Daffyduck528's comment about straight trucks being limited to 40 feet is important. Though, I know that exceptions have been made for devices that save fuel and make the truck longer.
Bob, a photo of Diane's and my truck is below. It is exactly 40' long as it sits. How might you streamline a truck like this?
Hi ATeam -
What a beautiful rig you and Diane have! I just love the nice clean look & the patriotic theme!
Please don't take this personally, as I am only commenting on the aerodynamics, and not on your beautiful, and obviously very high-quality rig. Aerodynamically, it's what we call "dirty" though. On the plus side, Volvo does wrap the front bumper around to meet the tires, which is a good thing. But the bumper itself is almost flat to the wind and has a very slight radius at its front corners. The radiator is almost 90 degrees flat to the wind, except for where they sweep it back slightly on the top radii. Your brackets and your spotter mirrors are very dirty, aerodynamically. The windshield looks to be close to the 65 degree to the wind industry normal. My current Chevy Impala LTZ sedan has a 32 degree windshield and a previous Chevy Z28 had a 28 degree windshield. Notice the 9
steps that the airstream has to travel to get over the top of the box:
1. - top of radiator, 2. - hitting bottom of windshield, 3. - hitting sun visor, 4. - hitting first lower hump of the sleeper, 5. - hitting the top of the first hump, 6. - hitting the lower part of the second hump, 7. - hitting the top of the second hump, 8. - slamming straight into the top of the box, 9. jumping over the top radius of the box. Whew. That air is sure expending a lot of its energy, and your fuel, doing that.
Notice also how Volvo makes the rear of the cab where it meets the sleeper narrower than the sleeper. Which itself is narrower than the box. So you're getting the same air-step type movement as you are with the airstream going over the top of the box, but to a much lesser extent.
Obviously, there are no modifications that we could do with your basic Volvo cab itself. But if it was my beautiful rig, I would:
Add full-length skirts
all the way to the extreme rear of the rig. This is assuming enough clearance between the tires and the skirts. If you have dual tires, this may be problematic. If you have wide base tires, this would be relatively easy. The stainless steel boxes for blankets , straps, etc. would have to be moved outboard to be perfectly in-line with the skirts. Or, the skirts would need access doors to be able to get to the supplies in the boxes. I assume the cab is of course air-ride and the box of course is not. So you need a small vertical air-gap between the skirts under the sleeper and the skirts under the box.
If there are dual tires, I would switch to Michelin X-Ones
and an ATIS (Automatic Tire Inflation System)
as a true run-flat solution that will keep the X-Ones @ at a constant 120 # for added fuel savings.
A rear of truck aero device is absolutely required for good performance, assuming compliance with FMCSA. I would add a 48-60" full-height
Aerodynamically and rolling-resistance wise, that would be the best one could hope for.
Please tell me about engine, cruise rpm, cruise speed, etc. There is a LOT
more to great mpg than just aerodynamics. But obviously, aero, is a big part of it.
By the way, I hauled LandStar
loads exclusively while testing the BulletTruck Last year. Every we mile we drove, except deadheading of course, was a LandStar revenue load. None of that test track crap. Real loads, real roads, I backed into every stinking small alley dock and other obstructions that everyone else does.