Frame question??

[scottreb]

Hello All,
Im curious about the frames on these trucks. Specifically it appears there is a second frame rail that runs along another. Does this run the whole length of the frame or just under the bed? What is the purpose? Can it be removed? I understand a double frame that you see on HDT which has one c channel inside the other, but I have never seen a second on a bare frame.
Thanks for all the great info!

 

[scottreb]

I think I answered my own question. Found a video with the cab forward. I guess its just support for the bed. Seems the bed weighs several thousand pounds!

 

[gimpyrobb]

All beds have weight, but I'm pretty sure that bed is aluminum. I would think the (extra?)frame is to support any load carried, its not there to support the bed. Hard to picture what your talking about though.

 

[scottreb]

Its the second C channel that runs on top of and parallel with the true frame. Ive found some pics and vids now that show where it ends. Looks like it just unbolts.

 

[porkysplace]

Its the second C channel that runs on top of and parallel with the true frame. Ive found some pics and vids now that show where it ends. Looks like it just unbolts.

With the stock cargo bed it keeps the tires from rubbing , any bed you put on it without the channel will need to be tubbed out for the tires to clear.

 

[coachgeo]

much of same questions answered here

http://www.steelsoldiers.com/showth...moving-rail-from-under-bed)&highlight=chassis

 

[98G]

I can't figure out why you'd want to remove it...

 

[Lmtv772]

Again the frame rails are there for a reason and shouldn't be messed with. The designer spent more effort and money to have them there. They wouldn't do that just for the heck of it.
If you do a search here you can find some POS truck, that has been backyard hacked by a hobby 'mechanic' and is an 18.000lb lawn ornament now.

 

[scottreb]

Thats perfect guys, just what I was looking for.

 

[scottreb]

If you put a camper box on it lowers the height and CG by 6-8" which can be pretty significant.
I agree it was put there for a reason. Is the main frame rails not strong enough? Why doesn't it run the full length of the frame? The front axle carries more weight. I'm not arguing, just trying to hear the collective thoughts and learn. Was it put there to make the bed a certain height only? To clear tires?

 

[Lmtv772]

If you put a camper box on it lowers the height and CG by 6-8" which can be pretty significant.
I agree it was put there for a reason. Is the main frame rails not strong enough? Why doesn't it run the full length of the frame? The front axle carries more weight. I'm not arguing, just trying to hear the collective thoughts and learn. Was it put there to make the bed a certain height only? To clear tires?

To hear the thoughts behind it as facts, you need to get with the designers in Sealey TX. As for us we are all just speculating and online speculation plus $3 buys you a cup of coffee at Starbucks.
As far as my opinion is concerned, I don't think the frame would be weaker without the frame rail ( in the operating parameters of an LMTV). but Unless you change to smaller Tires (which has other consequences) the Box will come in contact with the rear tire, when the axle articulates off road.

 

[98G]

I'm sure the stiffness and strength are engineered for full load, with a decent margin on top of that. That doesn't necessarily mean you need that level of strength for your camper box.

Be cautious when altering CG in that clearance is taken into consideration for the tires when the suspension is at full flex, not just sitting level...

 

[coachgeo]

LOL, Wish had skills and brain power of such a "Hobby Mechanic" myself. Chemistry and Pre Med, Certified Machinist and Certified Welder, and presently keeping the various countries fleets of oil tankers, Fish tankers, Military vessels and similar huge machine marvels built and repaired in various places thru out the world.

 

[scottreb]

The camper box would need clearance for sure. That could be accommodated with an articulated mount, 3 or 4 pt.
I understand this is a discussion with opinions, but that is why were here to share and hear. I appreciate the input. At this point I am curious about the FMTV for a camper build. But they certainly have a lot going for them, so whats not to like!

 

[coachgeo]

...but Unless you change to smaller Tires (which has other consequences) the Box will come in contact with the rear tire, when the axle articulates off road.

and lower bed conflicts with lid of battery box. Wheelwells in the bed can solve tire contact issues if one wanted to go that route.

 

[coachgeo]

According to another thread in here the box mount system on the LMTV is a hybrid 3pt/4pt system. Hard mounts in each back corner to second C Channel on frame rail. A captured? spring mount on at least one corner of the front. Might be both corners. A search in here should find that thread and others.

try these.

http://www.steelsoldiers.com/showth...e-flex-question-compared-to-Unimog-frame-flex

http://www.steelsoldiers.com/showthread.php?152020-M1078-M1079-for-overland-camper/page2


For camper box..keep in mind the box construction you use to determine what is best route to go for mounting. If it is lightweight then go 2 or 3pt if it is very heavy duty go as OEM box mount set up. But do the research and decide yourself. Am no expert...

 

[Oxyacetylene]

According to another thread in here the box mount system on the LMTV is a hybrid 3pt/4pt system. Hard mounts in each back corner to second C Channel on frame rail. A captured? spring mount on at least one corner of the front. Might be both corners. A search in here should find that thread and others.

try these.

http://www.steelsoldiers.com/showth...e-flex-question-compared-to-Unimog-frame-flex

http://www.steelsoldiers.com/showthread.php?152020-M1078-M1079-for-overland-camper/page2


For camper box..keep in mind the box construction you use to determine what is best route to go for mounting. If it is lightweight then go 2 or 3pt if it is very heavy duty go as OEM box mount set up. But do the research and decide yourself. Am no expert...

That is only the M1079 (and maybe 5 ton with van enclosure?). The M1078 has no spring mounts.

edit: you said "box mount" and not "bed mount"..so mine was probably an unnecessary clarification.

 

[scottreb]

Most of the European and Aussie camper use the spring style mounts. I think Aus has it in the DMV requirements (whatever the term for thier DMV is). Have the box frame run on top of the truck frame and mount several sets of springs front and back, most with no fixed position, though they have the mount to control fore and aft movement. Its very simple and mounts the weight of the camper just at the LMTV bed weight is on the full frame length.

The 3 or 4 point systems are much more complex, have moving parts, and I feel place stress at just those 3-4 pts. Most body builder guides show how to mount a box, and it uses the whole frame rail, not a few spots.

This argument has gone on on forums since the beginning of time it seems. Suffice to say that, I believe, they both have benefits.

 

[coachgeo]

For what little it's worth.

Am thinking hybrid 3pt mount cause camper box will be a repurposed Travel Trailer and have nowhere near the structural integrity of OEM boxes. Granted no one will ride in camper though. Camper Box won't fair well being asked to flex as the chassis does. Thus need for allowing chassis to flex somewhat independent of the camper box.

Complete Sub frame C Chanel as used on the Beds and Boxes of LMTV will be used. Any subframe of Camper will be attached to that. My understanding is the most flexion occurs at the outer ends of the chassis thus point of pivot will be at arse end of truck chassis and fixed points more toward center of chassis. http://www.expeditionportal.com/forum/threads/25494-pivoting-frames-and-mounting-campers


This chop is of Bill Caids MB 1017A. I happen to like the camper box to be mounted opposite direction. Bill used a 2 pt mount but then again MB's Chassis are known to flex more than most. Allways have



Bill Caids............................ Bad Chop of idea am going to pursue

Void between Cab and Camper is ROP, Then similar to OEM- the Spare, Air Cleaner, and possibly Gen Set stuffed in there?

 

[scottmandu]

The LMTV was offered without a bed, so the second frame is part of the bed and not the truck.