Will this Outrunner work? (A guide for motor selection)

[JohnRobHolmes]

Whenever I choose a motor for my crawler, I stick to some basic specs. I pm'd this to cartronicshn and figured it would make a good writeup for choosing an outrunner in general. This doesnt apply to any brand, or any style of outrunner. The only assumption I make is that the outrunner is 12 pole stator, 14 magnetic pole. Winding pattern is way beyond the scope of this, so we will also assume that the motor is distributed LRK for sake of argument.

These are my opinions based on experience, trial and error, and preferance. Just because I wont run XXX motor doesnt mean it wont work. I dont like adaptor plates, I dont like 22mm stator diameters. You might have different opinions on these things.... My opinions will probably change over time.

One thing to add: A temp gun is a VERY handy item to have, it allows you to push the voltage and gearing limits of your system without worry of messing things up. Almost all outrunners have a maxx temp of 100C, but I keep the motors under 170F and the controllers under 150F for longevity.



Info that is pertinent of construction: length and diameter of the stator, 22mm diameter is minimum in my book, and thats about the smallest you can find. If the diameter is 22mm, the length should be at least 10mm for a tlt IMO. I find this motor size to be too weak for my tastes. I prefer a 28x10 stator at minimum. How many bearings support the shaft and what size are they? Can I get more bearings if I screw one up? Mounting pattern (spacing and screw size should be 25mm w/ 3mm screws to mount where a standard 540 motor mounts). Output shaft should be 3.17mm to accept normal pinions. KV (rpm per volt) should be around 1000 for a crawler, but your working voltage might change this.


If this doesnt work for you....

The total weight is a big indicator of power. If you dont know any of the other stuff, you will at least know the weight.

Anything under 3 ounces is tiny. TLT's are tiny. Clodbusters use two motors, so you could consider one axle and half the chassis to be pretty light. TLT's and Clodbusters can get away with motors in the 2-3 ounce size range WITH PROPER GEARING. If a high voltage is used, a lower KV motor must be used in a clodbuster or heavy tlt or else overheating will occur. Moab xl's wont treat a sub 3 ounce motor right when it is hot outside. With such large tires I would recommend a larger motor.

Any motor over 3.5 ounces is getting some power under it, but I would still keep these in TLT's. A super sized shafty will want a 5 ounce motor or larger- or else overheating will occur. The fine line is a build like EeePee's txt. Smaller size maxx tires will allow a smaller motor like the Revolver (3.5 ounces), BUT the heat of the motor and voltage must be watched. Too much voltage will cause a burned up motor. If it is a realy hot day, the motor could overheat as well. ANY super class vehicle that is not a clodbuster will need a larger esc such as the mamba maxx.


5 ounce motors and up are the choice for large scale shafty rigs. You can get away with a 28x20 stator pretty well. Even on a very hot day it should not overheat unless you are geared to the moon or using more than 6 cells. If 6 cells is your working voltage, keep the kv around 1000 still. If you plan on using 12 cells all the time, a lower kv such as an 850 or 750 will suite the rig much better. Again, mamba maxx esc or similar is needed for larger rigs such as this. You can get away with a mamba 25 as I did for over a year, but it is riding a VERY fine line of heat.


To rehash in another way, the smaller the motor- the less power it has. This makes overheating more likely because of less surface area. Overheating is really the ONLY worry. Thus, a light rig can take a light motor (or the other way around). I choose 28mm diameter stators because of the extra torque vs a 22mm stator. More torque pulls more amperage, so runtime decreases. If you want to gear very tall (such as a scale rig) a larger-than-needed motor is the best bet. It allows plenty of headroom without overheating. For instance, in a scale tlt that was geared tall, I would choose a 28x16 stator or 30x13 stator. I would not choose a 22mm stator unless it was 25mm long. Microgoat would probably differ on this point, it is just my preference.



That about covers what I use to choose a motor. Pretty much any 12 pole outrunner is universal on these traits.. It is just any other motor, and I know the size and specs. To me it is just like an axiom 55t vs an integy 55t. They both are very similar in size, just a bit different construction.


Hopefully this didnt create more questions, but add em in if you have em!

[EeePee]

Excellent JRH, you're awesome, and very helpful. Thanks for being here and filling us full of information.

I absolutely agree that my 14'r TXT is about the limit with your Revolver, as it performs noticably better in my TLT. So much so, that I'm looking for something more powerful for the TXT.



I'm going to link this in our sticky.

[cartronicshn]

Awesome, a sticky and i get my name on it also

[jason]

I agree with everything you said except this part.

Originally Posted by johnrobholmes

I dont have sex with men.

I've met you, and I'm pretty sure you do.










Just kidding.

I think that when I am ready to go brushless, instead of trying to figure out all this mumbo jumbo, I'll just call Holmes Hobbies and tell them to send me the good chit.

[JohnRobHolmes]

Added a bit about temp guns to post #one. If you want to push your system performance, they are a needed item. If you want to test a new motor/ vehicle/ voltage setup that hasnt been tried before, they are needed.

[JohnRobHolmes]

Originally Posted by jason

I think that when I am ready to go brushless, instead of trying to figure out all this mumbo jumbo, I'll just call Holmes Hobbies and tell them to send me the good chit.

Thats why I do what I do I have fun with this stuff! I am also a power:weight ratio junky. Who wants a full horsepower of torque based power without adding an ounce of weight? I DO!!!! Brushless is where it is at.


I forgot to add one little detail. Holmes Hobbies is not resposible for how you use this info, and how many parts you break 'cause your trigger finger is too heavy

[syco133]

Awsome write up man you are the all knowing brushless god I know you made my life a hell of alot eaiser when I searched all your outrunner posts. Thanks a chit load.

[wyattburp]

I've only have experience with Park 400 motors, which require an adapter. I would love to see a list of outrunners that don't require any sort of adapter to mount...

It would be cool to tally a running list of commonly used outrunners that people here have experience with. Things like if they require an adapter or not, weight, measurements, etc. A nice chart for comparisons sake...? It would be a great reference guide, for me at least (and other noobs).

[JohnRobHolmes]

This here is the thread then. Feel free to post up your comments on whatever motor you run. It will only add more specific info for this guide.

The only motor that I know of that bolts up AND has 1/8th inch shaft is the Revolver and http://www.flyware.de/flyware-deutsc...00_deutsch.pdf that Eggressor pointed out. The hyperion motors I have on order will require me to turn down each shaft, but after that will bolt up.

That is basically the list right there. Not alot out there for us crawlers unless you are willing to do some work!! That is nothing new for crawlers though.

[Cloak]

Originally Posted by johnrobholmes

I forgot to add one little detail. Holmes Hobbies is not resposible for how you use this info, and how many parts you break 'cause your trigger finger is too heavy

Hey now, that's DJ's version of the story. He neglected to mention that what actually happened is my rear axle got locked up because of the locknut managed to clamp down on one side. Sure, I could have let up, but I really wanted to get over that rock.

[Tzi]

I am noticing a lot of brushless motors on ebay now, and because the outrunners arent commonly used for cars yet, i'm having trouble working out what is right and what isnt.
Firstly... what size rig would this work in.. if at all?
http://cgi.ebay.com.au/ws/eBayISAPI....8796&rd=1&rd=1

and secondly...
what does the Watt rating mean other than how much juice they suck?

e.g.
this 580rpm/v motor reads 600W with a "pull" of 1500g
http://cgi.ebay.com.au/ws/eBayISAPI....8789&rd=1&rd=1

this 800rpm/v motor also reads 600W but only a "pull" of 600g
http://cgi.ebay.com.au/ws/eBayISAPI....0474&rd=1&rd=1

and this 700rpm/v motor reads only 300W but has a "pull" of 900g!
http://cgi.ebay.com.au/ws/eBayISAPI....7214&rd=1&rd=1



Can you help explain this please? :-(

[JohnRobHolmes]

The only specs I would trust on those motors is the weight. The first motor is Just a bit over 2 ounces. It is small, and wont work for anything but a small tlt build. I do not trust many of the other specs. Efficiency, wattage, io, and current are kinda a moot point when the specs claim 98% efficeincy. That is simply not possible with any motor, period. Io will be faked to reach the insane eff numbers, and the wattage depends on the true eff numbers and heat dissapation ability. A small motor like that can only get rid of so much heat.

For the money it couldnt hurt to try on a small rig. The ESC will be useless for ground use. You will need to fab an adaptor plate, it probably uses 16mm or 19mm mount spacing and a standard RC motor is 25mm spacing.


The second motor is a big one. uses a 5mm shaft and will bolt up otherwise. You will need a pinion drilled or made to fit 5mm shafts.

[nitromtcrawler]

that was a great write up.but i was left with a couple of ??.im looking to buy a revolver2. and i was wondering if it would be enough for my comp rig. i dont know how much it wheights.it is sort of a bmvII but it works different and the rods are not steel they are graphite. im curently runing 6cell 1500mah ni-cd they weight a ton and i hate them.:-( . i know ill have to change to a better pack but i also dont know what??? So my main ? is will the revolver2 be big enough for my rig??? thanks.

[JohnRobHolmes]

geared very low it is enough for some people. I would get the hyperion z3013 for a comp rig though. Better to have more power when needed, than not enough sometimes.

For the batteries, IB1200, IB1400, Elite 1500, or 4/5A size cells are the way to go.

[TLTCrawlin]

I am going to start saving for a BL, a mamba 25/hyperion setup, can I run 9 cells without problems. And the mamba is 6-9cell limit, with a 5v/1.5amp bec right?

[JohnRobHolmes]

The mamba 25 can actually handle more voltage than that, but it will start to get hot. On 9 cells it might thermal (with that motor) when you are pushing it hard. You are correct on the BEC.

[DKNguyen]

I've heard people say one motor trucks have longer battery life than 2 motor trucks. But wouldn't two motors just require you to be lighter on the throttle to get the same amount of power? Resulting in approximately equal run times?

(Thinking of two Z3025-12 on a Clod, not really to put out max torque together, but more so that neither front or rear will ever stall, and maybe to zoom up smooth slopes).

[JohnRobHolmes]

One motor trucks would give you longer runtimes, mostly because the average person uses as much power as they can. Yes, with dual motors you can be easier on the throttle. Will you be? Probably not.

[DKNguyen]

Originally Posted by johnrobholmes

One motor trucks would give you longer runtimes, mostly because the average person uses as much power as they can. Yes, with dual motors you can be easier on the throttle. Will you be? Probably not.

Good thing then that software drives mine rather than me ;)

THen there's always the issue of how it lasted half as long, but maybe it covered the same distance 2x as fast as someone with a single motor.

[TheWiking]

I'm still kinda lost in this brushless world... Hope you guys can help me out.
I'm gonna build a scale-ish rig with a 1:6 Hummer body on it.:-P
I've ordered a R2 tranny and some punisher shafts from RC4WD, and a set of Mad Force axles from RCP Crawlers. I have lots of 3000Mah NiMh 6 cell (sub C) battery packs already for my Stampede with an old Hacker Brushless system (B508s and Master ESC), so that's my source of juice. This rig will be pretty heavy, in the 8 pounds plus range, and with a wheelbase of about 18 inches...

What motor and what ESC would you recommend for making this thing a powerfull crawler?? I'm not looking for speed, just awesome "crawlability" (is that a word??)

Regards
Roy from Norway