Floater axles

Dose gun drilling floater axles make them stronger, or dose it weaken them for weight saving?

 

Stronger, if done properly, to a proven formula to find the optimum wall thickness.
Simple explaination is that after a given point, the internal material close to the center, is just along for the ride. (and to add useless rotating weight).
Bob

 

definitely strengthens them... has some thing to do with adding more structure to the axle by creating internal surfaces where the gun drilling is. kinda like turning a square section of a chassis into two triangles by adding a diagonal tube... that one tube makes a dramatic diffence in the behavior of the whole structure.

as for how big that hole should be? i would have no idea

 

Just keep drilling them bigger and bigger until they break and then go back one notch? I'd like to know the formula to figure the hole. Ours are solid and I ain't gettin notin' drilled until I know how big. Is a single axle better than two separates in a full floater configuration? Just fishing for some extra input before we do something stupid. Thanks all.

 

Single or "live" axle is much more rigid. The axle becomes a major cross support to stiffen the entier assembly. I think they may be less prone to tire shake in a lot of instances as well.

 

gun drilled axle -- metallurgy

One reason gun drilling axles or many other bars are stronger than solid bars is metallurgical. When bar stock is made, the overall straightness, length, and strength are a result of a combination of internal stresses throughout the metal. Some are pushing, some are pulling. The load on an axle actually relieves some stresses and increases others. Those being increased are carrying the load.
Often if you drill out the center of bar stock, you relieve conflicting metallurgical stresses. The result is that the remainder of the metal is stronger because you have removed metal that is in conflict.
Unfortunately, you cannot always conclude that gun drilling always will increase the strength. It is dependent on how the bar stock was made. It also depends on how smooth the gun drilled inside surface is made. Roughness in the inside can be a stress riser leading to cracking and a failure just like a nick on the outside.
As far as the question that was posed about how big of a hole, a rough estimate from a stress relief standpoint is about 50% to 60% of the diameter. In one industrial application, about 85% of the metal (diameter) was drilled out for a maximum increase in strength. However, this was a high tech part with excellent process control from material selection all the way to machining and a lot of testing to that hole size that was too big.
One other consideration is the contribution to twist strength from the metal that is close to the twist center. It is too close to the center and as a result, is of little contribution. If you do an analysis of how much torque the metal near the center can transmit, you quickly find out not much. Consider a small diameter axle in a high power load. It readily twists under the high load. You can consider the small diameter axle to be equivalent to the metal near the center of a large diameter axle.
Bob Szabo, author of Fuel Injection Racing Secrets and 5000 HP on Methanol
www.racecarbook.com
(707) 446 2917