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  1. #1
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    Spur gear question

    So I got a few tanks through it today with the new axles and drive shafts. Ran great. But. There's always a but in these posts. About mid way through the fifth tank I started hearing a gear whine and by the time I got it back over to me the spur gear was destroyed. My question here is. If it made it throughout 4 or 5 tanks of hard, high RPM bashing, did I have it set up wrong or did it maybe suck up a rock or some thing
    Desmosedici RR

  2. #2
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    Mesh could of been to close or slipper to tight?? A hard hit with rev's high on landing with slipper to tight will do it..

  3. #3
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    The slipper was set very tight! Think that was it?
    Desmosedici RR

  4. #4
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    It could have been too tight. Was your engine mount loose by anychance

  5. #5
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    No. I checked before I took it apart and it didn't look like any thing had budged. I'm betting the gears got a small rock in between then them. It happened so quickly! I'm guessing it would be a little better to have the gears set ever so slightly to the tight side rather than looser? How much play should there be?
    Last edited by Redvegasgt; 01-12-2013 at 09:34 PM.
    Desmosedici RR

  6. #6
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    You should be able to hold one and wiggle the other a little, just a very small amount of wiggle though. I doubt a rock got jammed in between the gears, it could happen, but if the body was on (not sure) it's hard for something to squeeze its way in there. If the slipper was too tight, that is most likely the cause. Check to make sure you have all eight motor mount screws still, and that they're all tight. You'd be surprised how two being a little loose can affect that just enough to strip the gear.

  7. #7
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    The slipper was set for NO slip. I think I had the mesh set great. I could hold the gear on the clutch bell and just bearly jiggle the spur gear. There was maybe 1/4 to 1/2mm of play I'm estimating. With a lightly snugged engine mount (to tight to move by hand but was able to tap it with a pin punch and a tack hammer for very small movements) I put them together tight initially (so there is obvious binding) and then backed the lash off just enough so the gears would spin freely. At that point I checked the play and had 1/2 to 1/4mm. I then tightened the engine mount in an X pattern and rechecked the lash. All good! Is there a better way?
    Desmosedici RR

  8. #8
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    FOUND IT!!!! Here's what I think was happening! I think the bearings on the clutch bell were coming apart causing more and uneven clearance during running. After putting the new spur gear in last night and very carefully checking the lash and the alignment I took it out again today. Ran great for two tanks, carefully listening for abnormal noise and checking wear after half a tank and on refuel. After refueling I did a play check again and all was good. I did notice a very slight amount of runout in the clutch bell. I tried wiggling it and it seemed to have no play. So I fired er up and off I went. After about a quarter of a tank I brought it back in to check and did notice a little wear on it. I also noticed a little drag. I gave it a spin with my finger and it locked up solid! At that point trying to turn the spur gear would turn the engine over. Brought it home, tore it down and poured the bearings out of the clutch!
    Desmosedici RR

  9. #9
    RC Turnbuckle Jr. Wildman4910's Avatar
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    AvidRC! At $1 each you can afford to chuck the CB bearings at the first sign of roughness in them.
    Look out for the tree/crunch!

    LiPo? Naw NITRO!!

  10. #10
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    @Wildman4910 Great Info that is Dirt Cheap heck buy yourself 10 sets and it would cost you about what 2 sets would from a local Hobby shop or online with shipping.
    Are those by chance the ones with the Teflon cover of sorts over the bearings or do they have the metal covers? Not that it matters a whole lot at that Price just curious as I got a set with some Teflon type covers and some with Metal covers.
    although I have not had to change mine in a bit since I soak them overnight in a Mixture of White Lithium grease and Marvel Mystery Oil. It is a Nice goo I made up a while back I soak all my bearings in overnight before installing them. DId that to Tranny, Wheel Bearings (axle Bearings on the 3.3) and the Diff bearings. 'Of course I am a grease/oiling nutcase its something I learned back doing PM on CNC Lasers and Diesel Semi's etc.
    I probably Over clean and grease everything on my Traxxas T-Maxx but Oh Well lol.
    BTW v@Redvegasgt The way you explained setting your Spur Gear free play with a Pin Punch and Tapping it is exactly how I set mine and have yet to strip one.
    I set it to have some binding then just a tap to lossen it I usually can get it to have no Binding and spin freely (the Spur Gear and CB) when spun backwards yet have almost no Free play when holding CB and moving Spur gear.
    I have been really happy with this Type of adjustment and could never NEVEAR seem to get it correct trying the paper technique always felt like i had way to much free play between them with teh paper method.
    Still running the same 62 tooth Spur I finally switched over too after removing my custom made 72 tooth one.
    T-Maxx 3.3 :)

  11. #11
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    @wildman4910 I cannot remember what Size those bearing are exactly according to the Engine Exploded View they state
    5X11X4 I assume for the 4120,4122,4124 (20T,22T,24T) CB's and 5X10X4 for the 4118 (18T) CB and 5X8X4 for the 4116 (16T) CB. Since I use currently the 4120 I should get a couple of the 5X11X4 but I want to try a 4118 so I should get a couple of the 5X10X4 and more then likely get a few of the 5X8X4 ones also as I may sooner or later try a 4116 CB also.
    I guess I kinda answered my own question but I figured it may be helpful to have the Sizes posted for others possibly thinking of using some of teh above mentioned CB's at some time or another.
    T-Maxx 3.3 :)

  12. #12
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    Well the 5X10X4 and the 5X11X4 they show at $1.00 each and I added 4 of each to cart but cannot seem to find the 5X8X4 Size needed for the 4116 CB.
    With USPS Shipping being only 3.64 thats not actually to bad of a shipping price but I think I should add a few more bearings or at least until the Shipping price goes up drastically.
    wow when I added 20 of each the USPS First class became Free and the Priority dropped to $4.90 Great deal from what I have found for Parts.
    Thanks again.
    Last edited by spudler_t; 01-14-2013 at 03:49 AM.
    T-Maxx 3.3 :)

  13. #13
    RC Turnbuckle Jr. Wildman4910's Avatar
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    Yup they are great, I use the metal shielded for the CB & either rubber or revolution for everything else.

    Don't forget the 5x8x2.5mm, 2 for the throttle bell crank, & 2 or 4 for the steering depending on what model maxx you have.
    2 for the 4908/07 steering bellcrank, 4 for the 4910/09 steering bellcrank.
    Look out for the tree/crunch!

    LiPo? Naw NITRO!!

  14. #14
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    @wildman4910 Hey Thanks for the reminder, I have 2 in the Throttle at the moment which seem to be great and last Quite well, and I have the (well I have a Frankintruck of sorts) It was Told to me by Prior Owner he upgraded everything to the 3.3 Model Except the Engine (still have a 2.5) and I found the Diffs were 2.5 but now are Sealed 3.3 with the Silicone in the Spiders.
    I do have the 3.3 Style Steering with the Double Sheer or whatever it is called Setup and have the Spring with the 4 Ball bearings on the Steering instead of the 2.5 Style which I have a Truck with that too.
    T-Maxx 3.3 :)

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