My version of a inner fender support/front subframe stiffener

[inkjunkie]

Pretty sure that in the Mopar chassis manual that there is a sketch of where the car should be tied together, for drag strip use at least. And if I remember right a pretty much standard snout bar is drawn in, tied into the interior cage, thru the firewall, top shock mount tied in and then onward to the front of the car. Maybe the Mopar engineers were wrong??

 

[HemiDenny]

its called U-N-I-B-O-D-Y...and it ain't a bad concept

 

[HemiDenny]

but...as I mentioned...FOR DRAG RACERS...it is an excellant idea

but for $hit and get...they work great...and I still think if they flexed as much as you believe...they would have folded up a long time ago

 

[72bluNblu]

Pretty sure that in the Mopar chassis manual that there is a sketch of where the car should be tied together, for drag strip use at least. And if I remember right a pretty much standard snout bar is drawn in, tied into the interior cage, thru the firewall, top shock mount tied in and then onward to the front of the car. Maybe the Mopar engineers were wrong??

Its all about where you tie it in. If you're tying into the interior cage and firewall, that's pretty high up. Traveling from the upper firewall and interior cage down through the upper shock mount and down the front of the frame rail does an excellent job of triangulating the front end. Curly's bar ties in low, so, it doesn't do as much to add strength.

its called U-N-I-B-O-D-Y...and it ain't a bad concept

Not a bad concept at all. Modern F1 cars are all monocoque construction, not a far cry from unibody construction at all.

But, Ma Mopar didn't execute the concept nearly as well as modern F1 cars. It was intended to be a fast, cheap, and lightweight way to produce cars, and it was/is. But the original unibody's were anything but rigid, flex all over the place. And while that makes for a nice, plush ride, it also makes for crappy handling. Also keep in mind that what works for drag racing is a long way from what works best for road handling, in a drag setting the flex in the front end is pretty much irrelevant.

 

[HemiDenny]

There's definitely flex in the front end, there's no doubt about that. The frames on these cars are nothing more than formed 14 gauge sheet metal, so yeah, there's flex.Twist is probably a bigger issue than plain vertical flex, but its still there.

As far as "high strength steel", that's a joke right? Literally, the frames of these cars are made out of 14 gauge sheet metal. It's doubled up in a few places (near the bumper mounts), but thats it. It's just mild steel sheetmetal, there's absolutely nothing "high strength" about it. Welding to it will have no dire consequences, no carbon migration, heat quench issues, etc.

As far as the inner fender support goes, I like the look of it and how it conforms to the body panels. That said, I think its too much tubing and not enough contact points with the original frame. The length of the tubing will allow it to flex as well, and without more tie-ins with the original structure it may deflect more than you think. I'm not saying that it wouldn't help, but I think inner fender braces like the ones XV sells would actually help more (firewall to upper shock support only). Its a short piece of tubing, so less flex in it, and it makes a decent box out of the shock mount and fire wall to stiffen the frame below. Of course, you still need to box the upper shock mount to make it work well.

When you think about stiffening chassis, you have to think about making "boxes". With a connector running from the upper shock mount to the firewall, you're not just adding the brace, but also a moment arm- the vertical distance from the upper shock mount and the frame and the firewall and the frame. That parallel link makes a box that significantly strengthens the frame rail's bending moment. The long tube that you've made still attaches low on the frame, so, you're not getting additional strength from the boxing of the framerail, just the additional strength of the tubing itself. Now, if you used a plate to weld it into the frame structure where it passes through that lower hole,and tied it into the firewall at the top of the bend with an additional section of tube and anchor plate, you'd have a pretty strong brace.

i definately agree with the twisting from torque can be more of an issue....but that takes some HP and a good tire...even with good HP , without adequate suspension/tire combo....all you get is the spin cycle

I do think they flex...almost anything does...I just do not think they do to the extent (on non lethal drag cars) that has been projected.

just my view...and as a discloser...I have never received any intelligance awards...might have got a 'honorable mention" way back when though

 

[72bluNblu]

i definately agree with the twisting from torque can be more of an issue....but that takes some HP and a good tire...even with good HP and not adequate suspension/tire combo....all you get is the spin cycle

Its not just twisting from torque though. In a handling setting, you're going to get a bunch of twist from suspension and cornering loads. With modern tires, you can actually load up to around 1 lateral G with the right set up. That's more twist than engine torque is going to give you.

Here's pictures of a couple of braces. This one is on an A-body, the brace is made by Magnumforce. It ties the upper firewall, upper shock mount, and front frame together (the brace keeps going forward and down to the top of the front frame rail). This is probably one of the strongest ways to do this. And, because their coilover set up loads the upper shock mount, its also pretty important for their tubular K member/coilover conversion.

