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40ft bus into RV aero
Alrighty everyone, I'm saving up to start converting a rear engine school bus into a full-time RV. We plan to do quite a bit of highway travelling, and aerodynamics come into play quite seriously for the brick shaped things both in terms of fuel economy and in speed given the usually sub 200hp engines pushing 25,000+ lbs of steel. I'm already eyeballing a rear extension similar to semi-truck trailer "tails", a smooth underbody (with storage!!) and wheel covers. What else you got? The bus will be 40ft long, the limit for an RV is 45ft, so we have a few feet to play with. Maybe something to smooth up the big flat face?
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Have you considered sloping the roof down before it gets to the back (sides too, if possible)? The longer you go, the more difficult it'll be to maneuver and to find parking. A lot of RV park and even forest service type sites have a length limit. Going with a collapsible semi trailer tail would definitely help with that issue.
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There's an old, slightly dirty joke:
Q: Why are turds pointy on the end? A: So your butt doesn't slam shut. The atmosphere doesn't like slamming shut. Any taper you can add to the tail is good. Since you're planning adding tail length, plan ahead to taper it. If you can extend that tapering further forward then you can make even more of a difference - the goal is to reduce as much of the absolute tail's cross section as possible, while still adhering to the ideal aero template (find it in the Aerodynamics sticky). Don't forget you can taper in the sides as well as the roof. You give up storage capacity but pick up a smoother, quieter ride and lots of miles per tank. As to the nose, increasing the radii of the corners is good. It doesn't have to be structural and you may be able to make that take the form of new rear view mirrors, or simple add-ons at the front corners below the level of the windshield. With the rear engine you can do all kinds of smooth underbody, which you already have on your do list. That will yield big dividends. Big, big project. When you start your build thread, I'll be subbing that. |
Welcome to Ecomodder.
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On a vehicle that size, I'd want a chipper/shredder/alchol still for fuel and a 'cherry picker' for extravehicluar activities or to hold up a tent. Skylights and solar panels? Rather than the external taper that is popular here, look to the annular ring and wheel well treatment on Dr. Morelli's urban car. You have a very favorable fineness ratio — 5:1 in plan and 4:1 in elevation! There is enough length for reattachment so you have clean air into whatever you choose to do in the rear. Also search for Mair and Englar. Also, commercial box vans will be getting plasma actuators. A ring at the back at least but any edge or wheelwell is a candidate. Your vehicle could benefit from many of these techniques from trucking: http://ecomodder.com/forum/member-fr...dynamics-c.jpg Note the passive porosity in lower left. |
The bus for this project hasnt been purchased yet. I'm currently in an '84 International Amtram 35 footer, but with the new lady looking to move in next year it's gonna get tighter. Looking to get into national parks and various fairs and festivals, fulltiming in it.
Sloping the roof: I was planning to likely have to raise the roof of the new bus at least a foot, as most buses are too short for my 6'1" head to fit under, and I will be adding insulation. But to add a slope, I've never seen that done on the skoolie forums. At first glance, that looks exceedingly difficult to pull off. And I want to cover the entire roof in solar panels with a "raise and tilt" mechanism, which would be harder with a sloped roof. I do plan to have fairings around the panels when in the stowed position. Plasma actuators?!?! Looks a bit far into the future, and having actually built HV "plasma" brown-effect lifter/fliers before, I can tell you the power consumption to move a small amount of air is pretty high. It took 25,000 volts at several watts to lift less than 3 grams. Weight: My current 35ft bus completely stripped down was estimated at 16-18,000lbs. Its gvwr is 32k. I havent put it to a scale yet, but these are typical numbers for this size bus. I have plenty of reason to expect Bus 2.0 to be up to 25k given it's longer length and all amenities fully installed, including a massive 48v battery bank and hundreds of gallons of water for long term boondocking. Occupancy time: 2-3 people, "as long as possible" I'm seriously considering an incinerating toilet running on the solar to eliminate the blackwater tank to make more room for gray and fresh water for example. Got a link to the Morelli car? Google isnt being forthcoming for me today. Chipper/shredder still? Wouldnt that be alcohol fuel? I dont think my diesel engine will like that much. ;) |
My 19ft Cortez weighed 7000lb. I compared to twice that, but the Cortez was the 'sports car' of motorhomes and didn't have a battery bank.
