most powerfull brushed motor when limited to 7,4 volts

[murky123]

Guys.
what would be my best option for a motor when I am limited to 2s lipo ?
so I am driving a 2s lipo, rig weight is 9lbs, I plan on keeping 1.9 wheels
I do not care for wheelspeed and I am keeping the stock 14/87 pinion/spur.

I just wat to know what the best motor with the highest torque would be with this setup..

[Flyin Hawaiian]

holmes hobbies puller motors

[BOB8789]

Originally Posted by Flyin Hawaiian

holmes hobbies puller motors

I was going to say that, appearantly the 10t ones will pull your truck apart if you aren't careful.

[murky123]

how do I have to look at the turns with these puller motors?
lower turns is more torque ?

do these motors fit on the honcho with the tranny in stock position?

[JohnRobHolmes]

Now I see what you need

The 10t is going to be your best bet without losing wheel speed. It will produce as much torque as your battery and drivetrain will allow for. You can install a Puller into your rig with no worries, they bolt right in.

Lower turns will produce more power and torque until the brushes, wires, or battery reach current saturation. I never cared to find the "sweet" wind for a puller because any of them will break parts.

[sweli]

http://www.rcuniverse.com/magazine/a...article_id=505

?Basics of choosing a motor and ESC/MSC and Brushed vs. Brushless Systems?

There are always a ton of threads about motors and ESCs and they are all usually variants on the same questions. In this article I will go through and explain the basics of choosing a motor and ESC/MSC, and talk about brushed vs. brushless systems.

When choosing a motor it is important to choose one that meets your abilities and budget. The first thing to consider when buying a motor is how fast you realistically want the car to go. I know you all want your cars going 50mph, but there are only a few of us who have enough driving experience to go that fast without hitting straight into a wall. The basics on turns and winds are as follows:
Lower Turn = Higher Top End/Less Torque
Higher Turn = Lower Top End/More Torque

As you look at motors with lower winds, you begin to see motors like a 9x3. This means that the motor is 9 turns and has 3 winds. The winds are simply for more speed, the more you have, the faster you go. One thing to note about lower turn motors is that they need a lot more maintenance. You can probably run a stock motor (27T) for 15-20 runs before it needs to have the commutator cut. On the other hand, a 9T motor needs to be cut every 3-5 runs.

There are a few classes for brushed motors:
Stock (27 Turn)
19T Spec (19 Turn)
Unlimited (Any amount of turns)

Your hobby shop or race track may have others, but these are the common ones.

Choosing whether to get an ESC or MSC is an easy decision. Get an ESC. MSCs (Mechanical Speed Controls) are very outdated and cannot handle today's motors.
When choosing an ESC you truly have to rate your skill level. While you may have a 19 Turn motor today, will you be changing to an 8 Turn motor soon? The answer is probably not. An ESC's limit is the lowest number of turns that it can handle. Now you have to make a big decision. Since ESCs that can handle lower turn motors are more expensive, you will have to decide how low you're gonna go. It makes no sense to buy an ESC with no turn limits if you are going to race Stock and 19 Spec, nor does it make sense to buy an ESC with a 17T limit if you are going to race Unlimited. This is basically up to you (and your budget), but be reasonable and get an ESC with a limit that is around your skill level.

My final rant will be on brushed vs. brushless. While these systems are in relatively the same price range, they each have their own pros and cons. A brushed system needs a lot of maintenance, but offers more flexibility because you can change motors depending on track conditions (how much torque you need). A brushless system on the other hand, needs almost no maintenance.

There are two basic decisions you need to make when buying a brushless system. How much can you afford to spend and how many transmission gears you want to replace. The Novak systems are more affordable, ranging from about $180-210 and include both a motor and ESC. The next level up would be a Warrior/Feigao combo which will be about $250 and will have more power and a nicer ESC. The highest level of brushless are the Hackers, Lehners, and Shulze. These are not for novices, and must be geared almost perfectly. These systems can range from about $400-800 for just a motor and ESC. Also note that the Novak and Warrior/Feigao combos offer better customer support and are easier to get.










Understanding Electric Motor Basics
Thanks To:SkrapIron and AS-EE

It happens every time I complete a run with my electric powered truck at the track. Almost all of the other trucks and buggies that are run there are nitro powered. I constantly hear comments like, “Man, that thing’s fast, for an electric.” “It’s so quiet.”

It really doesn’t surprise me any more, since there is such a grave misunderstanding of just how electric motors work. Most enthusiasts have a good understanding of the internal combustion engine, but to those same people an electric motor is an enigma.

