Hop-Ups and Aftermarket Parts

One of the best things about R/C cars is the vast number of upgradeable parts that are offered.  HPI has a few for the Micro RS4 but it's the aftermarket that usually takes hold and reproduces tons of goodies.  First thing I'd like to do is get all the aluminum parts I can for this thing.  There's a lot of plastic in there, but plastic is still good.  It's lightweight, it's flexible and it's inexpensive and therefore is the obvious answer to machining parts.  Which is why 95% of this car is plastic.  But anodized aluminum just looks plain cool.  I'd like to get some other bodies as well, some in the 150mm and get a new belt.  That way I'll have more room for motor upgrades.  Click here for the Ultimate Hop-Up Heaven Drool Page.
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The Need for Speed

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 Speedster Racing



Current Setup 11.01.02
     Ratzas Pro Pan
     Stock Rear Deck Modified
     VCS Shock Rear
     Stock Shocks Front
     Speed 400 4.8V Race
      13T Aluminum (4:46:1)
     TRC Pinks on modified 24mm rim
     TRC Magenta in front
     GH Front Ball Differential (modded)
     GH Rear Ball Differential
     GPM Alloy Universal Joints
     Futaba T2PHKA
     Futaba FP-R122JE
     Futaba MC230CR
     Futaba S3003 Standard
Battery Pack
     1100mAh 2/3A Nexcell 8 Cell 9.6V

Quick Links

Promax 400 7.2V-8.4V Mpi Motor

This motor works best on lots of cells and a tall gear ratio.  It comes preinstalled with two caps (which is all you really need) and costs a mere $8.99.  Currently I'm running it with a 20T pinion and 10 cells.  Two of the cells are AA NiCADs strapped to the rear deck like a pair of NOS bottles.  I'm measuring about 11.60V (on dead batteries) at the terminals on the motor and this setup is very fast and very powerul.  It is quite comparable to the Speed 400 4.8V motor but  with quite a bit more low-end grunt, even though the gear ratio is almost twice as high.  Top-end speed feels very good and the car is completely controllable.  This is the setup I will run at the track next Wednesday.  Here's some pics of the motor and the car.

After running this motor, I found it to be a very poor performer.  I ended up removing the 2 extra cells, and going down to just 8, but it still couldn't keep up with guys running Speed 300's on only 6 cells.  I'm not sure if it was gearing, or lack of juice, or just the fact that it's a real low RPM motor.  I tried a 22T and it was little faster, but not enough.   So when you try out just any 400 motor, be aware that not all of these motors will be good candidates for speed.  The Watt-Age 380 for gearboxes is even a better motor than this.  Still the best setup by far is the Speed 400 4.8V race motor with 8 cells (or more) and a 13T pinion.

The Raw Scoop on 280 vs. 380 Sized Motors

This is why I prefer Speed 400's over anything else.  I cracked a Watt-Age 370 and a TSH Super 400 and compared the insides.  Here's a picture of my findings.  Bottom line - bigger IS better.  Everything about the 380 motor is bigger, beefier, stronger, and more robust than its younger brother the 280 sized peep.  It's actually funny how even though these motors look so much different, their performance is really quite comparable.  However in the long run, the 400 wins in lifespan, voltage capability, power, and speed.  What's not to like?

The Insides of Two Motors Compared

How Fast Can You Make Your Micro Go?

I put together a rather simple excel spreadsheet that calculates MPH given the motor constant, voltage and gear ratio.  It's not totally accurate, but can be helpful in making simple comparisons between different setups.  Like how much faster will your Speed 300 go if you jump from a 12T to a 13T?  How about if you add 1 cell and drop from a 12T to an 11T?  The program makes some assumptions that would be far beyond the scope of my programming skills, so you've gotta take the results with a grain or two of salt.  It's been helpful to me.

Download Micro Motor Speed Calculator

Speed 400 4.8V Race

This one page has gotten ridiculously long.  So I lied about that other 380 motor being my last motor.  I bought one more.  But this one is the last!  My Micro projects have become so time consuming lately, I almost can't keep up.  So I called this hobby shop in town that does 90% airplanes and man they had a lot of Graupner Speed motors just sitting on a shelf.  I could have bought a handful of 370 motors for $8.99 a piece.  A bargain for sure, but I refrained keeping my one single goal in mind...put a Speed 400 Race motor in my Micro.  And after about 6 hours of rebuild, I'm happy to say she's done.

