Lawnflite 703 Autodrive. PTO clutch for deck drive was slipping, so I
decided to have a go at it. I have looked at it before, a mechanically
operated clutch (rather than electrical) and then I found it was simply
metal face, to metal face - no sign of any friction material, but it
worked, so maybe that was how it was designed to work?

I have been unable to find a proper manual for it or any sort of
diagram of the tractor or the clutch, nor even a replacement clutch,
though I have not looked too hard for the latter.

It uses three balls, in deepening slots to engage disengage, with a
strong spring to engage and a light concentric spring to push the
plates apart.

Lacking any better idea, I thought to try a bit of thin card to act as
friction material between the two metal plates, but couldn't find any
suitable. What I did find was some material marked Novus Econostus
1.5mm which has been laying about in my workshop for decades, probably
intended as gasket material of some sort (light browny orange colour),
so I cut some of that into a disk and super glued it to the clutch
plate.

Drive to cutting deck now seems to work fine, but for how long? I
cannot see the clutch being under much stress, because it has sort of
worked metal to metal for the past few years.

Harry Bloomfield presented the following explanation :
Lawnflite 703 Autodrive. PTO clutch for deck drive was slipping, so I decided
to have a go at it. I have looked at it before, a mechanically operated
clutch (rather than electrical) and then I found it was simply metal face, to
metal face - no sign of any friction material, but it worked, so maybe that
was how it was designed to work?

Bump, someone must know?

Is a clutch ever designed to operate without any friction material just
steel against steel. There were no obvious signs of any friction
material ever having been there..

On 07/05/2019 16:30, Harry Bloomfield wrote:
Harry Bloomfield presented the following explanation :
Lawnflite 703 Autodrive. PTO clutch for deck drive was slipping, so I
decided to have a go at it. I have looked at it before, a mechanically
operated clutch (rather than electrical) and then I found it was
simply metal face, to metal face - no sign of any friction material,
but it worked, so maybe that was how it was designed to work?

Bump, someone must know?

Is a clutch ever designed to operate without any friction material just
steel against steel. There were no obvious signs of any friction
material ever having been there..

yes. Conical style clutches and IIRC centrifugal cluthes often used metal...
....ooi is this yours?

https://www.revillmowers.co.uk/spare...-kit-753-06346


--
There is nothing a fleet of dispatchable nuclear power plants cannot do
that cannot be done worse and more expensively and with higher carbon
emissions and more adverse environmental impact by adding intermittent
renewable energy.

On 07/05/2019 16:30, Harry Bloomfield wrote:
Harry Bloomfield presented the following explanation :
Lawnflite 703 Autodrive. PTO clutch for deck drive was slipping, so I
decided to have a go at it. I have looked at it before, a mechanically
operated clutch (rather than electrical) and then I found it was
simply metal face, to metal face - no sign of any friction material,
but it worked, so maybe that was how it was designed to work?

Bump, someone must know?

Is a clutch ever designed to operate without any friction material just
steel against steel. There were no obvious signs of any friction
material ever having been there..

Your description of 3 balls in deepening slots made it sound more like
some designs of freewheel to me (rather than a clutch). It's certainly
true that freewheels are usually metal to metal. As TNP points out there
are also various types of metal to metal clutch. Some use sintered
bronze on hardened steel multiplates (later Norton Commandos, I
believe). You don't want steel on steel to see too much slipping, unless
it is in an oil bath.

On 07/05/2019 19:00, newshound wrote:
On 07/05/2019 16:30, Harry Bloomfield wrote:
Harry Bloomfield presented the following explanation :
Lawnflite 703 Autodrive. PTO clutch for deck drive was slipping, so I
decided to have a go at it. I have looked at it before, a
mechanically operated clutch (rather than electrical) and then I
found it was simply metal face, to metal face - no sign of any
friction material, but it worked, so maybe that was how it was
designed to work?

Bump, someone must know?

Is a clutch ever designed to operate without any friction material
just steel against steel. There were no obvious signs of any friction
material ever having been there..

Your description of 3 balls in deepening slots made it sound more like
some designs of freewheel to me (rather than a clutch). It's certainly
true that freewheels are usually metal to metal. As TNP points out there
are also various types of metal to metal clutch. Some use sintered
bronze on hardened steel multiplates (later Norton Commandos, I
believe). You don't want steel on steel to see too much slipping, unless
it is in an oil bath.

Lawnflite manuals seem to be available to download. The Laser ride-on
mower that I used to have simply slackened off a V belt to disengage the
drive.

