front tube chassis

[CableSrv]

I've done alot of searching and still haven't found much answers...

 

first I just ordered myself a miller 140 and it should be here sometime next week. now I'm kinda curious as to what I can get away with using that welder. I know that it can handle cage building but my big question is can it handle welding a front tube chassis?

 

everyone that I've read that has done a front tube chassis uses chromoly and tig.. can it be done using normal structural tubing and mig tho? another thing.. what is the difference between erw and dom tubing ? I can't really find any info on these types of tubing or whatnot.

 

would a harbor freight 6ton tub bender work for doing this type of job? or would you suggest something else? I'm trying to go the relativly cheap route mind you, and don't have a billion dollars to spend on super mega take over the world type equipment.

 

If any of you guys could point me in the right direction on stuff to read up on I'd be gratefull.

 

Besides the welding info my next big question is of course once I build a jig for the car to be put on and chopping the front off. Besides making a new front lower frame for the crossmember to attach to, what parts on the firewall are good to weld against for extra strenght ?

[JustinOlson]

Are you planning on caging the car, or just doing the tube fron end?

 

Justin

[CableSrv]

probably both, but i don't want a FULL cage. This isn't being built for serious racing or anything. This is just a project for me to learn on and to have fun.

 

My reasoning on the tube chassis is, from what I've seen from others, means alot more strength tieing the engine & suspension to the body as well as alot more room to work with on working on the vehical. Yea I know that's alot more work required to do something of this sort, but I take this as a good chance to learn alot about my car and welding techniques.

[Pop N Wood]

chromoly is stronger than mild steel. It use to be if you used chromoly some racing bodies would let you use thinner tubing. This saved weight. But I thought I read on here that some places no longer make a distinction between chromoly and steel. At that point I personally would chose steel since it is cheaper and welds easily.

 

ERW = electron resistance welded (I think) where as DOM = drawn over metal. Basically you want a type of tubing that doesn't have a bad seam that will split should the car get in a wreck. DOM is formed through some type of mandarel so there is no seam. ERW is a type of welding that forms a very consistent and strong seam.

 

You can also weld chromoly with a torch. Some feel it actually makes a stronger weld than TIG.

 

You don't want the harbor freight tubing bender. Do a search. Jon Mortenson in particular has posted his experience that bender. There are things you can do to make it work better, but it still is less than satisfying.

[johnc]

ERW tubing that you and I can buy is made from 1010 steel and has a tensile strength of 58ksi and a yield strength of 40ksi. DOM tubing is typically made from 1020 steel and has a tensile strength of 80ksi and a yield strength of 65ksi.

 

ERW tubing is made by taking flat stock, rolling it, and welding the seam. You can readily identify ERW tubing by the blue/black stripe on the outside and the raised ridge on the inside. Its the cheapest way to make tubing.

 

DOM tubing is made by taking flat stock, rolling it, welding the seam, and then drawing the tube repeatedly over a mandrel, cold working the material. This cold working improves dimensional tolerances and increases the strength of the tubing. Because DOM has a price premium over ERW it is typically made using a higher quality flat stock.

 

And yes, you can make your tubular front structure using DOM. All NASCAR chassis are made using DOM.

[CableSrv]

So erw type tubing is not something you'd want for a front tube chassis? Is DOM tubing easily mig'able? or is there something I should know before attemting to mig weld dom tubing?

[JMortensen]

DOM is mild steel so you don't have to do anything special. Welds just fine with my MM135.

[CableSrv]

sweet thanks!!! now to figure out a good bender for that tubing..

 

Pop I do remember reading those threads, and how someone used 2 threaded couplers to help aid the bender but from what I remember that didn't work well for small DOM tubing. But I don't remember them stating one that worked well for cheap tho.

 

If I'm going to spend 300+ on a tube bender then it better do 3.5in tubing and below not just 2in and below, as I'll want to use it to make my exhaust.

[JMortensen]

The easiest thing to do on exhaust is buy prebuilt mandrel bends. You can get them from Jegs, Summit, even JC Whitney.

 

I just received this tubing bender yesterday: http://www.speedwaymotors.com/p/6614,,_3rd-Generation-Speedway-Hydraulic-Round-Tubing-Bender.html?itemNo=TUBING+BENDER

 

Looks good but I haven't tried it yet, tubing should be arriving in the next few days.

[CableSrv]

ouch.. 400 bucks and can't bend larger than 1 5/8's!! Problem is justifying that purchase... I just can't see me bending that much tubing that would require me to pay an extra 400 bucks for it. I'm already going to be spending alot on DOM tubing and other random metals. If only someone had one locally that would rent it to me *wink* *wink*

[lbhsbZ]

Tools to do the job properly cost money. If you don't spend the money on the proper tools to do the job right, you will end up spending almost as much money doing the job wrong, then more time and money redoing it right. There are some spots where you can get creative and acheive similar results with less monetary expense, but experience has taught me that the 49 hours I spent figuring out a different way to skin the cat does not make up for the $$$ that I would have spent on the tools to do the job in 5 hours.

Good luck finding a decent bender with Dies for $300. I spent $700 on my pro-tools 105, and if I want it to bend anything other than 1.5" OD tubing, additional dies are $200 each. I'll probably only use it once or twice, but I bought it anyway...becuase in my eyes, spending $700 is better than dealing with a poorly fiting cage for as long as I own this car, and possibly the next one.

 

The best idea would be to find a club or start one of people in your area that like to play with cars and are amature fabricators. As a club, get everyone to pool some money and buy the expensive tools that will see limited use. It makes much more sense to have 10 people paying $70 each for a bender, that they can all use when they need it, than it does for one individual to buy a $700 bender, use it once, and stick in the garage for the 20 years.

