If a door is swinging perfectly into into its frame and is balanced on roller bearings as perfectly as all the manufacturers tell us, I would have thought that the gearing and pressure system would be designed and governed by they effective pressure they designed the door to have on it.
In terms of opening and closing, a 25 ton door shouldn’t need that much more force to open or close than a 10 ton door if it’s all working properly. Likewise, the Cleveland Fed being 2 or 3 times the weight of many of the big doors is seen being pulled open and pushed shut by 2 guys- probably possible by 1, just a case of getting that initial dead weight moving and some momentum behind it.
We’ve all seen the makers claims of a door weighing 20 or 30 tons which can be pushed closed by a persons finger- it does figure as roller bearings are amazing, you only have to look at extreme examples like open-cast mining shovels, walking draglines and turbines etc to see the sort of immense loads they can take- loads which make even the Cleveland Fed door seem like a toy.
The door in the video is unusual for a big one in that the pressure bars are behind the crane hinge found more typically on the lighter doors. On most of the big 30-40 ton doors they are more commonly positioned outside the crane like on the Cleveland Fed. If you think about it this drastically alters their positioning in the housing drum or gearbox. On the Cleveland Fed and One King West the pressure bars are close to the front, leaving a lot more room towards the back. This is also common on the big doors with 3 point bar systems. The one in the video is the other way around, pressure bars at the back behind the hinge means all the gearbox space is at the front. No wiser but a bit more food for thought..
