Starter

The starter on the starboard engine on Fat Albert the Apache went
bad... I normally start the port engine first, per the handbook... A
local on the field commented that the starter on the starboard engine
was making grinding noises... Being inside the airplane with the port
engine running I did not hear it... I snooped around the starter and
sure enough I saw that the teeth on the bendix was worn back so far
that the teeth were barely engaging, slipping and skipping on the ring
gear... The rings were replaced 3 years ago and still look new (or
did)... The bendix gear on the port starter looks factory new yet...
Apparently the case hardening on the defective bendix gear failed and
the hardened ring teeth simply chewed the soft inner core of the bendix
teeth away within a short time period...
So, the usual decision process started.. I tried ordering just a
bendix... No number on my bendix so they could not cross reference it
over the phone - "ship the starter to us and we'll let you know"... No
thanks, I've been down that road before...
Also these Delco Remey starters are old.. A overhaul was over $300...
An exchange rebuilt was almost $400... So I looked at SkyTec.. They get
just shy of $500 for their NL model to fit the Apache... I ordered one
from Aircraft Spruce... Shipping was included...
Replacing the starter was simple matter of spinning the bolts... But
hooking up the electrical cable was not... The electrical post on the
SkyTec is about 4" forward of the stock location... The aluminum
starter cable (original) is as rigid as a piece of pipe... There is no
movement possible... So I got a piece of 2-0 copper cable and and big
lugs... Borrowed a battery cable crimper from the auto parts store and
custom built an extension to the starter cable...

The result is that the starboard engine cranks over like it is already
running... So I am happy with the result, if not with the bills... I
will get a bendix for the old starter and throw it on the shelf for a
spare...

denny

Denny wrote:
: hooking up the electrical cable was not... The electrical post on the
: SkyTec is about 4" forward of the stock location... The aluminum

We put a Skytec in our Cherokee a year or so back. At that time, I remember
they had a "kit" for some models. Something about a little jumper cable to fix the 4"
spacing problem on some installations. Sounds like you got bit.

Just for the record, the Skytecs are nice but have one drawback. Since
they're permanent magnet and don't include any flyback switches/diodes, the energy
stored in the rotor can only dissipate through the solenoid. That means that after
the engine starts, the solenoid keeps the bendix engaged for a few seconds while the
magnetic energy dissipates. To keep the engine from perpetuating the process by
running the starter as a generator, there's a sprag clutch on the bendix shaft so as
long as the engine is running faster than the starter motor does, it will die out.

I say this because it adds another wear and failure point. I definately
notice the starter staying engaged a bit after starting. I'm not thrilled at the
extra ring gear wear it induces. The really sad thing is that it can be easily fixed
with some minimal wiring changes, but it was certified as-is. Check their web page
for "alternate wirings" for experimental installations.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

And what's your tail number?


In article .com, says...

The starter on the starboard engine on Fat Albert the Apache went
bad... I normally start the port engine first, per the handbook... A
local on the field commented that the starter on the starboard engine
was making grinding noises... Being inside the airplane with the port
engine running I did not hear it... I snooped around the starter and
sure enough I saw that the teeth on the bendix was worn back so far
that the teeth were barely engaging, slipping and skipping on the ring
gear... The rings were replaced 3 years ago and still look new (or
did)... The bendix gear on the port starter looks factory new yet...
Apparently the case hardening on the defective bendix gear failed and
the hardened ring teeth simply chewed the soft inner core of the bendix
teeth away within a short time period...
So, the usual decision process started.. I tried ordering just a
bendix... No number on my bendix so they could not cross reference it
over the phone - "ship the starter to us and we'll let you know"... No
thanks, I've been down that road before...
Also these Delco Remey starters are old.. A overhaul was over $300...
An exchange rebuilt was almost $400... So I looked at SkyTec.. They get
just shy of $500 for their NL model to fit the Apache... I ordered one
from Aircraft Spruce... Shipping was included...
Replacing the starter was simple matter of spinning the bolts... But
hooking up the electrical cable was not... The electrical post on the
SkyTec is about 4" forward of the stock location... The aluminum
starter cable (original) is as rigid as a piece of pipe... There is no
movement possible... So I got a piece of 2-0 copper cable and and big
lugs... Borrowed a battery cable crimper from the auto parts store and
custom built an extension to the starter cable...

