Go Back  R/C Tech Forums > General Forums > Electric Off-Road
Question about motor turns and gear ratio >

Question about motor turns and gear ratio

Like Tree4Likes
  • 1 Post By Alexv2024
  • 1 Post By Alexv2024
  • 2 Post By trf211

Question about motor turns and gear ratio

Reply

Old 07-12-2019, 11:48 AM
  #1  
Tech Master
Thread Starter
 
Sir 51D3WAYS's Avatar
 
Join Date: Jun 2011
Location: Somewhere in this Universe
Posts: 1,525
Default Question about motor turns and gear ratio

For all my RCing life, I've always known that as a general rule of thumb, the lower the motors' turn rating the higher your gear ratio, and vice versa. Higher turn motors produce more torque, so can pull off lower gear ratios. Now, of course you are allowed to deviate slightly from an "ideal" gear ratio to prioritise acceleration or top speed depending on the track layout and personal preference.

I have the following dilemma. I run on an extremely tight and compact track, so much so that I never max out my buggy's speed. Clearly, I'm never going to require any kind of top speed on this track, so I might as well focus on all out acceleration.
I'm running a 6.5t LRP K7 motor, but I'm also running the highest possible gear ratio for my buggy, 87t spur and 19t pinion. I tried fitting 18t, but the mesh was ultra sketchy on the loose side.
So I'm now accelerating as fast as theoretically possible, but I would like to accelerate even faster.

What do I do now to accelerate even faster? I know higher turn motors produce more torque, so should I step down to say a 7.5t or 8.5t or even 9.5t, while maintaining the same gear ratio? Will that be faster or slower acceleration wise?
Or do I go to 5.5t to punch even harder? Having tried the 5.5 before, I don't like the soft bottom end on it, has a distinct lack of punch. It was mega quick up top though, but produced ridiculous temperatures in the space of a few mins.
I do not have a bigger spur, neither do I know of one that can fit my car.(YZ4)
Bear in mind I tend to go for longer practice runs, not short 5 min heats, hence I can't be having a motor overheat on me after 5min and 5 secs. I don't like to gear my motor like that.
I have completely dialled out any form of esc and motor timing, seeing that they only serve to increase top speed. Motor has a fixed endbell anyway...
Sir 51D3WAYS is offline  
Reply With Quote
Old 07-12-2019, 02:21 PM
  #2  
Tech Adept
 
Join Date: Jan 2018
Posts: 236
Default

Not seeming to add up. I'm not an expert.

- Lower the motors turn, the more power or amps the motor runs at. Yep, you gear them down, as there power is at higher RPM's.
- Higher turn motors produce more torque? No way. I've raced a 21 turn, and it was a turd. I believe Torque is more of Gearing, and less of turns.
- I gear my motors down, till I can use their top speed, on the longest strait at the race track. That way I have the most Torque, at the appropriate max Speed.
- 6.5t LRP? I would say get a real motor? Maclan V2, Reedy, Wurks v21, exec. OK, maybe I just don't know LRP.
- Your running a 6.5 on a little track, and don't have enough power? Something must be wrong?

Fix is simple, run a Tekno eb410, then get a 32t Spur (from a et410). Run a 4 pole 540, 4600 Tekin motor in. Or even a 550, 4300 Tekin? Maclan 4100? Bet you have enough power.

4 pole motors are better at not overheating for the amount of power they put out.

Talking about wanting more power racing, and wanting long practice runs, sounds a bit counter productive.

Fixed endbell on a 6.5 Mod motor? Sounds like you need a modern Motor?

My Maclan 7.5 turn, in a 4 wheel drive Truggy (et410), is more power than I can put down on our small/medium size indoor clay track. Not having enough power from a 6.5 in a 4wd buggy, small track, does not seem to add up?

This is not even talking about turning up the punch in the Speed control.
sea1swk is offline  
Reply With Quote
Old 07-12-2019, 10:23 PM
  #3  
Tech Master
Thread Starter
 
Sir 51D3WAYS's Avatar
 
Join Date: Jun 2011
Location: Somewhere in this Universe
Posts: 1,525
Default

Errrr... not quite. The power is there, but there is too much top speed instead of acceleration. I need more acceleration, but I'm running the smallest possible pinion that can fit. I CANNOT gear down anymore.
I literally have only a 30 foot straight, maybe 40 foot straight if they change the track layout?

Do I go with a higher or lower turn motor?
or confabulate my own spur gear?

