R/C Tech Forums

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

Reply
 
Thread Tools Search this Thread
Old 10-12-2004, 07:56 AM   #1
Tech Rookie
 
Join Date: May 2004
Location: malaysia
Posts: 8
Talking how to calculate rollout

hi guys

Can anyone please help me on calculating roll out.

Thank you
Newbies is offline   Reply With Quote
Old 10-12-2004, 08:00 AM   #2
Tech Elite
 
JDXray's Avatar
 
Join Date: Mar 2004
Location: Long Island, New York
Posts: 2,802
Trader Rating: 3 (100%+)
Send a message via AIM to JDXray
Default

i needed help on this one too. But this is what i got outta the forums.


RBLove wrote on Today 04:52 PM:
Yeah No problem.

19turn actually take a bigger gear than stock. Tire size has everything to do with it. I assume this person is running on carpet?

Tire size x pie (3.14) = ______
Spur / pinion x internal gear ratio = ______

Divide the top number over the bottom and you have roll out. Do not flip these two when dividing..

Example: X-Ray FK with 2.25 in tires ( I do not use mm).

2.25 x 3.14 = 7.06
132sp / 35pin x 1.77 internal = 6.67

7.06 / 6.67 = 1.058 roll out

Depending on track size, but like Cleveland or Snowbords a monster stock would be geared around a 1.00 or little lower. 19t would be at a 1.12 or even higher.

Hope this helps......
Rob
JDXray is offline   Reply With Quote
Old 10-12-2004, 09:14 AM   #3
Tech Regular
 
Join Date: Mar 2004
Location: Omaha, NE
Posts: 238
Send a message via AIM to galway
Default

Another way of crunching the numbers is:

(Tire size * pinion * pi) / (spur * internal ratio)

This requires division only once. It is also easy to pull out part of the formula and call it a constant to remove all need for division at the track.

(pinion * tire size) * (pi/(spur*internal ratio))

pinion and tire size are the only 2 things likeley to change so you can pre-calculate the right half.

Using the example numbers above you would just do

pinion * tire size * .0134

The easiest though is to just make a table, but real geeks do it by hand.
galway is offline   Reply With Quote
Old 10-12-2004, 09:20 AM   #4
Tech Fanatic
 
Chill Will's Avatar
 
Join Date: Oct 2003
Location: The Dirty South
Posts: 804
Default

www.gearchart.com

Click on gearchart creator. It has a section for rollout
Chill Will is offline   Reply With Quote
Old 10-12-2004, 09:31 AM   #5
Tech Addict
 
StewartFan20's Avatar
 
Join Date: Mar 2004
Location: Grrrrr!!!!
Posts: 693
Trader Rating: 4 (100%+)
Default rollout

The question I have is....How do you know what the rollout should be for a particular track?
__________________
Devil Dog Racing | HobbyTown USA (Kansas City,North) | Fastlane Raceway | Matrix Tires

Someday, I hope to be the man my dog thinks I am.
StewartFan20 is offline   Reply With Quote
Old 10-12-2004, 11:51 AM   #6
PaZ
Tech Master
 
PaZ's Avatar
 
Join Date: Oct 2004
Location: Cornwall (England)
Posts: 1,262
Default roll out

The best site i have ever used and found for roll outs is http://www.arroyoc.com/index.cfm?fus...utilities.gear you can print them out and take them to the track with you so you will always be able to check, like me
PaZ is offline   Reply With Quote
Old 10-12-2004, 01:43 PM   #7
Tech Regular
 
Join Date: Mar 2004
Location: Omaha, NE
Posts: 238
Send a message via AIM to galway
Default

you don't really know what is the best rollout until you get your car out on the track. Rollout is jjust a useful measurement for holding a setup or trying to copy someone elses. So the best way to find out a good rollout is to ask someone good at the track what they are running.
galway is offline   Reply With Quote
Old 10-12-2004, 02:20 PM   #8
Tech Regular
 
johnnywhopper's Avatar
 
Join Date: Apr 2003
Location: Rome, NY
Posts: 371
Default

if you're figuring rollout for a pan car, there's no internal ratio needed, it's simply:

pinion x tire size x 3.14 / spur = rollout


if someone has given you a good rollout and you want to figure out what pinion to use, just figure it backwards:

rollout x spur / 3.14 / tire = pinion


jw
__________________
Team CRC, Spektrum, Hobbywing, JDJ Vinyl Graphics, Moby Graphix, Black Art, Power Push
johnnywhopper is offline   Reply With Quote
Old 10-12-2004, 03:12 PM   #9
Tech Initiate
 
Join Date: Oct 2004
Location: North West, England
Posts: 43
Default

So heres the roll out of my car ...

(66 x 3.142) (95 24 x 1.81) = 28.96 mm per rev.
neveo is offline   Reply With Quote
Old 10-12-2004, 03:50 PM   #10
Tech Apprentice
 
Join Date: Aug 2004
Location: Windsor, Ontario
Posts: 65
Default

heres a easy one. roll out calculator
jasong is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
How to calculate KVs? boyntoncyclone Electric On-Road 4 08-31-2008 12:46 PM
How do i calculate my stop speed? GunMetal Nitro On-Road 6 06-24-2007 10:05 AM
Calculate Rollout NismoSkyline17 Electric On-Road 9 12-04-2004 10:07 AM
How to calculate drive ratio? Ares17 Singapore R/C Racers 7 01-28-2004 09:03 PM
how do you calculate your top speed?????? 2mcgrath Nitro On-Road 9 10-16-2003 12:32 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 04:39 AM.


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