Well, I broke it.

[pugslyyy]

Just to point out to anyone who has not read the whole thread, pugslyyy's frame is a custom build frame, NOT a factory Fuso frame. You should not weld directly to the Fuso's factory built frame. You would build (weld) the mounts as separate units and then bolt them to the factory frame.

Absolutely correct. Since we are fabbing the mounts on site it works out to be easier to just weld it on, but that's not an option with a stock frame which is not weldable.

 

[Gatsma]

4 attachment points per side, the forward one is a hard point, the rest are sprung.

Thank you! Looks like it oughtta work, especially with your NEW, much-stronger frame!
Also(on edit) could you or someone here clarify on what happens when welding anything to a Fuso FG frame? What actually fails; the weld itself, the frame material, or both?

 

[pugslyyy]

Thank you! Looks like it oughtta work, especially with your NEW, much-stronger frame!
Also(on edit) could you or someone here clarify on what happens when welding anything to a Fuso FG frame? What actually fails; the weld itself, the frame material, or both?

I'm not a metallurgist so i don't know what the failure mode is. I suspect it makes the frame more brittle.

 

[gait]

the original Fuso frame is high tensile steel. I don't know the spec, probably low alloy. I'm guessing Pugslyyy's is mild steel.

Several mechanisms for failure, possibly most common would be in the heat affected zone around the weld. More likely in welding the high tensile steel. Simplistically the heat near to the melted bit of the weld changes the crystal structure which then may act like a notch or a sharp corner for cracking, plus the weld metal isn't quite the same composition as the host metal.

Mild steel isn't immune, just not so critical.

 

[pugslyyy]

I actually think it is the other way round. My new frame is expensive HSLA 80ksi steel. Stock frames are made of inexpensive (lower strength and thinner) steel.

 

[Gatsma]

Uh-oh, looks like a debate in the making........;-)

On edit- Or maybe not; looks like Gait has some good answers (as usual) below-

 

[gait]

Always good to have the specs.

Probably tensile strength 440MPa Original vs 550MPa Puggslyyyy
Roughly HSLA 65 vs HSLA 80.
Both HSLA = high strength low alloy steels (low carbon 0.21% C original 0.18% C Puggslyyyy, about 1.5%Mn and 0.30% Si original 0.60% Si Puggslyyy). There's possibly small difference in micro-alloy elements.
Hot rolled (not controlled rolling as far as I can determine so no heat treatment implied).
A bit of translation required for ASTM vs JIS standards.
Reasonable fatigue resistance.
Good weldability.

This link is for completeness - useful for those who need it, but its got lots of pages with useful drawings, and a reference to the JIS steel spec for chassis in the chassis bending modulus diagrams.
www.mitfuso.com/content/documents/pdf/archive/08-fe-bbd-part2.pdf

There's also a possibility that older chassis use different steel but since the thickness hasn't changed that's probably unlikely.

All for info only, no warranty!

The issue of "should I weld" is possibly more related to the application than the steel.

 

[pugslyyy]

The new frame is 80ksi yield. a656 but pretty sure that the stock frame is only 44ksi yield.

 

[gait]

The new frame is 80ksi yield. a656 but pretty sure that the stock frame is only 44ksi yield.

it'll be in your doco somewhere,

I read it in the fuso document I linked to - I guess that's why I linked to it.

65 ksi

 

[pugslyyy]

it'll be in your doco somewhere,

I read it in the fuso document I linked to - I guess that's why I linked to it.

65 ksi

Yes, 44k is what it says in my docs for an 07 FG. That's why I'm pretty sure.

 

[gait]

Yes, 44k is what it says in my docs for an 07 FG. That's why I'm pretty sure.

which page of what are you on?

its probably a standards and units thing. JIS do it differently.

Probably tensile strength 440MPa Original vs 550MPa Puggslyyyy
Roughly HSLA 65 vs HSLA 80.

 

[dlh62c]

4 attachment points per side, the forward one is a hard point, the rest are sprung.

You'll need the fixed mounting points the way your torsion mounts are designed. I see forward, backward and side-to-side shear forces on the spring bolts without them.

Are the spring bolts Grade 8?

 

[pugslyyy]

which page of what are you on?

its probably a standards and units thing. JIS do it differently.

Probably tensile strength 440MPa Original vs 550MPa Puggslyyyy
Roughly HSLA 65 vs HSLA 80.

I'm just going from the us sell sheets where in the specs it says 44ksi. That's nowhere close to a656 65ksi.

 

[gait]

whatever

 

[pugslyyy]

You'll need the fixed mounting points the way your torsion mounts are designed. I see forward, backward and side-to-side shear forces on the spring bolts without them.

Are the spring bolts Grade 8?

View attachment 249414

There's some more work to be done on stability for sure.

I use grade 5 hardware, not grade 8.