Frame Ties 101

Duke5A

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My father and I ended up building a set of frame ties today for a friend and took photos. This set was for a Diplomat sedan. The point of this thread really isn't to show exact measurements, but to give a sense of what is involved with making a pair.

...and yes, I know the 'preferred' method is to install through the floorboard, but come on, that is overkill for anything short of a track car.

This set ties the front and rear sub frames together by tucking under the floorboard. For these you would probably have to make some clearances in the seatbelt support brackets under the car.

For installation the front is welded around the angle iron and back slips under the rear frame conforming to it. To get the shape right on the back a cardboard template was made.

Material:
  • 2" x 2" box tube, 1/8" wall
  • 2" x 2" angle iron
  • bits of flat stock scrap for caps
Tools used:
  • DC stick welder
  • 6" angle grinder with grinding wheels
  • Jet horizontal/vertical metal bandsaw

A shielded wire mig welder would have been more preferable, but we work with what we have.

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toolmanmike

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Nicely done. When you get the install done and posted I can make it a sticky.
 

Camtron

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Awesome and quick solution. Pretty dang affordable too. Are you guys welding along the bottom where it contacts the floor pan or just at the little frame rail sections?
This is for sure on my “todo list”.
 

Duke5A

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Nicely done. When you get the install done and posted I can make it a sticky.

Thank you! Unfortunately I won't be the one doing the final installation. These are being boxed up and shipped out of state. I'm new owner will take plenty of photos though.
 

LSM360

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Well, easy is easy for some of you to say, lol. Not easy for ME to make them. I am very impressed with his skills in both fabrication and the welds.
 

Camtron

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One mans scrap is another mans frame ties, lol. Hopefully, I’ll have these done and welded onto the car next weekend...maybe I’ll even post the measurements when I’m done, lol.

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XfbodyX

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Alot of good fab work going on here. In the interest of weight, profile, stealthiness? Ive always wondered if some have asked themselves these things and what there conclusion was?

1 What exactly are we trying to achieve?
2 What is the minimum proven or disproved requirements to be successful at tying a FMJ car together?
3 What are the shear characteristics of horizontal vs vertical welds?

I could probably make the list long but these are a few of the main things some may wonder.

Since some use bigger material and some smaller, is there a std. and what sets that standard and what are those standards based on?
 

LSM360

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1 Stop any twist in floor or roof when having significantly raised engine torque (and bonus of tightening entire car)
2 I can't really answer this, not enough sample size. Duke's choice of 2x2 and 1/8 seems a perfect balance between weight and
strength (seems to be a popular choice from what of read) for street car.
3 Not enough knowledge for me to answer. But for street use only, I love what Duke has made!

Stealthiness, I'll paint them black. Show a little? It's fine.
 

Camtron

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Keep the frame from twisting. Even the stock roller 318 in the car now, it makes enough power to feel the frame twist with a hard launch from a dead stop. Will be undoubtably worse when I put the 5.9 magnum in the car.
The 1/8 thickness of the angle iron and box tube is more than enough strength wise without adding too much unnecessary weight.
From what I can tell the unibody/frame rails look to be 1/8” also, so you can easily get full penetration through both the frame ties and unibody for solid welds.
As far as the horizontal vs vertical welds, can’t see it making too much a difference in this application. It’s all little fillet welds as far as I can work out in my head. Pretty typical and strong weld even in structural welding, but if you have a shit weld, fillet welds almost always break through the throat (length) of the weld. Should be able to put welds all the way around the ends of both of the frame ties, so, shearing shouldn’t be much of and issue since the load/force is twisting more than shearing anyway.
 

kkritsilas

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I'm following this with interest, and I am neither a welder or a fabricator (nor do I play one on TV), so I am going to ask a possibly dumb question.

Should the frame ties be triangulated where they meet the frame rails? Don't 90 degree joints tend to break more? Or is this not an application where the forces involved are not such that this will be an issue?
 

Camtron

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I don’t know what you mean by, should the connectors be triangulated where they meet the frame rails. Could cut some triangle braces from 1/8” steel and weld them off the side of the connectors to the floor pan, that would definitely add some extra strength/rigidity.
I don’t see an issue with what, Duke5A has put together for a typical street car. Welds around the box tube will hold up just fine.
Only way I see anyone running into problems with this particular method is,
frame rails being too rusty, that could lead to some issues pretty quickly...weak welds at best, metal disintegrates when you try to weld on it at worst. The second issue would be making too much power (which most people on here aren’t close to) combined with weak/rusty metal and welds and twisting the car hard enough to break all the welds on one end or more of your connectors...but if your cars makes that kinda power, you probably already know these aren’t the sub frame connectors you’re looking for, lol.
 

Duke5A

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The point is chassis stiffening. Ever put jack stands under the front frame rails and watch the whole front end sag when lowering the jack? Open the driver's door with the front end on stands? Feel the car twist with even so little as 250 ft/lbs of torque? Put in cop sway bars and still wonder why it feels like a wet noodle on the open road? Fact is the unibody on these cars was never rigid and 35 years of age hasn't helped.

When I installed mine I had already rebuilt the front and rear suspension with factory police bars. The difference is handling was day and night. The car tracked truer and the doors open/closed like they should even with the front end in the air.

There are plenty of ways to do them with different material dimensions and install methods. Through the floor is best, but overkill for street applications. I would only entertain a through floor install if I already had the interior ripped out or I was planning on installing a cage for drag racing.

Bottom line is the frame rails should have run the entire length of the car from the factory on everything. The rocker panels themselves weren't enough to brace the center section of the car. As far as I'm concerned this is fixing a design flaw most likely introduced by a bean counter.
 
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