R/C Tech Forums

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

Like Tree8Likes
Reply
 
Thread Tools Search this Thread
Old 05-11-2017, 10:51 PM   #31
Tech Addict
 
nubs's Avatar
 
Join Date: Mar 2016
Location: Tracy, CA
Posts: 530
Trader Rating: 2 (100%+)
Default

Quote:
Originally Posted by ixlr8nz View Post
The problem is the set up guides are very general and often not written to specific situations. For example with a spool more droop = understeer due to the inside wheel not diffing out — like a go—kart going slow. However with a ball diff more droop = more grip at that end due to more tyre contact. Its not really a one size fits all situation. Also people get this idea that less droop means less roll. Look closely and you will often see wheels in the air due to little droop, but the car still rolls. If you want less roll then raise your roll centre or change springs/anti roll bars.

The other factor that goes against this theory, is the suspension that becomes maxed out due lack of droop goes from being sprung weight, to being unsprung. This would affect the balance somewhat.

Lastly, you will only see changes in handling when the droop limit is reached. For example if all four wheels never leave the ground, then it makes no difference what your droop setting is.
But it does matter my friend. As I explained your wheels don't need to leave the ground for one to have more traction than the other.
nubs is offline   Reply With Quote
Old 05-11-2017, 11:34 PM   #32
Tech Addict
 
Join Date: Mar 2002
Location: New Zealand
Posts: 547
Default

Quote:
Originally Posted by nubs View Post
But it does matter my friend. As I explained your wheels don't need to leave the ground for one to have more traction than the other.
Theres no disputing that fact. When all wheels are on the ground, the suspension is working within its range (the arms haven't hit the limits set by the downstops). The outside tyre will have more force on it compared to the inside one during cornering.
ixlr8nz is offline   Reply With Quote
Old 05-11-2017, 11:51 PM   #33
Tech Master
 
gigaplex's Avatar
 
Join Date: Dec 2015
Location: Melbourne, VIC
Posts: 1,302
Trader Rating: 2 (100%+)
Default

Quote:
Originally Posted by ixlr8nz View Post
Theres no disputing that fact. When all wheels are on the ground, the suspension is working within its range (the arms haven't hit the limits set by the downstops). The outside tyre will have more force on it compared to the inside one during cornering.
Not always true. Gravity still acts on the car as it rolls, which can keep the wheels on the ground even if the droop screws make contact with the chassis. If droop screw contact always meant that the wheels leave the ground, then cars with limited front droop would do a wheelie while accelerating, being unable to turn. But the reality is that the limited droop reduces weight transfer to the rear, and increases turning while on power.
gigaplex is offline   Reply With Quote
Old 05-12-2017, 12:07 AM   #34
Tech Addict
 
nubs's Avatar
 
Join Date: Mar 2016
Location: Tracy, CA
Posts: 530
Trader Rating: 2 (100%+)
Default

Quote:
Originally Posted by ixlr8nz View Post
Theres no disputing that fact. When all wheels are on the ground, the suspension is working within its range (the arms haven't hit the limits set by the downstops). The outside tyre will have more force on it compared to the inside one during cornering.
It's not a fact. You believe it because I'm sure someone else that didn't understand the physics told you as much, or you "figured" it out in your head and know it's right because your gut says so. If you want to continue believing your reasoning go right ahead, but please stop telling people this explanation as though it's fact.
nubs is offline   Reply With Quote
Old 05-12-2017, 12:09 AM   #35
Tech Addict
 
Join Date: Mar 2002
Location: New Zealand
Posts: 547
Default

Quote:
Originally Posted by gigaplex View Post
Not always true. Gravity still acts on the car as it rolls, which can keep the wheels on the ground even if the droop screws make contact with the chassis. If droop screw contact always meant that the wheels leave the ground, then cars with limited front droop would do a wheelie while accelerating, being unable to turn. But the reality is that the limited droop reduces weight transfer to the rear, and increases turning while on power.
Without a camera its hard to prove either way on that subject(maybe you.have an example), however I can say plenty of cars lift wheels under acceleration in rc and real life. Those cars have weight transfer that is not affected by droop. Think dragsters, monster trucks etc. Of course you have to have huge grip + power to do this. You also have to remember the rear suspension squats down as well.

