The solenoid on my Detroit, as well as well as functioning as a switch, also
has an arm that moves the pinion into engagement with the ring gear.
The starter also has a clutch between the starter shaft and the pinion that
allows the pinion to be driven only one direction by the starter motor. When
the engine starts the pinion is driven faster than the starter motor but spins
on the shaft thanks to that clutch. When the solenoid is deactivated it
withdraws the pinon from engagement with the ring gear with the engagement arm.
I use a relay (activated by the line from the start switch) at the solenoid to
insure the solenoid gets enough current to do its job rather than feeding the
solenoid via a long wire from the start switch.
Some solenoids do not use this arm to engage the pinion with the ring gear, but
rather use a spiral clutch between the starter shaft and the pinion that uses
inertia of the pinion to propel it along the shaft and into engagement with
the ring gear. When the engine starts and the load comes off the pinion a
springs returns the pinion to its initial position.
Norm
S/V Bandersnatch
Lying Julington Creek
30 07.695N 081 38.484W
----- Original Message -----
From: Peter Kafer
To: [email protected]
Sent: 8/10/2008 10:44:16 AM
Subject: Re: [Liveaboard] update - motor doesn't start!
This is not exactly correct. The bendix is indeed the mechanical device that
causes the starter's pinion gear to mesh with the engine's flywheel. When the
shaft of the starter motor spins, the pinion gear is thrown outward along the
shaft to engage the flywheel. When the fly wheel is spinning fast enough (when
the engine starts), the pinion gear is thrown back along the shaft, disengaging
the the pinion. The solenoid is an electromechanical device that is essentially
a switch. By applying a small current to the electro-magnet, the switch (heavy
contacts) is closed which allows a large current to flow from the battery to
the starter.
Peter
s/v Now or Never!
P323
----- Original Message ----
From: Philip & Marilyn <[EMAIL PROTECTED]>
To: [email protected]
Sent: Sunday, August 10, 2008 7:09:11 AM
Subject: Re: [Liveaboard] update - motor doesn't start!
A small point:
A bendix spring and a solenoid are different methods by which the starter motor
pinion gear is made to engage the ring gear on the flywheel..
They are not used together, Both are systems whose purpose is to engage the
pinion gear with the flywheel on the engine.
A solenoid is a electro-magnetic device which drives the pinion into the ring
gear on the flywheel.
A bendix spring is a purely mechanical device relying on a loaded spring and
centrifugal force to do the job.
I believe what we are dealing with here is a solenoid.
Philip
"Be the change you want to see"
Philip & Marilyn Lange
AE4OV & KD4JRC,
ORYOKI
Witness 35 Catamaran
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