Go Back  R/C Tech Forums > General Forums > Electric On-Road
Opinion: Bigger Spur or Bigger Pinion Gear >

Opinion: Bigger Spur or Bigger Pinion Gear

Like Tree2Likes

Opinion: Bigger Spur or Bigger Pinion Gear

Old 08-02-2013, 06:42 PM
  #61  
Suspended
iTrader: (6)
 
Join Date: Jun 2011
Location: Brisbane
Posts: 1,696
Trader Rating: 6 (100%+)
Default

Originally Posted by bertrandsv87 View Post
Remember e=mc2....
All this proves is there enough energy contained within the mass of an RC car, that if released, would destroy a small sized city.


Originally Posted by bertrandsv87
In this hobby nothing is negligeable... Every milligram counts. Lighter gears make your Car accelerate and decelerate faster while conserving energy and decrease battery voltage loss throughout the run... It's a chain reaction that can make a big difference...
Perhaps, i think in reality a whole lot of what people do have more or less negligible or even zero influence over the car other than in their minds. Confidence in your gear is important, maybe even as important as good setup.

When you look at Keven Maceys post, someone who did the math and came up with a result of 0.06%, sounds like a lot does it, not really, and in terms of lap times we are talking in the 1000ths of a second. And it is only true if all setup changes effect lap times in a linear way, they do not.

Changes to a car are not linear, they are exponential, hence the law of diminishing returns, and the closer you get to the physical limits of the car, the less effect these changes have on the car.

So, unless you have reached the limits of the standard big ticket items of setup, the things which have the greatest effect on lap time, you have achieved very little, and if you have reached the physical limits of conventional setup, you will gain something that is most likely statistically irrelevant.
RogerDaShrubber is offline  
Old 08-02-2013, 06:54 PM
  #62  
Tech Adept
 
Join Date: Jan 2009
Location: colorado
Posts: 237
Default

the oval guys go for the largest gears you can run. Some have run them on the dyno and claim they can see the difference in amp draw.
Larger gears do reduce the force that tries to separate the gears. Is this big enough to matter, probably not in the range of gears we run now. In the old days, it probably mattered. Think 11 to 15 T 48 P pinions. Now we run 40 to 50 tooth pinions. The bigger difference is how the motor sits in the pod and how it effects the moment of inertia of the pod.
slotracer577 is offline  
Old 07-24-2014, 04:41 PM
  #63  
Tech Adept
iTrader: (2)
 
racegoer711's Avatar
 
Join Date: Apr 2008
Posts: 161
Trader Rating: 2 (100%+)
Default

Originally Posted by Csaari77 View Post
That was not what the original post was asking. He wanted to know if there was an advantage in using different size gear combinations (larger pinion & smaller spur or smaller pinion & larger spur) and maintaining the same FDR. He was trying to determine if the rotaional weight of a pinion gear, or gear mesh, has any effect when choosing what he uses.
Exactly !!!! My thoughts are that with the smaller pinion/larger spur setup the motor will run cooler. I'm not sure about this either but wouldn't the motor rev up quicker because of the pinion being smaller?
racegoer711 is offline  
Old 12-09-2017, 09:55 PM
  #64  
Tech Addict
iTrader: (1)
 
Join Date: Mar 2006
Location: ardmore oklahoma
Posts: 522
Trader Rating: 1 (100%+)
Default

Originally Posted by rangerjkb View Post
Tried this several years ago in Offroad, as the thought generated couriosity...the smaller spur/larger pinion seemed to put more of a strain on the motor and resulted in worse overall performance. Have not since tried it in Onraod....
did i necro a thread? good in this case it needs to be due to something i just noticed on team associateds site.

basically if you look at the various T4 models that have a 2.60:1 tranny you will notice that on the T4.1 it is recommended 11.31:1 FDR ( 20/87), however in the T4.2 and later ( still with a 2.60:1 tranny) they recommend for 8.5t and 9.5t motors a 10.92:1 FDR ( 20/84).

the ONLY difference in the gearing section is the T4.1 generalizes the motor while the T4.2 and T4.3 specify the reedy branded motor. does this make a difference? i seriously doubt motor branding plays a part but i did find it odd. i bought an 84 spur to try the ratio on my old T4( original us made team kit) because with my skyrc cheetah 8.5t the motor is nice at 130f but regardless of slipper setting ( including locking it down) the slipper constantly spins and over heats. i upgraded to vts and that didnt work, i now have the revolution design vented vts and still it gets to hot to touch, i have also added a 4th total pad ( 1 behind spur, 3 in the vts) and still it slips.

now as far as gearing goes i am wondering ( not worried about gear ratio at all here seeing as the main goal is to get as close to a 1:1 rollout as possible with good speed and motor staying cool LOL),is it better to use a smaller spur or a bigger spur .
lordraptor1 is offline  
Old 12-10-2017, 01:17 AM
  #65  
Tech Elite
iTrader: (2)
 
gigaplex's Avatar
 
Join Date: Dec 2015
Location: Melbourne, VIC
Posts: 3,544
Trader Rating: 2 (100%+)
Default

