Brushed and Brushless Confusion

[Dave Wilson]

Hi guys & Gals
Very new to RC Flight (see profile) but since taking up the hobby late last year I have almost??? finnished one projecet and started another whilst waiting for parts for the first.
My biggest headach (besides spelling lol) is understanding electric motors?????
I understand, just about, brushed motors... 400, 480, 600 etc. I found that I needed x2 600's (brushed) for the P38 I have almost finnished. BUT!!! for my next project, a DH Mosquito, I would like electic motors that are a bit more up to date and a lot lighter...... Brusless motors
Can anyone advise an inexpensive Brushless alternative to the x2 400 brushed motors suggested in the plan I am building the Mozzy from.
Any help would be very much appreciated.
Thanks in advance
Dave.

[Tim Mackey]

loads of stuff about, from cheap and cheerful outrunners on Ebay, or try some of the specialists like
Overlander ( sorry....Over-tec )- http://www.overlander.co.uk/products/default.asp?cid=51&scid=82&pid=996
Puffin-http://www.puffinmodels.com/kontronik.html
BRC hobbies -http://www.brchobbies.com/?page=shop&action=additem&item=233
Robot birds - http://robotbirds.com/catalog/product_info.php?products_id=1430

[Dave Wilson]

Hi Timbo
just had a quick look at the sites you suggested... especialy brchobbies and robotbirds. They look like they will do the job. The plan gives the span (43") but not weight. If only these websites would give some idea of what size brushless motors would be suitable for what size/weight of plane... it would help out us newbies no end :-).
Many thanks for shedding a little more light on the subject anyway
I'll have a good look at them in the morning

Thanks
Dave

[Tim Mackey]

Glad it helped alittle. There is still a LONG way to go with regard to simplifying the black art of electric flight, especially brushless inrunner /outrunner etc. One or two manufacturers are trying, but with everyone of them using a different system of number /letter code to "identify" the motors, it is bloomin hard going ! A couple of "generalisations for you....might help a little further :-)
1) INrunners generally are faster revving, but have less torque than OUTrunners, and suit smaller faster revving props and planes, as well as EDF (electric ducted fans)
2) OUTrunners - think of these as the fourstrokes of the electric world - slower, and swing bigger props, bit like an "ordinary" electric motor fitted with a gearbox.
3) A useful figure ( IF SUPPLIED WITH THE MOTOR SPECS )is KV. This is the revs per minute of the motor for every volt of battery supply. IE 2500KV motor, run on a 10v battery would give you 25000 rpm. This obviously depends on the prop size fitted.
4) Watts per Lb. Motors are increasingly rated by their wattage, and you need to aim for around 100 Watts per pound for anything decent in terms of power to weight ratios.
As stated, this is very much a generalisation, and there are several examples of breaking the norm !
EG it is becoming more common lately to see OUTrunners used in EDF, the wind count on the motor is pretty much what effects the KV, and a lower wind gives more revs. Outrunners are generally a bit easier to produce, so this is resulting in in increase of the amount available, and steadily lowering prices.
FINALLY....I, and many others I am sure, can wholly recommend John Emms at Puffin Models to give you the best advice to ensure you purchase the right setup for any type of model. Get it wrong, and at the least you end up with a redundant powertrain for chosen model. At the worst....it wont fly, or releases the magic smoke !!
PS Brian Collins (BRC hobbies )is himself disabled in a wheelchair, and is an excellent example of what can be achieved, a very nice bloke, and knowledgeable too :-)
PPS dont forget to allow for 2 X speed controllers on your Mossy, as brushless motors will need one each. You cant just join 'em up in parallel like brushed can motors. Because they aare effectively A/C motors, and need the ESC to deliver timed power, and each motor may have slightly different timing /performance. Also ( God -this is turning out a marathon :-) ) you should be aware that some of the really cheap ESCs are pretty naff, they may well work, but are notorious for causing electrcal noise - glitching etc.
YOU HAVE BEEN WARNED.
IF the budget can stand it, you cant go far wrong with JETI Escs. Simply the best I have ever used, but pricey.

[Dave Wilson]

Again, Many thanks for the fantastic info you have provided. I now understand a little more about how to work out what I would need for my projects. I have yet to get my first project off the ground (52" P38)I am using x2 600 brush motors in it and when ground tested it wanted to go! A bit of an advanced project for a novice you may say but it has kept me happy and occupied for the past couple of months. If it DOES fly, it's a feather in my cap, if not, the experiance I have gaind from building it has been worth it (and kept me from going brain dead :-) ) Budget is very tight but I think from the money I save Making my own cockpit canopies from clear sheets of laminate, empty plastic milk bottles for engin cowles, "Y" leads from old computer wires (same rating & connectors as genuine y leads) and making my own pilots from foam would just about get me a couple of brushless and ESC's. (It also helpes now that I have dicovered the combination coad to my wifes purse) I only found this site yesterday after reading the mag and allready I have gained a wealth of knowlage, thanks to yourself and the site. I will be putting a few pics up of the P38 later, you are permitted to have a good giggle at the home made pilot :-)
Cheers Timbo you have been a great help

[Tim Mackey]

Thats great Dave glad to have helped, feel free to email me if you want, much easier to communicate that way, and send photos and stuff. Looking forward to seeing the P38, and I doubt if anyone will actually laugh, besides....
WITH NO BLOOMIN SMILIES YET AVAILABLE you wouldnt even know if they did :-)

[nasa_steve]

hi dave
i have to ask are you a complete novice with rc flight or have you already completed some training
regards
nasa

[Dave Wilson]

Timbo... pics coming next few days... watch yer ribs ;-)
Nasa Steve.... I'm genuinly total novice, daughter got me an artf foam mustang sept last year. Clocked up loads of fun hours on PC flight sim but never actualy flown RC or built any till now.

