Conversion to Electric

[JayCee]

Hi

 

I would like to know if it is possible to convert my IC Kyosho Calmato Trainer 40 to Electric.

 

I have only just started flying Electric with the new Wot 4 Foam-e and the ST models MX2. With winter round the corner it would be nice to go to the site with just the aircraft and a few batteries in my pocket , much less hassle.

 

I have read a few articles but still not sure on calculating motor, ESC, and battery and prop sizes.

 

I read somewhere 100watts per lb in weight! but is the the airframe weight or including battery motor etc.? and if I don't know the battery size yet how can I calculate the weight......as you can see I'm at the beginning of a steep learning curve!

 

Any help would be appreciated or pointers to publications

 

Thanks

 

JC

 

 

[ken anderson.]

hello jaycee....tim is the boy for this question............you are right in saying 100watts per lb...and again it's the airframe weight you need to know..........so 5lb plane =500 watt motor......there are a few models that have been convereted from ic to elec and vice versa....

 

  ken anderson..ne...1.

[JayCee]

Thanks Ken

 

Will Tim pick this up I should I re-post? if so where?

 

Thanks

JC

[ken anderson.]

no dont re post-timbo will be along shortly.....he'll give you the finer point's......

 

            ken anderson...ne..1.

[Ultymate]

I think Tim's away for the weekend at the Lleyn bring and fly event near Pwllheli so you may not hear from him till after the weekend.

[Steve Hargreaves - Moderator]

Check out Timbos article in the RCM&E Special...an excellent article covering conversion of a 46 size model to electric.....

 

I'm sure Timbo will be along with some specifics but as Ken says 100watts per lb is the number to aim at. The weight is the total ready to fly weight for which the current weight of your trainer with ic motor will be a good guide so stick it on the scales & multiply the weight in lbs x 100. This is the number to aim at. I would guess we'll be looking for around 500watts as Ken has mentioned.

 

On a 3S battery (approx 10volts under load) this would equate to about 50A current which is getting a bit high....far better to increase the voltage to a 4S battery (about 13.5volts under load) which gives us around 37Amps which is much more manageable

 

So already we can see that we need a motor & ESC capable of about 40Amps (personally I would go a bit higher...say a 50Amp ESC & a 45Amp motor. We can also deduce our battery size.....we really don't want to run at much more than 10C if we can help it so 10 x capacity of battery should equal max current (37A) therefore we need a 3.7Ah battery or more commonly a 3700mAh battery.....this would give us 6 minutes of flat out flight or about 10 minutes of general use.....if you want more then a larger battery should be considered...maybe a 4200mAh.

 

So we're pretty much there....a 45A motor, a 45-50A ESC & a 3700mAh 4S battery...last & probably most important is the kv of the motor...this is the rpm it will spin for every volt applied & this really comes from experience......I would say (& open to correction here) that something around the 6-700 mark would allow for a 11" propeller which should suit nicely.

 

Final point...when its all together beg, borrow, steal or even buy a wattmeter to check everything is running within its maximum capability.....failure to do so will release the magic smoke & hurt your wallet!!

 

As I say I'm sure Headmaster Tim  will be along to check my work (& probably give me detention ) & I'm sure he will offer some specifics......can I also respectfully suggest you read some of the other threads in the new to electric section.....there are some excellent threads in there.....

[ken anderson.]

a gold star for steve...go to the top of the class.....that's about it JC........go spend some dosh and let other's know how you get on.......

 

 ken anderson..ne..1..

[Richard Wood]

There's just one other thing worth pointing out JC when you mention

flying electric over winter & that is that batteries do not perform as well

in the cold, often significantly so.

Take a look at this thread:

Cold batteries

I'll echo Steve's recommendation (order!) to use a Wattmeter - essential.

Don't forget to read Timbo's article in the latest mag & let us know

how it goes.

