Tube Frame Designs for Early Bronco

[theshadowknows]

Ok, I admit, I'm know early Bronco purist as I want to build a tube frame, fiberglass body early Bronco. I know of several companies that build early Bronco tube chassis, but BIG $$$$, at least more than I'm willing to part with at the present time. Besides, I have a 40x60 garage and all the welding and bending equipment I need, so why buy when I can build, only problem is I have no plans.

Does anyone know where I can lay my hands on a "non-proprietary" set of plans to build my own tube chassis that will accept a fiberglass (over even steel for that matter) body? I've looked on line and can't seem to find any such thing. Any help would be greatly appreciated. Again, my apologies to you purists, but I'm more interested in function over form. Thanks in advance for any information.

TJ

 

[70_Steve]

Does anyone know where I can lay my hands on a "non-proprietary" set of plans to build my own tube chassis that will accept a fiberglass (over even steel for that matter) body? I've looked on line and can't seem to find any such thing. Any help would be greatly appreciated.

N8's site has drawings that show the stock frame dimensions (frame-specs?.gif). If you're going to fit a Bronco body on it, I would think you'll need the body mounts in the correct place.

 

[JaxLax]

Get a hold on j.r. nice he's got a tubed frame on his bronco. it was also featured in Bronco Driver Issue...9 i beleive, there are some good pictures, but i bet that he has more somewhere...

 

[bsaunder]

There are a couple buildups of tube buggies with Bronco bodies on the Bfix site

 

[Dusty]

If you really want function over form, build the tube chassis to fit whatever drivetrain, suspension, wheelbase, center of gravity etc. that you want. Then skin it with Bronco panels after its built.

To build a tubular frame that matches the measurements of the stock frame and fits a stock replacement fiberglass body, in my opinion is a wasted opportunity to build something really special.

You said you wanted function over form. Then build it for function first.

Dusty

 

[theshadowknows]

Hadn't frankly thought about skinning a totally custom tube chassis, I can see how that could provide some real advantages. But that's really starting from scratch. I can fab up something with the best of them, but design engineering at that level is a little outside the scope of what I had in mind. If there some proven designs available out there, I'd love to get my hands on them. Most of the wheeling I do is pretty versatile, not just rock crawling, but tough truck and heavy trail action type stuff. I'm thinking a stroked 351 to keep weight down with a C6/NP205 combination, probably 39.5s, cut boggers in back and tried and true siped TSLs up front, 5.13s w/welded 70 out back and 60 up front. This is all stuff I pulled of my full size Bronco that I'd like to re-use. If I custom fab something out of tube stock, no reason I can't build it to use this stuff, right? Suspension geometry and articulation is where I need the help.

Thanks to everybody for all the resources.
TJ

 

[md_lucky_13]

I don't see any reason to use a totally tubular frame if you are going to try to use an entire body.

The advantages of building a rock buggy over an original framed rig are basically the care free "I roll it over and flip it back to the tires, no harm done" aspect of owning a buggy. You are basically nulling that by throwing an entire body over the top.

You can take a stock frame bronco and build one hell of a trail rig out of it, and you do not have to go totally tubular. Sure, a tube buggy offers more freedom when designing a 4 link suspension, and you can adjust anti-squat and all kinds of link triangulations better if you are running only tube, but the tried and true box frame offers several advantages.

For one, it gives you a flat surface to weld to. If you are not a serious fabricator that is comfortable welding the circumferance of pipe, then this can make a world of difference.

With a stock frame, the measurements are there. Other people have built 3-4 link suspension under the same platform, and there is a weath of knowledge out there. You ask a question, someone will probably have the answer. If you are going totally tubular, you can basically get a ton of web-wheelers to look at your design and tell you that you need to change it.. over and over and over and over.

If you try to stay close to street legal (many OHV parks are fairely easy on off-roaders, and will allow you to purchase a "truck" pass instead of an ATV pass) then the frame will have VIN numbers and what not.


Finnally, cost. Its much cheaper to use what you got, instead of trying to rebuild the Titanic. We have built everything from a toyota land cruiser with a mild lift, to a custom Cj-5 that was spring over with dana 44s and 36s (this was early 90s mind you, so it was pretty wild for its time) to my bronco (nothing extreme to todays standards, but was pretty wild a few years ago) and finally my step-dad's current bronco, with dana 60s, 38s, and basically everything you are talking about. All of these vehicles have used the stock frame, and they have been pleanty capible.

