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Post by norvin on Jan 8, 2013 11:06:08 GMT
I am not sure why but for some reason my bonnet will not stay open, I need to prop it up but the other day it came down on me as I worked on the engine and the catch hit me in the back, I was lucky as I had on a heavy coat, the bonnet has been off twice since I have owned the car for a paint spray the first time it went back fine and stayed up ok, but ever since it was taken off for the second respray it has never stayed open and I must admit I just can not see or find anything wrong with it, but something must be. Has anyone had this problem.   |
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Post by enigmas on Jan 19, 2013 2:12:05 GMT
I tend to think 'this' is the problem. The springs are under extension tension when the bonnet is closed. Most of the springs are now 40 or more years old and have lost some tension due to fatigue and age. When the bonnet is open a small amount of tension when the spring is at rest coupled with the correct geometry where the bonnet is held in a neutral balanced position enables it to stay open....anyway, that's my spin on it. My solution. Add a small gas strut to assist the mechanism. Sorry Vince I edited instead of replied must put my glasses on first thing  |
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Post by johnwp5bcoupe on Jan 19, 2013 8:35:56 GMT
Sounds a good theory Vince and I agree with the description of how it should work  To cure the problem the spring needs more tension as a spring ages under tension it stretches I am sure if you measure yours you wont get much of a feeler gauge between the coils it would be good if someone had a new one to measure I have 3 and they are all within 0.5 mm. A simple solution would be to remove say 2-3mm out of the top longest piece before the loop Mig weld it and see how it performs It wouldn't have to be heat treated afterwards! |
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Post by enigmas on Jan 19, 2013 13:10:38 GMT
Hmm, I didn't think of that John, but its a straight forward solution. Welding the shortened cut ends together should work. As far as I can see there should be no requirement for heat treatment as it is just a straight piece of wire under tension. |
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Post by norvin on Jan 19, 2013 16:19:51 GMT
I also thought about a gas strut, but then I thought it would look rather odd, John have you the time to try and modify one of your springs, but then your bonnet is ok, and you do not want to mess up your spare springs.
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Post by johnwp5bcoupe on Jan 19, 2013 16:24:21 GMT
I will do one norvin and see what it come out like |
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Post by johnwp5bcoupe on Jan 19, 2013 19:13:45 GMT
I have been thinking  the solution to this would be to make a sleeve to go over the cut and weld it, if just butt welded the process would make the join brittle if cooled too slowly. The spring at the long end isn't really a spring just a pulling action and is far enough away from the coil not to bother it its worth a try I will have a go tomorrow  |
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Post by enigmas on Jan 20, 2013 1:46:12 GMT
John Ill try the cut and shut with one of my springs.
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Post by johnwp5bcoupe on Jan 20, 2013 6:45:19 GMT
John Ill try the cut and shut with one of my springs. That will be great Vince just 2-3mm it just needs as you know that little bit extra at the point of balance, just try one first you should notice the difference? This is real hands across the water stuff |
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Post by enigmas on Jan 20, 2013 9:31:55 GMT
John I'll do this tomorrow (Monday OZ time). I just took another look at the mechanism in operation and it is almost an 'overcentre' mechanism. When the bonnet is open, the spring is at rest (unstretched). When closing the spring expands and then retracts back a little. If I pull on the spring in the 'bonnet open' position the bonnet raises slightly...indicating lost tension. I'll probably remove 10mm from the top straight portion and make a small sleeve (5/16" steel rod) and plug weld the ends in the sleeve (I'll provide pix). Thumbs up. (Hey...there's no emoticon for this admin!  ) |
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Post by johnwp5bcoupe on Jan 20, 2013 10:06:20 GMT
I will be a bit more reserved Vince and go 3mm I cant think what the effect will be if there is too much tension when the bonnet is closed if it is too short? it may kick up at the back? |
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Post by johnwp5bcoupe on Jan 20, 2013 12:30:39 GMT
I did a 5mm cut Vince allowing for maybe a bit of play I just did a V cut and mig welded and put it in a bucket of cold water I may have been lucky but it seems to hold ok on as far as I could bend it by hand  BUT I would still go for a sleeve I can't try it as my Bonnet is still off the car  Norvin if you PM me your details I will send it I think one will do to try we can go from there  |
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Post by enigmas on Jan 21, 2013 4:00:00 GMT
P5 BONNET SPRING REPAIRI removed 5mm from each bonnet spring (as per John's suggestion...sometimes less is more than enough ;D)and welded the sections together. The job took about 3/4 of an hour. The physical cutting and welding took 5 mins. A sleeve is not required. Prior to this repair I always had a 'bonnet stick' on hand for any lengthy under bonnet repairs...and yes, I have been hit on the head several times when the offending object decided to retaliate for my past mechanical indiscretions. Note: If the bonnet fails to sit down correctly at the windscreen end I believe it is due to lack of spring tension, not too much tension. I used a MIG to weld the pieces together. Here are a few pix of the task.        
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Post by johnwp5bcoupe on Jan 21, 2013 6:47:37 GMT
Well done Vince that's a cure I hope for a few guys a good result and a nice job I must admit I couldn't break my weld but doing it for norvin I was being cautious so no sleeves it is Did it take much pulling to fit them Vince? |
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Post by enigmas on Jan 21, 2013 11:20:23 GMT
Hi John, it doesn't require much effort to refit them, but a helper would be of assistance to hold the bonnet during refitting. I did one spring at a time and also used my 'stick' as extra support. As a matter of fact, I've been using that stick for 20 years. Until this thread, I just couldn't be bothered thinking about the bonnet mechanism or it's operation. It's certainly nice to have it stay in place effectively.
Before removing the springs for 'repair' I noticed that there was minimal tension on them when the bonnet was up and that it was possible to jiggle the spring back and forth on its mounting pins. The 5mm cut and shut added just enough tension to provide the needed support.
Note:
I don't believe a 'sleeve' is necessary, but then my MIG welder gives good penetration. (I only needed to trigger it 3 times on each join)
If I were using an oxy/acetylene torch I'd braze both ends into a small sleeve...this would be just as effective.
Alternatively, move one of the mounting pins 5mm back for the same result.
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Post by johnwp5bcoupe on Jan 21, 2013 11:35:30 GMT
That's a good result Vince for "Hands Across The Sea" |
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Post by enigmas on Jan 21, 2013 11:40:02 GMT
Ah, there's nothing like a transcontinental effort. |
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Post by norvin on Jan 21, 2013 13:36:16 GMT
I am going to cut and weld the springs myself as I do have quite a good welder so hope I am up to it, I wedged a screw driver between the spring loop and the spring post on the bonnet hinge to take up some slack and the bonnet stayed up ok.
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Post by norvin on Jan 22, 2013 20:40:57 GMT
 READY TO WELD.  SPRINGS WELDED BACK TOGETHER AFTER 1/4" CUT OUT.  SPRINGS ON BONNET WHICH NOW STAYS UP WITHOUT PROP.  BONNET SHUTS OK.  A QUICK SPLASH OF HAMMERITE. |
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Post by enigmas on Jan 22, 2013 21:05:11 GMT
Well done. Another successful fix.
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Post by johnwp5bcoupe on Jan 22, 2013 21:08:09 GMT
Good Job well done Brian |
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Post by Phil Nottingham on Jan 22, 2013 21:37:55 GMT
Good work - another one for SEARCH!
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the solution to this would be to make a sleeve to go over the cut and weld it, if just butt welded the process would make the join brittle if cooled too slowly. The spring at the long end isn't really a spring just a pulling action and is far enough away from the coil not to bother it 
)
BUT I would still go for a sleeve 
