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Precedent Electra fly

Started by Dav51, April 06, 2016, 16:21:42 pm

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Dav51

Hi Ladies and Gents
I've had a look around to no avail. I'm hoping someone on here has converted an Electra fly to brushless motor from the original brushed 540/600 motor.  I need a motor (inrunner?) ESC and prop combination. I'm not sure of the weight when completed as I haven't started it yet, and I know I'll have to add weight to get the cg right. Anyone got any ideas?

Michael_Rolls

Hi
Oddly enough there was a similar query only a week or two back, looking to update from a Speed 600 - this  was my response:-
A generic Speed 600 on a 7 cell pack will give you performance in the region of 8,650 rpm on a 9x5 prpo and draw 25amps for a power output of 177 watts (these are bench test figures I did back in the days when such a set-up was common.
Going to brushless, a Jeti 30-3 with a 3s 3000 pack will weigh around the same as that brushed set-up but will turn a 10x7 at 11,000 rpm for an output of 475 watts drawing 40 amps. You'll need a new ESC anyway when going from brushed to brushless so make sure it can handle 50 amps to give some leeway.
The Jeti has the advantage of being an almost drop in replacement for a 600 can - it mounts at the front like the can motor although you will probably need to fiddle the mounting holes a bit. It is also a fairly pricey motor - there are lots out there which will offer similar performance levels, so you could do a Google search on the Jeti, check its figures and look for a cheaper alternative - although the Jetis are well made and virtually bullet proof - I have a couple which would still be in use (if I still had anywhere to fly  :'( ) after the best part of 10 years.
Hope that helps - as you see, with a modern set-up you will have alot more power on tap - shorter, higher climbs. A 3000 3S pack will be around the same weight as  a 7 cell nicad and will give more duration.
Mike
Properly trained, a man can be a dog's best friend

nickr100

I've got an electrafly that requires a refurb and brushless conversion. I'll have a look at the jeti motor and see if there's an HK equivalent


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Dav51

Michael that's great info I'll have a look at that but I'm afraid I'm a total novice at this rc lark.
nickr100 I don't understand all these figures yet so I'd be interested what you find out.
I do have a NTM propdrive 3000kv motor and 50a ESC but not sure if they'd be suitable.

nickr100

I seem to remember a sp600 is 28mm case dia so that would be my first route, and look for a low kv motor so it swings big prop slowly


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Michael_Rolls

Hate to say it, but a 3000KV motor wouldn't be suitable. Electric motors are designed to try and turn at a design rpm regardless of the load applied (i.e., in this case, prop size) A 3S pack will give around 10V at the motor so it will want to turn at 30,000rpm (in theory in prctice intenal losses will lower the figure somewhat). To turn at those sort of revs would need a minuscule prop incapable of producing the thrust needed to fly a slow, draggy airframe, and any practical size prop would send the current draw through the roof.
Mike
Properly trained, a man can be a dog's best friend

DarrellW

I would think that this combination would be good, this motor:
http://www.hobbyking.com/hobbyking/store/__36822__Turnigy_Aerodrive_SK3_2836_1040kv_Brushless_Outrunner_Motor_UK_Warehouse_.html
The sk3 are really well made and worth spending the extra few quid on.
40A Turnigy Plush esc, 40A to give a bit of headroom and finally props; I think that 10 x 6 or 7 would work but it may be worth trying 11 x 6 or 7 if clearance isn't a problem.
I think.......I think I am........Therefore I am. .....I think!

Patmac

April 06, 2016, 20:33:38 pm #7 Last Edit: April 06, 2016, 20:34:51 pm by Patmac
Quote from: nickr100 on April 06, 2016, 17:54:53 pm
I seem to remember a sp600 is 28mm case dia so that would be my first route, and look for a low kv motor so it swings big prop slowly



Nick, it's the 400can motors that are 28mm dia, a can 600 is 35mm case & weighs around 180g -200g.   

Dav51, tthe recent similar that thread Mike refered to is here : http://www.rcmf.co.uk/4um/electric-soaring/motor-lipo-setup-!/msg1228515/#msg1228515

As you already mentioned you're probably going to have to add weight to achieve the CoG so you may as well go for a motor that's near to the weight of a 600 motor even if it's capable of giving much more power - the power can be limited by using a smaller prop than would normaly be used. IMO this http://www.hobbyking.com/hobbyking/store/__45916__Turnigy_GliderDrive_SK3_Competition_Series_3850_3_5_960kv_UK_Warehouse_.html would be an excellent choice (Darrell's suggestion in the other thread).
It's 38mm dia & should be a drop in alternative to a Speed 600.