The Natural Philosopher brought next idea :
yes. Conical style clutches and IIRC centrifugal cluthes often used metal...
...ooi is this yours?

https://www.revillmowers.co.uk/spare...-kit-753-06346

That looks like it, but its neither conical or centrifugal. The clutch
is engaged by a level by the steering wheel, that spring then forms the
force to push the two clutch plates tightly together.

newshound laid this down on his screen :
Your description of 3 balls in deepening slots made it sound more like some
designs of freewheel to me (rather than a clutch). It's certainly true that
freewheels are usually metal to metal. As TNP points out there are also
various types of metal to metal clutch. Some use sintered bronze on hardened
steel multiplates (later Norton Commandos, I believe). You don't want steel
on steel to see too much slipping, unless it is in an oil bath.

This is/was just steel on steel. The three balls in the slots, are just
the means to force the clutch plates tightly together, via a coil
spring and bearing.

newshound expressed precisely :
Lawnflite manuals seem to be available to download. The Laser ride-on mower
that I used to have simply slackened off a V belt to disengage the drive.

That is what this one uses for the propulsion system V-belt, tightening
it to provide the drive, but the PTO for the deck uses this weird
clutch system.

On 07/05/2019 19:43, Harry Bloomfield wrote:
newshound laid this down on his screen :
Your description of 3 balls in deepening slots made it sound more like
some designs of freewheel to me (rather than a clutch). It's certainly
true that freewheels are usually metal to metal. As TNP points out
there are also various types of metal to metal clutch. Some use
sintered bronze on hardened steel multiplates (later Norton Commandos,
I believe). You don't want steel on steel to see too much slipping,
unless it is in an oil bath.

This is/was just steel on steel. The three balls in the slots, are just
the means to force the clutch plates tightly together, via a coil spring
and bearing.

Interesting. I guess it is just meant to be on-off. Provided the load is
high enough it probably never really slips. I wonder if it is hardened
steel, or just mild steel? Ordinary grey cast iron would probably work
OK as the graphite might help to prevent the metal picking up or scoring.

After serious thinking newshound wrote :
Interesting. I guess it is just meant to be on-off.

There has to be some initial slippage and wear, when it engages with
the engine running at full speed, so not quite on off.

Provided the load is high
enough it probably never really slips. I wonder if it is hardened steel, or
just mild steel? Ordinary grey cast iron would probably work OK as the
graphite might help to prevent the metal picking up or scoring.

The metal plates seem to be just pressed mild steel and both are quite
scored. I have had a long term issue with my grass being quite tough
and moist, jamming up the cutter deck - probably causing a lot of
clutch slippage.

I earlier ran a full test of my 'gasket material' modified clutch and
it seems to be holding up.

Does seem a little on the crude side. Some materials can make it snatch and
if it gets at all hot during running it might melt or go sticky.
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"Harry Bloomfield" wrote in message
...
Lawnflite 703 Autodrive. PTO clutch for deck drive was slipping, so I
decided to have a go at it. I have looked at it before, a mechanically
operated clutch (rather than electrical) and then I found it was simply
metal face, to metal face - no sign of any friction material, but it
worked, so maybe that was how it was designed to work?

I have been unable to find a proper manual for it or any sort of diagram
of the tractor or the clutch, nor even a replacement clutch, though I have
not looked too hard for the latter.

It uses three balls, in deepening slots to engage disengage, with a strong
spring to engage and a light concentric spring to push the plates apart.

Lacking any better idea, I thought to try a bit of thin card to act as
friction material between the two metal plates, but couldn't find any
suitable. What I did find was some material marked Novus Econostus 1.5mm
which has been laying about in my workshop for decades, probably intended
as gasket material of some sort (light browny orange colour), so I cut
some of that into a disk and super glued it to the clutch plate.

Drive to cutting deck now seems to work fine, but for how long? I cannot
see the clutch being under much stress, because it has sort of worked
metal to metal for the past few years.

Brian Gaff brought next idea :
Does seem a little on the crude side. Some materials can make it snatch and
if it gets at all hot during running it might melt or go sticky.
Brian

Seems to be working fine, better than it has ever done in my ownership
- now I have run a more thorough test. It shouldn't get hot, unless due
to the friction of the clutch slipping.

On 07/05/2019 22:22, Harry Bloomfield wrote:
After serious thinking newshound wrote :
Interesting. I guess it is just meant to be on-off.

There has to be some initial slippage and wear, when it engages with the
engine running at full speed, so not quite on off.

Provided the load is high enough it probably never really slips. I
wonder if it is hardened steel, or just mild steel? Ordinary grey cast
iron would probably work OK as the graphite might help to prevent the
metal picking up or scoring.

The metal plates seem to be just pressed mild steel and both are quite
scored. I have had a long term issue with my grass being quite tough and
moist, jamming up the cutter deck - probably causing a lot of clutch
slippage.

