Electric power for old timer designs

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06 Aug 2018 19:50 #1 by oldadger
Electric power for old timer designs was created by oldadger
Can anyone help please. My interest is vintage IC powered models, I am a returnee to the hobby and having built a few IC powered small models (mostly Vic Smeed designs) I want to build a larger model with electric power. I have a 62" 'Viking' kit by Belair. they recommend a Hacker A30-12M 350watt brushless outrunner or any radially mounted 200watt motor. Now I know Hacker are excellent motors, but at 70 quid a throw it's a bit dear for me. I have found on Hobby King, for example a Turingy D2830 - 1100Kv 305watt brushless outrunner which sells for £7.30p!! talk about chalk and cheese - I know you get what you pay for, so I am really confused. Can anyone suggest a decent reasonably priced set up, including what ESC and Lipo is needed ( which I think needs to swing a 10 inch prop ) for this model.

Many thanks

Alan

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06 Aug 2018 20:43 - 06 Aug 2018 20:48 #2 by THE BLACKBIRD
Replied by THE BLACKBIRD on topic Electric power for old timer designs
I think for what we use Hacker are way over priced,,
HK motor are good for the price
Allen welcome to the forum, there is a intro thread on here you can use to tell us something about yourself, if you so wish of course

Tony
Last edit: 06 Aug 2018 20:48 by THE BLACKBIRD.

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06 Aug 2018 21:52 #3 by Polyphilla
Replied by Polyphilla on topic Electric power for old timer designs
Hi Alan, welcome to the forum. I had a similar problem to yourself when I returned to the hobby after a 40 year break, (I'm 62 now) electric power was the way to go and it confused the hell out of me........ now I'm well hooked. :cheer:
What we need to know first is the weight of the model & it's flying characteristics, you've said it's a 62" Viking, would I be correct to say that's a pretty light model for its size? I found one on youtube that's 970 grams, the bloke's using a 3s lipo giving 487 Watts and 1740g of thrust...... that's vertical performance!!!!!!!!!
I've got a few models about that span, but the only ones I've got that light are powered gliders.
You're probably looking at a 3s lipo and figure on roughly 100W per pound ..... that's why the weight is important.
When you get that sorted you need to figure out what KV motor you want, that will determine what rpm you'll get at the prop.

I've never paid a lot for a motor and I've never had one break, I think the secret is to get something that will do what you want, and a bit more besides. Never push them to their limit just to save a few grams or a few quid. I've bought most of my gear from HobbyKing, they used to do a range of motors called PropDrive I think they were, not sure if they still do them but I've had no problems with Turnigy.
Tell us a bit more about the model & I'll tell you what I'd use.

Phil Wood .... (Pol) [badass]

Why struggle for perfection?...just cheat & copy me.:-)

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07 Aug 2018 00:07 #4 by Eric
Replied by Eric on topic Electric power for old timer designs
As Pol put - 100 Watts per lb of model weight - guesstimate the motor and battery, any radio gear, and add that to the airframe weight.
Having found the total weight and calculated how many watts, Add about 25% (we call it headroom).
Find a motor that can deliver that many watts, and the notes will tell you what prop and what battery you need.
There will be a Kv number on the motor - that's how many rpm's PER VOLT the motor will deliver.
The notes will also tell you how many AMPS the motor will draw to achieve that RPM. Add 25% again (head-room) and that's the size of speed controller you need.
They will also give you the VOLTS required. (A lipo gives 3.6 volts per cell when it is effectively flat).
-
Lipo batteries are graded on two numbers - the number of cells ie 3S (three cells wired end to end (Series), and the power output, for convenience say 1000 - that's one thousand milliamps - or one amp. In other words the 3S 1000 can deliver one amp for one hour at approximately 11.5 volts - (or a lot more amps for a shorter time - 2 amps for 30 minutes, 4 for quarter of an hour, and so on - slightly less in real life).
Now you have an idea of what motor, speedo and battery, you need, check what their weights are, and go round the calculation again.
Did you have more than enough power for the weight?
-
There's lot more to learn yet, but let us know if you have followed to this point.

if you are calm and collected when all about you are going berserk - you've missed something important!

