dropped spring behind perch tab...to gusset or not to gusset

[alteredpilot]

so i got this pair of 'bones with a rolling chassis (gonna be a 27 ford roadster with a small block) i got. the tabs look to be in just the right place for my spring behind setup. the tab is .190(ish) and the boss is .500. do you think i should gusset or reinforce it and if so how?? thanks

[jub]

If it was me I would definately gusset

[Slag Kustom]

i would make a curved or angled plat to mount to the outer part of the bolt hole or cut a curved section out of an other wish bone to gusset it

[burger]

Look at the direct in which force will be applied. Your springs are going to try and push that tab up (BTW, it's suicidal as-is). Resist that force with a gusset that provides the greatest amount of strength in the direction of the applied force.

My design is not as pretty as what Slag has proposed, but form follows function.

[burger]

PS- All of the bending is going to want to occur at the weld between the existing tab and bone. Any gusset that does not securely connect to both pieces is a waste of time.

Also note that your gusset should be perpendicular to the existing tab. It's kinda like the straw example where you can easily bend it with a side load, but it's suprisingly strong along its axis.

[Unkl Ian]

Does that put the spring back far enough to clear the tierod,
or are you going to cheat and run the tie rod on front?

I like the way Eyeball did his: http://geocities.com/kustom1948/roadster4.html

[burger]

I like Eyeball's method better too, as it gives the bung more support. That being said, what you have will drop the car down low without the need for a tall suicide mount and should work well with some gusseting.

[SimonSez]

Pretty much all the times I've seen this done, the spring mount is around about the middle of the wishbone.

If you mount the spring on that tab, I think you will end up with all sorts of stuff hanging below your scrub line.

Mock it up first and see where the spring ends up.

[alteredpilot]

yeah i already mocked it up and the scrubline is not a problem. it puts the frame exactly where i want it with the wheels and tires i'm using.
okay now for the dummy question...should that gusset be to on the inside or outside?? the perch boss was oriented to the inside when i got the chassis. (think it was a shock mount) it would seem to me that the force would try to bend the tab out, and that a gusset on the outside would keep things in order. most of the tab drops ive seen have been gusseted on the inboard side.
anyway thanks for the input so far and for the diagrams, thats pretty much what i had in mind. any further insight is greatly appreciated.

[Unkl Ian]

Gussets are stronger in tension than compression.
Try and spread the stresses over as wide an area as possible.

[flt-blk]

You could gusset both sides.
If you only do one, I would suggest over the boss, that way
the top of the Boss is supported as well as the drop. Like edmurder's picture
TZ

[alteredpilot]

okay so the gusset goes on the inboard side. whaddya think about material thickness?? i know i want it as stout as possible, but i dont want it looking all beefed out if you know what i mean. am i better with one big 'ol piece of 3/8 straight up and down or two 1/4" going up at an angle parallel to the outer edge?? what say you??

[bigron]

it definelty needs some suport. i like edmurder's idea. it looks strong and still looks ok.

[burger]

What Unkl says about tension and compression is true and worth taking into conideration ...

However, I would make my decision based upon which side would provide the most area for the "legs" of the gusset.

Maybe do both sides? Overkill is better than getting killed.

As far as thickness of mat'l, 3/8 is overkill but I'd use it if I had it. Otherwise 1/4 will do you fine. I designed brackets to lift 6,000 pound pumps from two points using 1/4 plate. We haven't had a single problem in over a year's use.

[alteredpilot]

my intention was always to use the perch boss as the 'base' for the gusset, it was just a matter of orienting it inboard or outboard. whan i mocked it i had it inboard and it looked right. now with unklians input i'm going to go with something similar to the edmurder super gusset and put it in tension by orienting the perch and gusset to the inboard. thanks for the feedback guys!

[Unkl Ian]

1/4" would be plenty.
A simple triangle,run it up to the edge of the radius at the top,ike Edmurder showed.
Fillet weld all the way around.No undercutting,no stress risers.

Or you could use a piece of rectangle tubing,perhaps 3/4" x 1 1/2",to create a folded gusset.
Assuming the bushing is at least 3/4" od.That would spread the load over a larger area.

Are those 'bones chrome plated ?
If so,I would grind the chrome off in the area to be welded.

[DrJ]

That thing is a lever.
It looks to me like it's going to be a stress fracture about to happen no matter what you do to it.
The spring shackles are going to be constantly putting side loads on the "lever" and attempting to twist it off that tube. eventually it'll give, unless it's going on a lightweight car with no more sprung weight than unsprung weight on the front end, like a FED.

[alteredpilot]

okay howzabout something like this.....

[alteredpilot]

another view. this one is just a trial. i'll make the real deal fit tighter and i'll most likely grind the pointed end down to flow into the bone.

[flt-blk]

How about two of those, paralell to the edges of the bracket, in a "V".
That would take care of the side load from the spring movement too.

Now how about shackles. I have never seen a shackle that
was supported only with a pin sticking out. Maybe you
could use one of those that rotates to fix caster problems
and spring bind.
TZ

[Unkl Ian]

I'd make the hole a little smaller,but thats basicly the idea.

The more I think about it,the more I like the rectangle tube idea,
but either way should work just fine.

[Slag Kustom]

looks good but i like the idea of 2 of them on each edge of the tab just to be safe

[alteredpilot]

the more i'm looking at it, the more i think i'm gonna go with two in a 'v' configuration of some type. not sure if i want to make the point of the 'v' in the center of the pin boss or have them run down to the outer radius....

unklian could you elaborate on the rectangular tube idea? i'm having a hard time visualizing it.

as far as spring pivots are concerned, what i'm doing is using a set up similar to this....should be just what the doctor ordered...

[burger]

I don't see the need for two "vee" gussets. If you look at the picture below, I've drawn a green dot. Every force transmitted by the spring is going to try to rotate around that point. The blue rotations are going to work against the blue weld and the red rotations are going to work against the red weld. Everything looks good to me. Two gussets would work better, but one would provide ample support.

Also, those litening holes are too large. As a rule of thumb, you should have at least one half of the diamter in material between the edge of the hole and the edge of the material (i.e. a 1" holes should have at least 1/2 inch of metal around it).


Ed

[AHotRod]

Absolutley!

Chassis brackets are one of the things that most guys don't build strong enough.

[alteredpilot]

thanks for the illustration edmurder! that helped . the holes were just for effect. that was a rather crude test piece i made with a cutoff wheel and a bench grinder on a piece of old pitted plate we had laying around the shop, so the real deal will have the proper size holes. thanks again for all the input.