# Gearing a Brushless motor???



## JustaG3

Now that I got my charging issues worked out(lipo batt.),,, how about some advice on gearing for a brushless motor??? I'm using a 87 spur, with a 7.5 motor(LRP) in my T4,,,, what pinion gear should I be using????


----------



## 420 Tech R/C

I am running a 8.5 in my t4 running a 20- 87 so I would guess around a 18 or 19 for the 7.5.


----------



## JustaG3

Is there some kind of chart anywhere that tells what a brushless motor is equal to a brushed motor???? example a 17.5 = to a 21 turn brushed motor?

Tech, thanks again for your help, and I will try the 18 pinion, just don't want to blow up!


----------



## TamiyaTimNJ

I'm glad to read that your charging issues are worked out. I know that first LiPo can be a little scary and you don't want to ruin it or blow anything up. Charging that thing will become 2nd nature after going through the process a few times. 

I have a 6.5 LRP Sphere/Vector combo in my T4 and I run 87/17 mostly. I also run 87/18, 84/17, 84/18 and a few other ratios right in that ballpark when I want to *really* dial in the power output based on the track layout and the traction conditions.

Tech's suggestion (18 or 19T pinion) is pretty much right on for your 7.5. Just one tip: Make sure you check the motor & ESC temp often. The extra juice the LiPo provides has a tendency to heat things up fast. 

Tim


----------



## 420 Tech R/C

and use the slipper!!!! BL motors will kill diffs from the torque when you land off jumps so set your slipper up good!a 17.5 is equal to a 27t stock, a 13,5 is equal to a 19t, a 10.5 is equal to a 15t or 16t, a 8.5 is equal to a 12t, from there on down its all about gearing.a 5.5 geared right feels like a 10t brushedor if you under gear it it feels like a 12t with a whole butload more torque over geared it runs like a 8 or 9t, so you see what I am saying.


----------



## JustaG3

are these numbers for a stock rotor or the sintered? and does this matter????


----------



## 420 Tech R/C

max RPM stays the same with either the bonded or sintered rotor, the only thing that changes is the torque curve. so a 8.5 with a bonded rotor will be a little softer out of the hole than an 8.5 with a sintered rotor both running the same gear ratio, but top end will remain the same.


----------



## JustaG3

Got the T4 out today, and I must say this thing is makin me smile! Running a LRP 7.5,,,, had 87 spur with a 18 pinion,,,, seemed to me alittle warm, but ran great and did'nt shut off,,,,,,,,,,,,should I try a 16 or 17 pinion, and what kind of temps should I be lookin for???? And is the motor heatsink handy??


----------



## nutz4rc

If the top end is the same and low end torque is softer in bonded rotor motor, why is the gearing recommendation so much different for the bonded vs sintered? I have a Novak XBR and 13.5 EX and still trying to figure out how to gear in my XXXT. Novak instructions say 4 teeth lower than stock. This seems to be too low based on the previous statements? Not questioning you just trying to figure out where to go. Thanks.


----------



## 420 Tech R/C

because the bonded rotors do not deal with heat as well as the sintered rotors.heat causes the rotor to loose some of its magnetism. the bonded rotor motors are recomended to be undergeared for this reason, to reduce motor temps and to extend the life of the bonded rotor.you CAN gear a bonded rotor motor the same as a sintered rotor motor and get very similar performance UNTIL the heat starts to effect the magnetic feild of the bonded rotor.


----------



## nutz4rc

Thanks. I thought heat was the enemy. That is good news because I haven't topped a 100 degrees yet so I think I can gear up some more. Novak says 160 to 170 is a good heat range.


----------



## lordraptor1

try this if you are having a problem:

http://www.comeseethis.com/gearing/Default.aspx


----------



## NovakTwo

TeamNovak's NovaGear app

Coming Soon!


----------



## lordraptor1

NovakTwo said:


> TeamNovak's NovaGear app
> 
> Coming Soon!


not good for everyone, not everyone has an ipod, ipad, itouch, or droid (at least i dont ).


----------



## lordraptor1

nutz4rc said:


> Thanks. I thought heat was the enemy. That is good news because I haven't topped a 100 degrees yet so I think I can gear up some more. Novak says 160 to 170 is a good heat range.


check with your motor manufacturer for their heat recommendations, although this method may nopt wrok for all motors (getting help from traxxas has been like pulling hens teeth in my case). i read on novaks site to gear it according to temps so i am assuming they mean gear it up till the motor is up to but not higher than 160F. if i remember the page it said something about the motor would have issues after that and if kept running could damage esc as well. 


this is what i was reading:

http://teamnovak.com/tech_info/brushless_motor_notice/index.html


----------



## lordraptor1

420 Tech R/C said:


> and use the slipper!!!! BL motors will kill diffs from the torque when you land off jumps so set your slipper up good!a 17.5 is equal to a 27t stock, a 13,5 is equal to a 19t, a 10.5 is equal to a 15t or 16t, a 8.5 is equal to a 12t, from there on down its all about gearing.a 5.5 geared right feels like a 10t brushedor if you under gear it it feels like a 12t with a whole butload more torque over geared it runs like a 8 or 9t, so you see what I am saying.


just curious as to if you are sure about an 8.5t being comparable to a 12t brushed motor? and if you are would it matter if the 12t brushed was a single, double, triple, etc.?

im only asking because i have a skyrc cheetah in my T4 ( same gearing as you mentioned 20/87), but i recently ordered another 8.5t cheetah system to put into my old graphite plate FT TC4 ( which has a barely used trinity speedgems pro nitronite 12t double in it) and i have had a hell of a time trying to find any gearing recommendations. on the skyrc website they show 6.4:1 for medium size tracks and 7.1 for short tight tracks.

i did look at TQ racing gear chart and found that the best all around to get tclosest to and have multiple options would be a 71t spur ( which is proving to be a mythincal beast in terms of the kimbrough gears whether it be "kimbrough" or the associated branded kimbroughs which puts me at the stock 72t spur and multiple pinions or a 69t spur and multiple pinions.

my FT TC4 is now just run in parking lots as there is no track here and both tracks that were within a 3 hour round trip drive have shut down.

side note as to the 20/87 gearing on a T4 motor temps never get about 130, however 1 the truck isnt very fast and 2 my slipper setup overheats ( i mean hot enough to get burned on metal slipper disks) and wears out the pads after a minute or 2 and setting per instruction manual is pointless as it just slips and truck wont move. i have converted it to vts slipper, and just ordered an aftermarket vented setup which hasnt arrived yet. any advice on setting the slipper bud? how about advice on gearing my ft tc4 for the skyrc cheetah 8.5t 4000Kv setup?


----------

