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Author Topic: Need advice on sinking Motosat satellite dish into RTS roof for clean roofline  (Read 5333 times)
Kevin Warnock
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« on: February 05, 2008, 06:57:55 PM »

I have a Motosat F1 Internet dish for my MCI 5. This is the kind that folds down for travel and comes up and finds the satellite at the touch of a button. Here is a link to the installation guide on the Motosat website:

http://www.motosat.com/downloads/internet/documents/installation/datastorm_installation.pdf

I am converting a 1994 RTS with a factory Series 50, and I plan to move my Motosat dish to the new bus. So far, I have nothing showing from the ground on the roof of the bus, as I went with mini splits for the AC, and paper thin flexible solar panels to keep the batteries topped off during storage. When done, I want the bus to look like a bus, and not a conversion, thus I am leaving all the windows and doors as is, and there will be no cuts in the sides either.

I think the RTS is a fantastic looking bus as is, and I don't want to ruin the lovely lines with a satellite dish on the roof. So, I have an idea, and I would like your thoughts on how to make it work.

I am thinking about recessing the dish over the bedroom. This is the section that has the rear roof emergency escape hatch. I would cut a bigger hole, as required by the Motosat dish. The manual specifies 54 inches long by 40 inches wide. There is in fact 54" available according to my measurements. The dish is 10 1/2 inches high when stowed.

Then, I would build a box without a lid and mount that in the hole. I would then make a mechanism that could raise the dish out of the box vertically so that the base is flush with the roof exterior.

To prepare for driving, I would stow the dish and lower the entire mount into the box. To prepare for surfing the Internet, I would raise the mount out of the box and push the button on the Motosat controller to raise the dish. There would be no lid on the box.

Here are my questions:

1: Can the RTS stand having a 54" x 40" hole cut from the roof where I plan to do it? If not, what kind of bracing do I need to construct, and with what materials and assembly techniques?

2: How will I make such a box watertight so I don't get rained on while sleeping? My thought was to have a welder weld a box out of metal and put a drain in the bottom, to be drained via a pipe that would exit through the floor of the bedroom.

3: How would I make a mechanism to raise the satellite mount, which weighs 105lbs? I see Northern Tool sells powerful linear actuators like this one: http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200333243_200333243 that might be helpful. If I got three of them, could I count on them all going up and down at the same rate over time, so that I could just power them on to raise the mount and again power them on in reverse to lower the mount? I worry about them going different rates and the whole thing binding and getting stuck.

4: How can I make the elevation mechanism as shallow as possible so I don't lose too much headroom in the bedroom? If I didn't care about headroom, I could use a motorcycle jack like this one:

http://www.partsamerica.com/ProductDetail.aspx?MfrCode=PBI&MfrPartNumber=640753

This has the big advantage of being cheap and it won't bind going up or down. It also appears very heavy duty, and won't have any trouble with a 105 lb mount. It also looks like it would hold the mount in the wind safely at highway speed if I forgot to lower the mount. I think it supports 1500 lbs. But it's ungainly, and I'm not sure how I would operate it remotely, since I don't want to climb on the roof to raise and lower the mount.

If I use linear actuators, I think I can put them outside and make a bracket such that they can be beside the mount when lowered, not under it, so it would seem much easier to make the mechanism low profile.

-----------

Finally, the dish uses GPS to orient itself, so I don't have to worry about magnetic fields of whatever I come up with. Originally when these came out they did use an electronic compass, but now they don't, and my unit has been upgraded to the 7000 series modems and has the new upper control board.

The Motosat dish is an amazing device by the way. I was a beta tester in 2002, and the company has always been good to deal with.

I realize this project is somewhat challenging, but less so than adding a slideout room or raising the roof I think, so I'm pretty sure it can be done.

What do you think? Comments? Suggestions?

Thanks!

Kevin

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tekebird
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« Reply #1 on: February 05, 2008, 07:45:59 PM »

sell your unit and get one of the low profile jobs.

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TrevorH
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« Reply #2 on: February 05, 2008, 07:46:51 PM »

what about water, etc drainage?
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1987 MCI 102A3 8V92TA 5 spd MT
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Kevin Warnock
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« Reply #3 on: February 05, 2008, 08:06:11 PM »

To my knowledge, there are no lower profile mobile Internet satellite dishes that find the satellite automatically than the Motosat F1 dish I have now, at 10 1/2 inches high stowed.

