Amazing how that works LOL...on stock gearing my Kraton was quick, geared up it was a monster !!!

Overkill, I'm glad you have a good understanding of gearing concept that I shared.
I will not argue what is your opinion and what is the fact when it comes to watts/power and your experience.

However, when you claim that you have more low end acceleration in 34/32 gearing than 15/44. The claim raises questions to me.

I'm not here to argue or prove you wrong in any aspect. I want to share the information that is correct with the fellow forum members. Please do not be insulted or offended by any means.

Since this is Tekno MT410 thread, I will focus on to this chassis. It has 44T spur and you can choose wide range of pinions from 15T to 25T.
To relate to this chassis, let's keep the spur fixed at 44T as provided by the manufacturer.

Would you agree 15T pinion has more low end acceleration than 25T pinion?

my 2 cents :

it may simply be a missundertanding about the FEELING you get of torque : with a 15/44 ratio, there is no doubt that you get more pure torque Newton/meter on the wheel, but less total end speed. with the 15/44 ratio, you may have the feeling that the motor quickly reaches his highest RPM. some may think too quickly. this can lead to the feeling of no torque and not enough speed...

on the other hand, with a 25/44 ratio, you will get a bit less torque and much more endspeed ( and a burning hot motor... ). But the feeling you get is more satisfying : you can feel the motor battling to reach its highest rpm and you see the vehicule driving fast before reaching the motor's highest RPM. You have the feeling to drive on torque, not on RPM. just like a diesel motor.

I proceed this way to gear : I put the highest pinion I can without overheating the motor !!

With a fixed spur size, lets say 40T

If you put a 12t pinion on it will accelerate very quickly and will not have great top speed.

Now put a 17t pinion you will get a slower initial acceleration but a much higher top speed.

This is fact and is reflected in the real world, for example in drag racing a "smaller pinion" is put in the rear differential to give it initial fast acceleration and just enough top speed to get it to the line to get the fastest time in the shortest distance.

Now if you take for example top speed runs like on the salt flats you will see these cars do not have great take off speed and will need some time to build up speed but there top speed will be insane as they essentially have a "big pinion"

Smaller pinion faster acceleration lower top speed
Bigger pinion slower acceleration higher top speed

I agree. In my experience with brushless/Lipo electric. When I gear up, it wheelies easier all the way up to top speed. When I gear down it wheelies easy going slow but nothing once you get going because it doesn't go as fast. Basically gearing down grossly underuses the power available. Gear it up and you can wheelie down low and up high. The only downside is heat. In my experience, I puff my battery before I overheat the motor or ESC. I had a high dollar/high C rated Thunder Power 4s lipo in my MT4. I geared it too high and puffed the battery. I switched to 6s and everything ran cool. Only problem was I started destroying diffs! Lol!

Let me start by saying I do see you try to approach this constructively, which is cool - so let me try and do the same.

Yes, lower gearing results in higher Torque at the wheel axle. However, higher wheel-axle Torque, does not by definition mean higher usable acceleration and higher "wheelie-potential". Think of a Crawler type ultra low gearing: will it have huge wheel-axle Torque? Yes. Will it do standing back-flips and win drag races? No. Gearing 101 man :).

Why? Motion does not just involve Torque; Torque is just a static property. Motion involves Power... which brings RPM in the equation as well: Power=Torque x angular velocity (sort of RPM, but different unit).

An additional factor that contributes to all the common misunderstanding of how this all works is that the Torque produced by a motor or engine is dependent on RPM, and that PMDC motors have a falling Torque-RPM curve (max Torque at zero RPM, zero Torque at max RPM), which is fundamentally different than with the combustion engines, people are used to driving in their cars. Finally, typical 1/8 brushless set-ups will have so much Power potential, that traction is the limiting factor in acceleration, not the reduction in wheel-axle Torque caused by higher gearing. Here's some more discussion on what I mean with that: https://www.rcgroups.com/forums/show...-GT2-1-8/page3. Read until bottom for easier to comprehend figures and let me know if you find a flaw in the reasoning.

Like Kms, I'm not here to argue or convince anyone. Feel free to believe whatever you want, collect and process the info that is out there, combine that with your own experiences and make up your own mind.

Exciting when you find a fellow believer right?

In your excitement, you forgot to answer my question though... which leads me to believe you are running your ET48 on 140 mm diameter, 220g Truggy tires, which renders your input useless :).


Pic or it didn't happen (b000000ring explanation here http://www.rcgroups.com/forums/showt...-GT2-1-8/page3):
http://www.rctech.net/forum/members/...e-vs-speed.jpg

TLDR: Gearing up increases Power, acceleration, speed and flippage!!11!! Bro :D.

Dr T your explanation is great, a few things to consider are for example your crawler statement, no it won't do back flips but this is purely due to the power input. If you had 2 exact same motor spec crawlers side by side, one having a lower gearing than the other, one will certainly take off quicker and accelerate harder to a certain point until it reaches peak rpm of the motor and the taller geared crawler will eventually chase the other down.

Now put an 8 scale motor in one of them and it will most certainly do back flips and all kinds of crazy stuff, to a certain point. If it is too over geared it won't do any back flips or may not even move at all and probably burn out. Voltage input obviously also comes into play with electric motors. So power input plays a big part in determining best gearing for what situation you are running your vehicle IE, drag racing, speed runs, crawling etc.

Look at tc's, if you run 21.5 you will have a huge pinion to get you that higher speed as the motor simply doesn't have the rpm to take it there with a small pinion, whereas a mod motor like a 4.5 will tend to run smaller pinions as it has the rpm to get it to high speed due to a higher kv. Torque and power are basically the same whether its an IC engine or electric motor granted they apply it in a different manner. Gearing helps you get the most out of your power input.

Dr.T,

I appreciate your feedback and your comments. You have shined a light on interesting concepts of torque such as Angular Momentum, Wheel Axle Torque, traction, and power potential.

Although I am an engineer in F1 industry, your explanation was hard to follow with many variables you have introduced but it was certainly interesting.

So to make this conversation simpler, I want to ask you if we can hold all the variables fixed. Blarks and I have suggested this by suggesting "Fixed Spur gear" and only changing pinion gear. We wanted to claim that higher pinion gear will result in more top speed but less acceleration and lower pinion gear will result in less top speed but more acceleration. This goes back to Brandon32689's original question.

Dr.T, if I may suggest, lets approach this issue scientifically. You have brought up examples of Crawler, and other GT cars.

Let's imagine two same vehicles. Because this is MT410 thread, let's imagine MT410. Two same identical MT410 vehicles. This will help us eliminate variables that you have mentioned such as traction, power potential and many more.

- They will have same internal gear ratio
- They will have same tires
- They will be ran on same surface
- They will have same power system (let's say 2200KV motor with same ESC)
- They will have same weight and battery
- Everything will be the same.

The only difference between two vehicles would be the PINION gear.

1. First vehicle will have 15T
2. Second vehicle will have 25T

Gearing ratio is calculated by SPUR GEAR / PINION GEAR X Internal Gear Ratio

Since in this example, we have same internal gear ratio we will assume it as 1.

The spur gear in this particular vehicle MT410 is 44T.

Therefore, gearing ratio for each vehicle will be
1. 44T / 15T = 2.93
2. 44T / 25T = 1.76

In Gearing 101, you and I both understand that the lower the gearing ratio, the less acceleration it will have and more top speed?
It is visa versa. The higher gearing ratio, the more acceleration and less top speed it will have.

If you do not agree with my above statement, please let me know. Then, this debate is about the fundamentals of gearing ratio

https://en.wikipedia.org/wiki/Gear_train

By the way, Blarks and Ezlight, thank you for your contribution. I am still waiting on Overkill to share his opinion as well.

I'm running a 32T spur on the Tekno chassis. No, I have A LOT more low end acceleration with a 25T pinion, it's not even close.

Clearly understood. I appreciate your feedback.

It is one's choice to decide what is right and wrong.

I will stand by blarks and my previous statement that lower pinion will provide more instant torque in low end acceleration.

You have stated that higher pinion will provide more low end acceleration. Seems like we're at a stalemate. So be it.

Nonetheless, thank you for sharing your experience

Big Squids MT410 review.

http://www.bigsquidrc.com/tekno-rc-m...-truck-review/

Competition X MT 410 Review

http://www.competitionx.com/news-fee...monster-truck/

For those who want more information on gearing from a trusted source, please take a look at OFFICIAL Team Associated Gearing guide posted below.

https://www.teamassociated.com/pdf/c...ear_ratios.pdf

Too bad to read you couldn't follow, this isn't really rocket science, but let me try again:

Yes, I do not agree with your upper statement. Adhering to the definition of gearing ratio you posted (so spur/pinion), increasing gearing ratio (so bigger spur or smaller pinion) will increase Torque at the wheel-axle and lower top speed. The increase in Torque at the wheel-axle, will indeed increase angular acceleration of the wheel; so far we do agree (I thought that was clear from my earlier explanation...). The mistake you and many others make however, is assuming that this increase in rotational acceleration of the wheels automatically leads to an increase in longitudinal acceleration of the vehicle. By doing that, you are assuming that the power-plant is not able to put out enough power to break traction... This might be true for small, weakly powered brushed set-ups (or when driving the average gas car to work), but it is not remotely true for the typical 1/8 brushless power-plants.

Personally, I have never been able to gear a brushless car high enough (i.e., low enough gear ratio in your spur/pinion preference - if anyone's confused now, blame Kms with his wiki reference ;)) to not be able to break traction anymore for a big part of the speed range.

If you're really an engineer, ask yourself: do you really think a car set-up that is able to break traction already over the first portion of the speed range, will be able to increase acceleration (of the car! not the increase in wheel RPM :)) in that speed range by gearing down further (higher gear ratio in your spur/pinion preference)? If in doubt, consult your F1 team mates :).

Oh btw, I'm a big F1 fan. Looking forward to see what Chase Carey can do for the sport.