I suppose I could mess with ESC punch....

Changing timing is pointless as it increases top speed.... Which I don't need.


Stop tempting me with your bloody tekno.... I like 1/10th truggys too much.... Besides, tekin and tekno have poor availability in my country....

Last edited by Sir 51D3WAYS; 07-12-2019 at 10:35 PM.
Sir 51D3WAYS is offline  
Reply With Quote
Old 07-14-2019, 06:45 AM
  #4  
Tech Apprentice
 
Join Date: Dec 2017
Posts: 74
Default

You should run a fan since you're running your whole pack out. I try to stay at 130-140 for longevity but 150 at the end of a run is ok.

And timing can absolutely add low and mid range punch/acceleration. Timing actually wont increase your top speed, if you are hitting the motors RPM max. If you aren't hitting that point the extra timing will make more power to get it to that point though.

Brushless motors are weird sometimes gearing them up (larger pinion/smaller spur) can make more mid range acceleration as it forces the motor to use more amps to push the car. If the esc and battery can provide it, it can actually be faster. Also if you're under geared and the motor is over revving it may run hotter than if it was geared where the motor wants to be.
Sir 51D3WAYS likes this.
Alexv2024 is offline  
Reply With Quote
Old 07-14-2019, 09:21 AM
  #5  
Tech Master
Thread Starter
 
Sir 51D3WAYS's Avatar
 
Join Date: Jun 2011
Location: Somewhere in this Universe
Posts: 1,525
Default

^Thanks for the reply. I have a fan on the esc, but not the motor as there is no space for one. My motor is under the top deck, and sandwiched between the servo and layshaft. I have toyed with the idea of esc timing. Should I use a fixed amount or use the turbo function, which varies the timing throughout the range? I have tried using a larger pinion, but the temperature was through the roof after 5 mins... I've looked at setup sheets from the pros and they also run a similar sort of gear ratio i.e. 19t/20t/21t pinion and even more powerful motors like 5.0t and 5.5t. 5.5t was terrifying, I regret buying it in the first place....
Sir 51D3WAYS is offline  
Reply With Quote
Old 07-14-2019, 07:12 PM
  #6  
Tech Apprentice
 
Join Date: Dec 2017
Posts: 74
Default




That was the first result in google for yz4 fan mount. So I don't know what the problem is there's plenty of room. Heck my B6.1 is harder to mount a fan.

As far as timing goes I haven't messed with it as I've mainly been running stock classes. I would just copy a pros boost and turbo settings and see how you like each and tweak from there. I'm sure there are some guides out there on how to start off with I just haven't looked for any.
Sir 51D3WAYS likes this.
Alexv2024 is offline  
Reply With Quote
Old 07-14-2019, 09:07 PM
  #7  
Tech Master
Thread Starter
 
Sir 51D3WAYS's Avatar
 
Join Date: Jun 2011
Location: Somewhere in this Universe
Posts: 1,525
Default

Errrr...... That's a very odd placement But thanks for the tip.... I'll have to jury rig something.
Sir 51D3WAYS is offline  
Reply With Quote
Old 07-15-2019, 12:05 AM
  #8  
Tech Apprentice
 
Join Date: Jun 2019
Posts: 51
Default

First run of this truck I put in front lawn grass area basiclLy just did circle after circle and donuts in the low cut grass with the car setup for carpet . Anyways. 78/25 13.5 t revtech ,. Tekin RS gen2 it got so hot I believe it shut off as I got no signal and I had th top off do I heard speed control make some beeps but naturally didn't hear any of it .

It was like 108-110 outside so very hot but seems something more Is the cause to over heat. I would really appreciate any advice on this before it happens a second time. Since this occurrence my hotwire came in the mail and I switched its Bec voltage to 7.4 instead of 6 to accommodate servo power . (1258tg)
vegas7o2 is offline  
Reply With Quote
Old 07-15-2019, 12:44 AM
  #9  
Tech Master
 
the rc guy's Avatar
 
Join Date: Aug 2016
Location: Detroit
Posts: 1,403
Default

can you modify motor mount to make your pinion18 or even 17. that was loose mesh tighter?. like Dremel slots .will motor hit anything if you do?.
the rc guy is online now  
Reply With Quote
Old 07-15-2019, 02:23 PM
  #10  
Tech Master
Thread Starter
 
Sir 51D3WAYS's Avatar
 
Join Date: Jun 2011
Location: Somewhere in this Universe
Posts: 1,525
Default

Originally Posted by vegas7o2 View Post
First run of this truck I put in front lawn grass area basiclLy just did circle after circle and donuts in the low cut grass with the car setup for carpet . Anyways. 78/25 13.5 t revtech ,. Tekin RS gen2 it got so hot I believe it shut off as I got no signal and I had th top off do I heard speed control make some beeps but naturally didn't hear any of it .