Is that correct?

I know there are plenty of low profile TV reception dishes, even 2.5 inches thick.

I like the Motosat because I already own it, and I get over 1 meg per second download speed, and about 300K up. I also like it because I can get TV on it as well, something I can't get with a wireless card, which has very limited coverage outside of big cities. The Motosat will work everywhere in the US where you can see the sky properly. But if I'm not aware of a lower profile send/receive Internet dish, please let me know of it.

Thanks,

Kevin
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TomC
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« Reply #4 on: February 05, 2008, 08:07:06 PM »

Instead of sinking it into the roof and possible compromising the integrity of the structure, why don't you just mount it on the roof and then extend the wall line up a foot or so then if you mount roof air conditioners on the roof they too will be hidden.  Then you could have a roof full of antennas, air conditioners, Fantastic Fans and nobody from the street will see them.  Good Luck, TomC
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« Reply #5 on: February 05, 2008, 08:21:30 PM »

I share your love of the RTS's lines.  I have one too.  I don't plan on satellite currently so I haven't given it much thought.  Tekebird stated what is definitely the easiest approach for satellite TV.  Offhand I don't know if they have them for Internet as well.  With all the high tech limo's out there, I am surprised if they don't and would bet it will be right around the bend.

Structurally, I would be very nervous cutting it, since, the RTS shell is inherently load bearing, especially from the engine bulkhead forward.

Are you keeping the over the road air conditioning?  If not, you might be able to do somehting with the space over the engine where the condensers air handlers were.  I don't believe the roof in that area is such an issue, there would be plenty of height available for a lift system and you wouldn't have such an issue with water drainage.

« Last Edit: February 05, 2008, 09:42:37 PM by HighTechRedneck » Logged
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« Reply #6 on: February 05, 2008, 09:24:18 PM »

I don't really suggest that you cut the structure in the rear section. All of the mono-structure is tied in around that back section.

How about removing the road air section and recessing the rig into the rear fiberglass cap area.
then you would have plenty of room for mechanisms and space for other items.

Keep in mind that fuel mileage with the 100,000 btu road air will suffer nastily..

My RTS went from 5.6 mpg to 3.3 with the road air dragging the engine down.
That extra 750 lbs of air handler takes up a lot of space. Of course that is only
assuming that you still have the factory air.

As for keeping the original windows.... Nah.. Take them out and install aluminum skins.
also would help keep the smokies off your back, If it Looks like a Bus, It's a bus.
The original windows also can cause serious heating and cooling problems.
The rubber hinges will eventually leak and mold will get inside. Been there , done that..

Good Luck in any case....

Dave...
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« Reply #7 on: February 05, 2008, 11:01:25 PM »

Kevin,

(1) There is no need to have a mechanism to raise and lower the whole assembly.  When the dish elevates to operating position, it should be well clear of the roughly 10" recess you will need to make for it to stow out of sight.

Also, you don't need the full 55x40 area to be recessed.  Ditch the mounting "plate" and just mount the rails.  Now you can make your recess keyhole-shaped, like the dish itself.

(2) There is absolutely still a magnetic compass in the mount -- I don't know where you got the information that there isn't.  GPS can only provide position, it can not provide orientation.  The positioning algorithm requires both inputs to find the satellite.

(3) The F1 is the lowest profile internet dish on the market today.  However, expect lower profile solutions in the future, such as those based on the BGAN system.  I'm not sure what tekebird was trying to suggest.

I don't think the DataStorm will fit in the rear cap as Dave suggests.

-Sean
http://OurOdyssey.BlogSpot.com
DataStorm F1/D2/DW7000 on AMC9 at 83W
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Kevin Warnock
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« Reply #8 on: February 05, 2008, 11:26:48 PM »

Sean,

Thanks for your comments. Do you think recessing the mount will interfere with the magnetic compass?

