Measurements Wanted Please !!

[AlfaLofa]

I hope this all makes sense.

I need measurements - and I need opinions please.

In 1999 I fitted a new front to my S1.

I used a convoluted cut line which ensured that only 2 of the original bobbins were unused once the new section had been bonded. (See photo)

I spent an eternity measuring, cutting, grinding and adjusting until I was satisfied with the fit.

I then bonded the new section using a spare S4 bonnet as an added guide.

The final fit was good as can be seen from the old snaps.

I then fitted the original S1 bonnet.

After several years the bonnet decided to split ( due to a pair of exuberant bonnet springs).

I purchased a replacement S1 bonnet from the same supplier who supplied me with the front end.

But the new bonnet has never fitted properly. I've prevaricated in the interim, moved home (some 600 miles) and never addressed the "bonnet" problem.

I think that the biggest problem is that the "circular" slides in which the bonnet rotates and more importantly rests when closed, are awry as shown in the attached composite photo. (Last photo).

The LH slide is just about vertical but the RH slide is at a racy angle.

Could somebody please confirm that both of these slides should have an approximately vertical inner face?

Could somebody also measure the distance between the outer edges of the vertical faces adjacent to the pop-riveted slides on the bonnet. (My bonnet measures about 60.6cm as can be seen in the last photo).

I also measured the distance from the top outside corner of the curved slide (green lines and X) to the back of the bonnet aperture (under the screen) and to the intersection of the wing ridge and the headlamp pod aperture.

These measurements were:
LH - to rear of bonnet aperture 61.2 cm
LH - to wing ridge/pod aperture 44.8 cm
RH - to rear of bonnet aperture 62.0 cm
RH - to wing ridge/pod aperture 45.7 cm

I would have thought that the wing ridge/pod aperture distances should be identical because they come from the same unmolested front end which I bought back in 1999.

The fact that the curved bonnet supports appear to be in different positions on each side of the "new" front end and that one is vertical while the other is not, suggests that I need to remove the RH bonnet support and then reattach so that its measurements match the LH bonnet support.

It seems to suggest that the original front had a serious defect - although I can't explain why the S4 bonnet fitted apparently very well.

So is hacking off the RH support and then rebonding the way you would go?

[AHM]

Yes parallel and vertical.

No don't chop it off unless it is in the wrong place which it doesn't appear to be - Surgery rather than amputation!

It is difficult to see what exactly is wrong - could you post a picture looking at the hinge from the front.

I have an S2 and S3 bonnet which I have tried on the S4 they fit equally well as the S4 bonnet (which is not original to the car) within reason hey are the same. The earlier bonnets seem to be a bit flatter across the front and there is a bit of a step.

It looks like you made a really good job of the difficult bit, so correcting this should be quite straight forward and good fun!

[AHM]

S4 bonnet - 615 mm
S2 bonnet - 620 mm

To inner edge of flange.

Well I'm guessing it is an S2 (maybe S3) bonnet it is old and only cost me a few quid.

Your measurements (green) show that it is in approx the right place - more would be too scientific. Now make them look the same and then adjust with the nylon screws ... just like Lotus did!

Another thought - the support stay may be pushing it out of shape - they are adjustable

[AlfaLofa]

Good point about the support stay - I'll check that.

Currently because the RH hinge/slide is about 1cm closer to the screen, the bonnet gap is far less (i.e. zero) beneath the screen on the RH side when compared to the left.

I'll do a bit more fiddling.

[rodlittle]

Just measured my S1 and the distance between the flanges as in your pic is 610mm
but its not an original bonnet
rod

[AlfaLofa]

AHM - Thanks for reminding me about the slotted bracket.

I was able to straighten the RH hinge slide to just about vertical.

So definite progress

Mind you it is under tremendous tension

The tension on the 2 springs securing the bonnet was also much too high - so I fitted a piece of drilled strip metal to each of the 2 bolts either side of the bonnet.

The metal strips made a difference - but the two springs are still too tight. When closed the bonnet is still pulled up tight against the edge of the bonnet aperture beneath the screen - leaving all the gap at the front.

I'll try longer metal strips tomorrow. I'll also remove the plastic screws at the front of the hinge slides.

I might also investigate attaching a (relatively low tension) spring to the front edge of the bonnet with the other end attached to a bracket in the vicinity of the air filter. Hopefully this will at least encourage the bonnet to stop migrating to the rear of the car when it is closed.

Then I'll have a go at fettling the positions of the bonnet catches.

Rod - it's also good to know that the flange width is within "tolerances". Cheers.

[AHM]

Mind you it is under tremendous tension

Gently heat it with a hot air gun - not so hot that you wreck the paint... but as hot as you dare!

[AlfaLofa]

For the last couple of weeks now I've been fiddling with my replacement bonnet in an attempt to get it to fit the aperture better.

I'm getting there

After exhausting all the adjustments available via the bonnet catches and the plastic screws and washers in the bonnet slides I've now:

a) added an extra layer of fibreglass (plus filler) to the right-hand edge to create equal lateral bonnet gaps
b) added an extra layer of fibreglass (plus filler) to the back edge adjacent to each corner to make the gaps at the corners equal to the gap in the middle of the back of the bonnet
c) Added filler to the top surface at both back corners to get the levels equal to the body
d) Added fibreglass (plus filler) to the vertical front edge to lessen the gap
e) Added filler to the surface at the front edge to get the bonnet level equal to the body
f) Reduced the width of the bonnet catch locations (to about one mm wider than the catches) so that the bonnet locates centrally (without any sideways movement) when the bonnet is closed
And finally:
g) Fitted a 6mm plywood block behind each bonnet catch to move the catches forward and prevent the bonnet popping at speed (it was popping at 60 - now it stays put at 80+)

f) and g) are the best mods.

The last thing to do (besides painting) is to reduce the bulge in the edge of the bonnet along the central part of the left hand side.

What I intend to do is cut a sliver of fibreglass from the bonnet vertical edge, widen the gap as necessary and then close the resultant gap using a few "L" shaped brackets - and then laminate new fibreglass.

Hopefully there will be enough 'give' in the bonnet to make this possible

I've also (currently) abandoned the 2 bonnet springs which locate in the chassis. The springs were far too strong and constantly pulled the bonnet too far towards the rear of the car.

Currently I have a single spring (non Lotus) going from the leading edge of the bonnet (which I have reinforced top/bottom with steel strips) to a bracket fitted centrally adjacent to the air filter.