Hi Maik, no it’s not my first round steel door- it’s the biggest round working door in steel so far, but I’ve made lots of smaller ones in steel over the years. The ones in the group shot are the only ones I’ve got now.
Youre right the One King West door is aluminium, the tiny one is actually steel with brass trim, although I did make one in bronze about 20 years ago as a desk pen stand for my dad.
Years ago I made quite a few 4 inch (100mm) steel display models styled like the Chatwood door in the old Midland Bank London.
From that pattern I also made a few more ornate American style variations with brass bolts and trim. I made one of them really elaborate like a Remington Sherman with the square brass frame over the boltwork- only made one like that though, it took double the time. Also made a few big pen stands in Aluminium and stainless, all around 100mm diameter, some of those were about 75 or 80mm thick- really chunky.
Almost forgot, also made a few small Cleveland Fed doors in solid 316 stainless steel. They were about 45 or 50mm diameter and one much smaller version around 30mm I made into a pendant. There’s more from over the years that were rectangular but that’s probably it on the round ones. Oh, plus a few batches of small key rings or key chains as some call them. Some were brass and some in aluminium all had stainless bolts.
For the eccentrics on the ends of the pressure bars on this new door I’ll machine the cam blocks from solid in stainless, and add shouldered stainless eccentric pins afterwards. The cams will then be pinned onto the bars like you say.
Regards the eccentric pins bending under the the force, on a big working model like yours you ideally want the pins being a tight press fit in perfectly reamed or bored holes in the cams. There’s too much ‘play’ in screw threads to have them threaded, no matter how good the threads are cut, its still down to very small interlocking surfaces coming together which will crush under heavy sideways pressure creating play/wobble- rigidity is paramount under extreme sideways forces like these. You could incorporate heavy rollers as the eccentric pins as that’s a well proven method of relieving wear in ‘camming’ applications like this where there’s big forces involved. The improvement of a ‘rolling’ action where the pin can rotate is superior over the harsh ‘biting’ action of a fixed pin, and is easily achievable using a good set of roller bearings designed to take that sort of axial load.
For fixed eccentric pins you ideally want really accurate holes in the cam blocks either reamed to size or bored out with a single point tool on the lathe.
Make the eccentric pins stepped with a shouldered head and a tight press fit, use a smear of cyano or loctite on assembly as you press them together. It would make sense to use a tough grade of stainless or tool steel for the eccentric pins so you’ve got no worries about surface wear but might be OTT regards the shear strength- more on point later..
Making the pins shouldered so they are stepped into the cam blocks, adds good stability- doesn’t need to be much of a step as you still want the ‘root’ of the pins as thick as possible into the blocks.
Pressure bars are quite an unusual mechanism when you think about them, they have a few hidden points to note the more you go looking. Don’t forget that no matter how big, heavy, precise and strong the cams, bars and eccentrics etc are, if the cams are sleeved over the drive bars and then pinned in place then the whole system is only as strong as the shear strength of the small cross-pins holding them. So, shear strength is very important, but it’s easy to go overboard on say the cams and eccentrics, when the tiny cross-pins are the ones to really think about. Weakest link in the chain so to speak…
I know you’ll get it worked out and sorted Maik, unique projects like your Monster vault always involve a fair amount of experimentation- that’s the challenge and enjoyment of doing them!
Cheers again mate 🙁y):
