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Electric setup advice

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Will Anderson02/02/2019 22:45:53
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33 forum posts

Iv'e just bought my first RC aeroplane. It's a 2nd hand high wing trainer, 58" wingspan, film covered balsa construction. Receiver and servos are all installed and it has a 25 glow engine.

I would like to convert it to electric power so Iv'e been reading lots of posts on the forum to gain a bit of knowledge (I hope).

[img]https://i.imgur.com/b8RijQz.jpg[/img]

[img]https://i.imgur.com/jnpQQ6q.jpg[/img]

[img]https://i.imgur.com/tEarONW.jpg[/img]

[img]https://i.imgur.com/hNS7aT9.jpg[/img]

[img]https://i.imgur.com/yI1jlne.jpg[/img]

Will Anderson02/02/2019 22:56:56
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33 forum posts

Following up from my previous post....

https://i.imgur.com/b8RijQz.jpg

https://i.imgur.com/664iCAk.jpg

https://i.imgur.com/hNS7aT9.jpg

https://i.imgur.com/jnpQQ6q.jpg

https://i.imgur.com/tEarONW.jpg

https://i.imgur.com/yI1jlne.jpg

I realise this is probably more power than I need but I'm hoping that I can restrict the power available with the program card. My hope is that I can transfer the electrics to another more advanced model when I'm more experienced.

Pete B - Moderator03/02/2019 09:06:55
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Moderator
7572 forum posts
732 photos

Hi Will,

Welcome to the forum. I'm sure you'll get plenty of good advice here but I see you have a problem with inserting photos. Have a look at these threads Creating an Album and External Photos in our Forum User Guides section which should help.

Pete

Percy Verance03/02/2019 09:23:27
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8109 forum posts
155 photos

Hi Will

First of all I'll ask several seemingly unrelated questions if I may. Do you have any model flying experience, and are you in a club? Where did you buy the model? What is the model? Has it flown?

If this is your very first model Will, you're going to need more help than can be offered on here. Reading the posts on the forum is certainly an excellent start Will, but *hands on* help from an experienced flyer in a club environment is the way to go.

I'm not hugely experienced in electric flying myself, although I have been flying with electric power for 3 years or so now. I'm not sure you'll be able to reduce power in the way you mean with the program card Will. The throttle stick on the transmitter does that! And to a lesser extent propeller selection on an electric model will do the same, although again, prop selection on an electric model has to take in such factors as model size and weight, ESC rating, motor size etc. There are lots of examples of motor/battery/esc set-ups on the 4 Max website. George at 4 Max also offers sound advice too. But before you get that far Will, you really need to look to find your nearest club, and seek advice from the electric flyers you'll meet there. Their help and advice will be free, and is based on years of hard won experience. This forum is excellent Will, but it can't take the place of a club with experienced members.

Please feel free to carry on asking as many questions as you feel necessary Will. yes

 

Edited By Percy Verance on 03/02/2019 09:25:19

ken anderson.03/02/2019 09:32:39
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8425 forum posts
772 photos

welcome will from me....nice surname there also. Ask as may questions as you want as Percy has said...

ken anderson...ne..1....anderson dept.

Steve Hargreaves - Moderator03/02/2019 11:18:13
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Moderator
6716 forum posts
189 photos

Long lost Great Great Grandson perhaps Ken.....teeth 2

Will, you can easily reduce the amount of power produced by an electric set up by simply fitting a smaller prop so if a set up fitted with a 10x6 prop produces say 500 watts dropping to a 9x6 will reduce that to 400 watts (NB these figures are purely to illustrate the point....).

But I guess we are a little way off that bit.....start at the beginning, read lots, ask lots of questions & it will all start to become clear.....you could do a lot worse that starting here... **LINK**

Former Member03/02/2019 11:38:50
724 forum posts

[This posting has been removed]

Will Anderson03/02/2019 12:16:21
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33 forum posts

Thanks Pete for the pointer on posting pics and thanks to others for input. Yes Ken nice surname and forename is good enough for a prince so I guess it's win/win yes

This is my first foray into anything RC. The model is a high wing trainer that was an ebay purchase from a late gentleman's collection. I'm also looking at a flight simulator that will work with my futaba TX to get plenty of practice. Theres also a local club that I will most likely join.

The pics below are on my short list for parts shopping. Any feedback would be appreciated.

Steve Hargreaves - Moderator03/02/2019 12:39:41
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Moderator
6716 forum posts
189 photos

Are you sure its a 25 glow engine Will.....58" span sounds quite big for a 25.....might it be a 40 perhaps? Do you know the name of the model at all?

