Water weight

[o1marc]

Originally Posted by ol trunt

Next time you pull up next to one of those driveway car wash guys with the Harbor Freight trailer loaded with 100 gallons of water--watch closely as he tries to stop for a light. The tow vehicle and the trailer try to stop but are then pushed forward by the still in motion water. Its like creating your own tsunami.
Jack

You make it sound like all that water is packed against the back of the tank during travel and it doesn't move to the front of the tank until the vehicle stops. I used to carry a 100g water tank in the back of my F-150 for pressure washing, had no problems driving or stopping no matter how full/empty they were.

[gs1949]

I'm still looking at water tanks myself. Some of them are quite long, 6 feet or more. The small cross-section of these longer tanks would make them easy for me to fit in, but having something that long makes me wonder about damaging the tank or its connections.

I'm concerned about this because I have experienced a sloshing tank. I used to drive a tank truck for the Yukon Forest Service. It was a 1961 FWD, which was basically a 10 ton International with a front differential and a transfer case that had a vacuum operated control to engage it.

I quickly became the principal operator of this truck. Most of my colleagues were a little younger than me and totally clueless about how to shift a non-syncromesh transmission. That truck had a 1,000 Imperial gallon, unbaffled tank. We had a rule about never moving the truck when it was not either completely empty or completely full.

The only exception was once a week when I went to water a few thousand pine seedlings. That was on a smooth gravel road that saw very little traffic and I never took the truck out of first gear until the tank was empty, so there were never any problems there.

However, on a fire I fudged once and moved the truck about 200 feet when it was about 3/4 full. I decided it was an operational necessity. The wind shifted and we needed to move. I didn't want to waste the water, because we needed that too.

This was not on a smooth, flat road like at the pine nursery. It was just a bush trail, on a bit of a sidehill. I had to drive over a pine tree that had fallen across the trail. We didn't have a chainsaw, nor did we have enough time to mess around without one. And it wasn't a big tree, less then 2 feet on the butt, maybe 12 inches in diameter where I had to drive over it. So I drove over it going as slowly as I could, but I felt that slosh, twice, and wouldn't want to go through even half that much sloshing at road speed, even 20 mph.

Now, I do realize that 1000 Imp gallons is a lot more water than any of us will be carrying, but I think that even 50 gallons sloshing back and forth for a few years might eventually crack the tank and cause it to leak. So now I think I will plan to include 2 or 3 square tanks and then move on to worrying about something else.

[ol trunt]

01marc. My comments were based on an understanding of Newton's first law of motion which may be paraphrased "Things in motion tend to stay in motion". When the water tank abruptly (or even slowly) stops, the water contained therein continues forward at its initial velocity until it "hits" the front of the tank---and expends its stored energy against the front of the tank. Next the tank now energized does the same thing to the vehicle. Whether or not you personally were able to feel these shifts in momentum they were happening just the same.

Here is a tidbit from NASA remarking on Newtonian physics. There is also a kids page with great drawings.
https://www.grc.nasa.gov/www/k-12/airplane/newton.html.
Jack

[gs1949]

And there's another Newton's law about every action having an equal but opposite reaction, which refers in this case to the waves inside the tank that keep banging back and forth until the energy dissipates or more energy is added. So your tank takes multiple blows on 2 sides from each slosh.

[Joe45]

This bus has a large diesel tank on the "passenger side" and it had a really heavy hydraulic lift right over it, along with a honkin big battery on that same side, yet even empty, I saw and noticed zero effect on the bus: leaning etc. because of the weight, etc. This bus also transported kids that sat from about the center back with a couple of rows of seats and the rest for wheelchairs.



The more I think of it, the more it seems these things are meant to handle these weights and imbalances.



Yeah, a 100 gallon tank of water will be 800+ pounds, but even on one side, I can hardly see this having much effect on this vehicle.

