I've had a somewhat heated debate on rctech.net about using a one-way on carpet with foams. I thought I'd post my reasoning here as well.
Here is why I decided to go down the one-way path for carpet racing, versus the traditional adjustable limited slip differential:
1. A one-way ensures maximum use of the drive train power. An LS diff decreases a percentage of the power to the outside wheel where traction is the greatest and gives it to the inside wheel which is unloaded and "slipping" because of the diff action. Unless the front diff is tightened to the point where it functions like a spool, there will always be a loss of acceleration from the drive train. By tightening the diff you can minimize the loss of power, but then you start to introduce the problem of both front wheels fighting each other in the turns where the inside wheel wants to spin faster than the outside wheel because of the steering arc and their different turn radiuses. This scrubs too much speed on corner entry and also causes the front end to hop/skip/bounce. The beauty of the one-way is that it maintains 100% of the power to the outside wheel, while allowing the inside wheel to spin as fast as it needs to for its own tighter radius around any given corner. You can't count on 100% of the power to be applied in the rear either, since it also has an LS diff which is normally even more loose. The high amount of traction provided by foams on carpet is an advantage that should be exploited for acceleration, as well as cornering.
2. The first knock on the one-way that needs to be addressed in another area of the setup is too much initial turn-in steering where the car can become twitchy. I have found that you can address this effectively by using 0 front toe out (which also improves straight line speed and makes the car easier to drive) and a lot of caster (which also improves another weakness of the one-way, on-power push)
3. The second weakness is abrupt loss of traction as the front suspension reaches maximum roll and load prior to the apex. This can be addressed by using a stiff front anti-roll bar (which is also the best way to improve steering response without making a car twitchy; chicanes anyone?)
4. The last weakness is reduced on-power steering or push. The steep caster angle helps here as well. However, an interesting bit of information that I picked up from a well renowned scale racing book called "Engineer To Win" by Carroll Smith states that although a front anti-roll bar may decrease overall front traction mid corner, it actually increases on power steering by transferring the forces applied to the outside wheel, through the bar, to the inside front wheel which is instrumental in steering out of corners as the cars weight shifts to the rear. Carroll illustrated this to emphasize the benefit of using more ackerman, which increases the steering angle of the inside wheel to gain even more steering on corner exit. Of course the one-way and camber effects from the steep caster angle, which causes both front tires to dig in mid corner as the steering wheel is at or close to full lock (the inside wheel now gains a lot of positive camber for a wider contact patch), assist with providing enough traction mid corner that you would normally lose when using a stiff front anti-roll bar.
Now this type of setup became a little more difficult when I switched from the XRC FK to the FK05 with its new front biased weight distribution, which produces less rear mechanical grip. And coupled with the increase of front traction from the steep front caster angle, the rear needs more traction out of the tires, unless you want to mount a lot of weight to the rear. I found the orange-purple/double pink and plaid/magenta combinations were the ticket here to actually bring the car into, and not out of, balance.
The end result from all this is an easy to drive car that scrubs very little speed on corner entry and mid corner, is extremely responsive but not twitchy, has great steering throughout the entire corner and accelerates faster through and out of the corners. I've even found that dialing down the brakes to 60% allowed me to come in extremely fast and tight to corners for passing and then blip the brakes to rotate the rear end around quickly and smoothly, with minimal scrubing of speed. The one-way then allows me to keep the position by accelerating faster out of the corners.
I welcome anyones feedback and constructive criticism.
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