What is correct way to lengthen/shorten truck frame? - TheDieselGarage.com
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post #1 of 31 (permalink) Old 11-28-2009, 10:45 PM Thread Starter
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What is correct way to lengthen/shorten truck frame?

what is the correct way to shorten/lengthen a truck frame?

reason being , I am looking to lengthen a IHC 8100 tractor into a straight truck length.

what is standard way to do this, weld,fish plate etc? I will probably run double frame just to make sure it has enough strength.

truck will probably be registered at 33-39k

any insight?
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post #2 of 31 (permalink) Old 11-28-2009, 11:44 PM
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what we always do is cut it with a cut off wheel,then grind the edges to a v and weld your way out.keep grinding it after each weld so you keep good penatration.then we get 1/4 inch steel broke for fishplates and bolt em in.never had a problem yet.hope that helps a little.
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post #3 of 31 (permalink) Old 11-29-2009, 12:53 AM
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I have done more of both(shorter & longer) than I can remember.ktw900 reply is very good. If the frame is doubled already, you will have to stagger the cut. If it is a single frame rail, you can make your cuts with a torch, cut off wheel, plasma or whatever you have to work with, clean up your cuts and "V" both sides of rail to be welded. Then I fab a large diamond fishplate that is a little less than the width of the frame rail and approx. 10 inches to either side of center. NEVER weld straight up & down from top to bottom as the frame will crack beside the weld. Use 7018 if your welder will, or mig if you have one. The welded joint will be as good as your preparation . Good luk
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post #4 of 31 (permalink) Old 11-29-2009, 01:28 AM
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Originally Posted by broncobob View Post
I have done more of both(shorter & longer) than I can remember.ktw900 reply is very good. If the frame is doubled already, you will have to stagger the cut. If it is a single frame rail, you can make your cuts with a torch, cut off wheel, plasma or whatever you have to work with, clean up your cuts and "V" both sides of rail to be welded. Then I fab a large diamond fishplate that is a little less than the width of the frame rail and approx. 10 inches to either side of center. NEVER weld straight up & down from top to bottom as the frame will crack beside the weld. Use 7018 if your welder will, or mig if you have one. The welded joint will be as good as your preparation . Good luk
we have welded top to bottom everytime,never had a problem yet with crackin.i prefer a cut off wheel,least amount of heat transfer but thats just me.different strokes for different folks i guess.
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post #5 of 31 (permalink) Old 11-29-2009, 01:59 AM
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I have done dozens of extensions and shortenings, and you guys are all spot on.

I usually cut the rail on a 45deg angle and i reverse it on the other side. Just habit i guess, but it works well, and havent had one fail yet.

I use a Bevel Gauge to make sure i get the angle right on all the cuts, (nothing more annoying that finding the angle on your new rail is a little out of angle), and I always use new rail.

We have a fabrication shop nearby, and i have the new rail sections pressed up from 350 grade high tensile. I never use old/recycled rail, its old for a reason and usually becomes brittle after welding.

I fit a "liner" inside the rail, and usually about 4' long, which is just a smaller section of chassis rail. If the extension is only a small distance, (2-4') I usually just line the whole section to a few feet beyond the joins.

Best way to get it all straight it to find a common point in the old chassis and diagonally measure past the new section to another common point in the old section.

I also tend to put a very small amount of positive camber in if possible so make sure you support it all well and keep it straight whilst welding it together.

If your extending a long way you will also need to put a few more crossmembers in, and fit a center bearing in your tailsahft assemblies, perhaps even 2.



All in all, not a hard job, and as my dear ol dad the engineer taught me...

..... "Measure Twice, Cut once"....

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post #6 of 31 (permalink) Old 11-29-2009, 05:11 AM
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Cool

Lots of good info here I just have a couple of addons . when you park the truck move it back and forth a few times to make sure you don't have any scrub stress on the frame . and when ever I strech or shorten a frame I make a set of centerpunch marks exactly 1 foot from the cut/joint for a double check reference , makes you a lot more comfortable when you start to weld to be able to recheck your measurements, I also always make all my cuts 45 degrees but have seen many straight joints also. 45s give you more weld area
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post #7 of 31 (permalink) Old 11-29-2009, 12:08 PM
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Quote:
Originally Posted by ktw900 View Post
i prefer a cut off wheel,least amount of heat transfer but thats just me.
I'd prefer a plasma cutter over a cutting wheel, and over a torch. Cutting wheel can make plenty of heat its self.

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post #8 of 31 (permalink) Old 11-29-2009, 12:30 PM
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Quote:
Originally Posted by bmoeller View Post
I'd prefer a plasma cutter over a cutting wheel, and over a torch. Cutting wheel can make plenty of heat its self.
heat from the cutting wheel does not compare to the welding heat, using a guide to make a precision cut would help.

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post #9 of 31 (permalink) Old 11-29-2009, 02:06 PM
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Quote:
Originally Posted by bmoeller View Post
I'd prefer a plasma cutter over a cutting wheel, and over a torch. Cutting wheel can make plenty of heat its self.
I agree, but it takes a pretty good plasma cutter to get through frame.

Personally I would have bought a longer truck, anytime you hack a frame and peice it back together I think you lose integrity, but thats just my opinion.

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post #10 of 31 (permalink) Old 11-29-2009, 04:49 PM
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I,ve only lengthened 3 trucks over the years,. 'Z' cuts to the frame,. beveled edges, rose bud to heat up 6" either side of the weld,. fishplate on the inside,.cross member every 36" or so,.
the one truck is now a 260" 'tri axle' dump with the lift axle in front of the drives,. its been on plenty of mud jobs hauling evil amounts of weight,. never had any issues,.
and for folks that think you're compromising the integrity of the original frame by stretching it,. well mebbe you oughta go look at how they build ships,.

Nick
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