Subject: leaking oil - problem found
From: Rotary Engine
Date: 10/1/2007, 10:18 AM
To: AARotary Engine


Hello Paul-

So the cause of my leaking oil has been found.  I have determined
that
quite a few of the tapped oil pan bolt holes in AL parts have been
stripped.  I have not surveyed all the bolts - I'll be pulling the
engine off again to do that on Tuesday.  But I did find 4 already
that
are stripped.  I pulled the bolts out & they are fine.  But when
inserted, they cannot be torqued to the spec - they spin & spin...

So I suppose I could thin some JB Weld and re-tap the holes, but
given
my tapping skills, that sounds like a recipe for disaster.  I was
thinking instead of cutting the heads off of some appropriately
sized AN
bolts, flooding the bolt holes with JBWeld, and then inserting the
bolts
head-side first.  Since the pan only calls for ~ 8fp of torqued, I
figure this is a simple and reliable way to get studs for the
stripped
holes that I can then put metal stop-nuts on to secure the pan.

Comments?

Mark (Rocky Mtn High)

You must of read my mind. I was just thinking about your engine.

No no don't do that. Get some helicoils and a special tap.
I am sure you can do it if you use the proper drill.
Use google to check for the drill sizes.
McMaster also gives the drill sizes on the web site.

http://www.emhart.com/products/helicoil.asp
http://www.roadstarmagazine.com/modules.php?
name=News&file=article&sid=233

In Mcmaster Carr speak they are called "Helical Inserts".
Available in both metric and English sizes. Come in a kit with the
drill
and special tap. I think those pan bolts are 6 mm.

Also "Thread Inserts" that require a some what larger installation
holes.

Other than the oil leak how is the p-port engine running.

Paul Lamar ...No rotor no motor.

I have also found several stripped threads in the same location. If
the holes are already stripped, then helicoils are the answer.
Small  threads in aluminum are easy to strip.  I think it would be a
good idea to run a clean out tap whenever reinserting these bolts and
use a torque wrench.    Jerry


I was doing research on this on some machinists sites & came across the
suggestion to braze the stripped hole using a certina product.  Here's a
snippet from their website:



Thread Repair - Helicoil Thread Repair Alternative

Thread repair is easy with the HTS-2000 second-generation
brazing rod. If you're looking for a Helicoil thread repair
alternative you've come to the right place. With our
industrial-strength brazing rod, simply fill a hole with the
brazing rod material and drop a hot steel bolt into it. When
cool, the steel bolt can be backed out and new threads are
produced.

You probably know that sickening feeling already. You've
tightened a bolt almost as tight as it can go and you give
it that one last twist "just for good measure" and then you
feel the wrench spinning freely and loosely. You've stripped
the threads. With our HTS-2000 brazing rod, you can complete
your thread repair in minutes.

The HTS-2000 is permanent, erosion resistant and can be done
with any torch. Three times stronger and more flexible than
the first generation rods, the thread repair made with our
product is stronger than the original material.

Simpler to use than Helicoil, our HTS-2000 brazing rod can
repair threads for many automotive, aerospace, military and
industrial applications. Unlike Helicoil, there are no
inserts, taps, gages and tang break-off tools to mess with.
As with Helicoil, though, you will most likely need an
oversized drill bit to drill out the hole, first.

Instead of placing inserts into the hole, use a torch and
drop some off our high-tech brazing rod material right into
the hole. Heat the steel bolt to 750-degrees or above and
drop the bolt into the hole. Let the metal cool for 15 - 30
minutes and then using a wrench, back out the steel bolt
from the hole. Your thread repair is complete. You've just
repaired a thread faster, more efficiently and stronger than
a Helicoil thread repair.

The HTS-2000 second-generation brazing rod requires no flux,
is stronger than the base metal and melts at 500-degrees
below that of aluminum. No welding machine is needed as any
torch such as propane, butane, mapp, or an oxy-acetylene
will do. For expert thread repair, you don't have to be
expert to use our high-end brazing rod.

See the video for more details.


The video is quite impressive.  Anyone have thoughts on this before I go
out tomorrow & buy some inserts?

Mark Rocky Mtn High



Hi Mark,

Sounds like you have had more than your share of challenges with that
engine. To save you some future frustration of finding oil leaks and pulling
your engine once again I would advise to forget the brazing rod idea.  It is
a bandaid solution and one I would only use if I was stranded in some remote
place and needed to get home.  Consider replacing all  questionable threads
with an insert like Bill or Rob suggested. Just my two cents..

Regards


Doug Fir
hi  Mark            heating an al casting as expensive as that one for my airplane sounds a little risky to me.  you still wind up with a light alloy thread that can do it again.  the steel insert is a permanant repair that will still be there .  it is still the easiest and fastest and strongest,  an old A&P   wyo. walt.


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