R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Electric On-Road

Reply
 
Thread Tools Search this Thread
Old 12-07-2007, 09:33 PM   #1
Tech Regular
 
RandomFellow's Avatar
 
Join Date: May 2005
Location: Plymouth, MI
Posts: 311
Trader Rating: 3 (100%+)
Default Big or Small Spur Gear???

OK, I've spent the evening searching through the forums for the answer to this question: is it better to have the largest spur gear or the smallest spur gear your chassis can handle? Mostly, people have stated that while you can obtain the same FDR, the smaller spur has less rotating mass, so that is why the use the smallest. IDK, it sounds kinda nonsense to me, but I'm not entirely dissuaded. Does anyone have an opinion on this issue?
RandomFellow is offline   Reply With Quote
Old 12-07-2007, 09:42 PM   #2
Tech Elite
 
chris moore's Avatar
 
Join Date: Mar 2004
Location: Phx AZ
Posts: 3,780
Trader Rating: 88 (99%+)
Default

Sometimes yes and sometimes no As a general rule you get more speed(top end) with a smaller spur/larger pinion. The key is to match your track layout(overall size and longest straight) to acheive the best overall balance of acceleration and speed.
chris moore is offline   Reply With Quote
Old 12-07-2007, 09:51 PM   #3
Tech Master
 
Centerline Racing's Avatar
 
Join Date: Nov 2006
Location: Twin Cities, MN
Posts: 1,077
Trader Rating: 33 (100%+)
Default

In my case, S400, it has to do with the range of pinions that I currently have. I'd like to keep my base point in the middle of them so I can go up or down depending on the track size I am racing on; 36x58 vs 48x100. Makes it easer to just change pinions to test straitaway speed vs infield response.

Currently it's 88s and 41p for the larger track.

IMO
Allan
Centerline Racing is offline   Reply With Quote
Old 12-07-2007, 09:53 PM   #4
Tech Master
 
Centerline Racing's Avatar
 
Join Date: Nov 2006
Location: Twin Cities, MN
Posts: 1,077
Trader Rating: 33 (100%+)
Default

Also, unless you're trying to gain 1/10 of a second per lap at a Nat Race, it doesn't matter. I personally can gain or lose 3/10 of a second just by hitting or missing one apex. It's all about balance.
Centerline Racing is offline   Reply With Quote
Old 12-07-2007, 09:54 PM   #5
Tech Champion
 
Still Bill's Avatar
 
Join Date: Jan 2004
Location: Reno, NV
Posts: 7,237
Trader Rating: 12 (100%+)
Default

Using combinations of smaller or larger pinion/spurs will move the weight of the motor fore and aft in a typical belt-driven chassis. This changes your car's front/rear weight distribution which can be used to your advantage. Larger gears move the motor forward; and, smaller gears move in back.

Cheers!
__________________
Constantly evolving CRC WGT and WGT-R/T...Carpet & Asphalt...All thanks to Team CRC.

And a pair of Associated B6 buggies for turf and clay tracks.
Still Bill is offline   Reply With Quote
Old 12-07-2007, 10:04 PM   #6
Tech Adept
 
Join Date: May 2005
Posts: 241
Default

Good question, and I suspect you'll get some good answers. After 15+ years of high level 1/12, 1/10 and touring car racing with my son, my opinion is that it doesn't matter very much at all. One theory is that more tooth engagement (i.e. bigger spur and pinion) is more efficient due to smoother transition from tooth to tooth, and you have stated the other theory. Until someone does a definitive test showing a significant difference between the two, I will continue to be of the opinion that there is just not enough difference (if any) to matter.
Larry Brown is offline   Reply With Quote
Old 12-07-2007, 10:07 PM   #7
Tech Initiate
 