As I suspected with the 20T pinion, there is no need to modify the rear bulkhead in any way.  The rear deck I raised up with two nylon washers.  The biggest modification I had to do was cutting the rear deck to accommodate the VCS shock.  Which is mounted somewhat oddly, I may have to work on that one.  But everything else is mostly stock.   See my current setup to the left.  I painted my front springs red.  Now they match the coilovers in my Civic which gave my real car its nice drop.  So here's some preliminary pics.  

Read this thread at the YourMicro.com forums for more info.  This particular setup was a grave disappointment.  *The 4.8V Race motor cannot drive a 20T pinion.   I had to move back to the 16T pinion and my old shaved away rear bulkhead for the car to even work.   And once it did, it didn't end up being that fast after all.   A 13T proved to be the best setup overall.  Read on...

After driving around this new setup and with some help from the YourMicro forum (thanks Miha and Ryan), I realized that the car is still underpowered.  The blasted gear ratio is still too high.  So I dropped down to my stock 14T Micro pinion that I had been using with my Speed 300.  I didn't think it would fit, but Ryan insisted that it would and sure enough it did.  Now my setup is nearly identical to every Micro RC'er out there, except I'm running a Speed 400 on a 14T pinion and 7 cells.  Which brings me to something I've recently learned about RC cars.  The Three Keys to Micro RC Speed are:  motor, gearing, and batteries.  Pick the right combination of the three and you can have yourself a wide variety of Micro driving schemes from tons of low-end toque for short, quick tracks, or gobs of top-end speed for long straight-aways or something in the middle that runs cool and lasts for hours.  For most people that combination consists simply of a Speed 300 or Watt-Age 370 on 6 cells and a 12T or 13T pinion.  And I admit, that setup rocks and it has been proven by nearly all the Micro owners out there.  But I believe we've just scratched the surface on the capabilities and the possibilities of more cells, bigger motors, as well as a wide range of gear ratios.

My latest theory suggests these 3 possible setups:

Speed 400 Series (380) Size Motors

  • Speed 4.8V Race, 7 or 8 Cells, 14T - Awesome. Verified.

  • Speed 6V, 8 or 9 cells, 15-17T - Still even more awesome. Unverified.

  • WattAge 380 (gearboxes) 8 cells, 20T - Screaming fast. Verified.

  • Speed 7.2V, 9 or 11 cells, 22-25T - Rockin' your world. Unverified

I've now actually changed my setup to incorporate a lower gear ratio for improved performance on a road course and I added one more cell to make an even 8.  So I'm running the Speed 400 4.8V Race motor with a 13T pinion and 8 cells all of an MC230CR ESC.  And it's awesome!

Watt-Age 380 Motor (for gear boxes)

I thought this was the last motor I would buy.  But it wasn't.  I bought it from Hobby PeopleRunning 8 cells and a 16T pinion.   You know, if there were a few more people into Micros in my area, I'd love to get together and have some real races.  I can only drive up and down my street so many times before I'm bored.  I want to race, on a track against other Micro owners.  If you live in town, email me.  Let's hook up and race sometime.  In the meantime, here's the motor I will be installing.

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Putting a 380 sized motor in a Micro isn't all that hard at all, but it does require some cutting, trimming and drilling to make the thing work.   With the proper gear ratio and right number of cells this motor is VERY fast.   It's smoking fast.

First things first, the motor plate has to be modified.  A Speed 300 motor plate will work fine.  The upper screw mount and center motor spindle opening need to be widened.  That's it.  The rear axle housing needs to be shaved just until the bearings start to show through.  I even shaved off the upper motor plate mounting screw and only use the one lower screw.  So far it works fine and without that extra piece of plastic in the way, the motor can be mounted closer to the axle housing which will allow smaller pinions for even more torque.  I started by using a 16T standard pinion with 1/8" copper tubing inside which makes a perfect fit over the 380's smaller diameter shaft.  I later moved up to a 20T which proved to be a very worthwhile move.  Read on...

