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Model Forum / Radio Controlled / Air Models / October 2007



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Flying the AMA Twin Sport Utility

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Ted - 20 Oct 2007 00:43 GMT
I have flown this bird about 8 times now and each flight is a little
different. There is a brief article in this month's MAN that detials a
simple way to synch the engines so that is how I am doing it now. Due
to the newness of the engines though, it requires a re-synch each time
I fly. I hope they break in soon. Anyway, I was flying yesterday and
the port engine quit. I hardly noticued it was out. The plane still
flew very well but would not turn into the dead engine side. I
rmemeneberd my engine out procedures and started flying to the right
keeping the speed up. Landed with no problems so it does well on one
engine. Since I am using twin Magnun 46's I have had to go up to a
12x4 prop to keep the speed down as it really scoots with anyhting
else. One word of caution if you build this. Take off at FULL
throttle. I tried half throttle the other day and the controls were
mush. Not enough airflow over the control surfaces to gain positive
control after rotating. Once up, I increased the speed and all was OK
(until I lost an engine). She is a speed demon but not built for 3-D.
Just enjoy the sunday afternoon flight.

Ted
daytripper - 20 Oct 2007 00:50 GMT
>I have flown this bird about 8 times now and each flight is a little
>different. There is a brief article in this month's MAN that detials a
[quoted text clipped - 15 lines]
>
>Ted

Synchronizing the engines on a model is much less important than tuning them
to run reliably...

/daytripper
Fubar of The HillPeople - 20 Oct 2007 03:09 GMT
Got any pics you can post?

>>I have flown this bird about 8 times now and each flight is a little
>>different. There is a brief article in this month's MAN that detials a
[quoted text clipped - 21 lines]
>
> /daytripper
Ted - 25 Oct 2007 18:59 GMT
On Oct 19, 7:09 pm, "Fubar of The HillPeople"
<fub...@trashsocal.rr.com> wrote:
> Got any pics you can post?
>
[quoted text clipped - 25 lines]
>
> - Show quoted text -

Unfortunately, you can't post pics using the Google news reader. I
will send some to your Yahoo email if you don't mind.
Ted - 25 Oct 2007 18:57 GMT
> >I have flown this bird about 8 times now and each flight is a little
> >different. There is a brief article in this month's MAN that detials a
[quoted text clipped - 22 lines]
>
> - Show quoted text -

I hate to disagree but if they are synched, they are tuned. Part of
the synch process is to tune the low end on each engine and then the
high end. The synch process comes in when you determine which engine
is the "stronger of the two at optimum RPM and then you richen that
slightly "weaker" engine to bring it down to the lower rpm running
engine.
Ed Cregger - 20 Oct 2007 07:07 GMT
>I have flown this bird about 8 times now and each flight is
>a little
[quoted text clipped - 31 lines]
>
> Ted

A few hundred rpm difference between the engines is of
absolutely no consequence. Let that one get out of your
head.

There were electronic devices that had a sensor on the
slowest engine and that signal went to a box that slowed the
second engine (which also required a sensor) down to match
the slower engine. Both engines were originally tuned
independently for max reliability. This is the ONLY way I
can see to do it reliably without getting into a lot of
mechanical work on the engines - and all for nothing.

Yes, Charlie (CR), I know you're watching my absolute
proclamations. This time, before criticizing me for making
such a proclamation (which is only done to stir dialogue),
come up with an answer to the synchronizing problem FIRST.
<G>

Ed Cregger
Ted - 25 Oct 2007 19:02 GMT
> >I have flown this bird about 8 times now and each flight is
> >a little
[quoted text clipped - 53 lines]
>
> - Show quoted text -

Well Ed, glad you told CR off. He's been a pain in the butt ever since
he fouled up the Kerrville TX RC club. But, be that as it may, my
EXPERIENCE with twins has taught me to get the high end RPM match as
close as possible. Its a personal preferenece and not a hard and fast
rule.
Ed Forsythe - 24 Oct 2007 19:31 GMT
Use an accurate tach. TNT is the best, IMHO.
>I have flown this bird about 8 times now and each flight is a little
> different. There is a brief article in this month's MAN that detials a
[quoted text clipped - 15 lines]
>
> Ted
Ted - 25 Oct 2007 19:02 GMT
On Oct 24, 11:31 am, "Ed Forsythe" <EdNoSpamForsy...@hotmail.com>
wrote:

> >I have flown this bird about 8 times now and each flight is a little
> > different. There is a brief article in this month's MAN that detials a
[quoted text clipped - 17 lines]
>
> - Show quoted text -

Agree!
Doug McLaren - 29 Oct 2007 20:40 GMT
| Use an accurate tach. TNT is the best, IMHO.

Aren't all the modern optical, electronic tachs of similar accuracy --
i.e. they're all almost perfect?  And if your flourescent light isn't
rotating at 3600 rpm, either you're not in the US, or something is
wrong. :)

What the better ones give you is better sensitivity -- you don't have
to be so close to the prop, lighter weight, less likely to break if
dropped, etc.

Signature

Doug McLaren, dougmc@frenzied.us
I didn't claw may way to the top of the food chain to eat vegetables!

 
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