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Small Block Drill Motors

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There will come a time when the stock motors in the E-Maxx will eventually wear out. You’ll know they have one foot in the grave and the other on a banana peel when they begin making odd noises, start loosing power, or experience a catastrophic failure (i.e. copious amounts of smoke and a very bad smell coming from their vent holes). Either way, you’re now in the market for new motors.

power_wheels.jpg

The easiest thing at this point is to go online or drive to your favorite hobby store and buy yourself a new set of Titans. They’re great motors and are ready to bolt right into your E-Maxx.  However, what fun is this?? If you’re like me, you know that half the fun of owning an E-Maxx is to modify it and make things for it.  Plus, nothing beats finding a part for your E-Maxx where you least expect it.

Here’s an example. My kids have something called a PowerWheel (see picture).  It’s a plastic Jeep that’s powered by a 12 volt lead acid battery (like a small car battery).  The thing can carry my two kids (combined weight of 90 Lbs.) up and down hills and around the neighborhood without breaking a sweat.

So I got to wondering, “what kind of motor does this thing have?”  Time to break out the screw driver and take a look.  Imagine my surprise when I find that it’s driven by two Mabuchi RS-550VC motors. These are otherwise known as Titans! Yes, the same motors that drive your stock E-Maxx also drives this car.

The next question I asked myself is “where can I buy these and can I buy them for less than the cost of new Titans?”  Well, I already knew the answer to the first question because earlier in the day I drove past a vacuum repair store with a sign out front advertising that they repair PowerWheels.  A phone call to the store was is in order!

The owner of the store told me that he indeed had a supply of motors in stock but his contract with PowerWheels won’t allow him to sell them directly. PowerWheels doesn’t want the end customer working on their PowerWheels car themselves. He then said that if I could prove to him that I wasn’t planning to use the motors in a PowerWheels car he could then sell them to me.  So I gathered up my proof, my E-Maxx, and drove to meet him.

Words can’t describe how surprised this guy was to see my E-Maxx.  He never saw anything like it before and didn’t even know that such things existed. After looking at my truck for 15 minutes or so, he pulled out the motors.  Seems PowerWheels no longer uses Mabuchi motors.  Their new motor of choice is the Johnson 9689003 (I’ve been unable to find these motors on Johnson’s website.  I’ll post their specs when I find them.). He told me they have more torque than the Mabuchi motors and last longer.  I asked him how much they cost and he told me the price was $15 each.  Not bad.  A little cheaper than the Titans.

Despite being having the same dimensions as the Titans, these motors can’t be bolted on the truck - they need prepping.  You’ll see in the picture that the motors have large pressed on pinions.  These will need to be removed!

small_block_2_raw_motors.jpg

small_block_5_gear_remove.jpg

The easiest way to remove a pressed on pinion (short of having a pinion puller!) is to place the pinion in a vice, place a nail in the pinion so it is touching the spindle, and gently hit the nail with a hammer.  Several good taps should be enough to knock the spindle out of the pinion.

Once the pinion is removed, you’ll see that the spindle has some knurling on it (so the spindle could bite the pinion).  This will have to come off or else your pinion gear won’t fit on the spindle.  However, it’s not time to remove the knurling yet.  Read on and see why.

small_block_7_raw_spindle.jpg

Next we’re going to prepare the motor for soldering. The first thing is to sand the can and the motor’s leads with fine grit sandpaper (helps the solder to stick).  Next, clean the area with rubbing alcohol to remove any oil, etc.  Next, tin the can and the leads (tinning is the act of melting a little bit of solder onto the area). Lastly, solder on the capacitors and wires (the best source for these parts are your old Titans).

small_block_12_sand.jpg

Caps and wires installed

small_block_14_solder_job.jpg

OK, back to the knurling on the pinions. Now that we can attach the motor to a battery pack we are ready to remove the knurling.  How?  When the motor is powered up an spinning, gently hold a grinding stone on the knurling.  After a few moments, enough knurling is removed so that the pinions fit right on.  Be careful not to remove too much of the spindle! A metal file might not work since the spindles are usually hardened steel.

