Ludicrous Speed

[Tango]

Hey Guys, moving along nicely and looking great. I did a 40' BBAA a few years back and was fortunate enough to live just down the road from a BB engineer that I could consult with regularly (Lived near Douglasville, GA at the time). He gave me some great tips & insight into the Bird structure, one of which involved removing sections of ribs. The "official" BB party line is absolutely 100% opposed to any mods to the rib system since its' integrity relies on equal & uniform loading from end to end. That said, my engineer neighbor advised something like the following..."if you ARE going to chop up my design, you'd better compensate for screwing up the loading and do it right while you're at it". He talked (lectured) at length about how the combination of ribs & sheet metal formed a shell under uniform tension and that taking out any portion was like pitching a tent nice and taught, then removing a couple of pegs. It would probably be just fine...until the first time the wind blows. Any system that relies on such uniform tension is severely compromised when even a single element is removed. He advised compensating by boxing in any sections that had ribs cut away (such as for shiny, new RV windows) with full inch and a half, heavy gauge square tubing all the way around the opening that were tied (welded) back into the rest of the framing.

I've seen all kinds of chop jobs survive for years with little or no reinforcing at all, but personally chose to go with what seemed to make long term engineering sense based on his insight and comments. My final engineering choices were based on two considerations. First, I can see how an evenly tensioned system would naturally be inclined to torque out of shape by simply removing a single element. Second, Blue Birds are legendary for their crash & roll resistance, but it too is based on that balanced tension concept that can spread a load throughout the entire structure. Take any segment out of that system, and you've just created a very efficient crumple-zone...in a less than desirable area.

Certainly not telling anyone how to build their bus, but did feel compelled to share the results of the chats with my very knowledgeable (and very opinionated) neighbor with my friends here on the Skoolie board.

[ol trunt]

At the risk of butting in I'd second the advice given by Tango. Throughly box in your window cutout and try to stagger any other cuts well away from the first (no more cuts would be better). Just my 2 cents worth

[Stretch]

The area where supports are missing will be boxed in. Waiting on steel at the moment.

[Mark_Henning]

Your post on panel covers over window openings was very helpful toward my own project... Was wondering what gauge steel you used?

[Stretch]

18 gauge. I believe it is just CRS, or cold rolled steel.

[TheRainbowBoxer]

18 gauge is what we used, and as Stretch said, it was cold rolled steel. We likely could have gotten away with a lighter gauge, but this seems to work pretty good, and should resist the dreaded "oil-canning" that some people have experienced.

It is a pain to move the heavy sheets around for painting and install, and I would strongly recommend some decent work gloves, as the edges of the metal are pretty sharp.

[Jarlaxle]

Originally Posted by Tango

Hey Guys, moving along nicely and looking great. I did a 40' BBAA a few years back and was fortunate enough to live just down the road from a BB engineer that I could consult with regularly (Lived near Douglasville, GA at the time). He gave me some great tips & insight into the Bird structure, one of which involved removing sections of ribs. The "official" BB party line is absolutely 100% opposed to any mods to the rib system since its' integrity relies on equal & uniform loading from end to end. That said, my engineer neighbor advised something like the following..."if you ARE going to chop up my design, you'd better compensate for screwing up the loading and do it right while you're at it". He talked (lectured) at length about how the combination of ribs & sheet metal formed a shell under uniform tension and that taking out any portion was like pitching a tent nice and taught, then removing a couple of pegs. It would probably be just fine...until the first time the wind blows. Any system that relies on such uniform tension is severely compromised when even a single element is removed. He advised compensating by boxing in any sections that had ribs cut away (such as for shiny, new RV windows) with full inch and a half, heavy gauge square tubing all the way around the opening that were tied (welded) back into the rest of the framing.

I've seen all kinds of chop jobs survive for years with little or no reinforcing at all, but personally chose to go with what seemed to make long term engineering sense based on his insight and comments. My final engineering choices were based on two considerations. First, I can see how an evenly tensioned system would naturally be inclined to torque out of shape by simply removing a single element. Second, Blue Birds are legendary for their crash & roll resistance, but it too is based on that balanced tension concept that can spread a load throughout the entire structure. Take any segment out of that system, and you've just created a very efficient crumple-zone...in a less than desirable area.

Certainly not telling anyone how to build their bus, but did feel compelled to share the results of the chats with my very knowledgeable (and very opinionated) neighbor with my friends here on the Skoolie board.

I have a Genesis, not a Bird, but I didn't remove ANY uprights! I am just not comfortable with cutting structural supports.

[chev49]

i am going to permanently remove several uprights when i build a 12-14' slide. I will just box in the perimeter with 2x3 channel.. After all, a skoolie is just a steel box on a truck frame...

[atcc77]

Man, you guys are really making good progress! Looks like ya'll are having a good time doing it as well. Here at my house it's only me so far, with a little help from the four year old and lately, I've been so busy working for other people there just hasn't been time to even get near the bus. Not sure how you got teenagers to participate so happily, but is good to see... Good times man, good times.

[TheRainbowBoxer]

Thanks! It seems like we are going very slowly to us. The deadline for the maiden voyage is creeping up on us.

