A different approach to a LWB to SWB conversion
 

Since I needed to pull the bed on my 1970 C20 to do cab corners, I decided to make it a short bed too. My approach is different than the conversions I see most doing on this site. As a metal shaper, we are taught to plan out our cuts and splices to ease fabrication, save time, and avoid frustration later on. So I came up with a better idea to make cuts and seams easier to do and keep the original paint, well most of it. Here is my plan:

Before:

http://i137.photobucket.com/albums/q...psr66wcb7w.jpg

First remove the bed. I just cut all 8 bolts and unplugged the rear harness.

http://i137.photobucket.com/albums/q...pspykhuo1k.jpg

Remove 8" from rear of frame rails and move the slot on top forward too.

http://i137.photobucket.com/albums/q...psbgazkoye.jpg

Then remove the front most bed mounting bracket.

http://i137.photobucket.com/albums/q...pscxl3ditk.jpg

http://i137.photobucket.com/albums/q...psuioj4wkz.jpg

Then remove the front rivet of the second bracket and swing out of way. Then mark the cut. I went from the front rivet hole of the front bracket to the front rivet hole of the second brackets.

http://i137.photobucket.com/albums/q...psmpsybyvd.jpg

Then I unbolted the trailing arms from the crossmember, removed all rivets from crossmember and slid it forward 12". I welded in place. Then I cut the frame rails.

http://i137.photobucket.com/albums/q...psubjpaipt.jpg

To be continued...

Re: A different approach to a LWB to SWB conversion
 

Interesting.

More than one way to skin a cat. :metal:

Re: A different approach to a LWB to SWB conversion
 

I shortened the frame right behind the cab just like you did. The only difference was I put a 2" step notch. Sure makes it easier if you dont want to pull the cab off.

Re: A different approach to a LWB to SWB conversion
 

My cut behind the cab

Re: A different approach to a LWB to SWB conversion
 

Then I carefully aligned the rails and tack welded them together.

http://i137.photobucket.com/albums/q...ps9e5omqjs.jpg

Next did a full penn weld and ground it down so it could be tested. Then swung the bed mounts back.

http://i137.photobucket.com/albums/q...psoazhfvny.jpg

http://i137.photobucket.com/albums/q...pss2urf5cp.jpg

Cut the front drive shaft down, exhaust, and brake line.

http://i137.photobucket.com/albums/q...psawaq2o7z.jpg

Then drove it out to take a look and the new profile.

http://i137.photobucket.com/albums/q...psiv0rvi3o.jpg

Next comes the bed...

Re: A different approach to a LWB to SWB conversion
 

Nice work... does that frame need any more reinforcement in the weld area? I see a lot of people use a plate behind it.

Re: A different approach to a LWB to SWB conversion
 

95% of the people that read your thread are not going to have a clue what a penn weld is (including me) and what you mean by being "tested". I did a Google search for "penn weld" and not much came up.

Also wondering if you plated the inside of the frame at all.

Just personal preference I guess, but I would never use a straight cut to shorten a frame.

Thanks,
LockDoc

Re: A different approach to a LWB to SWB conversion
 

Full penetration weld. Means there is 100% weld joining the 2 piece of metal instead of just butting the 2 pieces together. You can see he has a slight gap between the frame rails, then he adds a small piece of metal to one side and uses weld to join it together. Hope that helps :D

Great work btw

Re: A different approach to a LWB to SWB conversion
 

penn weld is a full penetration weld. tested would mean that a certified weld inspector would check the weld for full penetration using some method of testing

Re: A different approach to a LWB to SWB conversion
 

95% of the people will not like my frame since I am not added any fish plate. A full penetration weld is just that, the weld bead is the full thickness of the material. This is done by beveling the rails and leaving a small gap before welding. Once welded, you will have a raised bead on both sides of the rail.

I then ground down the weld so it could be tested. A machine like an ultrasound and jelly is used to look for and air gaps or disturbances in the metal. Also, grinding the weld smooth avoids any stress spots or sharp edges.

If the weld was not 100%, I would add a brake formed channel to fit inside the rail. This is much better than a fish plate or boxing plate.

Now, off to the bed. I completely disassembled the bed and cut down the floor pan. 12" off the front and 7.5" off the rear.

http://i137.photobucket.com/albums/q...psjsblknya.jpg

I drilled new front and rear mounting holes in the pan and bolted it to the frame.

You can see it still looks factory.
http://i137.photobucket.com/albums/q...psxbw0zgs5.jpg

For the rear, I saved the rear cross sill and put it back on the frame and under the pan.

http://i137.photobucket.com/albums/q...pspqi9tzwo.jpg

Then I started to tip over the 1/2" of floor pan I saved when I cut 7.5" off.

http://i137.photobucket.com/albums/q...pslypvyg8y.jpg

Once fully tipped, I plug welded the pan back down to the cross sill. The floor is now a SWB pan and no splicing like all others I have seen here. I saved over 10' of weld and kept my original paint.

http://i137.photobucket.com/albums/q...pss1f9gw6y.jpg
http://i137.photobucket.com/albums/q...ps4u11e9z1.jpg
http://i137.photobucket.com/albums/q...pstcsimecn.jpg
http://i137.photobucket.com/albums/q...psiscjxslg.jpg

Now off to the bed sides....

