Offered for your review:

When I first started working on the Brodak Electric Power Systems I was following the List Your Set-up thread and what ever other sources of information I could find on motors.  I got frustrated that the motor companies used different methods for presenting the size of their motors: some used internal dimensions, some used external dimensions, and one company even used external diameter and internal magnet length! Thus I started a chart that sought to show the external and internal dimensions of motors as published, measured or as best could be determined.

I have been told by experts like Dean Pappas & Keith Shaw that one of the most dependable measures of motor power potential is simply the weight.  Almost all outrunners share the same basic structural design. The weight is mostly caused by the amount of iron and copper in the motor. This is a good sanity check from brand to brand and also a good indicator if you are comparing say a 28mm diameter motor to the equivalent size of a 35mm motor.

Not very many motors provide information on the bearing dimensions.  However they do show motor shaft diameters - this provides some clues on bearings sizes and (I think) on the stiffness of the motor. 

Also started picking up on the KV ratings available for each size.  Some brands offer several kv's some offered only one.  Over the past several months several of the "big" companies have also started pushing the motors as intended to replace a certain IC equivalent - those ratings have proven to be completely bogus, but if you get into the physical dimensions then more meaningful comparisons can be made.  Also, if you are looking for a particular size motor with a particular kv rating there are cases were "Brand X" might not have it but "Brand Y" does.

The list is fairly comprehensive at two pages but I am sure there are a lot of brands I have missed.  Conspicuous by their absence are the Hacker, MVVS, and Plettenberg motors - simply put I could never find any meaningful dimensional data on them that would align their sizes in a manner consistent with the other motors.  If you have/find that info I hope you chart it and share it.

With the ongoing discussions about motor sizes, I hope this chart is of some value while comparing and selecting your motor.

Dennis

Great mtr. cross reference.  Thanks for sharing ! 

Dan

the weights on the E-10 and E-25 don't look right. The E-flite book that I have list the following

E-10        1100 KV       4.30 ounces
E-25        879 KV        6.70 ounces
E-25        1250 KV      6.40 ounces

The 1250 KV rated E-25 is intended for pylon racing and they claim that version will produce 850 Watts while the 870 KV version only puts out 600 Watts.

Fred C.

Higher KV ratings of the same size motor usually have fewer winds and slightly less copper in them so they will weigh less - though the motor makers rarely call out unique weights for each kv offered.


I am coming to believe that the watt ratings of electric motors is like the HP ratings for IC engines - ie the info is of no value whatever.  I think the reason is that we do not run at anything like the rated settings.  In reality if you were to use the EF25-1250 you would use 3S (to get a reasonable throttle setting and governor performance) or the EF25-870 with 4S for the same reason.  Assuming same prop and same RPM the ouput power would be pretty close to EXACTLY the same.

BTW, the EF-1 Pylon racers are cranking around 15K with an 8x8 prop.  That ought to make a pretty interesting e-combat model...

I Agree the Watts are almost meaningless, we ran a test one time with a AXI motor, 3 different props and 2 different batteries (3S and 4S). We got Watt meter readings all over the map.

I just noticed that two of the motors had the wrong weight of the motor itself. That chart is very useful, I have been flying with the E-10, E-32 and the E-60.  The E-10 is on a Great Planes spitfire at 3lbs, the E-32 is on the Great Planes RV-4 kit (6.5 lbs) and the E-60 is on a scratch built camera plane at 11.25 lbs.

I like the E-Flite motors for CL scale, although I was hoping the E-10 would fly the spitfire with more authority, the spitfire really needs the E-15 or E-25 to fly with authority.

Fred C.

Dan - hey a little full contact combat ought to be - uh entertaining AND expensive!

Fred  - Hopefully the E-15 will nestle in without too much drama.  If not try the same length motor in a larger diameter.

Paul - Several - but not ALL - of the posted specs said weights did not include connctors or some other hardware.  Also motors like the Arrowind use 4mm instead of 3.5mm connectors - more brass!  Glad the E-32 is working out, it sounds like it ought to be a good choice among the slightly larger motors (versus the 2826's & the like).

Dennis

Then fire extinguishers will become standard equipment for the pit crews. 

I was thinking graham crackers, marsmallows, and a couple squares of chocolate....    

I am going to try the E-25 on the Spitfire. Since I have a temporary mount that will adjust for length I can put the E-25 on with no troubles. The E-25 will probably be too much power, but we will see when it arrives in the mail.

I flew the RV-4 yesterday and the E-32 flew the 6.5 lb RV-4 fantastic for CL scale. I am now up to three models with electric power and will be bringing two more on line this winter with electric power.

Thanks again for the chart I need to print it out and look thru it carefully.

Land softly,
Fred C.

What's the motor weight of a motor equivalent to a Fox 35?


MM

A Fox 35 turns a 10x6 prop.  Similar outrunners are in the 4-4.5 oz range.  (Elfite E-15, various 2815 (internal dimensions) or 35-36 (external dimensions)