R/C Tech Forums

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

Reply
 
Thread Tools Search this Thread
Old 02-08-2011, 09:24 AM   #1
Tech Adept
 
Join Date: Jan 2011
Posts: 189
Default limited slip setup

just a quick question about my ball diffs. I just installed them and I have set them up fairly tight but also loose enough so that it doesnt need a lot of force to turn the wheels. I did a quick test run with the car and i noticed that the motor can run even though the wheels are not spinning. Obviously i have to push the throttle to get to that point and the motor is 13300kv so there is plenty of power to make them slip.
Is it normal to have some amount of slip or have i configured them wrong?
omegaf is offline   Reply With Quote
Old 02-08-2011, 10:13 AM   #2
Tech Master
 
Join Date: Apr 2008
Location: Christchurch, NZ
Posts: 1,063
Default

You don't want slipping under normal operation. If you can do some acrobatics with your hands, hold one wheel and the spur, then use the other hand to turn the other wheel (front and back done separatly). There should be a lot of resistance, but a small amount of slip.
When you hold the spur and rotate a wheel, the other wheel at the end of the car should rotate easily, without a "gritty" feeling.
__________________
Agama A8 Evo | GRP .21 | Spektrum | Savox

My car just hit 88mph. I hope it comes back soon....
JR007 is offline   Reply With Quote
Old 02-08-2011, 10:55 AM   #3
Tech Adept
 
Join Date: Jan 2011
Posts: 189
Default

yep it works as you said. it doesnt have a gritty feeling. it rolls smoothly however the brushless motor has a bit of a "stepped" rotation so it clicks as it rotates a bit but that is definitely not the diffs.

i just realised after my first run that a 13300kv motor is a bit too much for realistic use. i had the car in my hand and i give it full power and it blew one tyre off the rim. i gotta glue it back now
they were brand new set of wheels too
omegaf is offline   Reply With Quote
Old 02-08-2011, 11:55 AM   #4
Tech Master
 
heretic's Avatar
 
Join Date: Aug 2006
Location: europe
Posts: 1,106
Default

If the tire blew off the rim it's very, very likely to have the inner belt broken. All 4 tires go the trash. Sorry.

Expensive lesson but a lesson learned nonetheless : Never pull the trigger to max with a decently powerful motor. All it does is ruin the motor bearings prematurely, maybe break the magnet and of course its makes you ruin 4 brand new tires.

__________________
I love wedge bodies. I love dish wheels.
heretic is offline   Reply With Quote
Old 02-08-2011, 12:16 PM   #5
Tech Elite
 
Foxxrocket's Avatar
 
Join Date: Jul 2008
Location: Sonoma County
Posts: 2,018
Default

Quote:
Originally Posted by omegaf View Post
I had the car in my hand and i give it full power and it blew one tyre off the rim. i gotta glue it back now
they were brand new set of wheels too
Don't do that. It can hurt the car.
__________________
Tamiya 416X/ Tamiya TA-05 IFS/ Losi XXX-SCT/ HPI Baja 5SC/ Tamiya M05/ Tamiya F103/ Tamiya F104/ Team Associated 10R5O/ Kyosho IGT2/
Foxxrocket is offline   Reply With Quote
Old 02-08-2011, 03:21 PM   #6
Tech Adept
 
Join Date: Jan 2011
Posts: 189
Default

yea i kinda figured. the entire chassis shakes, screws come loose and generally the thing looks like it is about to blow up. All that at only 20% throttle on the remote. i think i need loctite for the screws and glue for the tyres.
if the car shakes like this at 20% then there is no way it can do 100% on a track. for starters it will be impossible to control with the tyres blowing up and the vibrations would probably make the whole thing jump. i may need to add ballast somewhere.
omegaf is offline   Reply With Quote
Old 02-09-2011, 08:50 AM   #7
Tech Elite
 
Foxxrocket's Avatar
 
Join Date: Jul 2008
Location: Sonoma County
Posts: 2,018
Default

Quote:
Originally Posted by omegaf View Post
If the car shakes like this at 20% then there is no way it can do 100% on a track. for starters it will be impossible to control with the tyres blowing up and the vibrations would probably make the whole thing jump. i may need to add ballast somewhere.
Without anything acting on the wheel, the centrifugal forces will cause the tire to separate from the rim. This is why your tire blew out. It also explains the violent vibrations from the chassis and why you should never handle a car while on throttle.
__________________
Tamiya 416X/ Tamiya TA-05 IFS/ Losi XXX-SCT/ HPI Baja 5SC/ Tamiya M05/ Tamiya F103/ Tamiya F104/ Team Associated 10R5O/ Kyosho IGT2/
Foxxrocket is offline   Reply With Quote
Old 02-09-2011, 11:30 AM   #8
Tech Adept
 
Join Date: Jan 2011
Posts: 189
Default

i understand that, however the wheels are not balanced. only one wheel blew out and it was one that was not rotating straight. the others are fine although the tyres balloon under the torque. i think i have a defective rim or something.
i will try to glue the tyre back on and see what happens.
logic tells me that those vibrations will exist even when the car is rolling and will make it behave oddly.
there is an insane amount of torque steering when i try it on my floor but then again traction is quite poor here. i am driving it at 20% though so i am guessing that with better traction it will be fine with 20% but no way 100%
omegaf is offline   Reply With Quote
Old 02-09-2011, 01:19 PM   #9
Tech Master
 
simplechamp's Avatar
 
Join Date: Aug 2009
Posts: 1,315
Trader Rating: 73 (100%+)
Default

13300kv is definitely WAY too high. On 1S that's pushing 50k RPM at full throttle, and on 2S nearing 100k. And only being able to throttle up to between 0-20% means you are losing 80% of the resolution and throttle control you could have. Even a motor with half that kv rating will give you more speed than you probably need.

You should run your numbers through this speed calc, I bet you will find you are geared for like 100 mph, LOL!

http://www.scriptasylum.com/rc_speed/top_speed.html
__________________
Serpent 811Be - Jammin X2 Carbon e-GT conversion - Axial SCX10 Honcho
simplechamp is offline   Reply With Quote
Old 02-09-2011, 01:52 PM   #10
Tech Adept
 
Join Date: Jan 2011
Posts: 189
Default

without knowing the end drive for the diffs, i know that spur and pinion are 19t and 61t so not too bad. i am using NiMH so it hits around 80k rpm on full throttle. i am at 88mph if we believe that link.

Last edited by omegaf; 02-09-2011 at 02:05 PM.
omegaf is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
Countersteer drift setup falls here! fujiyatt Singapore R/C Racers 216 02-07-2012 10:44 AM
B.R.C.C.C (Tingalpa) hooked_on Australian Racing 6962 11-07-2011 02:58 AM
Losi limited slip? Mr. Pickles Electric Off-Road 8 04-25-2008 11:05 PM
Onroad Setup Tools and Tips Pauly6401 Electric On-Road 14 03-31-2008 08:16 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 02:05 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