Just finished this for a friend’s son who is 21 on the weekend. Hollowed out a deep sponge I had layered with jam and buttercream. After covering with black fondant I commenced building the engine with a combination of hand modelled fondant parts coloured candy shoestrings and liquorice. The bonnet struts are candy floss sticks covered with fondant, these go down to the bottom of the cake to support the weight of the bonnet, which is simply leant on the top. There is an aluminium “L” shaped brace at the back of the cake (like a bookend) which just peeps above the back of the cake. This stops the bonnet from slipping back and also from pushing the back of the cake out.