Pmax 520kv

At ø58 x 58mm long, this massive motor is expressly configured with a ø6 x 42mm long motor shaft (ø10mm internal) for 600/700-class model helicopters and thus, isn't supplied with a fixed-wing prop-adapter or mounting hardware. That said, these accessories are readily available, and this motor is fantastic for airplane-use as well.

Unlike motors where a button-pusher monitors an automated winding machine loaded with multi-strand wire, this one is hand-wound with a single-strand (7-turns) of ø1.36mm wire. This requires special tools and a skilled craftsman, effectively making it a custom motor. Since winding the 12-tooth stator by hand is finicky and time consuming work, this is a limited production item so please call for availability.

Packing the stator poles with thick wire is what gives this motor the ability to handle a lot of current - e.g. perform a lot of work. After all, the sole reason for using a single-strand is achieving maximum performance. Anyway, depending on the battery pack, this motor is well suited for scale, sport, hot-sport, and extreme-3D maneuvers.

At 505g and capable of outputting 4500W (about 6.03 hp), what results is sufficient power reserve for pretty much any maneuver you can imagine. By way of comparison, an OS MAX 1.05HZ-R engine on 30% nitro makes about 3.75 hp. However, it weighs 596g and costs $530 (plus another $230 for the 185g muffler).

Finally, a suitable ESC (electronic speed control) will typically be of 120-200A capability, and due to the high specific power output, you'd be well advised to lubricate the bearings (a wear item not covered by warranty) each time you go to the flying field (a needle oiler makes this quite easy - these are readily available at hobby shops that cater to RC cars and trucks).

• Winding Scheme = dLRK
• Poles = 10
• Magnets = 12
• Winding = Delta
• Wire = ø1.36mm
• Operating temperature = <260°F
• Maximum temperature = <350°F
• Bearings = Two 10x19x4mm supporting shaft

Note: The motor is tapped for four M4x0.7 bolts on a 30mm mounting pattern. Ensure you select the proper length bolt such that they don't protrude beyond the stator and into the windings because this may damage them. Also, due to the high specific power output, you'd be well advised to lubricate the bearings each time you go to the flying field because bearings are a wear item, e.g. not covered by warranty. A needle oiler makes accomplishing this quite easy (they're readily available at hobby shops catering to RC cars and trucks for the same reason . . . motor bearings 'must' be routinely lubricated or they won't last).

Further thoughts:

How much prop or load can you put on it? 250°F is a good safe number. This is fairly easy to avoid and only requires a temperature gun and a wattmeter. How? Simple, first confirm the current draw is not exceeding the capability of the controller with the selected prop under static conditions. Remember, the electric-motor/prop does not unload the same way an IC-engine does in the air so this will be good data for your use. At the same time, measure rotor temperatures (what's spinning and holds the magnets in place) and record every 30-seconds or so, and monitor continuously if they approach limits mentioned above.

That said, while conventional hobby-grade epoxy is often quite stable to 185°C, call it 365°F, high-temperature 2-part epoxies like we use to secure magnets to the rotor shell are often rated to 260°C (~500°F) and one-part silicone based adhesives are rated higher, in the vicinity of 300°C, or 572°F but our advice is to consider reducing the load when temps are in the vicinity of considerably less to provide overhead. Yes, this is a judgement call but guessing wrong can cost you a motor and one where the magnets have come loose is indicative of running too hot and not covered by warranty.

So in general, a motor coming down at 300°F is pretty damned hot in our view and you'd be wise in looking at reducing prop pitch or diameter to get it into the 250°F range. And no, these temps are not too hot or mean the motor will melt. Remember, conventional solder is used in the range of 625° and lead-free (what is used pretty much exclusively these days) melts in the 675°F range. So obviously, the motor has to get to those kinds of temperatures for the solder to let go.

The real danger is the coating use to enamel the wire for the windings as 250°C is widely recognized as a limit, and while that's approaching 500°F and seemingly plenty far form the danger zone, remember these motors are wound by hand and as the wire bends stresses are imposed on the wire strand so why risk shorting it due to overloading? Finally, for a magnet to come loose means the stator saw sustained temperatures that would qualify as . . . hot as hell.

Bottom line? Simple and widely available tools like an off the shelf infrared temperature gun and wattmeter - both - cost less than $100 and are all the tools you need to get a sense of what's going on. Take care of your motor, oil the bearings occasionally and this unit will deliver years and years of service.

Too Long; Didn't Read (TL;DR)

This is a seriously good motor because it makes monster power, has huge bearings, and is hand wound with a single strand of wire. It's called a Pmax because it's the maximum diameter motor, which you can comfortably stuff into the the side frames of a Pantera P6. However, it works pretty darn good with a lot of 700-800 class helicopters plus fixed wing models (but you have to source your own prop adapter, which is easy enough).

