[Aditya]

The hyper-cool Front-hinged bonnets

Most cars have their engine bays in the front of the cabin. To access the engine, one has to lift a bonnet, which is generally hinged just below the front windshield. In some cars, however, you will find bonnets which are hinged at the front end of the engine bay – near the radiator.

When I saw a car with a front-hinged bonnet for the first time (sometime in the early 1980s), I found it really cool. I do not remember the car, but the idea of the bonnet opening in the “reverse” direction stuck in my head. I clearly remember old BMWs and Jaguars having bonnets that were front-hinged.


Image Source

Among the cars manufactured in India, the Premier 118NE, Standard Herald and Standard 2000 are some names that come to mind.





Now, BMW and Jaguar have now almost completely shifted to conventional bonnets and nothing manufactured in India comes with a front-hinged bonnet either. Today, across the world, only a handful of cars (mainly high performance machines) come with such bonnets.

Here are the reasons why front-hinged bonnets gained popularity.

Better engine access and lighting:

One of the reasons why they gained popularity was that they provided better access to the engine. Most conventional bonnets open at an angle of ~45 degrees. This limits the headroom available while working on the engine. Front-hinged bonnets, on the other hand, can open at almost 90 degrees. Lighting too is improved with the bonnet almost completely out of the way.


Image Source

Safety:

In older cars, bonnet latches could fail. If one failed on a car with a conventional bonnet while travelling, the bonnet would open in such a manner that the view from the windshield would be obstructed. Worse still, the windshield could crack on impact. In the case of high-performance cars travelling at higher speeds, this is likely to prove even more dangerous compared to regular cars.

https://www.youtube.com/watch?v=JA9piRHcQUE

In the case of a front-hinged bonnet, the bonnet opens in the same direction that the car travels and the above-mentioned situation could be avoided.

Now, let’s have a look at the reasons why front-hinged bonnets fell out of favour.

Modern and safer construction of conventional bonnets:

Modern cars have started getting conventional bonnets with advanced construction and much better latches. Due to this, nowadays, it is extremely rare that a latch fails and a bonnet flies open. Conventional bonnets are a lot safer than they used to be.


If you have a look at some modern cars, their conventional bonnets open at a much greater angle than before. This allows easier access to the engine from not only the front of the car, but also the sides as there is much greater headroom available.


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In the case of a front-hinged bonnet, you get just the sides of the engine bay to work, which is less convenient.

High cost of repairs:

In traditional front-hinged bonnets, the headlight mounts, front fenders and radiator grille are integrated into the bonnet design. In case there is an accident, damage to any one of these parts would mean all the parts would need replacement. This in turn means additional costs while doing any repair work.


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Today, there are some front-hinged bonnets without any other parts integrated into them, but they do not open completely and restrict access to the engine bay. These are still helpful in performance cars, in which the engine is pushed right against the firewall to achieve better weight distribution. Anyway, they still look hyper-cool!


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[Rehaan]

Originally Posted by Aditya

If you have a look at some modern cars, their conventional bonnets open at a much greater angle than before. This allows easier access to the engine from not only the front of the car, but also the sides as there is much greater headroom available.

Some cars, especially the Mercs and a few BMWs have what is called the hood "service position".

This enables the hood to open even further, often beyond a vertical position.

On certain cars you can do this just by letting the hood open fully on the gas struts, and then pushing it up further. And on others you have to remove a bolt to free up the ability for the additional hinging.


image source

This video shows the bolt version:

https://www.youtube.com/watch?v=FGa27Af1e6I

[TrackDay]

Guess everything has it's pros and cons. Guessing here that radiator related works can be a pain, though I could be wrong. Also in this age and day, hood open sensors can give a warning before things get too late.

Although, I have to say that a car with reverse opening hood will definitely gain some attention at a car meet. But no one is going to see the engine properly if the hood is in the front But I think the reverse opening is kind of cool

Image source: https://www.vintage-mustang.com/thre...g-hood.625015/

[Jeroen]

Great thread!!!

I have two of these hyper cool front hinged bonnets!



In all, it is really handy when working on the engine and or components in the engine bay. The only drawback is if you want to take the engine out, which also means you will have to take the bonnet off.

Originally Posted by Rehaan

Some cars, especially the Mercs and a few BMWs have what is called the hood "service position".

Yep, Mercedes has had this on many models for a long time. My 1982 has such a “service position”. For just regular jobs, like checking oil it opens normally as seen on the photograph above.

But it can open to be fully vertical:





I have to admit, the mechanism to lock it in place in this position is broken on mine. Not easy to repair, so I used this clamp to lock the hood in its service position.



You do need to be a bit careful with this service position if you use it outside. If the hood catches the wind, you might have a problem. Also, when you have a car on a lift and you raise the lift with the hood in the service position make sure you don’t ram it into the ceiling!

Guessing here that radiator related works can be a pain

Depends, the hood on my Spider, front hinged, can also open up to be completely vertical! I can get the radiator out of my Jaguar with no problem too.

