tilt/rollover point

[texas-5-ton]

I can't logically figure this one out so I need some help from the gurus. As many of you know, our FD has purchased this M813 for a brush truck. Our water tanks are two, 600 gallon military fuel pods that are designed for these 5 tons (or M35's). So combined, you have 1,200 gallons of water on the truck. What I am trying to figure out is how much can the truck lean (in degrees) to either side before being in danger of turning over (full of water). I did a search but can't come up with anything. My concern is that since this thing will have a high center of gravity that it will be quite susceptible to turning over on the fire ground. If I can figure out (with your help) how to calculate this, I plan on putting a "Lev-O-Guage" in the cab to help warn us of such a condition. (Although I hope that pucker factor will prevent this from ever happening). Thanks for the help..

 

[Towman2277]

I do high risk recoveries and can calculate this for you with some software that I have in the office. First i'll need a few pics of the tanks to show placement and shape, and some measurements. I'll need your tire width across the rear (width of rearend with tires, measured to outside edge.) and i'll need a measurement of how high your tank bottom and centerline are measured from the ground up. If you can get these and email to steveyoungtowing@bellsouth.net I can get you a very accurate angle measured in degrees.

 

[texas-5-ton]

Steve,
Bless you brother!! I will get this for you as quickly as possible. The truck and tanks are out of town right now but I should have it back later this week. Thanks again. I REALLY APPRECIATE IT !!

Chad

 

[Towman2277]

Just let me know. When we have a rollover situatation we respond to (ie. Gasoline Tanker, etc) we correspond back to the office with different weights, measurements, hill angles, obstacles, etc and we can be given a VERY ACCURATE chart that says exactly when we will reach the positive 1 position (in degrees), Nuetral balance position (about to roll), and negative 1 position etc, ( she's rolling, MOVE). It's really cool software. I'll keep and eye out to get all the info from you. Steve

 

[texas-5-ton]

YOU THE MAN !! This is exactly what I was looking for. I owe you one !!

Chad

 

[M1075]

Chad-

If you find the side slope capability too limiting, you might want to try mounting the tanks on the frame instead of in the bed. That moves the weight down a lot lower. I have seen several M818s mounted that way. Keep in mind that rollover potential is impacted greatly by tanks with partial loads. Good luck with the project.

 

[emmado22]

the 600 gallon pods are RARELY baffled. No baffles = much higher risk for live load shift=easier to roll over..

 

[cranetruck]

Check out article in issue 87 (Oct 2001) of MVM.
The biggest problem would be sloshing like Emmado points out. The military calls for 1/2 the load for off road.

The inclinometer can be purchases from Westmarine.com, about $20.

 

[DDoyle]

Bjorn,
Do your calculations not also assume the conversion from 9.00-20 to 11.00-20, in addition to singling the tires out?
I dunno of the original poster has single or duals - or their sizes - on his five ton.

Regards,
David

 

[jasonjc]

As far as the half load I'm not shure about the "pods".But in the tanker trucks the TM says to fill the front tank only for the 1/2 load.Not 1/2 in ea tank.

 

[rmgill]

The dynamic nature of the water in the tanks will make a fixed number difficult with a partial load. How you drive the truck in such a situation could also impact that. Cut the wheel sharply at the wrong point and you could have the water shift the truck beyond it's tipping point.

 

[texas-5-ton]

I do plan on putting an inclinomater or LevO Guage in there like in the pictures posted above. The truck does have duals on the rear and they are 11X20's. Since the tanks are elliptical, is the side to side slosh going to be a big problem?? And like Ryan and Emmado is saying, if your tank is not completely full, there can be load shift that could put it on it's side. Eventually, I am going to do away with these aluminum tanks and get a poly tank custom made with a lower center of gravity, that won't stick up as high.

 

[M1075]

Are you building this truck in accordance with NFPA 1906 for Wildland Engines? I think NFPA 1906 limits the center of gravity to 85% of vehicle's track.

I wouldn't expect any problems with 2 600 gallon fuel pods on a standard M813. You can always remove the bed and put the tanks on the frame if you want peace of mind. That will help a lot. I have run a deuce up on the left tires only, and there is definitely a little hershey factor that sets in!

 

[cranetruck]

With open diffs the side slope capability will be limited because of traction. A loaded deuce may not be able to handle anything over 20% when the load is shifted to the downhill side wheels. Don't know the numbers, but it will loose traction before rolling over, I'm pretty sure of that (unless you happen to run into a big dip/ditch or something).

 

[texas-5-ton]

We plan on leaving the bed on the truck but I definately agree with you general on setting the tanks directly on the frame. I was going to put a picture on here but cant figure out how ..