Monday, May 12, 2014

RE-Xtreme RC Drift Bible - Watch your toes.

RC and Toe,

Lets look at some ideas and explain toe. Remember to experience the results, try, change and evaluate.

Toe changes the degree that the wheels point in or out when travelling normally

Just like your feet. Look down. Point toes in. point toes out. 

Toe In creates stability, like skiing down hill with your skis pointing in. you are slow and stable.
Toe Out creates instability, you are fast and on the edge of out of control, but turning is faster as you are basically already turning a little. 

Toe applies to the front an rear independently to effect the front stability or the rear stability.

Most RC chassis have toe blocks and hubs to control the basic toe geometry.
I will reference

FF = Front of Chassis Front position
FR = Front of Chassis Rear position
RF = Rear of Chassis Front position
RR = Rear of Chassis Rear position (dictates rear toe)

As the front of the chassis toe changes can be changed by the length of the steering turnbuckles, the suspension geometry at the toe blocks is basically ignored.

The basic configuration at the front of the chassis is ZERO degrees but it is adjustable at the hub by steering each wheel’s default position slightly.

Adjusting Front Toe Changes

Adjustments to left and right side should be done at the same time.
Lengthening the steering turnbuckles pushes the wheels in at the front. Toe In
Shortening the steering turnbuckles opens the wheels at the front of the chassis. Toe out. 

Toe out effectively makes the car nervous in a straight line as one wheel will basically want to steer with minute steering input. 

For drift, going straight is a bit of a luxury so the idea of front toe setting should be considered more in relation to ackerman angles with the steering at lock rather than simply in a straight line.

For race cars that rely on straight line speed, the tyres scrubbing across the track in a straight line can vastly effect speed and stability. 

For drifters. Zero or 1 degree toe out is a good start. 

Personally I like a bit more toe out in the 3.5 degree range as it also gives a bit more angle at max lock on the front lead wheel.

Adjusting Rear Toe Changes

At the rear there is typically no easy adjustment (with exceptions of course).
Rear Toe changes are made in 3 ways.

The toe block
The distance between the suspension pins on the RR mount controls the toe angle
Stock is usually set at around 3.5 degrees for stability.

Increasing the distance on the RR block creates toe in and the whole suspension arms will angle forward and in.

Decreasing the distance usually aims to remove toe in and results in zero degrees.

Option parts are aimed at reducing rear toe towards Zero for a more lively rear end and aiding transitions.
If you want to keep more realistic slower transitions, a stock rear 3.5 degree  block will be fine.

Tamiya have a stupid numbering system for their blocks. XL 1x 2X etc but basically they have a table to match to 1,2,3 degrees.

Moving past zero will create a rear steering chassis… a little hard to control.
So there are hub options to add that 0.5 degree of "safety".

Toe blocks control the angle from near the centre of the chassis and the change effects the geometry in more than one way. The whole rear suspension arm is angled forward. 

As you replace the toe block the angle on the suspension arm becomes 90 degrees to the centre line.
Wheelbase is also largely effected as the wheel moves forward or back a few mm. 

So adjusting the spacers around the rear suspension pin is usually necessary.

Above is a typical "active" setup. ready for drift.

  The rear hub Options
The angle of the hub has a built in alignment. Most are Zero or 0.5 but it is possible to get the 3.5 degree toe in on the hub itself.  Adjustable hubs will also do this.

Simply replacing the hub with another with a set angle is simple.
This way the wheelbase is relatively unaffected

  Adjustable hubs
Recently some rear setups like the Drift Package type C allows alignment control over the rear in a similar way to the front by means of a turnbuckle.
It is easy to misalign settings. Setup boards and rigs with calipers and measured lengths are recommended for this.

There are a few issues with toe that might need to be addressed

1.       Chassis Wheelbase ... follow this link 
2.       Steering Ackerman … follow this link.

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