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Fan Tower Cracks
I developed some cracks (two) in my engine’s fan tower case. This is
on a Rotax 503. The cracks developed until one piece broke off. When the
piece broke off the starter housing (GPL) fell away from the engine case
and the starter gear "chewed-up" the ring gear.
A friend welded
the case for me and I bought a new ring gear. The case is now better than
"new" and the starter works O.K., again. My friend also filled
in the notch, in the case, that is needed for the Rotax starter. One of
the cracks started in this notch. It’s a good idea to keep a lookout for
cracks starting in this area of the case.
I'm going to need a new ring gear, too. Last night, after flying to a
local airport, I attempted to start my engine. The starter motor spun
around freely but didn't engage the engine. A friend prop started my
engine and I flew home. After pulling the starter motor and examining
the starter case, I saw that the fan housing had cracked in two around
one bolt, one of the long, starter housing bolts had broken, the short
bolt in the starter opening had broken, and the ring gear teeth were
chewed off in places. GPL starters put way too much stress on the
engine case, IMHO. I know of several people who have replaced the long
starter housing bolts after they snapped off. I'd go to a pull starter
if I could keep the engine running until I could get into the cockpit.
My chokes and primer can't be reached from where I'd have to pull the
rope starter. Looks like no flying until I can tear the engine apart
and wait for parts. I thought about having the fan
housing welded, locally, but I don't know how it would hold up. Any
thoughts?
The following starter is widely used on Challenger and other ultralight
aircraft where the standard Rotax starter won't fit.
I have 8 reports of this problem, this is the latest report - as I
received it.
Dave:
GPL Enterprises, Inc. manufactures after market products. They have a
starter assembly which allows you to keep the rope starter and have an
electric starter also.
However, the starter is mounted at the 11 o'clock
position. Rotax starters are mounted at the six o'clock position. I found a
repair bulletin on the net which described my problem to a T. My lower
case has broken three times on the exhaust side of the engine.
The following was taken off the web:
I tried installing a GPL starter on a 532 last week. The kit was specified
for the 377, 447, 503, and points 532. The problem started when the blue
spacer called for in the instructions did not have a deep enough recess to
allow the register flange on the flywheel to NOT bottom out, thus the
spacer was sitting on the register, n the face of the flywheel/spacer
area.
The spacer actually teetered on the alignment flange on the flywheel.
So I used my lathe to deepen the recess, allowing the spacer to sit firmly
on the flywheel face. Had to take out fifty thou or so. This was the 'four
long bolts' type starter housing.
It installed fine as did the spacer and the ring gear and starter
adapter. But when the bendix gear was pulled into mesh with the ring gear,
the teeth barely touched at all, just enough that if the tooth was
straight out, it would catch, and as it turned ever so slightly, would
becomes totally disengaged. I then installed a fan pulley knowing this
would extend the ring gear , improving the mesh.
The teeth now engaged, but still had a LOT of rotational play in the
bendix drive gear against the ring gear. I then removed the starter adapter
and the gear and placed some 1/4 inch AN washers against the blue adapter.
Upon reassembly, the gear teeth on the bendix and the ring gear engaged
perfectly, some small clearance obvious and easy turning full
circle.
I called Gary Lutke of GPL, and he stated the spacer was too thin and
in about 1 percent of the 532 engines the silver spacer is required. As I
hung up the phone, my customer called and said the starter housing
interferes with a cross member on his avid flyer and he would need the
rotax starter after all.
BTW, the difference between the blue and silver spacer was exactly the
.120 that I had added to the total stack up of parts,,,, I just hope the
silver spacer also has a deeper recess for the flange on the
flywheel,,,,,but don't need it after all,,,,,
If electric start is installed, a modification may be needed on the 447
and 503 engine installations. On some, 5% +, Rotax engines the spacer that
comes with the GPL starter kit is too thick and .050" of material
must be milled off the surface.
If the spacer is not milled, the starter ring gear and bendix gear will
jam together and the starter will not work, all the time, or drag. If you
have this problem, GPL will mill .050" off the spacer at no
charge.
Also, if the engine turns over slowly, with a fully charged battery,
check to see if a lead to one of the four brushes, in the starter, has
broken off. Pull the end of the starter off to check.
I just installed my Starter last night. Here is a few things that I
discovered:
1) You should know that you need to put a round small bar in the
vacuum port to hold the engine from turning while you remove and install
screws.
2) The gear and spacer is held on with 1/4-20 socket head bolts that
you can only torque of you cut the straight part of an allen wrench off
the use a socket on that.
3) The bolts that hold on your rope starter cup are hex head and the
side of your socket will hit on the side of the cup and push the socket
off. The solution, replace the bolts with socket head like the rest of the
bolts.
4) Be sure that you very carefully torque the long bolts that hold
on the outside casting and the rope starter, and use the 242 lock tight.
Use the low end, the 10lbs. as the Rotax casting has been known to crack.
(This is a $200 to $400 fix if you crack the case)
5) I also drilled the two bolts that hold the starter on for safety
wire, my choice.
One last thing, if you do replace the hex head with socket head, make
sure that they are flush with the back of the flange that you are screwing
to as the starter bendix will hit bolts that extend through.
