Confused about gearing? Read this

[arogon1235]

if you need acceleration you would get a smaller pinion gear

[rcrallyuk]

Ta. If i get a small Pinion dont i need to get a larger spur

[moddedmartin]

Hi this is really useful and here it comes......but (lol) i dont know my internal revs is it?

I dont have a manual it was a magazine i think its missing so how do i find it put its a 550 brushed if its any good??

Thanks peeps

[Pistonhead]

Can anyone recommend gearing for 3s on a box stock firestorm flux? Want it to run cooler for a full 5000 mah pack instead of letting it cool down every 5 mins

[andrewd]

I have a hobbywing 17.5t motor ant the extreme stck esc any good setups and gearing in a t3

[EpicLURcher]

By the way i think Internal ratio is calculated by number of teeth on a driving object (e.g a spool) over the teeth on the lalyshaft(Not the pinion, the geraes that are driven by the pinion)

 

E.g on an xray T4, the spool is 38 t, the layshaft has 20.

 

38/ 20 = 1.9, which is the correct internal ratio for the T4

 

I think thats how it works!

[EpicLURcher]

@andrewd, I use a FDR between 4-4.1 for 17.5 in a t4. Thing with FDR is you can compare to other cars, so anyone running the same class as you you can directly compare FDR

[Skinso]

Can anyone recommend gearing for 3s on a box stock firestorm flux? Want it to run cooler for a full 5000 mah pack instead of letting it cool down every 5 mins

Did you ever get an answer to this? Just got myself a 3s for the firestorm

[Pistonhead]

Is it still stock? My esc didn't like 3s very much lol.

Either way i'm running a 16t pinion and stock spur if it helps bud. Can run 3s on it all day, til i break the car lol

[Monster LB]

So all of the previous suggest changing the pinion size based on what you already have. How do I go about choosing a pinion if I don't have one to start with? I have a 9t brushless etronix motor/esc going into the new Team Losi Racing 22-4 with a 2s saddle LiPo... Likely to be 5500mah . Any advice on where to start would be great please. I am looking at bashing initially but going forward running on dirt track. Once I have one, I don't mind playing around with different sizes but need a starting point as it doesn't come with the car.

Additionally, I know you get different sizes determined by no. of teeth but do you get different dimensions?

[boffy999]

Have a guess what I broke it today I clipped a post and bugger the from lower wish bone gone!! Bugger

[EpicLURcher]

So all of the previous suggest changing the pinion size based on what you already have. How do I go about choosing a pinion if I don't have one to start with? I have a 9t brushless etronix motor/esc going into the new Team Losi Racing 22-4 with a 2s saddle LiPo... Likely to be 5500mah . Any advice on where to start would be great please. I am looking at bashing initially but going forward running on dirt track. Once I have one, I don't mind playing around with different sizes but need a starting point as it doesn't come with the car.

Additionally, I know you get different sizes determined by no. of teeth but do you get different dimensions?

There are 3 main types- 48dp, 64dp and mod. I would recommend 48dp, however check what pitch you spur gear is running (pitch is what those numbers i listed refer to). I would see what the manual suggests- alot of manuals suggest pinions

Failing that stick a 20t on-make sure you get correct pitch for your spur

I say 20 because that is what i have heard 22 owners saying, never tried and might have mis heard though.

[Ted72]

Hi I am new to this I got my 1985 tamiya frog out the loft and when I press the controller to go forward it just makes a grinding & screeching noise but it goes in reverse could it be gears ? And is there a better gear upgrade for this old frog thanks

[piglet]

Hi guys, newbie here. I just ordered EZRUN 5.5T 6000kv - http://www.ebay.com/itm/171521237060 for my TT01ES - http://www.tamiyausa.com/product/item.php?product-id=46625

Like I'm reading more and more I realised that it's not exactly what I wanted. My fault. Yes, I wanted more speed, but I'd like to have also acceleration. This 5.5T is too much I believe.

Could anyone help and suggest pitch and spur to achieve reasonably speed and acceleration. I'm newbie and don't want to break something on first run. Thank you for your help.

[Brandon]

hello! Just curious to know how I find out the pitch of my spur, as my one I bought, never said what pitch it was 

[SWRCGUY]

Brilliant thread, taught me a ton in 2 minutes and i got it!

Cheers,

[Hornet neil]

Hi

just looked at all the posts and none of the links seem to be working 

all I get is thinks about jobs

[Nick46]

Same here. I've just tried all the links and none work.

