alternative bonnet hinge
Discussion
I know this has been talked about in the past, but, I am toying with a hinge that operates like a trellis, i.e. it has 4 hinged points. Two are attached to the bonnet and two to the chassis, so when the bonnet is opened it is also raised, giving better clearance and opens further giving better access to the radiator area. What does anyone think to this idea? or has anyone tried this before?
I'd like to be able to do this too 'cos mine is very low at the front and basically sits on the splitter every time I open the bonnet. I haven't thought of a good way of doing it yet, though. I think the most practical approach would be to move the pivot point forwards a few inches. It might be possible to come up some sort of 4-link setup to move the effective pivot point instead, but the way I see it that'd give you very poor location sideways and with both hinges free to work separately the bonnet would try to twist sideways every time it was opened.
Though I am not an engineer, surely the best way would be to retain the existing hinge point and arrangement on both sides of the chassis, but to change the fixing point of the hinge on the bonnet.
If the brackets that presently bolt through the two plywood wheel arch panels were removed and replaced with new longer curved brackets on either side with the fixings further back along the plywood bonnet supports, then because the brackets were curved upwards, the bonnet would move upwards and forwards when opened. Cantilever approach.
It would work ok, it just needs someone who is an engineer to measure it up,draw and prefabricate two curved brackets. They would be a really useful replacement and make so many jobs easier and cleaner.
Does anyboby follow what I am talking about?
If the brackets that presently bolt through the two plywood wheel arch panels were removed and replaced with new longer curved brackets on either side with the fixings further back along the plywood bonnet supports, then because the brackets were curved upwards, the bonnet would move upwards and forwards when opened. Cantilever approach.
It would work ok, it just needs someone who is an engineer to measure it up,draw and prefabricate two curved brackets. They would be a really useful replacement and make so many jobs easier and cleaner.
Does anyboby follow what I am talking about?
GreenV8S said:
I'd like to be able to do this too 'cos mine is very low at the front and basically sits on the splitter every time I open the bonnet. I haven't thought of a good way of doing it yet, though. I think the most practical approach would be to move the pivot point forwards a few inches. It might be possible to come up some sort of 4-link setup to move the effective pivot point instead, but the way I see it that'd give you very poor location sideways and with both hinges free to work separately the bonnet would try to twist sideways every time it was opened.
Problem as Greenv8 says ,keeping both sides true when opening would be hard
clarenceboddiger said:
Thought about it but cant work it out,I thought of getting hinges off something like a BMW 2002, I think they lift then open forwards??
i'd be interested if you think of anything.
i'd be interested if you think of anything.
SAAB 99/900 and BMW 02s all pop up and slide forward and then hinge forward again. Might be worth having a look at how they do it .
Don't agree Peter. The pivot point can remain the same, its the travel arc that needs to change. Don't think the stress on the new design is significantly different to that on the existing hinge arrangement...which is pretty flimsy. The curves could be much more businesslike in manufacture.
Just crudely cutting out two identical shapes of paper, one with the old arrangement,one with a curve below, but both sharing the same pivot point, shows the significant difference in the bonnets arc of travel.
Just crudely cutting out two identical shapes of paper, one with the old arrangement,one with a curve below, but both sharing the same pivot point, shows the significant difference in the bonnets arc of travel.
Just one point - it doesn't matter in that arrangement if the arm is curved or straight - since the distance between the pivot point and the bonnet fixing point doesn't change as you open the bonnet, you might as well make the arm straight and save the engineering cost!
(Chances are it would have to curve the OTHER way to clear the suspension wishbone, anyway)
Remember also that the further back you move the bonnet fixing point (to give clearance when it opens) the less sideways stability it has when closed - you have a lot of bonnet in front of that arm, totally unsupported...
(Chances are it would have to curve the OTHER way to clear the suspension wishbone, anyway)
Remember also that the further back you move the bonnet fixing point (to give clearance when it opens) the less sideways stability it has when closed - you have a lot of bonnet in front of that arm, totally unsupported...
