Bonnet metal hoop, when was it introduced?

[nebogipfel]

FWIW, the hoop on my car is steel - it's magnetic.

Thanks Brian, yes it's definitely a steel hoop and should be laminated in when the bonnet is being constructed.

[oldelanman]

The original cruxiform ribs across the centre of the bonnet could not be used on a bonnet with the Stromberg bulge so perhaps the steel hoop was introduced when the bulge was........

May 68 - Bonnet with bulge introduced from unit 7895 (LP12254, 24 May 68). Source Lotus Parts Book

Quote from Tim's (TRW99) post in this thread ....post151541.html#p151541

[nebogipfel]

The original cruxiform ribs across the centre of the bonnet could not be used on a bonnet with the Stromberg bulge so perhaps the steel hoop was introduced when the bulge was........

May 68 - Bonnet with bulge introduced from unit 7895 (LP12254, 24 May 68). Source Lotus Parts Book

Quote from Tim's (TRW99) post in this thread ....post151541.html#p151541

Possibly, but it is my understanding that the hoop of steel was introduced to solve the specific problem of the front edge of the bonnet bonnet sagging over time.

The cross brace would merely have stiffened the skin of the bonnet.

Just for info' I am happy to report that bonnets supplied by Susan Miller have the correct steel hoop installed (complete with spring attachment). I was admiring one yesterday

[oldelanman]

Just found a reference to the bonnet in Brian Buckland's book......He says S1 & S2 bonnets had ribs and 2 springs while S3, S4 & Sprints had the steel hoop and single spring implying that the change coincided with S3 introduction, but he does'nt quote an introduction date or chassis number.

[Pastapesto]

Here is my two pennies worth:

The early type radiator (Marston) sits right over the top of the steering rack which is probably why the original spring fixing points were moulded into the sides of the front of the bonnet with the other ends of the springs attaching to the little holes in the chassis near the engine mounting brackets. All lotus chassis including the galvanised ones have these holes (at least I think they do). Anyway, they stopped using (or ran out of) these bespoke rads around the time of the introduction of the coupe (September 65' ish) - apparently the first 100 coupe's had them. Lotus then introduced the wider/cheaper/off the shelf Triumph sourced one which now got in the way of the early spring fixing points but also being thinner allowed for a larger/stronger and probably with a slight cost saving (one rather than two) new spring to be affixed to the middle of the steering rack.
I think that the early type bonnet with the cross bracing (matting laid over "paper rope") worked fine and as there were two fixing points with the loading being spread over two springs rather than one, there was little or no buckling of the early type bonnets. With all of the load now being spread at one central front point as on the newer style bonnet fixing, there was a need to spread the load more evenly around the bonnet which is what the metal hoop does.

I have seen a few cars that have had replacement bonnets without the metal hoop moulded/bonded in and they all seem to be buckling on both sides about 10 inches or so forward from the screen.

So, in my humble opinion (and it is just my opinion - so please don't shoot me down in flames) I reckon that the metal hoop was introduced around about January/February 1966. As for chassis numbers - I haven't a clue.

[nebogipfel]

Here is my two pennies worth:

The early type radiator (Marston) sits right over the top of the steering rack which is probably why the original spring fixing points were moulded into the sides of the front of the bonnet with the other ends of the springs attaching to the little holes in the chassis near the engine mounting brackets. All lotus chassis including the galvanised ones have these holes (at least I think they do). Anyway, they stopped using (or ran out of) these bespoke rads around the time of the introduction of the coupe (September 65' ish) - apparently the first 100 coupe's had them. Lotus then introduced the wider/cheaper/off the shelf Triumph sourced one which now got in the way of the early spring fixing points but also being thinner allowed for a larger/stronger and probably with a slight cost saving (one rather than two) new spring to be affixed to the middle of the steering rack.
I think that the early type bonnet with the cross bracing (matting laid over "paper rope") worked fine and as there were two fixing points with the loading being spread over two springs rather than one, there was little or no buckling of the early type bonnets. With all of the load now being spread at one central front point as on the newer style bonnet fixing, there was a need to spread the load more evenly around the bonnet which is what the metal hoop does.

I have seen a few cars that have had replacement bonnets without the metal hoop moulded/bonded in and they all seem to be buckling on both sides about 10 inches or so forward from the screen.

So, in my humble opinion (and it is just my opinion - so please don't shoot me down in flames) I reckon that the metal hoop was introduced around about January/February 1966. As for chassis numbers - I haven't a clue.

