Spiral Bearing or similar which will raise a gate when open and cause it to close

I have been commissioned to make two separate, very solid oak gates, each about 1 m square for the entrances to our War Memorial Hall. I have designed some wooden hinges, lined with lignum vitae to fit on to exsisting steel vertical pins. The Hall Committee would like the gates to close automatically after being pushed open. The lignum vitae lining is next to the steel, otherwise in time the steel will cause the oak to stain black. I think by now you will know I am a professional woodworker and not a practicing engineer.
I am seeking advice from engineers about the possibility of fitting what I would call a rise and fall - type bearing that will allow the gate to open about 180 degrees and rise when opeing and subsequently fallback into place once the visitor has passed through the gate. I do not particularly want to introduce external 'closing devices'. I want to fix something under the 4 wooden hinges on the horizonal base of the vertical steel pins. Is this possible? Any advice most welcome.
Ian, Northumberland.

Something similar to this?

[ATTACH=CONFIG]1107[/ATTACH]

Thank you 'cake of doom'(???) YES the hinges in your visual are exactly the principle I am seeking to reproduce on a 3" / 75 mm diiameter hinge. Having looked at YouTube on how to cut a spiral in wood, I may have found the way I can make a 'self return' mechanism for the gates...

Glad to hear it! If you can, post a picture of the finished product. I was a Carpenter before I became an engineer so I'm always interested in good woodwork.

The only concern I would have is due to the wear and tear on wooden moving moving parts. If the end user is not (or just forgets) interested in proper maintenance, it wouldn't take long to spoil your work. You could do well to recommend a good dry lube for it. Being "old school" one of my favourites for wood is good ole' fashioned graphite from pencil shavings. It does the job and it's essentially "free" and lasts a good while between applications.

Are you going to mill this from a single piece? I haven't watched any videos on this so it should be good to see it happen in real life.

maybe not a spiral. make up a "tube" cross cut it at 45° and you will have the top and bottom halves of your mechanism. Use a suitable guide pin on the middle. You could also cross cut a washer from nylon round with a hole in the middle to match your guide pin to make a bearing surface