Fair point TVR, straight is the same result.
Difficult to show things to scale in a sketch to illustrate only the idea, but thought the joint with the bonnet plywood support need be only a short way back to achieve the desired lift.
No infringement on steering,tyres or suspension travel,and still close to bonnets leading edge. Just offering a rising as well as forward arc.
Might be a bit trickier setting it up to release correctly on the two spring spiggots was my worry. That, and a way of supporting it when its at 75 degrees or so on a windy day!
Difficult to show things to scale in a sketch to illustrate only the idea, but thought the joint with the bonnet plywood support need be only a short way back to achieve the desired lift.
No infringement on steering,tyres or suspension travel,and still close to bonnets leading edge. Just offering a rising as well as forward arc.
Might be a bit trickier setting it up to release correctly on the two spring spiggots was my worry. That, and a way of supporting it when its at 75 degrees or so on a windy day!
F908 Tim said:
Fair point TVR, straight is the same result.
Difficult to show things to scale in a sketch to illustrate only the idea, but thought the joint with the bonnet plywood support need be only a short way back to achieve the desired lift.
No infringement on steering,tyres or suspension travel,and still close to bonnets leading edge. Just offering a rising as well as forward arc.
Might be a bit trickier setting it up to release correctly on the two spring spiggots was my worry. That, and a way of supporting it when its at 75 degrees or so on a windy day!
Difficult to show things to scale in a sketch to illustrate only the idea, but thought the joint with the bonnet plywood support need be only a short way back to achieve the desired lift.
No infringement on steering,tyres or suspension travel,and still close to bonnets leading edge. Just offering a rising as well as forward arc.
Might be a bit trickier setting it up to release correctly on the two spring spiggots was my worry. That, and a way of supporting it when its at 75 degrees or so on a windy day!
Still don't get it:
If we assume that the hinge point on the chassis is a fixed point ok?
The existing arrangement has a short lever pointing forwards - so as the back of the bonnet goes up, the front goes down, following an arc around that fixed centre.
If we put on a longer lever, even if it points backwards, it still pivots around the same point - it MUST therefore follow the same arc. How can it not, if it is rotating around the same pivot point?
If you want it to follow a different arc (ie the front of the bonnet goes down less, as the rear rises) then you need to move the pivot point UPWARDS and refix by moving the fixing point of the arm on the bonnet by a commensurate amount, so that the bonnet sits right when closed.
OR you need a system of twin arms on two separate chassis pivots so that the bonnet pivot point effectively moves as it rises.
The length and shape of the arm is immaterial.
A slightly different tack then:-
how about a disc centred on the original pivot point,
the disc able to rotate (limited by stops around the said point.
a second pivot point on the disc could move from Point A to Point B,this would allow the pivot point to rise by approx twice the its radius from the original point.
The bonnet would have to be rotated around the pivot point (original) before being lifted.
when closed (A)the std catches would stop movement as it is being pushed back and up, and when at (B)its weight would cause it to fall forward if rotated enough.Maybe use of a few small ballraces would stiffen it up a bit.
Arms should clear centre point if it was not too proud of disc face,and adjustment could be kept as original.It would need a good fitting stay though as it would be high when up.
I reckon we are talking of a 1-2" offset here so it would only be a small component relatively speaking.
how about a disc centred on the original pivot point,
the disc able to rotate (limited by stops around the said point.
a second pivot point on the disc could move from Point A to Point B,this would allow the pivot point to rise by approx twice the its radius from the original point.
The bonnet would have to be rotated around the pivot point (original) before being lifted.
when closed (A)the std catches would stop movement as it is being pushed back and up, and when at (B)its weight would cause it to fall forward if rotated enough.Maybe use of a few small ballraces would stiffen it up a bit.
Arms should clear centre point if it was not too proud of disc face,and adjustment could be kept as original.It would need a good fitting stay though as it would be high when up.
I reckon we are talking of a 1-2" offset here so it would only be a small component relatively speaking.
Edited by clarenceboddiger on Thursday 28th September 18:45
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