Subject: Re: Intermittent starter problem
Author: Patrick Hayes
Date: Jul 6, 2005, 4:22 PM
Post ID: 1719124650
Lannis wrote:
| Suppose, just suppose (now this is just a rhetorical question, I didn't REALLY destroy the old gasket and neglect to put another one in), that someone (some other guy, call him Clem since we're just pretending) DID tear up the old gasket and throw it away and forgot to put another one one. (What a dummy he'd be, supposing there was such a feller, eh?). |
Dear Lannis: Please tell your pregnant friend that A: I don't have any,
and B: the thickness is far more important than the material one would
use. Its just a simple water and dirt seal to preserve the internal
copper contacts. No real tendency for water penetration unless you wash
with a pressure washer. IIRC, it was like the cardboard sheet you find
inside a fancy new dress shirt to form it and make it look presentable
for sale. I suppose if one found some cardboard material like this, one
could stack it to the correct thickness and use light silicone seal on
all surfaces. Anyone have a good original gasket to measure for Lannis'
friend?
Here's the physical scoop and why you need the gasket. Shrink yourself
down like in the sci-fi films and stand inside the solenoid end cap.
Add electricity and the electromagnetic solenoid pulls the plunger to
the rear coming at you fast. While doing so, using a lever system, the
plunger forces the starter pinion forward toward engagement with the
flywheel ring gear. As the solenoid pulls the plunger back further, the
huge "T" bar on the end of the plunger gets planted against the two huge
copper plate contacts inside the solenoid cap. One of these is battery
and the other is starter. Suddenly a huge spark and the starter motor
starts spinning. (BTW, it is this huge contact spark which slightly
burns, melts, abrades, deforms the contacts with each use and desposits
burn dust on the surfaces. Eventually the source of intermittent
action.) If everything works as designed, the pinion will already be
engaged into the ring gear and we start rotational work.
Now, rebuild the solenoid, but omit the cap gasket. (Not pointing any
fingers.) Just for for grins, lets say the gasket was 3mm thick. By
omitting the gasket, you have inadvertently moved the cap and its
contacts forward by 3 mm. Therefore, when the plunger comes flying aft,
the huge contacts will get bridged and begin conducting while the
plunger is 3mm LESS retracted than had been designed to do. There is
some lever magnification here, but you can see that also the pinion gear
will be LESS inserted (probably more than 3mm less) into the flywheel
ring, perhaps even not at all.
Now that strong motor is going to start spinning and you'll begin using
it as a die grinder to remove the tips of the flywheel ring teeth. Cool
huh?
On the good side, if you made the gasket too thick, like 5mm. You would
insure complete pinion/ring penetration, but you then risk having the
"T" bar connector on the solenoid plunger not actually reach all the way
back to the contacts or maybe just reach with very weak spring pressure
to support the connection reliably.
A gasket of design thickness is ideal. Missing that, you are better off
a little too thick than a little too thin.
Patrick Hayes
Fremont CA