This is a B body, but you get the idea. XV's inner fender brace. Notice the inner fender well has been seam welded to the shock mount, reinforcing it. The short length of tube will be pretty inflexible, but it still relies partially on the integrity of the upper shock mount a lot for the strength of the brace. Not as strong as the Magnumforce brace (tied into 3 places instead of 2), but a nice addition none the less. And, out of sight and not competing for engine bay room.

Now, Curly's brace.

The biggest issues here are that is ties in low on the frame in the back, and on the side of the frame in the front. Tying into the top of the frame would be stronger, as the frame would push directly into the brace (like on the Magnumforce brace). Also, there's really no reason to run parallel right next to the frame in the back. That part of the frame is already strong, and would be better off just boxed in with torque boxes. Tied in high to the firewall at the back, and welded onto the top of the front frame, it would be pretty similar to the Magnumforce brace, without the hassle of it being entirely in the engine compartment.

I'd keep the brace going straight back from the upper shock mount back to the firewall to an anchor plate, and then bend it to follow the inner fender in the front, then take it through the inner fender and tie into the top of the frame rail above the front K member mount.

 

[ardentindustries]

All excellent info here. Maybe I should start building random pieces to spark up good quality conversation on the forums every now and then. I totally understand the points being address. I thought about adding an additional piece of tubing, tieing this to the firewall, as far towards the outside of the car as possible.
After reading the discussions...it seems there may not be a need to reinvent the wheel for everything thats already available. Personally, I HATE the idea of simply copying something that is already being produced...but maybe that is the way to go here. The XV braces would be MUCH easier to make than the piece I have pictured. Like I said, I guess I didnt want to look like a copy cat...thats all.
Maybe I'll work on some bars similar to the XV stuff...Im really not sure how much interest there is in this stuff, but we'll see. I would think only this with a car not yet painted would be interested, but I could be wrong.
Thanks to everyone for the input! Nothing better on the internet than good, educational conversation.
HemiDenny...spill the beans. You often mention something along the lines of "Im no expert, but..." so whats your past history? Just curious.

 

[HemiDenny]

sorry...but I wouldn't put that Magnum Force brace on my lawnmower...I think if it is just plated and tied to the sheetmetal firewall...well, lets just say there are better ways.....now...if you tied it to a roll cage, you would have something. But then you better have some hefty HP..and were not talking "street car"...so I guess we are back to the start

 

[inkjunkie]

Granted it is an E-body but if you click on the video link here looks like there is a crap load of flexing going on.......unless that is my imagination as well.....

 

[HemiDenny]

HemiDenny...spill the beans. You often mention something along the lines of "Im no expert, but..." so whats your past history? Just curious.

usually I leave off the ..but...part.....but,I do talk a good game...so I'm told

I'm just a hot rodder...the pics on my posts tell the short version...

the Duster with the "Missle" scheme is from the mid 70's...it had a high revin 383/4-speed/dana ....right out of high school

the green Duster in the middle was my first Hemi/A-body build...around 1995

the silver Duster is my latest build ....all aluminum Hemi/aluminum passon 833 w/gear vendor and 4-bar/4-link ...just my coffee getter

also designed and built several other magazine featured Hemi A bodies...HemiMarks 528 orange Duster w/ Dana 60 and Keisler 5 speed and Jims butterscotch Hemi Demon complete with auto column shift and A/C

thanks for askin...never get tired of talkin about myself
Denny

 

[72bluNblu]

sorry...but I wouldn't put that Magnum Force brace on my lawnmower...I think if it is just plated and tied to the sheetmetal firewall...well, lets just say there are better ways.....now...if you tied it to a roll cage, you might have something. But then you better have some hefty HP..and were not talking "street car"...so I guess we are back to the start

It would definitely be stronger tied into a roll cage. But, if its plated well to the firewall, it does a lot to strengthen the front then. The front frame rails on these cars are basically just cantilevered off of the body, there's nothing other than a flimsy stamped sheet metal brace from the shock mount to the firewall to resist upward bending at all. Because the Magnuforce brace is tied in high,and near the corner of the firewall (also near the reinforced A pillar), it will actually resist bending pretty well. Not every car needs a cage, but why do you need "hefty HP" to want your car to plant all 4 corners without tying itself in a knot? Modern tire compounds are a whole different world from the tires that were out there when these cars were designed, you didn't need a stout frame because the tires would let go long before they started to stress the frame/body. Not so anymore, with 1" torsion bars, better shocks and wider tires, the flex in the body is an issue. In a drag race setting, with the rear tires hooking and twisting the car, you're reinforcing the frame to try and keep the BACK of the car from twisting. The front of the car flexing up and down is a non issue in a drag setting, as long as it doesn't flex so much side-to-side that you can't keep it off the rails you're good.

