Mechanical bearing design for structural engineers

[glass99]

Are there any good reference books on the topic of bearing design that could be recommended?

We are always designing bearings for our structural engineering and structural glass projects - either sliding bearings for the relief of thermal movements or rotating bearings for doors. Just today we were looking for the allowable bearing strength of oil impregnated bronze for example. Recently we also designed a custom pillow block for a spherical roller bearing with high loads. A good general purpose book on this topic with a few formulas would be good.

 

[CWB1]

From the sound of your mechanism Shigley would be a good place to start.

Could you recommend any good books on structural design? I'd like to get into designing skyscrapers.

 

[glass99]

CWB1 - thanks, I have seen that book around. Good to know its useful.

If you want to know about how to design the occasional I beam, I would be glad to recommend a resource! Sorry if you feel we are overstepping, but my little special structures world is merging more and more with the mechanical world. We have more project value going to machine shops manufactured at 0.001" tolerance than to steel fabricators manufactured at 1/8" tolerance.

 

[dhengr]

Glass99:
Find several good Strength of Materials, and Machine Design textbooks, Theory of Elasticity texts, and the like, and then apply some good experience and engineering judgement. It sounds like you and I are in about the same boat, with unusual design details for which there is no specific code paragraph or calcs. and details examples in a std. ref. book, so we pretty much have to go back to basics, first principles and good sound engineering judgement. Google bearings of a thousand different variations, and study what you find for basic materials info., design info. and ideas., etc. Get to know you suppliers and collect a bunch of their literature, there is a wealth of info. out there. Don’t just talk to their salesmen or the first person who picks up the phone, ask for one of their real/knowledgeable engineers, otherwise you just get a bunch of b.s. and pressure for a sale, without any meaningful engineering info. being imparted. Come armed with a bunch of intelligent questions, having done some of your own homework first, so they know they can’t just blow smoke up your leg. There isn’t anyone who should know their products and materials better than their good engineers, but like all of us, they may be put-off if they have to teach you first semester engineering. There are also some good supply companies like McMaster-Carr and Grainger, and the like, with catalogs full of a million parts which sometimes make the light go on when you desperately need a part or idea. The machine shops you are dealing with, particularly the older machinists have a wealth of info. if you listen carefully, and show you are interested in what they do and have to offer. That’s the fun engineering part, rather than the same glass panels every day, or the same simple beam, just a slightly different size.

 

[glass99]

dhengr: yes we do a lot of non-standard stuff. "Esoteric materials" is the fancy way of saying it.

Theory of elasticity and structural mechanics we have well covered already. The specific thing we are looking for is bearings. We frequently have these high force / low movement bearings. Like we have to carry 43,000lb but it only needs to move 3/4" once per year. But it MUST move, and it needs to be compact. Teflon kinda works but sucks in some ways. Oil impregnated bronze sounds promising but I don't know enough about it. Binding is always complicated to think about. We could maybe do a flexure.

 

[BUGGAR]

An over-simplification for structural engineers only: A bearing is a structural element that is also designed to provide a service life under a given load and at a certain speed. Pick your bearing for load, speed and lifetime wanted.

 

[BUGGAR]

"Like we have to carry 43,000lb but it only needs to move 3/4" once per year." Like those air slides below X-Ray machines. Plug them in to shop air and start shoving (don't forget you have to stop it, too). They have contained units that keep dust down.

 

[glass99]

buggar: yeah those air bearings are cool. Infinite life because air doesn't wear out.

A lot of the "sliding" bearings used in structural engineering don't actually slide. For example, a roughly cut slotted hole with a high bearing force and a bolt which has been torqued down. I am trying to to better.

I watched a bunch of YouTube videos about rebuilding old industrial equipment with sliding surfaces where they hand scraped the surfaces to a tolerance of 2/10,000". I need more of this in my life.

 

[mighoser]

There are many options with polymers. Unfilled PTFE has issues with creep. There are reinforced grades like Flourosint and Solid filled Lubricant or Oil Filled Cast Nylon. Other options are high pressure velocity grades of PPS, PET, PAI, or PEEK. If the stresses are too high (not enough area) then steel roller bearings etc are the only option. Mitsubishi Chemical Advanced Materials has a technical chat feature on the website. They can hook you up with an application engineer/material scientist.

https://www.mcam.com/

 

[glass99]

thanks mighoser. Mitsubishi chemical looks like a good resource. Plastics can do magic things sometimes.

 

[CWB1]

Sorry if you feel we are overstepping, but my little special structures world is merging more and more with the mechanical world.

Don't apologize to me, apologize to the board and past customers. You've admittedly done work that you're neither experienced nor educated in. That's highly unethical and fraudulent. Per my hypothetical I'm actually more qualified to design skyscrapers than you are to do the work you're describing being a certified weldor with years of experience designing large weldments.

 

[Andy-WXMK]

In our lab we have some reference and they're from China LYC and ZWZ, we are WXMK, not fanous like LYC, ZWZ. The question is that you trust China technology or not

Andy - WXMK
Spherical Roller Bearing Expert
Since 1993

 

[Andy-WXMK]

Sorry, I made wrong typing, it shoud be "famous", not "fanous", sorry.

Andy - WXMK
Spherical Roller Bearing Expert
Since 1993