Next, if your running a 150mm wheelbase, the rear deck shouldn't need to be modified.  You may need to install a couple of 4-40 nylon washers underneath each post to raise it a bit.  But if you want a run a 140mm, it certainly can be done.  I chopped off the rear posts on the rear deck and then filed the leftover nubs to match the height of the screw mounts for the upper deck.  Then using some leftover plastic from my old upper deck, I made little extender pieces that widen the mounting locations of the rear deck and used the 2 screw locations for the upper deck and 2 more screw holes where the old posts were to mount.  They're kind of like ears that stick off the rear deck.  Then using some 2" body posts for 1/10th scale cars I cut off about 7/8" off each post leaving about 1-1/8" and mounted them to the outside of the new rear deck ears.  Lastly I drilled two new holes in my Ratzas chassis about 7/16" further out from the stock holes.  This widens the rear deck mounting posts by about 7/8" making it 2-7/8" wide instead of just 2" wide.  Now the 380 motor can fit snuggly right underneath the rear deck using a 140mm wheelbase.  Not only that, but with the rear deck up off the motor, like it is with the stock motor, I can use my stock shock as well.  Check out the pictures if any of this seems confusing.  It's not all that hard to do and is a great way to kill a Saturday afternoon.  

First run 16T:  After I got all my electronics back on the chassis I took this monster out for a spin.  I thought it was going to tear up the pavement, but it didn't.  It sped off down the street pretty dang fast, but as fast as I was used to, especially running 8 cells.  However, my batteries hadn't been fully charged in days, and I wasn't sure how much juice was really left in them.  I was trying to run the batteries all the way down before sticking them on the charger.  That actually proved to be a harder task than I thought seeing as how a 30 minutes into my driving adventure, the batteries still seemed to have as much charge in them as they had before and the car wasn't slowing down.  Not only that but the batteries were cool, barely warm to the touch and the motor was the same.  I could put on finger on it and hold it there for as long as I wanted and it never got too hot.  Thinking maybe I wasn't running full juice, I checked the power to motor with a DMM and measured 9.41 volts.  Well it wasn't 9.6V which I would have expected to see if I were running a full charge, so maybe with a new charge in the batteries, I'll get some faster run times.

This motor actually performed very similarly to the Super 400 (380 motor for direct drive) that I had installed last month (see review below) that I didn't like at all.  But now I've wised up a bit in my old age.  Speed isn't always the one single goal to achieve.  I like the fact that this motor and these 8 cells can run all day long and never get too hot so as to cause concern.  Every time I drove my Speed 300 or my 370, I thought I was going to burn up the batteries, the motors or both, which inevitable did happen on two separate occasions.  I can tell that my current set-up is in for the long haul.  

Here's a list of a few other off-the-shelf non-Micro-stickered motors that I'd like to try out:

Updated: So my original setup was pretty nice, not super fast but definitely fun.  I decided to mess around with the gear ratio of this thing, and go to a 20T pinion instead of the 16T I had been running.  My batteries were bone dead because I hadn't driven my car in a week, but I popped them on my car battery (yes my real car battery) for a half hour to get some juice back in them before I tried out my new 2.90:1 gear ratio.  Now I knew this motor had more power than speed, but I didn't know it had this much power.  I slapped my Micro on the ground, gave it the gun and this time it took off like a rocket gaining tons of speed down my street.  I flipped around and flew back passing myself at lightning speeds.  This sucker was very fast.   I thought I'd lose some torque with the taller gear ratio but I honestly didn't notice any loss of torque, only massive amounts of top end speed.  This car rocks!  Especially with my newly outfitted front ball differential, I can power around corners at speeds I never thought this car could do.  It's so controlled and has gobs of power and speed, and this is running only 8 cells.  Exactly what the motor is designed to run all day long.  It still stays cool as well as the batteries.  

I can only speculate on taller gear ratios and more cells, but I do believe that this motor still has the potential to drive a taller gear as well as handle more batteries.  Like I said, it seems to be plenty powerful with a 20T but if you add added 2 more cells, the motor would still have more power, which would allow you to run maybe a 22T pinion would yet again improve the top end.  I only wish my ESC could handle a couple extra cells, or I would do it.    Another benefit of going to a larger pinion gear is you don't really need to shave so much of the diff housing.  In fact you might not have to shave it at all.  And if you're running a 150mm wheel base, I bet you don't even need to do the rear deck mod like I did.  But the lowering washers is a must because the motor can is so much larger that even with a highly shaved motor mount, the 2.5mm screw holes for the motor won't line up right.   I definitely recommend this setup for anyone who doesn't mind cutting up some plastic parts and seriously wants a hilariously fast Micro.  Not only that, but it's so cheap.  The motor is $10, the gear is $4, and well, what's a couple of batteries to throw on the fire?