 

 

Mr. Knurling, meet Mr. Grinding Stone!

small_block_16_spindle_pre_grind.jpg

Knurling’s all gone!

small_block_17_spindle_post_grind.jpg

Now that the knurling is gone, we have one thing left to do - grind a small flat spot onto the spindle for the pinion’s set-screw.  The best way to do this is to use a Dremel tool with a grinding wheel. When grinding the flat spot take care not to let the spindle get too hot or else you’ll damage the motor!

Nice ‘n flat!

small_block_19_spindle_flat_spot.jpg

And here’s the finished job! Unless you look closely, you would think that stock Titan’s are installed. The most obvious difference is the fans are more heavy duty on these motors.

small_block_20_finished_jobs.jpg

All in all, the whole process of prepping both motors took me about half an hour.  Not bad and I saved over $10 to boot!

At this point you may be asking, “how well do these motors run??”  After all if they’re not at least as good as the Titans then they’re not worth it.  To answer that question I’m happy to report that I’m very pleased with them.

These motors do have more torque than the Titans.  For example, a stock E-Maxx comes with pinion/spur gearing of 18/66 which amounts to a ratio of 3.66:1.  At this gearing these motors easily wind out in second gear and the motors/batts/EVX stayed frosty.  Obviously, these motors can take a lower gear ratio so I tossed on a bigger set of pinions which are in the photo. With 20 teeth, these pinions give me a ratio of 3.3:1. At this gearing the motors still wind out in second gear and the top speed is about the same as a stock E-Maxx. However, the truck easily wheelies in second gear and if you hit the breaks in first gear while at speed, the truck will tail up and flip over. With this gearing, the motors reached a temp of 152 F, the EVX’s cooling fins reached 135 F, and the batts (2X7 of GP 3300) stayed cool to the touch.  The outdoor air temp was 88 F.  Even when running in tall grass (ankle high), things didn’t get much warmer.

 

Based on these favorable results, I decided it was time to drop down to a smaller spur gear so I tossed in a 64 tooth spur and kept the 20 tooth pinions. This gives me a ratio of 3.1:1.  At this ratio, I feel I’ve reached a balance between low end torque and maximum top speed. The truck will wheelie and tails up in first gear and it wheelies in second gear. At this gear ratio, the motors reached 164 F and the EVX’s cooling fins reached 144 F. The batteries were warm but not hot. During this test I did some grass driving, top speed runs on pavement, some jumps, basically a little of everything but all of it was hard driving.

I contacted the makers of PowerWheels and they told me they currently use Johnson HC683LP Series motors (Code PT03007, Type PMDC, 600 Size) with the following specs (compared to the stock Titans):

Model

Voltage

No Load

At Max Efficiency

Stall

Operating Range

Nominal

Speed (r/min)

Curren t (a)

Speed (r/min)

Current (a)

Torque

Output (w)

Torque

Current (a)

HC683LP

6.0 ~ 12

12V

22,300

1.84

19,600

12.99

69 mN-m

NA

142

560 mN-m

NA

91.7

RS-550VC

6.0 ~ 14.4

14.4V

19,800

1.30

17,620

10.5

64 mN-m

660 g-cm

119

588 mN-m

5994 g-cm

85.0

Now keep in mind the figures shown above for the HC683LP motors are at 12 volts. To make a fair comparison with the Titans, you’ll need to increase the Johnson’s figures by 1.2% to make up for the voltage difference. Additionally, at maximum efficiency, the Johnson’s have the following specs: Efficiency: 76.1%, Torque: 69.49 m-Nm, Speed: 19,600 RPM, Current 13 amps, and Output: 142.398 watts.

In conclusion, based on my subjective testing I have to say that these motors are better than the stock Titans. They have more torque (as evidenced by the ability to have lower gearing and by the figures above) and therefore give the truck more power. Since my runtimes don’t seem any shorter, I would estimate that they are probably more efficient than the Titans too. So when it’s time to replace your Titans, you may want to give these motors a try!