In our hobby, we use a permanent magnet direct current (DC) motor. All of these motors operate from the DC voltage supplied by a battery pack. The battery chemistry can vary greatly, and what type is chosen can dramatically affect the performance of the motor. At the core of these motors lie magnets that are typically made of iron-ferrite or, less often, a rare earth material such as neodymium.
Lower-cost iron-ferrite motors usually employ oiled bronze bushings to support the ends of the armature shaft and stamped-metal can housing. Better-quality motors use stronger but more expensive rare earth magnets and almost always have ball bearings to support the shaft in machined housings. Motors will vary greatly in their physical size as well as their capacities, so selection of a proper motor for your application is critical.

The DC motor is broken into 2 distinct components. The stationary parts of the motor, collectively called the "stator," include the magnets, brushes, brush hood, and springs. The rotating portion or "rotor" includes the commutator plates, armature and windings. The motor's job is to convert stored electrical energy into mechanical energy. It does so through the process called commutation. Commutation occurs when a portion of the windings on the armature are energized in any one position. As the motor’s position in the magnetic field changes, the brushes connect to different windings through the commutator plates. The brush motor is designed so that the optimal windings are energized in every position.

Brush motors are most often identified using the number of turns and winds with which it is constructed.
A turn refers to a complete wrap of a coil of wire around an armature arm (15 turns means 15 loops of 1 wire on each arm). Higher number turns will be slower because more copper coils are exposed to the magnetic flux lines of the stator magnets. This will cause a greater amount of counter-voltage to be induced when the armature "cuts" through the magnetic lines per unit time. Counter-voltage then subtracts from supply voltage in the armature coils, and this will in turn cause your armature coils to have less current flowing through them which results in a slowing of rotational speed. A lower number of turns will be faster, since fewer copper coils are exposed to the flux lines of the stator magnets. It is in these applications that higher flux density magnets, such as neodymium, can be used

A wind refers to the number of strands of wire, wrapped around the armature, in 1 turn. In general, winds with fewer wires give greater starting torque and better acceleration, but lower top end. Conversely, higher winds with more wires will have less starting torque, but higher top end.

A brushless DC motor functions a bit differently than its brushed counterpart. In a brushless motor, the permanent magnets are mounted on the rotor. The windings are stationary and attached to the motor's outer case. Since it is now the magnet that is turning, instead of the windings, the commutation must be done electronically rather than mechanically. An integrated sensor circuit in the motor, along with the microprocessor in the Electronic Speed Control, controls commutation. This control is delivered by calculating the rotor’s position, and determining how to channel the current to supply the requested torque with minimal current. These sensor based motors provide the smoothest and quickest delivery of torque, but are limited in their RPM potential. Several DC brushless motors forgo the integrated sensor circuit in favor of a 6 step drive. Six-step drives channel current into only two windings at any one time. This simplifies the design and construction of the drive. However, the torque produced by six-step drives has more ripple and is produced less efficiently, compared to sensor based brushless motors.

Brushless, sensorless motors with three connections are in fact, not DC motors at all. They are actually permanent magnet synchronous AC, 3-phase motors. The ESCs that control them, have three distinct semi sinusoidal waveforms (not pure sinewave AC) that come in at different times (or degrees) which causes the rotor to rotate with the changing (alternating) magnetic fields of the stator. While this is still not as smooth in operation as a sensor-based motor, it does allow for tremendously greater power, and a much higher operating RPM.

Brushless motors are inherently more efficient than brushed motors for multiple reasons. Since there is no mechanical commutation, there is no wasted energy from friction between the brushes and commutator. There is also no loss in efficiency due to the build up of contamination on the commutator. Additionally, because the windings are physically mounted to the outer case, heat is more efficiently drawn away from the motor.

For any motor, either brushed or brushless, the voltage that is supplied to the windings controls the speed of the rotor. This supply is referred to as the voltage constant, which is represented with the symbol Kv. Kv is the rpm per volt that the motor will produce. (Kv x Volts = RPM) The higher the Kv, the faster the motor shaft will turn for each volt applied. But judging the performance of a motor solely based on its voltage constant (Kv), is a mistake.

Along with the Kv of the motor, there is something else to consider. Every motor has a torque constant (Kt). Kt is the amount of torque the motor can deliver to the pinion shaft, and is rated in either ounce/inches or Newton millimeters per amp of current. What is difficult to understand at first is that the Kt is inversely proportional to the Kv of the motor. That means, as the Kv of the motor increases, the Kt decreases. It therefore stands to reason that a high Kv motor cannot deliver as much torque as a similar-size lower Kv motor.

