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Old Mar 13, 2006, 03:15 AM
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Crieff, Perthshire, Scotland
Joined Jun 2005
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Sorry to break the trhead for a moment chaps, but I really must ask.

How do you 'time' a brushed motor and what are the benefits of this mod? I think I should start breaking in my motors also.....is it ok to run them on 1/4 throttle for 10-15 mons instead of using a cup of water?

Cheers in advance.
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Old Mar 13, 2006, 03:19 AM
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Crieff, Perthshire, Scotland
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Fantastic discussion by the way!
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Old Mar 13, 2006, 03:38 AM
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Lisboa, Portugal
Joined Jan 2004
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Quote:
Originally Posted by kaiser_solsay
Sorry to break the trhead for a moment chaps, but I really must ask.

How do you 'time' a brushed motor and what are the benefits of this mod? I think I should start breaking in my motors also.....is it ok to run them on 1/4 throttle for 10-15 mons instead of using a cup of water?

Cheers in advance.
Timing for the Permax 400 does not make a big change. Basically you release the back of the motor and rotate it little by little until you get the highest current draw. In some cases you get a little more power, but in this case not enough to justify the risk of damaging the motors...

As for breaking in, I break them in in water with two NiCd or NiMH AA cells, but in the past I ran the motors for 2 or 3 5 minute periods at less than 1/4 throttle. Don't run them for more than 5 minutes at a time and let them cool before running them again.
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Old Mar 13, 2006, 03:47 AM
sensitive artsy type
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Tucker, Georgia, United States
Joined Feb 2004
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Quote:
Here we go again like in the EasyStar threads. The TS2 needs, just like the EasyStar, a full range TX/RX system. The Spektrum DX is strictly for park flyer range.
- jcosta
Young man, did I say I was going to use it in the TS2? You're assuming!

Besides, according to what I have read on here, it was tested to 1000 feet (over 300 meters) by the reviewer for Ezone:

http://www.rcgroups.com/forums/showthread.php?t=444902
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Old Mar 13, 2006, 03:48 AM
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Crieff, Perthshire, Scotland
Joined Jun 2005
226 Posts
Thanks Jcosta, most appreciated.

I was planning on installing a couple of Typhoon 6/15 brushless into my TSII, but I might just go for a couple of 480 7.2v's instead now after reading the previous posts. If I can get a ok efficiency from the brushed 480's....why bother with the brushless expenses? I know there is a considerable weight saving gain, however if the plane flies perfectly fine using 480's then thats all I'm really looking for.

I picked up an 'UIltrafly' Extra at the weekend...my first low wing foamy!! (Should I be scared!) It has the standard geared 400 motor installed and I am waiting for some servo's to arrive before its first maiden. Have any of you guys owned this plane? If so, what she like to fly?
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Old Mar 13, 2006, 03:51 AM
more time to fly !!!
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Asti, Italy
Joined Apr 2004
340 Posts
What ???
A Spektrum 6 on a Twinstar ???
A brushless one ???

You really want to loose your plane? That's not a park-flyer...

Piero
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Old Mar 13, 2006, 04:00 AM
SlopeHead
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Lisboa, Portugal
Joined Jan 2004
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Quote:
Originally Posted by Treetop
Young man, did I say I was going to use it in the TS2? You're assuming!

Besides, according to what I have read on here, it was tested to 1000 feet (over 300 meters) by the reviewer for Ezone:

http://www.rcgroups.com/forums/showthread.php?t=444902
You didn't, somebody else did. And I read otherwise in reviews without commercial interest.
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Old Mar 13, 2006, 05:18 AM
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United Kingdom, Bracknell
Joined Nov 2000
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Quote:
Originally Posted by jcosta
I've even flown recently a TS2 that CAN hover.
My turn to be pedantic

With enough thrust it could climb vertically, or prop-hang for a second or two, but not sustain a hover. You need large control surfaces directly in the prop-wash for that.

In Paint Shop Pro however, anything is possible
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Old Mar 13, 2006, 06:13 AM
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Treetop's Avatar
Tucker, Georgia, United States
Joined Feb 2004
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Here is an interesting Hobbico Twinstar converted to electric in Ezone:

http://www.rcgroups.com/links/index.php?id=4719
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Old Mar 13, 2006, 06:25 AM
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Lisboa, Portugal
Joined Jan 2004
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Quote:
Originally Posted by Bill Glover
My turn to be pedantic

With enough thrust it could climb vertically, or prop-hang for a second or two, but not sustain a hover. You need large control surfaces directly in the prop-wash for that.

