Tom Kendall wrote:

I've got my 20B all in little pieces, bagged, tagged, and in boxes now.

The

engine is almost pristine.  Other than a lot of soft carbon, it looks

almost

brand new.  There is very little (if any) measurable wear anywhere.

Even

the apex seals look new, and there is no measurable step wear or
scratching/grooving of the rotor housings.

But... When I got to calculating the oil clearances on the main bearings
(rotors are fine), I found them all too large.  Double checked

measurements

& calculations, and still too big a gap.  This really has me stumped.

The

journals haven't even taken a polish, and the babbit is still hazy (also
hasn't polished in).  I can't figure how the clearance could be so large

on

an essentially new engine.

Here's what I have:

                                Main Bearing Clearance
Front Rotor                        0.0038"
Center Rotor                    0.0033"
Rear Rotor                        0.0036"

Each of these is above the spec range of 0.0016" - 0.0031"

The rotor bearings are right in there with 0.0022" - 0.0024".

Does this make sense to anybody?  Did Mazda provide increased oil

clearance

on these 3 rotor engines?  I would really hate to press out the babbit

on

good bearings... I'll probably screw it up if I do.

Any suggestions welcome.

Bruce Turrentine just responded to an e-mail I sent him with this question.
Turns out the 20B e-shaft (and/or bearings) are made with larger clearances
to accomodate the greater flexing of the longer shaft.  Spec clearances for
the 20B main bearings are 0.00425" max.  Sure explains why such a low wear
engine had such large clearances.

Tom Kendall

The AirCraft Rotary Engine NewsLetter.              Powered by Linux.
ACRE NL web site. Copyright 1998-2002 All world wide rights reserved.
http://home.earthlink.net/~rotaryeng/            http://www.linux.org