| Author |
Message |
John Wardell
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 15, 2005 - 5:15 pm: | |
Hi All,
This is one of those “take advantage of the opportunity” projects.
Yesterday, 2 duo-therm 15,000 btu a/c units with heat strips fell off a truck on the way past the house. It's a very bumpy road. <vbg>
Now I need help.
I live in a 1976 MC8 "under construction" bus conversion in the Southern Arizona desert, yes, it's "warm" this time of year.
I know this subject has been discussed before, and I've read through the archives on framing the roof for mounting air conditioners. Mostly, they talk about doing it after the ceiling is removed. I don’t have that luxury, my ceiling and luggage racks are still in place.
What's the best way to create the roof openings in a MC8 with the original interior ceiling still in place? I don't want to cut the center spine and I don't weld. I can have things fabricated.
Can I use a sawsall to cut through the roof and interior ceiling at the same time?
How can the framing box be installed and connected to the roof ribs or center spine WITHOUT taking the ceiling down? Is it necessary? Will the a/c be stable enough if the a/c and framing box are just sandwiched between the roof and ceiling without being attached to the roof ribs or spine.
What's the best placement on the roof? Close to the ribs? Equally spaced between the ribs?
How far should the front unit be from the windshield? Where in the back, in relation to the rear hatch, should the second unit go?
Thanks for your help.
oh, install volunteer help welcome.
John
Hopefully, soon to be cool in AZ. |
Ed (Ednj)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 15, 2005 - 7:31 pm: | |
Don't do it.
The roof units weigh about 90 lbs. each.
That’s alot of weigh to be bouncing around
Unsupported.
If you can't weld in support. Then at least put them where the escape hatches are now. |
t gojenola
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 15, 2005 - 8:09 pm: | |
I think the framing box is a matter more or less independent from the term "support." At least on a 4106 the ribs are near enough together to be spanned by the air conditioner unit. I installed one Carrier unit this summer and the top unit has a very rigid bottom pan that spans two ribs. The bottom unit has a rigid steel frame that does the same thing on the underside. The two units are held together by bolts that go through the roof opening. Thus the "support" is provided by the ribs. I built a square framework of oak that fits between the inner and outer skins and around the opening originally cut out for a standard 14" RV vent. Both skins were attached to the frame with sheet metal screws around the perimeter. When assembled, the a/c unit is compressed against the framed opening, which keeps the two parts secure without placing too much stress on the top and bottom pans.
I think the main consideration is the placement of the opening with respect to the ribs. You should look closely at the bottom pan of the top unit and measure distances. Cut your opening where it will allow the support to rest on two ribs, if possible. If this is not possible, then a steel frame welded to the ribs would be the best alternative.
tg |
John MC9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 15, 2005 - 8:18 pm: | |
Prior to putting the roof airs on the roof, just about everyone
here told me to make a frame and install the units where the
escape hatches are. I fought like hell, but finally caved.
After removing the hatch door and cutting the lip that protrudes
even with the roof, some light hammering of the existing frame
was needed to even it all up.
I used 1-1/2 x 1-1/2 oak for the frame. It's real simple to
make. You'd want to design it to fit into the existing escape
hatch frame. The inside of the frame must be 14-1/4 x 14-1/4.
I screwed it to the inside of the existing frame. Short pieces of
lattice strip nailed to the inside of two frame sides, brought
the sides to the 14-1/4 dimension.
A heavy aluminum panel is placed over the opening, and
the opening outlined from the inside with a pencil. Cut out
the outlined area, give the panel a good heavy coating of
butyl, and screw it to the roof (and to your frame only if you
counter-sink the screws). It's then ready to mount the AC unit.
The hatch cover can be used, if you strip it of all rivets, etc..
But to tell you the truth..... it's more work than it's worth to
do that, and a whole lot easier to buy new aluminum panels.
The entire project is easier than you think!! |
Ed (Ednj)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 15, 2005 - 8:55 pm: | |
You guys are right on the money.
Thats what I ment by "putting them where the escape hatches are.
On the MCI the ac will not span the ribs.
In the hatch area there is more frame work that the ac will spand.
John thats the way, I didnt mean use the hatch cover.