Here is a picture of the 4-link eliptic spring set up in his newest bronco. Stock frame, axle moved back some, but basically stock dimensions.. You could probably go a little more extreme with a tube frame.. But how often would you actually need more extreme, how well could you build it, and how much more would it cost?

 

[theshadowknows]

Hmmmmmm, very interesting thoughts. You're kind of bringing me back to where I started, which is full frame, traditional construction. I just recently switched over to a tube chassis way of thinking based on what I assumed were weight, cost, performance and strength advantages over stock frame or even aftermarket frame construction. But I haven't really done much research on cost of an aftermarket frame, or even building a full channeled "stock" frame out of rectangular tube stock. Definately want to reuse what I've got, just can't afford it any other way - the easy way out is just build another full size, but I'd like to switch over to something a little smaller, less footprint and more nimble with better articulation. I'm not into ramp competitions just want to thing to perform (function over form), and if I could get away with driving it on the street so I didn't HAVE to trailer it everywhere, that would be a big factor. Welding round stock is probably not anybody's favorite past time, including mine. I guess as far as structural integrity, rigidity and strength, a stock frame could be trussed so it has "cage-like" strength. I would assume there should be lots and lots of tech data on building a frame to spec. Awesome shot by the way, guess I'm not the only night owl.
TJ

 

[70_Steve]

This might be a good place to start.

http://classicbroncos.com/forums/showthread.php?s=&threadid=48893

Also, this thread will give you an idea of what can be done, starting with a stock frame.

http://classicbroncos.com/forums/showthread.php?s=&threadid=40738

 

[sstlaure]

Here's the "tube" chassis from my friends 68, the only thing original on the frame are the rails & cross-members, everything in the suspension is custom 4-link front/rear

 

[theshadowknows]

HOLY SH_T, NOW THATS WHAT I'M TALKIN 'BOUT!!!! I WANT ONE OF THOSE. GETTING ANY DONATIONS?

 

[j.r.nice]

If you really want function over form, build the tube chassis to fit whatever drivetrain, suspension, wheelbase, center of gravity etc. that you want. Then skin it with Bronco panels after its built.

To build a tubular frame that matches the measurements of the stock frame and fits a stock replacement fiberglass body, in my opinion is a wasted opportunity to build something really special.

You said you wanted function over form. Then build it for function first.

Dusty

....gee.....I'm not really sure how to take this. I dont necessarily disagree with your suggestions.

If you (generic) want a rock crawler, then build one a dedicated one. That way, you can hang any body panels available; make your own; leave them off, modify existing, whatever. Doesnt even have to be a Bronco.
If you want a trail rig - build one for that. All the goodies.....on board air, welder, winch, invertor, etc., etc. (kinda like Crazy Horse). That's also very appealing. In that case, it's probably best to stay with a full steel or f/g body (protection from the elements) and stay within the confines of a mfg conventional frame build and body. Maybe bolster the rollcage a little. Plenty of those on this site too, and VERY nice ones that I would be proud to own.

Also .....if I may quote md_lucky_13 ... "I don't see any reason to use a totally tubular frame if you are going to try to use an entire body. "

"The advantages of building a rock buggy over an original framed rig are basically the care free "I roll it over and flip it back to the tires, no harm done" aspect of owning a buggy. You are basically nulling that by throwing an entire body over the top."

I agree with part of that. If you are going to beat one over the rocks. flip it, roll it, scrape, scratch it, dent, abuse - then the buggy is the way to go.....or even a modified original frame.

Where you (generic) get into trouble is trying to build one for double duty and serve as a daily driver......or even street legal. It's nothing but compromise and doesnt serve either as well as it could.

What I disagree with is the opinion that building a totally tube frame within the confines of a Bronco Body is a waste or a missed opportunity to build something "special".


I dont consider what I did with mine a lost opportunity to do anything.

The guy who built my chassis is a certified, well-known, well respected chassis builder in the mud (NMRO)/sand/asphalt drag arena. I wanted light weight, strong and safe. I got that. I didn't forego anything by having it built to welcome the Bronco body.

I wasnt building a rock crawler. (matter of fact - I very quickly point out the limitations of the chassis to viewers). When I contracted to have this built, it wasnt even a consideration.

