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  1. #1
    RC Racer
    Join Date
    Jul 2011

    Revo 3.3 budget brushless conversion, The Sequel

    This is a build thread inspired by reflexa's "Revo 2.5R budget brushless conversion" thread, as it uses the same electronics, but some different hardware, all of which anyone could buy or do.

    This is my buddy's truck that used to have a rotostart STS.28 (of which the entire BB conversion: motor, mount, clutch, pipe, etc. are for sale). There was nothing wrong with it other than the fact it was nitro and took a preparation to get going. He liked to just run it on a whim for a few minutes, but the effort (including post efforts) wasn't worth those whim moments, so it didn't get a lot of use. He saw my e-conversion (thread coming in a few weeks) and loved it but the cost was high. I told him I could do it a lot cheaper, so here we are.

    Here are the players:
    Integy motor mount, ********* SC120A ESC, ********* program card, HK S3674-2370 motor, FAN5010-3665 heat sink, Scorpion 300mm velcro straps, Losi SCTE battery tray, /xt60 connectors, TGY-1501MG servo (236 in-oz) servo, two 4s 20C 5000mah hardcase battery packs, 4mm bullet connectors, three M3x6 button head screws, three M3 hex nuts, 6" servo lead extension, Traxxas FOC, Traxxas p/n 5145 screw pins (not shown), three 6-32 X 1/2" screws, 18T Mod1 5mm pinion, foam strips (not shown). Not counting the shipping, this comes out to $280, for which about $45 was shipping.

    Ignore the Du-Bro parts

    Things to note:
    The Integy mount is only good for 36mm motors unless you do some mods to it. The SC120 "clearly" states that it is "intended for 4x4 short course or smaller." Reflexa burnt up his motor no long after installing it. I didn't believe and don't believe the torque specs of the servo purchased.

    1) All the nitro stuff was removed.
    2) Mechanical brakes were remove.
    3) The tranny was gutted of all reverse hardware.
    4) The 2nd gear lock was done.
    a) remove the grub screw, ball, and spring from the clutch. I then put the grub screw back.
    b) put the clutch back in the 2nd gear and extend the steel clutch tooth/shoe while installed
    c) take it out without letting the tooth move and add one drop of CA to hold it in place.
    d) put the clutch back in the gear (tooth against pin) and mark for the holes for the 3 screws
    e) use a Dremel tool to notch out 3 areas for the screws to pass the clutch and screw into the gear
    f) Cut the screws to .40 inches and install them.

    Robinson input gears shown were not put in this build.

    5) Use a 2.5mm drill bit to open the pin hole in the aluminum main shaft of the FOC.
    6) Use a 1/8" drill bit to open the to-be-threaded hole on the main shaft gear.
    7) Unless you have a lathe, place Traxxas 5145 pin in a corded drill [spins faster than cordless usually]
    8) Place the drill in a vice, turn it on full blast and use Dremel to cut the bottom 1.5 threads down to the diameter of the pin.

    9) Attach the gear to the aluminum main shaft with your modified pin.
    10) Rebuild the tranny, minus the large 1st gear.
    11) Shave some of the features off the bottom of the SCTE tray as shown below.
    12) Remove the passenger side servo.
    13) Flatten out the two tabs of the chassis next to the passenger side servo.
    14) Bend the long tab near the rear to be co-planer with the passenger side servo area.

    15) Drill where required and install the battery try with the M3x6 screws and M3 hex nuts.
    16) Install the single servo on the driver's side.

    17) Do ll necessary soldering and change of connectors.
    18) Install the motor mount, motor pinion, velcro straps, goo-down the ESC and add zip tie.
    19) I used the mounting tray that came with the ESC for the RX and put it on the front shock mount.
    20) Shave some of the heatsink fins to fit into the motor mount.
    21) Use the servo extension for the motor fan.
    22) I drilled out the fuel tank mount and made it into an antenna tube mount.

    Motor fan not shown because I crashed during a speed run and destroyed it. I'll have another tomorrow.

    23) charge battery
    24) Program ESC (autolipo, 3.2V cutoff, 0 drag brk, 100 brk, 0 punch, Prop Rev Lock out, 8% timing
    25) Hit 50mph

    Last edited by metoo2; 08-29-2012 at 01:13 AM.

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