HorizonHobby.com How-To: Understanding RC Gearing
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- Опубліковано 6 вер 2024
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One of the most common questions we hear about RC cars and trucks is, "how fast does it go?" While this seems like a common, ordinary and easy question to answer, the truth is that there are a number of different factors that contribute to a vehicle's speed, torque and acceleration. One of the big determining factors is the gear ratio and transmission of your vehicle. While things like installing a faster motor or higher voltage battery are easy things to understand, wrapping your head around gear ratios can be like taking an advanced course in physics, geometry, algebra and trigonometry. While there's a lot going on, there's some simple ways to get a basic understanding of what the gears in your transmission do, what changing them means and how things work. We've also put a list of commonly used terms together for you below for quick reference to help you as you progress.
External Gear Ratio -- The gear ratio of the gears that are visible or outside of a transmission case. This is the ratio of the pinion and spur gear.
Final Drive Ratio -- The gear ratio of the entire drive system in a car or truck. This includes the internal gear ratio of the transmission and the external gear ratio of the pinion and spur gears. You can calculate this ratio by dividing the spur gear tooth count by the pinion gear tooth count and multiplying that total by the internal transmission ratio.
Gear Ratio -- A gear ratio is the relationship between the number of teeth on two meshed gears. This relationship is expressed mathematically. For example, if one gear with 50 teeth is driven by a gear with 20 teeth, the gear ratio is 2.5:1. You would calculate this by diving 50/20 for a total of 2.5.In an RC Car, you have 2 different ratios you'll need to work with to achieve the proper gearing for a specific application and goal. The first is the external ratio and the other is the internal ratio.
Internal Gear Ratio -- The gear ratio of a vehicle's transmission gears separate from the pinion and spur gear ratios. The internal ratio is a fixed number determined by the manufacturer of your vehicle.
Module -- For countries that use the metric system, Module is the equivalent of pitch. It typically refers to the pitch diameter, in millimeters, divided by the number of teeth. The higher the number on the pitch, the finer the tooth profile is. The common module types are 1.0 module and 0.6 module.
Pinion Gear -- A small gear that directly attaches to the output shaft of an electric motor.
Pitch (AKA Pitch Diameter) -- In countries that do not use the metric system, pitch refers to the number of teeth on a gear with a 1-inch pitch diameter. The higher the number on the pitch, the finer the tooth profile is. The finer the pitch, the more efficient the gear; however, since they have less material, they are often more prone to stripping if the mesh is not set properly. The more coarse the pitch, the less efficient the gear will be; however, they are also more durable and less susceptible to damage. 48 pitch is the most common pitch in RC, however, 64 pitch and 32 pitch can also be used.
Spur Gear -- The large gear mounted to the top shaft of your transmission in an off-road vehicle, the center differential in an 1/8-scale or 4WD Short Course Truck or the main lay shaft in an on-road vehicle. The spur gear is driven by the pinion gear or clutch bell.
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Ahh the nostalgia. Classic video. ❤
To determine the pitch of any spur gear use the following formula:
P = (T+2)/D
P = Pitch, T = number of teeth in gear and D = the measured outside diameter of the gear.
The resulting calculation will give you a whole number with a decimal. Disregard the decimal value on the end. The whole number is the pitch of the gear.
Example:
I have a pinion gear with 18 teeth. The measured diameter with a pair of calipers yields 0.415 inch. Using the above formula, P = (T+2)/D = (18+2)/.415 = 48.193, the pitch of the gear is 48
I hope that helps.
Joe
Referring to the math classes I thought I would never use, my very first thought when you said that was going to be using it here today was "I bet you're not". Because for me, that was Algebra lol. I worked for 25 years as a CNC programmer and machinist, and I never used Algebra one time after high school.
But this was a great video that really breaks things down. Good job, and thanks for sharing!
I appreciate this type of refresher knowledge. Helps when you can “build and UN-build it in your head and logically”
@fieryguns Absolutely! Many people have learned on the Super Cub! And it's gotten even better in recent years with a battery upgrade to LiPo and a transmitter/receiver upgrade to Spektrum DSM2 radio gear. You may also want to check out the new HobbyZone Stratos as well.
It was like a math lesson, but very informative thanks :)
I know this is an old video but this helped so much! Thank you horizon hobby
Clashy Bashy, it’s an very old vid now, three years on from your comment
It all depends on where you're running, the size of the straight away, the battery configuration and more. It's really unique to each track.
As a general rule of thumb when you increase the RPMs of the motor you decrease the size of the pinion. So if you have a 13T motor you would gear it with a smaller pinion than say a 17T motor.
Generally speaking 48P gives you the best combination of durability and efficiency. What sort of car are you running?
That is the overall desire, to have the best balance between top speed, acceleration and runtime.
They are all relations. For the larger gear to turn once, for example, how many times will the smaller gear have to turn. So for your first example, 7.35... The pinion gear will turn 7 full rotations and .35 of an 8th rotation. In this same time the spur gear will turn a total of one time. Hence 7.35(rotations):1(rotation)
The FDR (Final Drive Ratio) of the Rustler transmission is 2.72:1. So for that transmission you would divide your spur gear tooth count by the pinion gear tooth count and multiply that by 2.72 to get your overall gear ratio. So for wha you have now, 32 / 32 x 2.72= 2.72 for your gear ratio.
The lower the ratio will yield the faster top-speed but lower acceleration. The 32T pinion will give you more top speed. Cogging is caused by a number of reasons but the biggest is the motor/ESC themselves. The more you load a sensorless motor, however, can magnify that problem.
7:20 is what I came here for
thanks
Same
Cheers, should be at start of video as introduction into gearing then all the more complicated stuff later in the video.
Yeah same here. I just need to get a new gearing to make it faster, and now I know how. I was ready to look for this timestamp myself.
Cool video, it can't get any better than this.
@charles1matt Yes, if you're overgeared (too large of a pinion or too small of a spur gear) the motor will overheat. If that's the case just start taking teeth off of the pinion 1-2 at a time until you hit an acceptable temperature.
@fieryguns It's pretty robust. Plus it's made out of Z-Foam which can be re-glued with any sort of CA, it doesn't need to be the foam-safe variety. If you happen to brake something there's also a full line of replacement parts for both planes.
Do u know anything about the hpi jumpshot sc v2
This is awesome for a new person to hobby, now because of you I now know what type of pinion I'll ever need just by looking, and also taking into account the application I'll be using💎💎💎💎❤️👊🏿
Sounds like your setscrew on the pinion gear backed off is all. Check and see if you can move the gear on the output shaft of the motor. If it moves you just need to tighten the little screw down. If that isn't it I would check to make sure the slipper clutch is tight.
Thanks for sharing Sir👍👍👍
great video!! i finally feel like i have the basics of gearing down pat.
Very simplified thanks
@fieryguns Either the Stratos or Super Cub would be ideal for you. They are designed for the first-time pilot.
wow thanks this really helps i understand more how this works than before great video!!!
brilliant video love it
Thanks for the info I'm new to RC and bought a Losi Muggy and for now it's a little to fast for me so I'm trying to slow it down a little bit until I get use to it not to mention I'm hoping to get more torque for wheelies
I can't post links on UA-cam but I believe that TRA1951 is the part number you're looking for. If you check on our website you can see a photo to compare.
Anytime you increase RPM drop the pinion size. I'd say a 20T would be a good start from where you were at before.
I put like before ending see the video cause I already know how he's good explaining things, helped me once though... :)
It really all depends on the size of the track, along with how technical it is.
The problem is that you can get that size spur gear in a variety of pitches. Pitch and tooth count are completely independent from each other.
With the M05 you have an interesting challenge due to the fixed nature of the motor mounting system. For a brushless I am assuming you're running a 17.5? I think most people are running the largest pinion you can fit in there, so a 5.8:1. The fact that it is front vs rear wheel drive won't affect anything.
There is only one spur gear for ECX, 87T. I would drop a few teeth on the pinion from stock, 2-3 would be a good starting place. If your gear mesh and slipper are properly set there should be no reason the gears get stripped just by changing motors.
On the RC8B2 yes, that would be good. On the Rascal are you converting that to brushless? If so I believe the spur gear is also Mod 1 so a 14-17T pinion should get you in the range there.
I swear these videos are gold for rc wannabe kidz like me.
The plates should be but you'll need to get different slipper pads for what ever brand of spur you go with.
@fieryguns There's not a definitive range but it's easily as far as you can see.
It's not a horrible idea but I don't know how necessary I'd consider it. I have never used a metal gear diff with brushless in any of my race vehicles.
Super information about the gears!! Peace racers
There's nothing I'm aware of. Not only would you need to swap out the driveshafts but the differential outdrives too.
Define "Really Hot". 150-170 is about where you should expect things. Also what motor are you using, how much timing in the endbell and is there any timing or boost in the ESC?
@fieryguns All our products are rated for ages 14 and up. I'm not saying that a 13 or 9-year old couldn't fly it its just not what we recommend.
Great information. This helped me out.
thank you. nice presentation and good information
Omg your a genius.
Very informative 👍
In my 1/10 onroad colt rc car I built I run a dp32 15t pinion with a p2953 54t spur 120a esc and 5900kv motor and it gets 100+kmh on 2s Lipo best combo I reckon
Nice job explaining gearing. Can you recommend a short read that reinforces what you just demoed. I find it sinks in better. Thanx
how do you change a motor on an ECX roost without permanently screwing it up but make it faster at the same time?
I haven't used that combo before but I know the X-11 and X-12 LRP motors I have run in the past did run a little hotter than others. I'd drop 2-teeth on the pinion and test it from there. If it's still too hot just keep taking teeth off of the pinion.
ive got a axial scx10 with a supershafty bomb proof transmission and a tekin roc412 500kv motor what is the best choice for a pinion gear ? 32 or 48 p
Verry instructive video. I still have a question. If I want to go "in between", so more top speed and more acceleration. Is it possible using a spur gear with more teeth and a clutch bell with less teeth...??
outstanding video!!! thank you
How does this all translate to rpms?
76/33=2.30, transmission is 3.0*2.30=6.9fdr
3600*7.4=26640rpm/2.30= 11582rpms set to the transmission. Would you divide the rpm by the FDR or the spur/pinion ratio? So 11582rpms*3.0 transmission=34746rpms ?
I am still trying to achieve the most out of my new motor so I am trying to gain that good acceleration I had with my stock motor.
My Arrma infraction came with a 46 tooth gear. I ordered a replacement that said it was for my car came 50 tooth, is that ok?
@HorizonRCdotCom Thanks for the help man!
Horizon Hobbies I have the Kyosho Inferno Gt 2 Demon. I’m running stock 4s 100c 9000 man battery. It comes with a 17T pinion but I bought a 20T pinion. Is that good? Will it put too much torque on the motor?
i have a an evader brushless it has only ran one time so i put a new spur 48p 86t and a 23t pinion and it still slips
So I am new to the hobby and I'm building different vehicles. How do I find out the maximum gear ratio for any particular motor? How do I find out how low and how high I can go on pinion and spur gears?
I think most are running 17.5T or 13.5T motors in the Minis.
@fieryguns Well this is more for the surface crowd than the airplane or heli fans. What can we help you out with on planes?
You shouldn't have to change any capacitors when increasing voltage UNLESS they are not rated to handle that voltage.
👍👍👊👊📹📹 good info
Great video! I'm going to brushless with an RS4mt and I'm thinking about my gearing and heat. Does too high a gearing cause more heat? And what's the best way to start working down the gear if heat is an issue?
how much do gear modules (48DP, 64DP, etc.) matter? i may have ordered a wrong module pinion. how much will this affect it? (the gear fits, but i dunno)
This was a really great video! Thanks so much for doing this. One question I have is how do you decide whether to change the spur gear or the pinion gear. So if putting in a smaller pinion or a higher spur gear will give you more acceleration, what decides which one you switch? Or is it just trial and error to fine tune it?
It really is trial and error. I try to run the largest spur gear that leaves the motor as close to the centerline as possible. If I need to change up or down more than 3-4 teeth on the pinion I'll generally change the spur too.
It could be .6 module, basically "Metric 48-pitch". I am not familiar with that car or company so I don't know what it uses, sorry.
i hv a question. do they pinion n spur gear size contribute to the cogging problem on rc? tq
You almost hit on why you might want to use larger gears with close to or same ratio. Giving the flywheel effect might be minimal, the larger gears will still roll easier off throttle and allow the car to coast faster, or not slowdown as quick, with the throttle at neutral.
This is also true doing the opposite by using smaller gears, at a tighter track it could be advantageous to have the car slow easier with the throttle at neutral.
You never hit on rollout?!
You started to mention tire size and left it at bigger, higher ratio.
You can get a better ratio and keeping that sweet spot by calculating your rollout, how far the car travels per motor rotation/s.
Different tires with same rim sizes have different diameters and/or swell at high speeds depend on tread, design or compound.
On road cars benefit more from rollout calculations and the use of larger or smaller gear sets of the same ratio for the simpler drivetrains and/or tire wear.
Rollout calculations will use that math you never thought you’d use.
Great video learned plenty do you cover direct drive?
It shot up to 180 in three laps. The system is an LRP Spin Pro esc and LRP Vector K4 17.5 I do have the boost mode to 0 value/30 degrees of torque. Not sure about timing though.
Thanks.
i have a arctic hobby land rider 305 on road car. i converted to a brushless but the grub screw was rounded so i bought a new motor mount and i have bought 2 different pinions 48 pitch and 32 pitch the 32 is too big and the 48 is a little bit too small.. im confused
Which ratio is beat for short course parking lot racing of a traxxas slash.
If im running a rc on dirt concrete and grass what pionion is best 19t?
Thank you for the info!
Hi , i love the video ! Nice job , but i got a question . If i wanna make my car go faster what should i do ?
That's a decent amount of motor. I'd start around an 86T-spur with an 18T pinion.
In my 1/10 brushless truggy with 31 teeth pinion (25 stock) when it accelerates from standing position, i detect some hesitation like its going to switch gear up!
The same symptoms goes even worst when i change the pinion gear, with bigger one.
Im using 3s Lipo with 150Ah esc but the motor is stock (2400kv).
I don't think that's your gears, it may be the motor. If the brushless motor isn't sensored, then it can cause hesitation like that or start cogging.
Is that big spur gear a 82 teeth count? Or is that the pitch number.
Thank you!
I’m driving my VW Camper ‘60 RC across Scotland. How efficient can I make it…
I've actually waited with buying an engine yet as I know this model, and it seems most Tamiya models, don't seem to like Brushless and LiPo's very much. So I'm picking the engine based on what is possible with the gear ratio, I just want it to be rather swift, don't have to break speed records but neither do I want to get anywhere near toy-grade speeds. (Which in my book is 25 MPH/40 KPH.) So hoped to put something in that'll make it go around 30-40 MPH/48-64 KPH. Question is, how many Turns/kV?
This is a great video for us newbies!
Q: If I'm using a 13T double motor, should I be using a specific size/ tooth number pinion?
Or does the pinion have anything to do with motor turns?
@fieryguns What don't you get? What can we help you out with?
So on a slash racing oval track with 45 ft straights go with 90 20 or 86 18? both are similar ratio but different rotating mass. u said bigger spur more effecient? thanks great video!
Bigger gears always provide more of a "flywheel" effect, which is typically beneficial in most circumstances. Bigger gears are also easier to "mesh" together.
Horizon Hobby. Thanks for the fast reply! I have been researching this for a week or so after a friend of mine said I should drop from 90 to 86 spur. I have read alot and seems people but heads on this issue, because of the larger pinion size causing weight and stress on motor? I am gonna try going back to 90 like u said see how temps run. thanks again for the in depth video!
@@leeroyexcavator9149 If you are running an aluminum or plastic pinion, the weight difference between each size will be almost nothing.
8 years ago! Not sure if you still work there, but can you elaborate more on the last bit? How is it that the wheel size impacts the gearing? If I gear up (larger pinion), should I be dropping the size of my wheels at the same time?
If your using a larger pinion then you should use a smaller spur gear in most cases.
That's exactly what it was!!! The slipper clutch I set to factory specs, but I may e too right because I just snapped the left driveshaft to the wheel now. It's not the part that goes to the motor but to the wheel, the whole thing slides off in 2 pieces. The little pin snapped on the end where the metal piece holds the wheel. I have no local hobby shop near me. Do you sell these? Thank you very much for your help sir!
i have a ecx amp mt electric car and whn i push the throttle foward or back it sound like it going fast but bearly moving
Did you totally forget about the 1/16th scale? That would help a lot of Us who use them. The rules may generally apply across the board, but the specifics of that particular scale would be appreciated.
I have a brushless 1/16 Traxxas mini e-revo VXL and want to make it top-out in speed. Which exact pair of gears would I need?
No, I just didn't reference all scales in this video. Gear ratio calculations are the same regardless of scale. What MIGHT change is the pitch and number of teeth on the gears, but calculating the gear ratios are always the same.
A larger pinion and/or smaller spur gear would give you more top speed but less acceleration.
A smaller pinion and/or larger spur gear would give less top speed but more acceleration.
- Gary
hi mate thnks for video bt i would like to hv ur own advise abt my gearing..am converting a 1/5 scale harm to electric..am a bite out of fund due to expenses on esc,lipo n motor..i have the 730 kv and the 200 esc both trunigy trackstar..as my harm was petrol i was thinkin to keep my stock gearing which is 23 teeth pinion gear and 40 t spur gear.pinion gear r not so cheap and was thinking if these two pinion will be ok to use with this esc n motor,,what should i expect??top speed or acceleration?will it be safe aswell to use without overheating anythng or any other issue?if nt suitable what pinion gear do u reccomend?thnks
But... How do i make my rc car faster.... Bigger gears smaller gears.... Help me
nice intro lesson
I have an ECX Torment and I want to change out the drive shafts. My question is there any metal driveshafts out their I can use to swap out the plastic drive shafts on the Torment.
What vehicle do you have? A lot of time you just need to see it.
I have an ECX Torment 2wd and I just put a 9T brushed motor in it but I want to achieve more speed, so am I able to go up a gear for tooth or keep my stock ones? I use my ECX as like a Short course truck so I run it on grass and sand.
Good video
Thanks a lot!
I notice that there are multiple ways to get near the same FDR ie 104spur/52pinion = 3.800 fdr and so does 92spur/46pinion in my touring car how does that effect torque / acceleration? Or is 3.800 fdr just a 3.800 fdr no matter combination of spur/pinion?
While the FDR would be the same there are benefits and disadvantages to getting there with larger or smaller gears. Smaller gears have less rotating mass, therefore will spool up faster and yield better acceleration. However a larger gear will actually be more efficient at transferring power and, due to the slightly heavier rotating mass, have a bit of a flywheel effect which may increase corner speed when coasting.
Horizon Hobby Thanks!