More pics: 380 motor, 140mm WB and the larger 20T pinion.

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Specs of Various 380 (400) Sized Motors and a Speed 300 for Comparison
Motor Model Const. Cur. Res. Nom.
Speed 280 6V 6328 2333 .275 .8820 6 14.0k 8.4 1.25 15/16 2.0 1.5
Speed 300 6V 3306 4833 .700 .2140 6 29.0k 8.4 1.25 15/16 2.0 1.8
Speed 400 7.2V 1794 2227 .720 .3570 8.4 18.7k 12.0 1.5 1-3/32 2.3 2.5
Speed 400 6V 3321 2672 .890 .2540 7.2 19.2k 9.6 1.5 1-3/32 2.3 2.6
Speed 400 4.8V Race 3320 4492 1.72 .1110 6 26.9k 9.6 1.5 1-3/32 2.3 2.6
Rocket 400 6V 780 4013 x x 7.2 28.9k 9.6 1.5 1-3/32 2.3 2.6
Watt-Age 380 for gearboxes x 2321 x x 8.4 19.5k 10.8 1.5 1-3/32 2.3 2.6
Super 400 Watt-Age 380 for direct drive x x x x 8.4 x 10.8 1.5 1-3/32 2.3 2.6
Promax 400 7.2V-8.4V x 2253 x x 8.4 18.9k 12 1.5 1-3/32 2.3 2.6

Here is my interpretation of the above chart.  Free RPM is measured at the Nom. Volts spec only.  This is not a maximum RPM spec.  To calculate maximum RPM, multiply the volts you wish to run by the Const.  (which stands for constant which is interpreted RPM's per Volt  - RPM/V).   A Speed 400 7.2V motor on 12 volts will have a Free RPM of 26,724.  It may or may not actually spin that fast, because sooner or later you reach the physical limits of the motor and no amount of voltage will make it spin any faster.  But generally speaking it can give you an idea of how fast that motor is spinning given a certain number of cells.

The Maximum Volts column is derived from either adding 2.4V (2 cells) to the nominal operating voltage, or from other data sheets that rated the motor to handle such number of cells.  In other words, I am not certain of their maximum cell carrying capacity or for how long the motor can be expected to live while running the maximum number of cells.  Put it this way, the number of cells you use is inversely proportional to how long your motor will last.  In most cases with these motors, the rated nominal voltage is not the maximum voltage that the motor can handle, but the voltage at which the motor is most efficient.  You have to think in terms of model airplanes when looking at these motors.  Flight time is a critical factor, because who wants a plane that only flies for 6 minutes before the batteries die?  But for RC buffs like ourselves, we don't care so much about efficiency as we do raw speed and power.  Which is why all these motors can be pushed beyond their nominal voltage rating with a relatively good safety margin.  An 'x' means no data is available.  

Two other very important numbers to look at are Cur. (current) and Res. (resistance).  These numbers indicate how many winds per arm of the armature, as well as the gauge of the wire, which will in turn clue you in on how much torque versus speed the motor has.  A Speed 400 7.2V has thinner wire and more winds than a Race 4.8V motor, which means it will spin slower but has lots more torque.  Conversely the 4.8V Race motor will spin a lot faster because it has a thicker gauge wire and fewer winds per arm, therefore drawing more current resulting in maximum RPM's but with much less torque.  This is important because the gearing has to match the motor.  A 20T pinion on a 4.8V Race motor is horribly slow and burns up batteries in minutes.  However that same motor on a 14T totally screams.  But a 400 7.2V motor on a 14T would be a tank, have no speed and your batteries would probably last into the night.  But that same motor on a 20T is an absolute speed machine.  And then as with any motor/gear combination, if you increase the voltage you get an increase in speed and torque together.  Which is the most obvious benefit of lots of extra juice!

I will be updating the above table to reflect new information on new motors as it becomes available.  In the meantime, stay posted for other fascinating updates and hang out at the YourMicro forums to gain some wisdom.

