Outer Limits 4x4 Board

just wondring the best steel to use for a set of sliders on my 80 series, i have heaps or 50x75mm 4mm wall and 44mm tube with 2-3mm wall. i was thinking of using the 50x 75 off the chassie on crush plates to an inner rain and making hoops out of the tube. is this ok or to heavy? any suggestions?

yeh 44mm pipe would be overkill i reckon id go smaller tube with thicker wall. coul;d use the box from ur chassis to the pipe and id just use flat bar on ur chassis 75x8 would be plenty i would imagine

bowesy89 wrote:yeh 44mm pipe would be overkill i reckon id go smaller tube with thicker wall. coul;d use the box from ur chassis to the pipe and id just use flat bar on ur chassis 75x8 would be plenty i would imagine

i think the 44mm is diameter, with a 2-3mm wall thinness....

X2. A much better option than RHS.

44mm pipe is overkill? The next step down is about 34mm OD - I wouldn't use that for a slider that was intended to bear the weight of the car.

Here's 44mm steam pipe as a slider on a sierra.



Steve.

Why do you say that tube/pipe is better than RHS/SHS Steve?



It's a lot harder to kink or bend SHS than it is to kink tube. In fact the only advantage to tube over square I can see is it has less surface area to get caught up on stuff and hence slide over obstacles better.

Even then though I imagine the difference would be fairly negligible.




Ps. Not a dig, serious question.

what about using the factory mounting points? we are thinking about mounting the RHS directly under the sill with a thin layer of insertion rubber between the sill and RHS. Then making mounts that go back to the original factory sill mounts. That way the weight is taken by the sill along the entire length and the mounts mainly just locate it.

v840 wrote:Why do you say that tube/pipe is better than RHS/SHS Steve?



It's a lot harder to kink or bend SHS than it is to kink tube. In fact the only advantage to tube over square I can see is it has less surface area to get caught up on stuff and hence slide over obstacles better.

Even then though I imagine the difference would be fairly negligible.




Ps. Not a dig, serious question.

Round tube has the higher strength to weight. That's why in any application where weight is critical (like a race car) chassis etc are made from round tube.

tube has equal strength in all planes and with impact in all directions. RHS/SHS does not.

Whilst the corners of SHS/RHS will assist in preventing bending/kinking, the flat surface areas are susceptible to denting, thereby pulling the corners in and seriously weakening the structure. Basically, the flat surfaces of RHS/SHS add very little strength to the structure - all the strength is in the corners. That's not necessarily a bad thing, but in an application where the object is likely to see impact from multiple planes and requires high strength to weight, tube has to be the go.

Additionally, for the same wall thickness tube is lighter than RHS/SHS of equivalent size.

I guess it comes down to a few other factors too:

As you pointed out, tube has a smaller surface area to improve sliding

When tube has another tube welded to it via a notched connection, the weld has no corners and creates a joint that runs in multiple planes, not the case with an SHS/RHS connection where all the welding is on one face with the stress concentrated in the corners of the connection where the weld is at its weakest.

tube tends to have pretty good "memory" and will bend smoothly either side of a hit. Because of the deformation on a single plane, RHS will tend to kink at the point of impact.

RHS looks hack compared to tube IMHO

Just some thoughts.

Steve.

Cool, thanks for the explanation.

I was lead to believe that being a circle cross section, tube only really has one plane. So that when it gets bent or kinked, the whole section is compromised whereas SHS has four planes so that if one kinks it doesn't affect it so much.

I also thought that race car chassis' gained their strength from triangulation rather than materials? Tube being used for the aforementioned weight savings rather than any inherent strength advantage.


All good info though, I appreciate the response.