Pressure Bar Reduction Gearing

[Doug MacQueen]

The last big door I have worked on and spun closed was a 25" York door not far from the Fed bank. I might be able to get the Fed to let me tear into the pilots wheel but that would be a big job for me. Everything on that door is heavy, including that wheel. It would be much easier for me to pull the wheel and cover on the 25" door. It is the same make and vintage.

[Huw Eastwood]

I was joking Doug. I expect the hand wheel alone weighs a few hundred pounds and I can't imagine the bank being that easy going allowing it to be dismantled just to see how it works!

[Doug MacQueen]

Actually the idea is not so far fetched. Accessing any manufacturing and service info is the problem and in my opinion should be in hand if possible, prior to any investigation. This info unfortunately is not held by the bank. So it remains at a standstill until I can solve that problem.

[wylk]

Another video of a round door closing is at https://www.youtube.com/watch?v=v3hk_r9CJa8 in which the hand wheel executes about 12 revolutions. Assuming the pressure bars turn 90 degrees or so that turns out to be a 48:1 overall ratio.



I wonder if there is a rough correlation between the weight of a door and the ratio of the gearbox. It would make sense that the heaviest doors might need the greatest pressure to seat them. Of course a larger hand wheel gets you part way there. It also fits observations that light doors need fewer revolutions and that the lightest ones just use a lever.

[Huw Eastwood]

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..

[wylk]

As a door ages and the hinges wear, it will sag and tilt a little (or even a lot). This is where a good pressure system becomes essential and a manufacturer whose doors cannot be closed after years go by will get a poor reputation. Even if the hinges can be adjusted for height, tilt might be more difficult, and frequent visits by a service rep will still impact reputation.

Seating a years-old door might involve letting the pressure system "lift" it up into alignment. The force required will depend on friction between the door and frame, taper of the door, weight of the door, and possibly other factors.

Hence my speculation that the heaviest doors might have the highest gearing ratio while lighter doors can get away with a lower ratio.

But I admit this is an "informed guess."

[wylk]

Placing the pressure system under the crane hinge instead of over it seems to be a rather late development. One advantage I can see is that the pressure-bar anchors will not stick out of the frame as far, reducing the problem of tripping over them and bumping into them.

Based on a quick skim of images, it appears to have been done by Herring-Hall-Marvin. By this time I think they were subcontracting Diebold for the actual manufacturing but I didn't find any Diebold examples (I did say it was a quick skim). Here is a nice example in Festus, Missouri:



Notice the doorstop's latch on the door, something we were discussing earlier in another thread.

Here is another round example in Saint Louis:



But HHM wasn't the only adopter of this new arrangement. Here is one of my favorites, 510 Fifth Avenue NYC which is a Mosler from 1954:



I always think the crane hinge shape is "awkward". Note the door stop in the corner.

[Doug MacQueen]

Wylk, if you look back at post #3 of the early Diebolds you will find the idea was not a late one. Also I know of at least one 25" door that has the pressure system under the hinge. You are correct about the need for the system, but it is more to get door open than to shut it. Without the system an ill fitting door can be slammed shut and you won't just pull it open by hand. Of course slamming a door is not acceptable but they learned this very early on.

[Huw Eastwood]

I would have thought that whether the pressure bars were positioned behind or in front of the crane hinge would be determined by the actual diameter of the bars, the bearings and the stanchion blocks supporting them, rather than the risk of the anchors on the frame sticking out and people bumping into them.

On the really big doors with huge diameter bars and massive bearings/stanchions I can't see them fitting behind in the gap between the door face and crane hinge.

It makes sense to me that they're fitted behind the hinge on a lot of the smaller lighter doors, and there obviously are some big door exceptions like the one in the video and the one Doug knows of, but it seems a rarity on the really big doors, and also the same for both round and rectangular.

With regard to ill fitting doors you'll see the evidence on the door surface and the jamb. On massive doors like One King West or the Cleveland Fed, the surface area of the tapered plug closing into the jamb is immense- we've seen the paper clip imprint in the Cleveland Feds jamb, so one things for sure- with the tolerances of fit as tight as they are there'll be scuff and abrasion marks everywhere if the pressure bar system has been continuously overcoming any binding points.

[Huw Eastwood]

When the One King West vault door is open the pressure plug (on the combo viewer) is at the bottom of the vertical slot and the pressure hinge pin (on the hinge side of the door) is at the bottom of the hinge bracket; notice the hinge pin extends below the bracket.

Attachment 13363 Attachment 13364 Attachment 13365

I assume when the door is closed (and compressed) the pressure plug and pressure hinge pin move up and the hinge pin would extend above the bracket.

I am not sure if the pressure system has one or two bars but the pressure plug and pressure hinge pin appear to move in the same direction when compressed/decompressed.

those are good observations. Its down to which way the bars rotate from the gearbox to turn the cams. The hinge end cam in the 3rd pic looks to turn anti-clockwise as seen with the space for 'float' being on top, but there's no way of knowing which way the other cam with the locating notch turns without seeing it, and either way produces the same action. Well spotted