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  1. #1
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    Help don't understand the ghearing

    So the stock gearing is 18 pinion and a 54 spur. But when I look at WFO gears and I see gears like 35 pinion and a 35 spur. That is a big difference between WFO and Xmaxx stock 18 pinion and 54 spur.

    I'm waiting on everything to show up. And am using a XLX2 combo with a 1100kv motor. And want speed. And little jumping so what gearing should I get numbers?

    Thank you

  2. #2
    RC Turnbuckle Jr. ReglarGuy's Avatar
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    Even though I don't know what WFO means I'll try to answer your question. Guys that are using 35/35 gears are using high torque, low KV motors; like 800kv motors for example. I think the stock motor for a 8s Xmaxx is 1200kv, so lets use that to answer your question. With a stock 1200kv motor and stock 54/18 gears, your final spur gear RPM's for your stock setup is 400 RPM's.

    To find that 400 final stock spur gear RPM number, all you have to do is take your 54 spur, divide it by 18 pinion (to get a ratio of 3), and divide that 3 into 1200kv.

    With your new 1100kv motor (using the same 54/18 gears), you're going to drop 34 final spur gear RPM's. To get that 34 final spur gear RPM's back up to 400, we want to take your new 1100kv motor, divide it by 400 final spur RPM's to get a 2.75 ratio. Then take that 2.75 ratio, and divide it into our stock 54 spur gear to get your new pinion gear value that you need to get your stock final spur gear's RPM's back up to 400 (which is 20).

    So, the pinion gear you need, to get the 34 spur gear RPM's (that you lost by going from a 1200kv motor to a 1100kv motor) back up to a stock total of 400 final spur RPM's is a 20T pinion gear.
    Last edited by ReglarGuy; 04-02-2021 at 06:21 AM.
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  3. #3
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    Sorry for not mentioning that WFO RC Racing makes some of the most heavy duty pinions and spur gears -



    I understand some of what your saying. But how do you know what rpm of the spur should be? Saying I want really fast speeds? Then what pinion and spur. And what rpm? What can it take for going real fast before it gives and breaks.

  4. #4
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    Quote Originally Posted by chucky732 View Post
    Sorry for not mentioning that WFO RC Racing makes some of the most heavy duty pinions and spur gears -



    I understand some of what your saying. But how do you know what rpm of the spur should be? Saying I want really fast speeds? Then what pinion and spur. And what rpm? What can it take for going real fast before it gives and breaks.
    Mate, you need to know this WFO gears are 1.5 MOD, the stock ones are 1.0 MOD.

  5. #5
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    Please tell me what the difference is? And the 1.5 MOD is the only ones they list on there website.


    Quote Originally Posted by Juanmacine View Post
    Mate, you need to know this WFO gears are 1.5 MOD, the stock ones are 1.0 MOD.
    Last edited by chucky732; 04-02-2021 at 09:25 AM.

  6. #6
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    Quote Originally Posted by chucky732 View Post
    Please tell me what the difference is? And the 1.5 MOD is the only ones they list on there website.
    In the 1.5 MOD, the pitch on the tooth is greater than the 1.0 MOD, the 1.5 gears are stiff and heavier than the original ones, better performance.

  7. #7
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    I still need help understanding the gear ratio thing.

  8. #8
    RC Champion Acidic01's Avatar
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    https://youtu.be/IevcWhk_7es

    https://rogershobbycenter.com/rc-gearing-101

    Above should help you understand more on gearing.



    Sent from my Pixel 3 XL using Tapatalk

  9. #9
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    Quote Originally Posted by Acidic01 View Post
    https://youtu.be/IevcWhk_7es

    https://rogershobbycenter.com/rc-gearing-101

    Above should help you understand more on gearing.



    Sent from my Pixel 3 XL using Tapatalk
    Excellent links mate.

  10. #10
    RC Turnbuckle Jr. ReglarGuy's Avatar
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    Quote Originally Posted by chucky732 View Post
    I understand some of what your saying. But how do you know what rpm of the spur should be? Saying I want really fast speeds? Then what pinion and spur. And what rpm? What can it take for going real fast before it gives and breaks.
    In my reply, I showed you the math, so you could figure out on our on how to have the same performance when you went from a 1200kv motor to a 1100kv motor. I even made it as simple as possible by only using a 1volt supply voltage in my example. To find out what your true final motor RPM's are at 6s or 8s you would take your 400 final spur RPM's (which is also your motor's final RPM), and multiply that my 25volts (6s) or 34volts (8s). If you do that your answers would be 10,000 RPM's for 6s, and 13,000 RPM's for 8s.

