Crankshaft balance

Here is some more discussion about balancing:
http://groups.google.com/group/rec.a...9345c98a2408b1

here are some links to the Lyc mess. I am amazed you are in the
industry and have not heard of this fiasco..

www.bizjournals.com/wichita/ stories/2005/02/14/daily30.html

Another link to bad cranks....

eaa563.org/Newsletters/ 2002%20News%20Letters/0203/vol9issue3.pdf

more bad "CERTIFIED cranks

www.machinedesign.com/ASP/viewSelectedArticle.
asp?strArticleId=58969&strSite=MDSite&catId=0 -

Better yet just google " Lycoming crankshaft recall" Your sig line
shows you are a FAA repair station.. Ya mean the feds didn't notify you
of this major failure???



Kent Felkins
Felkins Aircraft Ltd.
FAA CRS WNKR918K
Tulsa Oklahoma

Ben,

I got a word from the machine shop. They say they can balance the crank
- about 5 g off on one end and about 8 g on other end. But they are
worried about the pistons and rods. Pistons about 5 g off and some rods
about 5 + 3 off. They will try to do the best but cannot take that much
alum off the pistons.

"abripl" wrote in message
oups.com...
Ben,

I got a word from the machine shop. They say they can balance the crank
- about 5 g off on one end and about 8 g on other end. But they are
worried about the pistons and rods. Pistons about 5 g off and some rods
about 5 + 3 off. They will try to do the best but cannot take that much
alum off the pistons.

It sounds like you are about to make some hard, expensive choices. New
pistons and rods, or live with at least part of it, is what it sounds like,
to me.

That is a lot of difference, don't you think?
--
Jim in NC

... make some hard, expensive choices.... or live with .. part....

They will get it as close as they can. The engine was about .4 ips
imbalanced to start with - not so terrible, FAA certified limit is 0.2
ips. Any improvement will certainly help and may bring it within the
0.2 ips. Remember that this engine redlines at 2800rpm compared to an
auto engine at about 6000rpm. The same mass imbalance forces are one
quarter that of an auto engine.

There are some tricks that can be done:
A.) for heavy rods big end - cut off four of the six castle nut crowns
to save almost 2 g or use a longer heavier nut with a slot where the
cotter pin goes to add 2 g to light big ends = a difference of 4 g.
B.) We will also look at matching light pistons with heavy small ends
and heavy pistons with light small end.

My engine is listed as EXPR-OTHER and not as not as a certified
Franklin - required 40 hours test time. This allows using a little
ingenuity to solve such problems.

OK. They managed to get things in balance - within one gram.
The only thing was the starter gear with the torsional damper. Because
of the fluid damper it changes - about 5g out max. Does anybody know if
5g is acceptable for a 10" flywheel?

OK. They managed to get things in balance - within one gram.
The only thing was the starter gear with the torsional damper. Because
of the fluid damper it changes - about 5g out max. Does anybody know if

5g is acceptable for a 10" flywheel?



////////////////////////////////////////////

One gram is darn close for your application. You will notice a
difference when ya fire up the new beast. As for the damper, if it is a
fluid style i can tell you they never repeat while spinning up on a
balancer machine. Temp differences cause the viscious fluid to migrate
differently every time so don't sweat the small numbers there. I am
curiuos, Was this engine a first time run motor and never been into
before? You would think with all the FAA requirments they would dictate
part weights in a new "certified" motor to be closer then 5-8 grams.
I also want to say Jim was very good at reading into the fine print and
giving a great feel of what was trying to be said. I am a little
forward in expressing my views and do sometimes rub people the wrong
way and hope we can get over this feud.

Happy Hollidays all you guys.

Ben