I welded in metal no wood used. |
Jim Stewart (H3jim)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 15, 2005 - 9:00 pm: | |
I wanted to save my roof hatches, so I did what tgojenola did and I am quite happy with it. I am a little off center (so I've been told) because I did not cut the center rib, for the reasons you mentioned. Its not raelly noticable from the outside, but quite noticable from the inside. some find it objectionable, I do not. I'm really glad to saved my roof hatches. One is a great vent when I'm not using the airs, the other is an access to the planned roof deck. |
John MC9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 15, 2005 - 9:44 pm: | |
Ed-
"I didn't mean use the hatch cover"
We understood that! But the metal cover -could be- re-used
to cover the opening once it's framed. The lip would have to be
removed (or flattened), along with removing all the rest of the
rivets, etc.. I was going to try to save a few bucks by using it,
but lost patience.
Actually Ed, at the time I asked the question here (about a month
ago?), I was trying to see if I could use the hatch cover to mount
the AC to. My neighbor did it that way since then, but may change
it. The AC unit sits too high and doesn't fit properly inside, causing
a bit of grief having to modify the interior mountings. The AC unit
also does not fit properly on top of the cover, forcing the use of
some type of support for the front or rear of the AC case. Those
units were designed to sit flat to the surface. Any overhang is
detrimental to the AC structure and components..
To make it short, the guys that suggested doing it the conventional
way were right.... as usual. |
John Wardell
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, September 15, 2005 - 11:51 pm: | |
Thanks all for the suggests, keep'm coming.
Here's some more thoughts.
I have to keep the one hatch I have. One of my goals is to lose at least 75 lbs so I can fit through it and get to the, "to be built someday", roof deck. In the mean time is does make a great air vent.
Jim Stewart, what did you install the a/c on. Can you give some details on cutting the roof and ceiling, location in relation to the ribs, kinds of supports used, etc.
I guess the next adventure is the measure the roof rivets and figure out how the A/C's fit with them.
Thanks again,
John |
Jim Stewart (H3jim)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, September 16, 2005 - 12:56 am: | |
My interior ceiling was removed, so all I had was the exterior, which I cut with a sawzall. I later installed the 3/8 plywood ceiling, making the hole just under the hole in the roof. The sawzall could have just as easliy cut through both ceiling and roof, however you need to be more careful that your saw cut is straight up and down so as not to leave a gap on either top or bottom.
In the area where I put it, the ribs are quite close. I snugged the cut in the corner next to two of them. The other two sides I made an L out out treated wood, the right thickness and curvature to just fit between the ceiling and roof. One rib was about 2" from the hole , the other side of the L was about 4" from the hole. As you know, the air conditioner is installed by installing 4 bolts that go through from the ceiling mounting plate to the roof mounted air conditioner, clamping the entire affair. Since my ribs were so close to the hole, I did not otherwise connect the braces to the ribs, and it does hold quite nicely. The clamping action and the proximity of the ribs actually does support it well. I'm sure this will be roundly criticized, but it does work does not leak etc. when i furst put the air conditionaer up top, before i clamped it, the thin edge of the roof aluminum did sag down about 1/4 inch. When clamped, it pulled it right back up to perfectly even with the rest of the roof.
I really did have to hold my breath to cut a 14" hole in and otherwise perfectly good roof, but its what has to be done, and has not been a problem. |
John Jewett (Jayjay)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, September 16, 2005 - 1:09 am: | |
Experienced help is available and FREE, just send a major oil company credit card to feed the 4905 with, and I'll be right there. About 4 days drive actually. That's how I ended up in 'Vegas two years ago, MikeSS said he'd pay my fuel bill, so I packed up and took off (from Ft. Myers, FL.) Near Yuma? I've lived on "B" street (way out by 32nd ave.) And in the 8th Street RV and Mobile Home Park. Closed recently and re-opened with all park model homes.
Cheers...JJ |
David (Davidinwilmnc)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, September 16, 2005 - 9:51 pm: | |
I installed a Carrier in the front of my MC-8 a few months ago. My package trays were still installed. You can remove the trim strips around a ceiling panel. Then remove the screws that hold the gold-colored aluminum to the ceiling. The panel will slide up and out. It's much easier to run the wiring and install the frame this way. I have the A/C sitting where a cross piece joins the center frame. I used wood and angle iron to connect to the two smaller sections of framing. It seems to be very sturdy. Besides, how many MC-8's have front hatches? My '78 doesn't. |
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