Granted it is an E-body but if you click on the video link here looks like there is a crap load of flexing going on.......unless that is my imagination as well.....

I think their method highlights what they did to the car (and why wouldn't it, they're trying to sell a product), but it definitely shows that these cars do flex quite a bit...

 

[HemiDenny]

Granted it is an E-body but if you click on the video link here looks like there is a crap load of flexing going on.......unless that is my imagination as well.....

couldn't find a video link.....got a link to their web site though

maybe it was just my imagination....slipping away (that would make a great song..eh???)

 

[HemiDenny]

Sorry...Mom says I have to put the computer down and hit the rack

but I'll be back to play in the morning....don't go away....this is fun!

 

[memike]

strength for sure :cheers:, I like :toothy2: Subscribed.

 

[Badart]

The only problem I see with the magnum force setup is the landing that comes down to the shock mount. If you look at your A body there is a good 1/4"-3/8" gap between the sheet metal and the factory shock tower bracing. If you ask me that area should be removed like purplehaze did in his thread and welded solid to the factory bracing.

 

[Mad Dart]

Just a thought to the Magnum Force version. There could be a Spacer or Plate that drops into the gapped area between the inner fender and the upper shock tower to "Sandwich" or take up that gapped area. It would tie all together with the Coil Over shock conversion mount and "Sandwich" everything together. This way you would not need to cut into the inner fender.

I myself would do it like Purple Haze did it but some guys are afraid when it comes to welding and cutting on their cars.

Someone could even offer a Bolt in Kit like the Magnum Force. Using Plates that bolt through the firewall again "Sandwiching" with a plate on the back side. Same thing at the front of the frame rail. Just another thought for the guys that do not have the capability of doing the weld in version or don't want to weld on their cars. So this version would have 3 areas where it is "Sandwiched" and Bolted.

1) The shock tower with a Spacer to take up the gap
2) At the upper cowl area of the firewall
3) At the front frame rail

 

[HemiDenny]

so let's just say...I got 800HP (like most of us around here).....and can yank the front wheels on a good launch, or I live and cruise a lot in Michigan (sorry) home of the "pothole" tour.....what do you think is gonna happen to my cowl , (ya know...where all that strong glass is) where the Magnum Force snout bars are attached...not to a cage...but to that single layer of 14 ga?

it is about the LAST place I want anything pulling or pushing on...not just for the possiblilty of cracking/ripping out....but that area is not an area on my car I want stress.....gotta be a better way.

the XV motorsport brace inside the engine bay..I really like...if it was invisible. I just like the look of the 70's Mopar muscle car engine bay but if I was road racing...I would have a version of it (XV is a little pricy for me, but I'm cost conscious...read: cheap sucker.)

but back to my original comment

these unibody cars have some minor flex...but when you are putting them on jackstands...and the front end is dropping as you let it down....it is because the car is pivoting on the jackstands and the rear is rising. NOT because it is flexing a couple of inches

while the discussion on snout bars is great too....I've already seen that movie.

Mopar to you boyz,
Denny

 

[Mad Dart]

Snout bars to the cage inside the car is always the best option. I myself will be attaching mine to the cage, however there is no room left under my hood so they will be underneath the inner fender in the fender well.

 

[HemiDenny]

still...I luv this forum and all the different threads here...it's like the ol' days.....hangin round the garage/race shop and BS'n

everybodys got different ideas and were never shy about lay'n 'em out....never had any hurt feelings....once in a while if someone got their panties in a wad...we would handle it like the men we are.....wait 'till they went in the can...and slide a lit bottlerocket under the door!

that brought everybody back to "reality"

 

[inkjunkie]

We used cherry bombs just outside the door.....

 

[HemiDenny]

good one.......nothin like an attenton getter to break the tension

 

[inkjunkie]

good one...but some of my buddies farts were that loud....

Flatulence maximus.............

 

[Mad Dart]

A seal bomb always does the trick.:toothy3:

 

[pishta]

I like it. Ive been looking for J bars for a while as I have no iners in my 65 and when I drilled the last 2 spot welds on those, it made a pop that I wasnt expecting, so there is a load on these inners. I trimmed a section out of one shock mount so a header would clear and it had some serious flex in it. I watched it move 2-3mm when I rocked the front fender. after rewelding the box shape back, it was steady but if you run a stiff shock, these are going to flex a little without an inner to help support them. If you deleted the stock perch, ran these with a shock tab welded in and tied the tops together with a bolt on "Monte Carlo" bar across the motor...? Mustangs, especially the big blocks would flex big time without these, but they used the towers as suspension points.