Earthstar Forums

Ahhh, a great weekend of flying, but thats for another time.

I found a crack in the exhaust pipe line from the cylinders to the
mufflers. There appears to have not been enough flex in the piping
and over the past couple of years it finally took its toll and
cracked. Looking at other muffler systems there seems to be the use
of ball joints to help prevent just this same type of thing from
happening. The lack of flexibility and constant turning of the
piping finally took its toll on my setup.

Just thought I'd bring this up so you builders can plan for this and
for those others of you who haven't you can keep an eye out for this.

Jim C

--- In ThunderGull@yahoogroups.com, "Jim C" <jimc@d...> wrote:
> I found a crack in the exhaust pipe line from the cylinders to the
> mufflers. There appears to have not been enough flex in the piping
> and over the past couple of years it finally took its toll and
> cracked. Looking at other muffler systems there seems to be the use
> of ball joints to help prevent just this same type of thing from
> happening. The lack of flexibility and constant turning of the
> piping finally took its toll on my setup.
>
> Jim C

I'm sorry to hear that, Jim!

Do you have the same kind of exhaust system that is in the photos
that I put in the HKS folder in the Yahoo photo section? The reason
that I am asking, is that EarthStar sells two different exhaust
sysyems for the ThunderGull HKS engine option. I don't think that
either one of them use ball joints like the Rotax two-strokes do. I
have the same exhaust system that is shown in the photo section, so
I am wondering what to expect down the road.

Thanks!
--Dave

--- In ThunderGull@yahoogroups.com, "derbaier" <dershu@s...> wrote:
>
> Do you have the same kind of exhaust system that is in the photos
> that I put in the HKS folder in the Yahoo photo section?

The one shown in the pictures is the setup I have.

Not sure yet of the mods I am going to do, but I'll let you know.
Another guy with the HKS with a different muffler setup has had
cracks three times. He said HKS told him he needed to make it more
rigid and he also put ball joints in. Says he hasn't had an issue
since then. Not sure yet what I'm going to do, but I'll let you
know. I did a field repair and made it back home with no problems.

I don't know what size pipe you have but Mark Smith has the Rotax size
ball flanges in stock, cheap. My old Rotax engines wouldn't crack on
local flights, but would on a 2 hr run. I had problems until I installed
the double flange manifold. Not another crack.

Jay D

--- In ThunderGull@yahoogroups.com, "Jay D" <jdewberry@p...> wrote:
> I don't know what size pipe you have but Mark Smith has the Rotax size
> ball flanges in stock, cheap. My old Rotax engines wouldn't crack on
> local flights, but would on a 2 hr run. I had problems until I installed
> the double flange manifold. Not another crack.
>
> Jay D
>

I had them on my Rotax 503 on the Challenger I had as well and never
had a problem either. I went just under 2 years (@ 200 hrs) with
this setup, and never really thought about it being a big problem
until this mishap. I was actually in the process of looking at ball
joints and a couple of other things that were swirling around in my
mind as things I should look into a little more closely. This one
caught up to me. It's funny how everyone with the problem tells you
about it after you have it. Kind of wish I knew it was more of an
issue beforehand.

Jim C

Jim, sorry to hear about the cracked exhaust. Is there any chance you
will be able to make it down to the Flying Gators Flyin? I would love
to see a Gull 2000 "in the flesh" and will be flying up to Gator
field weather permitting. Sure hope you can make it!!!!

My original plans were to go to Lucedale, however, I'm not sure I'm
going anywhere this next weekend. I may not have the repairs
completed by then looking at what I have to do to repair it correctly
instead of just makeshift.

Unacceptable! :)
I might have to swing by your way and patch it up. You're not gonna
leave me there with Chad.

Jay D

--- In ThunderGull@yahoogroups.com, "derbaier" <dershu@s...> wrote:

> The reason
> that I am asking, is that EarthStar sells two different exhaust
> sysyems for the ThunderGull HKS engine option. I don't think that
> either one of them use ball joints like the Rotax two-strokes do. I
> have the same exhaust system that is shown in the photo section, so
> I am wondering what to expect down the road.
>

Dave,

I am getting an updated version of my system from Mark. It is the
one with baffles and cereamic coating that is supposedly quieter -
Same style overall. He said he and others had the same issue that I
have and so he has made improvements. It is one piece. Mine was
separated at where the muffler and exhaust pipes came together on
both mufflers (I have had to do repairs at both of these points).
This caused vibration and some major league wear and tear at the
muffler itself, which then led to the cracks in the X joint
downstream where I now have big time cracking (probably due to the
ongoing twisiting - usually pretty rough at engine startup). He said
the one he has on his plane now has over 450+ hours with no problems.
I'll be getting this and putting it on this coming week (hopefully) -
I'll let you know how it comes out.

As far as how long it will last, right now I only have the hearsay of
what I have been told above, we'll see how this works - I am very
hopeful though. It's already less parts to mess with and I like
that. I'll keep an eye on it for a while - Ball joints and a second
attach point downstream may still be an option, but the rigidity of
the new system may be the better point. I hope so anyway.

Jim

Another thing to consider is to have your prop dynamically
balanced. The process is to place an accelerometer on your engine
and place some reflective tape on one of the props. The
accelerometer fires every time the heavy prop/engine passes
the accelerometer and lights up a strobe. The person doing
the balance can then see which prop is heavy. This is much more
accurate than static prop balance.

I have a two-cycle engine but was still able to reduce my engine/prop
vibration by half (.8 g to .4 g at which point the remaining
vibration came from the engine) You can have even better results
with a 4-cycle. My engine and prop run noticeable smoother and
I have substantially reduced vibration wear.

Cost about $150 in Portland, Oregon and is well worth the cost.

-Alan