Need advice on sinking Motosat satellite dish into RTS roof for clean roofline

[Sojourner]

About stress around roof's hole.

Your MCI's roof structural consists of 2 things....
1)   Framing with no diagonals but to hold it in planed or cage form.
2)   Skin or roof cover is your diagonals stress points.

You can remove sheet metal around hole to make larger or to installed new hole...you need to add another sheet metal under or over roof's skin at about 2/3 larger dimension (the more is better) using piece of same thickness or thicker. Never use screws or bolts or pop rivet but solid aluminum rivets or any rivet that fill in to swell tight in hole to keep it from moving sideways as well holding it on.

What ever you do you must always leave at least ¼" radius inside corners to help prevent stress crack or tearing.

On the other hand if roof is fiberglass such as with the end cap...then you needs to have diagonals framed roof construction thorough out the whole fiberglass areas. Fiberglass is strong but it doesn't hold firm sideway around the rivet well.

FWIW

Sojourn for Christ, Jerry

[Kevin Warnock]

Thanks for the great comments above.

I bought the RTS in large part because it has fully functioning over the road air conditioning, so I am not considering removing it. I get 10.75mpg without it turned on. I haven't calculated the fuel economy when it's switched on, but I'm sure whatever the number is it will be above 6.4mpg, which is what I get with my MCI 5a conversion.

I understand there is some risk in cutting into the roof, but it must be possible to do safely. Haven't others raised the entire roof on an RTS before? That must raise many more issues than the cut I am contemplating.

If I have a box cage welded with cross beams on the bottom of the box, and have this cage welded to the ceiling of the RTS before I cut, wouldn't that cage take over for the removed sheet metal? If I use substantial square tubing, it would seem to me that it would be more stiff than what I have now, and that I wouldn't need to perform any math calculations, as what I have in mind will be so much more than required, I would guess.

This reminds me of the guy that wanted to cut a hole in the floor of his older GMC, non RTS, bus, and some said the bus would fall apart if he did it, and others said to put a reinforcing frame around the hole and he would be fine. The box I have in mind will be that reinforcing frame. They were talking about using plywood for the frame, while I am talking about welding a substantial and hefty cage, so I think I'm likely to be fine. However, people here are cautious, and I appreciate their concern. What's the 'proper' way to do this? Do I engage a structural design firm and have them run numbers in a CAD program?

Don't people routinely cut extra holes for roof air conditioners in the roofs of MCI, GMC and GMC RTS buses? Some conversions have five roof airs, but probably there were not five escape hatches. How do those converters handle the issue we're discussing here?

Thanks very much to all,

Kevin

[Utahclaimjumper]

Kevin, you also should be thinking of snow and ice..>>>Dan

[HighTechRedneck]

I recall the thread you referred to about someone planning to put a slideout in a GMC bus.  I don't recall that they ever posted follow up on it.  If you do this, please do follow up after doing it and then after a siginficant (1000 miles) shake down (hopefullly not literally  ) period.

You do raise a good point about air conditioners.  But also keep in mind they are much smaller holes and not generally in the first 5' section ahead of the engine.  Remember, the engine and transmission "hang" from the bulkhead, and is somewhat cantilevered by the roof.  The way you are proposing welding in the caged box first and then cutting the hole makes sense.  But you are right, I am cautious about anything that could potentially create a structural weakness.  It's just me though.  If you are confident of it, then you should by all means do it.  The old busnut motto is "do it your way".

[Kevin Warnock]

Dan,

Thanks for the reminder. I will install a turkey fryer burner under the Motosat dish cage, and turn it on as necessary... just kidding. But perhaps I could install some electric radiant flooring heating material into the bottom of the cage box, and then turn it on as needed to melt accumulated snow. Anybody have any suggestions on this front? Is that heating material waterproof? What about the material put into concrete sidewalks to melt snow? Would that be better? Where would I buy this, and what is the official name for it, does anyone know?

Thanks,

Kevin

[HighTechRedneck]

I've seen guys use aquarium tank heaters to keep their water and waste tanks from freezing.  I would assume they are water resistant (not submersible, so it definitely goes on the part facing into the bus) and they are readilly available at most pet supply stores.  Or you could use a heat tape like is used for wrapping water lines.  That might be easier to fit to your exact needs and is readily available at Wal-Mart, Lowes, Home Depot, etc.

