By this point your probably saying "this guy has an awful lot of potential projects..." >_> That's right! But they are planned to be real, they're just at least 1-2 years off as of yet (nowhere to do such things living in the city, too busy with college, once I have access to rural land there will be space to park project cars, collect scrap aluminum or make fiberglass molds to make into aero shapes, and similar) and at varying priority levels - the need for high MPG daily driver is more than the need to move heavy stuff.
This is one I wasn't even sure whether or not i'd ever consider feasible, but got inspired after seeing the Airflow Bullettruck, and also after finding out that insuring one for personal only use isn't much more than a normal pickup so it's back in the realm of quite possible again. Basically any project that pays for itself is far more likely to get done - and as the vehicles get bigger (or the mileage needs get longer) the payback becomes faster. The 5mpg of typical semis if improved could save hundreds of dollars per couple hour trip.
Whatever I come up with i'd plan to Open Source - including CAD files if I ever generate any.
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The majority of the project would focus on aerodynamics, simply because I don't think I will have the budget anytime soon to experiment with the rest of the equation. (swapping transmissions, free choice of engines, etc.) Basically i've seen semi trucks for sale in working condition for as low as $1700-4000 or so and whatever I get is whatever I get. I have a need to do maybe 15-40 trips planned, maybe a third of it deadheaded/bobtail, with a total mileage of maybe 10-20,000 miles for personal use. (primarily being hauling construction material for an intentional community project) At 5mpg i'd use 2000-4000 gallons, at 10mpg (what I hope is at least possible) it saves 1000-2000 gallons, basically paying for even a $4000 rig even at the minimum miles. Any use beyond that is basically additional $ saved. If I reach 10mpg with v1.0 i'm happy. If I do a few commercial for hire jobs i'd be willing to try the same stuff on a newer, slightly better specced out semi and would try for 15mpg.
The eventual use of the rig for other purpose (ie for hire) is entirely possible but not necessary to build it. (I wouldn't mind at all doing small occasional jobs for side cash but I have no desire to be a trucker for life.) Because i'll be starting with an old beater semi i'm willing to do fairly radical things without caring too much what it looks like. It's possible that a v2.0 semi will reach 15mpg if I can spec it out more directly rather than picking the bottom of the availability barrel.
So this is an all purpose brainstorming thread. Share whatever opinions you got about ways to do things.
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AERODYNAMICS: Everything goes here, and should be assumed. Full boattails for tractor and trailer. (trailer may have legal length issues for the 53ft length trailers tho - suggestions? I'd rather not overlength permit for every trip) Aero treatment for bobtailed/running without trailer. (something collapsable) Aero treatment for different loads - a few box trailer loads, a few flatbeds, the flatbed loads would have some kind of improvised aero treatment. (another thread suggested fiberglass poles and tarps to wrap around objects - if flapping isn't a problem or wouldnt be too bad with enough points of structure that's possible, something like tinkertoys to make a rounded frame around hauled objects :P ) Tractor-to-trailer aero connection of some sort. And hoping to either avoid the 'tall' sleeper cabs and similar air deflectors, theyre fine for box/van trailers but not everything hauled will be a box trailer and it's a detriment if you haul something shorter. I'd like something adjustable to do the same job (while connecting aero to the trailer) when it does have a van trailer behind it though.
But some decisions once made cant be easily changed later. For instance, whether a flat nose/cabover has an advantage or a disadvantage to a conventional is open to discussion - for the very old and cheap class it's about half and half what turns up on the used market. But if it's a big aero advantage I might want to limit it due to that even if the other is a good deal, since I spend more on fuel than the truck anyway.
Whats the best overall shape to assume? The Airflow Bullettruck is one way to do it, are there others? Are there better shapes than the long slow slope up?
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THE REST:
Travel speeds may well be as low as 40mph unless it pisses off too much traffic, a max planned of 55mph. I have more time than money when hauling for personal reasons and fuel saved matters more. Longer trips may have to be 55mph. I'd at least like to experiment to see what kind of MPG difference by dropping to 40mph achieves.
Possible cruise RPM's probably will vary with what engine is available - it seems under 1200rpm wont work though since torque of essentially every engine drops off pretty radically below that normally. Even 1200rpm may be too low (driveline vibrations and such) and I may have to choose one rig over another based on the ability to tolerate that, hopefully if it tolerates it unloaded it will tolerate it loaded or it'd be an unwelcome surprise. :P (OPINIONS REQUESTED: What engines are or are not suitable for under 1600rpm loaded cruise in a big rig?)
Engine choices may be up to what's actually available rather than what I ideally want. Reliability and lower repair costs matters more than absolute lowest MPG as well - getting a breakdown with the cost of big truck repairs could kill the whole project. If I get something 1993 or newer i'd try to find a Detroit Series 60. (0.311 BSFC minimum at 1550 RPM, not sure what is at lower rpm though. OPINIONS REQUESTED: is anything more efficient? Or at least more efficient at 1200rpm? Impression I got is after 2003 engines just got worse due to emissions regulations, and haven't improved BSFC figures at all)
If I got something older i'm actually considering Detroit Diesel 2 strokes like the 71/92 series. This may be a little controversial, but for instance the 8v92 apparently has 0.345 BSFC minimum at 1700 RPM (again not sure what lower rpms have, i dont have a chart just a number) and although i'm sure there's better stuff, the series 60 is only 10% better.. the Detroits have a reputation of being reliable (though this is also controversial) and they seem fairly common in the vehicles that have shown up so far. (OPINIONS REQUESTED: Anyone knowing the history of trucking engines about who the winners or at least better competitors were around what age from 1970's to today feel free to chime in, whether the fuel mileage leaders or most generally reliable and cheap to fix. Keep in mind i'm more afraid of a mechanical problem and it's potential costs than I am another 10% mileage.)
One thing i'd contemplated, but may or may not be possible, would be the swapping of a non-big rig engine in the future. With overhauls of semi engines costing some $16,000 and up typically and big rig repair costs in general being high, i've wondered if there are alternatives like using medium duty engines. The slow speeds, lighter weights and reduced aero loads I expect don't require the power levels of a normal semi. The BSFC of smaller engines is usually higher, and the lifespan wouldn't be as long under the higher loads, but when I can rebuild or replace with another used engine for a tiny fraction it removes the variable of a serious engine problem offlining the rig. Does anyone think this would be viable? It probably wouldn't be an option if I pulled for hire loads but then income from that would pay for the difference in cost.
Other things like Super Single tires instead of the twins would depend upon cost - i've read a solid 2.5% improvement in fuel efficiency due to less rolling resistance, but i'm hoping to not have to spend thousands to replace tires and wheels when i'm focusing on much bigger economy improvements.
A suggestion of how to add precise instrumentation to an older engine without electronics is desirable, if I end up with one of those detroit 2 strokes. If I cant measure I dont know what works.
Although I have a number of nonaero questions in the rest of this thread, the aero basically drives the most important and first decisions for the rest of it, hence I posted it in aero. If it belongs in General a mod can move it though.
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