I wasnt building the ultimate off-road trail ride. Again, similar limitations. I am sure that this chassis would probably handle much larger tires, affording me much more ground clearance.
A blower and carb are not the best configuration on the trail.
I'm sure it WOULD (with some minor modifications, blow through the desert pretty well.

I wasn't building a trailer queen/show truck - inspite of my "Trailer Special" insignia on the glovebox. I drive this truck. No, not 400 miles, as I have done before. Sure I show it, but I prefer to drive it. Is it the ultimate "cruiser"?.....no hardly.
Is it the national record holder for pro-street Bronco's ?....again, "no".

I built this truck to be a 4130 Chromoly blown bullet-proof street Bronco. Is it fun? YES! IS it fast? YES. Is it what I wanted? YES.
Is it for everybody? ...should everybody build a tube frame Bronco? NO

But I did, I am happy with it (absent some minor bugs) and it has held up under some pretty tough testing........

Also, I was told by the builder, that anytime, if and when I decided to sell the chassis, he had buyers in line.
mud racers as well as tough truck. The builder wanted to design the chassis around a "gutted" rear end (no floor). I wanted a street legal truck, protected from the elements (mud - if I so choose!) so I vetoed the idea.

I think you all gave him some pretty good advise and took him down the path when he wants/needs to go. I just dont agree with your opinions on the use of a tube chassis.
my .02

J. R.

 

[schaan]

hey great thread

i very much want to build a lightweight tube or partial tube rig. keep this thread going.

 

[j.r.nice]

If there is anything I can add, I will be glad to jump in.

J. R.

 

[schaan]

ok heres my vision for spring 05

partial or tube frame incorporating an eb vin. big gun 35 spline dana 44/60 spliced , rear Heavy Duty housing and 35 spline 9" with full spool / 4.56 alloy axles and trussed ( lightly ) .
i just bought a hail damaged 1994 Ultra Park Avenue with the 3.8 litre ( eaton ) supercharger and i want to use a c4 ( built right ) connected to a cold duck ( if i can ever get the parts i need, ill build it myself, please WH !!!!!!! make the cold duck happen ! ) .
i can not go fullsize , if only because i think light is not only the answer but eventually will be the only way,unless you dont concentrate on wheeling, and to prove to the rest of the club that im not crazy! wheel base around 105 and very small if not negative approach and departure angles.
four link with as many heavy parts lowered and centered in relation to the vertical center of gravity and as much travel as i can get without going coil over.

btw how bout a 84 380 sel with rear airbags for a tow rig ?

 

[theshadowknows]

Sounds like this a topic of great interest to more than just myself, and I'm glad for all the great advice and opinions. To simplify, I'm looking for the hardest thing to achieve in engineering, and that's simplicity combined with a high performing, functional, multi-use vehicle. Complex solutions to complex problems, from a system engineering perspective is the path of the least resistance - it's always tougher to implement a simple solution. It's the whole "NASA spent a million dollars to develop a pen that would write in space, and the Soviets sent a pencil" example.

To keep things in perspective (at least my perspective), I've got a kid in college, another one that'll start in two years, child support from a previous mistake, a new house, and new house for my wife because we work four hours apart and only see each other on the weekends, just had a neck operation, etc., etc.; starting to get the picture. By default, a highly specialized vehicle; that is one for the trail, one for street, one for rock crawlin, etc., would be very cool, but at the present time I can only afford the time and money to build ONE vehilce. That vehicle needs to be durable enough to roll over on the trail and still streetable enough take downtown, weather-tight in a thunderstorm, and it wouldn't hurt if it was easy on the eyes. It needs to be buildable by a guy with average or better welding and fabrication skills in a home garage (of course once all those big sponsorship checks start rolling in, anyday now, all that will change).

In all seriousness, I need something, be it full frame, all tube, or a combination of the two that is functional in most environments, probably not the BEST in any one area, but respectable and affordable in most or all. I would love to be able to take this vehicle to the drag strip on Saturday, the trail on Sunday and work on Monday. There has to be a solution out there, other than that ultimate chrome moly, four link, powder coated, cryogenically treated, forged, extruded and stress-relieved magazine fantasy that the guys like me can build and enjoy. Having laid it out that way, I'm inclined to believe that maybe a full (stock) frame with a tube cage combination that takes advantage of the engine, drive train and axles I already have might be the way to go. This is definately a study in specialization and cost Vs performance and practicality. Someday, BELIEVE ME, I would love to have any of the vehicle above, and their owners should absolutely be justifiably proud of them, I sure as hell would if it were me, but till then, compromise is the only option a guy like me has got. So wadda ya think?