Trinity "Monster Horsepower" 540 Motor Installation

Stop by www.danmarx.org/micro/540 for details.

Hitec HS-81 Micro Servo

Bottom line - the plastic one is junk.  Okay, okay, so I got the plastic one and everyone said not to but I did and sure enough, all the teeth on every gear was stripped by the end of one run.  Junk.  This servo is not meant to turn the wheels on an RC car obviously.  Before the gears stripped however, I had major issues with it not centering.  I'd set the trim, the car would go straight, then after one or two turns it was veering to the right again.  So I'd tweak the trim so it was straight and then flip around and the car was now veering to the left.  I couldn't get it to return to center once after cranking it to the left or to the right.  It always sat just left or right of center.  So the car never went straight.  Then after a few small crashes and bruises, the servo quit working all together.  Now I've got my old S3003 in there and it works like a dream.  Centers every time for perfectly straight runs and takes more abuse than you can shake a stick at.

Ratzas Pro Pan Chassis

Well my car was going plenty fast after I'd upgraded just about all the moving parts I could afford.  It was time to do some chassis mods.  The Ratzas Pro Pan suited me perfectly because it allows me to use my 140mm wheelbase, it looks freaking awesome, and it's priced about midway between an ARM chassis and a Team Epic chassis.  One of my main reasons for going to a pan-style chassis was  I needed a place to put all 8 of my new 2/3A batteries.   You can't fit 8 batteries on that "battery holder thingy" HPI gives you with the kit.  It just won't happen.  This chassis is awesome.  It truly was engineered with some thought and intellect.  It's very light, very rigid (and yet still flexes ever so slightly), and the provided servo mount worked like a dream.  All the screw holes are recessed plenty deep for flush mounting of every screw.  All my stock parts fit perfectly.  One thing I actually like about this chassis is that with the stock shock, they've actually loosened up some of the tension on the belt.  It's almost like they made it 139mm instead of 140mm.  Now when I push the car across the ground, it feels more free and loose, less friction, and the car rolls for several feet almost uninhibited by the spinning of so many moving parts.  This is without the motor attached obviously.
When it came down to placing the electronics, I thought long and hard how I wanted to do it.  I knew I wanted everything on the chassis and nothing on the upper deck.  I wanted to get rid of the upper deck all together.  I also wanted the batteries symmetrical and balanced along with the ESC and receiver.  After fiddling around with a few different ideas, I came up with this one, which I believe to be the best way to do it.  The ESC up to the left of the servo.  Two batteries just behind it.  3 batteries right down the middle, and three more on the right side only separated by the belt running between them.  The receiver is mounted on top of the 3 batteries running down the middle and that's that.  Since I don't have a digital camera of my own (yet) I sketched out this drawing showing the parts placement.  Click here to see my pan chassis.

panchassis_1.gif (13640 bytes)

I also show the wiring scheme of the 8 cells.  I used a good 40 watt soldering, and some 14 gauge wire to make the proper connections and a Tamiya plug to finish off the job.  I used 3 strips of Velcro to hold the batteries to the chassis and a piece of servo tape between exposed opposing battery terminals to avoid shorts.  I would like to get some stiffer springs or X-shocks for the front because with all the weight of the batteries, it sags just a little bit.  It's not an issue for now, but I will eventually want to get something better up front. 

After I put nearly a full charge into my batteries, I couldn't wait to see how she would perform.  Unfortunately for me there aren't any street lights here in good ole Tucson, so at 10:00 at night,  it's pitch black outside.  So I pulled the cars out of the garage and resorted to driving up and down my driveway and in and out of the garage and tried not to let the temptation of jumping 14 feet off the curb overwhelm me.  My first impressions of this new setup is...this car is going to be fast...very fast.  The handling feels great, much better than with the thin stock chassis.  With all the weight evenly distributed and the CG point so low, you can really feel how well it rides in how smooth the car handles.  It's much tighter and cleaner now.  I think there is some steering slop I need to work on.  This is the first time I've used my HS-81 servo and so far I can tell it's quite different than my S3003 I was using.  Honestly I liked the S3003 better.  It seemed to control the car better.  With the little HS-81, it sometimes feels like the car is controlling it.  

