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  1. #1
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    RPM sensor and gearing

    Team - my new xmaxx 8s arrived today. Very surprised and happy it has a few telemetry options all ready installed. It has the vintage for the receiver 6v and the motor temp. At turn on it was 69.
    So I've orders the gps for the speed and ideas on how to get the rpm.

    Plus - gearing. Standard is 18/54. Been told only install the 46t spur for speed only and will burn out the truck if bashing.
    I want to hit the 50+ without cooking the truck every time I play.

    Any ideas on pinion and spur size for this.

    Cheers.

  2. #2
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    I put all the telemetry I could find on my xmaxx. Traxxas doesn't have an rpm sensor for this truck yet. Best I could find was people modifying the sensors from other trucks, bit that requires drilling a hole in your spur gear to install a magnet.

    Two other things you can add are another temp sensor for your esc. And the battery tap and voltage sensor. It's nice knowing how much voltage you've got left.

    Without a different motor and esc, you will be pushing the limits to reach 50+. You can play around but watch that motor temp sensor and give it a break everytime it gets to 160F, because it will. At 18/46, I can run for 10-15 and then let the truck sit with the fans blowing on the heat sink for 10 minutes.

    Can't wait for the last of my parts so I can post finished pictures of my truck. I see a lot of questions about telemetry on here, but it's simple when you see all the parts.

    Sent from my HTC One M9 using Tapatalk

  3. #3
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    I'm sorry, I also wanted to let you know this truck doesn't need to go 50mph. My top speed is 42, and I rarely get it over 30 unless I'm on a huge track, or pavement. Like a motocross track...not even bmx is big enough. And I've done quite of a few mods to make it controllable even at 40. The truck is really sloppy when it's stock. Which is a good thing, to be honest. Less broken parts if they have space to bend instead. But if everything bends...nothing is straight and high speed isn't much fun. To run like that and feel in control you need to get rid of the slop in the axle carriers and steering. The proline tires are sort of a wash...you will have more control with them, but the stock v2s are lighter and balloon more, which makes the tires taller and lowers your gear ratio further, making you got faster....just don't turn. Lol

    Sent from my HTC One M9 using Tapatalk

  4. #4
    RC Turnbuckle Jr. ReglarGuy's Avatar
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    Best I could find was people modifying the sensors from other trucks, bit that requires drilling a hole in your spur gear to install a magnet.
    You don't have to drill a hole for your RPM sensor.









    Getting RPM's is an easy mod. The BLUE plug is for the RPM's, and the RED plug is for the motor TEMP.
    Last edited by ReglarGuy; 04-27-2017 at 01:25 PM.
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  5. #5
    RC Racer
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    is that metal gearing

  6. #6
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    Quote Originally Posted by ReglarGuy View Post
    You don't have to drill a hole for your RPM sensor.

    Getting RPM's is an easy mod. The BLUE plug is for the RPM's, and the RED plug is for the motor TEMP.
    I must have read it wrong. My bad. Which truck is that sensor for? I'll probably do it when I need a project if they don't make one for the xmaxx.



    Sent from my HTC One M9 using Tapatalk

  7. #7
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    It's for the new 8s xmaxx. Can't find a way to get a rpm sensor. Metal gears and no options to buy one.

  8. #8
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    Quote Originally Posted by RVJ007 View Post
    is that metal gearing
    That's a Plastic gear forsure!
    V1 BL5/2028, V2 max6/5882, Erevo, Summit, Rustler.

  9. #9
    RC Turnbuckle Jr. ReglarGuy's Avatar
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    It's the original plastic 54t gear, but the new metal one has a spot for you to put the magnet. The metal 54t gear came out after I did this mod to my truck. The sensor is what Traxxas uses for installing RPM telemetry on their XO-1.
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  10. #10
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    So it can be done with a metal
    Heat on the 8s. Have you done this and any pics on how you attached it to the spur

  11. #11
    RC Turnbuckle Jr. ReglarGuy's Avatar
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    With the new Xmaxx's crush drive housing (which comes in two parts) look at the non-round half, and you can see where a RPM sensor magnet is suppose to go. If need be, you can reference the XO-1 crush drive to get an idea of what you're looking for.
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  12. #12
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    Hi!

