Carl Heideman
Carl Heideman
5/23/18 2:11 p.m.


Like stories like this? You’ll see every article as soon as it's published by reading the print edition of Grassroots Motorsports. Subscribe now.

Where do chassis come from?

It’s easy to have a kind of stork-myth response to this question: Chassis simply come from somewhere else. They’re born …

Read the rest of the story

Tom Suddard
Tom Suddard Digital Experience Director
5/23/18 2:20 p.m.

It's been a while since I read this story (from the October 2014 issue), but it's just as good now as it was then.

te72
te72 Reader
5/23/18 10:59 p.m.

What's amusing to me, Tom, is how much I've learned about welding from GRM articles. Not the "how to" part, but rather the, "ahh, so that is what I was doing wrong..." part. Either way, learning is learning.

 

I actually really enjoy the welding part. The prep work, test fitting, adjusting, more prep work, adjusting some more, putting the coat and gloves on, then the mask, only too find out that it's gotten dark and your garage isn't really well lit enough to be welding at night... that part I can't say is all that fun. Overall though, I enjoy the doors this new (to me anyway) skill has opened.

Torqued
Torqued New Reader
5/24/18 12:30 p.m.

Good, useful article!  When I first tried welding about 40 years ago, just out of college and poor as a church mouse, I wanted one outfit that could do many jobs (weld, braze, silver solder, cut, heat metal to bend it, and even do some tempering) so I bought an acetylene setup. I learned that pre-heating the entire joint with the torch, before beginning the actual weld, also helped to minimize the amount of movement of the components of the joint. Now I wasn't building things a complex as a chassis, but rather simpler things such as trailer hitches and adapting tools to special uses.  I suppose that not many weld with gas rigs anymore and I don't know whether it is practical to pre-heat before TIG or MIG welding.

classicalgas
classicalgas New Reader
5/24/18 7:38 p.m.

Good basic info, though as a career  TIG welder , I noticed that the welder in the article isn't keeping his tacks shiny... he's either not dwelling in place until the metal cools (stay put until your electrode stops glowing) or his post flow time is too short (possibly too much of a draft through the work area ) Any dullness or  gray frost on the weld is a bad sign, even on tacks. An oxidized tack will tend to cause problems when you get to the finish weld, even if you wire brush it... the damage may go below the surface.

My  only other nitpick .... not only does location and order   of  welds  in a complex structure matter in controlling distortion, the direction of each weld matters also. As an example, welding from inside toward outside  in  the corners of a square will distort it differently than out to in, even if tacked at all four corners first. Careful diagonal measurements of large  frame rectangles after a weld has cooled will alow you to bring things back into place (if need be) by using directional welds.

Aluminum and  copper alloys, and stainless steel, will tend to distort more than low carbon steel structures, in case you ever find yourself working with those metals.

te72
te72 Reader
5/25/18 12:05 a.m.

In reply to Torqued :

I know of only a couple people who even can weld with a gas setup these days. It may be that MIG is just a lot easier to pick up, but I find that just about every tool has its uses.

 

Is it practical to pre-heat your welds with a MIG / TIG? I can only speak to the MIG side of things myself, and only in limited experience at that. I've yet to NEED to pre-heat anything, but I have found that on particularly thick pieces, the weld seems to cooperate a bit more once the pieces have soaked in enough heat, so maybe!

frenchyd
frenchyd SuperDork
5/25/18 9:20 a.m.
te72 said:

In reply to Torqued :

I know of only a couple people who even can weld with a gas setup these days. It may be that MIG is just a lot easier to pick up, but I find that just about every tool has its uses.

 

Is it practical to pre-heat your welds with a MIG / TIG? I can only speak to the MIG side of things myself, and only in limited experience at that. I've yet to NEED to pre-heat anything, but I have found that on particularly thick pieces, the weld seems to cooperate a bit more once the pieces have soaked in enough heat, so maybe!

I still gas weld, I can preheat stuff and my gas welds are nicer than my MIG 

Carl Heideman
Carl Heideman
5/25/18 3:56 p.m.

In reply to classicalgas :

Great comments!  My son Jack was 16 when we did this story and was pretty new to TIG welding.  My Miller Syncrowave 185 also does not have adjustable post-flow and shuts flow off a little more quickly than I'd like.  

Your tip about weld direction is great.  I recently came across this video from Welding Tips and Tricks on YouTube that have great demonstrations about this topic.  https://www.youtube.com/watch?v=AKPwvVojfXc

 

classicalgas
classicalgas New Reader
5/25/18 4:42 p.m.

In reply to Carl Heideman :

I'd say Jack was doing great, especially for a new TIG welder. After 40 years, I'm still learning ways  to TIG better.

With solid state inverter machines now down in the home shop price range, things like wave form control   and pulse proportion control  can be a huge help...worth getting if you can.

te72
te72 Reader
5/29/18 8:53 p.m.
frenchyd said:

I still gas weld, I can preheat stuff and my gas welds are nicer than my MIG 

Nice! I've only ever played with flux core wire (ugh, unless you're in a bind) and MIG. I won't sit here and say any of my welds have ever been "pretty" but so far they've all held up.

