Hi and apologies if this is not an appropriate post for this NG.

A friend has an ancient flail mower without any functioning
interlocks. This means that it can be started in gear with the clutch
engaged. As it has an 11Hp engine this is not to be tried more than
once. There are switches which detect the position of the clutch
handle and whether neutral has been selected on the gearbox but they
are not connected and there is no loom as such with obvious gaps that
they could fill. There is only a (working) kill-switch which earths
part of the ignition circuit. However, this is supposed to
incorporate the gearbox and clutch switches.

He has asked me to come up with a circuit that does just that. Any
thoughts? I've asked for details of the operation of the two unused
switches. I think that these beasts usually require the clutch to be
held in when starting and this is achieved with a clip rather like
those on the old auto-stop fuel filling nozzles that drops out when
you squeeze the clutch handle.

TIA and happy thinking

Richard

On Thu, 14 Jun 2012 15:00:59 -0700 (PDT), Richard Savage
wrote:

Hi and apologies if this is not an appropriate post for this NG.

Yea, this isn't. An electronics NG such as sci.electronics.repair
would be more appropriate (though the name would imply integrated
circuits and resistors and such, it'll do nicely).

A friend has an ancient

Define "Ancient". Some people think anything over 10 or even 20 years
old is "ancient".

flail mower without any functioning interlocks. This means that it
can be started in gear with the clutch engaged. As it has an 11Hp
engine this is not to be tried more than once.

At 11hp, is this an electric start, or a pull start (I pull start my
"ancient" 16HP tractor, but only because I need to replace the toothed
drive on the electric starter, and it's easy enough to pull start, so
I haven't). If there's a battery, you have the benefit of being able
to use a relay or otherwise actuate one that is present. If not, a
lot more clarity is needed for the electrical schematic.

I've got to think it's electric start, because if it were pull start,
you'd have a hell of a time managing to pull it fast enough under
load.

There are switches which detect the position of the clutch
handle and whether neutral has been selected on the gearbox but they
are not connected

You need to use a DMM and take measurements from those switches to
determine if they're open (no continuity / infinite resistance) or
closed (continuity / zero or so resistance) when their respective
controls are in the position where they should't start. Measure both
switches, and run through the various positions for them (which also
ensures the switches DO something - perhaps the wiring was gutted
because one ceased functioning). From that, you can make a "truth
table" to figure out whether you're interrupting ground or making
ground, running in series, or in parallel to the solenoid on a relay.

There's also the matter of whether the switches have two vacant
terminals, or if one is tied say to ground.

I'm guessing they're open circuit when it's a no-start situation - in
which case, run them in series inline with the starter input from the
ignition switch. If they're closed circuit when it's no-start, it'll
require a bit more doing (unless the starter relay has a disable
terminal).

Get a fix on what's what and then post to an electronics NG to
continue your fix.

There is only a (working) kill-switch which earths part of the
ignition circuit. However, this is supposed to incorporate the
gearbox and clutch switches.

I wonder - has anyone considered contacting the manufacturer (or the
company which may have purchased them, as often happens), or looked
for sites for such implements (search for the manufacturer and model).
You may be surprised.

Last year, some fella drove about 230 miles round trip to pick up a
garden tractor carcass (no engine) from me. There's some people
really into some older gear.

On Jun 15, 4:16*am, Sean Straw wrote:
On Thu, 14 Jun 2012 15:00:59 -0700 (PDT), Richard Savage

wrote:
Hi and apologies if this is not an appropriate post for this NG.

Yea, this isn't. *An electronics NG such as sci.electronics.repair
would be more appropriate (though the name would imply integrated
circuits and resistors and such, it'll do nicely).

A friend has an ancient

Define "Ancient". *Some people think anything over 10 or even 20 years
old is "ancient".

flail mower without any functioning interlocks. *This means that it
can be started in gear with the clutch engaged. *As it has an 11Hp
engine this is not to be tried more than once.

At 11hp, is this an electric start, or a pull start (I pull start my
"ancient" 16HP tractor, but only because I need to replace the toothed
drive on the electric starter, and it's easy enough to pull start, so
I haven't). *If there's a battery, you have the benefit of being able
to use a relay or otherwise actuate one that is present. *If not, a
lot more clarity is needed for the electrical schematic.

