The Murphy Builders Site

G'day

I need some help please!

I am running the Rotax 100 hp engine and it is fitted with the exhaust
systems as supplied by the Murphy factory which consists of a separate
muffler for each side. The pipes from the exhaust ports join the mufflers
with a ball jointed fitting held together with springs. The mufflers are
unsupported and hang from the exhaust pipes.

I have had nothing but trouble with them and on my last trip away I had an
unscheduled landing in a farmers field. Luckily we were near civilisation
and managed to get some temporary welding done so that we could get home.
Its amazing what can be done with one spanner, a multi tool, a screwdriver
and some fencing wire!

Now my question is, what exhaust system are other Rotax users using? There
must be a better way than what I have now!


Regards and thanks


Ian Donaldson






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Ian, for the 912S to operate properly you really should have the 4 into 1
Rotax exhaust...but we know this would be an installation nightmare. To use
the two separate exhausts you have I have found that they hold up better if
you can get an angle (3/4 x 3/4 ie 19mm x 19mm) clamped across between the
two separate exhaust stacks to get them to quit swinging around so much.

Wayne

----- Original Message -----
From: "IAN DONALDSON" <allsure@bigpond.net.au>
To: <rebel-builders@dcsol.com>
Sent: Monday, April 04, 2005 1:19 AM
Subject: Rotax 912s exhaust system

G'day

I need some help please!

I am running the Rotax 100 hp engine and it is fitted with the exhaust
systems as supplied by the Murphy factory which consists of a separate
muffler for each side. The pipes from the exhaust ports join the mufflers
with a ball jointed fitting held together with springs. The mufflers are
unsupported and hang from the exhaust pipes.

I have had nothing but trouble with them and on my last trip away I had an
unscheduled landing in a farmers field. Luckily we were near civilisation
and managed to get some temporary welding done so that we could get home.
Its amazing what can be done with one spanner, a multi tool, a screwdriver
and some fencing wire!

Now my question is, what exhaust system are other Rotax users using? There
must be a better way than what I have now!


Regards and thanks


Ian Donaldson






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Ian,

There used to be a good picture of the exhaust and muffler on my 912S
Rotax/Kitfox but all was lost when the server went down a few years back. I'll look
and see if I still have it on a disk. You can probably see and order it from
Skystar Aircraft Co. Check their web site;

Skystar.com

It has 225 hours without a mishap.

Bruce




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Ian,

I found the picture, send me your email address off line.
_legeorgen@aol.com_ (mailto:legeorgen@aol.com)

Bruce




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Hi Bruce !

Please post it to the archive files, too - Rotax exhaust systems
will become a larger interest soon ! ;-)

......bobp

-------------------------------orig.-------------------------
On Monday 04 April 2005 11:06 am, Legeorgen@aol.com wrote:

Ian,

I found the picture, send me your email address off line.
_legeorgen@aol.com_ (mailto:legeorgen@aol.com)

Bruce




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Hi Ian !

We had a lot of fun with our 912 exhaust too !! Some things I
found that helped were:

Install TWO springs instead of one, in ALL locations - this
stopped the annoying habit of popping the muffler off of the pipe,
with it hanging on the lip, after sudden applications of power
(go-arounds).

Run a piece of locking wire up inside the spring, connecting
the 2 welded spring loops loosely. The locking wire will hold the
muffler on, even if the spring breaks. Got this one from the
2-stroke boys, who have a LOT more vibration & spring failure !
They also run a line of high-temp. silicone sealer up the side of
each spring, tieing the coils together with the flexible adhesive.
This damps the vibration within the spring, adding greatly to
life.

We added a gear clamp to the rear down pipe from the
muffler, with a strap & spring running to the mount, to support &
tension the muffler, damping rotation, but leaving lots of
movement. This held the rear of the muffler up a bit,
helping keep it tight on the manifold.

All that done, we had few problems for the balance of
10 years of flying. Wayne's right, though - if you use the
proper Rotax 4-into-1 exhaust, where all the pipes run into
a large tank at the rear, and one pipe exits at the bottom,
you will have a quieter airplane, and probably gain at least
2 or more HP !! This CAN be done on the standard mount -
there are a couple of builders in Ontario who are almost
ready to fly - will try to catch up to them & get photos.
Might take a while, though - they are a couple of hundred miles
away, and I have no email for them ..... :-(

.......bobp

-------------------------------orig.-------------------------
On Monday 04 April 2005 01:19 am, IAN DONALDSON wrote:

G'day

I need some help please!

I am running the Rotax 100 hp engine and it is fitted with the exhaust
systems as supplied by the Murphy factory which consists of a separate
muffler for each side. The pipes from the exhaust ports join the mufflers
with a ball jointed fitting held together with springs. The mufflers are
unsupported and hang from the exhaust pipes.