In Paint Shop Pro however, anything is possible
OK, Bill, it can prop-hang
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Old Mar 13, 2006, 11:34 AM
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Joined May 2004
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Quote:
Originally Posted by Bad Attitude
What ???
A Spektrum 6 on a Twinstar ???
A brushless one ???
Yes, Piero, absolutely.
Quote:
Originally Posted by Bad Attitude
You really want to loose your plane?
No, I want very much to *not* lose my plane. The field I fly at is a public park, with no enforced RC frequency control, and high levels of RF interference. I have been shot down three times by newbies turning on without checking if anyone was on their channel - I was.

To get to the technical side of this issue - is the DX-6 okay for a Twinstar? The wording "parkflyers only" was so vague that it raised more questions than it answered for me. Were they talking about range limitations? If so, what was the actual limit?

So I attended one of the seminars given by John Adams, Spektrum's chief engineer, at the last AMA show in Ontario, California. During and after his talk, he responded to numerous questions, so I had the chance to discuss the DX6 system with the man in charge himself.

Here is what Mr. Adams told us/me. The Spektrum has an officially blessed range of 1500 feet (unofficial tests have shown twice that in some cases), more than adequate for quite large model aircraft. However, the short wavelength of 2.4 GHz RF (12.5 cm or about 5 inches) raises the possibility of RF shielding by large metallic objects - a metallic object (such as a large glow engine in a 1/3 scale model) can cast an RF "shadow" which could prevent the receiver from receiving the transmitters signal when the aircraft happens to be pointed in certain directions.

For those without a physics background, when an obstacle is much smaller than the wavelength of radiation, it casts no real shadow - our 72 MHz RC frequencies have a wavelength of 4.17 metres, much bigger than the metal objects to be found in any RC model aircraft, so 72 MHz receivers are not going to be shadowed in the same way as the Spektrum system.

The Spektrum's high frequency also makes it susceptible to RF absorption by any large amounts of conductive carbon fibre that might be in the model, also certain covering materials (some white iron-on film contains titanium dioxide which absorbs RF) can also be problematic.

So, and this is direct from the man who spent the last seven years in charge of developing the DX6, the "parkflyers only" restriction is intended to ensure that nobody tries to use a DX6 to fly a plane with a large metal engine, or with lots of carbon fibre, or with heavy-duty iron-on coverings that absorb RF. They (Spektrum marketing) thought it would confuse non-technical RC pilots if they mentioned the need to avoid large metal objects or conductive coverings, and they decided that "parkflyers" were unlikely to contain any of these problem materials, so they came up with "for parkflyers only".

As you can see, Elapor models powered by small electric motors are not in this category, and can be flown quite safely with the DX6. Elapor (a mix of polystyrene and polyethylene) is quite transparent to 2.4 GHz RF, and the electric motors and lipo pack are too small to cast any significant RF shadow.

For anyone unconvinced by science, perhaps a direct statement will suffice. I specifically asked Mr. Adams about large electric foamies such as the Multiplex Magister and Multiplex Twinstar. His response was that there should be absolutely no problem with these sorts of models, as long as they were kept within the rated 1500 ft. He added that he thought a 2-metre balsa built up sailplane would also be safe to fly to 1500 ft with the DX6, though he would not recommend using it on any carbon mouldie.

I bought my Spektrum DX6 the same day, immediately after attending Mr. Adam's seminar - his seminar convinced me of what I had already suspected, that this revolutionary new transmitter was the answer to my RF problems at the Rose Bowl, and that it would not limit me at all, as it covered all the models I currently own or have any real interest in.

I've been flying with my DX6 since mid January, and have experienced not a single glitch or issue in two months - just a seamless, rock-solid link to the model, so solid that it disappears from ones perceptions. With my 72 MHz stuff I was always attentive for glitches, even with dual-conversion and/or Berg 5 receivers, and in the back of my mind I was worried about getting shot down by yet another careless RC pilot. With my Spektrum, once I've done my range check and gotten the model airborne, the link to the model is so solid that I entirely stop thinking about it, and focus on flying the plane instead of worrying about the RF link.

I've conducted some quick-n-dirty experiments at the field I fly from with two other foamies with wingspans in the 50+ inch range, estimating the distance they were at by comparing the visual wingspan of the models in flight with the thickness of the tip of the Spektum's antenna, and using the simple mathematics of similar triangles to estimate the distance to the plane. What I found was that at about 650 - 750 feet out, these models were visually so small that it was no longer fun to fly them - their apparent wingspan was about half the thickness of the Tx antenna held at arms length. These are powered electrics, not sailplanes, so I have no real desire to let them get any further from me than that - it's not like riding a booming thermal and waiting to see just how high it will carry your plane.

So: Yes, I will fly the Twinstar II with the DX6. No, I will never need to fly it beyond 1500 ft. And yes, Spektrums chief engineer himself fully endorses flying this model at this range with the DX6.