But let me talk about the speed.  It never runs out of it.  It is so fast, that I can only keep it on full throttle for a single second and then I'm forced to lighten up.  The wheels just scream when I hold the car in my hand.  The rotational energy is so much that you can see the inside of all four tires widen as much as the rubber will allow them to stretch, even with both the inside and outside edge of the tires glued to the rims tight.  As compared with my clocked 27 MPH, I would honestly calculate this up around 40+ MPH.  You may think I'm crazy and just making stuff up, but I'm not.  I truly believe it to be that fast.  All four wheels can break traction at almost any given moment and any given speed.  I think a 14T is perfect for this kind of setup.  With the 8 cells, the motor has so much more torque than with just 5 or 6 so the taller gear ratio is no problem for it.  Being that this is the highest standard feasible gear ratio for a Micro (without other mods), I think this is the optimum choice, especially for anyone who wants top speed out of their Micro.  More to come...

Watt-Age 370 Mabuchi TD22223 Motor

Running 8 AA batteries to a Speed 300 is just about enough to burn out the motor.  Or burn up a cheap set of Ni-Cad batteries.  One or the other,  I'm still not sure.  But when my car quit running last month, I blamed the motor, and only after I tore the whole thing to pieces did I find out that it was actually the batteries at fault.  My mistake, well maybe.  It's still up for debate.  So as an alternative to the infamous Speed 300 I picked up a motor sold by Watt-Age (very popular in the R/C plane world) called the 370.  There have been a few discussions about this motor and its origin being very similar if not identical to the Speed 300 which is sold under the company Graupner.  From the looks of the two motors they are absolutely the same all the way around.  Call them identical twins, if you will, separated at birth.  Can size, length diameter, shaft are all identical.  The holes and individual markings are also identical.  All the way down to the back plate on each motor has a unique gridded pinhole appearance to it.  Identical on both.  Solder tabs, same.  Red polarity marking, same location exactly.  Both motors are stamped Mabuchi and are made in China.  The only difference lies in the labeling on the stamp.  The Speed 300 says Made in China 5A and  the Watt-Age 370 says TD22223.  It could be that they left the actual model number off the Graupner Speed so that it could be sold under a different label as different motor.  Watt-Age may not have cared to have the original Mabuchi model number on there so they left it.  Possibly to try and distinguish the two motors and set apart the "labeled" one from the non-labeled.  I probably don't have to mention that many people have figured out the the Speed 300 is the same motor as the even more expensive Team Orion Big Block (280BB).  So suffice to say that if this motor is the same as the Speed, than this motor is also the same as the BB.

So later on the next day, I've got the Watt-Age 370 installed and ready to go.  I went back to my 8 cell, 7.2V AAA pack because I pretty much destroyed my 8 other ones.  But that's another story.  The reason this pack is only 7.2V is because they are smaller batteries and don't have enough juice to actually provide a full 9.6V to such a power hungry motor.  So we'll just say it's a 7.2V pack.  I turned everything on and gave the motor a few whirls with the trigger.  Oooooh.  It sounded nice and it sounded fast.  I set the thing on the ground a let her go for a ride.  It took off like a rocket spinning all four tires on concrete, flew across the street jumped up the neighbor's driveway doing summersaults and lands back on all four tires.  I drive it back around to me and said to myself, "Now that's a fast motor."  So my conclusion is this - the two motors are the same, and both provide an excellent improvement over the stock HPI motor.   I couldn't tell a difference between the Watt-Age 370 and the Speed 300 in any way.  They both provide excellent top-end speed and ample amounts of acceleration for any professional race or for just driving around the garage.  You be the judge.  Honestly though it's only a couple of bucks.  Get whichever one you want.  They both are excellent motors that will fit in your stock chassis and can make your car go at least 27 MPH.  

Oh and one other thing, the Watt-Age 370 is designed to operate with 8 cells.  Yes it's true.  This is a real 9.6V motor.  Don't believe me?  Read the instruction manual for the Watt-Age Crazy Max EP airplane.  It comes with a 370 motor and they recommend an  8 cell battery pack.  Enough said.  Now quit bellyaching and whining about your "super slow 4-cell alkaline-driven Micro" and get with the program.