I wouldn't slope the roof, except for maybe the last 5-10ft. Instead of messing with the roof, I'd add one foot through the side window area and over the top of the windshield. Forum member PranayBajjuri only posted twice but he said: Quote:
It's not trying to lift the vehicle, it's an ionic wind — fast moving ionized molecules drag adjacent air along with them. I defer to slowmover on extended occupancy (we both live in our 35ft trailers, but mine is up on blocks and skirted), but instead of an incinerator, consider a 55-gallon drum batch composting system that swaps out through an external hatch. The chipper/shredder/still was a fantasy I had about parking a conventional cab bus on BLM land and cooking down wood slash. It would have had the chipper at the front bumper running off the engine with the chip blown through a 4" pipe into a bin on the rear roof. The (18" dia., 7ft tall) still would be in the left rear corner with the composting toilet in the right rear and a new rear wall 5ft ahead of the original rear door. What do you think of using a cherry picker as a tent pole. If it would reach 12ft to the side you could have a 24ft diameter 'big top' tent with a ring of wall poles. Morelli: Quote:
https://www.youtube.com/watch?v=CnHGKUh-5O4 He started with a flatbed truck with 8ft ram jacks at all four corners, and added pop-outs, slide outs and swing-outs. The cherry on top is the fruit drying rack in the 2nd floor ceiling. |
Not sure what you mean about adding a foot through the side window area...
Power consumption of 1 watt to move that much air still sounds suspect to me. My point about the flyer was it took much power just to move enough air to affect a little bit of balsa wood and tin foil. I can blow harder through a straw that that 25,000 volt device could blow, so I find it difficult to believe it can significant alter the course of a gail force wind on a vehicle. But I guess we'll see if it's ever actually installed on a truck ;) Part of my motivation for the incinerator vs composting was, if I dont have a permanant base location or somewhere to dump the partially composted waste, what do I do with it? That said, at the end of the day, the price might get me. What kind of cherry picker?? Seems there are many things called that these days... Personally, I was considering having a hinged cover, or another layer of solar panels, over the rooftop solar that folded out to form an awning over one side for extended shelter. So the Morelli "annular ring" you're talking about is a modified Kamm Back eh? |
One foot was your idea. Take out all the windows, cut the posts alternately at the top and bottom and raise the roof the height of the original window opening. Move it one window forward or back, or split it and move half each way and put a hatch in the middle. Connect the posts and stack pairs of windows. You'd have to panel in half the window openings with something else.
The windows in a school bus are too low when your standing anyway. ______ All the plasma device has to do is speed up the air locally, right at the surface, inhibiting separation. Then the air further away doesn't have to move as much; sort of like judo. If I understand correctly. One watt per meter sounds low to me too; but what do I know. At 25Kv that's milli-amperes. ______ I take your point on the composting toilet. Two 30-gallon drums? Ship them home via Fed-Ex? ______ By cherry picker, I meant a utility bucket. Except I'd want to replace the bucket with a lounge chair with a little umbrella. You could run it up inside an Apple tree and sit there to read books. :thumbup: Or place the 'forearm' parallel to the ground and throw a tarp over it to make a tent. Or use it as an engine hoist. ______ The solar panels are expensive but you could have an aluminized shutter that you could open to reflect more sunlight onto the panels, or as an awning. Split down the middle or hinged/latched from either side. ______ It's more like the Kamm-back is an incomplete Morreli 'fluid tail'. Kamm, Morelli, Hucho and Jaray are all authoritative. Look to aerohead's posts. Hucho talked about retractable tails. Here's my own attempt: http://ecomodder.com/forum/member-fr...pe-ii-boat.jpg |
Alternate-cutting the window posts is a brilliant idea. Cut the roof straight across right behind the forward cap and just ahead of the aft cap. Shift the whole roof upward and aft one window width. Cut out one window width worth of the roof at the rear and move that to the front, weld it back in at the front and reattach the front and rear caps in their appropriate places. That makes the cutting and welding all in straight lines around wide radii, about as uncomplicated a major body job as you could hope for. Of course you'd still have to come up with ways to close up the gaps that project would open up.
Maybe it would just be easier to cut the whole roof, jack it up and then weld in a band. As I recall those windows are significantly more than a foot high, so you'd pick up quite a lot of height that way, more like about 18". That's just excellent. That's an awesome idea. |
re: the roof raise, the way 90% of them are done on skoolies is to weld jacks to each corner, remove windows, make cuts on all the "hat channel" frame members that run beside the windows, then jack it up to desired height, level, and weld new iron in the gaps. The bus windows generally are leaky noisey things so most attach sheet metal over the gap then install a few RV style windows.
