remember those tv ads showing the truck's suspension on a set of rollers bouncing it up and down? An independent suspension does just that, it moves up and down without the frame ( and body) moving up and down. That's what you want, and boxing the frame anchors that weight allowing the IFS/IRS to move instead. Confused?
__________________
"We are holding our own."--Ernest McSorley
The Good1948 F1: awaiting an S10 T5 tranny
The Bad1987 TC: awaiting funds for parts
And the Ugly1962 Fairlane: awaiting everything
so a frame rail that is 6" high will need nearly a 9" fishmouth ???
j
Yes. In fact, longer is better.
The idea here is to gradually transition the stiffness of the boxed area. The "wings" of the fishmouth have to gradually taper to do that, especially in steel, where the material modulus of elasticity is very high. I checked my "Manual of Structural Design and Engineering Solutions" book. The ratio actually calculates to 1.47 X 1 as a min. for 1018 steel.
While any fishmouth will be better than a straight cut, the 1-1/2:1 a good ratio.
__________________
Randy Jack 56 F100 Street Rod Daily Driver
Growing OLD is mandatory. Growing UP is optional. Inside every old guy is a younger guy wondering what the heck happened.
(Rough approximation of 20" long 6" tall frame section drawn in AutoCAD.)
__________________
Where's the cookies??
BACA, Central Oklahoma Chapter
No Child Deserves to Live in Fear.
1956 F-100 289 w/ 460 warming in the wings.
1999 ML-430 The only one that's bone stock.
1987 FXSTC 88 inch - too many mods to list.
2006 FLHXI - 95 inch Stage II
__________________
Where's the cookies??
BACA, Central Oklahoma Chapter
No Child Deserves to Live in Fear.
1956 F-100 289 w/ 460 warming in the wings.
1999 ML-430 The only one that's bone stock.
1987 FXSTC 88 inch - too many mods to list.
2006 FLHXI - 95 inch Stage II
I'm boxed back to the cab ...so basically you're looking at something like this... with 1/2" radii at each corner and at apex of mouth
pardon the crude quick paintshop crayon drawing
at the front I'm tied completely into the crossmember so there is no way there...
Thank's Guys!...This kinda reminds me of a class I slept-thru somewhere.....
I'm going to incorporate this Mod into my frame when the Cab comes back off, ..
BACAGrizz, Nice work! Good question , and Thank's again for stirring up the Grey-Matter!
I'm boxed back to the cab ...so basically you're looking at something like this... with 1/2" radii at each corner and at apex of mouth
pardon the crude quick paintshop crayon drawing
at the front I'm tied completely into the crossmember so there is no way there...
sound/look right ???
later,
John :0X06
Yes, John. That looks good.
Instead of cutting the fishmouth in the boxing plate you have, think about just welding in some tapered fingers to extend the box plate past the cab mount. That leaves you solid to the mount and lets any flex happen past it.
Either way will work, though.
__________________
Randy Jack 56 F100 Street Rod Daily Driver
Growing OLD is mandatory. Growing UP is optional. Inside every old guy is a younger guy wondering what the heck happened.
Join Our Site - Its free, quick and easy!
