Racing Chassis Steels and Alloys

[MONGOOSE505]

Hi

I have just joined the forum today because I urgently reqiure help from people who have a working knowledge of racing chassis and the type of metal alloys that are used.

What in your opinion is considered to be the best three materials for building a race chassis other than carbon fibre. It has been suggested that I should use spring steel or 4130 chrome alloy, but I need a modern and intelligent alternative that is readly avaiable to buy in England.

According to the rules I have to follow the term “steel” means an alloy of iron and carbon with an iron (Fe) content of more than 50%, or an alloy which reacts positively to the F.I.B.T. chemical test.

The chassis material must perform in a high speed environment with sharp bends and twist that generate 5-8 g-forces. In addition to these forces, the chassis must be robust and offer some flexibility so the alloy can return to a neutral state with no over or under steer.

The materials you recommend will be considered in the use of building a skeleton race sled, I have attached a two jpeg for a reference and a short video provides a insight to the physical conditions the alloy must deal with

http://www.skeletonsport.com/photos/?ph ... 1690&I=187
http://www.skeletonsport.com/photos/?ph ... 1691&I=186
http://www.fibt.com/index.php?id=97

I understand this an unusual request but I think car and skeleton racing have the same charactristics with regard to materials used

I have just be ripped off by a american sled builder, who has cancelled my order and sold my sled to an American racer. I have 26 days to source materials and build my own race sled,before my season starts,so I need help and now rely on the generosity of others.

If you do reply, I would like to thank the person who supplied the information, your help is greatly appreciated.

Mongoose

[Jersey Tom]

You can get a 4130 equivalent in England without too much trouble. I just can't remember what the code is. I think it may be 15 CDV 6.

Only reason to use CroMo steels is they weld REALLY nicely and are heat treatable for high-stress. If you're building a tube spaceframe and the main issue is stiffness rather than yield stress, some simple mild steel works as well. 4130 is also generally available in more tube sizes.

[MONGOOSE505]

Hi Jersey Tom

The frame of a sled is built using flat sheet metal with a min thickness of 3 mm, from what I have seen no tubing for a space frame is generally used.

Because of friends,family and business contacts I now have the poeple in place to manufacter this sled with little or no lead time. The area I have little knowledge of is the types of metal alloys being used for chassis design

In your opintion, other than 4130 cromo, what other alternatives would be suitable alternative to used in a racing chassis envoirnment based on the limited information I have provided

Cheers

Mike

[Jersey Tom]

Oh.. this thing is literally a bobsled? In that case it probably doesn't matter what the hell you make it out of. Make it out of mild steel, it'll be cheap. Going to be the same stiffness as 4130 or anything else, and I doubt you're going to be stress-limited.

[PlatinumZealot]

Holy moly!! that video was a little too extreme..

The blades have to be made of the same material?

There are some stronger regular steels you can use..

You can get steel like 1040 (what they use to make steam pipe) i dunno if you will easily get it in sheet form though..

Do you have any dimensions or drawings of the sled?

[flynfrog]

I am assuming that the material acts as the suspension similar to the way a kart works.

And I think most karts use CroMolly alloys

[MONGOOSE505]

Hi

The runners (blades) are a special steel that can be purchase thru one company in switzerland, I have them.

The sled design is simple to build but the materials used is the key thing because the material acts as the suspension and the flex paterns provide limited steering and must me robust as hell

For example,

As you go into one of the bends the sled must flex because one side of the sled will be higher due to the angle of the bend,

In the turn you are forced upwards to the highest point of the turn, the sled will be in a neutral position because you will be at a 90 degree angle and the track is flat

The exit point of turn you have the g-force and angle of exit causes the sled to flex again, because of the cruve of track, at the point the materials must snap back to a nuetral state beacuase any under or over steer will mean that you will hit the side walls at speed and this is bad and very painful to me.

Generally there are 14-17 turns in quick sucession over one mile of race track so the sled material can not break and must have a memory.

Mike

[PlatinumZealot]

Chome moly steel is good.. but suppose you could use aluminium?? or cheaper steels?

this is just me...(keep in mind i'm no professional! )

Well i would go about it like a machine design and then I would find the material and/Or size afterwords..

I would Get a basic design drawing of the sled.. MAIN dimensions of the structure itself..

what you need to find is where and how forces/load act. Then "Plug in" your Forces material/Part sizes into the program/calculation and see if it holds up..

you Start by making a few simple diagrams.. of the Sled in the worst case scenarios..

example

one blade is on the curved bank and the other on the flat section..

With like a 250lb man on the sled..

you use a speed and curvature of the track.. e.g 90mph through a turn of radius 20m

I guess air drag is a big deal so you can put that in the mix.

You also have the possibility for effects like fatigue (turn after turn) and impact (the sled drops of or crashes into the walls)

then you start to calculate the forces acting. (manual or with a program)

Then use a program like SolidWorks.. draw the sled and apply the Forces that you calculated on the model, use different materials and see if they fail..

Or instead of solid works manual calculation, to see if the material is strong enough.