Quote:
Originally Posted by Shepherd777
Hello All -
I have not been spending much time at this forum, even thought I really, really enjoy it, and all of the clever ideas, experimentation, and DIY projects.
I am not overly interested in reviving this dead-horse of a thread, but I felt that I must address a recurring falsity that I have seen on the internet. And I feel this forum has very broad depth of intelligent viewership to make this following point. I have seen everyone from a spokesman of one of the big truck OEM's, to fellow Ecomodder members opine on this subject.
That subject being that we extended the length of the BulletTruck in some sort of fool-hearty and misguided effort solely to help with the aerodynamics. Nothing could be further from the truth.
We always knew that we wanted to do this retrofit prototype by lowering the cooling system package from its stock location. This was accomplished to somewhat negate the horizontal phone booth hood look and aerodynamics that a lot of Class 8 trucks still have. And this way, we could provide a beautiful curved aerodynamic slope to the top of the hood. Please scroll up to the top of this Ecomodder forum page and check out the red conventional rig and its hood if a refresher is necessary.
The stock OEM location for the cooling system package (radiator, shroud, charge-air- cooler, A/C condenser) is mounted on top of the most-forward front crossmember. So to lower the cooling system we had to hand-build custom rubber-mounted cooling system brackets in front of the frame and that crossmember. This is the only way we could substantially lower the cooling system package for the hood slope we were looking for.
Additionally, we had to position the rear of the radiator forward enough of that crossmember so that the hot air expelling from the rear of the radiator would not slam directly into that crossmember, and block the air flow.
We also had to add a FMCSA (Federal Motor Carrier Safety Administration) mandated, and subsequently approved, horizontal 4" square steel tube bumper in front of that new cooling package. The bumper wraps around the cooling system package and ties directly into the truck frame for structural integrity. All of these component requirements necessitated that the front of the body be extended to envelope the components. It also created a lot of body overhang, forward of the front axle. This was not really an operational issue as we have shown that the overhang is equal to some very expensive motor-homes.
So in a nutshell, we extended the front of the BulletTruck not for aerodynamics, but for component packaging.
Compromises always have to be made when doing any retrofitting.
Our next-generation Class 8 rig (assuming we ever get the funding) will not have this extended and pointy look in the front end, or the body overhang.
Just wanted to clear that up. Thanks.
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After gleaning "Aerodynamiks des Kraftfahrzeugs",by Baron Reinhard von Fachsenfeld,I'm less dismissive of the 'Pointy' nose.
In his drag tables he illustrates a 'Reverse-Template',streamline body of revolution of 6.5:1 fineness ratio,running tail-first into the wind.The tests would have been performed at the FKFS wind tunnel under the supervision of Dr.Wunibald I.Kamm,whom ran the organization.
The Cd wasn't as low as the 'nose-first' body,but it was within about 15% if memory serves me.
Outward vision would be an obvious issue (internal reflections on inner face of windshield),but for a DOT-approved 48-inch rigid boat tail rig,or 60-inch inflatable boat tail rig,this nose configuration could have merit.
Without the 70% 'Template' boat tail,the 'pointy ' rig might achieve on the order of sub-Cd 0.16.Not shabby for an 18-wheeler.
Oskar G.Tietgens,of Westinghouse Laboratories had demonstrated a self-propelled railroad car of Cd 0.08 in the early 1930s.The car had a 'pointy' nose,and abbreviated boat tail.
Bob,thanks for all you and your team has done,and for sharing all the gory details.Hope you find $$$ for the next-gen rig project.'will be watching.
