Extending a wheelbase...

[Will]

Thinking about chopping my old Winnebago up to make a toter-home out of it. To pull this off I really need to add 31" to the wheelbase. There's a section before the back axle that is straight and 34" long with no obstructions or crossmembers. I could cut that in half and add 2 65" sections there, doubling it 17" on each end, but it's only 2" from the frame to the bottom of the motorhome and I don't think I can weld in that gap. Would putting a shitload of bolts instead be better? I've seen straight trucks with the frame lengthend by bolting.

The other option is to cut it off and not re-use the back half of the existing frame. I can double it as far forward as it practical and bolt the leaf hangers to my added section.

One problem is there isn't a standard channel available that will just snuggly fit in there.

This is what the frame looks like, but it's not mine. I'm not wanting to tear the floor out. My boosters are way up front and not in the way as they are on this one.

This is what the machine looks like now:

This is what I want it to look like. I can't leave enough space inside and use a gooseneck hitch without the wheelbase extension.

 

[red85]

I would recommend welding the frame, Will. Remember the old Citroen 2cv's? They were bolted together and they would basically disassemble themselves over time. What about bolting it together and then welding the bolts? That way the frame would be allowed to flex (like a transport truck) and you wouldn't have to worry about a weld breaking or a bolt coming out.

Phil

 

[Will]

Ford tech?

The frame splice technique, and the methods used to splice and re-connect the related vehicle
systems, must be in accordance with the guidelines established in MVE-11 and QVM Bulletin Q-18,
Guidelines for Modifying Ford Light Truck Wheelbases.

Does anyone have a copy of this available?

 

[almostclueless]

Sounds like the perfect technique to be messed up by subpar techs LOL

 

[Dave R]

Have you tried this....

MVE11


or this.....

chassis stretching


Chassis stretching/shrinking isn't that difficult. Just make sure your filler and reinforcing plates are as thick or thicker than the original frame. Measure and cut carefully, then measure 5-6 times to ensure everything is square and straight before you tack it together. Then measure one or two more times before fully welding and attaching the reinforcing plates, to both the inside and the outside joints. Also, yor reinforcing plates should not be square, if that's not clear, note picture 9 of the station 2 section in the second link.

 

[Will]

Good article Dave, thanks. Hard to see exactly what's going on it there. What I think I see in that picture is the extension piece is the same dimentsion as the frame, and is butt welded in there. Than the diamond plates are added to the inside--2 per side. After that, the reinforcement angle is only on the bottom flange and goes up the outside. Is that what you see in there?

Trying to squint into those pictures is killing my eyes.

The crap I've seen welded together on truck frames makes me think just about anything would hold if the welds were well done.

 

[almostclueless]

Thats surprising to me. I wonder how many truck frames are heat treated and how much it is affected by welding.

 

[Will]

There's nothing special about most truck frames. It's just steel. It's not hard to make it strong enough, the factor that concerns me is the amount of twisting and bending a frame sees in normal use--you want to avoid a hard spot--a sudden change in the stiffness of the frame. I wanted to make sure I followed an established procedure to account for those things I am not qualified to think about.

 

[Dave R]

Hard to see exactly what's going on it there.

Man, you are getting old. But, then again after doing it 6-7 times myself I know what their doing.

What I think I see in that picture is the extension piece is the same dimentsion as the frame, and is butt welded in there. Than the diamond plates are added to the inside--2 per side. After that, the reinforcement angle is only on the bottom flange and goes up the outside. Is that what you see in there?

Yep, that's about it. The most important thing is making 100% sure that you extend each side the same amount and you keep the frame straight and level. The diamond shaped interior plates need to go over the joint(s) i.e. one plate per side for shortening a frame and two per side for lengthening. Personally, I've always put the exterior reinforcing plates on both the top and the bottom but, technically, it's only required on the bottom. If you want to get into the overkill end of things, instead of using angle as the exterior reinforcement, use a 1/4" strip as wide as the frame, fully welded, on the top and underside extending about 6-12" beyond the joints in both directions. Then add a side plate, also 1/4" thick, as tall as the frame on the side, also extending 6-12" fore and aft of the joints. It's a lot of welding and quite a bit of weight but it isn't going ANYWHERE once your done.

The crap I've seen welded together on truck frames makes me think just about anything would hold if the welds were well done.

Ain't that the truth. A friend of mine drove/ran a medium sized crane truck for a somewhat "fly-by-night" operation, that thing was in the shop nearly every year having it's frame reinforced.

 

[Will]

Thanks Dave. That's the proceedure I'm going to follow, at least as closely as I can. My frame isn't a standard dimension channel so I may have to deviate a bit.

This beauty has 4 bolts per end holding the frame extension--and nothing else. Of course the giant piece of bridge timber and the steel deck also help.

And in lieu of the diamond plates, these guys cut the shape into it. I think that's all they do--cut the extension into the same shape and weld it up. It also gets a truck body bolted to it so that reinforced it a lot I guess.

 

[Jspafford]

Will, are you working on the Winnie?

 

[Will]

I pulled the old thing up by the garage last week. I'm making my plans and sharpening my angle grinder. I'm not absolutely commited but I'm pretty convinced life on the planet will suffer if I don't do this.

 

[Dave R]

My frame isn't a standard dimension channel so I may have to deviate a bit.

That's not a big deal either. How much are you adding in? On shorter (<12") pieces I've just used two pieces of steel, bent them each 90*, then trimmed them until they fit in the space created. If you have a fabrication/welding shop nearby you can also have them bend the C-section shape that you need out of plate. The place I use usually charges me $20-30 for both pieces.

 

[Will]

I want to lengthen it 31". The place I buy steel has giant brakes and sheers. I don't know if they can do this type of thing but I'll give them a call. That's probably the best option because the frame is 7.25" high and the flanges are 2.75". I don't really see anything close to that.

By the way, I usually use this site when I plan projects and they always have what I ask for at the steel yard near me. I'm guessing this is pretty standard but I son't know.

 

[351ranger]

What are you using for a welder? 2" gap is fairly big. You should be able to get in there with a mig or even a stick welder. It's hard to say without seeing it though, I know some spots seem to be easy to get to but no matter what you just can't do it! As far as the channel goes, do you have a local place that could form some flat 1/4" stock to fit snug over the exsisting frame? If not you can always fill the gap at the bottom with some flat stock and weld it all up. Wouldn't hurt to throw some bolts in it to just for some extra strength. I don't think it would be needed if welded good but but it might help you sleep at night.