From: svoboda@rtsg.mot.com (David Svoboda)
Subject: Re: First Trainer Questions
Organization: Motorola Inc., Cellular Infrastructure Group
Date: Tue, 29 Dec 1992 22:54:28 GMT

In article <1992Dec21.081522.2551@inland.com> bloom@inland.com writes:
|In article <1992Dec20.170241.973@bnr.ca>, martyg@bnr.ca (Martin Gallant) writes:
|> 
|> I have narrowed down the engine selection to the OS.40FP (~$70) and the
|> OS.46SF (~$140), the latter strongly recommended by my local hobby shop.
|> Do I need to be messing around with ball-bearing engines for my first
|> plane, or is a plain bushing motor adequate?  I am prepared to spend
|> whatever time is required for break-in on a test bench.
|
|There are plenty of other engines on the market that cost less than the 
|OS .46 SF and perform just as well.  I like the Enya .45 CXTV or the 
|Supertigre .45 ABC; both are about $20-30 cheaper than the OS .46 SF-
|ABN.  

I would agree with this.  There are many good engines on the market.  Watch
out for the Taiwanese brands, though.

|A bushing motor like the OS .40 FP has much less power (about the 
|same power as strong .25" motor) than an equivalent ball bearing motor. 

I would strongly disagree with this.  The only difference between a ball-
bearing motor and a sleeve bearing motor is the bearings.  Ball bearings
do not have significantly less drag, they just last longer and can take
greater stress.  But the FP is a Schnuerle ported engine, and produces
as much power as any other 40, excepting that you cannot safely stress
them with high nitro or tuned pipe.


|Your trainer may not need more power than the FP provides, but you can 
|always throttle a strong engine back.  If you're short on power, you 
|can't do anything but buy another engine.  Strong engines are an added 
|safety margin on take-off.  You can make steeper climbs without stalling 
|the plane.  Weak engines are much more critical on needle valve settings. 
|If the power is marginal, any change in the needle setting may reduce 
|the power enough to cause a stall and crash.   

The 40FP is the single most common motor used in 40-sized trainers, and 
most of the newer trainers were designed with that engine in mind.  Older
trainers (like the Goldberg Cardinal or Sig Kadet) were designed for
40's of fifteen years ago.  The 40FP is MUCH more powerful than those.
(My reference: the old K&B 40, considered a high-powered workhorse in it's
day, turns a 10x6 prop at about 11,000 rpm.  An FP turns the same prop at 
12K or more.)

You will have NO trouble getting off the ground with the FP.  Don't spend
the extra money.  You will likely feed the motor some grass and dirt the 
first time you muff a landing, and it is a shame to do that to a really
nice engine.

|Also, there is no more 
|messing around with ball-bearing motors than there is with bushing 
|motors.  All you do is run them dry at the end of the day, and give 
|them a dose of Marvel Mystery Oil.  

Which two things you do NOT have to do for a sleeve-bearing engine.

|As for break-in, with a good 
|strong .45 ABC ball-bearing engine, all you do is put it in the plane 
|and fly it - running in a rich 2-cycle.

Same with the 40FP.  One run on the picnic table (off the ground) until
it idles reliably, then break it in in the air.  Follow your instructor's
advice.

			Dave Svoboda, Palatine, IL