Buckstopper's FG Build

[Buckstopper]

Bed articulation

Here's another from OX13 today. These humps were set up to cross axles. There were more than a few rigs high centered or dragging their rear ends in the dirt. Look at the bed articulation. We couldn't get a wheel to lift on these humps

 

[pugslyyy]

Very nice setup, and very similar to what I have in mind for my crew cab build (though it will have to be a 12' bed). I don't think I'm going to have the same luck finding a cheap Alu bed as you though!

 

[Buckstopper]

Very nice setup, and very similar to what I have in mind for my crew cab build (though it will have to be a 12' bed). I don't think I'm going to have the same luck finding a cheap Alu bed as you though!

Thanks. I am finding photos of the truck all over the place. This is from Hallmarks face book page.






The photos of the truck going through the mogul field really show the articulation of the bed. I am glad I was driving the truck and not watching someone else drive it...it looks like its going to twist in half! Looks like the camper overhang is hitting the tunnel box but it just kissed it if anything. There are no marks.

As for the bed, it is made by Aluma. It is fairly light duty but the camper isn't putting a lot of stress on it. The boxes are all Protech and they make a really nice bed. You might take a look at their products. The welds are truly beautiful.

Buckstopper

 

[Overland Hadley]

That is some impressive flex.

How did you end up mounting the flatbed to the frame of the truck? And how is the camper mounted to the flatbed?

 

[SkiFreak]

Freight trucks, and the like, get away with hard mounting the boxes on the rear because driving on sealed roads does not cause the chassis to flex excessively. A Canter intended for off road use is a totally different story and cannot realistically be done in the same manner, as the environment in which it will operate is quite different.

I do not profess to be an expert in regard to mounting systems for camper bodies but using some basic logic I believe that allowing unrestrained flex of the chassis is as bad, if not worse, than hard mounting.
When a camper body is hard mounted it tends to focus the stresses and, in a Canter with a stepped frame, this is normally just in front of the step. This will naturally increase the potential of cracks in this area if the chassis is twisted a lot, as it would do in more harsh off road scenarios where wheel articulation is greater. Conversely, if the chassis is allowed to freely flex, this will place additional stresses on the chassis welds and rivets, which can also be detrimental.

In my opinion, for what it's worth, the chassis should be allowed to flex independently of the camper body but it should also be constrained, so it cannot flex too much.
This is why I believe that a fully spring subframe mount is the best solution for a Canter. The springs allow for the chassis to flex independently of the subframe but at the same time, they stop excessive chassis flexing.
Changing the suspension to something that allows more wheel articulation will also reduce stresses on the chassis.

 

[Buckstopper]

In my opinion, for what it's worth, the chassis should be allowed to flex independently of the camper body but it should also be constrained, so it cannot flex too much.
This is why I believe that a fully spring subframe mount is the best solution for a Canter. The springs allow for the chassis to flex independently of the subframe but at the same time, they stop excessive chassis flexing.
Changing the suspension to something that allows more wheel articulation will also reduce stresses on the chassis.

The truth is spoken here! The question is how much is too much? Here is a video of the truck going through the OX13 cross axle course.http://www.youtube.com/watch?v=dSMj6CHTs48#

Thanks Eric for posting this video!

This was the mild course. The Land Rover course was much more severe - especially the mogul field as the photos above show. Is this too much flex? Probably yes if it was driven through this terrain all the time. It would eventually suffer fatigue cracks and fail. The reality is that most trucks - mine included - don't see this action all the time.

I used the spring mounting details out of the AU truck regulations. Here's a photo:

The deflection was measured by jacking opposite corners of the truck with no springs - just bolts in the bracket and measured how far it moved. I added about 20% for bounce and figured that was a good start. The mystery is how to calculate or measure the appropriate spring rate. Since i measured each bracket locations deflection I tried to find a set of springs that would result in about the same force at the maximum deflection of each location so that no single bracket was doing more work that the rest of the pack. I also figured I would start light and move to heavier springs if it was too "floppy".

I can say that at slow speeds this pack of springs works well. However, if I hit a bump hard the camper does flop to one side a bit. I found this a bit unnerving first in a parking lot where I cut a corner a bit tight and drove over a curb with the inside set of rear tires going at normal parking lot speed. The camper tipped to the outside pretty quickly which was a surprise. Is it going to tip over? No. The CG is really low. Is it a bit spooky? Yes. I figure I will stick with this set for a while and may move a bit stiffer if it is a problem. It is not a problem at normal speeds and normal conditions. I do not see it move very much during normal cornering.


For what it is worth I crawled under the commercial campers that had spring isolators (I wont say which) at OX13 and they used the next heavier spring but did not have as many springs along the frame rail as I did.

I have spent some "quality time" on my back under the truck after getting home from OX13 and I don't see any damage or displacement of brackets or anything else out of place so I am very pleased with how the truck worked.

 

[Buckstopper]

Subframe

Here is a shot of the subframe before it was fully mounted on the truck (test fit):


I used an oak spacer between the subframe and frame so there is no metal to metal contact. You can see the spring brackets without the springs and bolts. What you can't see is the rear connection. I used the original bumper mount laying on the floor in the photo and welded that to the sub frame. The bumper brackets are then bolted to the frame. This fixes the subframe to the frame at the rear of the truck. It is restrained from shifting forward in an front collision and falling off of the frame under the awesome Fuso warp drive acceleration :Wow1:

 

[Buckstopper]

Tunnel Box Dimension

There has been some comments about how close the camper overhang comes to the aluminum tunnel box behind the cab...

