lml@lancaironline.net Mailing List Archive

Colyn, here's some more explanation as you requested. Doug Edwards runs Mid-Continent's gyro shop. As you can read below, he indicates that

1. My original gyro probably did *not* go bad from caging knob position (but caging knob position caused bad indications in the replacement gyros)

2. It's bad for a gyro to sit still for long periods (months), and

3. when the knob's pulled out, the first thing contacted is the caging ring which levels the roll and that constraining the roll bearings will actually feed into a pitch indication, which is what we saw that totally mystified us.

So the advice is: install the gyro soon after it's delivered, and make sure the caging knob can relax fully.

Begin forwarded message:

From: Doug Edwards <douge@MCICO.com>

Date: May 7, 2013 10:40:04 AM CDT

To: "'browncc1@verizon.net'" <browncc1@verizon.net>

Subject: RE: [LML] Re: Subtle bug in backup gyro installation

Good morning Charley,

It is difficult to pinpoint why the outer Gimbal bearings had a short life.

I do not believe it was related to the knob placement on the caging shaft,

A contributing factor may have been the shelf life from our original sale date

to Lancair being 5/3/2010 and the 9/2011 install date. All gyro’s have a 6 month

shelf life due to the oil in the Gimbal bearing will settle to the bottom of the bearing

and the oil may even escape from it intended area causing premature bearing wear.

As you have already discovered, the caging shaft set screw groove has approximately .110 (+/-)

adjustment (Groove is actually .207 but the knob bottoming out limits to approx. .110 of knob location/adjustment)

The Caging Pin assy. comes in initial contact with the Caging Ring at .170 (+/-) of shaft pull, therefore holding the “Roll”

In the level position. With a total of .280 (+/-) shaft pull, the Caging Pin contacts the Pitch cam, which is where it comes into play

if the Pitch bar climbs or descends due to the amount of pressure on the Pitch cam and the specific amount of pressure is a result of

knob location when panel/lighting ring interfere with the knob.

As I had mentioned during your visit, the Outer Gimbal bearings (Roll Gimbal) affect the Pitch alignment and

Inner Gimbal bearings (Pitch Gimbal) affect the Roll alignment due to torque and inertia created by the

Rotor spinning @ 20,000 RPM.

Please let me know if you have any questions.

Best Regards,

Doug Edwards
Mid-Continent Instruments and Avionics

(800) 821-1212 ph

www.mcico.com

From: Charles Brown [mailto:browncc1@verizon.net]
Sent: Monday, May 06, 2013 9:09 PM
To: Doug Edwards
Subject: Fwd: [LML] Re: Subtle bug in backup gyro installation

Doug, did y'all figure out

1. Whether the partially extended cage knob may have hastened my gyro's demise? and

2. Why it causes gyros to "climb" if extended a little further?

(I already figured out one thing -- the original installation of the gyro probably had the knob clamped on the post as far out as possible; whereas the loaner, and my refurbished gyro, both had knobs put on by you guys that were clamped closer to the instrument, preventing retraction as far as was possible in the original)