M1088 maximum grade 30%

[Givinup]

Tm states max gradient for m1088 is 30% and all other models are 60%. Any idea why?

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[coachgeo]

Tm states max gradient for m1088 is 30% and all other models are 60%. Any idea why?

The 30 is side slope. It is still 60% for gradient. see https://fas.org/man/dod-101/sys/land/m1088.htm

 

[Givinup]

The 30 is side slope. It is still 60% for gradient. see https://fas.org/man/dod-101/sys/land/m1088.htm

Do you know if theres an updated tm. I've seen conflicting information, but this tm isn't for the A1 version of fmtv trucks. I pulled this from Liberatedmanuals.com

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[coachgeo]

Do you know if theres an updated tm. I've seen conflicting information, but this tm isn't for the A1 version of fmtv trucks. I pulled this from Liberatedmanuals.com
...g[/IMG) [/QUOTE] ya stump me on that one. Checked my 1998 TM for the 1084 and it shows same table as you posted..... odd. As you point out this contradicts other info. Is there a date listed for this TM from Liberated manuals? It should on front of TM at the bottom I think.

All I can think of is the concern for potential Break Over angle at top of climb. The longer chassis will maybe "high center"? This would potentially match with the lower gradient listed when loaded... cause the squat would change also break over angle / increase chance of a high centering event.

Now that think about it..... at top of gradient there is more potential for.... Cantilever effect (for lack of better term). When cresting top of gradient in a shorter based rig the front of trucks weight begins pulling upward on back of truck..... sooner than a longer chassis would. This loads/puts weight on front tires onto surface above crest sooner. A longer truck.... would take longer for weight of front end to lift rear of truck... thus keeping front wheels unloaded and/or possibly not even on the ground at all for a longer time period... talk about PUCKER FACTOR

Or Im full of illogical shiat in this guesstimate??

Maybe the actual gradient driving operating discussed in the manual gives further clues???

 

[coachgeo]

Break Over Angle. Some write up here https://jalopnik.com/this-is-what-makes-a-vehicle-unstoppable-off-road-512501606

 

[Awesomeness]

The 30 is side slope. It is still 60% for gradient. see https://fas.org/man/dod-101/sys/land/m1088.htm

I've been a little skeptical of that site. They have a lot of specifications on there that I have not been able to find from any other source. The specs are better than what the manuals and other sources say (that I can find), so I've wanted to confirm some of it before believing it. For example, they cite that you can double the carrying capacity on road, which I know I have seen in a manual for the previous generations of trucks, but I have never seen in any official military document (and yet it gets quoted here in the forums a lot too). The site also says you can ford 60" of water with a kit, which again is a thing from previous generations of trucks, yet I have never seen the FMTV kit, seen it mentioned in the manuals (after looking for it a little, and then just never coming across it while using the manuals for anything else).

 

[Givinup]

Break Over Angle. Some write up here https://jalopnik.com/this-is-what-makes-a-vehicle-unstoppable-off-road-512501606

Initially I thought the same thing, but the m1088 wheelbase is one of the shortest, at 161in.

Does anyone know if the frame or setup is any different? I'll have lockers in both rears, so I'm not worried about going up a hill, but not sure if mechanically something will be pushed past a limit at 40,50,60°

I assumed all fmtvs started the same and then had either longer rails, or other kits added to the same spec chassis.

But 60° vs 30/22° is a pronounced drop. Seems like there'd be a reason for it - - wish I knew what that was.

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[Awesomeness]

My guess is that the empty truck is fully capable of the 60°, maybe even more, but that the 30° has something to do with the flexibility of the hitch. Either the hitch can't bend that far, or one of the trailers this is designed to carry would hit something at that angle. You have to remember that they are writing these specs while staring at a list of all the things they foresee it trailering, and they are trying to make it idiot proof ("If we say no more than 30°, an unknowledgeable soldier can stick every trailer we know of on there, and it will still work.").

There is a link at the bottom of that spec page to the original government request/spec for the truck, maybe there is insight in there.

 

[Givinup]

My guess is that the empty truck is fully capable of the 60°, maybe even more, but that the 30° has something to do with the flexibility of the hitch. Either the hitch can't bend that far, or one of the trailers this is designed to carry would hit something at that angle. You have to remember that they are writing these specs while staring at a list of all the things they foresee it trailering, and they are trying to make it idiot proof ("If we say no more than 30°, an unknowledgeable soldier can stick every trailer we know of on there, and it will still work.").

There is a link at the bottom of that spec page to the original government request/spec for the truck, maybe there is insight in there.

I'll try and do some more digging. They do spec 22° for when towing a trailer, which seems odd to clarify only 8° more without a trailer

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[snowtrac nome]

I don't have it in writing, but there are 2 factors come to mind, running bob tail with no weight over the rear drivers traction is going to be an issue. Load the truck down with a 40 foot trailer and now you have articulation limitations from the 5th wheel hitch, plus it has a much higher pay load with the same engine output, it's naturally not going to have the reserve power of a cargo truck.

 

[Givinup]

I don't have it in writing, but there are 2 factors come to mind, running bob tail with no weight over the rear drivers traction is going to be an issue. Load the truck down with a 40 foot trailer and now you have articulation limitations from the 5th wheel hitch, plus it has a much higher pay load with the same engine output, it's naturally not going to have the reserve power of a cargo truck.

That makes good sense to me. Thanks for the input

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