Background:

Physically imposing and larger than the usual 4035-type motor, we've found it's nearly Ideal when matched to the Pantera airframe by dint of it's versatility. Especially when dynamically loaded with the Quattro rotor head (4-blades) equipped with two sets of 700s because it has gobs of torque. Moreover, if you subsequently mount the mechanics within a scale fuselage, then you have the makings of a superb scale machine (or leave it pod-n-boom for a hooligan's dream).

- A tight fit, at 58mm this is the maximum diameter motor that fits Pantera side frames

Available in a range of Kv (450, 520, 630, and 720) this is our top-of-the-range motor. We hope you delight in using it as much as we do because within limits, it can almost be thought of as dial-a-motor. For example, in a helicopter, once you select the basic rotor-head RPM-range you desire, you can dial the power up or down via the cell count and thus, totally change its personality. Dealing with just one variable is nice! Anyway, here are some rule of thumb figures for main rotor RPMs.

• 8S ~1300 RPM (scale use, 2 or 4-blade head)
• 10S ~1650-1925 RPM (sport, mild-3D)
• 12S ~2100-2250 RPM (extreme-3D)

Here's the math:

First, let's take a 450Kv motor as an example; Kv is a constant that basically means the motor output (RPMs) vary with voltage. In this case, 450Kv means 1volt = 450 RPM (but technically, Kv (lowercase v) is K=constant multiplied by v=velocity (as opposed to KV which is Kilo Volts). Anyway, knowing the Kv is handy. In the case of the 450, it means on an 8-cell LiPo pack (nominally 29.6V) this motor will theoretically turn about 13,320RPM (450x13,320). However, in the real world it's results in something different.

Fudge factor: or why theory and practice differ

There's some background math involved (quite a lot) but assessing an 85% fudge factor will get you close enough for the real world with an effective load. Note, some call this overall efficiency (the combination between ESC efficiency, motor efficiency, and prop or rotor blade efficiency). We prefer to use the term fudge factor because it's derived from our experience.

Anyway, as it turns out, 85% is a pretty valid rule of thumb when loading the motor near it's max amp rating. Thus, 450Kv x 8cells x 3.7V/cell x 0.85(85% fudge factor) =11,322RPM . . . and this is surprisingly close in the real world regardless of whether you're using the rotor blades of a helicopter, or a propeller, as the load.

Disclaimer:

By the way, we know to be careful with throwing efficiency numbers around. For example, the motor's efficiency isn't always what we say. If we're overloading the motor e.g. beyond the proper current range, then efficiency will be impaired. Similarly, running the motor with reduced load, impairs efficiency as well. This last seems utterly counterintuitive because we expect heat when operating the motor with a load, and conventional DC motors without a load don't get hot, but a brushless motor without a load gets hot. What's with that?

Delving into the subject leads you to learn it has to do with the magnetic field changing (inducing current into the iron)/. Thus, under low or no load conditions you have a multitude of dead shorts hiding inside the center of your motor! This has to do with the flow of current within the iron laminations (in the stator core). The current is dissipating as energy (and thus, producing heat). This is also known as eddy current or iron losses.

But the point is, theoretical efficiency basically goes out the window in the real world so please just accept the .85 fudge factor as something that will put you in the ballpark with real world loaded RPMs. Hence, using a fudge factor gives good practical results and this is important - especially recalling what a great wag once said on the subject:

Gear Ratios:

In a fixed wing application, e.g. direct drive, there's a 1:1 ratio between motor RPM and load (propeller) - e.g. the RPM of the prop - duh! However, with a helicopter, specifically a Pantera, the gear ratio is 8.7:1. Thus, for an 8S pack 11,322/8.7 = 1300RPM. This is nearly ideal for scale operations where the goal is to simulate the 600-800RPM for the full scale machine more closely than you can with a 2000RPM main rotor. By the way, with good throttle management this is good for maybe 8-9 minute flights.

450Kv on 10S

Now take the same 450KV motor on 10S (37V). It's going to turn the main rotor at about 1625RPM, which as it happens, is hunky-dory for sport aerobatics. So just by varying cell count we change the personality - see what we mean by dial a motor? Anyway, as it happens, maneuvers like loops, rolls, and stall turns, plus flips and tumbles are the sweet spot for 1600-1650RPM range.

So basically, on 10S you get plenty of poop for sport aerobatics. By the way, 'plenty of poop' is techno-speak for approximating an OS 55-class nitro engine, e.g. just about the perfect amount of power for a Pantera P6 model. This is enough to effortlessly cruise around for up to 7-8 minutes on a 5000mAh pack. Believe it or not, this is plenty of air time for nearly anybody. So the 450Kv motor on 10S is a very nice combination because you get sweet performance at an affordable cost. What happens on 12S?