I have had nothing but trouble with them and on my last trip away I had an
unscheduled landing in a farmers field. Luckily we were near civilisation
and managed to get some temporary welding done so that we could get home.
Its amazing what can be done with one spanner, a multi tool, a screwdriver
and some fencing wire!

Now my question is, what exhaust system are other Rotax users using? There
must be a better way than what I have now!


Regards and thanks


Ian Donaldson






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Ian and Bruce, I had the side by side setup for the first 2-3 years and also
had lots of problems. We then made a custom 4 into 1 SS exhaust and has been
fine now for 2 years. It is a bit of a nightmare fitting it though. I had
the muffler made up by some car shop in southern Ontario and then found and
inexpensive (real cheap) source for SS tubing, which also came with 45
degree piping. It was a shop that made grab bars for handicapped washrooms.

I plan to go out this week to start my spring maintenance and will snap a
few shots for you.

Aurele
R063

P.S. Bruce, I'd like to see those pics also of your installation if you can
send to acerebel@ntl.sympatico.ca


----- Original Message -----
From: <Legeorgen@aol.com>
To: <rebel-builders@dcsol.com>
Sent: Monday, April 04, 2005 11:06 AM
Subject: Re: Rotax 912s exhaust system

Ian,

I found the picture, send me your email address off line.
_legeorgen@aol.com_ (mailto:legeorgen@aol.com)

Bruce




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I loaded 2 pictures of my 912S exhaust and muffler to the list. This is the
system Skystar sold me with their FF kit for the 912.

Bruce




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Mike,

The 912S exhaust pictures load half way then stop. Am I doing something
wrong?

Bruce




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G'day Aurele

Thanks for the reply.

I sure would like a few pictures of your installation. I think that the best
way to go is to replace the separate mufflers with a four into one system.

As well as posting them to the archive files would you please send them
direct to me at allsure@bigpond.net.au


Thanks

Ian Donaldson

Ian and Bruce, I had the side by side setup for the first 2-3 years and
also
had lots of problems. We then made a custom 4 into 1 SS exhaust and has
been
fine now for 2 years. It is a bit of a nightmare fitting it though. I had
the muffler made up by some car shop in southern Ontario and then found
and
inexpensive (real cheap) source for SS tubing, which also came with 45
degree piping. It was a shop that made grab bars for handicapped
washrooms.

I plan to go out this week to start my spring maintenance and will snap a
few shots for you.

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G'day Bob

Thanks for your interest.



I have two springs at each joint and have also lightly secured the tail
pipes with a flexible bracket onto the engine mount.

The springs are also wired and I have some sealant inside the springs.

In my last failure both the front exhaust pipes broke in the bend close to
the exhaust port. On one side a piece broke clear out and it was found
dangling in the cowl when I landed. The vibration had caused the safety wire
to cut through also! Thankfully we were able to retrieve the broken part and
after a lot of drama got it welded and put back in place. We were lucky that
it failed where it did as we were in gliding distance of a small town and
help was available. Anywhere else and we would have been in for a long walk.
Our outback is like the Canadian wilderness except for the fact that where
you have ice, snow and water we just have desert! I don't know which would
be friendlier to a downed pilot!

I am going to the hangar now and see if Wayne's idea of a bracket between
the pipes will help in the short term. I would like to get a fix done for a
fly away at the weekend, but it is also over large tracts of unpopulated
country and I don't want to have another emergency landing in country like
that.

Bruce has sent a pic of his installation in a Kitfox and Aurele is going to
send some of his also. I would also appreciate it if you could also get a
few pics. I think the long term fix will be a four into one system that is
if I can work out how to fit it in the cowl!

thanks and regards

Ian Donaldson
:

Install TWO springs instead of one, in ALL locations Run a piece of
locking wire up inside the spring, !
They also run a line of high-temp. silicone sealer up the side of each
spring, > We added a gear clamp to the rear down pipe from the muffler,>
will try to catch up to them & get photos.

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Hello Ian,
Welcome to the scrub flyers association; if it can't be fixed with a good
bit of fencing wire than she is definitely broke!!!!. And they keep sayiny
that rotax's are not rotaxcarcus, but lycomings are lyocarus!!!
Kind regards,
Greg.
VH-LCX & Elite 724(working on the wings)





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G'day Greg

Surprisingly we did use a length of wire to pull the remaining springs into
place and then twitched a piece to replace the spring that went missing.

