Welding on your frame

[cheford]

I've never done any extensive modifications to a frame and seeing the work that a lot of you are doing I think this is the place to start asking questions. When I asked some of the trademen welders at my place of employment they told me that you couldn't legally weld on a frame and especially what I had wanted to do which was cutting a frame in half and shortening the wheel base, but I see it being done. I understand about doing verticle welds on the frame and the stresses they create which brings the question of what is the best way to cut the frame in two, at 45% angles, straight up and down or the staggered half through the frame horizontal for 1 foot and then verticle down to the bottom.
If there are stress points on verticle welds how do you guys avoid it when you Z the frame and do the C ing of the rear frame rails, and do you have trouble getting to pass safety inspections. I have concerns sense I have shortened my frame of which was done straight through ther frame and c-channeled using 1/4 plate and feel that it is more than strong enough but how do the guys that sign the certificate for road worthiness view it?

[RunninLo]

While the [I]legalities[I] can vary with the particular situation I would disagree with the idea that all frame welding isn't legal . If that we're true many of the custom coachbuilders that do limosuines and strech conversions would be out of a job. I know that commercial vehicle such as line-haul trucks and passenger busses have resrictions most personal vehicles are exempt. My experience has been to make sure the person operating the welder has a good backgroung in welding, not just practical but theory and metallurgy. If they don't know what a heat affected zone is... RUN the other way. Ask to see their AWS card and certs. Even the self taught boys off the farm can go to a local vo-tech and get certified if they're good enough. Remember it's not just your life but those of everyone in your vehicle AND those you pass by in other vehicles or passing by.

Now that I've preached a little how bout the tech. the angle of your cut isn't terribly important to strength but a straight up and down can make the move easier to measure and line up again. I know a few people have used angle cuts in a Z but it was not for strength but to slide the suspension forward as it went up... thus centering the wheel. neat idea for that reason but does nothing for strength.

The absolute best way regardless of how you cut it is to weld it correctly. Use only enough heat to get a smooth good penetrating weld. It is tempting for novice welders to crank up the heat because the bead "flows" a little easier and can give the appearance of a good weld. More heat = more heat affected zone, the area just outside of the bead that becomes brittle. Take a look at every "weld" that you have ever seen fail. It's not the weld bead ever but usually a crack or tear just alongside the bead. That is a result of heat affected zone. So just enough heat to get the job done . Then take a small plate ( i like the diamond look ) and weld over the top to add some strength and lessen the flex that will cause cracks.

As far as the guy at the inspection station.... well if you take your time and make everything clean and as close to a factory look as possible they probably won't even know what they're looking at. If you got bubble gum welds and zany cuts and jaggies everywhere.... slip a $50 under his coffee cup.

Josh

[Bob@ProAuto]

Good advice RunninLo. Over at Webrodder, there is an article on shortening a 67-72 longbed and making it a shortbed. This has the 45 degree cuts and another piece of channel inserted for strength. There is also a 54 Dodge that has a new front frame section attached using the diamond plate method.

[kevindtimm]

Here's a 'hand-drawn' picture :



The diagonal lines represent what you remove. Don't forget to put a backing plate on it when you stitch the two parts together.

[N2TRUX]

Look in the FAQ forum for a well written article on this subject. In my opinion the best way to do this is in that article. It resembles that nice "caveman" drawing that kevindtimm posted for us...

[N2TRUX]

Ok, I felt like I was being lazy by not posting a link. Here's the thread I mentioned- LINK From the FAQ forum-LINK

Since I beat on kevindtimm for his drawing let me offer a better version for his file. Mad props to glock35ipsc for his skills and well written article.

[cheford]

Hi guys, thanks for your replies, the method you are describbing I had seen done on the tv show Trucks hosted by Stacy David about two weeks after I had cut straight through my frame and then welded three plates to the inside to form a c-channel,the plates are 2 feet long allowing a foot either side of my splice, this all took place before I had access to the internet and the way my luck usually runs. I'm hoping what I have done will prove to be alright.
I have been spending alot of my time on the FTE site mostly because it's a ford body and I was taking care of things regarding just that, now that I'm into the the things that power and conects my to the road should be spending more time here to pick your brains as brousing through some of the treads there are a lot of talented guys on this site. Thanks again, John

[kevindtimm]

Originally Posted by N2TRUX

Look in the FAQ forum for a well written article on this subject. In my opinion the best way to do this is in that article. It resembles that nice "caveman" drawing that kevindtimm posted for us...

Yeah, I know it's ugly - but hopefully it got the point across (and yes, I do plan on stealing yours and stashing it somewhere!)