Here's how I figured that out:



Before I ordered the box I mocked up full deflection (with springs this time) and measured how much space I had. I allowed a bit more room for bounce and placed the order. The box is mounted with springs so it does move as well.

 

[Buckstopper]

Spare tire mount

The last thing I got done before heading to OX13 was the spare tire mount. I literally had to wait for the paint to dry to get it mounted so I could leave. Here is the finished product.

Cab tipped:

Cab Down


This is the only thing that is hard mounted to the frame. It barely fits so I riveted some UHMW plastic rub pads to the tunnel box. You can't really see it but my hilift jack is mounted here as well but I separated the base and handle from the post. You can see the base where the braces intersect. The handle and post are under the tires. it all fits. At the last minute I noticed how nicely a light mounted on top of the rack would illuminate the engine so I added that. Still need to get it wired up.

Buckstopper...

 

[Buckstopper]

More deflection photos

These photos mysteriously arrived by email today. Thanks Honey whoever you are!

This is a really interesting sequence from pretty much full deflection to flat.





How much deflection is too much??

Note the camper overhang to tunnel box relationship. It didn't appear to touch although it sure looks like it in the photos. There are no marks on the camper. It works but I think I will add a pad under the camper and that will raise the camper slightly. I also have a wood spacer between the tunnel box and truck frame that can be changed out for thinner wood or rubber.

I have to say again after seeing these photos that I am glad I was driving and not watching! I would have figured that I was going to have to walk back to Oregon from Arizona because my truck broke in two!

All for now.

Buckstopper.

 

[SkiFreak]

From all that you have posted it appears that you have a good handle on things.

How much flexing is too much? Now there is a contentious question. Here is my take on this subject...
I have fairly heavy springs on my subframe as I want to limit the flex to about a 30mm lift at any of the mount points. I also have coil suspension on my truck, which should mean that a lot more flexing should occur in the suspension resulting in less twist being applied to the chassis.
As I mentioned previously... I believe that too much flex is as bad, if not worse, than hard mounting the subframe to the chassis. Like yourself, I have taken a "best guess" approach for my setup, knowing that I can replace my springs for softer or firmer ones if the need arises. No matter how much pre testing you do, real world driving, like you did at OVEX, is the ultimate test.

The one thing that I would change (modify actually) in your setup are the angle brackets for your spring mounts. I would add some gussets to the angle brackets so that there was minimal chance of flex/fatigue in them.
But maybe that's just me....

 

[Buckstopper]

The one thing that I would change (modify actually) in your setup are the angle brackets for your spring mounts. I would add some gussets to the angle brackets so that there was minimal chance of flex/fatigue in them.
But maybe that's just me....

Not just you. I've scratched my head over that. My question and concern hasn't been over the bracket but over the frame. The bracket is over 2x the metal thickness as the frame. What is that doing to the frame? I would rather have some give in the bracket that have a hot spot in the frame. That is part of the reason that I went with a softer spring. Less force to bend either the bracket or ultimately the frame.

Most of the subframe was built from junk from my scrap pile. Those brackets were scrap clips that were designed to hold huge pieces of precast concrete on a building. I had a pile of them so I went that direction. Free material and wife is happy that my scrap pile got smaller. That's a win win.

The holes are a bit over sized and they are elongated. I have large washers between the spring and the bracket so the bolts can move around a bit to avoid binding up. I don't have a photo of them but there are also some alignment plates with UHMW plastic to keep the frame and subframe in line so the bolts don't get bent. I looked at the ex army Duce-and-half trucks at Expo and they had the same set-up but double springs (more force on the bracket and frame).

My front spring has the most deflection. The spring is rated for 2" of deflection so I am allowing a bit more movement than you are. My theory is let it have room to move and use spring rate to slow it down to a soft stop rather than have shorter throw and a hard stop. I figured a hard impact would be bad all the way around. Hence I have some crazy deflection in the mogul field.

I agree with your comment about putting the flex in the suspension so the frame isn't doing the work. Mine is stock. I haven't mentioned this but I talked Alan at Sportsmobile into letting me drive the ATW suspension and super single equipped Fuso that they had at expo late in the day on Sunday as everyone was packing up. I drove around the camp area which wasn't as rough as the course but was pretty rough. I could see that the truck and camper stayed much more aligned than my truck did which means the suspension was doing more of the work. It was a really nice ride. They are selling that system here in the states now so it is probably the best option for a suspension upgrade here.

Thanks for your comments. That is why I am posting here so I can get some feedback from those of you that have done this before.

Buckstopper

 

[SkiFreak]

I have a similar scenario in that my mounts are made of heavier material than the subframe they are welded to.
What I did was to have a cross member inline with each mount, which strengthens the area more around the mounts. If you look at the suspension mounts you will see a similar setup on the chassis to this.
That's why if you move the suspension mounts you should also move the cross members.

 

[Buckstopper]

Interesting. There is a diagram in the Fuso Body Builders manual that has a cross hatched area around each cross member that is a no-load zone so I tried to avoid those zones for my spring brackets. I'll see if I can find that drawing and post it.

Buckstopper

 

[SkiFreak]

Are you talking about this diagram?



This is a guide to where you can and cannot drill additional holes in the chassis.
For my mounts I utilised existing holes in the chassis. I did not drill any new ones, although I did remove a couple of rivets in order to space the mounts evenly along the chassis.