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Introduction to Xmods

Xmods most Frequently Asked Questions

'Tips and Tricks' to tune your Xmod?

Xmods Manuals

Crest Spin Brush (SB) Motor Modification

Upgrades for your Xmod

'Builder's Corner' Reader's rides

'Review Section' Info on parts and vendors

'Motor Guide'

Xmod Evo Models

Evo v.s. Xmod

Upgrades for your Xmod Evo

Evo's most Frequently Asked Questions

'PimpMyMod' section


Motor Review and Purchasing/Modification Tutorial

I purchased a variety of motor parts and pre-built motors from a few sources that I found on the web, as I present the information about them I'll need to explain some of the more important points when dealing with DC motors and how they will affect your choice.

DC motors are fairly simple as they contain three main parts

  1. The 'Can' which is the container for all the parts itself can be made up of many different parts and configurations but the most common thing you'll notice is whether the can is 'vented' or 'closed' and you should note if the can uses bushing or a ball-bearings. The can also has an 'End-bell' which house the brushes that provide power to the motor.
  2. Permanent Magnets are installed into the can and create a magnetic field, the strength of this field is affected by the type of material used 'Ferrite' has the lowest magnetic field (used in stock Xmod motors) an upgrade to 'Isotropic Ferrite' yields a much stronger field and the rare earth 'Neodymium' Magnet creates the strongest magnetic field.
  3. The 'Armature' is what spins in the motor and is made up of the commutator, laminations, shaft and winds. Electricity flows through the brushes to the commutator, and into the windings on the arm. Since the windings are wrapped into a coil, they create a magnetic field when current is passed through them. This magnetic field is repelled and attracted to the magnets in the can causing the arm to turn. The 'Arm' can be made from many different types/styles of parts and is the heart of your motor.

When considering a motor for an Xmod you need to be aware of the Xmod killer which is a motor that draws excessive current resulting in a fried FET (read more about FET's Here) most sites selling motors will mention if stock FET's are fine or if you require 'Stacked' FET's or an optional voltage regulator board to use the particular motor. Luckily the Evo Xmod can handle higher current motors but you can still blow your FET's if not careful.

Windings anyone?

Every armature requires a few well placed turns of copper wire but how many do we require for a performance motor and is less more, or is more better?

  • A Motor with More Winds is less demanding on the battery, and smoother in acceleration it will also run much cooler due to the fact that a motor also acts as a generator when rotating even while under power.

    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. The motor, as it starts to turn 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 power required to keep the motor spinning is reduces by the amount of energy the motor creates.

  • A Low Wind Motor is more punchy and can be difficult to handle this is a result of the reduced mass (coils of wire) on the armature, obviously a lighter armature will spin-up faster than a heavier one but draws more current because the field is weaker and it requires more power to keep running as it creates less back EMF. A low wind armature is also called a 'Hot winding' the downside is the heat generated may be hard to dissipate and can lead to a fried motor. The upside is a faster motor with lots of torque.

So to recap winds with fewer wraps give greater starting torque and better acceleration, but lower top end and run hotter. Conversely, the higher wraps will have less starting torque, but higher top end and will run cooler. My take on the winds deal is simple, A cool motor is an efficient motor as your motor will loose power due to heat, because the magnets become less efficient when subjected to heat.

Wanna see some really nice 'Cans'?

This option is fairly simple ball-bearings reduce friction and will help to reduce wear of the armature so try and find motors that use Ball-bearings. Bushing are fine for general use but if your trying to upgrade the motor why bother with bushing go for the best!

Vented versus Closed, I prefer using a vented Can as the spinning armature acts like a fan and helps to cool the motor down but increases the chance of foreign matter getting into your motor. A closed can will keep the foreign matter out but also traps the heat in, so unless you have a good reason to opt for a closed can I suggest using a vented can.

Do magnets really make a difference?

The general rule is the stronger the magnets the more torque that will be produced but at the sacrifice of top-speed, stronger magnets limit the RPM. Most motors have been designed around the magnets used in the motor so changing them can result in the motor properties being altered sufficiently to cause unforeseen issues such as excessive current draw leading to FET's failing.

Here is a chart describing some typical motors I have purchased and some modifications I have added to them.

 

Standard Stage 2 motor upgrade from Radio Shack.
Closed can with bushings no information about windings but it lists a 30K rpm. I found it to be quicker than the Stage 1 motor but it lacked any real punch and it ran pretty hot. I swapped the magnets for some Isotropic Ferrite magnets and was pleasantly surprised by the amount of torque that was added. Next I swapped these for the Neodymium magnets and saw the torque jump to the next level. I was able to compensate for the lower top-end by jumping to the next higher gear.

