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Herald bonnet opening spring assist?


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2054016135_bonnetsprings.jpg.766d945b621f044cfa47d2366d2247d9.jpg

There were some very slight differences over the years, mainly in the shape of the bonnet tube attachment shown to the right in these, but all nearly the same length otherwise. Someone a few years back made them in stainless, that's the top version in the photo.

If you need any Paddocks have them at £9.95 each:

https://jamespaddock.co.uk/bonnet-counterbalance-spring-2

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From my hand-wavey back of the envelope thoughts on the geometry / physics of the two systems. The Herald’s bonnet is shorter and pivots such that the centre of gravity of the bonnet will be somewhere close to the front of the top panel when it’s open, and that will be positioned just about over the front valance. So the springs will only be providing a relatively small assist to a quite well balanced hinge. The Spitfire on the other hand has a longer bonnet and the hinges protrude beyond the front of the car, so the centre of gravity is much further towards the rear of the car at all times. That’ll mean any springs would need to provide much more force on the inner arches, and fits with Pete’s thoughts / memories about bonnet distortion. 

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I've certainly seen claims that the "club" gas-strut conversion for Spitfires can cause distortion or damage. The Herald and Vitesse had balance springs for, as you say, a relatively well-balanced bonnet (at least, it's an over-centre design that naturally rests open), whereas the Spitfire and GT6 have a heavier bonnet that needs a strut stay to keep it open and don't have balance springs. Perhaps the factory thought Heralds would be driven by "the wife" who had weak arms, whereas Spitfires would be owned by macho men who would be insulted at the implication that they might struggle with lifting the bonnet one-handed. They weren't very PC back then 😉

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The E-type Jag has a massive bonnet that uses counterbalance springs on the supporting arms, although they're stockier than the Triumph versions. Given the similarities to the Spitfire and Gt6 you'd think Triumph would have opted for something similar rather than just a metal prop to keep the bonnet open.

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Fascinating; every day is a school day on here. Helpful and informative.

Following on, is there a correct or preferred side from which to single-handed lift a Spitfire bonnet?

I lift mine from the near side. It will not lift from the off side as it distorts and fouls on something. Is this common?

 

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I lift from the nearside as that's where the bonnet support is on mine. Going to fit the gas lifts (sorry Kevin - he doesn't like them) when/if I ever get the steel bonnet fitted. Now there's a thought (see thread https://forum.tssc.org.uk/topic/9330-highest-asking-price-for-a-1360-convertible/page/3/#comment-138217), is my Spitfire worth more with it's fibreglass bonnet?

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I always lift the bonnet of my Spitfire from the nearside as that is the side of support strut which must be engaged once the bonnet is open.  However, if I lift just the nearside, the bonnet twists slightly causing the rubber cone on the offside to become stuck in its locating hole.  To stop this I first release both catches then slightly lift the offside and insert a piece of wood about 1" thick under the lower edge.  This keeps the  cone free of its locating hole so that when I return to the nearside and lift, there is nothing to hinder the bonnet's elevation.

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