450Kv on 12S

Basically, operating a Pantera P6 on 12S with a 450kv motor will really perk up the performance (into the aggressive sport, or mild-3D range). The rotor speed goes up to about 1925RPM but now the flight time decreases to maybe 5-1/2 minutes.

Want to know what else the 450Kv motor is great for? A classic pattern plane with an 11x7 prop (where you're going to see abut 17,000RPM). You'll have a rocket ship on your hands. One that will bellow like a bull and roar across the sky (and make every head turn). Fun? Oh no . . . it's 'great' fun!

520Kv motor

So what happens if you use the 520KV motor instead? On a 10S pack, with the 8.7:1 gear ratio of a Pantera (or divide by the gear ratio of whatever helicopter you have in mind), this gives you about 1875RPM. This gives sparkling aerobatic performance (and flight time goes up a little bit, to maybe 6-1/2 minutes). Alternatively, stuff a 12S pack in there and now you're going to see about 2250RPMs, which is what you want for crazy 3D performance range - not just tick-tocks but 'climbing' tick-tocks!

630Kv motor

You may also opt for the 630KV motor on 10S instead of a 12S pack. This will decrease weight and with around 2275RPM the model will flip and roll so fast it's a blur (note; 3D stick-bangers absolutely love this combination). Alternatively, switch to an 8S pack and you're looking at 1825RPM, or sport performance again. Dial-a-motor! Anyway, this is plenty of RPM for sport aerobatics - plus - flight duration goes up to maybe 7-1/2 to 8 minutes. Perhaps this is more your cup of tea!

720Kv motor

What about the 720Kv motor? Now the theory is 720RPM/volt but otherwise the math is exactly the same. Thus, on an 8S pack it's 720x8x3.7x.85)/8.7 so you'll see 2100RPM, which gives sparkling 3D performance. Depending on the pack capacity and collective management you may see around 6 minutes.

However, if you opt for a 6S pack for this motor, then the rotor head is gonna drop to around 1560RPM. Now we're in the range of sporting maneuvers. E.g. a lot of hovering, cruising around, with the odd loop or roll thrown in. This is absolutely a perfect combination if you like relaxed loafing around for long duration flights (of maybe 8-9 minutes, maybe more depending on how aggressive you are).

By the way, in a fixed wing model, the 720Kv is nice on a 6S5000mAH pack because you'll see 13,500RPM which is the sweet spot for a lot of 13x8-14x6 props.

Summary:

Astonishingly, all this comes out of the same basic motor! The key is hand winding different gauge wire. It's a stunningly simple system for making a fantastic motor!

- One single piece of wire loops in and back out in an AabBCcaABbcC pattern

Mechanical details:

The rotor features Neodymium magnets (NdFeB) radially arrayed within the body. And these strong rare earth magnets are secured within the rotor with high temperature epoxy. Your goal is to operate it below 260°F. Exceeds the max of 350°F and it's gonna be toast. You've been warned.

Also, the rotor has been dynamically balanced (to 30K RPM). This, by the way is the purpose of the blue epoxy (balance weight) in the photo below. Anyway, all this hand-built care is what you're paying for - the seamless and smooth delivery of pure power.

- Massive 10mm shaft - rotor is dynamically balanced (blue epoxy) to 30K RPM

Anyway, packing the 12-tooth stator with a single-strand of motor wire for high power handling, combined with the best magnets, plus the effort of balancing the rotor for high RPMs (so it won't buzz your electronics to death with vibration), along with 10mm bearings and what results is a Pmax. You get with power delivery that's smooth as silk, which is a really, really nice combination from this Delta-wound motor.

Bottom line? This motor is bad ass whether you're using it to power a helicopter or for fixed wing applications.

Q. Why are these motors so expensive?

A. This has to do with a few factors, chiefly how much copper you get inside (the more, the better) and how (especially the how) but basically, the more copper, the better. Technical details working against you whilst winding are as seemingly trivial as the insulation (varnish) which takes us space as you wind loop after loop of wire (adding up to space that's not available for copper). Added to which using multiple thinner-strands instead of a single large-diameter strand is attractive from a production standpoint but inevitably multi-strand also twists, which consumes useful space (again, meaning space not occupied by copper). Anyway, and as it turns out, a experienced man can cunningly wind copper more efficiently by hand than a machine (whether single or multi-strand) and thus the man consistently packs the available volume with the most copper possible. And this is good because it improves cooling and results in a lower IR motor (meaning more efficient). More efficient is another way of saying more power delivery. Thing is, winding a single-strand is bad from a production standpoint because it's more difficult, takes more time, and costs more money (labor isn't amortized like a machine). So machine-winding with multi-strand is quicker, easier, and cheaper, thus explaining why hand-wound single strand motors are the best - but also stupid expensive. Can't helped, so file this tidbit of knowledge under, it is what it is.