The result is that the starboard engine cranks over like it is already
running... So I am happy with the result, if not with the bills... I
will get a bendix for the old starter and throw it on the shelf for a
spare...

denny

Denny wrote:

Replacing the starter was simple matter of spinning the bolts... But
hooking up the electrical cable was not... The electrical post on the
SkyTec is about 4" forward of the stock location... The aluminum
starter cable (original) is as rigid as a piece of pipe... There is no
movement possible... So I got a piece of 2-0 copper cable and and big
lugs... Borrowed a battery cable crimper from the auto parts store and
custom built an extension to the starter cable...

Why isn't it a problem connecting dissimilar metals Cu-Al in a high-current
application like that?

I know of course that Al starter cables are used in lots of aviation
applications, and eventually they have to connect to some kind of copper at the
starter, but why isn't there a corrosion problem?

Dave Butler wrote:
: Why isn't it a problem connecting dissimilar metals Cu-Al in a high-current
: application like that?

: I know of course that Al starter cables are used in lots of aviation
: applications, and eventually they have to connect to some kind of copper at the
: starter, but why isn't there a corrosion problem?

There often is. That's why "copper battery cables" are high on the list of
desirable modifications. The galvanic corrosion causes (relatively) high
resistance.
In theory, aluminum battery cables are *great* on an aircraft... really good
conductivity at much less weight. Especially for long battery cables. Just need to
keep the corrosion problem at bay.

FWIW, electrical lugs are often rated for both Cu and Al.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

The lugs are steel and are plated with a metal that is less reactive to
both Cu and Al... Along with that I dip the cable end into antioxident
grease (NOALOX) before crimping the lug onto it... Then I wrap the
connection with self vulcanizing rubber (3M - at any electrical
distributor catering to contractors) to block moisture entry... The
cables on Fat Albert are of 1956 vintage (assembly date 1957) and the
original lugs look clean with no evidence of powdering, etc. at the
crimp point... Also, the fat boy is hangared in an insulated hangar,
other than on trips, which greatly reduces condensation corrosion of
interior parts...

On the "cable extension kit" I didn't see that and the sales lady
obviously never heard of it.. Actually, I like my 2-0 cable and lugs
better than what they would have likely provided... I just didn't like
the surprise of finding the gap which cost me a 3 day delay and an
additional 50 mile round trip to solve...

On the self induction current holding the solenoid in for 'seconds' - I
haven't noticed that but I will pay attention and let the group know if
I do see it...

denny

Denny wrote:
: The lugs are steel and are plated with a metal that is less reactive to
: both Cu and Al... Along with that I dip the cable end into antioxident
: grease (NOALOX) before crimping the lug onto it... Then I wrap the
: connection with self vulcanizing rubber (3M - at any electrical
: distributor catering to contractors) to block moisture entry... The
: cables on Fat Albert are of 1956 vintage (assembly date 1957) and the
: original lugs look clean with no evidence of powdering, etc. at the
: crimp point... Also, the fat boy is hangared in an insulated hangar,
: other than on trips, which greatly reduces condensation corrosion of
: interior parts...

Exactly... done right there's no reason why aluminum cables can't be used. If
done improperly (as most of the aging fleet are likely to have succumed to), it'll get
ugly.

: On the "cable extension kit" I didn't see that and the sales lady
: obviously never heard of it.. Actually, I like my 2-0 cable and lugs
: better than what they would have likely provided... I just didn't like
: the surprise of finding the gap which cost me a 3 day delay and an
: additional 50 mile round trip to solve...

Weird. The guy I talked with when we went to buy ours mentioned a few
different types. Maybe look it up pretending it's for a Cherokee?

: On the self induction current holding the solenoid in for 'seconds' - I
: haven't noticed that but I will pay attention and let the group know if
: I do see it...

Er... by "seconds" I guess I mean between 1 and 2 seconds. Not very long, but
it's a long time to hear the grinding/ringing of the ring gear driving the bendix
starter.

-Cory

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************