I was under the impression that the electronic compass was no longer used because when I activated the Motosat system with the new modems, I didn't have to orient the bus one way and them flip is 180 degrees like I did in 2002 when I activated the first modem/controller system. Nobody actually told me the compass wasn't used at all... I incorrectly assumed that since I was told that I didn't need to reorient the bus to calibrate. My mistake. But now I'm worried if I recess the mount that the compass will be confused. If I elevate the mount I think I'll be OK, but I love your comment that maybe I don't have to build an elevation mechanism, which would be a project.

With regard to others saying not to cut into the roof, I don't see how the part I plan to cut is that critical, as it's all sheet metal there. I won't need to cut into any of the heavy square tubing at all. There is already a big hole there in the roof for the escape hatch, so I am just making the hole larger. With Sean's comment to make a smaller, keyhole shaped hole, the cutting would be much less than I spoke of earlier, 54 x 40".

I would think having the box made out of 1 1/2" square tubing, and welding that to the opening, that would be plenty of structure to replace the removed sheet metal in that area.

Nobody has commented about what kind of metal to use. Do you think plain steel is OK, painted well of course? I was thinking the outside interior of the box could be lined with fiberglass, like I was making a water tank with plywood walls. That would seem to be very waterproof.

One thing I have to guard against is the drain clogging up and having the Motosat submerged in 10 inches of water. Any ideas on the best way to accomplish that? I was thinking a large grate, a square foot or larger, feeding a 2 inch drain pipe leading through the floor of the bus.

Sean, I admire your bus very much, and read much of your fantastic website a few years ago. Your bus really is a work of art, and more appealing than a $million five Marathon.

Kevin
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Sean
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« Reply #9 on: February 05, 2008, 11:51:02 PM »

...
Thanks for your comments. Do you think recessing the mount will interfere with the magnetic compass?


No, not really.  The metal of the bus will have an effect whether the mount is recessed or not.  The "compass calibration" that is part of the setup is intended to allow the system to compensate for the effects of the bus on the compass reading.

Quote
I was under the impression that the electronic compass was no longer used because when I activated the Motosat system with the new modems, I didn't have to orient the bus one way and them flip is 180 degrees like I did in 2002 when I activated the first modem/controller system. Nobody actually told me the compass wasn't used at all... I incorrectly assumed that since I was told that I didn't need to reorient the bus to calibrate.


The new software has an alternate calibration function that basically takes a compass reading, rotates the dish some, takes another reading, and so on, and builds a "map" of deviation from that and does the compensation that way.  However, it is still recommended that you take the time to do the old fashioned, flip the whole bus around type of calibration, as that is more effective.

Quote
... But now I'm worried if I recess the mount that the compass will be confused. If I elevate the mount I think I'll be OK, but I love your comment that maybe I don't have to build an elevation mechanism, which would be a project.


I don't think the compass will be any more confused with the mount recessed.  The compensation may very well be different, which is why you will need to do a calibration.  Also, remember that the search algorithm already assumes some compass error, which is why there is a fairly larger azimuth "window" during the search.

Quote
With regard to others saying not to cut into the roof, I don't see how the part I plan to cut is that critical, as it's all sheet metal there. I won't need to cut into any of the heavy square tubing at all.


I'm the wrong person to comment on this, since I know virtually nothing about RTS's.  That said, any time you have a frame-less coach, the structural loads are being carried by the sum total of the body trusses and other members.  It is often not apparent how the loads distribute through the body members without the review of a structural engineer.  Modern engineering methods call for finite-element analysis to really do the job right.  I would say you should really make sure you know what you're doing before cutting through any tubes, and any loads that are being carried will need to be picked up somewhere else.  Remember also that not all loads are compression -- some will be tension, and others will be shear.  If you do cut through a load-bearing tube, you'll need to know which way the load is normally carried in order to (1) unload the tube before you make the cut and (2) reinforce the area to pick the load up into other members.

HTH,

-Sean
http://OurOdyssey.BlogSpot.com
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« Reply #10 on: February 06, 2008, 02:56:12 AM »

A couple of thoughts. I would look at mounting the unit ACROSS the rear cap. With the A/C unit gone there is lots of space and I don't think mounting crossways will make any difference in working. That way you can permanently construct a box of stainless and not have to worry about raising it. Just make sure it will clear on erection. Perminate stainless box is the way to go - even leave drain tubes to the rear or better yet down thru engine compartment. I am doing an EL3 now and it has a recess for the TV sat dome in the same location that I am thinking about for the motosat. I think your rear cap is fiberglass so use the box for strength and mold the fiberglass to shape.
Good luck - sounds interesting.
JimH
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« Reply #11 on: February 06, 2008, 07:59:41 AM »

First, Sorry.. Didn't mean to insult anyone.

