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Old Oct 24, 2014, 07:27 PM
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Phil U's Avatar
Australia, NSW
Joined Feb 2013
335 Posts
Help!
Free Flight Timer

Hi all,

I'm building a first powered model for my 5 year old. It's a 12" span Canard style balsa scratch build originally designed for a Cox 010.

I have a little Turnigy outrunner for it instead with a 6 amp speed controller and 450mAh 2s battery pack.

Now that I have those items I realise that it's not going to work. For starters the ESC needs receiver input. And secondly there's no way to cut the motor after 30 seconds or whatever.

Please note that this is a toy and not a competition model. If anybody can help out with a simple method of getting the motor to run for 'x' amount of time I'd greatly appreciate it. I know it's possible to program ESC's but that requires expensive equipment.

Cheers,

Phil.
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Old Oct 24, 2014, 11:50 PM
Registered User
Gunbarrel, CO
Joined Dec 2006
115 Posts
A 12" span with a 450mAh pack? And a 6 amp ESC? Holy cow! No way can you suddenly cut the motor. It would crash headlong into the ground with that weight IMO. I could be wrong, of course. But add a receiver just to control the throttle. Then you can bring it down gradually.
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Old Oct 25, 2014, 01:37 AM
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Staffs, UK
Joined Nov 2003
10,770 Posts
The simplest way, as your subject heading suggests, is to use a FF timer. There are several available but they all cost money e.g. http://www.kpaero.com/ProductReport....peed%20control or look at "Similar threads"at the bottom of the page.

For a "toy" it would probably have been easier and cheaper to use a brushed motor which can simply be switched (without an ESC) using a homemade timer...but I guess it's a bit late for that .

Steve
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Old Oct 25, 2014, 02:27 AM
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United States, OR, West Linn
Joined Feb 2010
69 Posts
Check out this thread re the E20 event materials and timer

http://www.hippocketaeronautics.com/...?topic=14519.0

--Bill
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Old Oct 25, 2014, 02:45 PM
B for Bruce
BMatthews's Avatar
The 'Wack, BC, Canada
Joined Oct 2002
11,622 Posts
Also for casual free flight cruise around sport flying you'll find that the power system is grossly over the top.

As suggested to keep it cheap and simple the best option would be to switch over to a small brushed motor. As for timing the motor I'd go with a two AAA Nimh cells and simply set up a charger that times the charge. The motor then runs for around 30 to 60 seconds based on how long you charge it for and then runs out of power. The cells won't like this sort of treatment but they'll still work for a hundred or so such flights before they don't work well any more.

I also think that you're going to find that the 12 inch span is a trifle small for the weight of the power package even if you find one of the small geared GWS motors and run the two AAA cells as a power storage. Something more around the 18 to 20 inch span range would likely be better. Just don't over build it to avoid a heavy wing loading.
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Old Oct 25, 2014, 06:27 PM
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Phil U's Avatar
Australia, NSW
Joined Feb 2013
335 Posts
Thanks everyone. I've never used electrics before and frankly they are far more confusing than glow. It seems the only way to learn is through experience.
I've obviously bought all the wrong stuff but that's ok, it can all go into another project, perhaps a glider.
I am going to order some much smaller equipment because as you say, this wing will never carry the battery. I like BMatthews suggestion re the charging method, otherwise I will pick up a combined micro receiver/ESC with a brushed motor.
I'm running Futaba, so if anybody wants to tell me exactly what I need to buy, that would be great! (Presume that I am completely ignorant when it comes to electrics, lipo's etc.....)
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Old Oct 25, 2014, 07:02 PM
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Phil U's Avatar
Australia, NSW
Joined Feb 2013
335 Posts
My apologies I provided some mis-info. Wing span is 18". Weight prior to engine and paint is 37g (1.3oz)
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Old Oct 25, 2014, 07:14 PM
B for Bruce
BMatthews's Avatar
The 'Wack, BC, Canada
Joined Oct 2002
11,622 Posts
You'd find that a model of that size and weight would have also been somewhat generously powered even with the original .010 mounted on the nose.

If you can find something like a Mabuchi 180 or 250 motor that is wound for running off 3 volts you'll likely find that you can fly your model nicely. You'll want to find a push on prop for the motor shaft or a prop adapter that'll allow you to use a 4 to 5 inch prop that has roughly 2 to 3 inch pitch. If that doesn't fly the model in an "uphill glide" then try a prop with a little more pitch.

