 Courtesy of http://www.tcsn.net/mswihart/mark/files/muffler_spring_stuff.txt
One of the least expensive and most costly items on a Rotax aircraft engine are the exhaust
springs. While they only cost about $5.00, they can cause hundreds of
dollars in damage, and possibly death, if they go through a propeller!
Your not done installing your Rotax engine until you safety wire the springs
that hold the flex ball joints together and squirt a good strip of
automotive red high temp (RTV) silicone gasket sealer down the length of
the spring.
The safety wire must pass thru the center of the spring and both ends
of the hook attachment points. The reason for the safety wire is to keep the spring out of the prop should
it break or come unhooked. The RTV
 keeps the spring from vibrating which
contributes to their breaking, and holds all of the pieces together,
especially the exhaust hook TIPS.
Using pliers to install the springs causes nicks which contributes to their
breaking later. Use of a spring puller is suggested. It is tool that
looks some thing like a screw driver which has a hook on the blade end used
to grab the hook end of the spring when installing or unhooking the
spring.
They may be straight or L shape - the L gives you more
leverage.
The tool could be fabricated our of some metal banding like
they use to band crates for shipping or a flat blade screw driver by
putting a notch in the side of the flat part.
Depending upon kit manufacturer or engine supplier, the spring fastening
loops may not be installed on the exhaust system or may have to be
moved.
As an alterative there now is available a kit for fastening ball
joints together that has some advantages over the use of spring but may
eliminate need to weld loops on the exhaust pipes. Ask you kit
manufacturer if any modifications are required to standard Rotax exhaust
system.
A hockey skates-lace puller works really well for pulling the spring.
Made my tool out of a pull handle for the emergency brake in the car. Cut
it out of a junker. Leave it about 10" long. Bend a tight crook on the end
of the wire. Done, cheap and simple. The molded plastic handle makes a
great handle for pulling.
I use a short piece of safety wire tied in a four inch end to end
loop. The flexibility of the safety wire allows me to install and
un-install springs with ease. For a handle, I use a medium size phillips
screwdriver.
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| Maybe not the neatest thing to look at but it
works. |
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| Heat shrink installation, two globs of
silicone still need to be installed on each end of the spring hook. |
The wire may also be removed easily from springs in difficult
locations too.
If the springs are stretched more than 1/4 of an inch, they are
placing way too much load on the ball joints, creating wear that is
unnecessary. be careful when welding the tabs on the various parts.
Rather than use safety wire, I use one length of 1/16" flexible cable on
each exhaust joint that I lace through each eyelet and spring, and then
swage with a nico press.
I find this much easier, and consider it to be
stronger. I also make sure there is a bead on each spring, and at each
junction of cable and eyelet to prevent chaffing by the cable.
I also made a spring installer/removal out of an old flat blade screwdriver
I cut a short slot at a 45 degree angle into the blade. I used a cutting
blade on my small hand grinder and it took less than a minute to make.
This
tool works good, and virtually cost nothing but an old screwdriver that was
only good for opening paint cans!
Rotax
exhaust - Ball Joint Conversion Kit.
This simple bolt-on kit installs in minutes and
eliminates all custom placement and welding of standard Rotax exhaust
hooks. A matching pair of stainless steel half brackets surround the
existing exhaust pipe and are secured with AN fasteners and hi-heat
lock nuts.
AN3 bolts and SS springs tension the brackets to provide a firm yet
flexible joint. Also eliminate the large diameter springs that can
break and strike prop.
Sold in kits per joint.
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Click here for more information. | 