Jeroen

[srini1785]

Apart from looking cool, front hinged bonnets do not have anything working in their favour. In fact, on rear hinged ones, you have access to engine bay from three sides, Front (grille) side and two sides. While for front hinged ones, you have only two side access. This apart from obvious crash and safety related issues may have caused its demise.

PS : I am a tad in favour of rat rods. No bonnets needed.

[vigsom]

Originally Posted by Aditya

Among the cars manufactured in India, the Premier 118NE, Standard Herald and Standard 2000 are some names that come to mind

The Standard Gazel also sported the front hinged bonnet (image courtesy Bhpian @Stanher)



I also saw this side opening hood on rare car network

[tharian]

A bit of a deviation from the actual thread theme, but for me, the coolest bonnet would be from the big American trucks giving access to almost every part under the hood and displaying their huge diesels.

(Pic credit to original owner)

[CarNerd]

Can the hinged bonnets be replaced by something like a rolling shutter? You press a button and the bonnet automatically rolls inside and outside along side guides. Not sure about Practicality and Safety though.

[Fastdriver]

Originally Posted by CarNerd

Can the hinged bonnets be replaced by something like a rolling shutter? You press a button and the bonnet automatically rolls inside and outside along side guides. Not sure about Practicality and Safety though.

Not practicable. Same from the safety point of view.

[akash_v12]

Let’s not forget how good these 2 look with their bonnets open.

Dodge Viper



Datsun 240Z

[SnS_12]

Anyone for gullwing engine covers to match your gullwing doors?

[SS-Traveller]

Originally Posted by Aditya

Now, let’s have a look at the reasons why front-hinged bonnets fell out of favour.

The first and foremost reason we don't have front-hinged bonnets in most cars today, is safety.

The cars that come with front hinged bonnets today are fast and expensive, and they need to be safe AND light. So the bonnet lid is a kevlar & carbon reinforced fibreglass panel, which will not catch the wind and lift off into the windscreen at 250 kmph because it is hinged at the front end. Yet, in a frontal crash, it will crumble, and will not slice through the bodywork of the cabin.

So what's wrong with my 150-kmph sedan having a similar front-hinged bonnet? For one, that panel in fibreglass with kevlar and carbon reinforcement is going to cost me half the price of the car again - and my insurance premium probably will not cover it after a minor crash. So, to save costs, the bonnet is made of sheet steel, which is a lot cheaper to make and replace.

So why not a front-hinged steel bonnet? In a head-on crash, the hinges holding the bonnet will be the first metal structural components to fail - and a sheet of reasonably heavy steel unsecured at any end is going to come at me like a horizontal guillotine. No, I do not want to be in the driver's (or front passenger's) seat when that happens.

Another advantage of rear hinged bonnets - the panel is designed to curl up in a crash. That helps in 2 ways:
1. The sheet metal forms part of the crumple zone that absorbs a lot of the impact, preventing it from being transmitted to the cabin; and
2. the panel helps to form a shield and protect the front seat occupants from flying debris that can penetrate the windshield. Take a look at a couple of examples from the Accidents in India thread, to observe how the bonnet panel shields the front occupants at least partially.

[landcruiser123]

The member holding the bonnet hinges should be resistant to torsion. If the bonnet hinges are at the extreme front of vehicle, it brings additional manufacturing costs and weight. No surprise front opening bonnets are rare considering the focus on extreme cost cutting and weight saving in today's vehicles.

The structural members near the A-pillar are naturally stronger to protect the passenger component in a crash.

With frunks, they are all going to rear opening.

[Jeroen]

Originally Posted by SS-Traveller

The first and foremost reason we don't have front-hinged bonnets in most cars today, is safety.

In a head-on crash, the hinges holding the bonnet will be the first metal structural components to fail - and a sheet of reasonably heavy steel unsecured at any end is going to come at me like a horizontal guillotine.

On all modern front hinged bonnets, the bonnets are secured very well when the bonnet is closed: My Jaguar has one of these on each side of the bonnet.



This pin latches into a countersunk cilinder that grabs it. The cilinder turns 90 degrees to lock/release the bonnet. Both the pin and the cilinder has a squared section in it. Hidden here by the spring. It is designed to hold the bonnet in place during a head on crash.

Personally I think the main safety aspect is pedestrian safety. These days cars need to comply with many safety aspects in case of hitting pedestrians. Front hinged bonnets are more challenging (and thus more costly, complex and restrictive) than rear hinged ones.

On older cars, e.g. my Spider, the front hinged bonnets is kept in place by a locking mechanism, but these can be quite flimsy. Also, usually just one, in the middle of the bonnet.

Jeroen

[Scarlet_Rider]

Since the Premier 118 NE was our main car for many years (1994 to 2020), I have always been a fan of front-hinged bonnets. I have been using the picture for my Team-BHP avatar since day one!