If a 25 will fly the model then the motor/set up you have there might be a bit too powerful. On the other hand it looks pretty good for a model of that size. A "40 sized" Trainer is usually around the 5lb mark & a good rule of thumb for electric powered high wingers would be around 80-100 watts per lb. The motor is rated at 60A so if we combine that with a 4S battery that's a max of about 800 & a bit watts......as mentioned earlier we can reduce the size of the prop to reduce the power produced. Do you have a Wattmeter? If not then go & buy one....you can't really do much experimentation in electric flight without one.

Another thought.....with the kv of that motor you'll likely need a fairly big prop to allow it to develop full power. (I see a 12x9 is "recommended" but this isn't much use as it depends what battery you use....a 12x9 on that motor connected to a 7S battery will release the magic smoke very quickly I suspect.) How much ground clearance do you have? a 25 is likely to use a 9" prop so much smaller than the electric set up is likely to need.....

IMHO you are on the right track here but maybe a little extra thought through some of the "Gotchas" might be useful....wink 2

Percy Verance03/02/2019 12:47:47
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8109 forum posts
155 photos

Hi again Will

It might be best to hold off on any purchases until you get some additional advice Will. As Steve points out above, that set -up doesn't seem the ideal one for a relatively lightly loaded trainer type model. And again as Steve says, the *recommended* prop may not be any good at all for some types of model, as there are several factors that have to be taken into consideration. Just don't buy anything yet Will, because with respect you might be buying completely the wrong set- up...... that motor looks like it's way too powerful for a model fitted with a .25 for a start.

Hang fire Will and join that local club. There you'll get some first hand experiences of electric set-ups, which is far preferable to window shopping if you're not sure what to buy.

 

Edited By Percy Verance on 03/02/2019 12:53:47

PeterF03/02/2019 12:56:13
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407 forum posts
566 photos

Running the set up through e-calc, an on line electric set up calculator, the Ripmax Quantum 40 motor on 4S battery as you have shown will give an rpm of around 10,000rpm. Run this with an 11 x 6 prop and you will get a current draw of about 37A (well within motor and ESC specs and battery capability) giving just over 500W, which will be good for a 5lb weight trainer. If you then develop your skills, the prop could easily be increased to a 12 x 7 which would draw 52A (still in specs for motor, ESC and battery) giving 700W and aerobatic performance. As others have stated, you can not use the program card to limit the motor output, you do this by changing the prop size. One thing with electric is that the motor tries top turn at the same rpm whatever the prop that is fitted, so if you fit too large a prop it draws too much current / power and blows the motor or the ESC. Likewise, in your case fitting a smaller propeller does not allow the motor to rev faster, if you fitted too small a prop on an IC engine then it would scream.

Will Anderson03/02/2019 12:58:05
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33 forum posts

Hi Steve

I will remove the cowling tonight and check the engine size. The model has graphics saying "Hornet". It has a steerable front wheel, do I just measure from the centre of the spinner and divide the prop size by 2 to check ground clearance? The battery I have in mind is a 4S 5500mah.

Martin Harris03/02/2019 13:17:09
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8736 forum posts
214 photos

I suspect it may be this model although there seems to be a mismatch in the wingspan - if so, a 25 is massively under the recommended power but there are specs for an electric power train...

0.46 ~ 0.52 Two Stroke Glow Engine
42mm Motor 650kv (EP Version)
3300mAh ~ 4000mAh 4s Lipo Battery (EP Version)
60A OPTO ESC (EP Version)

A copy of the manual can also be downloaded here.

Edited By Martin Harris on 03/02/2019 13:20:36

PeterF03/02/2019 13:53:16
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407 forum posts
566 photos

If it is the Hornet noted above, then the set up I gave above with an 11 x 6 prop for starters. The recommended motor has a kV of 650 so would spin the prop more slowly than your 800kV motor, hence keep the prop size down a bit to limit the power output.

For ground clearance, you can measure from centre of spinner to ground, but as the nose gear is often sprung with a coil in the wire leg, you need to allow a good 2" of clearance, perhaps more for a heavy landing when the nose wheel bends quite a lot to absorb the shock.

Also, if it is the one shown then you will not need to make alterations to the model for the electric conversion as it already has a hatch for the battery between the wing and the firewall.

Steve Hargreaves - Moderator03/02/2019 14:44:50
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Moderator
6716 forum posts
189 photos
Posted by Will Anderson on 03/02/2019 12:58:05:

Hi Steve

I will remove the cowling tonight and check the engine size. The model has graphics saying "Hornet". It has a steerable front wheel, do I just measure from the centre of the spinner and divide the prop size by 2 to check ground clearance? The battery I have in mind is a 4S 5500mah.

