Heavy Door Hinge Design

[steris]

Hi Everyone,

First off I want to thank everyone for making this forum so great and being so helpful! My company is working on a project and I just noticed something in the specification that I don't know is even possible. The equipment has a large door that weighs 2,500 lbs and the hinge pin will be 30" horizontally from the center of mass - imagine the door to a large safe. The door is opened and closed by hand and the spec calls for a maximum of 5 ft-lbs of torque to move the door. Speed is not a concern since the door would be moving around 1 RPM. A quick calculation assuming a 3" dia bearing yields a required net bearing coefficient of friction around 0.001 - very low considering I will need multiple bearings. My questions are:

1) Are there any commercially available hinges that can support this load with such low friction?
2) Barring anything I can purchase - what are some good tricks to support a high moment load while minimizing the friction (ie. is it helpful or bad practice to put two thrust bearings on top of each other or nest one radial bearing inside another?)
3) What kind of bearing would be best for this application? Would it be best to use beefy tapered roller to support both the axial and radial or a combination of separate thrust and radial bearings?

Please let me know if anything is not clear. Any advise that can be offered would be greatly appreciated! Thanks!

-Steris

 

[dvd]

Even with frictionless bearings, overcoming the inertia of a massive door will require application of torque.

If using housed bearings, especially pillow blocks, it seems like steel housings would be preferrable to cast iron. The tapered roller bearings would be my choice.

If there is a significant change in temperature involved, you may need to anticipate the need for expansion allowance. Also resistance due to cold grease that never warms deserves some consideration.

Counterweighting may be one way to reduce operator effort. Also consider how to stop the door once it is in motion.

 

[MikeHalloran]

You don't need to 'double up' or nest bearings. Just buy decent ones and use them within their load ratings.


Mike Halloran
Pembroke Pines, FL, USA

 

[Oldhydroman]

It might be an imaginitive reading of the specification, but would a small hydraulic cylinder connected to a handpump still count as the door being "opened and closed by hand"? It would safe a lot of effort in trying to design in the ultra low friction bearings (and whatever systems and maintenance regimes were needed to keep the friction ultra low at all times).

You may be able to play the safety card and claim that the hydraulic solution means the door would stop moving as soon as the operator stopped pumping - thus preventing someone getting their fingers crushed should they inadvertently wander into a pinch point. There are many hydraulic fluids available to suit your particular circumstances: mineral oils, biodegradable fluids, fire resistant fluids, food safe fluids etc. And, with a little bit of extra investment, you could even engineer the scheme to use pure water as the fluid.

Just a suggestion.

DOL

 

[racookpe1978]

Seems like the solution is easier if you split the problem into two parts.

First: You need to reduce the resistance of the door as it is pushed shut (starting friction and rotating friction problems. I'd use one roller-type "thrust" bearing under the lower hinge pin so it holds up the door.

Second is the cantilevered hinge force (pulling out of the wall). Use two (three ?) other simpler/cheaper bearings for that around the hinge pins.

 

[MintJulep]

My initial thoughts were similar to Oldhydroman's.

Suitable gear train and apply your five ft-lbs torque to a crank handle.

Otherwise it seems like a "difficult" requirement to meet.

 

[DRWeig]

I know nothing about designing heavy swinging things, but here are some good views of my favorite heavy doors. Note that views when closed from the outside are rare, but the location is no longer classified. It doesn't appear below that Airman 1st Class Warfield is applying only 5 ft-lb torque. The article about him is the attachment at engineering.com below.

A couple other views:

http://upload.wikimedia.org/wikipedia/commons/1/19/NORADBlast-Doors.jpg

http://i2.ytimg.com/vi/iERsZT_glPs/mqdefault.jpg

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

 

[zekeman]

Let's see, 5 ft lb and the operator is 5 feet from the hinge.
One pound of force
Pretty wimpy.
Maybe, you can hire a stronger person for the job, or is this the bank manager?

 

[KENAT]

I'm with Zdas, 5 ft lb isn't much for a door approximately 60" wide (assuming the CofG is near the center of geometry of a regular shaped door)

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[steris]

Hi All,

Thanks for the feedback. This actually isn't a bank vault but the door certainly is heavy enough to be used there! Luckily there isn't a great temperature differential within the hinge so I shouldn't have to worry about thermal expansion. I agree that 5ft-lbs of torque is an absurdly low requirement - that's why I'm not sure that this is even possible. I don't know how this spec slipped through. I like the idea of a hand crank and but my manager doesn't think it would be acceptable. We are going to see what we can do to increase the torque requirement to somewhere around 40-50 ft-lbs.

Regardless, of the spec requirement, thanks for the pointers on the bearing setup. Are there any other suggestions to minimize the torque required? I don't have much experience with hinge design but the combination of a thrust bearing on bottom with radial or taper on top makes sense to me. I was looking at angular contact ball bearings as opposed to tapered roller bearings. My thought is that while the load limits are lower, the bearing has less friction. Does anyone have any experience with these?

In terms of doubling up bearings - again I don't have much experience with bearings - but I was thinking that two thrust bearing on top of each other would serve to cut the net coefficient of friction in half. I don't know if this is true. From MikeHolloran's comment it sounds like something that is just not done.

As an aside, it seems this conversation has become more about bearings than hinge design. Is there a way for me to move this thread into the bearing forum to get their input?

Thanks again!
-Steris

 

[MintJulep]

I was thinking that two thrust bearing on top of each other would serve to cut the net coefficient of friction in half.

And four would cut to a quarter and eight to an eighth and pretty soon we've got perpetual motion.

Go back to your fundamentals.

 

[steris]

Hi MintJulep -

I appreciate your sentiment. My thoughts were along the lines of how springs in series add up. There is a good deal of literature where friction is modeled on the micro-scale as springs. Given that, it seems reasonable to question whether putting frictional bearings in series would achieve the same result. If this isn't the case, so be it...

Best,
Steris

 

[boo1]

to obtain that low vlaues consider rotary air bearings