Help with model selection

[Clive Moore]

Hi all,

 I'm new to electric flight, and I need some advice on model selection.  

I have a speed 540 motor, T2m IMCS 35 amp ESC and a 4000 mah 6 'c' cell battery pack. All left over from a powered glider that hit a hedge after the elevator servo packed up. 

I would like a kit, or artf that I can use this kit in. I'd like something that is reasonably easy to fly non aerobatic. Something like a cub for instance. And cheap (ish).

I like anything that is pre 1939 etc.

 Has anyone got any suggestions?

[scott cuppello]

Hi Clive, sorry mate, I'm struggling with this one, the ARTF's are all designed around brushless motors, basically, off the top of my head.....it sounds like you need another glider!

[Tim Mackey]

Probably cheaper ( and certainly a better idea ) would be to buy a suitable brushless setup. Brushless motors and ESCs are cheaper than brushed these days, and FAR more efficient. You COULD if you really insisted, still use the 6 cell brick as a power source on the brushless setup, being roughly equivalent to a 2s liPo.

[Clive Moore]

OK Timbo fair comment,

So Ive fixed the glider and it flys ok (tested today) but its a bit slow on the climb due to the epoxy glass ive used to fix the cracked fus.  

I can not make any sense of any of the numbers on the web sites from retailers of electric stuff

So, what motor, ESC, prop and lipo do I need to fit to give me more power in the climb?

 The current motor (speed 540 with 8x4 prop ) has two machine screws that go through the front of the fuss (behind the spinner) and screws into the front of the motor chassis to clamp it against the front of the fuss (no other formers inside to mount a motor onto).

Any suggestions. The wingspan of the glider is approx two meters.

  

[Tim Mackey]

Give us a bit of time  and I will get back to you.

[Clive Moore]

Brill, thankyou

[Tim Mackey]

Well firstly, the fact that you are going to use a Lipo will have a pretty big difference on the power to weight ratio.

As you are probably aware, to get more climb out power, you really need to be using a bigger diameter prop, with either less pitch - or, if the motor will cope, the same pitch. Matching the prop to the motor is CRUCIAL in electric flight setups.

One of the most important aspects for you sounds like the ability to be able to just bolt a replacement brushless motor into the fus, although you may need to make new holes so lets see what might fit the bill. The 540 can motor is ( I think ) really a buggy style motor of yesteryear, and has ( again..I think )......

A length of around 54 mm ( hence the designation 540 ) and diameter of about 37mm, and weighs a ton ( 220 gram )

If you want quality and a highish price tag, try a couple of options from the AXI range depending on the AUW of the model - which you have not supplied .

If guess around 2lb, then an AXI 2212/26 motor should suffice with a 10 X 6 prop

If its heavier say...3lb or so, then go for a slightly faster revving motor which will still swing the same prop only faster, maybe an AXI 2814/12, on around 10 X 5 prop.

If you want budget then try this hereThis has the advantage of the same dimensions as your old lump.

Or maybe this.... which is an inrunner motor and may cause less hassle installing, but this version will still swing largish propshere

All the above will be good on 3s Lipo packs, and should probably pull 12 -18 A or so. Therefore get a battery of around 1700 - 2000 m/ahr @ 15 -20C ( which are very popular ) and 30A ESC to give you room for expansion later.

typical battery

ESCs

Any of these motors will weigh A LOT less probalby half or even less than the 540, and the battery ditto, so your PWR will be much better, as will duration.

[Clive Moore]

Thats real help Timbo, many thanks.

It looks like the AXI2814/12 with a 10x5 prop (if i can find someone that sells 10x5 folding props) 

One further question, the current battery is a 4000 mamp capacity and gives good duration and provides power to both motor and RX via a BEC. With the lipo should I be looking for a similar capacity if I want to get similar flight times and can I still use an ESC with BEC or do I need to use a seperate TX battery pack? 

[Tim Mackey]

ESC with BEC is fine for this type of setup. 4000 mahr LiPo will be pretty darn pricey, heavier, and un-necessary.

Go for 2000-2500 3s. GHis lighter combo will still give you longer flights even woth lower capacity.

Try Puffin for a 10 inch folder, or get a couple even....9" and 10 " maybe. Its been said many times before, but you really ought to invest in a whattmeter or similar tto. Check out the threads on here to see why.

[Clive Moore]

Timbo, I'm really grateful for all your help with this.