Last edited by ixlr8nz; 05-12-2017 at 12:32 AM.
ixlr8nz is offline   Reply With Quote
Old 05-12-2017, 12:46 AM   #36
Tech Master
 
gigaplex's Avatar
 
Join Date: Dec 2015
Location: Melbourne, VIC
Posts: 1,302
Trader Rating: 2 (100%+)
Default

Quote:
Originally Posted by ixlr8nz View Post
Without a camera its hard to prove either way on that subject(maybe you.have an example), however I can say plenty of cars lift wheels under acceleration in rc and real life. Those cars have weight transfer that is not affected by droop. Think dragsters, monster trucks etc. Of course you have to have huge grip + power to do this. You also have to remember the rear suspension squats down as well.
You're not explaining how such a difficult to observe wheelie would result in better turning in my example. If you concede that they do in fact stay on the ground, which is the only way the car would actually turn, then you must concede that droop screw contact doesn't guarantee that the wheel leaves the ground. They'll still leave the ground with excessive grip and power, though.
gigaplex is offline   Reply With Quote
Old 05-12-2017, 12:47 AM   #37
Tech Addict
 
Join Date: Mar 2002
Location: New Zealand
Posts: 547
Default

Quote:
Originally Posted by nubs View Post
It's not a fact. You believe it because I'm sure someone else that didn't understand the physics told you as much, or you "figured" it out in your head and know it's right because your gut says so. If you want to continue believing your reasoning go right ahead, but please stop telling people this explanation as though it's fact.
Sorry mate, I will make sure I get approval from you before posting on these public forums again 😁

Over and out from me as controlled from above.
ixlr8nz is offline   Reply With Quote
Old 05-12-2017, 06:24 AM   #38
Tech Elite
 
Join Date: Dec 2011
Location: Raleigh, North Carolina
Posts: 2,110
Trader Rating: 42 (100%+)
Default

Beam me up.
__________________
Aaron Moore

Serpent America/Desoto Racing, McFactory Motorsports, Team Trinity, Pro-Line/Protoform, Hobbywing North America/FalconSEKIDO, HRP Distributing, PTRC Racing, Ho B Max
Antimullet is offline   Reply With Quote
Old 05-12-2017, 09:00 PM   #39
Tech Elite
 
Join Date: Jun 2003
Posts: 3,995
Trader Rating: 3 (100%+)
Default

All I know is if my rear rolls, then hits the droop screw (lifting inside rear wheel), the rear will tend to spin out
__________________
www.rccartips.com
www.f1rccars.com
www.f1rcclub.com
http://www.youtube.com/user/rccartips/
http://www.facebook.com/RCCarTipsFan
rccartips is offline   Reply With Quote
Old 05-13-2017, 07:33 AM   #40
Tech Regular
 
OttoKrosse's Avatar
 
Join Date: Jan 2014
Location: Mesa, AZ, USA
Posts: 379
Trader Rating: 3 (100%+)
Default

Quote:
Originally Posted by howardcano View Post
I always run the rear diff open (lube only). When traction is very high, adding some viscosity can help out of the corners, but it also makes the car less stable under power, and my reflexes aren't fast enough any more to compensate.

The front diff viscosity depends on both horsepower and grip. As they increase, go higher on the viscosity. This accomplishes two things: first, it keeps the inside front tire from spinning under power coming out of a corner, and second, it offsets the thrust of the front end to the tire with more weight loading. This makes the car more stable under trail braking (since the outside tire thrust counters the chassis yaw), and lessens understeer when accelerating out corners (since the outside tire thrust makes the car yaw into the corner).

I adjust the front diff oil viscosity to achieve a nice balance of stability under trail braking and on-power steering. Going too high on the viscosity will make the car understeer into a corner and oversteer coming out of a corner.

Using too high a viscosity will also cause the car to scrub off speed in mid-corner and in sweepers. It's really noticeable in VTA, since the available horsepower is low.

For VTA, I'm running 50K in the front diff; for USGT, 300K; and for 17.5 TC, 1M. The most sensitive car seems to be the TC, since the tires are stickier and the horsepower is greatest. I've gone as low as 200K on very low-traction surfaces.
Thank you Howard!!!.... that is an excellent explanation of front diff setup!!!!!

I've been running 2.5 mil oil in my front diff on a medium to high grip asphalt surface since I installed it and prefer the diff over a spool, may have to try some lighter weight oil to test your data. I find the front diff gives me better 'feel' and stability entering and exiting corners and can see the difference on the track when I'm able to gain on cars (or lose less distance to faster drivers) in the infield sections.

I suggest the OP try a front diff and if it doesn't work he will always have a back-up diff that he can setup with a different viscosity oil for different track conditions....just my .02
__________________
This space for rent.

Oo=00=oO
OttoKrosse is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
4wd to 2wd conv. knapsty637 Electric Off-Road 18 10-15-2014 06:04 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 03:35 AM.


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