Engine speed limiter for industrial grey motors

[ardiesse]

At the humpy club meetings we have a "show and tell".  Last night's did not disappoint.
One of the guys brought in what looked like a steampunk distributor rotor.  And so it was . . .
He said it was from an air-compressor-on-a-trailer, powered by a grey motor, which the Defence Department was putting up for auction.  The engine had a grand total of 12 hours time.
It's a distributor rotor to fit Bosch distributors, but almost circular and nearly fills the inside of the cap, and it had all this extra weird stuff hanging off it.

The normal brass "tongue" that rotors have was still there, but almost completely encased in Bakelite.  Then about 150 degrees away was a brass block on a rod which moved in and out, retained by a coil spring over the rod.  When the rod was at its full extent, it contacted a vertical pin mounted on a metal horse-shoe-shaped bracket riveted onto the Bakelite.  The bracket was connected electrically to the detent spring which holds the rotor in position on the distributor cam (and earths it).

It's an overspeed cutout.  As engine speed increases, the spring-loaded brass block moves outwards under centrifugal force, until the gap between it and the vertical pin is small enough for the spark to jump the gap, depriving the spark plugs of lightning. Engine slows down, brass block retreats inwards, and the spark plugs get their zap back.

That's not all.  In the rotor there was also what looked like a resistor, probably for interference suppression.

Has anybody ever come across one of these distributor rotors?

And I'm thinking of a hypothetical situation in which a father is teaching his rev-head son to drive the family's grey-engined Holden, so he can go for the test on a manual car.  This would perhaps be the ideal device . . .

Rob

[hsv-001]

I worked with a builder with a trailer mounted sideplate and he powered a Lincoln welder and an air compressor , but he just used 2 base plates [throttle bodies] under his carby with specific idle settings and  throttle solenoids when the compressor or welder kicked in . 

[ACE]

I recall seeing rev limiter rotor buttons on 70s-80s era BMWs,VWs and Mercs with Bosch distributors.
ACE  8)

[ardiesse]

OK.  So the rev-limiting rotor wasn't just a niche product for industrial applications . . .

Rob

[RET]

The grey motor in Dad's blue FC that we drove to the Adelaide Nationals in '99 had a rev-limiter in it. Unlike this one, it was mounted in the front lobe of the crankshaft. When it was triggered, it ejected the harmonic balancer, which reduced the RPM quite dramatically. And permanently.

We all laugh about it now. Wasn't so funny 40 miles out of West Wyalong. At least we were on our way home.

[mcl1959]

That sounds a bit like the rev limiter that most grey engines have which arbitrarily removes teeth from the timing gear depending on how far over-revved the engine was at the time.
Car can be reasonably quickly restored by carrying the NASCO rev-restoring kit consisting of timing gear and associated pullers and pushers.

Ken ::)

[Harv]

That sounds a bit like the rev limiter that most grey engines have which arbitrarily removes teeth from the timing gear depending on how far over-revved the engine was at the time.
Car can be reasonably quickly restored by carrying the NASCO rev-restoring kit consisting of timing gear and associated pullers and pushers.

Ken ::)

Wish I had of known about the NASCO rev-restoring kit 5 years ago... would have saved the FB a drive home on the back of a tilt-tray  :D

Cheers,
Harv