Hi Will...yep that's it...a 12" prop is 12 inches in diameter so will have a radius of 6 inches. The 11x6 PeterF alludes to is pretty much the same size prop as the 40/46 glow motor would have used so should fit very well & probably provide the right sort of power (this is where the wattmeter comes in...it fits between the battery & the ESC & tells us how much power is being consumed). If you needed more power then you'd need to fit a larger prop (either in diameter or pitch) to make the motor work a bit harder. If ground clearance gets a bit marginal you can always fit larger diameter wheels too but again don't forget that going from a 3" to a 4" wheel will only gain you another 1/2" ground clearance....dont know

Battery sounds fine....quite a large capacity so probably heavier & physically larger than it needs to be but the model should handle it just fine. Do check you can get it in through the hatch though & if needs be go for a smaller capacity like a 4500mAh or even 4000 mAh.....these should still give you plenty of duration. (In case you didn't know the capacity of the battery in mAh or Ah represents the amount of energy it can hold...& this translates as how long the motor will run for. Hence a 5000mAh battery will hold twice the energy & last twice as long as a 2500mAh battery for a given set up but of course will weigh much more & be physically bigger too. Words & phrases like "compromise" & " you don't get something for nothing" are very useful to remember with electric power wink 2)

Will Anderson03/02/2019 22:07:53
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33 forum posts

Thanks for the input guys

Martin is correct, it is that exact Hornet, thanks for the link to the manual. The engine is a SC 40 and the prop is 11x7. The 1st prop number is obvious but with the 2nd number, does higher mean more pitch = more thrust? If so an 11x6 or a 10x7 would mean less thrust? The 11" prop has just over 2" clearance from ground so I don't think I'll go any bigger.

Regarding the wattmeter, is it better to bench test this or install one in the model?

Percy Verance04/02/2019 06:43:48
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8109 forum posts
155 photos

Hi again Will

Regarding the pitch of a prop, a straightforward way to visualise it would be to think of the prop turning a single revolution in a solid mass. A 6 inch prop would travel forward 6 inches, a 7 inch pitch would travel 7 inches etc......

It's similar to the gearing in a car, although engine torque is of course a factor. Your engine has to be able produce the torque to turn the higher pitch props at usable revolutions. Personally, with the models I fly I tend to stick with no more than 5 or 6 inch pitch props, because the lower pitches provide sufficient performance for me, plus you also get an element of braking effect on landing approaches which you won't see with a higher pitch. Experimentation is key with prop selection Will, although experience will eventually mean that once you've selected a couple of new props, one will almost certainly be bang on........

Testing with a wattmeter is almost always done on the bench/ground prior to flight Will. yes   A meter isn't usually installed in the model. And one more thing Will. When you are connecting, testing or running an electric motor to ascertain correct rotation, always always ALWAYS leave the propeller OFF until you've finalised everything. And don't forget to balance the prop, as some are way out of balance. You can buy a pretty good prop balancer for just a few quid.

And I personally would choose a larger propeller Will. That SC40 will rev quite enthusiastically on that 11 inch prop, which will mean the model flies faster. The pitch is also higher than necessary for a trainer model. Not quite what you need when you're learning to fly. When you switch to that electric motor I'd use a 12 inch prop if there is ground clearance. 

 

 

 

 

 

 

 

Edited By Percy Verance on 04/02/2019 07:01:13

onetenor04/02/2019 10:07:25
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1900 forum posts

Just 2 points A smaller prop Will allow an IC motor to rev faster, Hence the scream. Two / too small a prop won't have enough weight to provide flywheel effect for starting.. Unless of course using an electric starter.

Nigel R04/02/2019 10:24:56
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2981 forum posts
471 photos

Will, welcome aboard!

If you have a simulator, my biggest bit of advice would be to get as much time in, on the simulator, as you can. It will teach a lot of skills that translate very quickly to the real world.

Your trainer looks good. Are you dead set against using the glow motor that is already installed? You might find you get on perfectly well with it. And it may very well be easier to go with what you have, rather than taking on a project to convert it.

ken anderson.04/02/2019 10:29:49
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8425 forum posts
772 photos

Will, I would use the ic motor version to learn to fly, it will be a bit a bit more ding proof than the electric set up...ie...bent motor shaft, crunched up lipo's(which will be done for)...with ic you may only have to have some spare props at hand...…and a can of fuel to get straight back in the air....

ken anderson...ne...1...bent props dept.

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