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07 Aug 2018 00:51 - 07 Aug 2018 00:54 #5 by one tenor
Replied by one tenor on topic Electric power for old timer designs
Hi Al welcome to the forum. I'm in process of returning after a long absence ad I'm 75 and learning a lot too. I can't recall what my last motor was and from whom but very reasonable I thought with 2 nice props. 1 CW and 1 CCW. I can't get to my shed to check and our handyman stopped coming for some reason.so can't ask him to fetch it for me and wife and son are stuck like me, However I digress as usual. May I suggest you look on The Bang Good site for motors,RC gear, tools etc etc Also Gear Best site Good products and good value Thinking hard I think I ordered the motor from Robot Birds who carry a vast array of motors. If you go to the RCME Model Flying forum you will see Robot Birds listed as a shopping partner which you just click on. There are also guys on there who will be only too glad to offer advice. Look and see. Good luck and enjoy.
Regards John

Anything will fly give n enough power
Last edit: 07 Aug 2018 00:54 by one tenor. Reason: correction

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07 Aug 2018 03:37 #6 by Polyphilla
Replied by Polyphilla on topic Electric power for old timer designs
Alan has PM'd me, he's having trouble replying for some reason. I'm looking into it and will sort him out asap.

Pol.

Why struggle for perfection?...just cheat & copy me.:-)

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07 Aug 2018 03:44 #7 by Polyphilla
Replied by Polyphilla on topic Electric power for old timer designs

one tenor wrote: If you go to the RCME Model Flying forum you will see Robot Birds listed as a shopping partner which you just click on. There are also guys on there who will be only too glad to offer advice. Look and see. Good luck and enjoy.
Regards John

Are you secretly a spy sent to poach our members John? :woohoo: ...... well we do have the best I suppose. :lol:

Pol.

Why struggle for perfection?...just cheat & copy me.:-)

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07 Aug 2018 04:42 - 07 Aug 2018 05:01 #8 by one tenor
Replied by one tenor on topic Electric power for old timer designs
Hi Phil I am not prejudiced. I gather info wherever I can LOL Agreed however re being the best [badass] LOL P.S. I wish the new smileys were bigger . In the rack so to speak.:blink:

Anything will fly give n enough power
Last edit: 07 Aug 2018 05:01 by one tenor. Reason: Correction and addition

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07 Aug 2018 11:16 - 07 Aug 2018 11:17 #9 by Quorneng
Replied by Quorneng on topic Electric power for old timer designs
If we assume you are going to fly your planes in a 'vintage' style then as others have said you don't need the ability to squeeze the maximum power to weight from the motor to indulge in 'prop hanging'!
As long as you get a motor of similar kV and Watts it is not going to matter for a vintage design if it is a bit heavier but do remember to include a positive air flow for both the speed controller (ESC) and the motor itself.
For a given level of power electric is more efficient than IC and thus creates less heat however its components, particularly the ESC, cannot tolerate the same temperatures. As heat is dissipated by the square of the temperature difference even the modest amount generated from 'electrics' needs positive attention.

You will also discover just how smooth an electric motor is and how much extra weight has to built into an IC design just to hold the engine down. ;)

A description and pictures of the conversion(s) would be most interesting.
Last edit: 07 Aug 2018 11:17 by Quorneng.

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08 Aug 2018 09:12 #10 by Eric
Replied by Eric on topic Electric power for old timer designs
I'd overlooked the 'vintage style' bit, so 100 Watts per lb is a bit too Over The Top!
Aim for about 75 Watts per.
But, as I've put many times before, if you have too much power, you can throttle back, but if you are at 100%, and need 120% you are stuffed!
[badass]

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09 Aug 2018 04:05 - 09 Aug 2018 04:06 #11 by one tenor
Replied by one tenor on topic Electric power for old timer designs
Can this be worked in reverse i.e. having a motor and designing a model etc to match ?

Anything will fly give n enough power
Last edit: 09 Aug 2018 04:06 by one tenor. Reason: correction

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09 Aug 2018 08:45 #12 by Eric
Replied by Eric on topic Electric power for old timer designs
Of course, but not so easy.

if you are calm and collected when all about you are going berserk - you've missed something important!

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