[TheHubbardBus]

'Can handle' and 'optimum' are two very different things. The fact the weight may have been imbalanced while in service as a school bus doesn't negate the fact that it had to have had a detrimental impact on handling, tire wear, etc. The question is how much of an impact. Maybe not enough to even notice during normal conditions. But what about when things get dicey and you find yourself right on the limits of traction?

[Joe45]

Originally Posted by TheHubbardBus

'Can handle' and 'optimum' are two very different things. The fact the weight may have been imbalanced while in service as a school bus doesn't negate the fact that it had to have had a detrimental impact on handling, tire wear, etc. The question is how much of an impact. Maybe not enough to even notice during normal conditions. But what about when things get dicey and you find yourself right on the limits of traction?

I'd say the same as when carrying a bunch of students and things get dicey and you find yourself right on the limits of traction.

The bus has 160,000 miles or so, with no problems and no issue with tire wear etc. These things are way overbuilt and I really think we are getting a bit paranoid. It's not like I'm going to add 800 gallon tanks on one side or the rear. We're talking at worst 2000 lbs of water, with a 400-500 lb lift removed, seats removed, two to three passengers tops, and some furniture. The bus is already way under weight from when I bought it. Lets say I add 4,000 lbs total in the build. I say it's still built to handle that easily.

[Sleddgracer]

Originally Posted by o1marc

You make it sound like all that water is packed against the back of the tank during travel and it doesn't move to the front of the tank until the vehicle stops. I used to carry a 100g water tank in the back of my F-150 for pressure washing, had no problems driving or stopping no matter how full/empty they were.

I didn't notice the same thing - lol - a 250 gallon tidy tank in a trailer hooked to the back of my one ton on duals ( no trailer brakes ) - didn't feel any surge at all

[PNW_Steve]

Originally Posted by o1marc

You make it sound like all that water is packed against the back of the tank during travel and it doesn't move to the front of the tank until the vehicle stops. I used to carry a 100g water tank in the back of my F-150 for pressure washing, had no problems driving or stopping no matter how full/empty they were.

My experience has been similar.

When I built my first bus I was concerned about not being able to find a water tank that had baffles. I looked at what others were doing.

I went ahead and installed a 200 gallon tank without baffles. No problems in 250k miles.

I carry 55 gallons in my pickup bed. No baffles, no problems.

[Rivetboy]

Originally Posted by o1marc

That's like 16 students body weight. If your bus had 4 seats behind the axle, you won't exceed what was there originally.
I'd hate to have 1600lbs on the back end if that pendulum if the bus was empty

My bus had a wheelchair lift all the way in the right rear corner and the 60 gallons of fuel on the passenger side plus the weight of the fuel tank crash barrier which was at least 400 lbs. I am planning my grey water tank between the frame rails behind the rear axle. My feelings is after removing the crash barrier and the wheelchair lift my grey water tank will weigh less than what was removed and centered over the axles. I also moved the fuel tank to the drivers side and the batteries, generator fuel and honda eu2000 to the passenger side. Will weigh each wheel when final weight and balance comes up we shall see. This is a 28 foot bus.

[Rivetboy]

Originally Posted by Rivetboy

plus the weight of the fuel tank crash barrier which was at least 400 lbs.

This sucker is heavy . It weighs at least 400 lbs My buddy and myself slid it to this corner we could bareley lift it. Guessing it is 1/2 wall thickness. Gave it away so it did not have to be moved again.

[Joe45]

I like the idea of a crash barrier for the fuel tank. Seems like a good safety feature. But the other side of it is if it's that heavy! 400lbs?! 1/2" wall tubing?
I'm sure a replacement one can be fabricated that has 3/16 wall or even 1/8" which would work well.

Also, I just thought of the big 18 wheelers and their dual tanks with no crash barriers.

[TheHubbardBus]

Originally Posted by Joe45

Also, I just thought of the big 18 wheelers and their dual tanks with no crash barriers.

