Webra SS rear bearing

Mon May 3 02:42:34 AKDT 2004

Hi guys,

Sorry for the slow response, things have been quite hectic around 
here lately (re: my eMail about moving to KSC).

I have only had one bearing problem and it was similar to what Keith 
described below with respect to the rear bearing getting loose 
radially.  In my case the bearing in my 145 didn't fail outright but 
some aluminum from the case just in front of the rear bearing rubbed 
off and went through the motor and wiped out the piston/sleeve.  It 
was deceiving in that the bearing didn't feel rough or anything but 
it did start to develop some slop radially which allowed the 
crankshaft to contact the case (it's a pretty tight tolerance in that 
location).  I asked my friend Stefan Fink in Germany about it and he 
said that it happened to him once too and that he had simply gone too 
long between bearing changes.  He said that he changes the rear 
bearing out once in the middle of the season and then again at the 
end of the season (about every 300 flights by his account).  He said 
that the one that "got loose" on him had well over 400 flights on it. 
Stefan is a 5 time German F3A National Champion, and while he's 
recently retired from competition, he does all of the factory testing 
for Webra.  My point is that he know's the motors inside and out, 
having tested them extensively for some time before we ever see or 
hear about them (case in point Stefan was running a prototype Webra 
160 AAR with MC carb at the 1999 World Championships in Pensacola, 
FL, 3+ years before it was released to the public last year).

As for me, I'm pretty hard on my motors as I'm generally only able to 
fly on weekends, and then usually only three or four flights per 
session.  I do run the motor dry most of the time, but I don't use 
any after run oil (never have).  Living in the Mojave Desert may be a 
factor (~12% humidity in the summer, 30-50% in the winter) but things 
do rust around here, given enough time.  Also, I run the 160 pretty 
hard, using Magnum #1 since the first flights on it last Memorial Day 
weekend.  I just started running Magnum 15% last weekend for no other 
reason but to see how much difference in performance there was (the 
answer is slightly less, but still way more power than just about 
anything else around - Tony Frackowiak's ePartner the one exception. 
Tony and I both agreed at the field today that with #1 I've got just 
a bit more Mo than he does, and with 15% I've got just a smidge 
less).  I have had no bearing problems with the 160, however I did 
change the original rear bearing last fall as preventative 
maintenance (the bearing was nearly perfect with just a slight 
discoloration on the back edge of the outer race).  I will probably 
change the bearings again before the Nats just to be safe, especially 
since it's so easy to do and the bearings are so cheap.

My experience with the OS140 wasn't as good, although it wasn't as 
bad as some stories I've heard either (hey to Verne!).  Frackowiak 
flew the OS61's extensively back in the "good old days" (hey to 
RVP!), and his recollection is that the OS's have pretty much always 
had bearing issues (he thinks it's some sort of metallurgy problem 
with the aluminum alloy they use in their motors).  I ran OS and 
Webra 61's throughout the 80's and they all had bearing problems of 
one kind or another.  The solution on the Webra's was to use the 
MRC/TRW-1903SFF sealed steel bearing with stainless steel retainer as 
the tabs on the stock brass retainer tended to come off and wipe out 
the sleeve (remember those days Dave Harmon?).

Anyway, there's my response.

Thx, Jerry

>I also would like to read Jerry's response.  The Bully/Webras are good
>engines but the bearings are the weakest link in my opinion.  A few years
>ago the 145 was my competition engine and the 120 before that.  I have owned
>3 and ran them all to the point of exhaustion. I've tried the factory
>bearings and other brands from Purvis bearing company (they have many
>different brands in stock) and never got more than 50 flights on a steel
>liner.  The newer AAC liner is better (the steel liners would rust and foul
>the bearings).  I don't have good numbers on the AAC sleeved engines because
>I moved to the OS140 then the Mintor 170 and have more than one reason to
>stay converted.  On bearings, I have over 150 flights on the factory Mintor
>bearings and they are still going strong.
>
>--Lance
>
>----- Original Message -----
>From: "Keith Black" <tkeithb at comcast.net>
>To: <discussion at nsrca.org>
>Sent: Tuesday, April 27, 2004 11:34 AM
>Subject: Re: Webra SS rear bearing
>
>
>>  OK Jerry, with a comment like that you're going to get a follow-up
>question
>>  from someone! ;-)
>>
>>  What exactly do you consider "reasonable care"? I've been flying
>>  Webras/Bullys (1.45) for the last year and have about 180 flights split
>>  between three different engines (most on the primary engine) and I have
>yet
>>  to get more than about 50-60 flights before needing to change bearings,
>>  sometimes as few as 30. In fact on one brand new engine the bearings
>>  disentigrated and shrapneled the engine after about 30 flights, and I used
>>  after-run oil on every flight and ran it fairly rich (thanks to Horizon
>for
>>  replacing the engine).
>>
>>  I've tried using after-run oil, not using after-run oil, I always running
>it
>>  dry, and as far as I can tell there's not much difference.
>>
>>  I've noticed is that sometimes they start running poorly due to the
>bearings
>>  becoming loose, in other words if you grab the prop tips and wiggle it
>front
>>  to back there will be movement. When this gets too bad the engine won't
>run
>>  as reliably (won't hold a low idle, mid to high transision gets bad,
>etc.).
>>  In this case when I examine the bearings there may be some rust on the
>>  outside bearing case, but mainly it's just discolored due to running.
>>
>>  Don't get me wrong, I've been an advocate of the Webra/Bully engines. Once
>>  broken in and the bearings are in good shape they run great (especially
>for
>>  the price). I just can't seem to get the bearings to last.
>>
>>  Thanks,
>>  Keith Black
>>
>>  ----- Original Message -----
>>  From: "Jerry Budd" <jbudd at QNET.COM>
>>  To: <discussion at nsrca.org>
>>  Sent: Tuesday, April 27, 2004 10:25 AM
>>  Subject: RE: Webra SS rear bearing
>>
>>
>>  > I looked all over for a SS rear bearing for the Webra 145/160 and
>>  > have come to the conclusion that nobody makes one in that size.  The
>>  > good news is that given reasonable care the Webra bearings tend to
>>  > last quite a while (much longer than the OS).
>>  >
>>  > Thx, Jerry
>>  >
>
>=====================================
># To be removed from this list, go to http://www.nsrca.org/discussionA.htm
>and follow the instructions.

-- 
___________
Jerry Budd
mailto:jbudd at qnet.com
=====================================
# To be removed from this list, go to http://www.nsrca.org/discussionA.htm
and follow the instructions.