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.