It was like 108-110 outside so very hot but seems something more Is the cause to over heat. I would really appreciate any advice on this before it happens a second time. Since this occurrence my hotwire came in the mail and I switched its Bec voltage to 7.4 instead of 6 to accommodate servo power . (1258tg)
This buggy naturally has a high amount of driveline drag. Plus grass is a high friction surface, so your temps are naturally going to go through the roof. Suggest you go back to the 87 tooth spur....
Sir 51D3WAYS is offline  
Reply With Quote
Old 07-15-2019, 02:25 PM
  #11  
Tech Master
Thread Starter
 
Sir 51D3WAYS's Avatar
 
Join Date: Jun 2011
Location: Somewhere in this Universe
Posts: 1,525
Default

Originally Posted by the rc guy View Post
can you modify motor mount to make your pinion18 or even 17. that was loose mesh tighter?. like Dremel slots .will motor hit anything if you do?.
Maybe, but I'm reluctant. There is very little material left at the end of the motor mounting screw slot. Plus the mount itself is naturally weak...

Motor won't hit anything.
Sir 51D3WAYS is offline  
Reply With Quote
Old 07-18-2019, 01:19 PM
  #12  
Tech Apprentice
 
Join Date: Jun 2019
Posts: 51
Default

i couldnt fit a 81t spur with a 25t pinion? if i got a higher tooth spur would i need a higher or lower t pinion?

ill keep that in mind. i had a feeling that the grass surface was the main issue as its geared for carpet and running it opposite almost just doing donuts almost in a tiny tiny grass area
vegas7o2 is offline  
Reply With Quote
Old 07-18-2019, 03:12 PM
  #13  
Tech Regular
 
Join Date: Nov 2016
Posts: 280
Default

My 2 cents for mod motor tuning.(if you put an adjustable timing motor back in)

Start with the recommended gearing and set your motor timing very low. This keeps the amp draw to the minimum throughout the rpm range and will drop max rpm to a stock motor speed. The esc timing is useful to adjust where in the rpm range you need more power/use more battery. You want to see maximum rpm being reached on the straight. Focus on the infield driveability as well, you want to be able to drive it 100% in control with low can timing. It may feel kind of slow depending on your motor turn but don't worry for now.

Use your gearing and punch settings as your 1st gear when accelerating and to control the overall feel of the buggy.

Boost timing is your 2nd gear. Use it to increase your low-mid rpm torque. It's very useful for clearing jumps and accelerating hard out of corners.

Turbo is your 3rd gear for top end acceleration for the straight and/or a big feature on the infield depending on the activation setting. Using the full throttle+rpm setting you can adjust where the turbo kicks in on the straight. The delay and increase rate can be useful depending on your grip level/motor strength.

The difference between turns is slightly more power throughout the entire rpm range and more rpm. So for instance on a lot of setup sheets with a 5.5t you might only see 5° of turbo in conjunction with low can timing, because a 5.5t has so much power. With a 6.5t to get the same power throughout the same rpm you may need 5°boost and 10°turbo and more for a 7.5t ect ect.

With your current setup you could try turning your throttle end point down to limit top speed and add boost to increase acceleration.
hyperfuxx and Sir 51D3WAYS like this.

Last edited by trf211; Yesterday at 07:03 PM.
trf211 is offline  
Reply With Quote
Old Yesterday, 12:50 AM
  #14  
Tech Master
Thread Starter
 
Sir 51D3WAYS's Avatar
 
Join Date: Jun 2011
Location: Somewhere in this Universe
Posts: 1,525
Default

Originally Posted by vegas7o2 View Post
i couldnt fit a 81t spur with a 25t pinion? if i got a higher tooth spur would i need a higher or lower t pinion?

ill keep that in mind. i had a feeling that the grass surface was the main issue as its geared for carpet and running it opposite almost just doing donuts almost in a tiny tiny grass area
Use the same pinion for now. Just go back to the original 87t spur.
Sir 51D3WAYS is offline  
Reply With Quote

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service