I've got to think it's electric start, because if it were pull start,
you'd have a hell of a time managing to pull it fast enough under
load.

There are switches which detect the position of the clutch
handle and whether neutral has been selected on the gearbox but they
are not connected

You need to use a DMM and take measurements from those switches to
determine if they're open (no continuity / infinite resistance) or
closed (continuity / zero or so resistance) when their respective
controls are in the position where they should't start. *Measure both
switches, and run through the various positions for them (which also
ensures the switches DO something - perhaps the wiring was gutted
because one ceased functioning). *From that, you can make a "truth
table" to figure out whether you're interrupting ground or making
ground, running in series, or in parallel to the solenoid on a relay.

There's also the matter of whether the switches have two vacant
terminals, or if one is tied say to ground.

I'm guessing they're open circuit when it's a no-start situation - in
which case, run them in series inline with the starter input from the
ignition switch. *If they're closed circuit when it's no-start, it'll
require a bit more doing (unless the starter relay has a disable
terminal).

Get a fix on what's what and then post to an electronics NG to
continue your fix.

There is only a (working) kill-switch which earths part of the
ignition circuit. *However, this is supposed to incorporate the
gearbox and clutch switches.

I wonder - has anyone considered contacting the manufacturer (or the
company which may have purchased them, as often happens), or looked
for sites for such implements (search for the manufacturer and model).
You may be surprised.

Last year, some fella drove about 230 miles round trip to pick up a
garden tractor carcass (no engine) from me. *There's some people
really into some older gear.

Hello and thank you Sean.

First reply from Robin:

"They are push to make switches. NC when clutch engaged or gear
engaged, NO when not engaged or no gear selected. At least I'm pretty
sure that's the case. I did wire them up originally much as you'd
first think of wiring them up, only to have the engine die when you
engaged *both* clutch and gears."

I have asked for confirmation of the switch data and age/make/model
and starting method.

When I have that I'll post it here and to an electronics NG.

Ta

Richard

On Jun 15, 4:16*am, Sean Straw wrote:
On Thu, 14 Jun 2012 15:00:59 -0700 (PDT), Richard Savage

wrote:
Hi and apologies if this is not an appropriate post for this NG.

Yea, this isn't. *An electronics NG such as sci.electronics.repair
would be more appropriate (though the name would imply integrated
circuits and resistors and such, it'll do nicely).

A friend has an ancient

Define "Ancient". *Some people think anything over 10 or even 20 years
old is "ancient".

flail mower without any functioning interlocks. *This means that it
can be started in gear with the clutch engaged. *As it has an 11Hp
engine this is not to be tried more than once.

At 11hp, is this an electric start, or a pull start (I pull start my
"ancient" 16HP tractor, but only because I need to replace the toothed
drive on the electric starter, and it's easy enough to pull start, so
I haven't). *If there's a battery, you have the benefit of being able
to use a relay or otherwise actuate one that is present. *If not, a
lot more clarity is needed for the electrical schematic.

I've got to think it's electric start, because if it were pull start,
you'd have a hell of a time managing to pull it fast enough under
load.

There are switches which detect the position of the clutch
handle and whether neutral has been selected on the gearbox but they
are not connected

You need to use a DMM and take measurements from those switches to
determine if they're open (no continuity / infinite resistance) or
closed (continuity / zero or so resistance) when their respective
controls are in the position where they should't start. *Measure both
switches, and run through the various positions for them (which also
ensures the switches DO something - perhaps the wiring was gutted
because one ceased functioning). *From that, you can make a "truth
table" to figure out whether you're interrupting ground or making
ground, running in series, or in parallel to the solenoid on a relay.

There's also the matter of whether the switches have two vacant
terminals, or if one is tied say to ground.

I'm guessing they're open circuit when it's a no-start situation - in
which case, run them in series inline with the starter input from the
ignition switch. *If they're closed circuit when it's no-start, it'll
require a bit more doing (unless the starter relay has a disable
terminal).

Get a fix on what's what and then post to an electronics NG to
continue your fix.

There is only a (working) kill-switch which earths part of the
ignition circuit. *However, this is supposed to incorporate the
gearbox and clutch switches.

