Results 1 to 10 of 10
  1. #1
    RC poster
    Join Date
    Jul 2004
    Posts
    8

    Brass shaft and wire burn

    Hey everyone,

    Well i have been out of the hobby for awhile but just got back in with a spartan.

    I wanted to ask a question

    Has anyone seen the brass shaft and wire heat up / burn?

    I have a stock spartan with (2) Duratrax Onyx 8000mah 3s 11.1v lipos - after running the boat i started hearing some odd noises so i brought it back in.

    After tipping the boat the water sizzled as it cooled the brass shaft. It seemed to be HOT.

    I didnt notice a hot motor, batteries or esc... just that brass tube which is now discolored.

    I just wanted to get some input and see if anyone else has seen this happen?
    "Nothing like a flying 4-Tec"

  2. #2
    RC Qualifier
    Join Date
    Feb 2012
    Location
    Montreal, Canada
    Posts
    564

    Brass shaft and wire burn

    It happened to me, that means your brass and drive wire had a mis-alignment, take it off and check it, you need to put grease inside of it or else it will be the same thing that will happen next.
    Sharing is the best thing to do on EARTH legally.

  3. #3
    RC poster
    Join Date
    Jul 2004
    Posts
    8
    thanks i appreciate it - not really sure how to see the alignment as none of it is straight. Ill do some looking though.

    Thanks
    "Nothing like a flying 4-Tec"

  4. #4
    RC Qualifier
    Join Date
    Jun 2011
    Posts
    962
    This is caused by excessive friction between the flex drive (cable) and the stuffing tube.

    There are a few things that can be responsible for this problem.

    1. Lubrication: it is important to remove the flex drive and clean, inspect and lubricate it. Every two runs is what most Spartans owners find is recommended, but with 8000 mah batteries your run times are long enough you may want to consider after every run.

    2. Torque Twist: under load the flex drive will "twist" or "corkscrew" a bit which causes it to shrink a bit in length. Be certain to leave approx. a 1/8" gap between the strut and drive dog when you install the flex shaft.

    3. Strut Alignment: Having too much positive or negative angle on the strut can cause excess stress on the flex drive. No more than 1-2mm positive or negative strut angle is recommended. (see owners manual)

    4: Damage: Kinked or frayed flex drives can easily result in friction damage. (i.e. clean, inspect, lubricate often)

    5: Certain mods like larger props, or higher kv motors can increase the stress on the flex drive upgrading to a larger .187 flex drive, or to a .078 wire drive can help. NOTE: prop upgrades and motor upgrades also increase load on the ESC and can result in premature failure of the ESC as well.

    6: Running Conditions and Driving Habits: running hard in rough water (i.e. wave jumping) can be hard on the flex drive. when the prop leaves, and re-enters the water the torque energy in the flex drive loads and unloads hard. This can be the start of damage to the flex drive. Occasional jumping of a wave is normal, continuous wave jumping can be bad.
    Constant hard on/off the throttle, or rapid forward to reverse can also be hard on the flex drive.

    Other: there is a teflon liner in the stuffing tube that helps reduce friction and eliminates metal to metal contact. Liners are not absolutely necessary, a well maintained and lubricated flex drive will last a long time without a liner, but they are helpful. Be sure to replace the liner if damaged as well.

    Welcome to the forum, and have fun with the Spartan.

    hog

  5. #5
    RC Qualifier
    Join Date
    Feb 2012
    Location
    Montreal, Canada
    Posts
    564
    The brass tube is not straight, it's a bit bend, mostly on that curve the wire drive makes a friction, and that's the one that happened to you, so thing is drop it with a small amount of dry lube before putting the grease and see what will be the result, check your drive wire too there might be some stranded wires.
    Sharing is the best thing to do on EARTH legally.