 

 

 

 

[JayCee]

Thanks Steve, Richard and Ken

 

My copy of RCME has just dropped through the letter box!! So I will have a good read.

 

Just one final (ish) question if I use a 4S battery does that mean I have to have a separate battery for the RX + Servo supply?

 

JC

[Richard Wood]

Good question JC  - yes & no!

If you use an ESC with a switching BEC you don't need a seperate Rx bat.

with up to 4 analog servos.The BEC should be rated at around 3A at 5V.

If you use an OPTO ESC or an ESC with a linear BEC you will need

a seperate RX pack in your case!

The article in the mag will answer this better!

 

 

Edited By Richard Wood on 24/09/2010 12:07:16

[JayCee]

Thanks

 

Should have got reading first now where were those scales!!

 

JC

[Steve Hargreaves - Moderator]

Yeah its a good point JC...I should have mentioned it  but certainly consider the power supply to the Rx......probably the easiest is to use your existing battery that you use to power the radio now in the ic powered model. Or you could look at sourcing a UBEC to power the radio independant of the BEC on the ESC.....

 

If you do this then you must disconnect the RED wire from the ESC plug into the Rx (assuming you don't use an Opto ESC) & don't forget to charge this battery before flying...seperate Rx batteries in electric aircraft are easy to overlook & forget..

 

Keep reading & posting back if unsure & remember...the only daft questions are the ones you DON'T ask.....

 

Oh & try Giantcod for your motor/ESC/Battery/Charger etc etc etc..... excellent prices & service....

 

If I get time I'll try & look up some suitable bits for you later....

[JayCee]

Thanks Steve great help

 

Think I might keep my original Rx battery pack so long as the extra weight isn't a problem.

 

Nice little project for these 'No Fly Days'! thanks for all your help very much appreciated!

 

JC

[Steve Hargreaves - Moderator]

Possible motor here or here (extra peer review needed here....these motors might be a touch on the small side so I'll defer to anyone with greater knowledge)

 

Possible 50A ESC here or here note the BRC one is an Opto unit so would need an additional power supply for the Rx as discussed

 

Possible 4S Lipo here or here

 

Gives a good idea of costs if nothing else.......

 

Wattmeter here 

 

Or you could try Hobbyking Amazing choice & prices but you are buying from China....I've never had a problem but some folks don't like it!!!

 

The key with electric set ups it to buy bits bigger than you actually need.....then, if you have insufficient power, you can increase the prop size & access the extra power. Usual caveats about not going too over the top...buying a 1000watt set up & only propping it for 250watts would be just plain silly!!!

[JayCee]

Thanks Steve your a star!

 

Blimey, 4000mah lipo 5c charge rate......better get a new charger!

 

Plenty of home work to do before I start the serious stuff.

 

JC

 

 

[Steve Hargreaves - Moderator]

Well....you don't NEED to charge it at 5C!!!!

 

But yes thats about 300watts you would need...a very serious charger indeed!!!

[Simon K 3]

Charging at 5c (if you have a suitable charger) is possible, but is likely to do nothing for your battery life. In reality charging at 0.5c or 1c will be sufficient. It'll allow you to recover from the last flight, have a chat or watch someone else fly... and be far kinder to your batteries.

Converting most things to electric is possible given a bit of time, thought and research.

I'm currently flying a YT International SBach 50cc converted to 12s and a fellow club mate has one of the 40% Extreme Flight Extras running on 14s!

Edited By Simon K 3 on 24/09/2010 18:08:21

[Danny Fenton]

I will back you on the the 4250 Steve, Not run one personally but the size is about right. Of course if you are starting afresh you could go A123. They don't seem to mind the cold so much and can be left tucked up warm and snug in the model while charging  

Cheers

Danny

[Tim Mackey]

Trust Danny to "get a plug in" for the A123s  - LOL.

Been away for 4 days flying the Lleyn do - so sorry for not responding sooner JayCee.

