Several kinds of bonnets are in use on different makes of ca

 Bonnet
The bonnet (Figure 1.45) is the panel which covers the engine compartment where this is situated at the front of the vehicle,or the boot compartment of a rear-engined vehicle. Several kinds of bonnets are in use on different makes of cars. The bonnet consists of an outer panel and an inner reinforcement constructed in the H or cruciform pattern,which is spot welded to the outer skin panel at the flanged edges of the panels. The rein- forcement is basically a top-hat section,to give rigidity to the bonnet. In some cases the outer panel is bonded to the inner panel using epoxy resins. This system avoids the dimpling effect on the outer surface of the bonnet skin which occurs in spot welding.
Early models used a jointed type of bonnet which was held in place by bolts through the centre section of the top of the bonnet into the body of the cowl and into the radiator. A pianotype hinge was used where the bonnet hinged both at the centre and at the side.
The most commonly used bonnet on later constructions is known as the mono or one-piece type,and can be opened by a variety of methods. On some types it is hinged at the front so that the rear end swings up when the bonnet is open. Others are designed so that they can be opened from either side,or unlatched from both sides and removed altogether. Most bonnets,however, are of the alligator pattern,which is hinged at the rear so that the front end swings up when opened.

The type of bonnet catch mechanism depends on the type of bonnet used. When a bonnet opens from the rear the catch mechanism is also at the rear. When it opens from either side the combina- tion hinge and catch are provided at each side. The alligator bonnets have their catches at the front,
and in most cases the catches are controlled from inside the car.
Bonnets are quite large,and to make opening easier the hinges are usually counterbalanced by means of tension or torsion springs. Where smaller bonnets are used the hinges are not counterbalanced and the bonnet is held in place by a bonnet stay from the side of the wing to the bonnet. Adjustmentof the bonnet position is sometimes possible bymoving the hinges.