Fuso FG frame specs

[dhackney]

I've been doing some research on replacing the rear section of our FG frame.

I thought this info might be of interest.

Notes:

• Web = the vertical portion of the frame
• Flange = the horizontal portion of the frame
• Sleeve = additional reinforcement placed inside the frame
• RBM is used to compare frames of different sizes, shapes and strengths.

Note that the rear section of our frame is extended, so the weight delta is different from a stock frame.

Info on the frame and crossmembers is here: http://www.hackneys.com/mitsu/docs/fusoframemodificationinfo.pdf

Info on the stock frame modulus is here: http://www.hackneys.com/mitsu/docs/fusoframesectionmodulus.pdf

Info on reinforcing the FG step-down section is here: http://www.hackneys.com/mitsu/docs/fusoframeFGreinforcement.pdf

Replacement frame info is from P.G. Adams http://www.pgadams.com/truckframes.php

Quoted cost for two 80k PSI rails for our length (longer than stock) is ~$1,600. Cost of drilling holes to match the stock frame varies depending on the number of holes. If you match every hole you can spend as much for the drilling as for the frame rails. (Quote is based on constant height rails with the flanges cut down to match the stock flange width)

The process is to ship them the stock frame section so they can match the holes. They ship the new frame back. Total turnaround is a few weeks including ~two weeks of shipping time. Freight both ways from TX to VT to TX is ~$1,000.

The stock FG frame is C channel.

The stock FG's frame is riveted together at the step-up junctions.

The stock FG frame tapers from a point near the forward rear leaf spring hanger to the tail. The web height diminishes from 7.486" to 5.378".

Highlights:

• The stock rear section is 188k RBM at its strongest point.
• An 80k PSI replacement frame is 459k RBM.
• The step-up junction section is 482k RBM.
• The stock step-up section is 295k RBM (with no reinforcement).
• The front section, which has a stock sleeve, is 305k RBM.

 

[kerry]

It'll take a while to digest all those numbers. When you say you are replacing the rear section of the frame, are you talking from the back/bottom of the step-down to the end of the frame?

Does anyone know the rationale for the original diminishment in height of the frame towards the back? Do other trucks typically do this or is it unique to the FG?

 

[haven]

I think that, rather than stepping down at the rear, the frame steps up at the front to make room for the transfer case and front drive shaft. The raised frame section also provides a higher location to mount the front suspension, adding wheel travel. The frame for the Fuso FE with rear wheel drive is quite different than the FG frame.

Fuso provides a truck body builders' guide that includes dimensions of the frame. Download the PDF here http://www.mitfuso.com/Content/Documents/pdf/Archive/08-FE-BBD-part2.pdf

Here's a photo of the FG frame in the foreground, FE in the background. There is more space between the top of the front wheel and the bottom of the door on the FG.

(In the rear of the background of the photo, there's a Fuso heavy truck showing off its bridge truss-like frame.)

 

[DzlToy]

Im not an engineer but I never got the stepped frame thing. Sure MFTB would not do something so monumental as engineer and build a new and separate frame just to give the transfer case a place to hang. A simple clocking ring or adjustment in the bolt patter to make the transfer case flat would solve this issue and it would not hurt to do this anyway. Makes the belly flatter giving more ground clearance for off roading and the driveline should not care ALA there arent any crazy angles going on.

Additionally, the stepped frame makes the cab sit higher, which changes CoG and handling. Not to mention the fact that it looks ridiculous with that huge wheel gap...

 

[dhackney]

When you say you are replacing the rear section of the frame, are you talking from the back/bottom of the step-down to the end of the frame?

Yes, from the bottom of the step-up to the tail.

 

[kerry]

Im not an engineer but I never got the stepped frame thing. Sure MFTB would not do something so monumental as engineer and build a new and separate frame just to give the transfer case a place to hang. A simple clocking ring or adjustment in the bolt patter to make the transfer case flat would solve this issue and it would not hurt to do this anyway. Makes the belly flatter giving more ground clearance for off roading and the driveline should not care ALA there arent any crazy angles going on.

Additionally, the stepped frame makes the cab sit higher, which changes CoG and handling. Not to mention the fact that it looks ridiculous with that huge wheel gap...

Since the front driving axle raises the whole truck compared to a 2wd FE, it's a choice between keeping the frame level and dropping the real axle low below the frame or stepping down the whole frame in the back.

 

[whatcharterboat]

I think that, rather than stepping down at the rear, the frame steps up at the front to make room for the transfer case and front drive shaft. The raised frame section also provides a higher location to mount the front suspension, adding wheel travel. The frame for the Fuso FE with rear wheel drive is quite different than the FG frame.

Yes Chip. ALmost.

Im not an engineer but I never got the stepped frame thing. Sure MFTB would not do something so monumental as engineer and build a new and separate frame just to give the transfer case a place to hang.

The FE and FG do share the same frame. It's not a completely re-engineered frame but an FE frame that's been cut in half and the step has been riveted in place. So rather than have a completely new frame they only add in the step. Fuso must have decided that was the most efficient way.

Slight side track >>>> Isuzu always went for stronger (and heavier) frames and went for one piece chassis rails on previous NPS models with the steps formed into the rails rather than as an added section into the old NPR frame. Interesting that as of 2008 they ditched the whole "step" idea and went for straight rails common with the NPR and simply packed up the rear suspension to keep it level on the NPS. BTW they are 850mm wide all the way and not tapered back to 750 like the FG too. Good move IMO ...not packing the suspension but having them 850mm wide.


Hi Doug ........Long time........how are ya? Hey, when are you and Steph going to bring that GS over and do Cape York ? John.

 

[dhackney]

BTW they are 850mm wide all the way and not tapered back to 750 like the FG too. Good move IMO ...not packing the suspension but having them 850mm wide.

Agreed.

Hi Doug ........Long time........how are ya? Hey, when are you and Steph going to bring that GS over and do Cape York ? John.

Long time -Yes, too long.

Been focused on other things for a bit.

We may have some time to travel again soon.

 

[Amesz00]

Additionally, the stepped frame makes the cab sit higher, which changes CoG and handling. Not to mention the fact that it looks ridiculous with that huge wheel gap...

the weight of the cab would have a negligable effect on COG imo. there isnt alot of weight in them. at least the higher cab makes it look like a 4x4. as for the wheel arch gap- "whats that Mr Bishi? you designed this with the specific intention for me to run 40" XZLs? why thank you Mr Bishi, i think i might take you up on that..."