Swallow & Also Servos

[ronlock]

I  found the servo test data very interesting.
In the discussion of test method, there is no mention of  an
attempt to duplicate vibration, as is present in our models.
The difference between bushing  and ball bearing servo
life and performance might be different in the presence
of vibration.

Ron Lockhart
----- Original Message ----- 
From: "Wade Akle" <wbakle at charter.net>
To: <discussion at nsrca.org>
Sent: Friday, June 27, 2003 7:09 PM
Subject: Re: Swallow & Also Servos


> Eric,,
> According to the Aussie UAV tests, ball-bearings were not a factor, and
> linkage 'slop' was more significant than cheap servo 'slop'. I may have
read
> too much in #8 and 12. Anyway, can anybody confirm and source/date this
very
> interesting data?
> Here is for what I copied from this group a month ago
> Wade
>
> From: "John Monk" <jsmonk at csir.co.za>
>  I did find the following article that I thought worth sharing with the
>  group. It come from Brian Taylor in Aus.
>
> In a recent job I got to test 50 servos from several manufacturers (Hitec,
> JR, Futaba, GWS, Volz, FMA) for a UAV manufacturer.
> Perhaps this summary will help.    I set up a 100 hour test with the
> servos cycling +/- 45 degrees once per two seconds lifting a 1 kg load on
a
> 10 mm moment arm.  In normal flight conditions there would be many small
> deflections rather than the continuous sweeping I used in this test.  The
1
> kg.cm
>  torques are fairly representative of flight loads on a small UAV or  RC
> model.
> All tests were done at 5.00 volts with each servo having its own 1 amp
>  power supply and a 1000 uF cap to supply a short time peak current a bit
> over an amp.  Note that digital servos can pull considerably more than one
> amp when stalled but running in this test they drew less than one amp.
> 1.  There is NO true standard in the hobby RC servo industry except that
> 1500 uSecs was the centre position on ALL servos tested.
>  2.  1000 to 2000 uSecs works with EVERY servo tested.  900 to 2100 or 800
> to 2200 worked with SOME analog servos but caused almost instantaneous
> destruction with newer digital servos.  Digital servos draw 4 or 5 times
> more current in their quest to get to the set point faster.  If the
internal
> gearboxes, or a binding linkage,  prevents this, they go into very rapid
> meltdown internally.
>  3.  Just because your new fancy transmitter lets you dial in 120% throws,
> do NOT assume your servos will comply.  Digital ones may die.
>  4.  Rotation angle is not standard, even within one maker's range.  1000
to
> 2000 uS can be +/- 45 degrees, +/- 60 degrees or even +/- 90 degrees.
> 5.  All nylon gearboxes typically have lowest backlash and remain tight
over
> 100+ hours of cycling.  Metal gearboxes wear substantially over 100 hours.
> 6.  Metal shaft/metal gear servos like the Futaba micro servo are very
> robust but the metal shaft conducts interference into the pot and the
servos
> chatter with nearby RF nterference - bad news on a UAV with  on-board
> transmitter until you fit ferrites & bypass caps.
> 7.  Hitec servos, in general,  have motors far too powerful for their
> gearboxes and instantly strip gears if linkages bind.  Other servos may do
> this but Hitec stood out as poor in this regard.  Volz failed in the
> shortest time under load tests from electronic failures, not gearbox
> troubles.
> 8.  Ball bearing servos performed no better than servos with the output
> shaft just rubbing on the plastic case.  Observed case wear on the no
> bearing Futaba and GWS servos was negligible.
> 9.  Driving the servos with 50 Hz refresh rate gave 100% of makers specs
for
> response time and torque.  Driving faster (only went to 60 Hz) did not
> improve response times.  Going down to 25 Hz refresh rate worked for all
> servos tested but holding torque and response rates suffered.
> 10.  Lowest power with highest speed was to drive the servos at 50 Hz rate
> until into position then drop the refresh rate back to 10 Hz.  Only works
> for lightly loaded servos however.
> 11.  Price was absolutely unrelated to lifetime.  The most expensive
(Volz)
> failed first (all three of a sample of 3 at 5, 22 and 35 hours).
> 12.  Cheaper servos have more backlash when new and tended to have highest
> backlash at end of test.  Backlash was very small in every servo tested
and
> your linkages are guaranteed to have more slop than the servos.
> 13.  Digital servos have a genuine 1000+ steps between 1000 and 2000
uSecs.
> Analog servos gave 500+ steps from cheapest to most expensive.
> 14.  How long do servos last??   Unless you physically stress them by
> manually moving the output arms, you can be almost certain to get 75
> continuous hours.  That is probably plenty for normal RC hobby flying but
> for UAV use I would suggest replacement at 50 hours maximum.  Your mileage