Judging from the excerpt Tree Top posted from one of Jcostas posts (I no longer see Mr. Costa's actual posts, thanks to the blessings of the ignore list), it would seem Mr. Costa is yet once again making forceful and erroneous statements on subjects of which he is ill-informed at best, and ignorant at worst. I leave it to you readers to decide whether to believe Mr. Costa, or whether to believe John Adams, the engineer who headed Spektrums program to design and build the DX6, the man who knows as much about the DX6 as anyone alive.

Happy flying!

-Flieslikeabeagle
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Last edited by flieslikeabeagl; Mar 13, 2006 at 02:25 PM. Reason: typos and clarifications
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Old Mar 13, 2006, 11:58 AM
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Joined May 2004
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Quote:
Originally Posted by kaiser_solsay
Sorry to break the trhead for a moment chaps, but I really must ask.

How do you 'time' a brushed motor and what are the benefits of this mod? I think I should start breaking in my motors also.....is it ok to run them on 1/4 throttle for 10-15 mons instead of using a cup of water?

Cheers in advance.
Kaiser, I've heard that running the motor on a single cell (1.2 V), or two if necessary, for ten to fifteen minutes is frequently used as a break-in method. It's not a very good method, as the brushes are typically rather hard material and can score the commutator during break-in, not to mention the excess heat created by arcing at the brushes can pit the commutator.

It seems that immersing the motor in water and running it at the same low voltage (1.2 V or 2.4 V) for several minutes is a much better method. The lubrication from the water reduces damage to the commutator, and it also carries away the heat.

I've got to run now, no time to respond to the timing part, but if you use the search function you will turn up many posts. The short answer is that motors have inductance - which means when you apply voltage to a motor coil, the current does not reach full strength instantly, but rather takes a fraction of a second (fraction of a millisecond, actually) to reach full strength. To compensate for this delay, we alter the position of the brushes so that voltage starts to be applied to the motor winding a fraction of a rotation earlier than normally - that way, the current has a chance to build to full strength by the time the motor has rotated to the position where it can make use of that full current (and correspondingly strong magnetic field).

-Flieslikeabeagle
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Old Mar 13, 2006, 12:18 PM
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Quote:
Originally Posted by kaiser_solsay
If I can get a ok efficiency from the brushed 480's....why bother with the brushless expenses?
You might want to read through Vintage1's thread "Can motors on 3S lipo" on the power systems forum. That entire thread is about getting decent efficiency out of inexpensive brushed motors, by running them at higher than normal voltage (3S lipo), letting the motors rev, then gearing down to spin a big prop.

If the 480's are used without gearboxes, efficiency will be significantly lower, however you can put so much power through them that enough gets to the prop to fly the model well despite the losses. The downside will be reduced flight times, which may or may not be an issue. With a big lipo pack you could probably get all the flight time you need.

I considered going with geared 480 motors, then found that using twin 400XT's cost very little more.

-Flieslikeabeagle
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Old Mar 13, 2006, 12:24 PM
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Joined Dec 2002
2,299 Posts
Hey now,
Breaking in the motor at low current in water works very well. The brushes on these cheapo motors are very hard and when new their ends are flat, making for very little contact with the com. This causes lots of arching, sparking and that builds carbon on the com and the carbon scores the soft copper on the comutator all of this also causes a large amount oh heat build up, further reducing the power of the motor. Breaking them in under water at low current reduces the heat, washes away the particles of brush as they wear in to the proper curved shape of the comutator and the low currect reduces arching, so you don't get the additional carbon build up. You can improve the preformance of the motor and *double* it's life.
Advancing the timing also improves the ability of the motor to use the power from the batteries and increases the life of the motor. I don't know the numbers to give you, but testing in small direct drive models has shown to me a very noticable difference in flight preformance.
To advance the timing on these s400 and 480 motors just loosen the back plate and turn it 5mm against the direction of run. Um, opposite the way the prop turns. Yes, you could go the whole hog and check amps by running the motor in a drill press and measuring, but the s400/480s all go about 5mm.

On a Switchblade s400 pylon racer under simular conditions just doing the water break in I was able to drop .5 seconds per lap
Adding in the advance timing I was able to get an additional second drop in lap times. That's 1.5 seconds per lap! Also I was able to run one motor through an entire season instead of replacing them every few hours of run time.
RobII
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Old Mar 13, 2006, 12:57 PM
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United Kingdom, Bracknell
Joined Nov 2000
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Quote:
Originally Posted by elfwreck
On a Switchblade s400 pylon racer under simular conditions just doing the water break in I was able to drop .5 seconds per lap
Adding in the advance timing I was able to get an additional second drop in lap times. That's 1.5 seconds per lap!
Was that with the same motor? Any before/after tacho and amp draw figures? A couple of years back I tested four neutrally timed Permax 6V S400s with the same prop and same input voltage (8.8V), and got quite a spread of results. If I'd been flying the worst (13,900 rpm) and switched to the best (15,200 rpm) I'd have got a significant improvement without any tinkering whatsoever!
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