 

I want to get into TIG welding, but the machine and a new bottle (plus I'm sure a few other odds and ends I'm not considering at the moment) add up to a pretty decent sum, money I could be spending on tires for the car, and trips to the track. It doesn't make my habit of seeing squirrels any easier, haha, I gotta focus!

bigeyedfish
bigeyedfish New Reader
5/30/18 7:16 a.m.

It might be worth mentioning that you can tig weld with pretty much any DC constant current machine, meaning if you have an old DC stick welder, you can buy an Ar tank, regulator, and a tig torch with a gas valve, and go to town.  You'll have to scratch start and you won't be able to control amperage with a foot pedal, but it's a great way to get some hood time without spending a bunch of money on a machine. Being able to scratch start is useful when you have to weld out of position and can't get a foot pedal to your work area.

Scratch start is really only obnoxious for tacking.  Also, no foot pedal means you have to pay attention coming to the end of a weld on thin metal.  It helps to use a copper or aluminum backing bar and/or to backstep on longer joints to prevent blowing through as heat builds up.

akylekoz
akylekoz Dork
5/30/18 7:30 a.m.

https://youtu.be/rLnN-hqgfxY

This is all I have to say about welding.

 

te72
te72 Reader
5/31/18 12:44 a.m.

In reply to akylekoz :

Good thing for captions haha!

jerel77494
jerel77494 New Reader
12/29/21 2:35 p.m.

Never, ever, EVER use brake cleaning solvent to clean the area.  Read about a guy who almost killed himself when he accidently welded over a small drop of fluid and inhaled the fumes.  He almost died and had respiratory problems for 6 months afterwards.  With heat and argon, brake fluid turns into phosgene.  They use it in chemical warfare.

 

EvanB
EvanB MegaDork
12/29/21 4:02 p.m.

In reply to jerel77494 :

That's true if it contains chlorinated solvents. Not all "brake clean" products do. 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
12/29/21 4:36 p.m.

In reply to EvanB :

The nice thing about non chlorinated solvents is that they do not evaporate as easily, and can hide out in crevices.

One would THINK that the shielding gas would prevent excitement, but signs point to "no".  Most memorable being the time I blew the valve cover gaskets out of an assembled engine and added half a quart to the oil pan's capacity.  It made it easier to see the crack I had been welding, at least.

frenchyd
frenchyd UltimaDork
12/29/21 8:24 p.m.

My first complete new chassis  I started at one end and welded to the other end and wound up with a twisted banana. 
   The remarkable thing was after I put the car together and adjusted the suspension.  It really was a sweet handling car.  
That winter when I made a new chassis that was square and true it never handled as well. 

lotusseven7 (Forum Supporter)
lotusseven7 (Forum Supporter) HalfDork
12/30/21 9:59 a.m.

A chassis table, lots of clamps and  only weld in one small area at a time then alternate areas = very little distortion. I too learned the hard way! No more though. 
 

 

 

wspohn
wspohn SuperDork
12/30/21 11:42 a.m.

I was friends with an old school British guy that made sports racing chassis from scratch. He used silver brazing and said that if it was good enough for Colin Chapman, it was good enough for him (and it does seem to have served him well.

If he had to join two tubes in line, he would slide a piece of smaller tubing inside after first cross-drilling the original tubes, and then plug weld through each frame tube and then finish by welding/soldering the butt joint between the main tubes. Never hd one break on him.

I asked him about the new guys that were pop riveting monocoques, and he said that his methods worked and were safe, and that while the new methods might well be superior, he wouldn't want to go out racing in a car built by someone who was early in his learning curve.  Hard to argue with that.

frenchyd
frenchyd UltimaDork
12/31/21 9:59 a.m.

In reply to wspohn :

Jaguar XKE was brazed. That is the front subframe that held up the 700 pound 6 cylinder engine and went 150 mph. It only weighed 22 pounds.  Was properly crash tested according to the US government standards and passed with flying colors ( no damage in passenger compartment) 

    My wife then proceeded to do her own crash testing at speed over 70 mph and escaped with a slight bruise. I later sold pieces off the car and recovered more than I paid for the car.  
 The frame itself was made of 1" square tubing 22 gauge,  yes thinner than sheet metal.   
     Brazing was used because the heat required didn't distort the bicycle tubing used. Yep! The front 1/2 of a Jaguar XKE is the same steel used to build bicycles !   
   The V12 version used the same tubing. ( heck the V12 was 30 pounds lighter than the Six cylinder). 
  It's also the same as the D type Jaguar that went as fast as 180 mph down the Mulsanne  straight back in 1955 during the 24 hours of LeMans. 

frenchyd
frenchyd UltimaDork
1/1/22 8:32 p.m.

In reply to lotusseven7 (Forum Supporter) :

Out of curiosity what does a lotus 7 bare chassis weigh? 
    Or Locost 7? 

Our Preferred Partners
vS67xkgAwEkxnfwysBduFBy3J1BgrCJvBdzX5tU2thPEGO3HWPknrEr4cuWQZskG