Join Date: Nov 2007
Location: Dayton Ohio
Posts: 32
Default

Well,this is a touchy subject for some,and you will get diffeent answers.But here is mine.I have done this on a TC4 and a TC5.Don't know if you have ever seen the factory spur with the TC5 but it is a 87t 48 pitch,a monster! I put a 88t 64 pitch and can run 45 to a 52 pinion.Carpet or asphalt the car flys.Then you also have to consider brushed or brushless.Brushless can be geared way different,they have a ton of torque.Torque moves mass,horsepower keeps it moving.I really don't even use roll-out anylonger.I gear by temp. and lap times.Just like a real car when doing a diff.How many times does the pinion turn to one rotation of the ring gear(spur). If your spur turns once and the pinion turns two times,thats better than a larger gear that turns one and a half turns.(example)Again for brushless,Torque!!!! It works try it.Some at our track said that won't work....they orderd new gears the next day......lol Mark your gears and turn them,check the revolutions.Take anything with pulleys/gears one small (power) one big,big turns slower.Now remove big one replace with smaller one it spins faster.
My 2 cents....
__________________
TC5-TC4-KSG-Tekin-Novak-3PK-Hitec-PRS-Gears-John's BSR-Racing-Tires Tri-State Raceway In Hamilton ,Ohio-Much More-Spektrum Associated-Team Magic-APS-SMC Competition Electronics-Ice.
8up-Club Dayton,Ohio
108% Certified 8up
8up-racing is offline   Reply With Quote
Old 12-07-2007, 10:10 PM   #8
Tech Master
 
Join Date: Aug 2005
Location: Michigan
Posts: 1,049
Default

I've understood that with a larger spur you actually get more leverage which equates to more torque. Can't give a definitive answer one way or the other though!
John Warner is offline   Reply With Quote
Old 12-07-2007, 10:15 PM   #9
Tech Champion
 
skypilot's Avatar
 
Join Date: Mar 2007
Posts: 9,524
Trader Rating: 14 (100%+)
Default

i believe your question is, for example, if i can get a 7.0 gear ratio which is perferred, 118/32 or 100/40, (those are just random numbers.) i believe it does make a difference in motor performance, but which is better i can not say, it depends on the track layout and which motor you are using. on my home track i perfer the feel of 96 spur, on the away track i'm running this weekend end i went with a 118, (actually 89 48 pitch, same size as 118 but can only match gear ratios with the 89) most of all, it depends on which one you think feels better to you and your driving style.
skypilot is offline   Reply With Quote
Old 12-07-2007, 10:31 PM   #10
Tech Elite
 
Grenade10's Avatar
 
Join Date: Nov 2003
Location: Fort Collins, Colorado
Posts: 4,674
Trader Rating: 37 (100%+)
Default

My 2 cents ..... A larger spur will give you more adjustment (finer adjustment) Also in stock it will give you a little more leverage on the spur. With a 19 turn, modified or brushless motor which has more torque, it is not as important.
__________________
Darkside, Sweep, BSR, Fantom, IGT Hobbies and IGT8
Byrons Fuel, ProtoForm Bodies & Futaba Radio Gear by Choice
Founding Member of CORRC .... 5280raceway
www.darksidems.com www.igthobbies.com www.IGT8.com
Grenade10 is offline   Reply With Quote
Old 12-08-2007, 03:23 PM   #11
Tech Regular
 
RandomFellow's Avatar
 
Join Date: May 2005
Location: Plymouth, MI
Posts: 311
Trader Rating: 3 (100%+)
Default

WOW! Thanks for all of the replies. Right now, I'm trying to figure out the the best spur/pinion combo for my TA-05 with a 13.5SS. Getting down to 4.5-5.0 FDR provides for a couple options: small spur with ginormous pinion, or larger spur with slightly less than ginormous pinion.

The only thing I can think of as being that much of a difference is the rotation of the motor compared with the drivetrain. Smaller spur with biffer pinon makes the motor rotate less than using a smaller pinion/larger spur combo. So, I think the biggest issue is motor rpm, and where in the rpm curve the motor feels most comfortable with.

