap repair rather than have to buy an expensive new
mower.
The side of the capacitor is obscured by the mower body. I need to
remove the motor to read what is on the side of the cap. Incidentally,
there does seem to be a bulge three quarters of the way up the
capacitor. Does this indicate failure?
I tried to spin the blade using a garden cane and standing well back
whilst wearing goggles and the motor will run once spun, so I guess
this confirms it?
On the motor is a label which says "CB 12uF 450VDB". Is this referring
to the start capacitor? I am puzzled by the VDB: 450 Volts but what is
DB?
To remove the motor to read the capacitor directly I need to remove
four 17mm bolts. Unfortunately these are recessed and I cannot fit a
socket or box spanner into the recess. Any idea how I loosen these?
It looks as though the two wires from the cap goes straight into the
motor, which presents me with a second problem: how to connect a
replacement capacitor?
Will the capacitor still be holding a charge. Do I have to be very
careful handling it? If so, what is the safest way to discharge it so
that it no longer poses a threat?
Thanks.
Stephen
nuts were actually covers. Once I flipped these off I found smaller
steel nuts that I could fit a socket around. The motor is now loose
but it is too big to get out the hole, so I've got to work out how to
remove the rest of the mower body! Why aren't these things simple?
The Natural Philosopher
> On Sat, 25 Apr 2009 23:21:24 +0100, John Rumm
> <see.my.s...@nowhere.null> wrote:
>
>> They can dry out, or leak... I had a similar problem on my SIP chip
>> collector recently. The cap looked rather knackered - the outer case was
>> leaking and it was a bit soggy!
>
> Thank you for all the replies. I removed part of the lawn mower body
> from above the motor: it was held in place by three clips, one on each
> side. Looking into the mower I can see the motor and the capacitor is
> bolted onto the side of the motor, so I am hoping I can change the
> capacitor without having to change the motor. I'm hoping this way I
> can make a cheap repair rather than have to buy an expensive new
> mower.
>
> The side of the capacitor is obscured by the mower body. I need to
> remove the motor to read what is on the side of the cap. Incidentally,
> there does seem to be a bulge three quarters of the way up the
> capacitor. Does this indicate failure?
>
> I tried to spin the blade using a garden cane and standing well back
> whilst wearing goggles and the motor will run once spun, so I guess
> this confirms it?
>
> On the motor is a label which says "CB 12uF 450VDB". Is this referring
> to the start capacitor? I am puzzled by the VDB: 450 Volts but what is
> DB?
>
250VAC.
> To remove the motor to read the capacitor directly I need to remove
> four 17mm bolts. Unfortunately these are recessed and I cannot fit a
> socket or box spanner into the recess. Any idea how I loosen these?
>
Get a slender box.
> It looks as though the two wires from the cap goes straight into the
> motor, which presents me with a second problem: how to connect a
> replacement capacitor?
>
Solder or crimp to cut wires, or dismantle motor.
> Will the capacitor still be holding a charge. Do I have to be very
> careful handling it? If so, what is the safest way to discharge it so
> that it no longer poses a threat?
>
No. Almost certainly not. its generally shorted by the totality of the
windings.
> Thanks.
R
"Stephen" <inv...@invalid.org> wrote in message
news:19q8v4thvfunqfieg...@4ax.com...
Bulge in cap' usually means FKD.
Discharge it by shorting the wires together if you're worried, (Use
insulated pliers) but if it's bulging already it's had it.
Maplin or R.S components may well have a suitable replacement
Andrew Gabriel
Stephen <inv...@invalid.org> writes:
> Thank you for all the replies. I removed part of the lawn mower body
> from above the motor: it was held in place by three clips, one on each
> side. Looking into the mower I can see the motor and the capacitor is
> bolted onto the side of the motor, so I am hoping I can change the
> capacitor without having to change the motor. I'm hoping this way I
> can make a cheap repair rather than have to buy an expensive new
> mower.
>
> The side of the capacitor is obscured by the mower body. I need to
> remove the motor to read what is on the side of the cap. Incidentally,
> there does seem to be a bulge three quarters of the way up the
> capacitor. Does this indicate failure?
