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Truck Length Modification


Cdfarabaugh

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Frames need to flex. 

Creating a stiff spot or hard point in the structure will concentrate stress, and may lead to failure.

 Quite a few original equipment manufacturers will void a warranty if welding is done on a frame just for this reason.

 Huck bolts are the method used by most coachworks to modify frame length.

 

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56 minutes ago, midnightman said:

A consideration I ponder in regards to the doubling the frame at the splice is that it creates a short very rigid section of frame. I may be wrong but would like to see the frame able to flex evenly from front to back. Personal opinion would be to use an upside down L shaped piece over the outside. I have used this method a couple times on longer stretches. Used a piece of used frame by cutting off the bottom flange 

Ours were double frame from the factory from under the cab to the back. I agree that one really stiff section and it will probably break next to it 

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1 hour ago, supermechanic said:

Frames need to flex. 

Creating a stiff spot or hard point in the structure will concentrate stress, and may lead to failure.

 Quite a few original equipment manufacturers will void a warranty if welding is done on a frame just for this reason.

 Huck bolts are the method used by most coachworks to modify frame length.

 

I'm not worried about warranty being a 1992.  Also if I was wealthy enough to afford a huck bolt setup I'd be buying a new truck.....

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I have done 6 or 8 at work.  Replaced frame rails and lengthened.  Have used PG Adams.   The ones I lengthened we cut across the top of the frame and down the side about an inch.  Then we made a 12 long inch angled cut down to the bottom.  These were all ten wheelers.  We  joined the outside frame at the location of the first cross member in front of the tandems.  On the outside of the joint we bolted on a plate to keep the box centered on the frame.  We joined the inside frame rail in between the  tandems.  They were all welded with ER70S wire.  All beveled out for near 100 percent penetration.  We haul grain and gravel as well as silage.  We have the tandems back as far as they will go and like about 12 inches from the  end of the box to the center of the hinge pin.  

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All  the points you guys bring up here have some merit. As far as stretching the frame there are as many ways as there are opinions. The most professional way I have seen is usually a single frame when stretched, they double it all the way to front axle rear shackle. I have looked at and worked on almost 500 trucks that have been stretched for grain bodies or gravel dump. Here in North Dakota almost every truck hauling sugar beets in the valley has been stretched and a box added. When the stretch a single or double frame you should plate the outside with a new formed rail. Up across the Canadian  border near midnightmans area is an old truck box mfg that can bend long pieces of frame rail. They have press brakes loacated end to end. When you have a double frame most times you should take it off and replace it with new full length. There was one place and I think it was same place that bends frame rails had a heck riveter for the big frame rail bolts. I have seen lots of the cheaper ways to add on frame. Most of the time in beet country they crack just from stress off running up piler ramp. I always thought the front pusher third axle was better if added but sometimes they like the rear tailgate lift. Again when running up a ramp middle axle takes a lot of load breaking frame eventually. The rear mount trailing tag seems the geometry when that is pushed down isn’t as bad. Whatever you do make sure that they are welded good and square.

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8 hours ago, bitty said:

On our double frame Mack RD we lengthened we didn't plate it at all. Just spliced it at the angles and staggered the splices . We did that in 1994 and it's never had any issues with the frame 

My loadstar has a 20 foot box,  its been lengthened.  Inside frame rail is straight up/down weld, outer is straight up/down weld, just staggered 3 feet. Guessing it's been like this since the 70's when it was built.

Edit to add, outer frame is the upside down L as mentioned,  inner is C channel frame. Appears to be factory based on holes drilled and huck bolts everywhere. 

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37 minutes ago, brahamfireman said:

Edit to add, outer frame is the upside down L as mentioned,  inner is C channel frame. Appears to be factory based on holes drilled and huck bolts everywhere.

Seems most llmedium duty IH trucks are done this way with the outer being an "L".  This truck is the same.  

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14 minutes ago, Cdfarabaugh said:

Seems most llmedium duty IH trucks are done this way with the outer being an "L".  This truck is the same.  

Yes you don’t see double channel until big trucks and the ones that have been stretched. Our 79 s1954 twin screw walking beam spring suspensions is double c channel factory.

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12 hours ago, Cdfarabaugh said:

Our own 14 foot single axle dum is set up like this and it's annoying as the bed height comes down when dumping, eventually only about 2 feet off the ground at full up.  I'm not sure why they were built like this, but a lot of farm trucks around were.  

This design also eliminates the possibility of having a hitch receiver 

That one has the hitch mounted on the body, and we made pins when hauling to lock the body, more recently the hitch has been moved to the end of the truck frame, where is more traditional, the body overhangs the trailer tongue, makes hooking it a pain, but otherwise doesn’t infringe on towing.  I agree that it can be annoying because it comes close to the ground when dumping, however it is one of those things you learn to work with. I agree with @bittyin principle, but not application. That body has had 8-10 yards of sand on, way more than it should, and has never gotten light in the loafers when dumping or driving. 

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23 hours ago, Finney said:

I think if conditions were perfect 70S6 would work. But I never have perfect conditions. Dual Shield would be good also.

Dad is in love with dual shield, had to buy a 400a Bernard gun for the 252 mig because the 250a couldn’t take the heat. Apparently it is a thing, the dual shield is hot. 

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