Results 1 to 17 of 17
  1. #1
    RC Competitor
    Join Date
    Apr 2019
    Posts
    64

    Is the loose pinion gear still a thing?

    Thinking of buying a brand new xmaxx soon for my first 1/5 scale. Is the pinion heat coming loose issue still a thing and if so how bad? How do you fix that? Any recommended upgrades right out of the box?

  2. #2
    RC Champion Acidic01's Avatar
    Join Date
    Jul 2018
    Location
    beaverton oregon
    Posts
    1,572
    Quote Originally Posted by Bigtim29 View Post
    Thinking of buying a brand new xmaxx soon for my first 1/5 scale. Is the pinion heat coming loose issue still a thing and if so how bad? How do you fix that? Any recommended upgrades right out of the box?
    Just make sure pinion is tight or remove put some blue lock tight on and re tighten.

    The rpm oversized rear hub carriers are only thing you will need right away. As rear inner bearings will be first thing to go if bashing.



    Sent from my Pixel 3 XL using Tapatalk

  3. #3
    RC poster
    Join Date
    Jul 2020
    Posts
    17
    Yeah, still an issue, but an easy fix.

    Line your gears up, give the pinion grub screw a good crank, and then remove the pinion. Take a dremel or other rotary tool and put a divot in the motor shaft where the screw makes contact. I used a conical grinding bit to do this, but there's dozens of other attachments that can accomplish the same task. Reinstall as before, with blue lactate. This now allows the grub screw to sit "in" the shaft, instead of on top of it, preventing the pinion from sliding off.

    I went through 4 sets of pinions\spurs before doing this. Since doing it, I haven't had a single issue. The only downside is that you're likely locked into a specific brand of pinion gears. Not all brands have the grub screw located in the same spot in relation to the gear teeth.

    This makes me wonder...how many wrecked gears were blamed on the pin mesh system that were actually pinion gears coming loose?

  4. #4
    RC Racer
    Join Date
    May 2019
    Posts
    212
    I have 3 and have never had a problem. Blue loctite let set for 24 hours.

  5. #5
    RC Competitor
    Join Date
    Apr 2019
    Posts
    64
    Would another good way to do this is deemed the bottom of the grub screw to make sure it’s flat and not rounded?

  6. #6
    RC Competitor
    Join Date
    Apr 2019
    Posts
    64
    You using stock gears still @clubin

  7. #7
    RC poster
    Join Date
    Jul 2020
    Posts
    17
    I tried blue loctite for 24 hours, too. Still had issues.

    I should have added, in my case, I could visibly see the flat spot on the motor shaft tapered along the entire length, narrowing towards the end. I then verified this with calipers. It wasn't a lot, but expansion/contraction due to motor heat would simply push the pinion off over time, sometimes as little as a single battery run. My grub screw was still super tight after every failure, so I don't think it was backing off. I probably should have used a really fine-tipped paint marker to verify this, drawing a line along the pinion and over the grub screw. If the line wasn't straight, the grub screw loosened up.

    Prior to dimpling my shaft, I did grind it as flat as I could with the dremel, verifying it was actually flat, visually, and with the calipers. This probably isn't necessary if you were to just grind the divot.

  8. #8
    RC Qualifier Flux Capacitor's Avatar
    Join Date
    Jan 2012
    Location
    United States of America
    Posts
    783
    Quote Originally Posted by MikeBusch2 View Post
    This makes me wonder...how many wrecked gears were blamed on the pin mesh system that were actually pinion gears coming loose?
    Very good question that proves a point my friend.

    There is absolutely nothing wrong with the pin mesh system and I'm willing to bet that those that blamed the pin mesh system for their spur/pinion troubles and meshed manually didn't realize that the pinion walking on the motor shaft was the culprit alongside the fact that their motor walked in the cradle (because of the absence of the pins from meshing manually) which caused an oblique meshing angle that aided in the pinion walking again as well on the motor shaft.

    I never had a problem with the pin mesh system and I put a divot on the motor shaft anyway just because I know from experience it works.
    Last edited by Flux Capacitor; 10-01-2020 at 09:39 PM. Reason: Spelling.
    Sent from my autonomous device.