Bucket lift, LOL, sounds pricey on it's own, how would I mount it to the bus so it didnt severely disturb the aero? :P Aluminum reflectors for solar: While that would technically work and be cheaper, the higher operating temperatures that would result in the panels would both reduce their efficiency and their calendar lifespan. Would need liquid cooled panels ;) Something else that bears mentioning aero-wise: I'll likely be towing a little Honda Insight behind the bus as our run-about vehicle. |
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Bucket lift — I've wandered into that part of the Cosmos again. Sorry. maybe a weeny little robot arm? Here's what led me down that path, Luigi Colani's Sea Ranger: http://www.diseno-art.com/news_conte...-4-730x469.jpg www.diseno-art.com/news_content/2014/04/colani-sea-ranger-amphibious-insanity-1979/ The bucket/escape pod could hang over the rear bumper for aero. Reflector vs solar cells: the price of solar cells is dropping all the time. Insight: I'm stiill wondering about conventional vs pusher bus. |
I've read many pusher buses have a pretty hefty frame under the engine to the rear bumper, on the bus forums it's generally considered that they can pull thousands of pounds with a proper hitch. Of course I'll consider that when looking at buses.
RE pusher is kinda a must for me, for reasons of underbody storage space, driver's noise levels, and weight distribution. I'm tired of getting stuck on wet grass in my front engine bus bc there's no weight in the back!! "Escape pod" bucket mounted in the back suffers issues with the engine being back there too... I dont want to have to remove too much to work on it! :) |
What gets to me most about rigs like this is the sheer weight just to support a couple of people. Sure, folks ought to buy or modify what they want -- that isn't the question -- but rather from the perspective of design. Lighter means less fuel. Short of commercial reasons it's hard to justify
That said, my favorite RV bus is on DoItYourSelfRV in a post entitled, "Can't Miss Open and Airy Converted School Bus" An engrossing video. Second is the maintenance and repair costs. Nothing is inexpensive. From the towing bill to the hourly labor to the parts. Why I asked if there are commercial considerations. None of my business WHAT they are, just that --if so -- they must be able to pay for the thing. Offsetting fuel cost a minor amount won't do it. The beauty of some aero will be better handling. Fewer steering corrections. The long term average MPG should benefit, but one has to run a lot of miles for that to pay. The box cavity thread, post #8, is where I'd start. A neighbor of aerohead. Also on pickup wing thread in an October post. Look forward to any pics you may care to post. |
Yes, it's heavy. Compared to a stick and staple RV, it's also virtually indestructable. This isnt just for vacations, this is my HOUSE. I live in my '84 International right now, and it gets 8.2MPG foot on the floor at 60mph, which is actually better than many smaller gas RVs.
As far as expense, this is why I'm picky about my engine and transmission choices. My '84 has an international straight six DT466 mechanical turbodiesel. Extremely common, parts arent insanely expensive, and very reliable. The transmission is a MT643 which is rated for vehicles up to 80,000+ lbs, also virtually indestructable. I can work on this bus myself. I intend on getting a similar drivetrain in my RE bus. Why would I do aero? Personal mission. :P I'm going to be doing alot of body work anyways, with the roof raise and window delete. I will be building tons of storage underneath, might as well make it smooth. I've heard rumor of people getting these buses into double digit economy with gear changes and careful driving, I'd like to see just how far into double digits I can get. There's a huge difference between 8 and 12 mpg when you go cross country. |
My 35' travel trailer is my house also. With my truck it's full out 17-18000-lbs. 14-16/mpg towing. 24-mpg highway solo. I need two AC units, not 4-6. Still have 95-GPS fresh water. Washer/dryer. Etc.
I can change the tow vehicle any time. My point about size/weight was in line with practicality. Go back and re-read what I wrote. It wasn't a criticism of the choice. Mines not "better". But it's a helluva lot lighter. And will last as long or longer. Freebeards trailer is well past a half century. Mines a mere babe at 26. As you're altering sheet metal and structure, you really do have some nice options. And you should of examine aeroheads threads/posts on trailers for a bus type vehicle. So, grab a cold one and drink in the mysteries of the video above. |
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Re: Weight I've thought some about weight and aerodynamics and [for me] it comes down to "What's the largest geodesic dome you can stuff through the 8ft wide, 14ft tall hole mandated by the various highway departments." Here's my solution in 24ft and 40ft versions: http://ecomodder.com/forum/member-fr...-w-caption.jpg http://ecomodder.com/forum/member-fr...07-7-35-02.png Length width and height are variable. six tired tricycle on the 40 footer. I also applied the same geometry to a belly tank race car but that's off topic. |
Sorry I can't post link. Page 8 in bus section.
I'd also add see the road trailer rooflines by Don Burr. This site and ksewhere. |
My solution is cut it off at the bottom of the window line and build a super lightweight roof that telescopes in minutes about 18". Goes down the road shorter than the original, and has the proper taper at the back to make aero. Don't put air conditioners or traditional RV vents up there to make drag, and incorporate your tracking solar system into it.