Originally Posted by lordraptor1 View Post
did i necro a thread?
Yes. Can you not see the timestamps on the posts?
Originally Posted by lordraptor1 View Post
the ONLY difference in the gearing section is the T4.1 generalizes the motor while the T4.2 and T4.3 specify the reedy branded motor. does this make a difference?
Yes, it can do.
Originally Posted by lordraptor1 View Post
i seriously doubt motor branding plays a part but i did find it odd.
Different motor designs can have quite different torque/rpm characteristics which needs to be geared differently. Take recommendations with a grain of salt, they're starting points and you need to test and check temps as appropriate.
gigaplex is offline  
Old 12-16-2017, 03:42 PM
  #66  
Tech Master
iTrader: (26)
 
Dane's Avatar
 
Join Date: Feb 2005
Location: Texas Baby
Posts: 1,724
Trader Rating: 26 (100%+)
Default

Dont know if it's been answered but all he is really playing with is the placement of the motor while maintaining same final gearing.
Dane is offline  
Old 01-20-2019, 04:37 AM
  #67  
Tech Initiate
iTrader: (1)
 
Join Date: Sep 2010
Location: Arizona
Posts: 27
Trader Rating: 1 (100%+)
Default

This thread is exactly why I like to run a non-circular pinion/spur combination.

I get the best of everything!

My gear ratio is all over the place, my temps are hot and cool, the amp draw is high and low, the output shaft moment arm is always changing, and I'm speeding up and slowing down whether I like it or not. It throws that 0.06 thing out the window and makes my crappy driving skills irrelevant. Who even cares about rotating mass at this point? It's less stress and I sleep better!

Problem solved.

You guys can thank me later. :-)





glennhl and RCSteveH like this.
Darkstar is offline  
Old 01-20-2019, 06:10 AM
  #68  
Tech Regular
 
Join Date: Oct 2011
Posts: 455
Default doesn't understand the question

Originally Posted by oldrcr View Post
Without getting into the technical differences with friction because of teeth size and moment arms...

S(spur)/P(pinion) = FDR (Final Drive Ratio)


80S/10P = 8.0FDR > high rip, lower top speed, low temp - more rip

80S/20P = 4.0FDR > med. rip, med top speed, med temp
{These two will perform basically identical since FDR is the same}
40S/10P = 4.0FDR > med. rip, med top speed, med temp

40S/20p = 2.0FDR > low rip, higher top speed, high temp - less rip


So,

If FDR is higher, rip is higher, top speed is lower, temps will be lower.

If FDR is the same, performance, rip, temps. are the same.

If FDR is lower, rip is lower, top speed is higher, temps will be higher.


Simple.
Top post is asking same ratio with a small pinion and spur vs large pionion and spur. The above answer missed the point entirely.

Lets say it's 4:1 this guy is shooting for, His question is about 80 spur:20 oinion (=4:1) vs 40 spur: 10 pinion (=4:1), is there a performance advantage?

The answer is yes but very slight. You want the least amount of inertia to overcome at the motor. Having said that we are talking 0.001 second per lap difference here. Just get the spur that fits your range of pinions so you have the gear ratio selection that works for your track. Mine for instance is 4.4:1 to 3.8:1 to cover the layout and track features changes from month to month. Sometimes I need higher on a technical layout, simpler layout (higher speed , less corners) I will move towards 3.8:1. Just install a spur that allows you the range you need.

dman18t is offline  
Old 01-20-2019, 08:43 AM
  #69  
Tech Fanatic
 
Join Date: Jul 2018
Location: Florida
Posts: 989
Default

Originally Posted by dman18t View Post
Top post is asking same ratio with a small pinion and spur vs large pionion and spur. The above answer missed the point entirely.

Lets say it's 4:1 this guy is shooting for, His question is about 80 spur:20 oinion (=4:1) vs 40 spur: 10 pinion (=4:1), is there a performance advantage?

The answer is yes but very slight. You want the least amount of inertia to overcome at the motor. Having said that we are talking 0.001 second per lap difference here. Just get the spur that fits your range of pinions so you have the gear ratio selection that works for your track. Mine for instance is 4.4:1 to 3.8:1 to cover the layout and track features changes from month to month. Sometimes I need higher on a technical layout, simpler layout (higher speed , less corners) I will move towards 3.8:1. Just install a spur that allows you the range you need.
I have to admit I dont have a feel for the relationship between a heavy small gear and a light large diameter gear in RC (yet). Ordinarily the ratio of inertia between the mechanical system and the motor rotor is tied for the primary measurement (alongside torque) for a reciprocating application like ours. it would be the primary diving relationship for the whole application and very small changes make very large differences. I hope that nobody takes that statement as an argument with you its just an I dont know but for selfish reasons I hope you are wrong. Obviously the overall ratio effects inertia but it would be great if the area of a circle could be used as a tuning aid. It squares things in the math world.

But with only 2 variables I would say you understand the only things that would be important to me (granted you said they arent very important).
Bry195 is offline  

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 - Do Not Sell My Personal Information -

Copyright 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.