Sent from my SM-G800F using Tapatalk

[Lone-wolf]

Here is a problem, i have just got an ftx outlaw brushed running 15T motor with 17tooth pinion on a 62 tooth spur, they are known for getting a hot motor, and short run times, so want to use 2s lipo for longer run times, i also want to reduce the top speed as this was not bought for all out speed and the lipo will make it faster, so i have ordered a 35T motor, but i could do with dropping down the pinion to say 14, problem is the motor mount in non adjustable, so how do i go about meshing the gears

[Paul Busby]

Old thread revival, but I have been trying to validate my own google sheets calculator in my RC Parts reference sheet:

https://docs.google.com/spreadsheets/d/1hsQBVZHxqyHskx2CS3niMWIqGJePsbG1hEpCDrVZXFM/edit#gid=212831620

 

I think I've done something wrong as my calculations put the theoretical speed of my Kraton on full 6s with the speed pinion (16t) at 75mph with the stock tires... that aint right?

This calculator: http://www.radiocontrolinfo.com/information/rc-calculators/rc-car-calculator/

Gives me an output of 62mph dead, but it doesnt say what voltage it uses for the cells. Even if I use 3.7v, I get a speed of 66 with my calculator.

 

So just like in school, show your workings:

Step 1 - Motor RPM

Motor KV * Battery Voltage (6s) = Motor RPM
2200 * 25.2 = 55440

 

Step 2 - Internal Drive ratio

Idea here is to find out how many revolutions of the motor it takes to make 1 full turn of your internal drive system. I just have a diff, no transmission, so:

Spur / Pinion = Internal Drive Ratio

50 / 16 = 3.13:1

(note - this means the RPM of the IDr is 55440/3.13 = 17740.8. If you have a transmission, you can either do the math to figure out the ratio, or just look at the manual )

 

Step 3 - Gearbox/External Drive Ratio

Now we can work out how many turns of the internal drive system it takes to turn the drive shafts one full revolution.

Spur / Pinion = External Drive Ratio

43 / 10 = 4.3:1

(note - this means the RPM of the EDr is 17740.8/4.3 = 4125.77)

 

Step 4 - Final Drive

Here we are merging the two ratios calculated separately in step 2 for IDr and step 3 EDr as a single ratio. This a single ratio that tells you how many times it takes the motor to turn for one full revolution, through the whole driveline, to the driveshafts going to the wheels.

IDr * EDr = FDr

3.13 * 4.3 = 13.44:1

(note - Calculating the RPM here results in the same as step 3, as that is also calculating the final RPM of the external drive shafts going to the wheels.  In this case, you take the original RPM of the motor worked out above, and divide that by the FDr  55440/13.44 = 4125.77)

 

Step 5 - Wheel and Tyre Circumference

Idea here is to find out how far each wheel will travel for each full revolution.

So to find out the circumference, you just need pi (3.142) and the diameter of the wheel, best to use inches here seeing as I'm working out MPH.

Wheel Diameter (I'm calculating for the Minokawa LP)* Pi = Wheel circumference

6.14 * 3.142 = 19.29

 

Step 6 - Theoretical Max Speed

So with everything we have above, we now have everything we need to calculate the speed.

We take the final RPM calculated in step 3 or 4, and multiply this by how far the wheel travels every revolution (its circumference).

Final RPM * Wheel circumference = Inch Per Minute

3634.6 * 19.29 = 70111.434

Obviously this is a silly number, so we x 60 to make it inch per hours, then to make inches into miles, you divide by 63360

70111.434 x 60 = 4206686.04

4206686.04/63360 = 75.38MPH

 

Anyone want to tell me where I'm going wrong, or am I right?

(Note: I have deliberately broken this up into pieces to try and help people go through the process, I'm aware this can be put into a much more simple formula. I'm also aware that this is theoretical, so don't need all the things which would cause the theoretical to not match with reality to be pointed out... this is strictly a maths question)

 

 

Edited January 28, 2020 by Paul Busby

[Pendelton]

Thanks again Garry.

[Paul Busby]

I'm a bit upset noone replied to my post on this ☹️

[locky]

On 28/01/2020 at 23:21, Paul Busby said:

Old thread revival, but I have been trying to validate my own google sheets calculator in my RC Parts reference sheet:

https://docs.google.com/spreadsheets/d/1hsQBVZHxqyHskx2CS3niMWIqGJePsbG1hEpCDrVZXFM/edit#gid=212831620

 

I think I've done something wrong as my calculations put the theoretical speed of my Kraton on full 6s with the speed pinion (16t) at 75mph with the stock tires... that aint right?

