Chassis

[mud90mike]

Hi guys

I am thinking about making a chassis for an winch challenge vehicle,

its based on a landrover so I as going to mimic the box section (roughly 150mm x 60mm) but out of 4mm mild. I have been speaking to a few people about weight saving and have thought about using a dimple die and putting 50mm (ish) cut outs spaced regularly along the length on either side of the box section stopping short of engine and suspension mounts, this would allow me to get a really good galvanising job on the chassis and then I can simply stick a jetwash in to clean it. The only negative feed back I am getting is about whether this weakens the box section or a couple of people said it strengthens it, What do people think?

Thanks

 

[Wendelspanswick]

A: How will you get your dimple die inside the box and operate it?
B: 4mm wall thickness is going to take a lot of pressure to dimple!

 

[mud90mike]

A: It will start of life as two C sections (actually flat plate that I will bend) then be seam welded the same as the original
B: 30 ton punch should do it!

 

[Wendelspanswick]

Ahh, that makes more sense.
Well it definitely won't make it stronger!
There used to be a trick of cutting through the web of an I beam in a zig zag pattern, offsetting the cut and welding it back together, leaving the web full of hexagon shaped holes and effectively doubling the depth of the I beam which would increase the load carry capacity but that is not the same as sticking holes in the supporting sides.

 

[Wendelspanswick]

Found it, its called a Castellated Beam.

 

[outofthefire]

Although your punching holes I would think that the dimple should add stiffness to the wall of the box in a similar way that a corrugation stiffens sheet but I don't know whether that makes it stronger.

 

[Wendelspanswick]

Castellated beams have greater resistance to deflection, and can accommodate services.

Castellated beams have a deeper section than a comparable solid beam, which has a greater resistance to deflection. They are therefore most often used in long span applications with light or moderate loadings, particularly roofs. Since the weight of steel has not changed, the structural efficiency of the section in bending has been increased. A further advantage of castellated beams is the holes in the web which provide a route for services.

The web, however, is the main source of shear strength. Care must therefore be taken to ensure that the shear resistance is sufficient at points of high shear. For this reason the holes are often filled in using welded plate, at points of support and/or concentrated load.

The increased depth of a castellated beam will also increase its tendency to fail under lateral-torsional buckling. Where this form of failure is an important factor in the structural design, the improved efficiency of castellated beams may not be realised unless additional structural restraint is provided.

 

[mud90mike]

I can see why that would make a beam stronger as is doubling the height to increase the strength but keeping weight down, but I am not sure whether the same would work with a box section as I cant double the depth of the chassis, I assume that as the dimple would increase the stiffness of the box it would help but whether that out weights the lose of strength due to the cut outs I don't know.

 

[outofthefire]

It seems like a lot of work making your own box, why don't you use box, drill the holes and weld tube between them. You could leave a couple of tubes out if you want to be able to wash them out.

 

[mud90mike]

For the chassis to work it needs 4 curves in it, but I want to make each leg out of one-piece so there are no joins length ways, only Way I can see to do this is get it laser cut then bend and weld it I want to increase the thickness for strength but was hoping to punch it to balance out the weight gain. Not an easy job but i want it to last and they take a Huge amount of punishment.

 

[harryb94]

I think it's gigglepin that have a chassis similar to what you're suggesting on there challenge truck made by Richards chassis, have a look on the gigglepin Facebook page because I've definitely seen photos somewhere, they had a lot of holes but I think they may have been flanged

 

[harryb94]

Found the picture I was thinking of
https://m.facebook.com/TeamGigglepi...1432764074./312074628950518/?type=1&source=42

 

[mud90mike]

That's the type of thing I was looking to do, interesting they have done the top and not the sides

 

[dan.taylor.1]

It may not be feasible but most tractor loader booms are made like you're planning with two folded c sections, but they don't butt them,they overlap/interlock them and run a lap joint top and bottom. Don't know if it's any stronger but they don't seem to make them that way for any reason so strength is all I can think of.

 

[mud90mike]

Yep that's how the old landy chasiss were made two sections overlapping, seems I need to find someone good with solid works and do some testing!

 

[graffian]

If you want to see a stock chassis that was homemade, look online and you will find a bloke who made his own chassis.
I think he built a plasma table and needed something to cut out;-)