R/C Tech Forums

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

Reply
 
Thread Tools Search this Thread
Old 01-03-2009, 12:22 PM   #1
Tech Apprentice
 
RielTime Racing's Avatar
 
Join Date: Oct 2008
Location: Fort Collins
Posts: 72
Lightbulb Gear Box Ratio's

Does anyone here change their gearbox ratio for particular tracks or racing conditions? (Not to be confused with Spur/Pinion Gear Ratio or Final Drive Ratio). If so, what gearbox ratio have you settled on most of the time and why? I've figured I can change mine pretty much anywhere between 2.25-1.88. What seems to be most efficient for you? I know there are tons of factors to consider but I thought it would be an interesting, fun topic to discuss.

Currently running 107/36 Spur/Pinion, 2.0 gearbox with FDR of 5.94
RielTime Racing is offline   Reply With Quote
Old 01-03-2009, 07:57 PM   #2
Tech Elite
 
a_main_attendee's Avatar
 
Join Date: Jan 2008
Location: Colorado, USA, The land of the free and the home of the brave!
Posts: 2,880
Trader Rating: 2 (100%+)
Default

I wouldn't think it would be an efficiency issue but instead an issue that deals with getting an appropriate FDR for higher turn brushless motors.

I've never changed nor would consider changing my vehicle's internal drive ratio.
__________________
Support your local tracks!--|--e-teamhobbyplex.com--|--corrc.org--|

NNFaN Paints - Add some pride to YOUR ride.
a_main_attendee is offline   Reply With Quote
Old 01-03-2009, 10:25 PM   #3
Tech Apprentice
 
RielTime Racing's Avatar
 
Join Date: Oct 2008
Location: Fort Collins
Posts: 72
Default

If you compared a gearbox 36/18 to 34/17 the ratio would be the same, 2.0. Depending on a given course one combo has to have an advantage over the other.
RielTime Racing is offline   Reply With Quote
Old 01-03-2009, 10:50 PM   #4
Tech Elite
 
a_main_attendee's Avatar
 
Join Date: Jan 2008
Location: Colorado, USA, The land of the free and the home of the brave!
Posts: 2,880
Trader Rating: 2 (100%+)
Default

Quote:
Originally Posted by RielTime Racing View Post
If you compared a gearbox 36/18 to 34/17 the ratio would be the same, 2.0. Depending on a given course one combo has to have an advantage over the other.

Why should there be an advantage?
__________________
Support your local tracks!--|--e-teamhobbyplex.com--|--corrc.org--|

NNFaN Paints - Add some pride to YOUR ride.
a_main_attendee is offline   Reply With Quote
Old 01-03-2009, 10:56 PM   #5
Tech Apprentice
 
RielTime Racing's Avatar
 
Join Date: Oct 2008
Location: Fort Collins
Posts: 72
Default

I would think that one ratio would be more efficient on the motor, or better on acceleration, or holding speed for certain parts of the course.
RielTime Racing is offline   Reply With Quote
Old 01-04-2009, 01:39 AM   #6
Tech Addict
 
Superkarter's Avatar
 
Join Date: Aug 2005
Location: Scarborough Australia
Posts: 630
Trader Rating: 2 (100%+)
Default

In theory the bigger pulleys will give a slight increase in efficiency due to less belt wrap.

How much of a difference not really sure, probably not enough to notice.
Superkarter is offline   Reply With Quote
Old 01-04-2009, 03:45 AM   #7
Tech Elite
 
Trips's Avatar
 
Join Date: Aug 2001
Location: 360 Speedway
Posts: 2,251
Trader Rating: 16 (100%+)
Default

Quote:
Originally Posted by RielTime Racing View Post
If you compared a gearbox 36/18 to 34/17 the ratio would be the same, 2.0. Depending on a given course one combo has to have an advantage over the other.
The 2.0 ratio would have a clear and noticeable advantage.
__________________
MARSHAL!!
Trips is offline   Reply With Quote
Old 01-04-2009, 06:09 PM   #8
Tech Adept
 
jbmx4life's Avatar
 
Join Date: Feb 2008
Location: Green Bay, WI
Posts: 137
Trader Rating: 2 (100%+)
Send a message via AIM to jbmx4life Send a message via MSN to jbmx4life Send a message via Yahoo to jbmx4life
Default

Quote:
Originally Posted by Trips View Post
The 2.0 ratio would have a clear and noticeable advantage.