TSH Super 400 (Wattage 380 for direct drive) Motor Installation and 16T Pinion

My Micro was plenty fast.  Almost too fast, but there is that need for speed that drives us all.  I wanted to go faster.  I was at a local race the other night and saw what a 1/10th scale modified touring car could do and it completely blew me out of the water.  Those suckers are very, very fast.  These micros don't even stand a chance.  Now as compared with the stock class, a modified micro can barely just keep up.  So that's when I decided to pop in a 380 sized motor into my little micro.   I wanted it to be fast, very fast.

A Wattage 380 can be picked up at most Hobby stores for about $10.00.  You can also get it at Hobby People.  Specs on the motor are no where to be found.  Generally speaking though, they fun fewer RPM's than a Speed 300.  But with the more power available, you should be able to get away with a taller gear ratio to make up some speed.  The shaft diameter on this motor is somewhere between a stock HPI motor and a standard pinion for 540 sized motors.  Which means it takes some modifications to get a pinion on there.  So this is how it's done.  I bought a piece of 1/8" brass tubing (also available at your LHS).  The inner diameter (ID) of the tubing fits just around the outer diameter (OD) of the shaft on this motor.  Then the OD of the 1/8" copper tubing fits just inside the ID of a  standard pinion.  So there you go.  Pinions sizes from 8T-28T right at your finger tips.  

Now I used a 16T aluminum pinion because it was just a bit larger than the 14T that my Speed 300 was running but it didn't require me to shave off my entire rear differential housing.  But I did have to shave quite a bit, almost too much.  I would say that a 16T is as small as you can safely go with this motor.  I think I may have even preferred a 17T.  Any higher though and you'll sacrifice power for top-end speed which may never be reached because of friction and weight.  There is a good balance there somewhere.  All you can do is try a few out and see what you like.

I had to modify the motor plate that I got with my Speed 300 by enlarging the shaft opening by just a few millimeter toward the front.  The screw holes I shaved just a little bit as well.  Then the new motor screwed right it.  Use 2.5mm screws.  I used 4-40 and re-threaded the screw holes in the motor (only because I bought the wrong kind, twice, and didn't want to drive back to the hobby shop).

With this motor in a stock 140mm chassis, the rear deck doesn't fit anymore.  So I didn't even put it on.  I just rested the upper deck on the motor and used zip ties to hold it down.  Then I zip tied my extra 2 cells to this same location, just above the motor.  That means now I can't install my body.  Which I hate driving my micro without the body.  Too much stuff breaks.  And with that, the sucker is installed.  I'm charging the batteries right now and may pick up 9 2/3A or AAA batteries this afternoon.  This motor is voltage hungry!  7.2V does nothing to it.   Even with 9.6V it runs very cool.  It needs more power.  I would guess that even 12.0V (10 whopping cells) would be just enough to get this puppy going.  Stay tuned.  The pictures below aren't all that great, but they show the current set-up.

super400motor.jpg (7302 bytes)     super400_1.jpg (59942 bytes)     super400_2.jpg (59344 bytes)     super400_3.jpg (61925 bytes)     super400_4.jpg (59552 bytes)     super400_5.jpg (54835 bytes)

Just to make a note, this motor is not your regular 380 motor that most people talk about.  The 380 that most people have (I think anyway) is the Wattage 380 for gear boxes.  Hobby People has this motor as well.  I plan on buying this motor sometime soon if I don't like the outcome of this Super 400 motor.

Conclusions:  In the end I'd have to say that this motor is a poor choice for Micro RS4.  Due to its vary large can, voltage hungry windings, and overall low RPM's, it just doesn't perform as well as some of the smaller and lighter motors available.  Don't get me wrong this motor is fast, much faster than stock but it needs lots of voltage to get there.  A Speed 300 on only 6 cells is just as fast as this motor running 8.  The only pinion I used was a 16T so there may be more speed in there if you used a larger pinion.  It surely didn't seem to run out of torque with the setup I had so a taller gear ratio is certainly feasible.   Any way you look at it though, you need to have a modified aftermarket chassis and a 150mm wheelbase to fit this motor comfortably in a Micro.  Get a Watt-Age 370 or a Speed 300 before you try messing with this so-called faster 380 sized motor.