My final plan is :-

Lipo Himodel 2200 3S 11.1v 15c (33.0A) Lithium battery for £25

HM Professional 30A, 2-4S BEC, Brushless ESC £25

AXI 2814/12 motor £40

APC 10x6 folding prop £14

So I can do the whole lot for circa £100 and as you say I'll have something I can transfer on into another model in the future.

Looking at the weight of the new kit and allowing for the extra weight for the epoxy glass repair to the fus overall the aircraft will be lighter than it used to be so I'm now waiting to see how she flies once the kit arrives and is installed (and the weather gives me a chance to get to the flying field!)

Cheers (I owe you a pint)

Clive

 

[Tim Mackey]

Hi Clive...may I just add in something here.

The Axi 2814/12 motor will be pretty close to maximum effort on a 10X6 prop. I am not saying it wont spin it, - it will, BUT the current could be getting up quite high. I did suggest a 10 X 5 or a 9 X 6 but perhaps you are struggling to get the 10 x 5 ? Where did you get the prop from - Puffin by any chance ?

If its a graupner folder with the  black slim E blades, then they are great props, I use one on a model of mine

The reason I mention the prop size is that if the current gets up a bit high....then the ESC may be getting close to its limit and the duration could be " not very long". Now I am sure things will be fine, but I just want to give you a heads up. The reason is that the 281412 has a slightly lower wind, and therefore higher revs, which means it takes a bit more current, hence it is recommended for both 3s or 2s LiPo. On the bigger prop, a 2s pack might be better overall. Then again.... it also depends on how you will use the power. Some glider guiders want short bursts of high power to get up high quickly, and others want to switch on slowly to keep stooging around the sky as the lift falls off.

Do let us know how you get on with it...and please consider seriously getting a whattmeter -  it could repay its cost the very first time you use it.

[Tim Mackey]

Hi Clive...may I just add in something here.

The Axi 2814/12 motor will be pretty close to maximum effort on a 10X6 prop. I am not saying it wont spin it, - it will, BUT the current could be getting up quite high. I did suggest a 10 X 5 or a 9 X 6 but perhaps you are struggling to get the 10 x 5 ? Where did you get the prop from - Puffin by any chance ?

If its a graupner folder with the  black slim E blades, then they are great props, I use one on a model of mine

The reason I mention the prop size is that if the current gets up a bit high....then the ESC may be getting close to its limit and the duration could be " not very long". Now I am sure things will be fine, but I just want to give you a heads up. The reason is that the 281412 has a slightly lower wind, and therefore higher revs, which means it takes a bit more current, hence it is recommended for both 3s or 2s LiPo. On the bigger prop, a 2s pack might be better overall. Then again.... it also depends on how you will use the power. Some glider guiders want short bursts of high power to get up high quickly, and others want to switch on slowly to keep stooging around the sky as the lift falls off.

Do let us know how you get on with it...and please consider seriously getting a whattmeter -  it could repay its cost the very first time you use it.

see here

[Clive Moore]

Hi Timbo,

I can get a Graupner 9x6 folding prop from modelmaniacsonline so perhaps that's a better choice based on what you say. I can also uprate the ESC to the 40 amp version for just another £5 so perhaps that would be better also? 

Re how I use the power, I tend to slow climb looking for lift then glide around a bit and so on. The only time I use full throttle is for the first few seconds after launch just to get the thing going and 'safe' .

I occasionally fly from Ivinghoe Beacon where I use the power to climb back up to the launch site if I loose the lift (saves a very long walk).

Ive read the post re the watt meter and I will take your advise and add it to the order. 

[Tim Mackey]

Well done Clive, you are taking it all in and I assure you will benefit.

A VERY HIGH PROPRTION of people who dismiss electric flight ( and especially modern Lipo brushless stuff ) after one or two failed attempts, do so because they just dive in on poor advice or worse still, - no advice.

If its not too late to upgrade your ESC I would do so.

You cannot use an ESC which is too big in capacity, only the other way around - and this usually releases the magic smoke The only penalty for using a bigger than necessary ESC is a few extra grams of weight, but it does allow the use of it in larger stuff later on, with some of the 50A plus versions allowing up to 6 LiPos.....much more flexible

Yes get the 9 x 6 prop and try it first, see how it goes, and whether the motor is warm /hot after use. If you do get the watt meter, use it to determine if the 10 x 6 prop will be pushing things a little too hard etc.

Good luck....keep us posted on progress.

[Former Member]

[This posting has been removed]

[Tim Mackey]

Good Idea assuming the size required is actually available in that make - if not, you could always chop down the 10" ers.