[DavidInWilmNC]

I know you want your bus to look like a BUS... but this seems like a ton of work, with a lot of potential problems and issues, to attain that goal.  If this recess in the roof is made to fit your current system, I wonder if a future replacement dish will fit there correctly? 

David

[HighTechRedneck]

Another idea for keeping the snow/ice melted.  If you are considering a Webasto type hydronic heating system, you could run a loop up there to keep it warm.

[Kevin Warnock]

David,

I've thought about your point that future dishes might not fit. However, I suspect I will get many more years out of the current dish. These things are built like tanks, and Motosat did not make my dish obsolete when they introduced new controllers and modems. But even when I have to replace the dish, say five years from now, I suspect the new one will be smaller overall. But it's a very good point to think about, and I thank you for mentioning it.

Kevin

[mc8 tin tent]

  Kevin
Frostex makes a self limiting heat trace. You could put the heat trace on the inside (coach side) with insulation covering it,then trim with your headliner material to dress it off.(this heat trace comes 120v or 230/208v and should be available from most refrigeration/ plumbing sply. houses . also with the heat applied to the dry side of the cabinet it doesn't need to be water proof (but it is),you may want to install a power switch to turn off the heat trace when not needed( no thermostat needed self regulating and from aprox.3wts. to 8wts. pr ft.depending on the voltage.)
   Dwayne

[prevost82]

What about all the water that will accumulate in the hole, what are you going to about that ... I'd say snow is the lest of your problems ... if you have the MotoSat sitting in a 8 or 10 inch deep swimming pool, you'll have nothing but problems with it. The sat. dish is full of electronic components that are water proof but are prone to moisture intrusion. I don't know ...call me crazy but I seem like a lot of work to make a roof line look good, with reduced head height on the inside of the bus ... why don't you use a broadband card.

[DrivingMissLazy]

What about all the water that will accumulate in the hole, what are you going to about that ... I'd say snow is the lest of your problems ... if you have the MotoSat sitting in a 8 or 10 inch deep swimming pool, you'll have nothing but problems with it. The sat. dish is full of electronic components that are water proof but are prone to moisture intrusion. I don't know ...call me crazy but I seem like a lot of work to make a roof line look good, with reduced head height on the inside of the bus ... why don't you use a broadband card.

In an early post he indicated he was putting in a massive drain system.

Richard

[RJ]

Kevin -

The chassis of the RTS, under the outside skins, is mostly stainless steel.  Use a magnet to check the area you're contemplating welding in reinforcements.  If the magnet doesn't stick to the crossbows, then you're going to have to figure out how to weld regular steel to stainless, unless you can come up with $tainle$$ tubing.

Perhaps Chaz can jump in here and clarify welding to stainless. . .

Personally, I'd just mount the dish in a normal way, then tell folk it's the latest high-tech solar collector for the ETB (Electric Trolley Bus) powertrain. . .   

FWIW & HTH. . .

[compedgemarine]

several years ago I had a hospitality trailer that was a retired NASCAR race hauler. in the roof over the lounge was exactly what you are talking about. it was 6 foot by 8 foot and housed a satalite dish and the compressor units for the a/c for the lounge and work area. the only real problem that it had was drainage. it had two 3/4 inch drain lines which worked fine except that running down the road dirt would go up in the tubes and when it would rain the dirt turned to mud and they would plug up pretty bad. once it flooded the box enough that it found a place to leak and ruined the cabinets in the lounge. not saying that you shouldnt find a way to do this if you want but pay close attention to the drains at the bottom to avoid road dirt and dust from finding its way in.
steve

[Sojourner]

I would think of everything possible to avoid having a pan build in roof. One problem lead to many more problem later.

However if you want to install larger than original hole a box of whatever reasonable size without using double lamination of sheet metal you can do the following drawing in 3 attachments.

I am not responsible for any fatigue of the reworked/modified design. You are responsible of all modification work because of the out come of the workmanship preform.

This is what I would be satisfied if I build the modified opening on my own MCI.

FWIW

Sojourn for Christ, Jerry


Choice of two drawings of roof boxes

No. 1 Constructed with 1 1/2 " tubing from top to bottom
No. 2 Same as no.1 but bottom 2/3 is lean construction
using 3/4" tubing for pan & posts

3/4" vertical posts are welded to inside corner of the
1 1/2" main frame to keep inner wall straight vertically.