    On this post:


    are not still present the photo :-( now I want to modify my x maxx for rpm sensor but without this pohoto it could be difficult :-(

    can some one send me that photo?

    or maybe I can reopen a new thread and we can talk here!

    thanks all
    Massimiliano

  13. #13
    RC Turnbuckle Jr. ReglarGuy's Avatar
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    You're in luck, because even if Photobucket tries to screw us, they can't.







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  14. #14
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    Quote Originally Posted by ReglarGuy View Post
    You're in luck, because even if Photobucket tries to screw us, they can't.







    Hi! Thanks you regularGuy! Are very very very usefull this image for me!

    What you have buy is the origianl RPM sensor TRX6522 and a magnet. Only one info, I eared that for mount the magnet on x maxx 6s I need to put another plastic circle in the spur gear, a kind of "magnet holder"... you have directly glued the magnet on the original spur gear without any other thing, correct?
    the spare part trx6540 is a magnet original traxxas, is that you used (or you think it is compatible) ?

    thanks you very mutch
    Massimiliano

  15. #15
    RC Turnbuckle Jr. ReglarGuy's Avatar
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    I carved out the area (in the gear) I wanted to mount the magnet. Then I used PolyWater adhesive to glue in the magnet, and fill in the area around the magnet. You don't have to use PolyWater, but it's guaranteed to bond permanently anything to whatever.

    To carve out the needed area in the gear, I used a small sharpened straight slot screwdriver, and a Exact-o knife with the very tip broken off.

    Below is a picture I took with the RPM sensor, temp sensor module-ised, That way it make it easier to break down the truck when doing maintenance. The BLUE plug is RPM, and the RED is temp.

    Last edited by ReglarGuy; 05-23-2019 at 01:51 PM.
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  16. #16
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    fantastic!
    Thanks you for your explanation!
    I will try very soon!

    thanks
    Massimiliano

  17. #17
    RC Turnbuckle Jr. ReglarGuy's Avatar
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    Quote Originally Posted by holyhope View Post
    fantastic!
    Thanks you for your explanation!
    I will try very soon!

    thanks
    Massimiliano
    You're most welcome, and I used (even though it doesn't matter) Emaxx magnet and sensor.
    The ReglarGuy is kid tested and father approved.

  18. #18
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    Ahah ok ok!
    I order a magnet Traxxas original... Paied 3.5euro. It is very very very expensive for a pieces of magnet but 3.5euro are a very small price if you do not need to cut a magnet etc..
    I buy a rpm sensor long version.. So as soon as possible I will try this Implementation!. I have break my dog bone and wheels... I have some replacement in this order... I hope I will return operative as soon as possible! Ahah

  19. #19
    RC Turnbuckle Jr. ReglarGuy's Avatar
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    Something else you may need to be aware of. There's a chance that the Final Gear Ratio formula on page 28 in your 8s owner's manual is wrong. It's wrong in my 6s owners manual. If you use your stock 8s gearing of 18/54, use the default Final Gear Ratio setting in your Traxxas Link; you should be okay.

    The key to knowing (if your 8s formula is right) is by seeing if your Traxxas Link is using 8.11 as its' Final Gear Ratio setting. If so, then your page 28 formula is wrong. You can't use 8.11 as your formula's multiplier, and have 8.11 as your Final Gear Ratio product unless the results of 54 divided by 18 is 1. However, the last time I checked it was 3.

    Here's my 6s owner's manual. It shows the multiplier in my Final Gear Ratio formula as 8.24. In my Traxxas Link my Final Gear Ratio default (for stock 6s gearing of 15/54) is 8.24. My Traxxas Link works fine if I have stock a 15/54 gear set, but I run beefier electronics and had to go from a 15/54 to a 29/54 gearing.



    When I used the Traxxas 8.24 number as my "multiplier" (in the Final Gear Ratio formula) I got 29.66 as my result. Using 29.66 in my Traxxas Link made my RPM's go crazy, so here's what I had to do.