I earlier ran a full test of my 'gasket material' modified clutch and it
seems to be holding up.

It might well be good. Quite simple heavy woven cotton used to be used
for clutches and brakes on things like cranes.

On 07/05/2019 20:18, newshound wrote:
On 07/05/2019 19:43, Harry Bloomfield wrote:
newshound laid this down on his screen :
Your description of 3 balls in deepening slots made it sound more
like some designs of freewheel to me (rather than a clutch). It's
certainly true that freewheels are usually metal to metal. As TNP
points out there are also various types of metal to metal clutch.
Some use sintered bronze on hardened steel multiplates (later Norton
Commandos, I believe). You don't want steel on steel to see too much
slipping, unless it is in an oil bath.

This is/was just steel on steel. The three balls in the slots, are
just the means to force the clutch plates tightly together, via a coil
spring and bearing.

Interesting. I guess it is just meant to be on-off. Provided the load is
high enough it probably never really slips. I wonder if it is hardened
steel, or just mild steel? Ordinary grey cast iron would probably work
OK as the graphite might help to prevent the metal picking up or scoring.

I have the same mower - mine is probably the 2007 model.

The clutch still works ok on mine, but its definitely a progressive
action. You can engage the blade gradually... usually wise if you are
not sure if the deck is clogged or not - saves stalling it.

--
Cheers,

John.

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| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Rumm pretended :
I have the same mower - mine is probably the 2007 model.

The clutch still works ok on mine, but its definitely a progressive action.
You can engage the blade gradually... usually wise if you are not sure if the
deck is clogged or not - saves stalling it.

Yes, it is very progressive and a clogged deck I find is a very regular
problem. It is never obvious that the deck is clogged up jamming the
blade rotation, which probably explains my clutch issues.

Because it clogged so often, I stopped using the grass collector on it
to make the deck and duct a bit easier to clear out. I'm thinking to
remove the duct entirely, to knock up a bit tin to convert it to side
discharge duct. If I just remove the rear discharge duct, it blows the
cuttings onto the pulleys and drive belts, causing them to slip.

On 10/05/2019 09:09, Harry Bloomfield wrote:
John Rumm pretended :
I have the same mower - mine is probably the 2007 model.

The clutch still works ok on mine, but its definitely a progressive
action. You can engage the blade gradually... usually wise if you are
not sure if the deck is clogged or not - saves stalling it.

Yes, it is very progressive and a clogged deck I find is a very regular
problem. It is never obvious that the deck is clogged up jamming the
blade rotation, which probably explains my clutch issues.

Because it clogged so often, I stopped using the grass collector on it
to make the deck and duct a bit easier to clear out. I'm thinking to
remove the duct entirely, to knock up a bit tin to convert it to side
discharge duct. If I just remove the rear discharge duct, it blows the
cuttings onto the pulleys and drive belts, causing them to slip.

The standard deck is not really configured to allow cut'n'drop, since it
blows all the clippings out of the central top opening. So you can cut
and collect, or block the outlet altogether with the mulch plug, and
then cut and mulch. I have tried defeating the grass collector
interlock, and just allowing the rear duct to discharge into free space
- but it has quite significant airflow, and you get plume of blown grass
that tails probably more than 10' behind you! Perhaps adding a baffle
there to redirect the stream at the ground would work.

(A side discharge chute could work - although because of the counter
rotating blades, the grass is being swept forward at the outsides of the
deck)

To minimise clogging on damp grass, I adopt a number of procedures... I
don't take off much at a time - start on the longest grass setting. If
worse comes to worst, then mowing twice without clogs is less hassle
than having to unblock it every 5 mins). Don't allow the collection bin
to get too full. Keep the glass collector interlock disabled, and have a
5 or 6' long bit of scrap timber handy. When it clogs I then take off
the collection bin, engage the brake lock, hold the seat down by hand
and engage the blades. Now with one hand holding the seat to keep that
interlock engaged, you can poke the duct with the wood. A quick stir
will normally loosen it enough to then blow out. (perhaps one of these
days I will wire up an interlock disable switch to knock out the grass
box, and seat interlocks)

I have toyed with the idea of taking an angle grinder to the back of the
deck and cutting away the back wall, so that it can be reattached with a
hinge mechanism, and some kind of two position lock. That way you could
close it and lock it shut to get the current mode of operation, fit the
mulch plug, then lock the flap open to allow grass to fall out of the back.

Armed with a tow behind sweeper, that would be quite handy for the
tricky first cut of the year when everything is a bit damp.

(once its got to this time of the year, clogging is pretty rare I find)

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/