4130 vs 1020 - Racing Carts

Don't get to bogged down in the basics. We know most of it. 4130 is easier to weld than 4140, and maybe harder to heat treat. 1020 is easier yet to weld, but lower tensile strength.

My son's engineering class (club?) is build a 4wd race cart for a big competition. He has done the structural calculations with what he considers a decent safety margin using 4130. Some years back I had a chat with a local marine shop owner (Keith) who was building race carts for his son at the local speedway for their 2wd youth cart racing class. He said they were using 1020 DOM because it flexed more in hard racing.

Now there are some class differences. The cart my son's group is building is using a specific nominal 14hp motor and using a full 4x4 drive train. The Keith's son was racing nominal 6.5hp Subaru Robin clones like the Predator 212.

I'm not sure what my question is. I'm just trying to wrap my head around it as "not an engineer."

-- Bob La Londe CNC Molds N Stuff

----------------------------------------- There are some strongly believed misunderstandings about the properties of steel, and physics in general.

I think the choice depends on how they deform vs break in a crash. Below their yield points their bending resistance (Young's Modulus) and thus chassis stiffness is practically identical, like all steel, but 4130 has a higher yield point.

The suspension geometry's job is to keep the tire tread flat on the track while the body rolls in turns, and chassis flex can interfere. My understanding is that 1020 controls the limited deflection permissible as well as the same size and weight of 4130.

The goal is to limit crash deceleration to what the driver can handle because race car frames became too strong and stiff, the car survived but the driver didn't. I don't remember the auto numbers, for aircraft Col. John Paul Stapp raised the limit of survival from an estimated 20g to a proven

Don't get to bogged down in the basics. We know most of it. 4130 is easier to weld than 4140, and maybe harder to heat treat. 1020 is easier yet to weld, but lower tensile strength.

My son's engineering class (club?) is build a 4wd race cart for a big competition. He has done the structural calculations with what he considers a decent safety margin using 4130. Some years back I had a chat with a local marine shop owner (Keith) who was building race carts for his son at the local speedway for their 2wd youth cart racing class. He said they were using 1020 DOM because it flexed more in hard racing.

Now there are some class differences. The cart my son's group is building is using a specific nominal 14hp motor and using a full 4x4 drive train. The Keith's son was racing nominal 6.5hp Subaru Robin clones like the Predator 212.

I'm not sure what my question is. I'm just trying to wrap my head around it as "not an engineer."

The engineer who explained that to me wasn't talking about go karts.