When a DC motor is energized, it draws a large initial surge of current. The surge is caused because the motor, when it is turning, also acts as a generator. The generated voltage is directly proportional to the speed of the motor. The current through the motor is controlled by the difference between the battery voltage and the motor's generated voltage, otherwise called back EMF. When power is first applied to the motor, there is no back EMF. That means that the current is controlled only by the battery voltage, battery internal resistance, motor internal resistance and the battery leads. Without any back EMF the motor, as it starts to turn, the motor draws the large surge current. This surge of current is what generates huge amounts of initial torque. As the current flow evens out, with the back EMF, the torque curve falls off proportionally.

[JohnRobHolmes]

Pretty off topic, but I just can't let bad info slide past.

The notion that a higher turn motor produces more torque is a (very common) fallacy from past days, it is only a limitation due to the design of the 540 brushed motor endbell and commutator. While lower turn motors need more amperage to produce the same torque, the phase resistance is lower so they can pass the amperage needed to produce the same amount of torque. A correct explanation is that the brushed 540 motor can be wound to a point of brush and commutator saturation. Past this point the torque falls because of the lower Kt value and fixed amperage available to the coils. The rest of the motor and system can cope with faster winds and produce more torque than slower motors for a given voltage.


I will attach two brushless motor dynos to show that faster motors can indeed produce more torque when the rest of the system is designed to handle the higher currents needed. Lower turn motors producing more torque?!?! Blasphemy!!

[.bg.]

...

[beidave]

Sweli, great explanation. But John is right, the question is can you be trusted with the wheel speed. A good esc and throttle finger are a must.

[murky123]

I see now 2 different kinds of pullers.

Cobalt Puller 454.... 40 dollar....11 turn 3300 KV
Holmes Hobbies Cobalt Puller..... 80 dollar.....10t- 1800 rpm/volt


wich one should be mine

[671_oners]

Originally Posted by murky123

I see now 2 different kinds of pullers.

Cobalt Puller 454.... 40 dollar....11 turn 3300 KV
Holmes Hobbies Cobalt Puller..... 80 dollar.....10t- 1800 rpm/volt


wich one should be mine

10t hands down....

[obsession4x4]

Originally Posted by JohnRobHolmes

Pretty off topic, but I just can't let bad info slide past.


I will attach two brushless motor dynos to show that faster motors can indeed produce more torque when the rest of the system is designed to handle the higher currents needed. Lower turn motors producing more torque?!?! Blasphemy!!

Hi John,
what type of dyno do you use to check your motor?
I have never seen this data form.

[JohnRobHolmes]

These were on a home made unit an electrical engineer made, data pulled from a "cycle analyst" via serial data streaming. Not my own unit.

[Manning]

Originally Posted by JohnRobHolmes

Pretty off topic, but I just can't let bad info slide past.

The notion that a higher turn motor produces more torque is a (very common) fallacy from past days, it is only a limitation due to the design of the 540 brushed motor endbell and commutator. While lower turn motors need more amperage to produce the same torque, the phase resistance is lower so they can pass the amperage needed to produce the same amount of torque. A correct explanation is that the brushed 540 motor can be wound to a point of brush and commutator saturation. Past this point the torque falls because of the lower Kt value and fixed amperage available to the coils. The rest of the motor and system can cope with faster winds and produce more torque than slower motors for a given voltage.

Thank you. It kills me when I read the "higher turns = more torque" philosophy. I want to hand somebody that thinks that my old 4wd off road race 10 single and see if they think it has less torque than their 55t motor......

[rusty577]

So what would be the best holmes hobbies motor for a standard geared scx10? I have a axial 55t at the moment but looking for a upgrade. Dont want to lose any torque but would love some more wheel speed.

Im running 2S lipos at the moment but plan to run 3S in the future with a upgrade esc from the novak rooster crawler I have now to something better that will handle more voltage.

[JohnRobHolmes]

I would say a TorqueMaster 45t or 35t, or a Crawlmaster 540 28t if you are looking for 540. Keeping within my brand pool a Puller 10t would also be a good bet for even more power and torque.

[beidave]

I'm running a HH 25 turn hand wound and loving it. Plenty of wheelspeed and smooth bottom. I'm running 2.2 tires, we comp a tuff truck format hill climb, sled pull,mudbog and course. It works pretty well.