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Old 06-09-2019, 07:19 PM   #1
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Roof raise thoughts

First, I am not a structural or automotive engineer. I am a retired pole climbing, dirty old linemen.
I have no experience doing roof raises.
I am NOT anti-roof raise.

I have been poking around the internet, looking at the way buses are built.

Skoolies are not built like other buses.

Big old over the road tour buses have a truss frame that doesn't rely on roof/walls for stability. A Skoolie needs it's box intact to be strong.

Build the crap out of your roof raise, return the box to it's original integrity.

These observations are probably worth what you paid for them.

We all know what a Skoolie looks like with the roof (and walls) cut off.
This is what a big bus looks like in the same condition.

I find this very interesting, you may not.
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File Type: jpg Typical big bus.jpg (26.0 KB, 61 views)
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Old 06-09-2019, 07:52 PM   #2
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Originally Posted by 2kool4skool View Post
First, I am not a structural or automotive engineer. I am a retired pole climbing, dirty old linemen.
I have no experience doing roof raises.
I am NOT anti-roof raise.

I have been poking around the internet, looking at the way buses are built.

Skoolies are not built like other buses.

Big old over the road tour buses have a truss frame that doesn't rely on roof/walls for stability. A Skoolie needs it's box intact to be strong.

Build the crap out of your roof raise, return the box to it's original integrity.

These observations are probably worth what you paid for them.

We all know what a Skoolie looks like with the roof (and walls) cut off.
This is what a big bus looks like in the same condition.

I find this very interesting, you may not.
A central part of a school bus body's integrity is the ribs forming the walls and roof, bent from single pieces of homogenous hat channel material. A roof raise cuts these ribs in two places, and even the best-quality welding and bolting of the rib extenders will still concentrate stresses at those cuts (even if the welds and extenders are stronger than the channel material this will happen) making them prone to fail.

I am also not anti-roof raise, I just don't think people should be expecting their raised buses to be as structurally strong as they were before the modification. Just don't ride in the back of the damn things.
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Old 06-09-2019, 07:53 PM   #3
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Quote:
Originally Posted by 2kool4skool View Post
First, I am not a structural or automotive engineer. I am a retired pole climbing, dirty old linemen.
I have no experience doing roof raises.
I am NOT anti-roof raise.

I have been poking around the internet, looking at the way buses are built.

Skoolies are not built like other buses.

Big old over the road tour buses have a truss frame that doesn't rely on roof/walls for stability. A Skoolie needs it's box intact to be strong.

Build the crap out of your roof raise, return the box to it's original integrity.

These observations are probably worth what you paid for them.

We all know what a Skoolie looks like with the roof (and walls) cut off.
This is what a big bus looks like in the same condition.

I find this very interesting, you may not.


lets just say, 'there is less work in doing a roof raise in a tour bus'
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Old 06-09-2019, 08:15 PM   #4
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Seems like the tour bus has far fewer structural members supporting the roof. The roof looks strong, but man, so few pillars.

School busses are designed by law to resist a roof cave in in the event of a roll over. I wonder how a coach fares in that scenario.
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Old 06-09-2019, 08:19 PM   #5
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IMG_9618.jpg

Some survivors, but some fatalities as well.
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Old 06-09-2019, 08:25 PM   #6
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School busses are designed by law to resist a roof cave in in the event of a roll over. I wonder how a coach fares in that scenario.

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Originally Posted by david.dgeorge07 View Post
Attachment 34353

Some survivors, but some fatalities as well.

That answers that.
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Old 06-09-2019, 08:47 PM   #7
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Found another angle. Looks like this may not have been a coach style bus. I see a driveshaft so it must be a puller.

That roof though. Just a disaster.

38 onboard, only 1 dead. Hard to believe it wasn’t worse.

IMG_9619.jpg
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Old 06-09-2019, 08:58 PM   #8
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I think there are other important differences about the weight distribution of a skoolie and a tour bus as well.

If you look at a school bus head-on, it's a fairly short rectangle - it's taller then it is wide, but not by much. (I think general consensus is 8 feet by 10 feet or so.)
A tour bus is a LOT taller. (8 x 11 or 8 x 12).