Re: A different approach to a LWB to SWB conversion
 

Interesting. Looking forward to seeing how you do the bed.

Re: A different approach to a LWB to SWB conversion
 

What's your plan for the front of the bed floor where the front bed panel attaches? Will you form all the beads flat where the two bolt together?

Re: A different approach to a LWB to SWB conversion
 

No. I didn't see the need to flatten the pan where the bulk head bolt down. I will just re drill the bolts between the ribs of the pan.

I am aiming to keep as much of the original paint and rust as possible. I do not want two huge weld seam on the sides of the bed. I can't keep the original paint or finish the weld that way. It would surely require bondo and new paint with that cut down method.

Re: A different approach to a LWB to SWB conversion
 

I'm pretty much amazed so far. I'm looking forward to the bed work

Re: A different approach to a LWB to SWB conversion
 

How do you plan on shortening the bed sides without weld seams while still retaining a factory short bed appearance?

Re: A different approach to a LWB to SWB conversion
 

For the front of the bed I scribe two lines. My cut line at 11 1/8" and my tipping line at 12". More pictures as I go....

Re: A different approach to a LWB to SWB conversion
 

looks like very nice work. waiting for more pics

Re: A different approach to a LWB to SWB conversion
 

Looks great! You work wonders with metal and it sure is fun to watch.

Re: A different approach to a LWB to SWB conversion
 

This is great info for when I shorten mine :metal:

Re: A different approach to a LWB to SWB conversion
 

Some good ideas

Re: A different approach to a LWB to SWB conversion
 

Nice

Re: A different approach to a LWB to SWB conversion
 

Looks great.

Re: A different approach to a LWB to SWB conversion
 

The bulkhead will just bolt to the floor pan something like this. I will drill holes on the lows of the pan.

http://i137.photobucket.com/albums/q...psh9abejoo.jpg

Here are my scribe lines on the front of the bed side. One for cutting and one for tipping over the edge.

http://i137.photobucket.com/albums/q...pss3rnnwen.jpg

I will tip the edge over just like the factory did here.
http://i137.photobucket.com/albums/q...psxq7z6nd0.jpg

If I wanted to, I could just weld the bed side back together right at the edge. But I don't want to burn the paint if I don't have to.

http://i137.photobucket.com/albums/q...psazd6f1ox.jpg

Once I cut the extra material off, I started to tip over the inner panel. Again no welding here.

http://i137.photobucket.com/albums/q...pswjqjfqa7.jpg

And started to tip over the outer bed skin.

http://i137.photobucket.com/albums/q...pstlxeyo1e.jpg

With the inner panel fully tipped, I slid the end cap in place to see my progress.

http://i137.photobucket.com/albums/q...pszihiuswp.jpg
http://i137.photobucket.com/albums/q...psicfti1jk.jpg

Test fit is looking good. I just need to complete tipping the outer skin to the end cap, spot weld back together and add the front bed pocket to finish up this corner.
http://i137.photobucket.com/albums/q...psqpqx8hb3.jpg

100% of the original paint save and 17' of weld avoided so far.

Re: A different approach to a LWB to SWB conversion
 

Damn fine work fella! Nice and original looking

Re: A different approach to a LWB to SWB conversion
 

I'm kind of curious how your frame will do without fish plating it. You have two brittle lines running up your frame. Fish plating spreads that stress over multiple areas. It's not a matter of whether the weld is completely penetrated, it's the stress on the toes of the weld. Without heat treating, those toes will be weaker than the weld or the unheated frame.

Jeff

Re: A different approach to a LWB to SWB conversion
 

I understand everyone's concern about the frame. I have been doing this for nearly 30 years now and have never had a weld crack, even on some very high horsepower trucks. Remember, this is a C20 and the frame rail is about 50% thicker than a C10 frame.

Skinning the rail with a channel that fits inside would be insurance that everyone can see and understand. Welding is still mysterious to most and not trusted with your life. I am a unlimited thickness certified welder. The frame will stay as is. All others please add fish plates and not follow my example here.

Re: A different approach to a LWB to SWB conversion
 

I'm a longbed guy myself but your are doing a fantastic job!

Re: A different approach to a LWB to SWB conversion
 

My wife wanted it cut down. She didn't like the look of the long bed. Pressure from her made me convert it.

Re: A different approach to a LWB to SWB conversion
 

You have some fine fabrication skills, I like how you are doing the bed.

