Lorry Truck Design/Aerodynamics

[Brother D]

Since being a kid I just never understood why lorries are so lacking in aerodynamics, and why there are no modern designs out there? The last design that I thought was ground-breaking was a layland Daf(?) that had a windscreen that went down to the passenger foot well on one side, since then nothing.

Is it because for the speed they travel at there is no need for aerodynamic considerations?

Why is there so much space under the trailers that is not used? - I wouldn't have though ground clearance is an issue, or do they have to visit sites that are off-road?

(And while I'm on the topic of truck design - why don't buses have exhausts routed vertically at the back rather than pointing towards the pavement)?

[OwenK]

Brother D said:

Since being a kid I just never understood why lorries are so lacking in aerodynamics, and why there are no modern designs out there? The last design that I thought was ground-breaking was a layland Daf(?) that had a windscreen that went down to the passenger foot well on one side, since then nothing.

Is it because for the speed they travel at there is no need for aerodynamic considerations?

Why is there so much space under the trailers that is not used? - I wouldn't have though ground clearance is an issue, or do they have to visit sites that are off-road?

(And while I'm on the topic of truck design - why don't buses have exhausts routed vertically at the back rather than pointing towards the pavement)?

There actually is quite a lot of aero in truck design, it's just constrained - next time you pass one have a look at the front corners, they have little vanes to guide air around the front and onto the sides, these make a notable difference in economy on a long run.
The main constraint is size/length, european trucks are limited in a maximum length meaning that any length you use up for the cab means less length for cargo, ie, moneymaking. This is why you don't see many American style trucks with the "doghouse" fronts.

[davepoth]

OwenK said:

There actually is quite a lot of aero in truck design, it's just constrained - next time you pass one have a look at the front corners, they have little vanes to guide air around the front and onto the sides, these make a notable difference in economy on a long run.
The main constraint is size/length, european trucks are limited in a maximum length meaning that any length you use up for the cab means less length for cargo, ie, moneymaking. This is why you don't see many American style trucks with the "doghouse" fronts.

True enough. If you take 2-3m off the trailer to put a slopey front on the cab you would never make back the lost freight.

[s p a c e m a n]

And you cant utilise the underneath of a trailer because anything other than a flat floor with rear doors at a decent hight restricts the type of work you can do too much.

[Brother D]

OwenK said:

There actually is quite a lot of aero in truck design, it's just constrained - next time you pass one have a look at the front corners, they have little vanes to guide air around the front and onto the sides, these make a notable difference in economy on a long run.
The main constraint is size/length, european trucks are limited in a maximum length meaning that any length you use up for the cab means less length for cargo, ie, moneymaking. This is why you don't see many American style trucks with the "doghouse" fronts.

Ah that rings bells about constraints (thought it was a weight thing - the US trucks look pretty heavy)...

I thought maybe a cab with 'ship's bow' kind of arrangement would provide better aero over the plastic vanes, kind of like a < shape looking down? and with flexible/stretchable flaps to the trailer.

But I guess the savings from aero-additions would take quite a while to recoup vs bog standard truck and trailer.

[Pints]

I've seen M&S, B&Q and Homebase using trucks and trailers which look very aerodynamic.

[philmots]

Our trailers fridge is inches away from the back of the unit, so much so on some steep slopes they touch..

Closer the trailer is the more aerodynamic it is.. That and its got to be under max length IIRC 16.4 Meters