 

[Tazz]

Seeing how my thread was posted here I'll wade in.

For the first question Shadow asked, if all you want to do is build a tube frame that mimics a stock one, because you have the tools and time go for it. It would be easy enough to detail a set of plans off of an existing frame to build one from.

There are a couple of spots on the web where frame dimensions are posted. Do a search, they'll show up. I found a set, can't remember where but I'll check and see if I can find the link. If not, I know I have a set on my work computer and could post them.

Nothing is a waste of time if you want to do it. Everyone has an opinion, take most of them with a grain of salt. I usually keep mine to myself.

As for building a full tube rig and hanging skins on it, it does take some work, especially if you do it all yourself. I retained a portion of the frame and the fire wall for no more reason than to keep the vin #’s in place. It may be semantics, but both my insurance agent and my attorney felt that it a good idea. It will be licensed and insured and driven on the street at times.

When I finish mine, I plan on taking all of the pics from the thread my plans, notes, mistakes and doing a right up.

Schaan if there is anything I can help you with when you do yours, ask away I help if I can.

 

[j.r.nice]

I think it's a little clearer in my mind what you're after. Let me see if I can say it right.
Although a tube chassis looks neat, unless there is something you want that just can't be added to a stock rectangular frame, it might not net you much. A structurally sound design built out of mild steel would probably not save that much weight.
As a point of reference, the front half of my old Smittybuilt roll cage (the front 4 points at your feet and behind the seats) weighed more than my new complete 6 point 4130 cage. You can use your imagination on the rest of it.

On the other hand, if you are serious about the dragstrip comment, you'll have to have serious hp to make up for all the extra weight added with hoops and tubes, transfer case, extra axle and driveshaft, and big tires. You can EASILY add 350 lbs just in wheels and tires. 4wd vehicles are pretty expensive to setup to withstand dragrace torture.

Similarly, the f/g body doesnt really save much over a steel one. It's just a lot easier to replace the old rusty tub with a f/g one. This is also subject to debate. The beauty of a f/g body over a steel is the finish. I've had my f/g body for 12+ years. At the suggestion of the body shop owner where I did the swap, I left it gel coated. It is easy to clean, holds up well to moderate abuse and still looks good. I sanded and buffed mine.


If you want to try to make a "universal" Bronco you might have to make removable panels to jettison weight. (100 lbs = approx .1 of a sec at the track!). ...then put them back for street use. Although pratically speaking most of the weight wont be in the body. An Atlas transfer case is about 125lbs..... A C-6/AOD can't be far behind. (ask my back!) An EB in standard trim weighs in around 3900 give or take depending on year and equipment. That's pretty heavy, I was surprised the first time I put my 77 on the scales. A newer one is closer to 4850.

As far as trail, it's hard to beat a slightly warmed up Bronco no matter what. I would guess that unless you're doing extreme off-roading a std. frame would be adequate.

As far as using the stock frame, it is easier to register and insure. A tube chassis is a pain in that regard. What makes all the headaches worthwhile is the freedom to remove the smog stuff and thumb my nose at some DMV regs.

just offered for your consideration.....

J. R.

 

[sstlaure]

The stock EB frame is a great starting point. The main problems we encountered with the build-up of the "green machine" were in stretching the wheelbase (clearance to the oil pan at full compression in the front, and clearance to the rear cross-member for rear axle position. You can get awesome performance if you take your time and lay your project out (CAD helps, but we did this one on graph paper.) Long travel will also get you bump steer (not good) we went full hydraulic to eliminate this. The "conversion" from Bronco suspension to this one was ~$30K, built with all of the best parts.

This truck used coil-overs & 4-links, but the one I'm building (see 74 EB Sandrunner under development thread under my ID) will still be using coils/leaves & King Bypass shocks

 

[j.r.nice]

...ever put that on the scales? I'd be curious......

how much travel do you have in the front axle?

does he street drive that? .....and is hydrosteer street legal.

I was told it was not (cant remember if it was in VA or OH)