Roof Raise Steel question

[Intalleyvision]

I'm ready to raise my roof. I've decided to go with the scaffolding method. My question is how many extra inches do you usually have on the new steel rib piece that overlaps with the existing rib? Like if I'm raising my roof 20", how long does my rectangular tubing need to be? Also what gauge steel would you suggest using? My bus ribs are 14 gauge so I figure that would work fine.

[slaughridge85]

Im getting ready to do my raise 16" and I plan to use 26" sections of square tubing leaving 5 inches on either side of my cut... woohoo 1st post!

[EastCoastCB]

Originally Posted by Intalleyvision

I'm ready to raise my roof. I've decided to go with the scaffolding method. My question is how many extra inches do you usually have on the new steel rib piece that overlaps with the existing rib? Like if I'm raising my roof 20", how long does my rectangular tubing need to be? Also what gauge steel would you suggest using? My bus ribs are 14 gauge so I figure that would work fine.

I"m planning to use custom bent channel made with 14ga to replicate what the rib is made from at the factory. I'm going to leave 4-6" of overlap on either end. I plan on doing a one foot raise, so I'm going to have them made 20".
There's no certain answer here, imo.

[nat_ster]

I over lapped 12 inches on both ends.

I raised my roof 24 inches. This made my splice pieces 48 inches long, making best use of the 4x8 sheets of steel we sheered to form the ribs from with no waste.

I would not do less, you want to spread to connection over as large area as you can.

Mine were custom formed 14ga ribs made to the same shape as the original ribs.

I was the first one I ever seen to do the custom formed ribs. It's the best and strongest method that can be used.

I was also the first to use scaffold to lift the roof. I found it vary safe, simple and easy.

More can be seen here in my latest build thread.

http://www.skoolie.net/forums/f11/th...ime-10138.html

Nat

[EastCoastCB]

[mrblah]

For a structural pov, the overlap isn't as important as how much fastening you will have.

Rivets or bolts?

How many of them are needed to have the same tensil strength as the original ribs?

How much space do you need between rivets/bolts?

If I was interested in doing one I'd answer those question first. But I'm the overly cautious chicken type so Iight be over thinking this...

[nat_ster]

I like to spread the connection out.

All my outside skin bolts / rivets pass through both the original and the new rib splice.

Same for the bolts that hold the inside strapping on.

I also used Por 15 as a metal adhesive between the new splices and the original ribs.

When using adhesives, the larger the connection the more strength it will have.

I didn't invent anything. I just used what I had around.

I based my fastener count off the original structure at the rub rail. The rub rail supports 100% of the load from the walls to the floor. Each rib on my buses have between 3 and 9 rivets into the rub rail.

So with that I made sure to have at least 12, 1/4 bolts / rivets in each end of the connection, plus the metal adhesive.

Nat

[mrblah]

Originally Posted by nat_ster

I like to spread the connection out.

All my outside skin bolts / rivets pass through both the original and the new rib splice.

Same for the bolts that hold the inside strapping on.

I also used Por 15 as a metal adhesive between the new splices and the original ribs.

When using adhesives, the larger the connection the more strength it will have.

I didn't invent anything. I just used what I had around.

I based my fastener count off the original structure at the rub rail. The rub rail supports 100% of the load from the walls to the floor. Each rib on my buses have between 3 and 9 rivets into the rub rail.

So with that I made sure to have at least 12, 1/4 bolts / rivets in each end of the connection, plus the metal adhesive.

Nat

Sounds right on the money to me! I like your numbered and calculated approach to things!

[family wagon]

I second nat_ster's advice on the scaffold and hat channel. At the moment (and for the last two weeks) my bus roof has been sitting atop a pair of scaffold frames waiting for me to get around to re-attaching it.. hopefully that'll come on Monday and I'll post some updates on my build thread then. In my case it's good I chose the hat channel: when I got the wall opened up I discovered that the existing hat channel is filled with a U channel already, so the square tube method can't be done on mine. Mine was a transit bus though with wide windows; it seems the narrow-window school bus variety might not have this "feature"...

One other thing I'm doing differently is I'm raising from the base of the wall rather than in the middle. There'll be more sheet metal work, but only one splice/lap joint instead of two on each side of each rib.

[nat_ster]

I like Family Wagons approach of raising from the chair rail. This didn't cross my mind until I was done my roof raise.

It requires removing outside panels at the floor line, but that is also a plus. Doing so allows you to fix rust, and repaint the steel in the area that is usually the most rusty.

Nat

[Intalleyvision]

Okay the steel has been ordered. I'm doing a 20" raise, with 36" Steel tubing, 1.25" at a 14 gauge. That'll leave me 8 inches on either side. I plan on bolting it into place (With multiple bolts) along with some adhesive for added help. Cost me $66 at my local metal shop.

[EastCoastCB]

FWIW- If anyone near me (FL) wants any "hat" channel made hit me up.

[nat_ster]

Originally Posted by Intalleyvision

Okay the steel has been ordered. I'm doing a 20" raise, with 36" Steel tubing, 1.25" at a 14 gauge. That'll leave me 8 inches on either side. I plan on bolting it into place (With multiple bolts) along with some adhesive for added help. Cost me $66 at my local metal shop.

You will not be able to use bolts with tubing.

There are no flanges to bolt through.

If you use tubing, your stuck to welding them in.

You also can't use adhesive with tubing. The new and old pieces must match to use adhesive.

Hat channel is the way to go.

Nat

[Intalleyvision]

I couldn't drill holes through the ribs, mark the tubing, then drill holes in the tubing, then bolt them in place? I was planning on doing bolts on all three sides like in this sketch. Is there any reason why that wouldn't work?

[family wagon]

I can't tell whether those bolts go all the way through, or if you're bolting them "blind" by getting a nut up inside so that the bolt only clamps the near side of the tube. If the bolts go all the way through, is it necessary to sleeve the tube..? If not sleeved, then there's a reduced limit to how much clamping the bolt can provide (if the bolt is tightened beyond some point, the tube will crush).

[Intalleyvision]

Haha yeah I just realized I'm an idiot and could tighten the bolts while they're in a tube. What about something like this? Do 8 bolts (2 in a row, 4 rows, spread out evenly over the 8 inches) Top and Bottom.

[Tango]

You'll still be better off with a channel that is open to the inside and fits snugly if you are using bolts. Those bolts need to be cinched down VERY tight to create any kind of bonding force. What you are showing is going to move. Not a good thing.

I used 1-1/4" thick wall square tubing that fit tightly inside my old BB ribs but they employed a combination of welding (mostly as a temporary hold) and a bunch of quarter inch blind steel rivets on 3 sides and then a section of original rib material spliced in to fill the gap that also used both methods of securing.

[Intalleyvision]

Could I fill the gap between the ribs and the tubing with washers?

[Tango]

Yes...but you will still be basically crushing the square tube in as you try to tighten the bolts. The force needs to go to pulling the inner & outer elements together...not collapsing the tube.

[nat_ster]

Just get hat channel made..........

Nat