FWIW I think both you and Roger (oldelanman) are on the right lines in that the change of radiator and spring attachment required a change to the bonnet spring attachment, but it's my understanding that initially for the S3 a flate plate with spring attachment was rivetted to the front face of the bonnet as seen in Gary's pic' of 36/5520 in this thread ......elan-f14/bonnet-spring-hook-t23362.html

This arrangement was found to sometimes result in distorted bonnets so the improved arrangement with the tubular support was introduced as far as I can glean sometime in S4 production. It would be interesting to pin down the chassis number/date.

I mentioned Susan Miller's correct replacements above because I know of at least one major supplier of Elan panels who (apparently) always supplies the older inferior design. In fact they are supplied without the bracket which then has to be retro-fitted by the customer.

I'm conscious of the fact that I'm banging on a bit about this but I'm interested and do feel that this sort of historic information is the sort of thing the forum should try to pin down simply to add to the body of info' that Tim and others are hoping to compile.

[DaveAlmey]

Hi All,

My origional bonnet from 69S4SE 48/8882 had no power bulge but had the steel hoop, when initially sanding off hte paint from it I'm fairly sure it was origional as all the paint changes though the decades matched the rest of the body.

The replacment bonnet from Boss Motors was supplied without the hoop fitted. Just another job in the list of stuff to do

Dave

[types26/36]

Hi All,

My origional bonnet from 69S4SE 48/8882 had no power bulge

A type 48.......Wow! .....I'd like to see that

[types26/36]

I reckon that the metal hoop was introduced around about January/February 1966.

I?m not so sure about that, my Oct 67 S3SE has the crucifix type strengthening the same as my S2. I cant be certain but I have no reason to think it is not original.
My Sprint has the metal hoop as expected.

[Pastapesto]

Ha Ha Brian.

There you go, shot down in flames! .

Does it have the central fixing with the plate/hook & one spring or the two early springs?


All the best

Adam

[types26/36]

There you go, shot down in flames! .
Does it have the central fixing with the plate/hook & one spring or the two early springs?

Adam ...... did not mean to score a direct hit
....but yes, it has a central fix and one spring but it was sold as a kit so who knows what Lotus did that day

[nebogipfel]

I think the cruciform stiffener in early bonnets is a bit of a red herring and not related to the issues of spring attachment.

It looks like the final bonnet design is certainly post S3.

It also doesn't matter if the bonnet is of the flat or Stromberg flavour, at whatever point the change was made, (I would guess some time around '68-9 during S4 production) all bonnets had the hoop stiffener laminated around the edge with the spring attachment welded to it at the front.

I would also venture to suggest that if you intend to replace your bonnet on any post S3 Elan (with central bonnet spring) it makes sense to seek out someone who offers the later and improved design ......unless you really must have your S3 original of course


EDIT

It would be interesting to know if anyone on the forum has an original early S4 with a bonnet which has the flat plate spring attachment riveted to the front of the bonnet?

I'm reasonably confident that by chassis 8900 ish based on my own and another example that the latest design was standard fitment.

[fatboyoz]

John,
'68 S4 45/8152 has original bonnet with bulge and riveted flat plate spring attachment.
Colin.

I think the cruciform stiffener in early bonnets is a bit of a red herring and not related to the issues of spring attachment.

It looks like the final bonnet design is certainly post S3.

It also doesn't matter if the bonnet is of the flat or Stromberg flavour, at whatever point the change was made, (I would guess some time around '68-9 during S4 production) all bonnets had the hoop stiffener laminated around the edge with the spring attachment welded to it at the front.

I would also venture to suggest that if you intend to replace your bonnet on any post S3 Elan (with central bonnet spring) it makes sense to seek out someone who offers the later and improved design ......unless you really must have your S3 original of course


EDIT

It would be interesting to know if anyone on the forum has an original early S4 with a bonnet which has the flat plate spring attachment riveted to the front of the bonnet?

I'm reasonably confident that by chassis 8900 ish based on my own and another example that the latest design was standard fitment.

[nebogipfel]

John,
'68 S4 45/8152 has original bonnet with bulge and riveted flat plate spring attachment.
Colin.

That's interesting Colin, thanks for the info'

So we have an earlier S4 with the early bonnet design as I suspected.

OK Guys and Gals, more examples please

[elansprint71]

Apologies for introducing non-metallic references to your steel tube debate; my car is, of course a type 36R, so I have no further comment to make.

http://en.wikipedia.org/wiki/Lotus_Elan