Nobody cares if a trucker or two goes up in flames. When it's a bus full of school children, though, that's bad publicity.

Disclaimer: In case my dark humor is taken the wrong way, I don't really think either case would be the least bit funny.

[Joe45]

Originally Posted by TheHubbardBus

Nobody cares if a trucker or two goes up in flames. When it's a bus full of school children, though, that's bad publicity.

Disclaimer: In case my dark humor is taken the wrong way, I don't really think either case would be the least bit funny.

HOW DARE YOU MAKE SUCH A CALLOUS STATEMENT?!?!?!!


Just kidding!




You're absolutely right.
That's why these buses are so overbuilt, which is good!


But what do you all think? If the crash cage is really that ridiculously heavy (is it?) wouldn't it make sense to remove it altogether, or make a lighter version which is still strong?

[Rivetboy]

Originally Posted by Joe45

I like the idea of a crash barrier for the fuel tank. Seems like a good safety feature. But the other side of it is if it's that heavy! 400lbs?! 1/2" wall tubing?
I'm sure a replacement one can be fabricated that has 3/16 wall or even 1/8" which would work well.

Also, I just thought of the big 18 wheelers and their dual tanks with no crash barriers.

There are many box trucks out there also with steel diesel tanks similar to the bus tanks hanging out in the breeze. On my bus, there is still a rail around the tank and the riveted skin on top of that. No concern at all for the removal, this is a Coach, not a schoolbus Added bonus the fuel fille is now on the drivers side.

[Joe45]

Did you remove your cage?

If so, was it a difficult nightmare task, or pretty simple?

[Rivetboy]

Originally Posted by Joe45

Did you remove your cage?

If so, was it a difficult nightmare task, or pretty simple?

1/2 bolts with air tools, 2 people and it was supported by a floor jack with some ply wood and construction screws rigging. Just unbolted it and lowered it down. It really is that heavy! Look up a few posts for the picture.

[Sehnsucht]

After the 1988 Carrollton KY bus crash, fuel tank safety cages became mandatory on all school buses nationally. Kentucky also made some regulatory mandates which is why their buses have so many more emergency exits than buses from other states. They also outlawed gasoline powered buses in favor of diesel which is less flammable.

As far as trucks with uncaged fuel tanks, those round tanks are designed to withstand a lot of impact stress but again diesel isn't actually flammable so if it ruptures in an impact the fuel isn't at risk of ignition by a local flame or heat source. It does pose an environmental concern however so at wreck scenes they have to contain any fuel spills.

[Rivetboy]

Originally Posted by Sehnsucht

After the 1988 Carrollton KY bus crash, fuel tank safety cages became mandatory on all school buses nationally. Kentucky also made some regulatory mandates which is why their buses have so many more emergency exits than buses from other states. They also outlawed gasoline powered buses in favor of diesel which is less flammable.

As far as trucks with uncaged fuel tanks, those round tanks are designed to withstand a lot of impact stress but again diesel isn't actually flammable so if it ruptures in an impact the fuel isn't at risk of ignition by a local flame or heat source. It does pose an environmental concern however so at wreck scenes they have to contain any fuel spills.

There are plenty of rectangular aluminum uncaged diesel tanks out there also. The school bus steel diesel tank at 60 gallons capacity is no light weight either. In fact; it is one heavy piece of hardware in its own right.

[TheHubbardBus]

Originally Posted by Sehnsucht

After the 1988 Carrollton KY bus crash, fuel tank safety cages became mandatory on all school buses nationally. Kentucky also made some regulatory mandates which is why their buses have so many more emergency exits than buses from other states. They also outlawed gasoline powered buses in favor of diesel which is less flammable.

Are you saying that a crash in which gasoline was the problem (I'm guessing here - don't know anything about it) was the basis for regulations affecting all school bus fuel tanks, regardless of the type of fuel?


If so, that's wack.