>
> I tried to spin the blade using a garden cane and standing well back
> whilst wearing goggles and the motor will run once spun, so I guess
> this confirms it?
>
> On the motor is a label which says "CB 12uF 450VDB". Is this referring
> to the start capacitor? I am puzzled by the VDB: 450 Volts but what is
> DB?
It's probably VAC.
Go to http://cpc.farnel.co.uk and type "motor start capacitor 12uf"
into the search box, and you should have two choices -- a wire-ended
one, and a blade terminal one.
The actual capacitance value isn't very important - the higher the
value, the higher the starting torque, but the higher the current
draw. The voltage should be 400VAC or higher, but all start
capacitors are anyway. Check the physical size will fit, and if
it won't, go down to the next smaller capacitance value.
> To remove the motor to read the capacitor directly I need to remove
> four 17mm bolts. Unfortunately these are recessed and I cannot fit a
> socket or box spanner into the recess. Any idea how I loosen these?
>
> It looks as though the two wires from the cap goes straight into the
> motor, which presents me with a second problem: how to connect a
> replacement capacitor?
Maybe push-on blade connectors at the capacitor. If not, get a wire
ended one, and cut/join the wires.
> Will the capacitor still be holding a charge. Do I have to be very
> careful handling it? If so, what is the safest way to discharge it so
> that it no longer poses a threat?
Probably not, as it's dead.
Also, don't power it up for a while before opening it.
www.GymRatZ.co.uk
> easy to grind the blade, and it makes a real difference to
> performance. They do get in a sorry state. I always ground in situ,
> with an angle grinder. Dont forget the grind should be one sided, so
> the grass cuttings are whisked upwards.
We used to grind them off-mower and then take off a bit from whichever
back edge needed it to get the balde balanced.
OP: My original comment was about a cylinder mower. Sorry if I confused.
Cheers
Pete
Stephen
>Bulge in cap' usually means FKD.
>Discharge it by shorting the wires together if you're worried, (Use
>insulated pliers) but if it's bulging already it's had it.
I managed to dismantle the mower. It was simpler than I first thought.
Just a few well hidden screws. I wasn't sure if I touched the two
wires together whether it would go bang. Don't I need a series
resistor? Judging from the other posts though, it should discharge
through the motor windings?
Stephen
Gabriel) wrote:
>Go to http://cpc.farnel.co.uk and type "motor start capacitor 12uf"
>into the search box, and you should have two choices -- a wire-ended
>one, and a blade terminal one.
The capacitor I have has something not unlike long, fault, spade
terminals that slide into a connection block on the motor, so I may
buy the wired cap you mention and solder the wires to the terminals.
Thanks again. That's saved us a fortune.
R
Well it's past 9pm, you're still alive and persevering well.
Follow the ideas and recommendations from Andrew below and you'll get there
Stephen
>Well it's past 9pm, you're still alive and persevering well.
>Follow the ideas and recommendations from Andrew below and you'll get there
Don't worry, I wasn't still working on it at 9pm! I was unsure at
first because I could not see how to remove the mower cover and I
worried it was a disposable sealed unit with no "user serviceable
parts inside". It looked as though it was held together with plastic
rivets but I eventually found some screws in the wheel arches.
I had already looked at CPC but my capacitor had two leads molded into
it, that ran to a connector block on the side of the motor. The block
seemed quite loose and I didn't want to pull the wires with any force
for fear of breaking the internal connections inside the motor.
Fortunately the wire did pull out and had a flat, not fault (spell
checker mistake), connector. From the CPC side it would appear they
are called "blade" connectors. I will try and re-use mine.
The capacitor has arrived today but has a brown wire and a blue wire.
I guess it's electrolytic? The old cap had two white wires and there
are no markings on the connector. Which one should I connect where or
doesn't it matter (or will it make the motor run backwards)?
Thanks again for all your help, you have saved me a fortune I'm sure.
Andrew Gabriel
Doesn't matter which way around, and that won't change the direction.
Providing it's marked VAC, it's not an electrolytic.
> Thanks again for all your help, you have saved me a fortune I'm sure.
--
Stephen
Gabriel) wrote:
>Doesn't matter which way around, and that won't change the direction.
>Providing it's marked VAC, it's not an electrolytic.