In terms of performance for sport flying you don't want or need a lot of climb power. For flying in more confined spaces you literally want it to climb at around the same rate it glides. If it takes a good 30 to 40 seconds of motor time to reach 50 feet that's just about perfect for sports fields surrounded by housing. If you're out in the wide open spaces then a little more climb would not be at all bad. But expect longer chases.

Motors are funny creatures. They don't really have a peak power like an engine. To get more power from then you can use a bigger or higher pitch prop that pulls more current from the battery pack. Up to where the built in resistance limits this you can draw enough power to get things done. On brushed motors the brushes and winding resistance limits this to some extent. Brushless motors don't have this issue and will happily suck enough power from the battery to burn themselves out if you load them down to that point.

So that's why I suggested more pitch to get more climb. Up to a point this works well. If you run into the limit you simply need a little larger motor.

Another option if you can find them down your way the GWS IPS range of geared motor units would be the way to go. Get one that has a numerically low gear ratio so it'll more happily turn a smaller prop. These motor units provided good performance for their size.
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Old Oct 25, 2014, 10:45 PM
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flyelectcl's Avatar
Joined Oct 2008
198 Posts
I have done some small FF using electric with a cheap RC car transmitter and receiver . I use the Hobbyking 3ch, costs about $30. Very easy for sport flying, no need for specialized timers.
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Old Oct 26, 2014, 04:41 AM
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Staffs, UK
Joined Nov 2003
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If you've decided to go with a brushed motor then I'd suggest using one from a Parkzone UM model (P51/Corsair etc). They're readily available as spares and run well from the equally easy to find 1S lipo batteries those models use. Add to that a cheap homemade timer ala "Peterborough timer" http://www.peterboroughmfc.co.uk/tec...e_FETtimer.pdf (much discussed round here over the years - try a search).

That gives you very workable system. I've used that setup in dozens of small FF models, mainly for indoor use but they also work outside in VERY light winds.

Steve
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Old Oct 26, 2014, 07:15 AM
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Phil U's Avatar
Australia, NSW
Joined Feb 2013
335 Posts
I've just weighed everything that I have and it comes to 97g wet. I've included in that the 2s battery pack, propellor and a frsky receiver.

When I plug the numbers into this excellent calculator that I found this morning it gives me a cubic loading of 7.5 oz per cubic foot. That's a little high for a 'parkie'.

So I've just ordered a 130mAh 2s pack which apparently weighs only 15g. That will get my weight down to 82g, which puts me a tad over 6 oz per cubic foot.

I will give this a try with the receiver and see if it glides, otherwise it's back to the drawing board.

Thanks a lot everybody, I hope this has been a help to somebody else looking to build a 'simple' toy.
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Old Oct 26, 2014, 07:21 AM
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Phil U's Avatar
Australia, NSW
Joined Feb 2013
335 Posts
slipstick that timer looks the goods. If I have too much weight I will pick up a brushed motor and run with your system.
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Old Nov 01, 2014, 10:02 PM
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Joined Mar 2011
1,360 Posts
Hi Guys, i just read this threat and... well, FF electric can be a nice hobby, easier than glow or rubber, as the power is always the same, and can be as small as a peanut model.
i suggest to go for the simplest way, get an nice KB timer and a very small brushless, 5 grams is ok, and a very small ESC. i have an nice linnet FF electric, and is a joy to fly.

Here a video.
Frog Linnet FF electric trim season 2 (0 min 51 sec)
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Old Nov 02, 2014, 10:13 PM
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Rhudson1960's Avatar
United States, NY, Fulton
Joined Sep 2013
116 Posts
I have found that an 1811 higher KV (2000+) brushed motor is close to an .010 glow engine. I have been thinking about throttle only setups for free flight designs as well. This should work if you have room for the equipment. Better yet, down the road you could add a rudder servo then elevator. I fly a foam version of the 22" span Sharkface on an 1811 motor, rudder & Throttle only and I am getting good performance, and I am not terribly experienced in RC. Rudder-Only is Free Flight that takes suggestions.
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Old Nov 04, 2014, 07:33 PM
Balsadustus Producerus
Escondido, CA USA
Joined Jan 2001
1,043 Posts
Occasionally...
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