Coupling (mechanical) vs Coupling (the TV Show) - A New Year's Eve Match-up

When searching for "coupling" online users will often see search result for both the UK sitcom "Coupling", which aired during the early 2000s as well as flexible mechanical power transmission couplings. (Users may also see results for pluming pipe couplings, but since there can only be two entities in a 1-on-1 boxing match they have been sidelined for this article.)

The intent of this tongue-in-cheek New Year's Eve article is to simulate a boxing match between two very different products that compete for the same search engine result space (for "coupling").

Spoiler alert: This article has been written by an employee of a leading flexible mechanical coupling manufacturer and has never seen the Coupling sitcom. This article is about to get extremely biases, so, if you are a fan of the show which has apparently drawn comparisons to Friends and Seinfeld in the US market, now would be a good time to stop reading this article. For those looking for more information or trivia from the show, consider visit either the show's Wikipedia or IMDB write up and rehash old memories... but the rest of this article will bring you no pleasure.

Round 1: Relevancy

Coupling the TV show is unfortunately way past its prime and has been retired for a decade. While it may have been well received and popular in its heyday, the television series wrapped up in 2004. With each passing year, it becomes less and less relevant. 

Power transmissions couplings meanwhile are in the midst of their prime. Every day, there are millions of them around the world ensuring smooth operations of applications large and small in just about every industry imaginable. Do I hear Eye of a Tiger playing in the background? This boxer means business.

Round 2: Global Reach

Power transmission couplings can be found not only in nearly every industry imaginable, but also in nearly every corner of the world as well. 

The television show may have been popular for a few years in the United Kingdom, but has nowhere near the global reach of power transmission couplings. When the television show attempted to cross the Atlantic, it was cancelled after only 4 episodes airing. (You can find a bit more trivia on its brief US run here.)

Round 3: Staying Power

Power transmission couplings have generations of staying power. While Coupling the TV show ran from 2000-2004 in the UK (and under one season in the US), power transmission couplings have been around long before the actors in the show were even born.

Ding, ding, ding!!!

Unanimous Winner: Mechanical Power Transmission Couplings!!!! 

After three decisive (and admittedly biased) rounds, mechanical power transmission couplings emerged as the clear winner. While fans of the television show may keep it popping up on search engines for a few more years, we predict (with bias) that overtime the television show will fall well into the second or third page of search engine results, allowing power transmission couplings (preferably Lovejoy) to reign supreme.

On behalf of the entire Lovejoy organization, we hope you have a happy and safe New Year's Eve.

Lovejoy Update: Who knows what's up with British television, but it also appears that there was a now defunct British comedy that ran from 1986-1994 titled Lovejoy! Wikipedia and iMDB both have pages on the show, and apparently it does still pop up in search engines when you search for "Lovejoy". Using the same logic as above, and being 100% biased, we similarly declare Lovejoy (the coupling manufacturer) as the head to head winner over the Lovejoy (the defunct British TV show)... but for two British television comedies to be titled "Lovejoy" and "Coupling"... really?

Maintenance Procedures for Couplings

I recently gave a presentation on couplings and one of my fellow presenters had an interesting story.

A consultant was hired by a refinery operation in South America to study why the MTBF (mean time between failures) was significantly different than their peer group.  Upon investigate this was discovered:

Needless to say the maintenance procedures & operations was given a detailed review….

It is import to understand what the root cause of an issue is and take to time to correct the situation. While we are all pressed for time, would you rather have it done it right the first time or find the time to do it all over again?

Top Reason for a Coupling Failure

Coupling failure issues can be traced down to multiple types of failure modes. However, I have found that a few are the primary culprits for all types of couplings.

The #1 failure mode that causes the majority of the premature failures we see can be attributed to one aspect:

IMPROPER ALIGNMENT (angular, parallel or axial)

Some of the remaining common failure modes are (in no particular order):

• Lack of lubrication (Gear and Grid couplings)
• Improper torquing of fasteners
• Excessive torque
• Environmental
• Excessive vibration induced by mating machinery

While multiple issues can occur that will lead to a premature coupling failure, it is a good idea to start with the alignment of the machinery when determining a root cause. 

Used properly, dial indicators (lower cost & pictured above) and laser alignment tools (premium/higher cost) are both effective tools to consider when aligning a coupling.

Recommended Follow On Reading: For a deep dive into specific failure modes, inclusive of photographs, check out the following four articles below.

 

Coupling Failure Analysis - Jaw Couplings (includes hub & spider photos)

Gear Coupling Tutorial - Part V: Failure Analysis (with photos)

Grid Coupling Failure Analysis (includes photos) 

Coupling Peak Torque Failure at Keyway

Sizing a Coupling – Pay Attention to the Driver!