I wondering that if brushless motors have all of this torque, that they might enjoy the lower rpm band more, whereas a brushed motor might want to have some higher rpms to keep the motor spooled up.

Man, this may be the most boring topic on here, but for some reason I am really intrigued by this issue.

Last edited by RandomFellow; 12-08-2007 at 03:53 PM.
RandomFellow is offline   Reply With Quote
Old 12-08-2007, 07:38 PM   #12
Tech Adept
 
Headshot's Avatar
 
Join Date: May 2007
Location: South Florida
Posts: 131
Trader Rating: 1 (100%+)
Send a message via Yahoo to Headshot
Default

ok, I realize I am relatively new to R/C, and I was following this thread perfectly....but when you start using highly technical terms like ginormous, I am lost.....
__________________
Frank

"Some People are like a Slinky- basically useless, but still bring a smile to your face when you push them down a flight of stairs"
Headshot is offline   Reply With Quote
Old 12-08-2007, 07:49 PM   #13
Tech Addict
 
surrealmaterial's Avatar
 
Join Date: Aug 2006
Location: NSW, Australia
Posts: 651
Trader Rating: 4 (100%+)
Send a message via MSN to surrealmaterial
Default

Quote:
Originally Posted by RandomFellow View Post
small spur with ginormous pinion, or larger spur with slightly less than ginormous pinion.
you got it the wrong way around, it should be with a smaller spur you will need a small pinion and with a larger spur you will need a larger pinion.

Cheers
__________________
Castle Hill Raceway
surrealmaterial is offline   Reply With Quote
Old 12-08-2007, 08:37 PM   #14
Tech Regular
 
RandomFellow's Avatar
 
Join Date: May 2005
Location: Plymouth, MI
Posts: 311
Trader Rating: 3 (100%+)
Default

Quote:
Originally Posted by surrealmaterial View Post
you got it the wrong way around, it should be with a smaller spur you will need a small pinion and with a larger spur you will need a larger pinion.

Cheers
Yeah, what Surreal said! BUT, the size of the pinion doesn't increase as fast as the size of the spur. For example, a 68 tooth spur and a 17 tooth pinion = 4.0, whereas a 76 tooth spur and a 19 tooth pinion also equals 4.0. That's an 8 tooth difference on the spur, but only a 2 tooth difference on the pinion. So, as spur sizes increase, the rate of increase is greater than the pinion, thereby resulting in a smaller pinion in comparison to the spur. It's all relative.
RandomFellow is offline   Reply With Quote
Old 12-09-2007, 11:14 AM   #15
Tech Addict
 
kcrunchone's Avatar
 
Join Date: Oct 2005
Location: WWW.MAXAMPS.COM
Posts: 527
Trader Rating: 1 (100%+)
Default

Guys dont you think that roll out would play a major part in the decision on the gears ? Also the determination of what works best for your size track and to determine what gears also fit your driving style.

If you apply a lot of torque and spin the wheels that accomplishes just about nothing because the guy that is rolling smoother and apply torque to the ground is making laps while your are just spinning tires.

I am not going to dispute that different things work for different tracks, but trial and error is a major factor in any decisions that should be made. 2nd season for me on the carpet and I am still playing with ratios.
__________________
Rick Hill

"Failure Is Not An Option"
kcrunchone is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
Jammin CRT/BCE Small gear conversion Bob Moore R/C Items: For Sale/Trade 19 03-25-2008 07:58 PM
Gear Ratios/ Spur Gear Sparky7B Rookie Zone 2 02-26-2008 10:03 PM
Jammin Diff, w/ Lightened Spur And Extra Spur Gear prphze R/C Items: For Sale/Trade 0 10-07-2007 03:40 PM
small spur gears pinggoy Electric On-Road 7 07-07-2006 05:19 PM
Big Pinion / Small Spur - OR- Small Pinion / Big Spur -- Difference? rctoyguy Electric On-Road 7 07-12-2004 05:54 PM



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

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



All times are GMT -7. It is currently 06:35 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net