    I new that the Traxxas Link default 8.24 was a good number. I new the 15 and the 54 were good numbers. This meant that the "multiplier" had to be incorrect, so I made it my unknown factor. Solving for "X" resulted in 2.89 as my corrected multiplier. When I used the corrected formula with my new 29/54 gearing, I got the right RPM's on my Traxxas Link display.

    If you need to, you can plug in 18 for my 15, 8.11 for my 8.24, and use my transposed formula to calculate your new correct Final Gear Ratio's multiplier. The key to (knowing if you need to) will be if you want to change your gearing, and if you have 8.11 being used in your Traxxas Link. Remember, you can't have 8.11 as your formula's multiplier, and also have it as your Traxxas Link, Final Gear Ratio default.
    Last edited by ReglarGuy; 05-27-2019 at 05:39 AM.
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  20. #20
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    Hi thanks you for tour info.
    I0m sorry for delay... Today I will try to install the magnet... it was arrived friday but untill today i can't unbox the packet!

    This evening I will try to install it (I'm writing from Italy, so... there are few hours of time zone!)

    this evening I will read another time (but with more time to spend for it) your explanation; on the first read there is something I not understand very well...

    thanks
    Massimiliano

  21. #21
    RC Turnbuckle Jr. ReglarGuy's Avatar
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    As you have questions just post them and I'll try to help you out.
    The ReglarGuy is kid tested and father approved.

  22. #22
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    Thumbs up

    Hi!

    yesterday I did the work!

    After several problems it works!

    i put the sensor outside the cover and I trill a hole because in your position ... i see in my x maxx... it is the center of gear and the magnet I placed (like you) in the external part of the gear... so i was worried that maybe could not read the magnet...

    I must to trill a part of chassis because the wire of sensor block the cover to close in a right position (and sensor not see the magnet in this position)

    here there are a photo of m work.

    it is very funny the position was erected my x maxx with a light inside it!

    IMPORTANT THING: For glue the magnet and the sensor I use the Henkel Loctite Super Attak (this one: https://www.amazon.it/Loctite-204807.../dp/B0084OI4PC )
    it is enought for you? Due rusting of my screw bottom the x maxx was not possible to disassemble all the motor so I glue it without disassemble... (Very Hard). I place a very big quantity of super attack (and in the position that I placed x maxx the excessive glue not go around the model)

    I verify that the sensor work but not the quality of the speed read... I see about 80 km/h of max speed WHEN I TEST WITH WHEEL NOT ON THE GROUND (I leave the x maxx with chasis above a little chair , so wheel are free to spin) and trasmission ratio is not 8.11 ... I have pinion and spur gear of 18/50



    tomorrow for future test (today I'm not at home...)

    thanks
    Massimiliano
    Last edited by holyhope; 06-05-2019 at 01:53 AM.

  23. #23
    RC Turnbuckle Jr. ReglarGuy's Avatar
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    When your running your truck to check your RPS take your wheels off. Testing will be easier that way. I don't know about the glue you used, so time will tell if it holds well enough. I can't tell from your pictures how you installed everything, but if it works, it works. Use my corrected formula (above) to calculate your "Gear Ratio." It should work for you too.
    The ReglarGuy is kid tested and father approved.

  24. #24
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    Hi reglarguy!
    As all past times your answer are very perfect!

    Ok, time will tell us if this glue will work!!!

    Tomorrow I will correct my gear ratio with your info!
    thanks!
    Massimiliano

    Hi, I'm reading your thread about gear ratio.

    So I have configuration of 50 / 18 (was changed by previous owner)

    My version is X Maxx 6s

    I change (only rear... I'm still waiting the other 2....) the rear wheel but size is very similar between them (I have stck front and Louise rear)

    On my traxxas link app the gear ratio is 8.24 (not 8.11)

    I not have original instruction box and I downloaded some month ago the instruction from site (for the 6s version) and in that (revision 04, the name file is: "77076-4-OM-EN-R04.pdf" ) is 8.24 and the ratio for my gear (18/50) is 2.78

    So, tell me if I am correct

    Final Gear Ratio: ( 50/18 ) * 8.24 = 2.78 * 8.24 = 22.89
    And I verified that the table was true about 50/18 that is 2.78
    Ok I confirm that in My traxxas link app I have 8.24 selected... Is set this value by default!