Pros
Low cost and easy to modify
Adding Neo's really bring's this motor to the next level
Runs fine on stock FET's

Cons
Runs 'Hot'

These next few motors were all purchased from Maine-iac-Motors
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The Blue Power SE EVO (45T)

At 4.81volts the motor draws 0.45 amps and the motor reached 35,520 rpm
 

The Blue Power SE EVO is the fastest stock motor that does not need a FET's upgrade. It comes with 45 turns of 31AWG armature and strong stock magnets. This motor has a good balance between torque and speed. To help it's performance it has a ball bearing end-bell. It's safe to use in stock Xmods

Pros
Low cost
Higher rpm than a Stage 2
Decent torque and top-end
vented Can helps keep it cool
Ran very cool barely warm to the touch

Cons
Used a bushing on the can instead of a Ball-bearing

     

The Blue Power SE (47T)

I'll assume this model is slightly slower at around 33,500 rpm with a draw of about 0.44 at 4.81 volts
 

The Blue Power SE is the fastest stock motor that does not need a FET's upgrade. It comes with 47 turns of 31AWG armature and strong stock magnets. This motor has a good balance between torque and speed. To help it's performance it has a ball bearing end-bell. It's safe to use in stock Xmods

Pros
Low cost
Higher rpm than a Stage 2
Decent torque and top-end
vented Can helps keep it cool
Ran very cool barely warm to the touch

Cons
Used a bushing on the can instead of a Ball-bearing

     



At 4.81volts the motor draws 0.44 amps and the motor reached 32,610 rpm
 

The Blue Stock is powerful stock race motor It comes with 50 turns of 31AWG on the armature, strong stock magnets, it normally comes with a bushing can but I received a ball-bearing end-bell with my order.

Pros
Low cost
Higher rpm than a Stage 2
Decent torque and top-end
vented Can helps keep it cool
Ran very cool barely warm to the touch

Cons
Used a bushing on the can instead of a Ball-bearing

I was hard pressed to find any significant difference between these three motors they all ran amazingly cool and were sent to me broken in so I was ready to run I would have liked to see a ball-bearing can but at least the end-bell was (I suspect at this price range you won't find many upgrade motors that do have them). I ended up liking the The Blue Power SE EVO (45T) the best as it had a bit more punch and a slightly higher top-end. So I wandered back to the Maine-iac website and noted some specs for other high-performance motors than would need a FET upgrade and found these two



  This is for a 35T or 35 turn winding you'll notice the rpm jumps to 44,610 rpm and the draw also jumps to 0.79amps

This was for the 28T motor and here you really start to see the affect of less turns as the rpm has now hit over 45,000 rpm and the draw as gone over 1.0 amps
Meet my little Frankenstein Muh ha ha!
 

Well I guess I should learn to leave stuff alone but alas I had to play with these motors a little to see if I could improve them.
I started with the The Blue Power SE EVO (45T) and changed the Can for a Ball-Bearing Can that contained a set of Neodymium magnets I kept the end-bell and brush's from the Blue Power SE EVO so the only change was the Ball-bearing can and stronger magnets. I strapped my new Frankenstein in to my Evo and prepared to give it a test run.

Holy Shit! this little upgrade has turned this motor into a torque monster at the slightest bit of throttle the rear wheels will break free and the car fishtails all over the place and I'm using the AWD! I have to ease into full throttle slowly and when she reached top-speed I knew that it was at least 20% faster than before I frankensteined it! I literally have an issue keeping the god-darned tires on the rims! I use the softest tire with treads since I'm on concrete and if you hold the car in your hands and hit the throttle they balloon outwards and will fly off! I actually cracked two of the plastic lug-nuts during my first 10 minute run. I was completely amazed that after 10 minutes the motor was only starting to get noticeably warm. Try your Xmod and see if it will do this, place your car against your foot and give it full throttle, it most-likely just stalls and makes some noise right? Well my little frankenstein spins all four wheels as it tries to overcome the obstacle in its way!

Remember I'm using stock/factory electronics with regular 4AAA Nimh batteries I've used my frankenstein now for quite a few long sessions will no issues (other than tires spinning off) and after a good hard 15 minute session the motor was still much cooler than any other motor I've tried, yes it does heat-up but nowhere near those finger-searing temperatures I've burnt myself on with previous motors.

I forgot to mention I have to drive with the steering trim set close to minimum or it just keeps spinning in circles with each twist of the steering control.

I've found an even better motor offered by Maine-aic-Motors the details are Here

Well I'm done hope this helps you choose your next motor but first check out the next section for some ideas of parts you should be looking for in your next motor.

"Extreme motors require the best parts"

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