Pax vobiscum

wunwinglow

I converted my 20 year old Electrafly to brushless and LiPo power about 5 years ago.
I fitted an Emax 2210/30 (1300kV) to the front of the nose, i.e. I didn't try to fit it where the old Speed 600 resided.
I use a 3s 2200mAh LiPo and an 8" x 6" folding prop  This combination uses about 160watts,
This modification gave a weight saving of 12ozs. compared with the 8 cell NiMH powered aircraft.
The LiPo is carried immediately ahead of the wing L.E.; the NiMH sat under the wing on the C.of G. Importantly, this configuration maintains the correct C. of G.
Climb performance is pretty much the same - not sparkling but adequate - but glide is better.
HTH
WWL

DarrellW

If you look down the page of the one I posted on this thread it gives the dimensions, the pictures of the motor shows that it can be rear mounted on a bulkhead or front mounted on a mount.
You would have to make something up to fix it in, rear mount would be good because then you could put it in where the cog would be easier to get right; I didn't suggest the one I posted in another topic because it can only be mounted on a front mount.
I think.......I think I am........Therefore I am. .....I think!

Dav51

Got them thanks, I'm going blind!
So that's what I'm going with then the SK3 with a 40A esc and a prop I'll worry about later, but i'll try one of the ones you mentioned DarrellW.
I don't fancy putting a motor on the nose i'd like to keep it as original as i can and I'm sure there's plenty of room up front for a battery and anything I need for the CoG.
The jeti motor although bulletproof is just too expensive considering I'm new to all this.
Thanks for all the replies guys

Patmac

Not disagreeing with the choice but surely a 600 can motor would have been front mounted same as the Glider Drive, so there should be no need to rear mount the SK3 one on a bulkhead or a mount as it can be nailed directly to the nose ring ?
Pax vobiscum

DarrellW

Agreed, but it may work better if rear mounted if it needs to go further forward to get a decent size battery in and get the cog right, I don't know that model well enough to be specific about it but in my experience with this type of thing flexibility often solves problems.
I think.......I think I am........Therefore I am. .....I think!

Patmac

Darrell, if it's the model I think it is, the Electra Fly's a rudder/elevator/motor only e-glider about 7 ft span.
Pax vobiscum

DarrellW

April 09, 2016, 08:10:00 am #14 Last Edit: April 09, 2016, 08:13:08 am by DarrellW
Quote from: Patmac on April 08, 2016, 21:29:32 pm
Darrell, if it's the model I think it is, the Electra Fly's a rudder/elevator/motor only e-glider about 7 ft span.

So really it's more of a thermals model than aerobatic, in that case it really  doesn't need a lot of power.
Might even run on something like an Emax 2220/07 that does about 250 W and runs nice on a 30A esc on 3S and 10x4.5 prop.
I think.......I think I am........Therefore I am. .....I think!

wunwinglow

Quote from: DarrellW on April 09, 2016, 08:10:00 am
So really it's more of a thermals model than aerobatic, in that case it really  doesn't need a lot of power.
Might even run on something like an Emax 2220/07 that does about 250 W and runs nice on a 30A esc on 3S and 10x4.5 prop.


I refer you to my earlier post - as I said I've had this model for some 20 years, 5 with brushless/LiPo :af

DarrellW

April 09, 2016, 18:07:47 pm #16 Last Edit: April 09, 2016, 18:11:30 pm by DarrellW
Quote from: wunwinglow on April 09, 2016, 11:31:41 am
I refer you to my earlier post - as I said I've had this model for some 20 years, 5 with brushless/LiPo :af

Oops, didn't notice that - bit more power but the real difference is the prop; I like bigger diameter lower pitch in a glider purely for less speed and better climbing power; funny that - i've got that motor in a plane of similar weight, that's what made me suggest it  :af
I think.......I think I am........Therefore I am. .....I think!

Dav51

April 19, 2016, 15:52:57 pm #17 Last Edit: April 19, 2016, 15:57:17 pm by Dav51
I can't believe the drama's I'm having with this.
Right, The Turning Aerodrive 2836 1040kv motor has to be back mounted with a propshaft adapter (for a pusher prop that comes with the motor) making my folding prop and spinner useless.
The prop shaft comes out of the wrong end of the motor.
There's a circlip and grub screw that end up being the same end of the motor if you reverse the shaft therefore making shaft reversal impossible.
You live and learn
Thanks for the replies.

Dav51

April 26, 2016, 10:39:53 am #18 Last Edit: April 26, 2016, 15:25:38 pm by Dav51
I went with a Turnigy Gliderdrive 960kv in the end, a tiny bit of sanding to make it fit but everything looks fine. It says max Amps 35 with 510 w power so roughly the same as the Jeti mentioned earlier. I'd already got a 50A esc so hopefully all is well. So just a spinner and prop to go.

onetenor

I know I'm late but someone might be interested. Surely the fast motor  3000Kv Could be geared to give real torque and power at lower Watts and amps.A ten to  one  ratio would be a good starting point.swinging say a ten by seven but please use your meters to check loadings.