That extra height means a couple different things. First, if a tour bus rolls over, it's more likely to roll onto it's side, and stay there. It's a tall rectangle sideways - there's not that much of a chance that it's going to continue to roll onto the roof. I also wouldn't be surprised if tour buses have a lower center of gravity in the first place- larger engines, closer to the ground, and just more weight in axles, engines, luggage bays, etc. So if you look at the framing on the tour bus, the heavy stuff is down low - it goes to the bottom of the windows, which is enough to support the bus on its side. The roof and windows are designed to keep it from rolling over, not exactly to fully support it upside down. While you're giving up a bit of roof integrity, you're also helping to keep the center of gravity lower - which lets you have a nice, tall roof height in the first place. (At least, that's what I believe the design logic is.)

There's also the fact that a school bus, at 55mph, is going to have vastly different physics then a coach bus doing 75. Not to be morbid, but at some point, it doesn't matter what you do, the results aren't going to be pretty. That said -


There are roughly 128 people killed every year in school-bus related crashes in the US. 9% of those (11 people) were passengers riding the bus - the vast majority were either pedestrians, or occupants of other vehicles in the crash(es).

https://crashstats.nhtsa.dot.gov/Api...ion/812476.pdf



If you go here, in 2016, there were 10 people killed in motor coach accidents. (14 in transit buses, 3 in vans, and 27 in "other" buses. Also 10 in school buses.)

https://www.fmcsa.dot.gov/safety/dat...ash-facts-2017
(Scroll down to Trends Table 25.)

So overall, at least as buses, these things are pretty darn safe. I'm not qualified to say that 10 lives/year is enough to re-design the way we build over the road buses.
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Old 06-09-2019, 09:01 PM   #9
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Originally Posted by Mark_In_MA View Post
I think there are other important differences about the weight distribution of a skoolie and a tour bus as well.

If you look at a school bus head-on, it's a fairly short rectangle - it's taller then it is wide, but not by much. (I think general consensus is 8 feet by 10 feet or so.)
A tour bus is a LOT taller. (8 x 11 or 8 x 12).

That extra height means a couple different things. First, if a tour bus rolls over, it's more likely to roll onto it's side, and stay there. It's a tall rectangle sideways - there's not that much of a chance that it's going to continue to roll onto the roof. I also wouldn't be surprised if tour buses have a lower center of gravity in the first place- larger engines, closer to the ground, and just more weight in axles, engines, luggage bays, etc. So if you look at the framing on the tour bus, the heavy stuff is down low - it goes to the bottom of the windows, which is enough to support the bus on its side. The roof and windows are designed to keep it from rolling over, not exactly to fully support it upside down. While you're giving up a bit of roof integrity, you're also helping to keep the center of gravity lower - which lets you have a nice, tall roof height in the first place.




Also, interesting statistic - there are roughly 128 people killed every year in school-bus related crashes in the US. 9% of those (11 people) were passengers riding the bus - the vast majority were either pedestrians, or occupants of other vehicles in the crash(es).

https://crashstats.nhtsa.dot.gov/Api...ion/812476.pdf



If you go here, in 2016, there were 10 people killed in motor coach accidents. (14 in transit buses, 3 in vans, and 27 in "other" buses. Also 10 in school buses.)

https://www.fmcsa.dot.gov/safety/dat...ash-facts-2017
(Scroll down to Trends Table 25.)

So overall, at least as buses, these things are pretty darn safe.


Good analysis.
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Old 06-09-2019, 09:02 PM   #10
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Found another angle. Looks like this may not have been a coach style bus. I see a driveshaft so it must be a puller.

That roof though. Just a disaster.

38 onboard, only 1 dead. Hard to believe it wasn’t worse.

Attachment 34355
I just watched the helicopter video that this still was taken from. Looks like this was a shuttle bus, so not surprising that it was crushed like this. A good reason not to base your conversion on something made out of fiberglass.

Here's the video: https://www.facebook.com/WYFF4/video...5445552094114/ At about 6:55 the camera pans back to a second bus (undamaged) from the same church that appears to be the same type of bus.
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