The Skin on the roof of the RTS "is" the lateral structural element.
It keeps the section across the bow of the roof under stress.

It may or may not affect the integrity of the section but if you cut the
areas that are doubled up ( ribbed ) you risk weakening something.
The roof hatch areas are part of the original equation in the design.
Changing, enlarging or removing may have undesired effects later on.

Maybe locating one of the carrier or other brands of housings that cover the a/c units
on some of the newer buses. ( that long low profile module on the roof ) would work
better." Da' Hump' "?
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« Reply #12 on: February 06, 2008, 08:40:20 AM »

Well, I got curious and did a google search and came across this:

RaySat StealthRay

They don't mention consumer applications for the 2-way data version on their site, but this proves the technology exists.  Further googling may find a consumer oriented solution.  The google search string I used was:   "low profile" "mobile satellite" internet

It will probably be expensive, but so would the engineering study to assure good results.  And it would be even more expensive if alterations to the bus roof did damage it.  I know it sounds strange that so much load is transfered through the skin of the roof, but it all works together to distribute the load.  GMC busses, and especially the RTS are built entirely different from the way Eagles or MCI's are.

All that said, the suggestion from busguy01 sounds like a good one.  Look at transverse mounting in the rear cap.  Should be plenty of room if you are taking out the road air.

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« Reply #13 on: February 06, 2008, 10:13:38 AM »

With regard to mounting the unit cross-ways:

Yes, the unit will function properly when mounted in this direction, as the internal compass reads the orientation of the mount, not the vehicle.  HOWEVER, the mount was designed, mechanically, to travel base-first.  The effects of airflow across the stowed mount in any other direction may cause problems.  At the very least, I would expect the very flimsy fairing over the feedhorn to tear right off.  This may ultimately lead to weather pressure on the drumhead, which will eventually cause moisture in the feedhorn.  After nearly four years of use (and knocking the feedhorn off the dish on a low overpass -- don't ask how), I have a small amount of moisture in mine, and it's a pain in the butt -- I need to go up and tap on the drumhead sometimes to get a good signal.

With regard to the StealthRay:

I should have written, earlier, that the DataStorm is the lowest profile consumer terminal.  Note that I did say that I thought there would be lower profile designs available in the near future.  FWIW, the StealthRay will not work with consumer services such as HughesNet and Starband.  Even the smallest HughesNet terminal, which has a 74cm elliptical reflector manufactured by Prodelin, has an antenna gain in the neighborhood of 58dB.  The StealthRay has an antenna gain less than half that, at around 28dB.  (No surprise, as the antenna has about half the aperture.)  So even though the product could, theoretically, be aimed at the HughesNet birds, and claims to be "modem-agnostic", none of the subject transponders' ground footprints has an EIRP high enough for the terminal to work.  You could, in theory (although not legally) put an external high-power BUC on the terminal to get the required transmit power, but the receive sensitivity is entirely a function of the modem, and the DW7000 is not user-adjustable -- Hughes has them locked up tighter than a drum.

Note also that the StealthRay (and other, similar products from other vendors) is also nearly 6" tall -- a bit over half the height of the DataStorm in the stowed position.  If the objective is for it to be completely unseen from ground level, it will still need to be recessed into the roof,, just with a shallower recess.

YMMV, etc.

-Sean
http://OurOdyssey.BlogSpot.com
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« Reply #14 on: February 06, 2008, 10:33:57 AM »

Correction to my last:

I overstated the gain of the .74m Prodelin dish (I was looking at the wrong spot in the chart).  The correct gain is about 38dB.  Note that the dB scale is logarithmic, so this is still a huge difference from the ~28dB gain of the StealthRay, which will still not work with HughesNet or StarBand.

-Sean
http://OurOdyssey.BlogSpot.com
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