    As a "general rule of thumb" you want to use gearing that keeps your motor's final RPM's between 12 to 18,000 to have the best chance of longevity. Using what you semi-learned in my other reply (lol), you want to increase your 1s RPM from 400 RPM's to 514 RPM's to get you the 8s top end you're looking for (18,000 RPM's). To do that (using what you semi-learned), you want a 2.2 ratio rather than a 2.7 ratio. The gearing you would need with a 1100kv motor, to keep you in the 18,000 RPM range using 8s (34volts), would be a 46T spur gear an 21T pinion gear.

    Of course, anytime you change gearing its very important to monitor your temperatures with each gearing change, because calculations just gets you in a reasonable starting area. You'll want to fine tune your final gear selection that will keep your ESC and motor temps at 140 and under. Keep in mind that another tuning trick is: if your motor is running hot, reduce your gearing; and if your ESC is running hot, increase your gearing.
    Last edited by ReglarGuy; 04-03-2021 at 06:20 AM.
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  11. #11
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    Thank you. But I'm more confuse then before. You said 21/46 for the 1100kv motor. B&M racing says to use 25/35 on a 1100kv motor. WFO racing says to use 18/35 for a 1100kv motor. By dividing like you said.Below is the ratios

    You - 2.19 ratio

    B&M - 1.4 ratio

    WFO - 1.94 ratio

    This is why I'm confused. A big stretch here.



    Quote Originally Posted by ReglarGuy View Post
    In my reply, I showed you the math, so you could figure out on our on how to have the same performance when you went from a 1200kv motor to a 1100kv motor. I even made it as simple as possible by only using a 1volt supply voltage in my example. To find out what your true final motor RPM's are at 6s or 8s you would take your 400 final spur RPM's (which is also your motor's final RPM), and multiply that my 25volts (6s) or 34volts (8s). If you do that your answers would be 10,000 RPM's for 6s, and 13,000 RPM's for 8s.

    As a "general rule of thumb" you want to use gearing that keeps your motor's final RPM's between 12 to 18,000 to have the best chance of longevity. Using what you semi-learned in my other reply (lol), you want to increase your 1s RPM from 400 RPM's to 514 RPM's to get you the 8s top end you're looking for (18,000 RPM's). To do that (using what you semi-learned), you want a 2.2 ratio rather than a 2.7 ratio. The gearing you would need with a 1100kv motor, to keep you in the 18,000 RPM range using 8s (34volts), would be a 46T spur gear an 21T pinion gear.

    Of course, anytime you change gearing its very important to monitor your temperatures with each gearing change, because calculations just gets you in a reasonable starting area. You'll want to fine tune your final gear selection that will keep your ESC and motor temps at 140 and under. Keep in mind that another tuning trick is: if your motor is running hot, reduce your gearing; and if your ESC is running hot, increase your gearing.
    Last edited by chucky732; 04-03-2021 at 07:57 PM.

  12. #12
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    Quote Originally Posted by chucky732 View Post
    Thank you. But I'm more confuse then before. You said 21/46 for the 1100kv motor. B&M racing says to use 25/35 on a 1100kv motor. WFO racing says to use 18/35 for a 1100kv motor. By dividing like you said.Below is the ratios

    You - 2.19 ratio

    B&M - 1.4 ratio

    WFO - 1.94 ratio

    This is why I'm confused. A big stretch here.
    Mate, you can choose the ratio you want for your requeriments, the most tooth in the pinion and less tooth in the spur, the stress for the motor and ESC are bigger, I think 18/35 WFO ratio is the medium choice, maybe the better at this time.

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    What do you mean by medium? I like to go faster. So if I increase the pinion tooth count I go slower. But if I lower pinion tooth count the faster I can go?

    Another question. I watched a bunch of videos. And from some in those videos they claim the bigger the can the more torque you'll have. Is that true?

    Thank you.


    Quote Originally Posted by Juanmacine View Post
    Mate, you can choose the ratio you want for your requeriments, the most tooth in the pinion and less tooth in the spur, the stress for the motor and ESC are bigger, I think 18/35 WFO ratio is the medium choice, maybe the better at this time.

  14. #14
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    Think of your 21-speed bicycle. The front gear set attached to the pedals is like the pinion. The rear gear set on the wheel is the "spur." What gears work best when starting from a stand-still? What combo works better for higher speed? If you go small up front and large in the back then you will be able to put down a lot of torque but have low speed for the amount of effort you put in to the pedals. Large up front and small in the rear and you will have to expend a lot of effort just to get moving.