We kept a length of wire in the plane "just in case" and it came in handy
when a piece of luggage became dislodged and slid rearward in flight! It was
just the thing to reach back and haul the bag back into place. But it did
require my passenger to undo his seat belt, turn around and lean over the
back of the seat. As he leaned backwards the c of g changed and the nose
pitched up, but that was easy enough to control. However the difficult bit
came when he was turning around again and managed to get his foot caught on
the control column and pushed the stick full forward! That gave us a lot of
negative G and a good look at the ground!

Never a dull moment!


regards

Ian

Hello Ian,
Welcome to the scrub flyers association; if it can't be fixed with a good
bit of fencing wire than she is definitely broke!!!!. And they keep sayiny
that rotax's are not rotaxcarcus, but lycomings are lyocarus!!!
Kind regards,
Greg.
VH-LCX & Elite 724(working on the wings)

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Sometimes welding stainless is a very temporary repair. Beside the weld
bead will be brittle and crack fairly soon unless it is welded with a
technique that shields the molten metal from oxygen. TIG is acceptable
as is MIG if gas shielding is used (argon cylinder and regulator). I
think a torch can also be successfully be used if one knows how. However
there is also the backside of the weld (inside the pipe). The inside of
the pipe can be purged with argon which means that the ends of the pipe
are sealed and argon is flowed through it during the weld. Or there is a
Solar B flux that works well if you have access to apply it to the back
of the weld. This may be common knowledge but I've been in small shops
that don't protect the backside of stainless during welding and you know
their stuff is not going to have a long life.

Other things: 321 series aviation exhaust should outlast the more
common cheaper commercial 308 series or the 4xx series that cars use.
321 forms brittle carbides slower than the other types while in service
and resists high temperature better. Also the material will be markedly
thinner where it has been stretched on the outside of mandrel bends. If
problems occur in the bends it probably makes sense to use gentle bends
rather than tight bends. And of course bumping up from 0.035 wall
thickness to 0.049 may help. Burn's stainless has a good website and is
a source of material.

Ken

IAN DONALDSON wrote:

G'day Bob

Thanks for your interest.



I have two springs at each joint and have also lightly secured the tail
pipes with a flexible bracket onto the engine mount.

The springs are also wired and I have some sealant inside the springs.

In my last failure both the front exhaust pipes broke in the bend close to
the exhaust port. On one side a piece broke clear out and it was found
dangling in the cowl when I landed. The vibration had caused the safety wire
to cut through also! Thankfully we were able to retrieve the broken part and
after a lot of drama got it welded and put back in place. We were lucky that
it failed where it did as we were in gliding distance of a small town and
help was available. Anywhere else and we would have been in for a long walk.
Our outback is like the Canadian wilderness except for the fact that where
you have ice, snow and water we just have desert! I don't know which would
be friendlier to a downed pilot!

I am going to the hangar now and see if Wayne's idea of a bracket between
the pipes will help in the short term. I would like to get a fix done for a
fly away at the weekend, but it is also over large tracts of unpopulated
country and I don't want to have another emergency landing in country like
that.

Bruce has sent a pic of his installation in a Kitfox and Aurele is going to
send some of his also. I would also appreciate it if you could also get a
few pics. I think the long term fix will be a four into one system that is
if I can work out how to fit it in the cowl!

thanks and regards

Ian Donaldson


:

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G'day Ken

Thanks for the information regarding stainless steel welding.

However the system that I have at the moment is just mild steel that I have
welded with a torch. I was considering making a stainless 4-1 but I think
that I will stick to good old fashioned mild steel!

Regards

Ian Donaldson

Sometimes welding stainless is a very temporary repair. Beside the weld
bead will be brittle and crack fairly soon unless it is welded with a
technique that shields the molten metal from oxygen. TIG is acceptable
as is MIG if gas shielding is used (argon cylinder and regulator). I
think a torch can also be successfully be used if one knows how. However
there is also the backside of the weld (inside the pipe). The inside of
the pipe can be purged with argon which means that the ends of the pipe
are sealed and argon is flowed through it during the weld. Or there is a
Solar B flux that works well if you have access to apply it to the back
of the weld. This may be common knowledge but I've been in small shops
that don't protect the backside of stainless during welding and you know
their stuff is not going to have a long life.

Other things: 321 series aviation exhaust should outlast the more
common cheaper commercial 308 series or the 4xx series that cars use.
321 forms brittle carbides slower than the other types while in service
and resists high temperature better. Also the material will be markedly
thinner where it has been stretched on the outside of mandrel bends. If
problems occur in the bends it probably makes sense to use gentle bends
rather than tight bends. And of course bumping up from 0.035 wall
thickness to 0.049 may help. Burn's stainless has a good website and is
a source of material.

Ken

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