  6. #6
    RC poster
    Join Date
    Apr 2014
    Posts
    9
    I broke another flex cable yesterday. I ran Traxxas 5800mAh 2s about 8-10 minutes, then ran Traxxas 5000mAh 3s about 3-5 minutes and flipped it trying to go too fast over some wake. After retrieving my boat I ran almost new SMC 6500mAh 70c 140c about 3-5 minutes and snapped another cable. This is 3rd time I've replaced stock flex cable so I have a back up but should I buy replacement stock or I've seen .187 mentioned? Also recommendations on running 4 trim tabs? Spartan appears to have places for screws but Traxxas did/would not recommend anything but stock. Comments/advise please. Steve

  7. #7
    RC Qualifier
    Join Date
    Jun 2011
    Posts
    962
    I upgraded one Spartan to a .187 flex, and the other to a .078 wire drive after snapping or twisting up several OEM stock, and aftermarket .150 cables.

    It is my opinion that the .150 flex shaft is marginal for a boat of this size and power (especially on 6S)

    Our lake was often a bit rough, and jumping waves is very hard on flex cables. The flex cable is "torqued up" when under load, and releases when the prop leaves the water, then "torques up" hard again when it hits the water.

    Occasional skipping over a wave or wake shouldn't be problematic, but lots of wave jumping, aggressive on/off the throttle, or quick alternations from forward to reverse can stress the cable.

    Since upgrading my boats, I have had zero drive line issues.

    As for trim tabs, yes there are bolt wells molded into the plastic to receive bolts for an additional set of tabs, or to relocate the originals. There is a thread over on the OSE Spartan Forum showing how to easily find the right spot to drill or punch the hull for install.

    Last season I ran one of my Spartans with no trim tabs or turn fins and my experience was it ran exactly the same without, as it does with two, or four tabs. You can pretty much use battery placement to do what trims do, which is to lift the stern, and push the bow down.

    Others have posted their experience is that the extra tabs help a lot.

    All you can do is try, and see what your results/experiences are.

    Hog
    Last edited by hog; 05-25-2014 at 02:04 PM.

  8. #8
    RC poster
    Join Date
    Apr 2014
    Posts
    9
    Thank you very much. OSE is currently out of stock on the upgrade kit that comes with .187 cable, coupler and strut with teflon bushings. I'm assuming stock propos will not work, or will they? Will I need to also replace the stock stuffing tube and liner?

  9. #9
    RC Qualifier
    Join Date
    Jun 2011
    Posts
    962
    All you need is a .187 flex with a Traxxas stub shaft on it, and a new motor coupler to accommodate the larger diameter flex.

    These are available from Jeff Wohlt at rcraceboat.com

    I run mine without the teflon liner (.187 won't fit with liner installed) Keep it lubricated and it won't be a problem. If the stuffing tube wears through one day, they are inexpensive and simple to replace on the Spartan.

    All the prop shafts for the Spartan should be sized to run a 3/16" diameter prop stub shaft. (standard prop sizing)
    The Spartan prop stub is actually 5mm stepped down to 3/16" to accommodate standard prop sizes.

    Alternatively:

    1- There is a stuffing tube upgrade that some have done to allow the .187 flex cable to run with a teflon liner. There are some good threads here on the forum detailing the mod.

    2- Go the kit route with new strut etc. I haven't investigated this option so I'm not certain what the benefit of changing the strut is. Teflon bushings I suppose??

    3 - Use a .078 wire drive and keep the teflon liner installed. (Also available through Jeff)

    Hog
    Last edited by hog; 05-26-2014 at 11:20 AM.

  10. #10
    RC Qualifier
    Join Date
    Jun 2011
    Posts
    962
    So I had a look at the OSE .187 upgrade kit and confirmed what I suspected.

    The kit changes the stub shaft to a standard 3/16" stub shaft.

    This is good in some ways, it opens the door to a wide range of "standard" sized strut options.

    BUT..... 3/16" is the same as .187, so the flex and stub shaft are the same diameter.
    This raises the question of how the flex cable is fastened to the stub shaft. Traditionally the stub shaft is drilled out and the flex shaft is inserted and then glued or soldered in place, but this wouldn't be possible if both components are the same diameter, unless the flex is somehow crimped or trimmed to a smaller diameter where it connects to the stub shaft.

    Also, inserting the flex cable through the strut would "wipe" all the grease off because the tolerance would be so tight. This is tricky even with the stock strut with it's 5mm inside bushing diameter.

    Just food for thought.

    Hog
    Last edited by hog; 05-26-2014 at 01:26 PM.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •