View Full Version : Gearing question, acceleration

07-13-2004, 08:40 PM
Ok, me and a another person are having an argueement right now on gearing and acceleration. When you gear it up like say from 18/72 to 24/72, wouldn't you gain loose torque and increase acceleration? Or would you loose torque and loose acceleration also? I say the first one is the truth, and the other person says it's the second one. Pease tell us who is right and who is wrong...

PS, these are numbers out of my head...

07-13-2004, 08:44 PM
I think if you leave the spur alone and increase teeth on the pinion, you will loose acceleration but gain top speed. you should be loosing torque as well

07-13-2004, 08:55 PM
Yeah, I just asked my uncle(he showed up after I made this post), and it increases top speed, but decreased torque and acceleration. It does that because of the power it used to spin the bigger pinion. So I can go and eat my words and everything I have to. Well, Thank you cheerwhiner for the quick response, that was only 4 minutes after I posted this thead(damn, that's fast!).

But, I have another question, how do you find torque in a BL motor? For my aplication I want to use, a 1940/6 on 14 ofthese cells(here (http://integy.automated-shops.com/cgi-bin/webc.cgi/st_prod.html?p_prodid=2195&p_catid=56&sid=4wSJJh0-d7kZ8eH-35104531836.7e))? And with 30 of those cells on the 2250/10?

07-13-2004, 09:06 PM
now you've lost me!!

07-13-2004, 11:28 PM
Fist off, all those things you mentioned will cost over $750 bux...you got that kind of money?

07-14-2004, 12:53 AM
...When you gear it up like say from 18/72 to 24/72, wouldn't you gain loose torque and increase acceleration? Or would you loose torque and loose acceleration also?...

Second is correct. "Torque" for our practical purposes, is the ability to move the load, which is really part of accelleration. With the higher (24/72) pinion, you are decreasing your ability to get the load moving from a dead stop.

BUT that higher gearing you will have a higher overall TOP SPEED. You just wouldn't get there as quickly.

07-14-2004, 01:26 AM
Fist off, all those things you mentioned will cost over $750 bux...you got that kind of money?

Who cares about the money!

07-14-2004, 02:13 AM
Me, because if he doesnt have the money, I wouldnt want other people that REALLY explain things in a long drawn out manner to waste their time if he isnt acctually going to even run all that. :)

07-14-2004, 11:25 AM
I really know nothing about brushless

07-14-2004, 02:07 PM
Yeah, not many people know too much about them...I know craps is knowledgeable on the subject...Seems like he was ridiculed for liking lipo's, now everyone goes to him with lipo and brushless questions cause they want em now...

Poor Craps. :D

07-14-2004, 08:43 PM
Well, the 1940 is going to be the one I am wanting. So I am going to be getting the ESC soon(that's $405 for the ESC), and my friend is getting the 2250, and getting the $600+ ESC. So if I was going to ask one, I thought I would make it easier and ask about both of them. Thank you very much for the info guys. And also, does anyone have the eqation for the torque? I remember seeing one, but now I can't find it. And I know it has somthing to do with the amps. :?

Chris LaPanse
07-14-2004, 10:39 PM
Yes, it does relate to the amps. I don't know the exact formula, but I do know the more turns and the more amps, the more torque.

07-15-2004, 09:11 AM
Actually, after some discussion and input from Big Jim, a definitive source in RC Motors, you actually can gain punch as well as top end. From how I understood his explanation, motors make most of there torque at the lower end of the RPM range. They don't perform like how a nitro engine would. Thats why a properly geared motor will give booth great punch and top end.

for more info on this check out www.rccars.com and go to the Big Jim motor forum.

07-15-2004, 12:07 PM
You mean finding an optimum between the two, correct? As in the correct gearing optimizes both low end and high end?

Big Jim rocks. :D

07-15-2004, 12:44 PM
Very interesting. Because I was thinking about going with the 1940/6(or 8, whichever is the lowest turn) series, and use 14 integy 1.22 volt batteries to get it at about 44,000 RPM in an E-Maxx, or 1/8 buggy. And use the 18.149 ESC for the job too. Would that give me enough torque? I am wanting to atleast give the record in the E-Maxx a shot. And I am thinking this might beable to do it if I used the lightest parts emaginable, and arodynamics also?

07-15-2004, 12:45 PM
Yeah, I think he means like, finding the "sweet spot" for the motor.

Ive never heard of Big Jim. :D

07-15-2004, 12:46 PM
Not a chance in getting the record buddy, Ive seen guys with Twin Hacker C50s geared up...Quick stuffs. :D

07-15-2004, 12:49 PM
Ive never heard of Big Jim.
Are you being facetious or serious?

Big Jim Greenmeyer was making motor mods before I even got into ground RC, I've still got some of his old 27T stocks over 12 years old or so. They're totally thrashed and worn out, but still run. Next to an off-the-shelf Trinity or other Yokomo can, they totally kicked A right out of the bag. They always came with a dyno sheet and full specs, and were great motors.

07-15-2004, 12:51 PM
I was being for real. ;)

My Chameleon Pro comes with Dyno specs too. :p

07-15-2004, 12:59 PM
Big Jim is pretty much the man when it comes to motors right now as Mike Reedy Retired.

Using big jims methods, my motors finally started to perform for A-main appearances instead of trash can jump shots.

Using his rules on a true RC track, I try to go higher on my pinion size till I find my lap times drop off or I am not topping out at the end of the longest straight. This methods works great for all my motors that I have had. I think the main thing is paying attention to finding a good starting point. With trinity motors, you have to be careful as they will go poof on you really quick if you are over or undergeared.

07-15-2004, 01:15 PM
nm... :o

07-15-2004, 01:18 PM
Don't be shy.... :D

07-15-2004, 01:19 PM
I found the 'answer' to my query ;)

07-15-2004, 01:22 PM
Ahhh, reading yields marvelous results. :D

07-15-2004, 01:28 PM
Ok then; here it is : :D
'...This is how you get your most speed. You can then adjust for run-time, infield punch, or motor temp...'

'...Your lap times are the only criteria to use for proper gearing. Nothing else matters. Not motor temp and not maximum runtime...' (http://www.rccars.com/forums/showthread.php?threadid=440 )

But on his site, it doesn't say that motor temp doesn't matter... :confused:

07-16-2004, 12:40 AM
Not a chance in getting the record buddy, Ive seen guys with Twin Hacker C50s geared up...Quick stuffs. :D

Probalby because of too much weight. And Promod used one motor and still got 70MPH+. Also, what other stuff did they use? I am worrying about getting the lightest stuff avalible. Arodynamics is the main thing when it comes down to it. If he(Promod) would of made the body a little bit lower and used a crowd pleaser for it, he could of gone just a little bit faster, maybe. Just like NASCAR, when you get a little body damage, your arodynamics are messed up, and you can't get full speed or handle right...

So, I like the motor talk, go ahead and use this thread for that, more info for me. :cool: But I would just like for one thing, can I get an answer about the torque for the 1950 motor? :rolleyes:

07-17-2004, 04:27 AM
For determining how to gear a motor to achieve a certain power result is knowing or having an idea of the motor's power curve. Motors may have a 5-6 tooth spread when they make certain levels of power. 16-18 tooth may be the range for good low end torque (less accerleration) 19-20 may be ideal for both low end power and acceleration while 21-22 is ideal for acceleration. Using a pinion 1 tooth in either direction would lead to overgearing or undergearing the motor.

That is one reason for a lot of misinterpretation with electric motors, we tend to think of low, middle and upper power range like gas motors. In gas engines you can setup some up to produce better mid range power for electric rc motors they have a low and upper power range - gearing is used to make the best of one or the other or finding a compromise where you get the best of both.

07-17-2004, 11:43 AM
...16-18 tooth may be the range for good low end torque (less accerleration) 19-20 may be ideal for both low end power and acceleration while 21-22 is ideal for acceleration.....

Don't you mean top speed here? Aren't we using the word "acceleration" to describe the ability to get from stop or low-speed up to the maximum speed with that gearing? In which case, lower gearing would achieve that faster . . . wouldn't it?

07-17-2004, 02:39 PM
People sure seem to get confused on gearing. With the spur being the same,
a smaller pinion is lower gearing-quicker acceleration to desired speed.
A larger pinion is higher gearing, giving slower acceleration to top speed.
The larger pinion gives a higher top speed, but won't punch off the line, or through infield jumps as well(but good torque helps).
IMO, you don't have less torque with tall(high) gearing, its just not in the(your) powerband to make use of it.
If your motor makes its best power around 30,000 and you gear tall(high), and never get to 30,000, you won't make use of your power and your motor(electric of nitro) will feel slugish.

07-17-2004, 04:57 PM
Yeah, you would think that the bigger the pinion, the more acceleration, but it puts more "load" on the motor, so it will take more power to get it up to speed, so it loosed acceleration. I had a big arguement over this a couple nights ago, I lost. That is why I created this thread to begin with, and kept this thread for the AMP thing. It all relates one way or another.

hiroller-How big of an area would the 1940 need to be to get it up to speed with a stock spur on a 22 pinion with about 19 volts spinning it to about 44,000 RPM acording to the specs of the motor? Also on a 22/72 setup?