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Old 03-20-2008, 02:45 PM   #1
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How to weigh a stationary bus + brake question

Hi guys! New to the group. I have an old driveable 65 Ford 66 passenger school bus, and after 15 years in one spot, it's time to move. (It even went through the flood of '93 in Iowa with 18" of water inside the bus!) The bus is a full blown machine shop with machines down either side. I'm moving 4 hours away and need to license it. I've got ots of additional questions but for now I need to weigh it without moving it. One friend says to jack it up from the rear with a 20 Ton jack with a pressure gauge, pivoting off the front bumper (it is massive and tied to the frame.) Then do the same thing pivoting off the back bumper and jacking up the front. My question: What do I do next? Add the weights (I can calculate from the pressure and diameter of the piston) and divide by ? The Gross Vehicle Weight on the tag is 20,500. I may be a tad over that so I need to get a weight so I can remove tools if necessary to get it licensed. Any ideas would be appreciated.
2nd critical question: It only has a single brake master cylinder going down to a power brake booster attached to the frame. The flood of 93 virtually destroyed the booster. Since then I've purchased a Ford F-350 dual master power brake unit that I plan to mount on the firewall. Will this give me the stopping power I need for the bus, running one line to front and one line to rear? It's a very unique and heavy bus. I have driven it the way it sits, but am debating whether to have it towed or trucked to the next location. Thanks for any ideas, Mike Fendley, Le Claire, Iowa
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Old 03-20-2008, 09:11 PM   #2
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Re: How to weigh a stationary bus + brake question are looking at some serious math to calculate the weights from what you want to do. You're also going to need to know the angle. Trigonometry is your friend. Even then I don't think it's going to be possible without knowing the center of gravity in the first place. I'd probably be looking for a different method or jack it up front and rear an equal amount at the same time. Basically, you're going to want the bus level when you figure this all out. You could do it with some cribbing.

1. Jack up front of the bus and crib it up.
2. Jack up rear of bus with jack until it is perfectly level and calculate axle weight by dividing pressure by piston area.
3. Put rear of bus on cribbing
4. Jack the front up until it is perfectly level again.
5. Calculate front axle weight using the pressure/area method
6. Add both weights together to get gross vehicle weight.

If you have an angle involved there is weight transfer. Now I'm reasonably certain there is a method to do it, but I'd have to sit down and think for a while about the whole SOH-CAH-TOA trig thing to figure it out. Something about a normal force and a perpendicular force and rotating the axis and such. Ugliness at best...
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Old 03-21-2008, 03:53 PM   #3
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Re: How to weigh a stationary bus + brake question

15 years sitting idle, and with a flood? I'd have to agree with towing or flatbedding it.

Maybe your MVD can issue a temporary 3-day permit, or something similar?

Good luck

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Old 03-22-2008, 09:11 PM   #4
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Re: How to weigh a stationary bus + brake question

As for weighing it, just rent a heavy duty scale or something like that. Weigh the weight on each wheel. Then add all 4 weights up. That's what we do in the Air Force when we're hauling vehicles on an airplane. The exact weight is critical for weight and balance too.
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Old 03-24-2008, 03:54 PM   #5
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Re: How to weigh a stationary bus + brake question

how friendly is the local state weighmaster, he should have portable scales and like donuts
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Old 03-25-2008, 01:52 PM   #6
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Re: How to weigh a stationary bus + brake question

I don't think your master cylinder idea will work. I had my brake booster go out once on my 2 ton truck and it's amazing how much help it gives to your brakes. I had to put both feet on the pedal to get it to stop without boost and I thought I was going to go through the back of the seat. You can get rebuilt ones for a couple or three hundred bucks. I bet your wheel cylinders need rebuilding also, especially after being submerged for a while. Your steel brake lines are probably rusted and leaking too. Borrow a set of scales to weigh your bus, you might even be able to rent a set, you only need 2. sportyrick
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