[nasa_steve]

if you want my advice i would not even consider trying to fly the P38 or the Mosquito until you are confident with a trainer. you will only end up with a binbag full of balsa if you do.
do you belong to a club and are you a member of the BMFA are the next questions
regards
nasa

[Dave Wilson]

sound advice Steve...Just gaining experiance with the mustang at the momemt whenever I can get out with it. The p38 needs a few more weeks work on it before I even concider letting an experianced person fly it an the mossy is only in the beginning stages of the body.
Unfortunatly I am unable to get to my local Flying Club (Rochdale Lancs) and as yet I am not a member of BMFA. I am just getting satisfaction and pleasure out of building for the moment..... and crashlanding the mustang, have a production line of new nose cones going for it :-)

[Tim Mackey]

One prob with not being a club member is
are you insured to fly R/C ??

[nasa_steve]

i would invest in a bmfa membership (or insurance)if you don't do anything else. if only for the insurance side of things. because if god forbid you hit someone or damaged property etc whilst out flying without insurance you would not have a leg to stand on and you would be subject to the ANO (air navigation order) which is law in this country. it could prove very expensive if you were prosecuted with it.
regards
nasa

[Bladerunner]

As Timbo says, make sure you understand the power-to-weight requirement for your model. That can be awkward if they don't tell you what it needs to be - so I'd suggest the following approximations when unsure:

1.)
Scale&Sport = 150-200 Watts per kilogram

2.)
Performance (fun-fly / aerobatic) = 200-250Watts per kilogram or better.

For two motors, divide the power requirement between them.

Invest in a good power-meter so that you can measure the power your system consumes - make sure it's within the electrical limits. Many folks smoke their systems because they can't see they are overloading(often caused by over-propping the motor, or under-specing the battery). Make sure that the motor, ESC and batteries are properly cooled by flowing air - they do get pretty warm. A basic rule: if you can't touch-and-hold, then it's too hot.

There are now many brands that offer good value. Hyperion make good products at a reasonable price - you can get everything you need from that one brand.

[Dave Wilson]

Thanks everyone for all the advice and help so far. All have been very helpfull, Informative and boosted my confidence in taking up the hobby more seriously. i have robed the wifes purse for the £27 Family Membership fee for BMFA (NOBODY say a word to her lol)and posted it this morning.
For those who want a giggle, I have just posted some pics of the P38 I am building.It's my own version of it as the plans I got off ebay... well, say no more about them. Thanks again everyone

[Tim Mackey]

WELL DONE DAVE - A SOUND MOVE.
I will send her an email thanking her for the order just placed on my website for the "massage tool" :)
Off to laugh at - sorry admire the piccies now :-)

[TerenceA]

A very interesting and informative thread. Although an experienced modeller but new to electric flight, (after a break of some 30 years) can someone explain what the terms "inrunner" and "outrunner" refer to?

Dave, have you actually flown a model yet?

[Bladerunner]

Hi Terence

Inrunner refers to the classic motor configuration where the rotor is enfolded by the stator. In other words, its that internal center bit that spins.
An outrunner is the exactly the opposite.

Inrunners are good for high rpm(low number of slots/pole-pairs), low-torque applications such as ducted-fans. Outrunners are better at lower rpm(high number of slots/pole-pairs), high torque applications such as 3D.
It should be noted that the majority of sport flyers prefer outrunners because they work on standard prop sizes without requiring a reduction gearbox. This saves weight and complexity.

There is more to it than that, but these are the basics.

[Tim Mackey]

A good expalnation Blade....
Another "rule of thumb only" comparison is to think about the outrunner as a 4T and the inrunner as 2 stroke.
That said, outrunners are generally easier to produce, and many self assembly kits of outrrunner motors are available -this makes them cheaper overall, and therefore perhaps gaining in popularity. A correctly wound outrunner can perform as well as an inrunner -EG can be made to rev very high, even driving EDF planes these days ( Electric Ducted fans )at VERY high RPM - 50000 rpm is not uncommon.

[Ian Muir]

Hi Enjoying threads and getting plenty of input, am trying out cheap poly ready copters and planes and intend to build 2D (flat) planes and reuse the salvaged items from the shop bought poly types.
It would be easier if there was a sliding scale of motor to plane weight/type of use/span to give an idea of what to look for in estimating parts needed to carry out a project. ian

[nasa_steve]

ian
there is no way to really do that there are so many factors to take into consideration. the general rule of thumb i work on is 150watts per lb will fly reasonably well. but if you want out and out ic stomping performance then 200-250+ watts per lb will do what you want.
also to bear in mind 1hp is 748watts so its easy to work from that
regards
nasa

[TerenceA]

Thanks guys, its so simple when it's explained!