Go Back   RCCrawler Forums > RCCrawler General Tech > General Crawlers
Loading

Notices

Thread: Need some math help: gearing and wheelspeed

Reply
 
LinkBack Thread Tools Display Modes
Old 12-09-2014, 04:53 AM   #1
I wanna be Dave
 
Join Date: May 2010
Location: The east coast
Posts: 2,598
Default Need some math help: gearing and wheelspeed

there was another thread i had been looking at (Mechanics of a half track with driven front axle) but figured i'd ask the question in a general forum.

so i'm looking to build a transfer case that will allow me to match wheelspeed between a standard wheeled axle and a tracked axle. the setup is front axle is an scx10 axle with underdrive and standard 1.9 tires and the rear axle would be overdrive with rc4wd predator evo tracks.


this is the problem i was trying to work:

if the front as underdrive (43/13) and a 4.1" tire and the rear has overdrive (36/14) with the 2" drive cog does the math work like the following:

tire to drive cog ratio = 2.05
over to under drive ratio = (36/14) / (43/13) = 2.57 / 3.31 = 0.776

total delta = (tire to drive cog ratio) x (over to under drive ratio)
= 2.05 x 0.776
= 1.591

if that is correct I could get something like a 24 / 15 pinion ratio (1.6) or 19 / 12 (1.583).


suggestions or corrections are welcome!
jebster is offline   Reply With Quote
Sponsored Links
Old 12-09-2014, 07:00 AM   #2
RCC Addict
 
Join Date: Jan 2012
Location: Sweden
Posts: 1,809
Default Re: Need some math help: gearing and wheelspeed

Seems you've got the math about right.

I'd just set it up a bit different, going "drive shaft to ground" for each axle.
Front: 13*4.1/43 = 1.24
Rear: 14*2/36 = 0.78

You want these to be closer to each other, though I suspect some overdrive (10-20%) on the front axle is good for tighter turning.

You can simply use smaller front wheels and/or see if there can be more differentiation in the axle gearing.
Olle P is offline   Reply With Quote
Old 12-09-2014, 08:08 AM   #3
I wanna be Dave
 
Join Date: May 2010
Location: The east coast
Posts: 2,598
Default Re: Need some math help: gearing and wheelspeed

Quote:
Originally Posted by Olle P View Post
Seems you've got the math about right.

I'd just set it up a bit different, going "drive shaft to ground" for each axle.
Front: 13*4.1/43 = 1.24
Rear: 14*2/36 = 0.78

You want these to be closer to each other, though I suspect some overdrive (10-20%) on the front axle is good for tighter turning.

You can simply use smaller front wheels and/or see if there can be more differentiation in the axle gearing.

thanks for the input. getting confirmation my math was solid helps.

as far as overdrive on the front axle that works ok if both are running wheels but from my experience with tracks on both axles if there is a front overdrive the rear axle tracks end up getting dragged, causing them to tip up so you don't get flat contact with the ground. that is what i'm going to have to be very close on the "drive shaft to ground" balance via the transfer case. i'm probably going to have to make a transfer case with moveable shafts so i can fine tune the pinion sizes.
jebster is offline   Reply With Quote
Reply



Need some math help: gearing and wheelspeed - Similar Threads
Thread Thread Starter Forum Replies Last Post
Wheelspeed Q Voteban Electronics 5 04-27-2010 03:20 PM
Can you get decent wheelspeed with an r2 HD Hellstomper General Crawlers 2 04-06-2008 09:45 PM
wheelspeed anyone looneybin Chit Chat 1 03-23-2007 07:38 AM
Sometimes you need a little wheelspeed Jeckler Chit Chat 3 04-23-2005 04:06 PM
Thread Tools
Display Modes

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 On
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -6. The time now is 10:00 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO ©2011, Crawlability, Inc.
Copyright 2004-2014 RCCrawler.com