Re: A different approach to a LWB to SWB conversion
 

Great fab work, I always wondered why no one did the bedsides like this. I am curious how you do the rear half of the bedsides though. You obviously know what you are doing and I understand the difference in frame welding from a guy with a welder like me to a real cert welder like you. Keep up the great work.

Re: A different approach to a LWB to SWB conversion
 

No need to get defensive, I just don't want anyone else thinking this is the proper way to weld a frame. Welding is not a mystery to me. If we're throwing experience out I will tell you I've been welding for about 40 years, but a journeyman for only about 30 of that. I have a fair amount of both formal training and experience with heat treating techniques and practical experience pertaining to a variety of metal, including mild steel. To not acknowledge the change in space lattice and the resultant vertical stress points just doesn't make sense. Without heat treatment that frame is weak on each side of the weld. Not opinion, fact. Either most every frame shop in the nation doesn't possess your talent or fish plating is an industry standard for a reason. I appreciate your craftsmanship, but would not do a frame like that anywhere but maybe the ends. I hope anyone else doing this consults more sources before they proceed. Good luck!

Re: A different approach to a LWB to SWB conversion
 

The weld is the same type of weld used in piping. Nuclear plants and any other plant use full pentration welds with beveled ends. No difference. Nice job man. Being a common weld with QC inspections for the full penitration. Certified welders can do this with no problems. As stated most people are not going to be certified in this type of welding. It takes years to gain this type of certifaction. It takes even more practice to keep it. :chevy:

Re: A different approach to a LWB to SWB conversion
 

As one who has the certification I will tell you this is not the same as nuke piping. Mild steel isn't used in nuke piping. Nuke piping is welded with TIG. It's generally not steel period. There are many types of welded assemblies that are require fullpenetration welds. No mystery there. The toes are an issue. There's a reason for fish plating and its not because no one has enough expertise to do it. It's because the heat put into the steel causes the toes to become brittle. That's why heat treating exists. The steel in a weld is stronger than the base material, but the adjacent steel undergoes changes that induce internal stress in the steel and it becomes the failure point. Once again, this isn't a welder ability issue, this is metallurgy. If you can tell me the weld technique that leaves the space lattice of the toe unchanged I will be happy to try it. Unfortunately, welding puts heat into the base material and that changes its characteristics. Not my opinion, fact. If the truck is ran like most trucks these days it may very well be ok, but if it fails it will be next to those welds, even if they're perfect. I won't argue it further as its not a subjective issue, but since you brought nuke plants into it I thought I'd respond.

Re: A different approach to a LWB to SWB conversion
 

Okay, can we stop the pissing match and get back to the "outside of the shortbox" thinking here? The man has talent and great imagination, Lookin forward to more :metal:

Re: A different approach to a LWB to SWB conversion
 

Curious about bed rear as well.

Re: A different approach to a LWB to SWB conversion
 

Any of you certified welders know what the reduction in material allowables is due to welding? We could do a quick axial and bending calculation on the frame and see if it's anywhere close to Fty. My guess is that with a good weld and a 3 ton load at the rear bumper, it should be no problem with a C20 frame.

At least the analytic calculations would stop the conjecture whether it will fail or not.

I think this method of cutting down a LWB could save a ton of welding and body work. I can't wait to see the final product and how you tackle the hardest part.

Re: A different approach to a LWB to SWB conversion
 

True statement.

Maybe since its a thicker frame than any Swb that ever left the factory with, it will have stresses low enough to not be an issue, but so much of it depends on usage (loads and miles driven). A fishplate or formed channel insert just seems like cheap insurance.

I like what he is doing here otherwise, this seems like a well thought out way to shorten the bed and Im on my toes to see how he does the back part of the bed.

Re: A different approach to a LWB to SWB conversion
 

Probably a fatigue crack propagation problem, which occurs at less than yield. If we could find guidance on reduction allowances, just multiply the allowable stress by the x sectional area of the C20 frame and compare to same calculation with a stock swb C10 frame and no allowance.

Re: A different approach to a LWB to SWB conversion
 

I'm wondering why this guy is catching so much trouble here? I've welded two things in my life, so would I try this, no. Dude has been welding 30 years, and by reading, does it everyday. I'm sure he wouldn't do something that isn't going to work. Has he told anyone to do it his way? He made a build thread for us to look at, not junk up with a bunch of middle school crap. Send him a pm if you want to tell him his way won't work or whatever. Maybe it's because he hasn't built a truck on here yet. Not that I want to drag others in, but what if superflysteiny did this? I almost bet no one would say a word about it.

*Eric, I love reading your builds. You're a household name around here. Just used you as a point guess you could say.

Now, I'd love to see these besides, please continue sir.

Tom

Re: A different approach to a LWB to SWB conversion
 

I'm not sure this thread will last much longer if it becomes a massive critique about what one man decides to do with his property. I for one would like to see it continue on the right track.... perhaps with pictures of shortened bed sides ;):metal: