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Comments: 7


New toy for slope & field

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Re: New toy for slope & field

Post by Andy Sayle on Wed Jul 14, 2010 1:10 pm

Like I said Bob, if you were to up the Prop to a 14x9.5, you would really notice the difference in climb rate Smile If you could find a 13x10, that would be pretty cool too.

Rich, a budget, fairly low powered option for you. The Himax HA2825-2743. It's a 28mm geared motor, and should be pulling about 35-40 amps on a 3s lipo with a 13x8 prop (400 watts ish). About $100 in the US, although I have no idea of any Himax suppliers in the UK...

Andy


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Re: New toy for slope & field

Post by Andy Sayle on Wed Jul 14, 2010 1:12 pm

Oooh, or, if you want to go proper lightweight, you could try a Mega 16/25/4 with a 10x6 prop, 3s lipo for about 25 amps. You could get away with a 1250mAh lipo then Smile

Andy

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Re: New toy for slope & field

Post by Brian Colclough on Wed Jul 14, 2010 1:16 pm

Galaxy models list some Himax motors Wink

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Re: New toy for slope & field

Post by Rich on Thu Jul 15, 2010 12:28 pm

How does this sound,

Mega 16/25/2 geared 4.4:1, 3S 2.6Ah LiPo, 15x9 prop (2800 fpm, 45A) approx

Andy what do you reckon your Graphite fpm was. WAS being the operative word

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Re: New toy for slope & field

Post by Andy Sayle on Thu Jul 15, 2010 1:06 pm

Was, ha haa, I like it Smile

2800fpm is about 14m/s climb rate, which is probably not far off what my Graphite was doing. I've just checked a couple of current draw plots, and it was getting to 150 meters in about 9 seconds, so a climb rate of 16 ish meters per second, or about 3100fpm give or take. Bear in mind I am taking that data from seperate altitude/current measurements, so there may be a bit of error in it.

I've got a Mega 16/15/2 in my little green thing. They are very nice motors, and would cope with a higher current than 45A if you limit the motor use to bursts of about 10s max. I'm running mine at about 50A continuous, and it does get pretty warm, but bursts of power should be fine. That setup will be a good starting point though.

Another good motor to consider, might be the HET EDF motors. They are very good also, and a fair bit cheaper than the equivalent mega motors. They would work equally as well coupled to a gearbox.

HTH
Andy

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Re: New toy for slope & field

Post by Tim on Thu Jul 15, 2010 1:28 pm

Just one thought Rich - what is the "C" rating of your rather small capacity LiPo?
45- 50 A from a 2300 pack is quite high at around 20C ( although my mega 22/20/3 equipped Alienator has a 2300 pack and pulls around 50A peak ) . However the packs are 30C rated.

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Re: New toy for slope & field

Post by Andy Sayle on Thu Jul 15, 2010 1:38 pm

Meh, 45A from a 2300 pack is naff all. I'm pulling... Ah. Wrong tense. I was pulling approx 65-70A out of the 2150mAh packs in the Graphite. Those were nothing special, just the Hobbycity Rhino cells, rated at 20C.

The C rating doesn't really apply to low burn time applications, like getting a glider a few hundred feet up in the air quickly... The only effect it will have, is how well the packs hold their voltage for the few seconds that the motor is on. Obviously the newere better packs, will be slightly better.

Andy

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Re: New toy for slope & field

Post by Tim on Thu Jul 15, 2010 1:40 pm

I wasn't asking you Mr hooligan /maniac/ insert your own description here.
Very Happy

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Re: New toy for slope & field

Post by Rich on Thu Jul 15, 2010 1:42 pm

The packs are 2600mAh 40C 100A

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Re: New toy for slope & field

Post by Tim on Thu Jul 15, 2010 1:43 pm

Thats good Very Happy

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Re: New toy for slope & field

Post by Rich on Thu Jul 15, 2010 2:18 pm

I'm not looking to keep the power on continuously just climb & glide I think, much the same as the larger "E" soarers

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Re: New toy for slope & field

Post by Andy Sayle on Thu Jul 15, 2010 2:22 pm

Hence the C rating being a bit of a non-issue Smile

Andy

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Re: New toy for slope & field

Post by Tim on Thu Jul 15, 2010 2:39 pm

Yeh I understand that but was just being cautious - for all I knew the packs were low rated 15C or summat - and caning them ( even for short "burst" sessions ) aint good for overall pack life.

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Re: New toy for slope & field

Post by Andy Sayle on Thu Jul 15, 2010 2:44 pm

A short pack life is well worth it for the size of the grin on your face when you open the taps Wink

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Re: New toy for slope & field

Post by Tim on Thu Jul 15, 2010 2:46 pm

Well I guess it is for those with deep pockets.

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Re: New toy for slope & field

Post by Andy Sayle on Thu Jul 15, 2010 3:00 pm

The Rhino packs I use came in at approx £13 each. If I get 26 flights from them before they need replacing, that;'s 50p a flight, and a factor of 4 cheaper than running something like my Jet.

In reality, the oldest packs (that haven't been crumpled in the crash, or lost when ejecting from a funjet or similar!) have over 120 cycles on them. So that;s not far of 10 p per flight. You can't get much cheaper than that Smile

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Re: New toy for slope & field

Post by Rich on Thu Jul 15, 2010 10:36 pm

Now that you've seen the glider Andy what about this little number,

http://www.sloughrc.com/asp/default.asp?itemid=M-MM1215EXT 77g with gearbox

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Re: New toy for slope & field

Post by Sam Thomas on Fri Jul 16, 2010 7:56 am

Looks very nice and bright!!!
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Re: New toy for slope & field

Post by Andy Sayle on Fri Jul 16, 2010 8:49 am

That motor will give you a very light overall setup, I would limit the current (in bursts of 10s or so) to about 30-35A max. It's a 300 size motor, with a can diameter of 25mm or so, and if you do want to go down that route, I would probably look at using the 6:1 gearbox, and a 2s lipo, coupled with something like a 14x9 prop for about 30 amps. If you go with a 3s battery, you will need to prop down to about a 10" pitch prop to keep the current below 35A or so. You might need some pretty large 2s lipos though to get the balance right without adding weight.

If you want to try it, it just so happens I have a 1215/Extreme (6370Kv) motor sat in my motors box. I bought it for an EDF model, but it was a bit too hot for the 55mm fan I got. You would just need the gearbox (which can be bought seperately through Puffin IIRC)....

Andy

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