Triple Diff Basics -
12.28.2006, 01:01 PM
TRIPLE DIFF BASICS
(This article is from RCDRIVER)
Tuning your Diffs
Most diffs are designed to be filled with viscous silicone fluid, which alters the diff’s tension, i.e. makes it “LOOSE” or “TIGHT”. What this is really doing is changing the diff’s “limited slip” properties. A loose diff will send more power to a wheel that loses grip, robbing valuable power to the wheels that have traction.
Some general rules that can be applied for diffs.
GENERAL DIFF RULES:
A looser diff provides more traction and will enable vehicle to work better on rougher surfaces. A stiffer diff works better on high grip conditions and improves acceleration and throttle response.
A good starting point for 1/8 scale biggies and truggies, is to fill the front diff with 7k wt. silicone fluid. Using thinner fluid will loosen the diff’s action, improving steering response, but will also tend cause a decrease in stability under hard acceleration, as the front wheels will more likely to pull to one side or the other in reaction to the chassis transverse weight and to irregularities in the running surface. Thicker fluid enables the front wheels to pull harder and with greater stability, and on-power and high-speed steering will improve, but you will lose some off-power steering response, especially in slow turns. Try to use fluid no thinner than 3k or thicker than 10k in the front diff.
Buggies- start by filling the diff with 10k wt silicone. This usually provides a good combination of acceleration and stability. If your vehicle leans toward over-steer when exiting turns, using thinner fluid such as 5-7k in the center diff will send more power to the front wheels, allowing them to pull harder. At the same time, drive to rear wheels will be slightly diminished. The shortcoming is the overall acceleration will be reduced, as more power will be sent to the unweighted front wheels, while less goes to the rear wheels.
A looser center diff will improve off-power steering response, as it reduces wheel-slip, thus inhabiting understeer, or push, by allowing the front & rear diffs to function more independently during cornering.
A tighter center diff sends more power to the rear wheels , thus allowing the car to be “ steered” more by the rear wheels, increasing on-power steering.(but at the loss of stability on slippery surfaces)
Truggies- It is not uncommon to use 20k or even 30k silicone fluid in a truggies center diff to compensate for the extra heft and rotating mass of the tires. If the tires tend to expand hugely during acceleration, thickening the fluid the front diff and center diff is often a remedy. Some drivers have run up to 20k diff fluid in front diff to reduce tire expansion.
Of the 3 diffs found in the vehicles, the rear is run the loosest. This is done in a effort to achieve maximum traction from the rear wheels- during acceleration as well thru the bumps. Most racers fill their diffs with 1k-3k, but no more than 7k. Using anything thicker will create a condition of oversteer when exiting turns, making the vehicle the vehicle difficult to control in almost any conditions.
This article was originally written: by Frank Masi of RC-Driver
Copied by: Shayne Richardson
Last edited by sjcrss; 12.28.2006 at 08:50 PM.