My mistake. I saw that it had a blue and brown wire and being in the
microFarad region and being cylindrical in shape I guessed it was
electrolytic, though I did wonder how that would work with AC. A
little knowledge is a dangerous thing!
I removed the old cap and this is what it said:
C 450V 25/85/21
B 400V 25/85/21
The new cap says:
-25/85/21
I don't know what this means but I wondered whether the -25 to 85 is
the working temperature range in Celcius?
The new one also says:
B 425V 10000h/cl
C 475V 3000h/cl
I'm guessing it is Volts and hours but what is a cl?
I'm faced with one final problem. I looked at terminal on CPC when I
ordered the capacitor and I was bewildered, so I had hoped to recycle
the old ones. Unfortunately I cannot remove the old wire because it is
crimped to the terminal. I realise now that I should have joined to
the old wire only I cut the wire off at the terminal so do not have
anything to connect to!
The terminal is called a blade or a tab depending on the web site but
I cannot find any the right size. The connector is 29mm long in total,
with the blade or tab being 16mm long and just over 6mm (6.4mm) wide
and about 0.7mm thick.
Does anyone know what these are called or where I can get a pair?
Thanks,
Stephen.
Dave Liquorice
> Does anyone know what these are called or where I can get a pair?
Probably standard 1/4" blades (male, flat) or the female for a blade with
the edges rolled around. Halfords sell 'em or you could just solder the
wires to the original connectors or carefully uncrimp them, though getting
a decent connection after uncrimping without soldering is tricky.
--
Cheers
Dave.
Stephen
<allsortsn...@howhill.com> wrote:
>Probably standard 1/4" blades (male, flat) or the female for a blade with
>the edges rolled around. Halfords sell 'em or you could just solder the
>wires to the original connectors or carefully uncrimp them, though getting
>a decent connection after uncrimping without soldering is tricky.
I had hoped to uncrimp and re-use the originals but I could not open
them. How are you supposed to do that?
I looked at RS, CPC, Maplin but they didn't have what I was looking
for. What I need is slightly longer than the common-size blade
terminal that they all sell.
It is very difficult to see what I would be buying on these websites
as they tend to use a generic photo rather than a close-up photo of
the specific item. I did try to read some of the RS datasheets but
they were nothing more than sketches and the measurements were in
inches!
I did the sensible thing and went for a walk around some "real" shops
where I could hold the crimps in my hands. I had no joy with a number
of electrical shops nor car shops until I went to Halfords who
suggested a hidden auto electric shop that I had never heard of
before.
It was like a trade counter so I couldn't see what else they sold but
they went into a drawer and magically produced what I needed. I've
never crimped before and didn't do a very good job of it but I
soldered it as well, so the solder did the trick even if the crimping
did not.
Where can I learn more about how to crimp properly and what tool do
you recommend?
Thank you all once again for all your help. The mower is back to
normal again and it cost less than �5. You have been a fantastic help.
Thank you.
John Rumm
> Where can I learn more about how to crimp properly and what tool do
> you recommend?
For insulated crimps there is not much to it:
http://wiki.diyfaq.org.uk/index.php?title=Cable_crimping
The uninsulated type sometimes require a little more care to fold the
claws round the wire.
The Medway Handyman
> Stephen wrote:
>
>> Where can I learn more about how to crimp properly and what tool do
>> you recommend?
>
> For insulated crimps there is not much to it:
>
> http://wiki.diyfaq.org.uk/index.php?title=Cable_crimping
Superb article John, well done.
--
Dave - The Medway Handyman
www.medwayhandyman.co.uk
Stephen
<see.my.s...@nowhere.null> wrote:
>For insulated crimps there is not much to it:
>
>http://wiki.diyfaq.org.uk/index.php?title=Cable_crimping
Thank you that was very useful. Unfortunately these were uninsulated
crimps, so I'll have to wait for part two.
John Rumm
> John Rumm wrote:
>> Stephen wrote:
>>
>>> Where can I learn more about how to crimp properly and what tool do
>>> you recommend?
>> For insulated crimps there is not much to it:
>>
>> http://wiki.diyfaq.org.uk/index.php?title=Cable_crimping
>
> Superb article John, well done.
Well thank you... but that one has been there for ages!