    Put the same bike under a 10-year-old and a college athlete. One "motor" considerably stronger than the other...now perform the same tests.
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  15. #15
    RC Turnbuckle Jr. ReglarGuy's Avatar
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    I really like your analogy, Double. Just about every guy has had a variable speed bike, and can relate...never had a 21 speed, though, just a 10 speed. I guess I'm showing my age. (lol)

    Thank you. But I'm more confuse then before. You said Thank you. But I'm more confuse then before. You said 21/46 for the 1100kv motor. B&M racing says to use 25/35 on a 1100kv motor. WFO racing says to use 18/35 for a 1100kv motor.
    As far as for you, Chucky, I gave you the tools you needed to figure out your own gearing. If you re-read what I gave you, I said that "21/46 for a 1100kv motor" was a calculated value, and that calculated value would get you in the range of what you wanted (top speed). From there, I gave you how to use your "motor and ESC temps" to fine tune your calculated gear selection to the final gears you will want to use.

    There's an old saying, Chaz, "Give a man a fish and he'll eat for a day. Teach a man how to fish, and he'll eat for the rest of his life." I don't think you could go wrong taking B&M/WFO's advice (25/35 or 18/35 for a 1100kv motor), but they are giving you a fish, and I was teaching you how to fish. So now, you have a decision to make, do you want to eat for a day; or for the rest of your life.
    Last edited by ReglarGuy; 04-05-2021 at 04:10 AM.
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  16. #16
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    First off you talk about the spur gear RPM number. Why? How are you measuring the RPM number. You say the spur gear is turning 400 rpm. So is the final gear rpm that drives the front and back diff running at 400 rpm's? So what is the rpm of the tires? You can try to teach but if the student doesn't understand what you are saying then your not teaching.

    If the 1100kv is faster then the 800kv motor then why do you need to bring the 1100kv up to 400 rpm? You shouldn't have to if the 1100kv has a faster rpm.

    I'm an old guy like but maybe older. What was a 10 speed. I use to racing pan cars and they only had a pinion and a spur gear that was connected to one the rear rims/tires.



    Quote Originally Posted by ReglarGuy View Post
    I really like your analogy, Double. Just about every guy has had a variable speed bike, and can relate...never had a 21 speed, though, just a 10 speed. I guess I'm showing my age. (lol)


    As far as for you, Chucky, I gave you the tools you needed to figure out your own gearing. If you re-read what I gave you, I said that "21/46 for a 1100kv motor" was a calculated value, and that calculated value would get you in the range of what you wanted (top speed). From there, I gave you how to use your "motor and ESC temps" to fine tune your calculated gear selection to the final gears you will want to use.

    There's an old saying, Chaz, "Give a man a fish and he'll eat for a day. Teach a man how to fish, and he'll eat for the rest of his life." I don't think you could go wrong taking B&M/WFO's advice (25/35 or 18/35 for a 1100kv motor), but they are giving you a fish, and I was teaching you how to fish. So now, you have a decision to make, do you want to eat for a day; or for the rest of your life.
    Last edited by chucky732; 04-05-2021 at 06:38 AM.

  17. #17
    RC Turnbuckle Jr. ReglarGuy's Avatar
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    First off you talk about the spur gear RPM number. Why?
    Because, your spur gear is connected to your motor, and as your motor turns (or rotates) so when it dose, so does your spur gear. Double-G-Wiz gave you a perfect analogy of that with his bicycle example.

    How are you measuring the RPM number.
    Your spur gear is driven by your 1100kv motor. Your motor turns at 1100 RPM's per volt (or turns 1,100 times per minute per volt). The rest of of the numbers you need is done by using math to develop gear-to gear ratios. You can develop your gear ratio's two ways. One, by using 1 volt applied, or two, by using what voltage you want to apply.

    I didn't know what voltage you wanted to apply, so I gave you the voltage ratio developed from 1 volt applied to a 1200kv and 1100kv motor, and showed you the difference between the two (Post #2). Then in (Post #10) I show you how to take your gear ratio (that was developed by 1volt, and use it for what ever input voltage you wanted to use (I used 6s and 8s examples).

    So, is the final gear rpm that drives the front and back diff running at 400 rpm's?
    No, all we have discussed so far is just the gear ratio of the pinion gear (on your motor) and the spur gear (connected to your truck's drive train). Don't get your spur gear's final RPM's confused with your truck's final speed (or your tires RPM's). Going from a spur gears final RPM to your tires final RPM's are two different things.