Having just ploughed through around 1200 emails, I am just about up to speed with forum things. Seems you have received some great advice already, so perhaps coupled with the piece in the special edition mag - youre sorted?

Hope so, but of course, post away with any further questions.

[JayCee]

Thanks Tim

 

Great article, and lots of help from the forum as you say.

 

The project is on the back burner as the weather is still 'A- OK'  for flying.

 

Will sort out a short list for the motor, ESC, and battery over the next couple of weeks based on your article and the help from all the guys in the forum, will run the list past you if that's OK before parting with my hard earned cash.

 

Regards

 

JC

[Steve Hargreaves - Moderator]

It all starts with the weight so get those scales out!!!

[nasa_steve]

Personally I would fit an Eflite 46 on either 4 or 5s it depends what you'd like to do after the trainer but that setup will work coupled to a 60amp esc and you'd be in business. Nasa

[JayCee]

OK Steve/Timbo and all you electric buffs!

 

The weight of my Calmato HW trainer is 5lb 9oz (same plane as in my ID picture!)

 

Thinking, rightly or wrongly, that a bit bigger is better than a bit smaller I was thinking something about 600 watts.

 

Not wanting to throw to much 'hard earned' on this first conversion project I found this http://cgi.ebay.co.uk/TURNIGY-SK35-42-KV1000-605W-BRUSHLESS-OUTRUNNER-MOTOR-/260655405082?pt=UK_ToysGames_RadioControlled_JN&hash=item3cb045d81a on good old e-bay only £20.00 + p&P. What are your thoughts?

 

Now I get a bit lost, reading Timbo's article in RCME he starts from prop size, I certainly like the idea of a slower revving motor with a larger prop on a trainer...as you can see I need help!

 

I assume the Lipo will be a 4s around 3200mah and the ESC around 45amp, once I have the components clear I can start to work out the logistics.

 

I don't want to have to remove the wing to change batteries, once I know the battery size/weight I can find the CG and hopefully be able to cut a battery access between the firewall and LFE of wing above the existing fuel tank position.

 

Thank for all your help.........Oh any suggestions on a reasonable Watt meter?

Regards

 

JC

 

[Richard Wood]

Hi JayCee,

600W will be adequate for a trainer.

The kV of that motor is a bit on the high side for a 4S & would

probably limit you to a 10" prop. to keep current manageable.

Something around 900kV on a 4S would be better & would allow

an 11" prop. without current draw being excessive.

A trike u/c model like yours will probably have a 11" prop limit

for ground clearance as well.

Follow Steve's link to Giantcod for  XYH or Emax motor and an ESC,

and a Wattmeter from BRC.

I'd go for a 60A ESC as they're not much dearer but will give you

a wide safety margin & will not get as hot.

 

Cheers

 

PS 

The Emax motor I use in a Scorpion (40 size low winger) would

suit you perfectly but it's out of stock at GCod .

This would be suitable:

Emax motor

 

Edited By Richard Wood on 28/09/2010 10:34:27

[Steve Hargreaves - Moderator]

Richard makes a good point about ground clearance.....what is the max sized prop ypou can fit & then work back from there. Certainly with a 4S set up on this motor I think you would be limited to a 10" prop...possibly 11". This might be all that the ground clearance will allow so we can work around that. Let us know what fits....prop selection is absolutely crucial in electric set ups & we don't want to find that the optimum prop is a 12" prop when you can only fit an 11"......size really does matter in this instance...

 

I do like the Turnigy motors (see here for link to same motor at HK) but I think 600watts is pushing it a bit for this motor. The reviews are slightly mixed with some early ones saying its not very good & later ones giving the thumbs up...this is often the pattern with Chinese goods...they seem to learn from their mistakes & quietly improve things.....not that they would ever admit to a mistake..oh no...loss of face & all that!!

 

Agree with Richard about the 60A ESC too.....

 

The wattmeter at BRC is about as cheap as you will find.....