Add a slide while you are in the cutting mood, but make it very light. |
What's worse, I couldn't even find the Bus section. But I allowed additional Google API scripts until site search worked. Turns out there are more categories than the 10 in the page header. It's under Builds, Buses and Popular. I'd call them tags.
Can't-Miss Open and Airy Converted School Bus. Plus an Awesome Shower Rod Idea. I think it has the same problem as my Airstream, the curve above the windows means they are positioned well for sitting down; but standing, they are too low. And the 360° windows might be nice in the mountains, but in an RV parks? What makes my park living tolerable is the side windows are 80% blocked (opaque or transluscent) and there are four 14" skylights. I found a bus that uses the plan I proposed: 1990 Thomas School Bus Tiny House With Wood Burning Stove http://www.doityourselfrv.com/wp-con...school-bus.png Window area is not reduced. There's a lot of interesting stuff on that site. I'll have to look around some more. :thumbup: Edit: aerohead left this one out, also apropos of skyking's suggestion: http://ecomodder.com/forum/member-fr...off-camper.jpg Note the simple curves, and the horizontal edge at the front and vertical edge at the rear. |
Speaking of slides, etc, if I built a seldom-moved mobile dwelling, I'd put all the hardware along one side, and put big doors in the other, leading to a fold-down deck. The deck would be enclosed with half arches from the commercial greenhouse store, with two layers of polyethylene inflated to an insulating pillow wall. Assembly or packing would take a few hours, but a greenhouse is a lovely space for living and solar gains. On cold nights, the doors would be closed to save heat.
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It would be slow to erect and dismantle.
https://emergencyroof.files.wordpres...2014/06/01.jpg https://emergencyroof.wordpress.com/2014/06/ When you open the door to inflatables, it put me in mind of: Antfarmhttp://golancourses.net/2010spring/w...PM-600x420.png Special Topics in Interactive Art & Computational Design » Looking Outwards – Ant Farm Here's their Inflatocookbook as a PDF. Frei OttoAlthough most of his work was tents, like at the 72 Munich Olympicshttps://en.wikipedia.org/wiki/Frei_Otto http://1.bp.blogspot.com/_HMTcR_29J-...hqA/s640/7.jpg http://mondo-blogo.blogspot.com/2010/11/blow-me-inflatable-art-architecture-and.html Haus-Rucker-CoThe 'house wrecker company' http://3.bp.blogspot.com/_HMTcR_29J-...G08/s640/9.jpg MONDOBLOGO: blow me: inflatable art, architecture and design The Dyodonhttp://4.bp.blogspot.com/_HMTcR_29J-...ijQ/s640/5.jpg ibid Not to mention Archigram, Frank Lloyd Wright, Walter Bird and others. |
Hmm. - my friend must have had a rare setup - I can't find any images. The idea is to use arches with a shallow channel to support two layers of poly, with a tensioned member over both layers at the ribs, drawing them down into the groove. Air is blown into the space between layers of poly to separate them, and give the general topography of a cheap, stitched sleeping bag. The inner layer bulges in, and the outer layer is all convex. Being taut, it won't flap in the wind. More layers could be arranged. Air-supported buildings are rather wonderful, but different, requiring an air lock entrance.
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Whelp, that post took my an hour already so I skipped over Frei Otto. Mostly because he's most famous for things like the 1972 Munich Olympics:
https://i.kinja-img.com/gawker-media...xde4ypkjh7.jpg http://gizmodo.com/the-best-of-frei-otto-the-architect-who-engineered-the-1690783540 His definitive work was in two volumes, on Pneumatic and Tensile structures. Pneumatics are of two types, air-locked as you describe and air-supported.The modern epitome of what you're thinking of would be a geodesic mountaineering tent with the fiberglass poles replaced with high pressure tubes. ​Can Inflatable Poles Make Better Tents? |
Aye, I'm quite fond of pressurized tubes for a framework, and they would be wonderful for nomadic use, but I like to buy components when I can if they save time over the expected lifespan and use. Someone once made a radically light and stiff bicycle frame using beer-can spec aluminum for the tubes, with air pressure to prevent local buckling.
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http://0prx9.com/inflatableimages.co...y_sebring5.jpg
Corvette Racing Deploys New Inflatable Paddock - Corvette Online http://www.campingworld.co.uk/Images...ir-comfort.jpg Outwell 2016 Tent Collections & Camping Equipment And to get back on topic. Just about every way to make a big box have less drag has been discussed here. I assume the OP did a search like this one: Google image search of this site |
That Corvette Racing paddock is something right out of Archigram.
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