    You can try to teach but if the student doesn't understand what you are saying then your not teaching.
    No, he's teaching, but the student just doesn't understand. So, if the student doesn't understand, then (if both are willing) they both have to keep at it until the student does. I'm game if you're game. I'm here for you babe (lol)

    If the 1100kv is faster then the 800kv motor then why do you need to bring the 1100kv up to 400 rpm? You shouldn't have to if the 1100kv has a faster rpm.
    I got to get ready for work, so I'll see how I can answer this later, okay. Take care till then.
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  18. #18
    RC Turnbuckle Jr. ReglarGuy's Avatar
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    Your last question.

    If the 1100kv is faster then the 800kv motor then why do you need to bring the 1100kv up to 400 rpm? You shouldn't have to if the 1100kv has a faster rpm.
    In your original post below,

    So the stock gearing is 18 pinion and a 54 spur. But when I look at WFO gears and I see gears like 35 pinion and a 35 spur. That is a big difference between WFO and Xmaxx stock 18 pinion and 54 spur.

    I'm waiting on everything to show up. And am using a XLX2 combo with a 1100kv motor. And want speed. And little jumping so what gearing should I get numbers?
    you asked why you were seeing 35/35 gearing with WFO. I told you guys were using that kind of gearing wit 800kv motors. You also said, that your Xmaxx was stock. The stock 8s Xmaxx comes with a 1200kv motor. You said you wanted to replace your stock 1200kv motor with a 1100kv motor (along with a Castle XLX-2), and asked what gearing you needed. I (in Post #2) gave you the gearing you would need to have the same performance using a 1100kv motor (54/20 gearing) as you had with you using your original stock 1200kv motor (54/18 gearing).

    Note: I did make one type error, though in Post #2.

    So, the pinion gear you need, to get the 34 spur gear RPM's (that you lost by going from a 1200kv motor to a 1100kv motor) back up to a stock total of 400 final spur RPM's is a 20T pinion gear.
    The 34 should be 54. I'm sorry about that Chaz.

    Then in Post #3 you said you wanted really fast speeds, so (in Post #10) I gave you (again by using and showing you the math) 46/21 gearing. I gave this to you as a safe starting point. From there (in Post #10), I told you how you could use your motor/ESC temps to fine tune your gearing up to the top speed you wanted safely.

    Of course, anytime you change gearing its very important to monitor your temperatures with each gearing change, because calculations just gets you in a reasonable starting area. You'll want to fine tune your final gear selection that will keep your ESC and motor temps at 140 and under. Keep in mind that another tuning trick is: if your motor is running hot, reduce your gearing; and if your ESC is running hot, increase your gearing.
    From there, you posted in Post #11

    Thank you. But I'm more confuse then before. You said 21/46 for the 1100kv motor. B&M racing says to use 25/35 on a 1100kv motor. WFO racing says to use 18/35 for a 1100kv motor. By dividing like you said. Below is the ratios

    You - 2.19 ratio

    B&M - 1.4 ratio

    WFO - 1.94 ratio
    Chas, the difference between what you and I have discussed, and what you have seen at B&M and WFO is that they are just telling you what you need. You and I are discussing how you can find out what you need on your own. If you use what we are discussing, you might need the same gears as B&M and WFO suggest. The nice thing about knowing "how" as apposed to just using a gearing chart is, that you can always get the "exact" right gears for your specific truck (no matter what level mods you have installed on your truck). Thus....

    As far as for you, Chucky, I gave you the tools you needed to figure out your own gearing. If you re-read what I gave you, I said that "21/46 for a 1100kv motor" was a calculated value, and that calculated value would get you in the range of what you wanted (top speed). From there, I gave you how to use your "motor and ESC temps" to fine tune your calculated gear selection to the final gears you will want to use.
    and thus....

    Of course, anytime you change gearing its very important to monitor your temperatures with each gearing change, because calculations just gets you in a reasonable starting area. You'll want to fine tune your final gear selection that will keep your ESC and motor temps at 140 and under. Keep in mind that another tuning trick is: if your motor is running hot, reduce your gearing; and if your ESC is running hot, increase your gearing.
    In the end Chas, if you were to go though the tuning process (that we have been discussing) you may end up with the same gearing as what B&M and WFO are giving you, but again you might not. It all depends on how close your truck's mechanics are to what truck B&M and WFO used to get their gearing suggestions.

    P.S. Also, I don't mind drawing up some illustrations, if you think that will help you.
    Last edited by ReglarGuy; 04-07-2021 at 05:21 AM.
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