Bored,
In my limited experience, things can get boring in a company when they are going too smoothly. For example the company is raking in profits on an existing product line where most of the bugs are already worked out, and the main focus is on slashing costs to squeeze out even more profit...
There is not necessarily any problem with a non-standard center distance. The involute form of spur gear teeth is not sensitive to center distance variation in that it maintains a theoretically conjugate (or kinematically correct) meshing action at any center distance. This is one reason the...
If you are talking about carburized steel gears, then you can, depending on how the gears are processed, get some significant residual compressive stress in the gear teeth. For that reason they probably won't locally yield at the same stress as a typical stress strain test specimen. If you...
GKBuckingham,
I have a well-worn copy of Analytical Mechanics of Gears that has been useful many times over the years.
Small world - interesting to hear that you were involved with those fatigue tests. I would be very interested to see the website you mention when its done. Thanks for...
One way to think of it is that with typical spur gears, at some instants in time you will have 1 pair of teeth making contact and at other instants in time you will have 2 pairs of teeth making contact. There is typically a rather abrupt change from 2 teeth to 1 and vice versa. Imagine you...
In case anyone is interested I finally located a paper having results from this study:
Seabrook and Dudley, "Results of a Fifteen Year Program of Flexural Fatigue Testing of Gear Teeth", 1963.
Its AGMA paper No. 63-WA-199
They broke around 3000 gear teeth of varying materials. Not of any...
Tbuelna,
As I said, I am aware that modern materials and processing improve gears in many ways. And again, I do not intend to use Dudley's data to design anything. But trust me when I say that companies are still using it. If they use old stress "allowables" that underestimate the...
First of all, I never stated I intended to use the data for anything, so please don't anyone jump to that conclusion.
Secondly, give me a little credit. I know gear materials and manufacturing have changed over the years. That's trivial.
My understanding is that the AGMA actually used...
tbuelna,
Using S/N curves developed from small, polished material specimens for gears would be inappropriate unless one actually factored in a variety of things (this should be worked on).
However, many times S/N curves are developed based on tests from actual gears and thus they include all...
I must be mistaken, but it seems that in a few of the posts here people are advocating a sort of cover-up of dangerous products and/or conditions. If you believe there is a danger to human safety, you should just keep quiet about it? Really? Management doesn't even want to know?
I'd say any...
I have heard that sometime after WW2, Darle Dudley conducted a large scale study of gear fatigue that may have been funded by the US government. He supposedly came up with S-N curves.
Does anyone know if the results of that study are still available anywhere? I can find no trace of it on...
Marvincooper:
In conjunction with an idea like the spring-loaded pivoting rack or sliding rack, could you make the first few rack teeth out of hard plastic or rubber? Maybe something like PEEK. I don't know how much torque you will have, but if its low enough that the plastic teeth can...
I don't see any discrimination against older engineers where I work. Quite the contrary in fact. The older engineers control just about everything that happens, and at the same time seem to constantly express concerns like the OP.
Some people seem to get married to certain way of doing things...
Crazy idea - what if the rack itself had some play in its travel before it hit a hard stop. In other words, if the whole length of rack could translate +/- one pitch length freely (or more likely with some small resistance) before it hit a stop. Then if a pinion tooth came crashing against a...
You could have a kind of ramp that the carriage could drive along. The ramp would be parallel to the rack. As the carriage drove along it would start on the decline of the ramp with the pinion positioned above the rack. As it went down the ramp the pinion would be brought down radially into...
