COST-chassis(using MS or Chrome alloy)

[BHARDWAJ]

wat will be approx. cost of complete chassis manufacturing using either MS-1020 or Chrome moly-4130 including all welding and other processes..and which one is better after considering all possible aspects of competition..

[BHARDWAJ]

wat will be approx. cost of complete chassis manufacturing using either MS-1020 or Chrome moly-4130 including all welding and other processes..and which one is better after considering all possible aspects of competition..

[Matt Gignac]

1020 will cost a bit less for the material cost involved, but once you figure in all the labor and machining costs, the material cost is a relatively small part of the equation.

You'll get the same stiffness from either metal, as the Young's Modulus is the same, but since 4130 has a higher yield strength, you can make some parts lighter around stress concentrations (for example, a-arm mounts, shock mounts, etc).

In my opinion, mild steel is the metal that will get you the most points at competition. Less expensive (more cost points), and I don't think the weight benefits of 4130 will affect performance enough to offset the cost.

Matt Gignac
McGill Racing Team

[Matt Gignac]

Oh, and our cost report for the frame came to around 1000$ for mild steel.

Matt Gignac
McGill Racing Team

[Jersey Tom]

Do some engineering, run some quick numbers. Doesn't take that much.

[Wright D]

The suspension mounts of a frame should not be designed with ultimate strength in mind, but stiffness. When designing the parts to be stiff, the stress levels should be kept low, even when using 4130. Remember, high stress = high deflection.

[Jersey Tom]

For the record we use 4130 for our chassis. Very available, especially in thin wall. That's the primary reason.

[KU_Racing]

I like mild steel, but If i built a chassis entirely on my own it would be 100% chromoly- 4130, if you have the time and money/sponsor, can be heat treated to exhibit some incredible properties- one of them being almost spring-steel levels of ductility and memory, without sacrificing yield strenght or young's modulus. i.e., if you use a heat treated chromo frame and you bend it, you could dtraighten it by heating it cherry hot with a torch and letting it cool.
one big disadvantage of a chromo frame is that to be welded properly it must be back-purged with argon or helium, which adds a huge amount of time to the welding process.

[Jersey Tom]

I'd say the chassis is overdesigned enough not to warrant heat treating. And if you did take that whole thing and cook it up to start any HT process i'd have to think it would twist like a pretzel, unless you had some fancy jig set up.

[KU_Racing]

the trick to heat treating a structure like that is that you normalize all the joints after welding and before you pull the frame off of your chassis jig- that way it will not twist when it gets heat treated.

[Jersey Tom]

Sounds like that'd get expensive. The most available shop resource to be normalizing all those joints while still on your jig would be an oxyfuel torch I'd think. Keeping the whole joint glowing cherry red / orange and letting it soak for a good 10 minutes at least to recrystalize.. then keeping the heat on it a bit more to let it cool nice and slow and not just quench itself.. that adds up to a lot of torch time and a lot of fuel.

But hey if you do that.. that's all the heat treating you need. No reason to harden your chassis past normalized condition (90-ish Rb?? Just under the C scale range)

That memory property you speak of, I've never played around with that. what kind of heat treating you talkin about for that? Q&T? Curious how long you'd temper that and at what temperature..

[KU_Racing]

At my old job, we built some big control arms for a military truck. They were 4130 welded tube; we normalized them, basically by the process you described above. They were sent out to heat treat. They were heat treated, then cooled over a long period to 0 C, with total time in the tank at about 40 hours. Kind of involved, but worth the results- we ran that truck over a durability course, bent the two lower arms, then straightened them by jigging the undamaged arm and heating the creased area to half heat and holding it there for about 6 mins- pretty cool when the metal straightened as it cooled.

[BHARDWAJ]

thank people for useful input..well we r using MS after considering various aspect.nw next problem is which kind of welding we should use TIG or MIG or if any one else.
forum shows a trend towards TIG but some people are saying MIG is good for MS..and above that we also need new welding machine for same...i m really hoping for ur useful sujjestions.