  9. #9
    RC Competitor
    Join Date
    Apr 2019
    Posts
    64
    Seems like the general consensus is put a divot in the flat spot of the motor shaft. Would making the bottom of the grub screw flat instead of rounded work well too? Also if the stock pinion and spur are meshed correctly, shouldn’t they be fine?

  10. #10
    RC Champion
    Join Date
    Feb 2020
    Location
    Canary Islands, Tenerife, Spain.
    Posts
    1,399
    Quote Originally Posted by Bigtim29 View Post
    Seems like the general consensus is put a divot in the flat spot of the motor shaft. Would making the bottom of the grub screw flat instead of rounded work well too? Also if the stock pinion and spur are meshed correctly, shouldn’t they be fine?
    Keep the grub screw as is. Try to use hard thread locker.

  11. #11
    RC Racer Nickerz's Avatar
    Join Date
    Jan 2016
    Posts
    233
    I never knew this was a thing until I saw this video the other week and I was surprised (skip to 8:30)...

    https://www.youtube.com/watch?v=2WjfzTkW0YE&t

    ...I bought my X-Maxx in March/April 2018 and I never checked my pinion and never had an issue but now that I know, I'd check it just in case. I've taken mine off and changed it with the speed gear pinion and then have put the stock one back on with no issues. Then again, I use blue (medium strength) Loctite Threadlocker and never had a problem...

  12. #12
    RC Qualifier Flux Capacitor's Avatar
    Join Date
    Jan 2012
    Location
    United States of America
    Posts
    783
    Quote Originally Posted by Nickerz View Post
    I never knew this was a thing until I saw this video the other week and I was surprised (skip to 8:30)...

    https://www.youtube.com/watch?v=2WjfzTkW0YE&t

    ...I bought my X-Maxx in March/April 2018 and I never checked my pinion and never had an issue but now that I know, I'd check it just in case. I've taken mine off and changed it with the speed gear pinion and then have put the stock one back on with no issues. Then again, I use blue (medium strength) Loctite Threadlocker and never had a problem...
    In that video he mentioned also that "reverse instantly" was an issue. He said: "Could you imagine people bumping the trigger by accident and just blowing the gear every time?"

    That sounds like two things to me are going on with this video he made.

    Firstly, he just ran it without checking over critical components that should be checked before every run, even if it is brand new and secondly, it almost sounds like his ESC was not calibrated correctly.


    One of the two possibilities was his fault as the ESC not being calibrated correctly can happen after an update or throttle input is adjusted through the Traxxas Link App. He still should have checked that too before running........so possibly a end user fault as well.

    So the pinion coming loose was his fault (not doing the routine check before running) and the ESC issue of it having reverse instantly instead of braking, points to a calibration issue or faulty ESC, with the latter (faulty ESC) being out of his control.

    In all fairness to his video, Traxxas really did make an engineering error when it comes to that grub screw securing the pinion to the motor shaft. You don't use a pointed grub to mate with a hardened flat shaft, hence the reason people either grind the grub flat or make a divot on the motor shaft if using the pointed grub screw supplied.

    I personally choose the second method of making the divot on the shaft because even if your pointed grub screw comes a little loose, it still prevents the pinion from walking on the motor shaft.
    Last edited by Flux Capacitor; 10-12-2020 at 09:53 AM. Reason: Spelling.
    Sent from my autonomous device.

  13. #13
    RC Racer Nickerz's Avatar
    Join Date
    Jan 2016
    Posts
    233
    I've seen a simple solution that all companies should practice which is simply make the pinion hole shaped to the motor shaft to match the flat part. If the set screw comes loose, the pinion gear is still secure and the pinion won't spin, everything locks up so you can't turn the gears to metal dust. I think this is how it works and I think I saw this with an Armor car but not sure. Made perfect sense to me unless they have some patent on it - lol!

  14. #14
    RC Qualifier Flux Capacitor's Avatar
    Join Date
    Jan 2012
    Location
    United States of America
    Posts
    783
    Quote Originally Posted by Nickerz View Post
    I've seen a simple solution that all companies should practice which is simply make the pinion hole shaped to the motor shaft to match the flat part. If the set screw comes loose, the pinion gear is still secure and the pinion won't spin, everything locks up so you can't turn the gears to metal dust. I think this is how it works and I think I saw this with an Armor car but not sure. Made perfect sense to me unless they have some patent on it - lol!
    But you are missing the part that even if the pinion shaft hole was shaped like the motor shaft, the pinion still has the ability to walk up or down the motor shaft when the pinion grub screw loosens just a little.

    With a divot on the motor shaft, the pinion cannot travel up or down the motor shaft even if the grub screw works a little loose and gives you that extra time to catch it before it becomes a real problem.
    Sent from my autonomous device.

  15. #15
    RC Champion
    Join Date
    Feb 2020
    Location
    Canary Islands, Tenerife, Spain.
    Posts
    1,399
    Quote Originally Posted by Nickerz View Post
    I've seen a simple solution that all companies should practice which is simply make the pinion hole shaped to the motor shaft to match the flat part. If the set screw comes loose, the pinion gear is still secure and the pinion won't spin, everything locks up so you can't turn the gears to metal dust. I think this is how it works and I think I saw this with an Armor car but not sure. Made perfect sense to me unless they have some patent on it - lol!
    This feature is called "D" shape.

  16. #16
    RC Champion grizzly03's Avatar
    Join Date
    Dec 2014
    Location
    Adirondacks
    Posts
    2,273
    Quote Originally Posted by Flux Capacitor View Post
    But you are missing the part that even if the pinion shaft hole was shaped like the motor shaft, the pinion still has the ability to walk up or down the motor shaft when the pinion grub screw loosens just a little.

    With a divot on the motor shaft, the pinion cannot travel up or down the motor shaft even if the grub screw works a little loose and gives you that extra time to catch it before it becomes a real problem.
    I agree. The pinion walking is the reason gears are being destroyed. If the gears are not getting stripped while the set screw is holding (even under 8s power) how could they strip when the set screw is removed? When that pinion moves you lose that full tooth contact, so now 1/2 a gear tooth or less gets all that torque applied to it.

  17. #17
    RC Qualifier Flux Capacitor's Avatar
    Join Date
    Jan 2012
    Location
    United States of America
    Posts
    783
    Quote Originally Posted by grizzly03 View Post
    I agree. The pinion walking is the reason gears are being destroyed. If the gears are not getting stripped while the set screw is holding (even under 8s power) how could they strip when the set screw is removed? When that pinion moves you lose that full tooth contact, so now 1/2 a gear tooth or less gets all that torque applied to it.
    Just to add to what you are pointing out - it isn't just the pinion walking that is causing all the problems. To clarify, I will stress the importance of the pin mesh system. When a person manually meshes their stock motor on the X-Maxx, they run the risk of having an oblique mesh angle because the forward and aft part of the motor cannot be set exactly the same distance from the spur.

    This results in an oblique or off skew mesh angle between the pinion and spur that is not noticeable with the naked eye. The results are visible though over time on the pinion or spur, as one will see rounded edges on the long axis of each tooth instead of them remaining straight cut on the edges.

    Believe it or not, that can cause a pinion to walk as well.

    The pin system is more accurate because it aligns the motor equally front to back thus causing the pinion and spur to mesh at the correct angle or a more aligned true angle. Also, I have already mentioned that the pin mesh system serves two purposes in another thread.

    The first purpose is the adjustment for the correct fitment of pinion to spur ratios and the second purpose being that the pin system acts as a fail-safe to keep the motor aligned in the event the motor mount screws work loose or slide under 8S power.

    With 8S power being the issue that causes most of these problems, I cannot for the life of me understand how someone could be confident that motor will not walk in the cradle on a stock setup if they choose to not use the pins.

    I'm just saying that if I chose to manually mesh the stock motor without the pins, even if I checked the tightness of those motor mount screws before every run, I still have this inclination to believe that the motor would still walk a little out of alignment and cause problems that are not easily seen or noticeable upon visual inspection.

    Maybe not right away or noticeable; but over time, I guarantee you would start to see the rounded off edges on the long axis of the teeth on either the pinion or spur if not both.
    Last edited by Flux Capacitor; 10-13-2020 at 12:37 AM. Reason: Spelling.
    Sent from my autonomous device.

Posting Permissions

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