granatelli k-member

[billfisher]

ok so the welds are fine.

but there's one very small thing.......

they advertise that stock a-arms work with it. so i didnt buy any. they don't. i am cutting the spring perches out anyway, so they aren't really much heavier than tubular. i would have purchased them if i had known they aren't even close.

well its too late now. i want the car on the road tomorrow. so i cut the a-arm mounting points off and i am making some stainless replacements that will mount the factory a-arms AND return the wheelbase to factory.

otherwise i am satisfied with it. it mounted fine and all of the holes lined up.

 

[02nightmaregt]

Dude, you got skills. Glad to hear you got it all figured out. How do you like the Granitelli piece? Would YOU recommend it?

 

[blubullett]

Isnt most of the benefit of getting a granetelli the revised geometry It sounds like you are pretty handy with a welder, at least you can fix it when it breaks

 

[bdcardinal]

the benefit of the granatelli is that it will break and cause severe bodily injury to the driver. the point of the MM designed k-member that granatelli copied is increased wheel base which allows more positive caster and helps high speed stability.

 

[billfisher]

its not going to break.

i have 6 x 15" ---" 3" backspaced front runners. i cant afford more caster. they will hit the fender.

i adjusted them a little. instead of losing it all i just moved the front tire 1/2" back.

it may be a copy, but its a strong one. it only needs to handle 165/80 r-15's. not much force really.

i recommend it if you buy their a-arms of course. this would have been a 3 hour job.


i have 1 side of the brackets welded on, and the 2nd side brackets are cut out and i am tacking them in place. once they are aligned and have the ride height set, i'll finish them .

i am using 309 stainless 3/32" sticks with 60 amps. stainless brackets for the a-arms to mount to. stringered root and weaved cover pass. front and back plates are boxed and double welded.

 

[billfisher]

14 gauge stainless plates.

 

[geoffsgt]

How can you tell the welds are fine?

 

[billfisher]

i am a certified welder. they are fine.

 

[smokin00GT]

Aftermarket K members are a pain in the @ss! Nobody knows this better than me. I used a QA1, which totally didn't fit and was a piece of crap... then went with PA Performance. The second one fit ok, but in my opinion the car handled better with the stock one.

 

[geoffsgt]

Do you know if it was heat treated after the welds were made?

I'm not a certified welder or anything, but we do weld things at school for projects, and I've been told heat treating makes all the difference. Specifically, we were throwing some BS around the table about making an all aluminum chassis for our car, where we have used steel in the past. Someone said we would have to heat treat the entire thing after welding it, which we can't, because we don't have a big enough oven.

 

[billfisher]

welding on heat treated metal is fine. you can even rework it once before the metal crystalizes at the weld area. i am weldding after grinding the old weld out. what you cannot do is use acetylene for cutting or burning holes, as it will remove the heat treament and make the metal extemely weak, ie instead of 100.000psi it can go low as 30,000 or worse have a very hard surface that is glass hard and shatters on impact.

i doubt this is heat treated. this stuff doesn't require a lot of loading and mild steel is fine with enough thickness. i welded semi traler suspensions for 3 years and reworked them. those are all heat treated in the beam and axle.

when you consired the loading of one wheel say a good tire with traction at high speed, the loading at 1.0 g is still only the proportion of the weight over both tires depending on the sway bar/spring, etc. it wont get to the 60 percent of full front weight. for example ifi have a 3000 lb car with 56 percent up front, i get ~1600lbs. at 1 g both fornt tires are contributing to cornering. the outside can be taking no more than the weight of the car where the tire begins to break loose. i am sure there are fellow willing to calculate the actual number , but lets sat its 70 percent or 1100 lbs. that would be a car with little sway bar in it like mine. (the back tires take the cornering force in my car).

so if 1100 lbs / 2 bushings = 550 lbs. in a double shear setup 550lbs is not that much weight.


i guess the actual weight each wheel takes is less than that.
the k-member is using 16 gauge mild steel for the shackles, and i suspect most others are too.


with the front and rear pivot points well overlapped and welded there is lot of strength there for cornering.

 

[billfisher]

you dont have to heat treat an aluminum chasis or anything else after welding, with threads being the counter point. you can low temp Tig weld treads and remachine them.

 

[flstang65]

I REALLY need to learn to weld

 

[forum155pl]

I REALLY need to learn to weld

ahh welding is a piece of cake anyone can do it...


but you gotta be good to make em hold

 

[billfisher]

well it is all together. you talk about riding different. some things i cant explain. the ride height dropped 1". that doesnt make any sense.

it turns out my measurements didnt take out as much wheelbase as i thought. it still added some. the handling is much crisper. the manual steering feels like power. camber is the same pretty much. i'll have to adjust it a tiny bit. i run camber for lowering rolling resistance anyway. i just toe it in a bit for good treadwear. (relatively)

i did go over a few welds i found during the process. i think they were ok, but i added metal anyway. 309 SS makes for a tough and strong tensile weld.

 

[billfisher]

learning to weld like i do or other professionals takes training and years. as good as i see myself, my welding skills are a sad joke comared to a 15year boilermaker welder.