[74_5.0L_Z]

You mean something like this:

 

[CableSrv]

yes you are one of my biggest reasons for wanting to do this!! seeing that much room in a z to work on the engine and how much more weight you save! not to mention how much more strength you've gained in both suspension and engine tie in!

 

question for you tho, I'm not quite seeing where you are attaching the tube chassis to the structure points of the z! in the third picture I see a bar in the center look like it's going into the cabin possibly to connect to the roll cage inside ? and where is the bottom bar connecting to ? also why have a bar right next to the firewall ? isn't the firewall itself enough support in that area ?

[CableSrv]

lol here is the other user that also got me really intrested in a front tube chassis

 

http://album.hybridz.org/showphoto.php?photo=2999&cat=500&ppuser=12636

[74_5.0L_Z]

"I'm not quite seeing where you are attaching the tube chassis to the structure points of the z!"

 

You'll discover when you cut off the front end that all the metal of the Z is very soft and flimsy. At that point you will not feel very comfortable attaching anything to the firewall as a stuctural element.

 

My solution was this:

 

First, hard mount the car on a surface that gives you a good reference to work from. For me, I built a 2 x 12 wooden structure topped with 1" MDF that just barely fit between the stock frame rails (25.1" wide). This structure extended from the rear (Point C of the factory frame drawing) to past the front. I then aligned the car on this structure and bolted it down. Then I made sure the whole thing was level. From that point on the car did not move relative to the structure.

 

Next, I built frame rails (similar to pparaska's). These were welded to the rear cross member, to the floor pan, and to the firewall.

 

After I had the frame in place, I built the roll bar. It is tied into the rear shock towers and the rear of the rocker panels. From this, I extended door bars forward through the firewall. The door bars then connect to the hoop in front of the firewall. The point where the lower door bar meets the firewall hoop is also welded to the front of the rocker panel, and also meets a bar that angles to the frame above the T/C mount. The point where the upper door bar penetrates the firewall is just below and outboard of the clutch master cylinder. This point is triangulated to the frame and to the strut tower.

 

The bar across the top of the firewall hoop was mainly there to connect the top legs that go to the strut towers.

 

My front end is attched to the car through the framerails, rocker panels, and door bars. However you decide to do yours, spread the load through as much surface area as possible.

[boodlefoof]

Glad to see another person with the desire to get his hands dirty!

 

The 140 will have adequate power to weld the gauge of steel you will need to use to make your frame. With any welding project though, pay close attention to joint preparation and you will be fine. Practice on some scraps first.

 

As for building a front frame for the car, you will be able to save a lot of money and headaches by using square and rectangular tubing rather than round tube. Prices for square tube are typically less than half of ERW round and probably about a quarter of the price of DOM. Then, you can avoid the cost of buying a tubing bender and/or tubing notcher and just make straight cuts in the square steel tube.

 

For materials, mild steel will be the easiest to work and learn with. To be safe, go with .120'' wall tubing (2x2'' square is very versitile). Perhaps use a pair of 2x3'' main rails and build up from there. If you pay attention to frame design, you can use some thinner wall tubing, but anything with a suspension pickup on it should probably not go below .095'' and even then should be reinforced.

 

Start by designing your suspension (if you're going through the trouble of building a new frame from scratch, you don't want to finish it and end up with bad suspension geometry).

 

Then, design your frame around the suspension. Pay attention to the load paths in your frame and your attachment points. Building the best front snout in the world will not make any improvement if it isn't (1) attached securely to the rest of the car and (2) attached squarely to the rest of the car. The firewall isn't particularly strong, so sending loads from the front frame into the firewall isn't the best idea without some form of reinforcement. Door bars can be used (as 7.0_5L_Z has).

 

Good luck. I look forward to hearing of your progress.

 

You can check out my web page for some information about building a spaceframe for a Z.

[CableSrv]

I see!! I'm use to the newer cars were the firewall is a large structrual point for the vehicals. Curious now... why don't more people use square tubing if it's cheaper and still possess the same strength as erw or dom tubing? not to mention you can get away without a tube bender for square just by cutting it and welding it to angles. Is it just because square isn't exactly best looking tubing for the car? or am I missing something?

 

74_5.0L_Z, thank you so much for showing me and explaining all about your front tube chassis! It now makes total sense. I assumed these cars were like the newer ones in that the firewall was a large structural point but I was absolutely wrong and would have made a very nasty mess had someone not explained that.

 

Curious how have most of you lopped off the front end? sawzall? cut off? or something else?

 

This is why I love hybridz! you guys rock!

[74_5.0L_Z]

I used a hand held grinder with a 4.5" cut-off wheel and tin snips. The metal that I removed from the firewall forward (not including fenders, hood, crossmember, front apron) weighed 95 lbs. The tubing that replaced it weighed less than 50 lbs.

 

Oh, do yourself a favor: Remove all of the undercoating and sound deadening material before you start. It's easier to do that before you have the car bolted to your fixture. Don't ask me how I know that....

[CableSrv]

LOL! yea i've already removed all the interior tar and stuff... once I get my new flap disk for my angle grinder i'll get to work on removing the rest.

 

Atm my biggest hurdle is getting the engine trans out asap so i can get to fully tearing apart my z! right now the z is just gutted interior wise and awaiting for the engine removal before I really get to work on fixing the frame rails and floor pans and then building the cage.

[JMortensen]

LOL! yea i've already removed all the interior tar and stuff... once I get my new flap disk for my angle grinder i'll get to work on removing the rest.

I tried everything from a heat gun to a flap disk to a wire wheel to remove the tar from the bottom of the car. What worked the best for me was a propane torch and a scraper, then finish with the wire wheel. Just put the heat on the tar until it starts to bubble, then scrape it off. Give it a try before you do the whole thing with a flap disk...