The last 2 days I continued to skin windows, and now only have the final piece on each side to do. I am waiting on the square tube steel I had to order to box in the dinette windows. If it does not come in tomorrow, it looks like I will start installing the windows in the back half.

[TheRainbowBoxer]

All of the window skinning is done! I put in over 520 rivets including reattaching the rub rails... Wow. Rivet tool is getting worn out too, as it popped the rivets in 3 pulls when I started, but by the end it was 6 or 7 and kept slipping.

Ceremonial final rivet ---

http://www.youtube.com/watch?v=73z9oFHXDWI

[bansil]

Great victory vid

[keith]

Ha rainbow ,,,when are u going to start on the slides,thats what i want too see i got a 94 bird,but i got belly bays .i have one speace to put a slide.

[TheRainbowBoxer]

Don't think I'm going that route LOL! Remind me to try that on my next conversion (yeah right hahahaah)...

[TheRainbowBoxer]

OK, over the last week or so we began working on adding the RV windows and installing a hitch and trailer wiring.

For most of the window install, I used an air nibbler to cut the holes. This tool cuts through the steel pretty fast. Unfortunately, the nibbler, being from harbor freight, was not the most robust of tools. I tended to break the cutter/punch after relatively short cuts. The nibbler was clearly marked to be good up to 16 gauge steel, but the 18 gauge I was using it on proved to be too much. Needless to say, after 4 trips to harbor freight, I decided to just cut the steel with the handy cutoff wheel.

Now for some pics!


I used drill bits of increasing size, so I wouldn't snag and twist the sheet metal when making the hole for the nibbler.


The nibbler would get a great start from one of these holes.


There is a hole in my bus again! This appears to be a recurring theme!

[TheRainbowBoxer]

I used the same rope caulk for the windows that I used on the door install. After securing a bead of caulk around the window frame, I clamped the window into the hole, with a 2x2 on each of the sides. I then screwed the frame to the sheet metal of the bus (and on through into the wood) with stainless steel self-drilling screws. Once the window is fully attached, it makes the sheet metal feel much more solid.


I used welding vise grip style clamps to hold the window in place.


The heads of the stainless screws were 5/16" hex head. I used a drill with a 5/16" nut driver attachment to drive them.


One of 4 windows that I have installed. I plan on putting in 4 more (kitchen, bathroom, and one in each top bunk), but they will have to wait until after the maiden voyage.

[TheRainbowBoxer]

OH! before I get to the hitch install, I realize I left out the pics of the framework we welded in to compensate for the 2 consecutive ribs I removed on either side of the bus. Yes we are aware that it is not as strong as it was when it rolled off the assembly line, but we are doing what we can to retain as much of that original strength as possible.


The steel we used was 11 gauge 1" square tubing.


Once again, my welding buddy, Stretch, taking good care of me ;)


The welds where the frame crossed the ribs that were removed.

[TheRainbowBoxer]

I needed to install a hitch on the bus, as we are going to use it to pull my friend's camper for our trip to Haspin Acres. A few of my friends and I tend to get a little noisy during the nights at this event, and Stretch likes his sleep, so he brings separate sleeping quarters. At first I acquired a hitch from my dad, but after some relatively close inspection, we realized it was too rusted out to trust.


I found this hitch on craigslist for $40. It still has undercoating on it, and the guy let me beat on it with a ball peen hammer to make sure it was not too rusted/soft. It was not the first one the guy showed me, but he happened to have one that fit my frame rails exactly! No cutting and re-welding makes us happy


The hitch is installed! I used grade 8 1/2" bolts with regular and lock washers to secure it to the frame. These were tightened firmly with an impact wrench.


I used a hole saw to cut the hole for the trailer wiring outlet. The bumper on this thing is THICK. I had to repeatedly dunk the hole saw in oil to keep it cutting without dulling/breaking it.

[TheRainbowBoxer]

I ran into a bit of a pickle with the trailer wiring, as the bus is wired for separate brake and turn signals, and trailers are wired to combine these. I could not just tie them together, as it would cause the bus lights to stop functioning properly, and I did not want to do without either the turn signals or the brake lights on the trailer. I could have gone into town, spent the $22 on the easy converter, and had it done no problem. But in grand skoolie fashion, I said "I can do this myself!" since I happened to have a few relays lying around. My first attempt (trying to wing it), I wound up doing nothing but isolating the turn signals, basically mimicking exactly what was already there... D'OH! After scribbling a few schematics on paper, I decided on a better course and was able to get it done correctly.
Note: The oddity with this setup is that when the brakes are applied while the turn signal is on, the turn signal on the trailer blinks out of sync with the bus. Figured some might find that interesting.

The wiring was then soldered to a heavy duty cable with enough leads in it that I could wire the trailer brakes if I so desired (not doing it at this time) and threaded down through the floor inside the wall to the trailer outlet.


I mounted the trailer wiring outlet in the bumper.


While this looks a bit like the proverbial rat's nest, I cleaned it up considerably before closing it back up.


Here is my schematic for those interested who know how to read them. Sorry for anyone who gets a headache trying to read it.

[pipopak]

Read the regulations about max length RC+ trailer in your state BEFORE sailing out. You don't want to learn about them in the middle of nowhere from some trooper!.