I think that you misunderstood.... both examples he gave were a 2.0 ratio, he was just asking which one would be more beneficial for particular applications.
jbmx4life is offline   Reply With Quote
Old 01-04-2009, 06:47 PM   #9
Tech Apprentice
 
RielTime Racing's Avatar
 
Join Date: Oct 2008
Location: Fort Collins
Posts: 72
Default

Quote:
Originally Posted by jbmx4life View Post


I think that you misunderstood.... both examples he gave were a 2.0 ratio, he was just asking which one would be more beneficial for particular applications.
Yes, and if you compared Tamiya, Xray, Associated ... they all use different Gearbox/Internal drive ratios.
RielTime Racing is offline   Reply With Quote
Old 01-05-2009, 12:17 AM   #10
Tech Elite
 
Trips's Avatar
 
Join Date: Aug 2001
Location: 360 Speedway
Posts: 2,251
Trader Rating: 16 (100%+)
Default

Quote:
Originally Posted by jbmx4life View Post


I think that you misunderstood.... both examples he gave were a 2.0 ratio, he was just asking which one would be more beneficial for particular applications.
I understood completely. He said an 18/36 set of pulleys and a 17/34 set of pulleys both have a 2:1 ratio, but one would have to have an advantage over the other.

I responded that I thought the 2:1 ratio would be the better of the two.
__________________
MARSHAL!!
Trips is offline   Reply With Quote
Old 01-05-2009, 08:11 AM   #11
Tech Adept
 
jbmx4life's Avatar
 
Join Date: Feb 2008
Location: Green Bay, WI
Posts: 137
Trader Rating: 2 (100%+)
Send a message via AIM to jbmx4life Send a message via MSN to jbmx4life Send a message via Yahoo to jbmx4life
Default

Quote:
Originally Posted by Trips View Post
I understood completely. He said an 18/36 set of pulleys and a 17/34 set of pulleys both have a 2:1 ratio, but one would have to have an advantage over the other.

I responded that I thought the 2:1 ratio would be the better of the two.
jbmx4life is offline   Reply With Quote
Old 01-05-2009, 09:14 AM   #12
Tech Elite
 
Trips's Avatar
 
Join Date: Aug 2001
Location: 360 Speedway
Posts: 2,251
Trader Rating: 16 (100%+)
Default

Quote:
Originally Posted by jbmx4life View Post
All kidding aside now, some might say the 18/36 set of pulleys might have a slight efficiency advantage over the 17/34 due to the belts making bigger radius turns, but there might be a loss of efficiency with the bigger pulleys due to increased friction having more belt teeth engaged than with the smaller set. I have no idea which would work better.

If we're comparing different ratios in the same car, then there are situations where one might prove better. I can think of two cases off the top of my head... You might find that you can't achieve the final ratio you want given pinion/spur availability unless you use a certain transmission ratio, in which case the choice is made for you. In other cases, you might be able to get to your ideal final ratio with either of several pulley ratios, but depending on pulley ratio you might find a spur piniono combo that moves the motor slightly forward or rearward in the car to optimize front/rear weight bias without having to add ballast to the car.

I've never actually gone so far as to change pulley ratio in a TC to tune weight bias, but I suspect some might go that far. I will say that I HAVE at times changed spur/pinion combos in a pan car to keep the same gear ratio, but move the motor further or closer to the rear axle.
__________________
MARSHAL!!
Trips is offline   Reply With Quote
Old 01-05-2009, 12:28 PM   #13
Tech Apprentice
 
RielTime Racing's Avatar
 
Join Date: Oct 2008
Location: Fort Collins
Posts: 72
Default

Quote:
Originally Posted by Trips View Post
All kidding aside now, some might say the 18/36 set of pulleys might have a slight efficiency advantage over the 17/34 due to the belts making bigger radius turns, but there might be a loss of efficiency with the bigger pulleys due to increased friction having more belt teeth engaged than with the smaller set. I have no idea which would work better.

If we're comparing different ratios in the same car, then there are situations where one might prove better. I can think of two cases off the top of my head... You might find that you can't achieve the final ratio you want given pinion/spur availability unless you use a certain transmission ratio, in which case the choice is made for you. In other cases, you might be able to get to your ideal final ratio with either of several pulley ratios, but depending on pulley ratio you might find a spur piniono combo that moves the motor slightly forward or rearward in the car to optimize front/rear weight bias without having to add ballast to the car.

I've never actually gone so far as to change pulley ratio in a TC to tune weight bias, but I suspect some might go that far. I will say that I HAVE at times changed spur/pinion combos in a pan car to keep the same gear ratio, but move the motor further or closer to the rear axle.
Wow! That's awesome. Never thought of changing pulley ratio to effect the positioning of where the motor mounts for weight ditribution too. Highly doubt I'd go that far. Keep the posts coming!

Yeah, I'd think smaller pulley would be and advantage for tight, twisty tracks or a need for quik accelerations and the larger pulley for long high speed flow tracks.
RielTime Racing is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
Hpi Pro 4 Barry White Electric On-Road 16060 Yesterday 02:19 AM
Formula 1... Darkseid Chat Lounge 15115 11-01-2017 10:52 AM
Kyosho Ultima RB5 Thread Drift_Buggy Electric Off-Road 14641 11-10-2015 09:28 AM
Losi XXX-S TSR6 Electric On-Road 14329 01-26-2015 08:59 PM
TRAXXAS REVO WITH BUMP BOX AND EXTRAS Jaypeezy R/C Items: For Sale/Trade 6 04-21-2009 05:16 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 11:43 PM.


Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net