> will vary depending on loads, vibration (the wiper on the feedback pot can
> gouge a pit into the track in high vibration), power supply voltage and
> current limits, temperature extremes, moisture ingress, etc, etc. Lifetime
> could be as low as 10 hours if you insist in pulling the full rated torque
> and loads out of the servo with every movement.
>
>
>
> ----- Original Message ----- 
> From: "Henderson,Eric" <Eric.Henderson at gartner.com>
> To: <discussion at nsrca.org>
> Sent: Friday, June 27, 2003 7:42 AM
> Subject: RE: Swallow & Also Servos
>
>
> Ref. covering wrinkles. I found the Swallow needed a heat gunning before
it
> could be flown. The Quest handled the 90F with no problems.
>
> As regards servos I would use at least ball-bearing servos and also
clevices
> that have no slop in them. It is hard to fly straight and level if the
> ailerons are moving....
>
> E.
>
> -----Original Message-----
> From: discussion-request at nsrca.org
> [mailto:discussion-request at nsrca.org]On Behalf Of John Crozier
> Sent: Friday, June 27, 2003 11:04 AM
> To: discussion at nsrca.org
> Subject: Re: Swallow & Also Servos
>
>
> I must have missed the UAV report.
> Is it available somewhere?....croz
> ----- Original Message ----- 
> From: "Wade Akle" <wbakle at charter.net>
> To: "Paul Horan" <phoran at vvm.com>; <discussion at nsrca.org>
> Sent: Friday, June 27, 2003 7:02 AM
> Subject: Swallow & Also Servos
>
>
> > Paul,
> > I built the Swallow as a bare-bones demo for my flying buddies to show
> them
> > that you could fly pattern as sport. Therefore, stock Tower 75 muffler,
no
> > pipes or any pattern goodies. To my surprise, I am enjoying flying
> Advanced
> > with it and using it a lot more than my full size patterns. I guess its
> the
> > freedom of knowing that the investment is low, the size convenient, and
> the
> > setup easy.
> >
> > By the way, I also used standard servos after reading on this site the
> > results of the Australian UAV research on servo selections. I was amazed
> > that so few responses were made about the Aussie results. It's one thing
> to
> > have the money to buy the 'most expensive' it's another to ignore data.
We
> > are talking about standard resin gear servos centering and slop compared
> to
> > servos 10x the cost.
> >
> > Wade
> >
> > ----- Original Message ----- 
> > From: "Paul Horan" <phoran at vvm.com>
> > To: "Wade Akle" <wbakle at charter.net>
> > Sent: Thursday, June 26, 2003 9:03 PM
> > Subject: Re: Swallow
> >
> >
> > > Wade,
> > >     It appears that the Swallow has a single piece mid-wing.  The
> > pipe/silencer tunnel is on the bottom side of the wing; therefore,
> > > the pipe must be removed when ever the wing is removed.  Is this
correct
> > ?
> > > Thanks,
> > > Paul
> > > ----- Original Message ----- 
> > > From: "Wade Akle" <wbakle at charter.net>
> > > To: <discussion at nsrca.org>
> > > Sent: Wednesday, June 25, 2003 7:36 PM
> > > Subject: Re: Swallow
> > >
> > >
> > > > Eric,
> > > > I have a Swallow with Tower's .75 engine. Talk about inexpensive,
$330
> > for
> > > > them, but it proved to be a great choice and does Advanced well, for
> me.
> > The
> > > > engine purrs below 1700 and roars up to 10000 rpm, never missed. A
> > relief
> > > > from the YS and Webra's. Expensive pattern is by choice not
> requirement,
> > > > unless you compete at the national level. I have built and flown
many
> > full
> > > > pattern ships, that I enjoyed, but now I mix in easy, inexpensive
Fun.
> > > > I am very interested in a comparison of the Swallow with the Quest.
> > > > Wade
> > > >
> > > > ----- Original Message ----- 
> > > > From: "Henderson,Eric" <Eric.Henderson at gartner.com>
> > > > To: <discussion at nsrca.org>
> > > > Sent: Wednesday, June 25, 2003 5:19 PM
> > > > Subject: RE: Swallow
> > > >
> > > >
> > > > Good luck tomorrow Bill.
> > > >
> > > > I think the Swallow will like the power of the 1.30.
> > > >
> > > > I did my QUEST test flights today that I will post in a separate
note.
> > > >
> > > > Regards,
> > > >
> > > > Eric.
> > > >
> > > > -----Original Message-----
> > > > From: discussion-request at nsrca.org
> > > > [mailto:discussion-request at nsrca.org]On Behalf Of Bill Glaze
> > > > Sent: Wednesday, June 25, 2003 5:50 PM
> > > > To: NSRCA discussion
> > > > Subject: Swallow
> > > >
> > > >
> > > > Just got a look at Eric's review of the Swallow.  Could hardly have
> come
> > > > at a better time.  I'm testing mine tomorrow, weather permitting.
> > > > Powered by a Y.S. 1.20, (the old one) it weighs just under 8-1/4
lbs.
> > > > After reading what he says, I believe I'll reduce my control throw
on
> > > > the elevators, at least, and maybe ailerons also.
> > > > I'll post to the list--boy, do I absolutely hate first flights!
> > > >
> > > > Bill Glaze
> > > >
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> >
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