GH Ball Diff

With hopped up motors, the stock differential usually won't last more than a few runs.  I decided to pick up a GH front ball differential hoping it would solve all my differential woes.  But it didn't.  At first this unit seemed like a fine little piece of work.  Till I realized that the thing slipped like crazy.  It was like I was in 2WD all the time.  I couldn't get any power to the front wheels.  So I pulled the thing apart to inspect the insides.  Everything looked okay, but I noticed a major flaw in its design - there is no friction adjustment.  That's why all the slippage.  The problem is that this differential uses the tension of the stock front lower bulkhead bearing rings to hold it together.  The little rubber washers inside the diff are suppose to provide the tension to create enough friction for minimum slippage but they just don't squeeze together hard enough.

The solution?  Install one more metal washer inside the differential between the bearing washer and the rubber washer.  This adds about 0.5mm to the length of the diff so when it's crammed into the front lower bulkhead unit, there's a lot more pressure pushing against the differential plates.  The problem with doing this is that it puts pressure on the bearings as well so they tend not to want to spin.  That's why it's crucial to install a washer that's thick enough to make the diff work, but not so thick that the diff doesn't spin smoothly inside the housing unit.  Experiment with different washers till you find one that works, and believe me you can get it to work.  My GH ball diff works like a dream now.  Rotation is smooth, and power gets to the wheels like it's suppose to.  

Graupner Speed 300 with 14T Pinion

The first hop-up part was  I purchased was the Graupner Speed 300 with the accompanying motor plate.  I bought both pieces for $19.99 from www.teamspeedster.com.  They shipped the stuff out the within a couple of days, sent it priority mail and 2 days later the motor arrived in my mail box.  Pretty dang good service.  Now despite what everyone says about this motor not fitting in a 140mm body, they are wrong.  I fit this motor in my Civic with very, very little modding.  I don't have picks of my car, but I do have pics of someone else's car whose idea I used and it worked perfectly.  Basically you need to add 2 nylon washers to the upper deck mounting posts so that there's more room underneath for the motor.  Then you need to shave off about 1/16th of an inch off the tail end of the upper deck.  See images below...

moddedupperdeck.jpg (21078 bytes)     washersdeack.jpg (35904 bytes)     150mmspring.gif (41706 bytes)     modspringmount.gif (37445 bytes)

I moved the rear shock from the 140mm hole to the 150mm hole and then cut the spring about 2/3rds and left just enough so that the spring is still compressed when mounted.  This way the shock stays almost stock and allows room for the bigger motor to fit underneath it.  

The last thing you have modify is the differential housing.  I was able to fit my stock 13T pinion onto the motor by just barely shaving away some of the edge of the diff housing where the motor was hitting it.  You just have to look and see where it needs shaving.  I've heard that with 14T and larger pinions you don't need to shave the diff housing, but it's a small chore and can be easily accomplished with only a razor blade.  I like the added speed of the 13T over anything smaller.  There are no other modifications that need to be made!  That's it and now you too can be flying with a Speed 300.

After I installed the Speed 300, I was very anxious to see how this puppy was going to perform.  I drove to a high school nearby that had a huge lit up parking lot and took it out for a spin.  WOW!  This thing is hysterically fast.  I don't think people actually realize how fast this car car when they say it does 25-30 mph.   That figure means absolutely nothing.  The car goes so fast you lose sight of it in seconds.  My ATV on my steering has to be set to '1' so I don't crank the wheel so hard the car just spins out.  The car is fast.  It is very fast.  So fast it becomes difficult to control.  Almost impossible at times.   

I recommend the Graupner Speed 300 to anyone whishing to break the scaled sound barrier and go faster than this car was really meant to handle.  But be prepared to by new parts soon.  My front differential is is totally blown.  One of my front universal dogbones broke into several pieces while the other one broke and flew off into oblivion.  My tires all all shredded into bits.  My rims are bent and torn.  My pinion gear stripped off the motor shaft.  And my servo will not stay down no matter how much tape and glue I use.  So was it worth it?  You bet!  I've got new dogbones and aluminum pinions on the way and I'll be getting a new one-way aluminum differential just as soon as I can.  I also want to get a ball diff for the rear, but my rear differential has actually held up so far.  I'm running a plastic pinion on my plastic stock spur and although they are getting torn up quite a bit, I should be okay for a few more hard runs before getting new ones.

So with that said, stay posted for cool  new pictures of all the latest hop-ups.

Click here for the Ultimate Hop-Up Heaven Drool Page.  By GPM especially for Micro RS4.




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