flawless fabrication

[corx]

I happend buy this, check it out

Don't know if you've seen this, it's a Baja 1000 WRX build:

http://www.dirtyimpreza.com/forums/showthread.php?t=5162

my comments are wow.

discuss:

check out the fab work on this car. amazing or not?

I wonder why they went for cromoly instead of mild steel for the stub frames. do you guys think the lightness of cromoly is worth the risk of cracking it? or should they have gone with the forgivable mild steel with more weight.

I wonder what wall size cromoly tubing they used for the stub frames? do you think it should be thicker for strangth or thin for lightness.

I wonder why they used a typical ball joint instead of a spherical rod end type ball joint for the lower front control arms. do you guys think a spherical rod end type ball joint is overkill or they just didn't think about doing it? or maybe do you think they wanted the servicability of a standard ball joint over a spherical rod end type ball joint?

I wonder if they used limiting straps on the suspension? does anyone do this in wrc? or do they just let the strut take the blunt of the forces at work?

as far as what I think:

I think the fab work is perfect. the welds look to be in good shape. the aluminum parts and bits look truely great. the jig they built was great.

I beleive they felt that the cromoly would be light and very ridged giving precise driving engagement. the thick aluminum skid plate will protect it from being cracked but personally I would have went with mild steel. it is cheeper and has that little bit of flex to make sure the rigors of the trails would not alow cracking.

the wall thickness looked sort of thin which would mean they went for the light weight but it is always hard to tell when it comes to photos.

on the lower front control arms. I think they maybe didn't think to use a spherical rod end type ball joint. as you might be able to tell I don't think it is for servicability because of the type of money they have already put into this car. it wouldn't take much to build a couple sets of extra control arms to swap out and it would be faster than beating out the old standard ball joints and pressing in the new ones.

[99STM]

Those are some awesome fab skills.

[WheelGap]

If you want to see something where the fabrication bar is set way way higher, check this out:

http://www.race-dezert.com/forum/showthread.php/31417-Something-New!!

[Aki]

If you want to see something where the fabrication bar is set way way higher, check this out:

http://www.race-dezert.com/forum/showthread.php/31417-Something-New!!

Slick, that's almost unreal... and just as things should be 

[kandykoated]

the better part of the 4130 compared to you mild 1020 steel is that 4130 has a tensile strength of 95,000psi while the 1020 is only 80,000psi unless you go with the 1026 grade steel which is normally for OD's larger than 2" and wall thicknesses heavier than .156"
that has a tensile strenght of 87,000 psi which is still 8,000psi less than that of a thinner walled 4130,

as for the yield point
4130-75,000psi
1020-70,000psi
1026-72,000psi

as for weight here are a few figures
(type of steel-o.d.-wall thickness-weight/foot (lbs)
4130-1.0"-.065"- .6491
4130-1.25"-.065"- .8226
4130-1.5"-.065"- .9962
4130-2.0"-.065"- 1.343

1020-1.0"-.065"- .6491
1020-1.25"-.065"- .8226
1020-1.5"-.065"- .9962
1020-2.0"-.065- 1.343

so to conclude 4130 is not lighter infact it is the same as 1020 steel except that is goes through a completely different process in order to get the strength it has and to get the shearing strength. the best part is that is the onlyt difference between the two they start out as the same exact two pieces of steel but through refinement and a few more processes they make it stronger and more durable

hope this can help ya out some
BTW-Very good questions to be asking i liked it alot your trying to figure out why certain groups of enthusiasts use the different types and styles of products

[kandykoated]

as for the wall thickness and size of the tubings the funny part of it is that the thicker the wall tubing the less tensile strength and yield point you will have.
 usually anything over a .190" will have 5,000psi less of a breaking point
its hard to explain it but basically through the processes it goes through it loses its strenght the more you stretch and heat the metal even if they say its cold rolled the friction from rolling it will actually create the heat

[Aki]

Very cool, thanks for the insight.

[corx]

what I mean by lightness is that drag racers use cromoly because it has a higher tensil strength there for they can use a thinner wall material, thus making it lighter than mild steel but being just as strong. the problem is that the carbon content in cromoly makes it more brittle and more prone to cracking and breaking. Mild steel is able to be strong yet give enough to prevent cracking or breaking. this is why cromoly cages are banned in road racing, wrc, and nascar. the only reason why drag racing alows cromoly is because lighter is faster and that matters more than safety.

[corx]

If you want to see something where the fabrication bar is set way way higher, check this out:

http://www.race-dezert.com/forum/showthread.php/31417-Something-New!!

wow, those guys have some balls. building a-arms out of flat stock would take soooo long... I really like the weld quality. nuff said.

[kandykoated]

what I mean by lightness is that drag racers use cromoly because it has a higher tensil strength there for they can use a thinner wall material, thus making it lighter than mild steel but being just as strong. the problem is that the carbon content in cromoly makes it more brittle and more prone to cracking and breaking. Mild steel is able to be strong yet give enough to prevent cracking or breaking. this is why cromoly cages are banned in road racing, wrc, and nascar. the only reason why drag racing alows cromoly is because lighter is faster and that matters more than safety.

thinner walled or not, 4130 and 1020 start out as the SAME thing 4130 goes through a longer process in order to make it the way it is there for the weight difference between the two is zero, if there was ANY amount at all it would be in the hundreths of a pound per foot

the reason drag racers can use 4130 is because the way their dragsters are built, they are made for straight line racing yes they are under alot of g forces but from one direction, which would be compression.
wrc, nascar, etc. doesnt use it is because there is a load being put on it from all angles as in fatigue stress 

as for the carbon content of 4130 compared to the 1020 it is very minimal

4130 has roughly a 0.30% carbon rating, has double the maganese at 0.8%, and also has about 1.0% chromium which gives the 4130 the better strength than 1020

1020 has on average 0.20% carbon rating, 0.4% maganese, and 0% chromium

the reason why the cromoly can crack and break under stress is because it is used in places where it wasnt meant to be used. cromoly is a  VERY hard metal therefore constantly pushing it in a way it was not designed will stress it too far and eventually break it

[corx]

roll cages see the same stresses when crashed doesn't matter in what sport...

[jaz]

Haha, love the stock intake hose.

[kandykoated]

roll cages see the same stresses when crashed doesn't matter in what sport...

the way roll cages and frames in auto-x wrc nascar etc see stress is alot more different than you may think because thay are being pushed in more directions than one at any given time during a race, a drag car on the other hand 90% of the time sees it from a forward to back compression stress

the way a dragster is designed is the reason why they can use cromoly and no all roll cages do not see the same stresses from a crash when a car rolls doing 100mp ith is ALOT different than one flipping at 200+mph that is the reason why they use it for the simple fact of it being stronger this is why F1 race cars also use cromoly frames.

although on a drag racing team after each event the frames are measured from certain given points and if they have been tweeked over the maximum allowed tolerances than that team must produce a new frame for which to use in the next event, and if they do get into a wreck, hit a wall, rub the wall, or end up in the sand pit then that team must produce a new frame (obviously lol)

[corx]

almost nothing is cromoly on an f1 car. the chassis is carbon fiber and aluminum monocoque. it is made of sheeted materials not a cage.

differnt forces while racing produce differnt cages. rally cars are strengthend for torsional rigidity with guseted "x's", nascar has triple barrel cages for rubbing or hitting a wall, drag cars have cages made for weight transfer to the rear wheels.

thus, the materials are more a saftey/cost thing and the chassis design is more for the aplication.