No torsion bars? what holds the back of the lcr in?

thanks

Dude I don't mean to be rude but that's just flat out dangerous and should never be on the road( or track) Your going to kill yourself and/or someone else.
I understand your intent and desire and I applaud that but for starters that "steering arm" WILL fail and with catastrophic consequences. The "k-frame will flex and bend and break in short order too. Not to mention how it will steer even if it didn't break. PLEASE PLEASE PLEASE find someone with a lot of experience to help you with this before something very horrific happens.
Again your best interests are at heart here, not trying to rain on your parade or insult you in any way.

Looks alittle weak to me. Remember that the steerig arms/ball joints from the factory was made of forged steel.
Also the stock k-member have alot of flex going on and i cant see you made it better.
I always try to think triangulate when i fab stuff.
Need to think 3 dim.
Just my two cent.

Really awesome job, very impressed....Along with your Drag Week completion with a new engine...

Apparently most of you guy's have never looked at a strut steering system, 1/4" flat plate bolted on with 2 - 3/8 bolts. Never heard of one breaking.

I believe when using TB's, the K sees the weight from the motor, whether is on mounts or plate, but when going to coil overs, the k only sees the motor when on mounts, although on coilovers it does see a small %, depending motion ratio stuff.

Steff... on that PM.... strut rods also

Ok I'm not trying to stir the pot, but here is my two cents. Tried to explain it in the simplest way possible.

First, remember the old saying. "Every action has an equal and opposite reaction".

When the car brakes, nose dives, comes of a wheelie, etc... here is part of what happens.

First look at Figure "A" in the top left corner.

This is a section through the frame rail and rear attachment point of the K-member. Force #1 represents the weight of the car pushing down in the frame rail. Force #2 represents the force from the lower control arm holding the car up. In principal, this is what keeps the car "Up". You can see that these forces are not in line. What this means is that there will be a "twisting" of the frame rail.

Now look at Figure "B" at the bottom.

You can see the same Force #1 and Force #2. This results in the "twisting" that I was trying to simply explain in Figure A. The twisting is shown as Force #3.

So what counter acts the twisting of Force #3? It's safe to assume that most of Force #1 is also distributed through the front portion of the untouched K-frame. It is much larger/stronger then the rear square tube that was added.

As Force #3 twists up, it creates a Force #4 on the square tube. Force #4 and Force #1 (on the front of the K-Frame) are now "fighting" eachother to keep the car up. This is what normally happens with a stock K-frame.

But what you can envision, is that there is a huge mismatch of strength between the old front box section of the K-frame, and the new 1" square tube that has been added. The new square tube is clearly not as strong as the old boxed K-frame section.

To make things worse, the holes that are drilled for rack attachment bolts, is right through the worst part of the load path in the small square tube.

If Force #1 is hard enough, it will try to bend/break the new square tube because of the translated Force #4. This will most likely occur right at the rear hole that was drilled for fastener access to the rack attachment.

If it were mine, I would cut the square tubes off, replace with adequate size round tube, and weld tabs off the round tube to attach the rack. That way the tube is not compromised because of the rack attachment hole.

Just my opinion....but something to think about.

Good work Steve. I think, given the time and materials, you could/would build a functioning space shuttle. I really like the explaination given by Scott too. I thought I had some 1 1/4" .134 mild steel tube,... I DON'T. Anyway, it's good to see these ideas materialize. Hope to see you over the holidays.

I agree the added square tubing is imo also a problem area, the stress concentration on the mid angle welded joint is going to be rather high, and competing with the thru bolts for weakest area. I think it can be reinforced, or upgraded with a replacement, without starting over. I would not automatically suggest round tubing, as it's greatest strength attribute compared to equally sized square? tubing is torsional strength, and not sure that is a big concern on this support piece.

However the Op's point on the many over the years rather cut-up/butchered drag race k's for oil pan clearance makes for a rather compelling argument, although street/road vs drag are two different animals.

Steff I have been watching this thread and can relate, I'm in the middle of a K-member project myself for me and a couple of buddies a-body cars.

I would suggest you buy a caster camber gauge (if you don't have one) and set the caster/camber before you spend too much time on the bump steer and shape of the steering arms. It will make a difference, when you move the top of the spindle back it will raise the steering arm and vice versa.

Looks like it might work, My guess is that the bars where your rack are attached will flex and crack at the K-frame joint.

If it does, you will be moving your rack back and forth instead of your wheels.


Be careful.

I also built a K member with a rack for my Roadrunner.

...nice