Tire adhesion and differential locking
In the “Differential Locking” forum, I posted, that, with a 2S battery, any power setting over 52% causes the car to swerve to the left, including tipping the car over. And any braking percentage over 70% causes the car to swerve to the right, also tipping the car over.
Thus it looks like the right drive tire has all the traction, both in acceleration and in braking, and thus tips the car over in opposite directions.
I want to thank “billy Weeks” and “LightFighter” for their forum comments.
I “locked” the differential with Silly Putty using the method described in this video. [url]http://www.youtube.com/watch?v=zkO-0zTQDhY&feature=related[/url]
With Silly Putty in the differential, there was no change in the cars swerving behavior. Everything was exactly the same as before.
So I exchanged the right and left rear tires with each other, and now, with 52% power, the car swerves to the RIGHT rather than to the LEFT and it is definitely more stable during the run. (I did not test how much more power I could use before tipping the car.)
Therefore, there is a significant difference between the two tires. One tire obviously has more adhesion than the other. I do not do burnouts and have not treated the tires with anything.
I assume that an un-locked, or semi-locked differential, will magnify any adhesion differences between the tires, so I am going to totally lock it with JB Weld.
I would appreciate any comments on the adhesive difference between tires. How do we detect such differences, and how do we deal with these differences.
FOLLOWUP -Tire adhesion-differential locking -
This is a follow-up to my post (#1 on this forum thread).
In that post I indicated that on heavy acceleration the car would veer in the direction opposite that of one specific tire, independent if the tire was on the left or right of the car. And on heavy braking the car would veer in the same direction that that specific tire was on. When veering occurred, it was always tire related as stated, and never once did it ever veer in the other direction.
My conclusion is that one tire has more adhesion than the other and the differential was magnifying this difference.
JB Weld in the differential made a significant change. I now get exactly 50% veering to the right and 50% to the left, independent of what side of the car the tires are on.
Therefore, the locked differential is now mitigating the adhesive difference between the tires.
Based on the 15 successful runs before and the 15 successful runs after the JB-Weld, the median ET decreased by 15% and the median speed increased by 16%. However, this is not a definitive improvement, because there are many variables involved. For example, one pre-JB-Weld run had a lower ET than any of the JB-Weld runs.
However, the two 15% improvements would seem to be convincing evidence that an improvement has really occurred.
The power generated veering is no longer a function of tire adhesion, there is a performance improvement, and even with the locked differential, it is easy to turn the car around at the end of the run.
Bottom line, I am very happy with the locked differential.