van/lorry drivers

[sophie_1003]

on vans- what is the round black thing on top of some vans that spins round?
on lorries- what is the purpose of the bit on the top of the cab, usually displaying the lorry company's name?

[chasbo]

On the vans - its a ventilator. The bit on top of the cab is either purely decorative, or is a wind diverter or spoiler to enable the cab to be more aerodynamic

[Postdog]

Dunno about the round thing. Probably some form of ventilation.

The bit on top of the cab is at an angle and reduces drag, and so improves fuel consumption, by directing the air as you drive into it over the top of the lorry or trailer.

[sophie_1003]

but how come only some vans have them? is it just like only some cars have air-con?

[RATTER15]

The round thing is ventilation, its usually put on by the owner or driver as an additional extra. The thing on top of the cab just diverts the wind over the truck bodie instead of the wind hitting it straight on.

[Ethel]

The ventilator is an optional extra. Useful for certain loads, such as pets.

[tali122]

vans carrying meat i assume must legally have this roof vent

[asallen]

No, you're all wrong.
These are only found on clockwork vehicles and this is where the key goes!

[ugly_bob]

I think asallen may actually be correct, but the black bits are an optional extra, though i'm not sure they are for ventalation necessarily. You see them on refridgerated vans which, obviously, do not want outside air getting in and warming up their cold air. It probably, in this case, has something to do with the cooling system.

[sophie_1003]

thankyou all! like the clockwork idea!!

[Disco Fever]

My van has a ventilator on the roof as it used to carry batteries and the inside of the vehicle needs at least 2 air changes every hour so the driver doesn't get overcome with battery fumes.