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S1 Bonnet springs

PostPosted: Sun Apr 21, 2019 5:02 pm
by Certified Lotus
Ever since I rebuilt my car the bonnet springs have been a thorn in my side. They are way too tight and it takes an act of god to get them off and on both sides of the bonnet. They also shove the bonnet back against the body. I have purchased them from R&D as well as Kelvedon and they are almost identical.

It seems to me that the spring should either be longer or more “springy” so they stretch easier.

I was wondering if I took a torch to the spring and stretched them some more if that would help?

Anyone have a good solution?

Re: S1 Bonnet springs

PostPosted: Sun Apr 21, 2019 9:36 pm
by baileyman
Perhaps you could adjust the mounting locations for less pre-load?

John

Re: S1 Bonnet springs

PostPosted: Sun Apr 21, 2019 9:40 pm
by Certified Lotus
Yes, I did that. Still much too stiff. It is clear to me the spring tension is way too high.

Re: S1 Bonnet springs

PostPosted: Mon Apr 22, 2019 2:10 am
by Elan45
I don't have the same spring as you, but on all my S3's I have effectively reduced the spring tension by winding a "key ring", available at most lock smith or hardware store, onto the front center hook on the bonnet. I've used a 1" diameter ring, so I have to stretch the later, center spring, which fastens to the steering rack about an inch less than stock. If some later owner is bothered by this modification, it is easily undone w/ no permanent marks.

Perhaps you could do some "temporary" fix with a pair of smaller diameter rings or even a short length of small chain. Even more temporary, 'suck-it-and-see" fix could be done w/ a short length of soft wire, formed into a loop and added to the length of the original spring.

Roger

Re: S1 Bonnet springs

PostPosted: Mon Apr 22, 2019 8:45 am
by paddy
I had the same issue. I stretched the springs literally just by stretching them (ie beyond the elastic limit) with one end in the vice and mole grips on the other. I didn't take too much force but you really need to make sure both ends are secure - it wouldn't be pretty if came away. I found the bonnet fit a lot better afterwards. I can measure the new free length if that helps.

Paddy

Re: S1 Bonnet springs

PostPosted: Mon Apr 22, 2019 10:25 am
by Certified Lotus
Elan45 that is exactly what I did. Attached two key rings to both sides. But after a while they start distorting due to the spring pull. I am trying to understand why these reproduction springs don’t fit. They really need to be another 4 inches longer or a weaker spring so it stretches easier.

Paddy, I had wondered if I just try to stretch them far enough they would stay that way. Any idea if I heat them up with a torch it might be easier?

Re: S1 Bonnet springs

PostPosted: Mon Apr 22, 2019 11:25 am
by paddy
Certified Lotus wrote:Paddy, I had wondered if I just try to stretch them far enough they would stay that way. Any idea if I heat them up with a torch it might be easier?


It didn't really take that much force but I have to stress you do have to be careful not to injure yourself if anything gives way. I didn't use any heat. I'm guessing I must have extended the spring to 3 or 4 feet before it started to stretch, but don't take that as gospel - you can feel when you get to the elastic limit, and you can do it progressively. For reference, the ones I had were from SJ Sportscars, just in case there are multiple variants on the market.

Looking at the picture below you can see that the free length hasn't changed that much - the coils are no longer bound, but only just. But it makes a huge difference to the tension when in use.

img_20190422_121538.jpg and


Paddy

Re: S1 Bonnet springs

PostPosted: Mon Apr 22, 2019 10:53 pm
by Certified Lotus
Thanks Paddy. I spoke with a friend of mine who has a PHD in metallurgy and he told me to take a torch to the spring, get it red hot and slowly stretch it to the desired length. Then put in cold water. The spring will need to be electroplated so it doesn’t rust.

Will try this and let you know how (if) it works.

Re: S1 Bonnet springs

PostPosted: Tue Apr 23, 2019 12:51 am
by nomad
Well, I've only fooled with springs from a black smith point of view but annealing and tempering springs is a bit more complicated than heating and quenching IMO. Best of luck.

Kurt

Re: S1 Bonnet springs

PostPosted: Tue Apr 23, 2019 1:12 am
by Certified Lotus
Kurt, I really have no idea which is why I’m on a mission to figure out how to create a spring that is the correct length and tension.

I am amazed that more S1/S2 owners who have replaced their bonnet springs have not brought this issue up before.

Re: S1 Bonnet springs

PostPosted: Tue Apr 23, 2019 10:45 am
by baileyman
It seems also there may be a way of adding something like an angle bracket that would alter the leverage of the attachment point on the bonnet. That would adjust the effective spring rate.

John

Re: S1 Bonnet springs

PostPosted: Tue Apr 23, 2019 11:16 am
by Certified Lotus
Elan45 made the recommendation of adding key rings which I have done in the past. In reality I had to add two (2) key rings to make the length correct and it was still too tight. That is why I’m looking to finally solve this problem.

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Re: S1 Bonnet springs

PostPosted: Wed Apr 24, 2019 11:03 pm
by Certified Lotus
I measured the original bonnet springs on my 65 Elan S2 that have been stretched over the life of the car and then took my "new" reproduction bonnet springs and heated them up with a torch and stretched them to the same length, dunking them in water afterwards.

Fitted them to my 64 Elan S1 and I am happy with the results. The springs are now loose enough that the bonnet isn't pressed against the body when closed and the springs aren't under significant tension. The bonnet does not rise up as high when released as it did before, but that doesn't bother me at all.

I will try this for a couple of weeks and if everything works well, will electroplate them to prevent rusting.

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Re: S1 Bonnet springs

PostPosted: Thu Apr 25, 2019 7:06 pm
by RichardHawkins
Gentlemen,

I had a different problem with my S4 bonnet, the spring was not strong enough. After much messing about, taking measurements and hanging weights to the hook on the bonnet until the bonnet opened, I had a spring made.

I live in rural Lincolnshire and there is a spring manufacturer in Skegness about 40 miles away. Skegness Springs made me a bonnet spring and it works nicely.

I am not suggesting that you all place your business with them, but it might be worth searching your area to see if there is a company near you that can help.

Richard Hawkins