Since I have not had the HHF 503SC running since
October, one day in Jan.,I heard the weather man say that the next day it
was going to get above the freezing temp. So I put the battery on charge
for the night. The next day it got to 35°. I decided to take the flying
machine out of the garage and start the eng. and get it up to temp. and
then put it back in the garage for the next time it gets warm. The problem
started when I pushed on the starter button. It turned over a few revs,
started, and then died. I pushed the starter button again and the same
thing happened, it died, but THE STARTER WAS STILL RUNNING. I did not have
access to the relay to hit it. I tapped on the starter but it kept
running. Then I started running. I got some tools from the garage and
proceeded to disconnect the battery. Of course, I worked on the battery
ground terminal, and got the starter & everything else shut down. After a
while I tried to make contact again to the battery. As soon as I touched
the battery with the wire the starter turned again. Now this told me that
the relay was stuck. I put everything back in the garage; I decided to let
things set for a few days. One night I got on PalTalk and I brought this
problem up in a PPC group. There was a question & answer session for a
while and the cure was to replace the relay with one that is used for
cars.
This was good that this happened the way it did. If I
were in the sky what would I have done? Would I have known that the
starter was still running when the Rotax was purring along during flight?
I think NOT! During the PalTak discussion I asked if anyone knew where to
buy an BATTERT DISCONNECT SWITCH. I did NOT trust any relay from this time
on. You can order a switch from NAPA (SW33), it was around $40.00. I
replaced the relay with one from NAPA (ST85), around $25.00. The GPL relay
is too small for the current draw that the starter took on this cool day.
I just want to thank "BigWheelHawaii" and the others that helped me find
the parts to fix this problem.
PS. Today it was warm around 60° and time to test the
mod. I got everything ready, pushed the starter button and nothing
happened. I for got to check the BATTERY DISCONNECT SWITCH it was in the
disconnect position. :-) Good test. I tried it again and it worked. I then
disconnected the SWITCH and everything still worked. I am using the switch
as a STARTER DISCONNECT. That way I can still use everything else.
You are not the first to have experienced this
problem. I described your situation exactly as one reason to consider
adding a battery master switch and solenoid in an article I wrote for
Ultraflight Magazine appearing in the December 2000 issue.
Me again. Something that I found regarding the starter. GPL claims that
Rotax is to blame for the tolerance difference on the bendix and ring gear.
Looking very CLOSELY at the starter housing, I noticed that the hole bored
for the mating of the starter motor to the housing is off center!!! When
the starter motor sits flush in position on the housing it is shifted off
the center line of the CAST mating surface by approx. 50 mil!!! Its going
to be an interesting convesation with GPL tomorrow! Furthermore, I believe
that GPL stated that they would be including information in with the new
starters that was to point out the possible problem of the spacer thickness.
( I dont think the spacer is needed because of Rotax tolerance. I believe it
has more to do with the boring of GPL's housing for the starter motor!) My
NEW starter that just arrived last week does not mention the possible
neccessity of milling the spacer. There is only mention of the turning of
the bendix by hand to check for fit as has always been in the instructions.
Couple other notes: I have yet to install a gpl and grind merely the lip off
the fan shroud as per their instructions. It usually neccessitates grinding
the shroud paper thin and also grinding some of the aluminum off the housing
in order to get them both to fit. Just for grins, I will also ask GPL who
manufactures a torque wrench that can be used on the two bolts that hold the
starter to the housing. They give the torque specs (sometimes wrong as we
all know) Getting tired of the Bull by after-market suppliers! Thanks for
letting me vent! : -)
Mike Harrison
Skyes the Limit!
Challenger Dealer
Arizona
When I helped to build my friends Challenger II last summer we also had to
grind down the blue spacer. But we didn't grind the screws down enough and
had to rewind the coil because the srew nicked the wiring.
Don
Mike, I had problems with GPL. Had the problem with the "blue thing",
and when I got the milled off replacement started to put things together
broke one of the studs that hold the casing in place. Was following
their instructions as to torqueing. They call out 13- 18 ft-lb (156 -
216 in-lb). I set torque for the middle of the range, and stud broke
off. Later found that Rotax calls out 90 in-lb for the same size bolts
that formerly held the pull starter in place. When another lister asked
them about this they conceeded that their figure was wrong. There was a
lot of discussion on the list about 6-8 months ago, and from the posts
it looked like the ratio was pretty much reversed with 5% having no
problem with the blue thing and 95% having to have it milled off.
There is also a problem with the screws that hold the blue thing in
place are too long, and come dangerously close to the wires of the coils
behind the flywheel. A number of people have had problems and had to
replace the coils.
I will say that they are in general cooperative when one calls them
about a problem. I think their problems could be fixed relatively
easily, and sure would like to see this happen.
gil leiter
MAPLEWOOD, MN
Mike, every single plane last year that I sold had a GPL starter installed.
That's 30 planes!! ALL spacers had to be trimmed!!!!! Even the starters that
would work with the no modified ring worked MUCH better and spun the motor a LOT
faster after the ring was trimmed. Also the teeth on the ring should be heavily
ground on with a wire wheel on a grinder to round off the UNFINNISHED very SHARP
teeth. If you don't, it will wear out the berndix gear very quickly. All in all
pretty shitty quality finish for a product that costs soooo much loot.
DZ |