I wonder - has anyone considered contacting the manufacturer (or the
company which may have purchased them, as often happens), or looked
for sites for such implements (search for the manufacturer and model).
You may be surprised.

Last year, some fella drove about 230 miles round trip to pick up a
garden tractor carcass (no engine) from me. *There's some people
really into some older gear.

Thanks Sean. Have asked for clarification of switch operation, age/
make/model and starting method and will post that here and to an
electronics NG.

Meanwhile this is the first reply from Robin:

"They are push to make switches. NC when clutch engaged or gear
engaged, NO when not engaged or no gear selected. At least I'm pretty
sure that's the case. I did wire them up originally much as you'd
first think of wiring them up, only to have the engine die when you
engaged *both* clutch and gears. "

Richard

On Jun 15, 4:16*am, Sean Straw wrote:
On Thu, 14 Jun 2012 15:00:59 -0700 (PDT), Richard Savage

wrote:
Hi and apologies if this is not an appropriate post for this NG.

Yea, this isn't. *An electronics NG such as sci.electronics.repair
would be more appropriate (though the name would imply integrated
circuits and resistors and such, it'll do nicely).

A friend has an ancient

Define "Ancient". *Some people think anything over 10 or even 20 years
old is "ancient".

flail mower without any functioning interlocks. *This means that it
can be started in gear with the clutch engaged. *As it has an 11Hp
engine this is not to be tried more than once.

At 11hp, is this an electric start, or a pull start (I pull start my
"ancient" 16HP tractor, but only because I need to replace the toothed
drive on the electric starter, and it's easy enough to pull start, so
I haven't). *If there's a battery, you have the benefit of being able
to use a relay or otherwise actuate one that is present. *If not, a
lot more clarity is needed for the electrical schematic.

I've got to think it's electric start, because if it were pull start,
you'd have a hell of a time managing to pull it fast enough under
load.

There are switches which detect the position of the clutch
handle and whether neutral has been selected on the gearbox but they
are not connected

You need to use a DMM and take measurements from those switches to
determine if they're open (no continuity / infinite resistance) or
closed (continuity / zero or so resistance) when their respective
controls are in the position where they should't start. *Measure both
switches, and run through the various positions for them (which also
ensures the switches DO something - perhaps the wiring was gutted
because one ceased functioning). *From that, you can make a "truth
table" to figure out whether you're interrupting ground or making
ground, running in series, or in parallel to the solenoid on a relay.

There's also the matter of whether the switches have two vacant
terminals, or if one is tied say to ground.

I'm guessing they're open circuit when it's a no-start situation - in
which case, run them in series inline with the starter input from the
ignition switch. *If they're closed circuit when it's no-start, it'll
require a bit more doing (unless the starter relay has a disable
terminal).

Get a fix on what's what and then post to an electronics NG to
continue your fix.

There is only a (working) kill-switch which earths part of the
ignition circuit. *However, this is supposed to incorporate the
gearbox and clutch switches.

I wonder - has anyone considered contacting the manufacturer (or the
company which may have purchased them, as often happens), or looked
for sites for such implements (search for the manufacturer and model).
You may be surprised.

Last year, some fella drove about 230 miles round trip to pick up a
garden tractor carcass (no engine) from me. *There's some people
really into some older gear.

Mo

It's a 1970s or more likely early 80s Saxon pedestrian flail mower
with a Robin EY40B pull start engine fitted with the separate coil and
KTR unit. Both the switches are push to make, the clutch switch makes
on clutch engagement, the gearbox switch makes on reverse gear
selection only. As far as I can work out, they were originally wired
in series as that's what the cable remnants seem to determine.

On Fri, 15 Jun 2012 01:02:31 -0700 (PDT), Richard Savage
wrote:

[snip - my original reply]

It's a 1970s or more likely early 80s Saxon pedestrian flail mower
with a Robin EY40B pull start engine fitted with the separate coil and
KTR unit. Both the switches are push to make, the clutch switch makes
on clutch engagement, the gearbox switch makes on reverse gear
selection only. As far as I can work out, they were originally wired
in series as that's what the cable remnants seem to determine.

