Camper 3-point subframe crack

[pugslyyy]

In order to make a repair to my gray water line (leaking between the holding tank and the drain valve), I had to take the camper off of the service body. This gave me the first opportunity to inspect the frame from above (and the first time since construction that this was possible)

Everything looked as you would expect for a 7 year old truck that has been the length of South America. Plenty of dirt and plenty of surface rust. What I wasn't planning on finding was this nice little crack, emanating from where the three-point subframe attaches at the front driver side (the single pivot is at the rear)





I'm going to fix this, but from the rust it has obviously been this way for a long time.

When I have some more time tomorrow I'm going to go in there with the right tools to grind away the paint and surface rust to get a better idea of what I'm dealing with.

 

[gait]

difficult for me to see ... is something attached to top or bottom face of chassis rail?

 

[pugslyyy]

It is bolted to the frame rail through the side, the sub frame is resting on the top of the frame rail.

The crack looks like a result of the frame twisting underneath the sub-frame. The weld doesn't look the greatest, and I could see where there would be pretty good stress risers at the point where the crack started.

 

[k9lestat]

http://robgray.com/graynomad/wothahellizat/wot2/diaries/diary_06/index.php

i dont have an fg but i have drooled over the possibilities of a big ride like this. but i read robs whole blog and his diagram and explanation of the three point mounting was very interesting. that said my question is, where is the crack located? is this the truck with tool boxes and what looks like a slide in camper?

if it is i saw the damaged boxes, were they located anywhere near where this crack is? the reason im asking is i was wondering if there is enough flex where the frame and mounts are to allow movement with out binding.

maybe im way off base and if so im sorry for confusing the thread.

 

[pugslyyy]

http://robgray.com/graynomad/wothahellizat/wot2/diaries/diary_06/index.php

i dont have an fg but i have drooled over the possibilities of a big ride like this. but i read robs whole blog and his diagram and explanation of the three point mounting was very interesting. that said my question is, where is the crack located? is this the truck with tool boxes and what looks like a slide in camper?

if it is i saw the damaged boxes, were they located anywhere near where this crack is? the reason im asking is i was wondering if there is enough flex where the frame and mounts are to allow movement with out binding.

maybe im way off base and if so im sorry for confusing the thread.

I had to replace some boxes but that was due to hitting stuff. This crack is on the driver side and the damaged boxes were on the passenger side. I'm used to custom builds and understand that it is an iterative process - you do the best you can, but you also make adjustments as you go along and see what's working and what isn't.

 

[gait]

I'm with you on the twisting. I have a meccano model that demonstrates a rigid mount for the non pivoting bits is subject to some twisting effects.

As the rear twists (left-right) relative to the front one chassis rail has to be higher at the front than rear, the other lower. Eventually either the bolts will loosen or shear, or the steel give way.

Yup, one off is very different to repeated manufacture of the same model with improvements.

 

[mog]

Sorry to hear that
I could not find any detailed photos of the front mounts on Doug's webpage for the 3-point system (lots of the rear mount details)
Are the front mounts of the 3 point sub-frame bolted directly to the Fuso's frame, or is there any system of 'give' (springs, sliders, etc) at that mounting point ?
It looks like a direct no-give mount in this photo here : http://www.hackneys.com/mitsu/photos/buildup_album_03/image042.htm
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So is the crack in the subframe opposite of the original crack in the Fuso frame as shown below ?
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[pugslyyy]

Sorry to hear that
I could not find any detailed photos of the front mounts on Doug's webpage for the 3-point system (lots of the rear mount details)
Are the front mounts of the 3 point sub-frame bolted directly to the Fuso's frame, or is there any system of 'give' (springs, sliders, etc) at that mounting point ?
It looks like a direct no-give mount in this photo here : http://www.hackneys.com/mitsu/photos/buildup_album_03/image042.htm
-
So is the crack in the subframe opposite of the original crack in the Fuso frame as shown below ?
-

Yes, and it could well have occurred at the same time. The rust/bubbling of paint leads me to believe it happened some time in the past. The only way to detect it would be to take the camper off of the service body.

If it happened when the frame cracked near the passenger side front fixed load point that could explain why it hasn't propagated any more (since the frame crack that cause it has been repaired)

I already gave the frame a good once over, but I need to go back and take a closer look at the front fixed load point crack repair to make sure I'm still happy with the way it looks.

 

[mog]

If it is mounted like this at the front (all solid) ?

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Maybe (??) since the camper is off it might be a good time to put a little 'play' or 'fudge-factor' in the forward mounts.
It does not have to be something as fancy as new spring mounts. As you have said, it has survived (mostly) a trip around South America, but what about just slotting the holes in the mounting plate were it bolts to the Fuso's frame?
You could put a sheet of UHMW plastic between the frame and plate (it can be very thin, friction reducer only) and then have a spacer on each bolt so they can not be tighten too much.
You should be able to do all that with every thing 'in-situ', so not too much work.

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I might be looking at the existing mounting all wrong. If so, please disregard.
BTW- how did Doug eventually fix the frame? I know he had looked into an after-market frame replacement. Is that the route he took?

 

[pugslyyy]

There's not a lot of flex in the mount that I can see. As far as I can tell it is just bolted - though it is with a single bolt so that does doubtless allow a bit of movement. Doug may correct me on this - he's the only one who really knows!

Even though I have the camper off the service body, the service body is still firmly mounted on the Fuso chassis and at this point I'm not sufficiently motivated to pull the service body off of the frame.

The frame was repaired, not replaced.

A frame replacement would be a pretty big undertaking. If I were to look at something like that, I would probably be considering building up a new vehicle using parts from this truck and from my crew cab.

 

[k9lestat]

The system rob described in his blog was very effect and seemed rather simple

Sent from my SCH-I605 using Tapatalk

 

[pugslyyy]

The system rob described in his blog was very effect and seemed rather simple

Sent from my SCH-I605 using Tapatalk

Oh, I don't disagree. I'm just not currently motivated to disassemble my truck any more than it already is.

It's not implementing a solution that's complex, it's gaining access.

For example, I just did a simple gray water pipe repair (15 minutes), but it required over a full day of labor to access the compartment that the pipe was in.

Range Rovers are the same way P38 heater core replacement requires 12 hours of labor because you have to take the entire dash off of the vehicle. Actually replacing the core is really easy.

 

[mog]

There's not a lot of flex in the mount that I can see. As far as I can tell it is just bolted - though it is with a single bolt so that does doubtless allow a bit of movement. Doug may correct me on this - he's the only one who really knows!

Even though I have the camper off the service body, the service body is still firmly mounted on the Fuso chassis and at this point I'm not sufficiently motivated to pull the service body off of the frame.

The frame was repaired, not replaced.

A frame replacement would be a pretty big undertaking. If I were to look at something like that, I would probably be considering building up a new vehicle using parts from this truck and from my crew cab.

View attachment 220561

In that case, IF ACCESSABLE, I'd add reasonable (<2.0") doublers at the 4 welded areas of the subframe to help spread the 'forces' and not have them concentrated on the weld line.

 

[pugslyyy]

In that case, IF ACCESSABLE, I'd add reasonable (<2.0") doublers at the 4 welded areas of the subframe to help spread the 'forces' and not have them concentrated on the weld line.

Gotcha. In the morning I have to work on getting someone out to weld this up, thanks for the thoughts.

I've been over/under the frame and service body and that one crack is all I'm seeing. There were a few broken tabs that I fixed a while back but don't see anything new.

 

[pugslyyy]

I will be very surprised if it cracks here again.