    Now second part, Traxxas link final gear ratio

    (50/18) * X = 8.24 (Traxxas link final gear ratio)

    So X= 8.24*18/50 = 2.9664

    SO now I not understand what I must do!
    What value I must set in my traxxas link app?!

    And the value that I discovered, 2.9664, is the CORRECT value instead the 2.78 ?!?

    So I must "fake value" in my traxxas link app about pinion and spur for crrect?! Or I must change the gear ratio in traxxas link app?!? I remember that in my traxxas link app I have by default 8.24

    Sorry but maybe I missunderstand something..

    thanks
    Massimiliano
    Last edited by Double G; 06-05-2019 at 07:39 AM. Reason: merge

  25. #25
    RC Turnbuckle Jr. ReglarGuy's Avatar
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    1). Do you have the 6s version Xmaxx with the slipper clutch, or do you have a 8s version Xmaxx with the center diff?
    2). What pinion gear and what spur gear do you want to use?
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  26. #26
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    Hi
    I have the 6s version! I do not know what kind of clutch is the slipper.... But I Can tell you that I have the 6s version.

    I want to use pinion 18 and spur 50!

    Thanks!
    Massimiliano

  27. #27
    RC Turnbuckle Jr. ReglarGuy's Avatar
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    Let's make this easy for you using my corrected formula (being you have a 6s): Spur/Pinion X Multiplier = Final Gear Ratio

    50 (Spur) divided by 18 (Pinion) equals 2.77.
    2.777 times 2.89 (corrected Multiplier) equals 8.027 (Final Gear Ratio)

    I don't know what Traxxas Link App you have, because I don't update mine. I don't have the Xmaxx 8s, UDR, or any of the newer Traxxas products in my version, so I can't tell you what the 8s defaults are. My App shows the Traxxas 6s Xmaxx, and its' default settings at 15/54 and 8.24. This will work if you have stock 6s gearing. However, you're wanting to go with 15/50 gearing. So, if I was going to use your gearing of 18/50, I would have to change my default settings to 15/50 and 8.02.

    You should be pretty close with those settings. Now, if you had a 8s, we would have to develop another (Multiplier) for our formula. That's what I was saying above, but you're saying you're a 6s like me, so you should be good with my original corrected formula that calculated 8.02 from using a 15/50 gear set.

    Enter 15 for your pinion, 50 for your spur, and 8.02 in both your Final Gear Ratio entries in your Traxxas Link App.
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  28. #28
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    Hi reglar! Thanks you very mutch for your calculation.
    I confirm you that mine x maxx is 6s and I have updated the firmware (both transmitter and esc / receiver) and the app about 1 week ago.

    Ok I will put your new setting and I will test it as soon as possible! Yesterday I reach 80km/h with 18/50 but original 8.24 stock setting using the x maxx with free wheel and about 46 km/h in real movements. I will try with your new setting

    thanks
    Massimiliano

  29. #29
    RC Turnbuckle Jr. ReglarGuy's Avatar
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    Good luck, and if you put your findings in miles per hour rather than metric, I'll understand your progress and results better. Here in the U.S. we do things the old fashion way. (lol)
    The ReglarGuy is kid tested and father approved.

  30. #30
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    Hi!

    So sensor is working well! Wheel not good ahah! I will buy another pair of louise!

    An info, a little off topic, for trx 4 there are any magnet holder traxxas original or I must glue the magnet another time? I have a trx 4 and I want to do the same thing that I made in my X-maxx ....

    thanks!
    Massimiliano

  31. #31
    RC Turnbuckle Jr. ReglarGuy's Avatar
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    I think you're going to have to use the GPS and Expansion module for that truck. I don't think you have the real estate for the magnet sensor setup. That truck is tightly put together.
    Last edited by ReglarGuy; 06-13-2019 at 03:22 PM.
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  32. #32
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    Hi! Ok thanks you!

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