Alternator
Selecting an alternator has not been easy. I've been to the auto parts store
5 times and have ordered and returned two alternators from Vans. Basically
here is what I have found.
The 35 amp units from Vans are from a 1978 Honda civic. You can remove the
fan easily yourself. This unit costs $21 at the auto parts store plus $35
for a core. It requires an external regulator ($50), and does not last very
long due to vibration/heat. It MUST be cooled! These alternators can be made
to last longer if the unit is disassembled, and potting compound is applied
to the wires where they are welded on the diode leads. This reduces
vibration and will extend the life of the unit. Although these are initially
low priced, over the long term they are costly, when considering break
downs, need for regulators, larger pulleys to slow them down etc.
There are fantastic units out there. I narrowed it down to a 1987 Toyota
Camry and a 1987 Suzuki Samurai. The Toyota units ($99 lifetime warrantee)
is the same size as the cheapo Honda, but will withstand high RPM, has
internal regulation, and belts out an impressive 80+ amps. It also weighs
about a pound more than the Honda. This would have been choice had I needed
the power.
Not needing the power, I chose the Suzuki (Nippon Denso - $99 lifetime
warrantee) to power my ship. This little alternator is a jewel. It is tiny,
weighs very little, is internally regulated to 14.5V, has dual internal
cooling fans, makes 55 amps, can withstand high RPM, and has a solid
reputation for longevity when installed in a homebuilt.
A lot of people talk about alternators from a GEO Metro. I checked these and
they are identical to the Suzuki unit (Nippon Denso) except they come with a
serpentine belt pulley, requiring the builder to buy and install a V-belt
pulley.
So far the only problem I see, is that the available Lycoming boss mount
brackets won't fit the thing. I will need to fabricate my own bracket,
though not difficult at all.
Here on the left, is the
Vans 35 amp Honda (1978 Civic) alternator. On the right is the 1987 Suzuki
Samurai Nippon Denso 55 amp unit. In the foreground is the Vans bracket kit.
The small 2.5" pulley will stay. It turns the alternator about 7,000 rpm in
flight. Don't try that with the Honda!
Here is the problem with the
vans 35 amp bracket.
After many trips to the auto parts store, the alternator problem is finally
fixed. In a nut shell, here is what worked for my Rocket!
Alternator 1987 Suzuki Samurai $155
Bracket kit Vans Aircraft ES ALT-BKT $27
Grade 8 bolts $4
Belt NAPA 3L350W 9mm X 980MM $11
A couple of notes. I had to drill the bolt heads myself to size #40 for
.032" safety wire. I had to cut a bit off the long bracket to fit as it was
too long. I had to cut a bit off the tensioning arm as it was a bit too
long. The belt fits perfectly with the maximum amount of tightening still
available. This "should" clear the Rocket cowl but I don't know as I have
not got that far yet. I am using the large Lycoming drive pulley (about 9
3/4") and the small pulley that came with the alternator. I have heard from
so many people that the small pulley is OK, I am sticking with it!
Added note... this setup clears the Team Rocket cowl with miles to spare!
 
This is a simple diagram of how
I hooked up my unit. I have disconnected the "S" terminal and it works
perfectly. You may be interested to know... The idiot light (charge lamp)
only works when the "IG" terminal is powered. If the alternator were to fail
in-flight, turning off the power to "IG" terminal will extinguish the charge
lamp.
It "IGN SW" is my alternator switch.
The "S" terminal is a remote sensing terminal for the regulator. It is
intended to sense the actual voltage at the battery after wiring losses etc.
Then it adjusts the alternator to produce whatever is needed to end up with
the desired voltage at the battery. Connecting the "S" and IG" terminals at
the alternator will likely reduce the regulated output voltage of the
alternator to around 13.6 V, but I haven't tested that theory yet. As it is,
it puts out 14.5 V.
For you real tecnonerds...
The regulator will pass a few milliamps thru the charge lamp when operating.
If you use an ultra bright LED for and idiot light, it may glow even though
the alternator is working properly. A small resistor across the led will
bleed the drain current to give proper operation of the light.
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