OS mixture question
Robert Harden
rharden1 at cox.net
Wed Sep 21 16:50:44 AKDT 2005
I was thinking of getting a Showtime 90 also. There are a few around
Wichita, KS and the pilots are having a good time with them. Let us know
how you set yours up.
Thanks,
Bob
----- Original Message -----
From: "Bob Pastorello" <rcaerobob at cox.net>
To: "Robert Harden" <rharden1 at cox.net>
Sent: Sunday, September 18, 2005 7:50 PM
Subject: Re: RE: OS mixture question
> You're welcome! Best of luck with your setup!
>
> I have just finished a SHowtime90 and powered with a Saito 1.50... gonna
> make that motor work in pattern.... will be fun.
>
> Bob Pastorello
> www.rcaerobats.net
> rcaerobob at cox.net
> ----- Original Message -----
> From: "Robert Harden" <rharden1 at cox.net>
> To: <discussion at nsrca.org>
> Sent: Sunday, September 18, 2005 7:45 PM
> Subject: Re: RE: OS mixture question
>
>
>> Bob,
>>
>> I saved the below messages some time ago and am now getting around to
>> reading it again. I am at the header and pipe installation right now and
>> find your write-up below useful. Thanks for sharing it with us.
>>
>> Bob Harden
>>
>> ----- Original Message -----
>> From: <rcaerobob at cox.net>
>> To: <discussion at nsrca.org>
>> Sent: Tuesday, April 19, 2005 10:27 AM
>> Subject: Re: RE: OS mixture question
>>
>>
>>> This is good info, no doubt!!!
>>> Just a thought - many folks want a "starting point" for pipe length.
>>> Experimenting with different props/pipes and motors - all things being
>>> about equal (I know they're not, really, but it's okay), I've found the
>>> 17 x 12 APC or similar load starting point to be about 23.75 -24" plug
>>> to reflector, following headers curves, and the "wave" length.
>>>
>>> This measurement will get a person who's in a hurry in a flyable
>>> condition pretty fast, with minimal additional tweaking.
>>>
>>> Of course, YMMV, depending on a lot of things, but the most frequently
>>> asked question I get by the newbie two-stroke convert (or a former 2
>>> stroker who has RE-converted)is "what's a good starting point for 1.40 -
>>> 1.70's in today's planes?"
>>>
>>> Hope this is helpful to someone.
>>>
>>> Bob P.
>>>>
>>>> From: "richard.lewis" <richard.lewis at idmcontrols.com>
>>>> Date: 2005/04/19 Tue AM 11:08:47 EDT
>>>> To: <discussion at nsrca.org>
>>>> Subject: RE: OS mixture question
>>>>
>>>> Thanks again Wayne...:) Very well spoken, clear, and concise 2-stroke
>>>> tuning methodology.
>>>>
>>>> Richard
>>>>
>>>> _____
>>>>
>>>> From: discussion-request at nsrca.org
>>>> [mailto:discussion-request at nsrca.org] On
>>>> Behalf Of Wayne Galligan
>>>> Sent: Tuesday, April 19, 2005 9:12 AM
>>>> To: discussion at nsrca.org
>>>> Subject: Re: OS mixture question
>>>>
>>>>
>>>> I helped a guy with the a similar issue this weekend on his Mintor. Way
>>>> too lean on the bottom end. His would pop on acceleration or die coming
>>>> out
>>>> of the outside loop.
>>>>
>>>> For the OS 1.40 RX Try this:
>>>> Use an OS "F" plug.
>>>> 15% nitro
>>>> I have not had to adjust the pump on any of the OS's I have set up to
>>>> date.
>>>>
>>>> Set the top end till it peaks in rpm(use a tach if you have one) and
>>>> back
>>>> off one click to the rich side.
>>>> Bring it down to an idle and try to set the idle to about 18-1900 rpm.
>>>>
>>>> Let the engine idle for at least 20-30 seconds and do not touch the
>>>> throttle.
>>>> 1. if it speeds up or surges at any time during this time the
>>>> bottom end
>>>> is lean.
>>>> 2. if the engine gradually slows down and dies...its rich.
>>>>
>>>> Advance the throttle with medium speed and observe:
>>>> 1. if it burbles and picks up speed or burbles and dies bottom end
>>>> is
>>>> too rich.
>>>> 2. if it falls flat or hesitates then accelerates or dies it is
>>>> lean
>>>>
>>>> This may take several tries to get but once its set then its just minor
>>>> top
>>>> end adjustments depending on weather conditions.
>>>>
>>>> Changing pipe lengths will also effect the low end transition. A
>>>> longer
>>>> pipe setting will allow you to set the bottom end a little richer and
>>>> give
>>>> better downline braking.
>>>> I find that running the bottom end as rich as possible with out it
>>>> loading
>>>> up gives the best downline deceleration.
>>>>
>>>> Setting your pipe is a whole other story. My best method is on a test
>>>> stand. Set the pipe long and run engine, tach the top end at peak
>>>> rpm.
>>>> Shorten the coupler or pipe about 1/4" at a time and observe the peak
>>>> rpm.
>>>> It will increase with each shortening of the pipe.
>>>> Once it peaks in rpm or no longer increases or drops in rpm this is the
>>>> top
>>>> tuning spot for your engine and pipe for max rpm(not really the desired
>>>> tuning).
>>>> At this point back the pipe off about 3/8 to 1/2". This will give you
>>>> a
>>>> good starting point. I usually lengthen the pipe if I go to a higher
>>>> loaded
>>>> prop or
>>>> shorten it with a lighter loaded prop.
>>>>
>>>> The OS 1.40 is a very predictable engine. If it starts to load up and
>>>> stall in the midrange for no apparent reason or drops rpms
>>>> after the glow plug is removed first check the plug . If it continues
>>>> to do
>>>> the same thing then the bearing is probably on its way out.
>>>> Replace the bearing with a sealed bearing or a stainless steel bearing
>>>> that
>>>> goes in the EFI version. I have about 200 flights on one
>>>> of my OS's that has the sealed std steel bearing from Bearings Limited
>>>> in it
>>>> and it is still going strong. Another way to check the bearing is
>>>> move the
>>>> prop by the tips
>>>> perpendicular to the engine and if you can feel end play the bearing is
>>>> getting loose.
>>>>
>>>> Wayne Galligan
>>>>
>>>> ----- Original Message -----
>>>> From: Kurt <mailto:kurt at bozarthhomes.com> Bozarth
>>>> To: discussion at nsrca.org
>>>> Sent: Monday, April 18, 2005 7:22 PM
>>>> Subject: OS mixture question
>>>>
>>>>
>>>>
>>>> OS 140 RX (non-EFI) question:
>>>>
>>>>
>>>>
>>>> When I advance the throttle, the rpms remain at idle for approx. one
>>>> second,
>>>> "pop" and then advance to full throttle rpms I am not quite sure if
>>>> this
>>>> "pop" and hesitation is a result of having too lean of an idle mixture
>>>> or
>>>> too rich. This is an older motor released back when Hobby Services
>>>> offered
>>>> a free needle valve assembly replacement to correct for mid-range
>>>> richness
>>>> issues. I do not know if this was done or not - something I will check
>>>> for
>>>> tonight. I have never adjusted the pump setting. Let me know your
>>>> thoughts. Thank you.
>>>>
>>>>
>>>>
>>>> Kurt Bozarth
>>>>
>>>>
>>>>
>>>
>>> Bob Pastorello, El Reno, OK, USA
>>> rcaerobob at cox.net
>>> www.rcaerobats.net
>>>
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>>
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