Broken frame

[Michel Szulc Krzyzanowski]

Is there somebody that knows the details of the recent situation of Douglas Hackney's Fuso FG expedition vehicle?
Apparently his frame broke in South America.

 

[Tree]

OH MAN! That really sucks, he did overload a little bit but I didnt think the frame would break. Did it just crack, whole thing snap off or what? I would hate to break something like that so far away from home. If its a crack would some metal and welding hold it together? Well best of luck to him. I hope he finds some solution.

 

[kjp1969]

Here's the post from Doug's blog:
http://www.hackneys.com/travel/ecuador/justanotherday.pdf

Bummer. Sometimes these seemingly big problems are easily repaired. I recall a story about the original Earthroamer breaking in Baja, and the fix was doable at a local welder. Let's hope the same is true here.

 

[kerry]

That's not good. Here's a link to the blog with a picture of the break. It's not a small crack. The frame is completely broken in two. It's hard for me to tell where it is given the tightness of the shot, but no matter where it is, it's not going to be a simple repair since it looks like access is going to be difficult. I can sympathize with their feelings. I had the frame break on a motorhome I once owned.

http://www.hackneys.com/travel/ecuador/justanotherday.pdf

 

[Tree]

Wow I just read it and finally saw that broken frame picture. It tore right off. Would they have to take off everything to get at it? Im getting scared just thinking about what would of happened if the right side broke too. And I like how he says... Another day on the road....real calm man! :costumed-smiley-007

 

[kerry]

Can anyone figure out if that picture is from the back looking forward or forward looking back?

If it were me, I'd be thinking that if the left side broke, the right side can't be in much better condition so something needs to be done to reinforce the frame on the right as well as fix the left. I'm guessing that given the location of the cross brace in the picture immediately in front (?) of the break, the back(?) of the frame has been flexing for a long time.

Here's a picture from Doug's build thread. That break has to be next to one of those cross members in front and behind the rear axle:

http://www.hackneys.com/mitsu/photos/BEV_buildup/image001.htm

 

[Tree]

Not sure Kerry but isn't that the leaf springs to the left of the frame. They are kind of dirty so its hard to tell. So according to the leaf spring we are looking at the left frame from the back....I think... that picture confuses me :Wow1:

 

[pplkook]

The world is such a small place. I saw this guy a couple years ago when he first finished his truck down at a Baja surf spot called Alejandros a couple points north of the wall.

Bummer about the frame.

 

[kerry]

I have a question for the more engineer minded amongst us. Looking at this picture of Doug's pivot frame:

http://www.hackneys.com/mitsu/photos/buildup_album_03/image001.htm

It looks to me as if the load of the camper is concentrated at the three points of the pivot frame with the rear load being carried at the pivot bolt right at the very back. Does this set up in any way increase the possibility for frame flex compared to a commercial truck box which would mount directly on top the frame rails?

 

[ntsqd]

If they were in Baja they could find someone who knew how to fix that.

I would imagine that life conditions aren't all that different where they are, and that there would be folks around who can fix it. May even be easier to find someone willing as they're not as likely to be worried about being sued.

Kerry, It will allow for more frame flex, which is the whole point. Trying to make a ladder frame that long rigid enough to not flex under the expected loads isn't really feasible. Mogs use this approach, three point loadings, quite successfully. It's the old 3 points define a plane thing. Adding a fourth point or more usually isn't a problem in theory, but we've all sat on that 4 legged barstool with one slightly shorter leg.

 

[kerry]

I understand how it allows for frame flex on uneven terrain. It seems to me that under those conditions, the frame is 'twisting' to accommodate the uneven terrain. What I was thinking was the the long distance between the load points allows for vertical flex on rough roads which, all other things being equal, are conditions under which frame flex isn't necessary. I don't have any idea as to how both conditions could be dealt with in a single design

 

[Michel Szulc Krzyzanowski]

Latest news: it seems Doug's Fuso is being shipped back to San Diego right now. Mitsubishi engineers are studying how to solve this problem.

 

[bigreen505]

Michel - a sincere thank you for the updates!

 

[kerry]

Yikes! Is that a tow covered by AAA?
Oh, I get it. It's under warranty.

 

[FusoFG]

I have a question for the more engineer minded amongst us. Looking at this picture of Doug's pivot frame:

http://www.hackneys.com/mitsu/photos/buildup_album_03/image001.htm

It looks to me as if the load of the camper is concentrated at the three points of the pivot frame with the rear load being carried at the pivot bolt right at the very back. Does this set up in any way increase the possibility for frame flex compared to a commercial truck box which would mount directly on top the frame rails?

I don't think the 3 points increases the possibility of frame flex because for the allowable load (about 8000 lbs) the frame is supposed to flex to allow the wheels to stay on the ground.

That's why the frame is riveted and bolted together and not welded into one rigid piece.

The problem with just 3 mounting points is that concentrating the load in just 3 places may exceed the capacity of the frame at one of those points. Even though it's less than the maximum payload.

The Mitsubishi body builder manual says that you have to distribute the load over the frame and not concentrate it in just a few places.

That's why, depending on the load, a 4 point mount is better than a 3 point mount. It spreads the load over more of the frame.

Unimog uses a 4 point frame.

If you think about it, a 3 point mount is really only a 2 point mount. The 2 flexible mounts at one end are really in one place horizontally along the frame. And the 3rd pivot is at the other end of the frame.

A 4 point mount, like the unimog, would distribute a third of the weight at one end, a third of the weight in the middle and a third of the weight at the other end.

Myself, Darrin and others have used 3 point mounts, but my load is under 4000 lbs, less than half the maximum payload. Plus in Darrin's case, he used a sub frame that spread the load over the entire frame much like a normal truck body would do.

Maybe if you are closer to or above the maximum payload, a 4 point mount is better.

I can't tell from the picture where the break is either, but in addition to using a 3 point mount and exceeding the maximum payload, Doug also extended the frame.

If his extension was more rigid than the rest of the factory frame it could have created a stress point or hot spot where the normal flexing of the frame was concentrated and caused a fracture from repeated bending at one spot.

It sounds from his report and the update that the camper is being shipped home that they are okay.

Beats having a problem like this if they were sailing across the ocean instead of driving on a South American road.