This calculator: http://www.radiocontrolinfo.com/information/rc-calculators/rc-car-calculator/

Gives me an output of 62mph dead, but it doesnt say what voltage it uses for the cells. Even if I use 3.7v, I get a speed of 66 with my calculator.

 

So just like in school, show your workings:

Step 1 - Motor RPM

Motor KV * Battery Voltage (6s) = Motor RPM
2200 * 25.2 = 55440

 

Step 2 - Internal Drive ratio

Idea here is to find out how many revolutions of the motor it takes to make 1 full turn of your internal drive system. I just have a diff, no transmission, so:

Spur / Pinion = Internal Drive Ratio

50 / 16 = 3.13:1

(note - this means the RPM of the IDr is 55440/3.13 = 17740.8. If you have a transmission, you can either do the math to figure out the ratio, or just look at the manual )

 

Step 3 - Gearbox/External Drive Ratio

Now we can work out how many turns of the internal drive system it takes to turn the drive shafts one full revolution.

Spur / Pinion = External Drive Ratio

43 / 10 = 4.3:1

(note - this means the RPM of the EDr is 17740.8/4.3 = 4125.77)

 

Step 4 - Final Drive

Here we are merging the two ratios calculated separately in step 2 for IDr and step 3 EDr as a single ratio. This a single ratio that tells you how many times it takes the motor to turn for one full revolution, through the whole driveline, to the driveshafts going to the wheels.

IDr * EDr = FDr

3.13 * 4.3 = 13.44:1

(note - Calculating the RPM here results in the same as step 3, as that is also calculating the final RPM of the external drive shafts going to the wheels.  In this case, you take the original RPM of the motor worked out above, and divide that by the FDr  55440/13.44 = 4125.77)

 

Step 5 - Wheel and Tyre Circumference

Idea here is to find out how far each wheel will travel for each full revolution.

So to find out the circumference, you just need pi (3.142) and the diameter of the wheel, best to use inches here seeing as I'm working out MPH.

Wheel Diameter (I'm calculating for the Minokawa LP)* Pi = Wheel circumference

6.14 * 3.142 = 19.29

 

Step 6 - Theoretical Max Speed

So with everything we have above, we now have everything we need to calculate the speed.

We take the final RPM calculated in step 3 or 4, and multiply this by how far the wheel travels every revolution (its circumference).

Final RPM * Wheel circumference = Inch Per Minute

3634.6 * 19.29 = 70111.434

Obviously this is a silly number, so we x 60 to make it inch per hours, then to make inches into miles, you divide by 63360

70111.434 x 60 = 4206686.04

4206686.04/63360 = 75.38MPH

 

Anyone want to tell me where I'm going wrong, or am I right?

(Note: I have deliberately broken this up into pieces to try and help people go through the process, I'm aware this can be put into a much more simple formula. I'm also aware that this is theoretical, so don't need all the things which would cause the theoretical to not match with reality to be pointed out... this is strictly a maths question)

 

 

Been a while and generally use this tool, it may be wrong as just quickly inputted your values but have a look...https://scriptasylum.com/rc_speed/top_speed.html

[m4inbrain]

Haven't even seen this, for some reason i never check the stickies.

 

Yeah of course, something's way off. 

 

If i use my go-to calculator, it spits out 61.5 mph, which honestly sounds about right. 75mph doesn't sound at all right - the motor you're using is only 150kv faster, but your tyres are 15mm less in diameter than a stock Kraton. A stock Kraton goes around 59-62mph according to GPS (depends on the video you're watching, but always this ball park). 

 

 

[Paul Busby]

Just now, m4inbrain said:

Haven't even seen this, for some reason i never check the stickies.

 

Yeah of course, something's way off. 

 

If i use my go-to calculator, it spits out 61.5 mph, which honestly sounds about right. 75mph doesn't sound at all right - the motor you're using is only 150kv faster, but your tyres are 15mm less in diameter than a stock Kraton. A stock Kraton goes around 59-62mph according to GPS (depends on the video you're watching, but always this ball park). 

 

 

In fairness, I was calculating the stock motor as 2200kv, when it's actually 2050kv... that was my error.

 

This is what my calculator spits out now with more correct info and a 13T:

 

Sounds about right to me.