Vitamin K wrote:ngyoung wrote:
It is also pretty easy for one of the wheels to get knocked out of alignment during racing. It is usually bad enough having just that one DFW to worry about being bumped.
... I had to grip the nail head fairly well with the pliers and it took an appreciable amount of torque to rotate the axle heads. However, I just don't see a lot of forces that act on a typical pinewood derby car that are going to cause the rear axle rotation to change. ...
The "lever arm" of an axle bent 2.5 degrees at 1/2" from the nail head is 0.022 inches. Given so little leverage, it seems that an impact capable of twisting the axle in the hole would as likely bend the axle. Such an impact would not care if the axle were originally bent or straight!
I think that this is testable, though. We could set up a car with no offside front wheel, exposing a rear axle to impact.
First phase:
1. Using bent axles, align the rears.
2. Station a PWD block lengthwise on a track flat just past where the flat begins positioned so that the offside rear wheel must strike the end of the block.
3. From the normal starting line, release the car and allow it's offside rear wheel to strike the block.
4. Check rear wheel / axle alignment without changing the alignment.
If the check shows a change in the alignment, then either the axle was twisted OR the axle was bent.
Repeat the above using progressively heavier blocks until a check shows a change in alignment or you run out of patience.
If alignment did change, then we could differentiate between the axle being twisted or bent by the impact.
Second phase:
1. Insert a straight axle in place of the offside rear axle.
2. Verify that the rear alignment is approximately as good as in the first phase above.
3. Station the heaviest PWD block above on a track flat just past where the flat begins positioned so that the offside rear wheel must strike the block.
4. From the normal starting line, release the car and allow it's offside rear wheel to strike the block.
5. Remove the straight axle and test it for straightness by rolling the shaft on a flat hard surface. If the axle resists rolling at any point, then it has been bent by the impact.
Whatcha think, folks? Would that answer the question?