Pullstart complicates things, because that means you don't have 12V to
drive a relay. Also means there isn't a starter relay (or start
inhibit relay). Since the switches are closed when the selectors are
in the "shouldn't start" position, it's probable they're intended to
provide an alternate ground path for the igntion (kill). If simply
wired to the ignition kill, as your friend found, it'll still kill it
when the engine is running and you go to engage the implements as
you'd expect to be able to in order to utilize the tool.

Does the engine have an alternator winding? Might be a little
bullet-like connector on the side of the flywheel assembly that may
have a fuse in it (I'm not familiar with the Robin engine, though I
could go look it up in a reference book here) - that'd provide 12V
when the engine is running, and could be used to actuate a relay.

Here's a basic primer on relays:
http://www.the12volt.com/relays/relays.asp

Check out Figure 1 - that's the terminal diagram for a very common
SPDT relay type used for automotive applications (you could pop the
bonnet on amost any car at a wreckers and pull several of these out).
An SPST relay would serve as well, since you don't need to switch a
different signal in - just disable the interlock once started.

You'd wire 85 to chassis ground, 86 to the alternator output from the
engine (all of this assumes it is present), 30 to the ignition kill
line, 87a to the control switches (in parallel, so either one provides
a ground path), and 87 needs no connection.

Now, when the engine isn't spinning (or not not spinning fast enough
to really generate 12V, such as when you very first pullstart it), you
have no 12V, so the solenoid isn't energized, and 87a (normally
closed) has continuity through to 30 (common). As a result, if either
lever is set to a no-start, the ignition system is grounded, just as
if the kill were active. Take them out of their no-start positions,
and there's no ground, and the igntion can fire. Once you've started
the engine, the alternator produces 12V, and the solenoid engages,
switching from 87a to terminal 87 (which has nothing wired to it) -
now, the position of the two levers won't kill the engine, though the
existing kill switch still will (which isn't wired through the relay).
Kill the engine with the kill switch (or because it runs out of
petrol, or whatever), and the 12V goes away, solenoid disengages, and
terminal 87a is once again selected, and the levers will inhibit
starting.

Absent a relay configuration as described (and a necessary alternator
tab), it makes me wonder if perhaps the switches are in place for an
electric start model/option (though electric start would need some way
of charging the battery, which would be the alternator tab). On a
small engine, the alternator can be wired inside the flywheel - it
doesn't need to be a separate belt-driven apparatus like you see on
cars. The original engine on my tractor had a generator - when the
engine was spinning it, it generated voltage, and when you applied
voltage to it, it spun to start the engine.

You're really capable of getting the thing pullstarted when the
implement is engaged? I wouldn't dream of expecting to get my tractor
pullstarted with it either in gear or the PTO tiller engaged.

On Jun 15, 6:29*pm, Sean Straw wrote:

lots of useful stuff

Thanks Sean. Info passed onto Robin who should come back with answers
(and thanks!) soonish.

Rgds

Richard

Thanks to all who replied.

This seems to be the solution:

From my reading of the thread and a little thought I suspect the
interlock may only be designed to kill the engine *if both* the clutch
is engaged (and said clutch is flail drive clutch, not wheel drive
clutch) *and* reverse gear is engaged at the same time in which case a
simple series connection of the switched in parallel with the engine
kill switch should suffice.

Reply from Robin:


That would be a logical assumption and quite possibly the answer, but
the layout of the belts and clutch levers doesn't lend itself to this
being the logical layout:
There are two hand levers for the two clutches*1 (calling it a
clutch is glorifying it, it's just a belt tensioner arrangement), one
for the gearbox drive, and one for the flail drive. The clutch lever
on the left handlebar is set up to operate the left belt / clutch
arrangement which operates the gearbox drive, and the clutch lever on
the right handlebar is set up to operate the right belt / clutch
arrangement which operates the flail drive. A simple swapping of the
lever control cables will give the 'no reverse with flails engaged'
scenario detailed below - and as I said above, quite possible the
answer - but the controls / cables / belts layout doesn't lend itself
to this and would explain why the previous owner(s) had installed it
this way.

*1 Of the two clutch levers, only one has the cut out switch
facility.

Many thanks for the AFL bod who came up with this probable solution.
When back at work on Monday I will see if the cables will fit the
other way around.

cheers,

Robin



Cheers

Richard