Teardrop roof for boxy SUV?

[Cd]

Good point wink.

[cfg83]

aerohead -

Originally Posted by aerohead

I think they are lowering both the leading and trailing edges rather than raising the roofline.Daimler-Benz is too smart to believe adding frontal area could benefit drag.Trailer flow is typically fully attached with conventional trailer design.Their 95-square-foot wake is the issue which lowering would address.------------ PS "teardrop" is used out of context,as in a real teardrop form,the sides would be converging in direct proportion to the drop of the roof.

They are claiming "10% additional load space", so I think it is bigger on the whole. They are also stating bigger frontal area here :

Increased Load Space And The Effect on Aerodynamics

                 STANDARD   TEARDROP
                 TRAILER    TRAILER    % VARIANCE
Speed 56mph 
(constant m/s)    25.03      25.03     
             
Cd: Drag 
Coefficient 
(est)               0.7       0.4        -42.86
             
Width               2.55      2.55    

Height              4.0       4.5

Frontal Area       10.2      11.48        12.5

Fd 
(Force of drag) 2,742.08  1,762.77       -35.71

In terms of practicality, I think this is a "from land-to land" design. It' won't work on container ships and double-decked trains can only allow them on the "top bunk", so to speak.

CarloSW2

[aerohead]

Originally Posted by cfg83

aerohead -



They are claiming "10% additional load space", so I think it is bigger on the whole. They are also stating bigger frontal area here :

Increased Load Space And The Effect on Aerodynamics

                 STANDARD   TEARDROP
                 TRAILER    TRAILER    % VARIANCE
Speed 56mph 
(constant m/s)    25.03      25.03     
             
Cd: Drag 
Coefficient 
(est)               0.7       0.4        -42.86
             
Width               2.55      2.55    

Height              4.0       4.5

Frontal Area       10.2      11.48        12.5

Fd 
(Force of drag) 2,742.08  1,762.77       -35.71

In terms of practicality, I think this is a "from land-to land" design. It' won't work on container ships and double-decked trains can only allow them on the "top bunk", so to speak.

CarloSW2

So much for my pea brain! They definitely upped the frontal area.When Fruehauf did their "high-cube" trailer combo in the 1980s,they also increased area.Since the rig was so clean,even with the extra frontal area they still netted less overall drag,better mpg,with extra cargo to boot! Not a bad business plan.Would these clear U.S.A. bridges and overpasses?

[McTimson]

I doubt those things could pass in the US. Trucks are close enough as it is, it'd have to be a pretty small increase in height to make it work. Half a meter would be too tall, I think, but that's just based on what I see.

[rainyday]

If you doubt the US will pass it, then it'll probably take at least 10 years.

[DON-BUR]

My name is Richard Owens and I represent DON-BUR, the manufacturers of the commercial Teardrop trailers.

We have done considerable work on the shaping of these vehicles and I wanted to clarify a few points.

1) The UK standard height for a trailer 4.2m. The Teardrop standard is 4.5m - a 300mm increase in height and proportionate frontal area. Since the initial launch, we have now improved the range of Teardrop designs, catering for European/US height limits of 4m. This newer option has no increase in projected frontal area and capacity has been maintained by dropping the floor.

2) The shape, or profile is critical to the Teardrop's success. As some of you have noted, we have not simply added a "hump", as this would purely add to frontal area and the CD reduction would not be significant enough to outweigh the height increase. We have to consider the entire combination before setting heights: the cab top deflector and front edge of the trailer have to be set at the correct height to maintain a clean line (usually lower by 200mm). The rear "top header" is positioned much lower than normal, which reduces the wake considerably. Further investigation is underway to include "boat tails" to the rear which will improve this further.

3) The belief that a standard trailer has little airflow separation is completely inaccurate. There are several areas of significant seperation including top edge of tractive unit, tractor-trailer gap, trailer leading edge, trailer side leading edges, under chassis, rear. As you all understand, the Teardrop shaping on the roof is a fairly simple common-sense approach to an age old problem. We would also have liked to taper the sides in at the rear but commercial requirements prevent this from being practical.

Interest in the Teardrop trailer is now increasing exponentially and globally. We have interests from major US operators, as well as interest from Europe, Eastern Block and Australia.

We are delighted that it should be such a hot topic for debate but also feel it is a solution that was long over-due.

Richard

[Dieselman]

Originally Posted by DON-BUR

We are delighted that it should be such a hot topic for debate but also feel it is a solution that was long over-due.

Absolutely. I always wonder what trailer manufacturers don't make the underside more streamlined as well.

We need full underfairings, wheel spats and brake cooling ducts..

Go on, you know you want to..

[DON-BUR]

Under-fairings and other streamlining aids are highly debated topics.

We did do a far more complex exercise in conjunction with Piper and expended great resource to develop the most aerodynamic solution.

Regrettably, commercial vehicles are subject to considerable stress - particularly on the rear and sides.

Underskirts are practical and we provide full wrap-round skirts, but even these get damaged.

Tail-fins, skirt extensions (lower than 400mm from ground) and other aids regularly get damaged thus nullifying any fuel benefit attributable to their aerodynamic efficiency.

Covers over the wheels are not practical as wheel nuts are regularly checked and inspectors will not go through the process of removing a panel.

Under-belly smoothing is something we have been testing, with the inclusion of a venturi duct running under-chassis. Contrary to initial beliefs, actual fuel savings were not forthcoming and this method was dropped. "Fill-in" has also been discussed, but this makes maintenance very difficult (servicing usually every 10 weeks)

The most exciting development is that of eliminating the gap between tractor and trailer by using a seperate bogey. This will allow us to maximise the Teardrop profile without undue separation.

[MetroMPG]

Originally Posted by DON-BUR

Interest in the Teardrop trailer is now increasing exponentially and globally. We have interests from major US operators, as well as interest from Europe, Eastern Block and Australia.

We are delighted that it should be such a hot topic for debate but also feel it is a solution that was long over-due.

Richard

This is good news to read - here's hoping you have much success.

Thanks for stopping by to clarify/share the info you did.

Darin

[winkosmosis]

I wonder what the current status is of the teardrop commercial trailers