One of the steps in properly sizing a coupling is to understand the application.  Continuous operation vs stop-start, high inertia loading, excessive vibration, etc…  The severity of the application is used to modify the calculated application torque to truly represent the usage of the system.  A handy reference guide is the Driven Machine Service Factor charts that coupling manufacturers publish.  This will typically give a number between 1.0 and 3.0. 

An item that is often overlooked but should be considered for specialized applications (infrequently, but particularly pertaining to gear and disc couplings) is the driver.  When a Variable Speed Electric Motor or Internal Combustion Engine is used as the driver within a coupled system, the torque variations experienced by the coupling are more severe than with a standard electric motor system. This variation is included in the formula:

Application Torque x [Service Factor (Driven) + Service Factor (Driver)] = Selection Torque

The Driver Service Factor can vary from 0.0 (standard electric motor) to 1.5 (low cylinder count internal combustion engines).

As you can see, in specific specialized applications, the Driver can potential have a greater impact on sizing the coupling than the Driven unit!

Shaft Keyway Damage

During inspection of a shaft prior to installing a replacement coupling, a technician found the shaft keyway had some damage. I was asked if this damage would have any impact on the coupling. (The image above shows the shaft keyway in question).

First, I commended the technician for inspecting the equipment and asking about its condition. Second, we dove into what the impact the damaged shaft keyway could have on the system once a new coupling was installed.

For this application (the coupling hubs having interference fit bores), torque is transmitted between the shaft and coupling hub through two methods: (1) the friction caused by the shaft interference fit and (2) via the surface of the key.  When the surface of the keyway is damaged, the key no longer has proper contact and the shaft & hub connection/joint may not be able to fully transmit to the torque level as designed.

For this application, as the new coupling might not be able to transmit a full torque capacity as rated, a recommendation was made that the shaft should be reworked/replaced to ensure a proper keyway fit.

Is "coupling" a noun or verb?

Great question! In short, yes and yes... but really, "coupling" is a gerund. 

In an earlier post, we determined that... as much as many like using the term "coupler"... "coupling" is the appropriate term for describing the physical product connecting/joining two shafts together... but doesn't "coupling" also sound like a verb? (Perhaps this is the root of why some people opt to using "coupler" to describe a "coupling"?)

So what exactly is a gerund? Per Wikipedia, "a gerund is a non-finite verb form that can function as a noun in Latin and English grammar. The English gerund ends in -ing (as in I enjoy playing basketball); the same verb form also serves as the English present participle (which has an adjectival or adverbial function), and as a pure verbal noun. Thus the -ing form in the English language can function as a noun, verb, adjective or sometimes adverb; in certain sentences the distinction can be arbitrary." There you have it... "coupling" is a verb that functions as a noun.

As couplings play such an instrumental role in the life and health of a mechanical power transmission system, I certainly can blame anyone from trying to give the product a noun only name (thus the "coupler" camp)... but I'm also not so sure being a gerund is such a bad thing. It's fun, unique and something I either never learned or quickly forgot during high school English!

Coupler or coupling? Which one is correct?

So what is it... a "coupling" or "coupler"? This is an age old question that, inside the industrial sector, could quite possibly be as fierce as the "soda vs pop" debate that continues to rage through the United States. While corporate budgets have not afforded us the opportunity to map out the United States or take formal studies... Lovejoy is decidedly a "coupling" company, as are all of the handful of other major coupling competitors that our team has surveyed.

Wikipedia also appears to be on the side of "coupling", which defines a coupling as "a device used to connect two shafts together at their ends for the purpose of transmitting power".

But what does Wikipedia say when you search for coupler... it defines it as "is a word used to describe any of a number of things"... one of which is "a connector between two moving parts to relay the motion, such as a universal joint or oldham coupler". It then goes on to say... "see also: Coupling".

Given universal joints and oldham are absolutely coupling types... what does all this mean exactly? Are they interchangeable?

Merriam-Webster dictionary doesn't seem to think so. Among its definitions, a coupling is "a device that connects two parts or things".... but, search coupler and you will find no reference for anything mechanical power transmission related.

So can Merriam-Webster and Wikipedia be at odds? Not really. Upon closer inspection, the oldham coupler reference on Wikipedia actually points back to the Wikipedia coupling page... and the universal joint reference points to a universal joint page that calls a universal joint a coupling (not coupler).

As such, it is our current opinion that "coupling" is the true and proper term... but that doesn't mean that the "coupler" folks aren't without their merits. We just completed another post on the word "coupling", and it turns out it is a very unusual word type (being that it is verb that also can/does behave as a noun).
 
Do you agree or disagree with our analysis? We are certainly still open to revisit the subject/revise our position... so please let us know in the comment field below.

And, in the meantime... should it be any consolation for "coupler" fans, Lovejoy promises to continue thinking no less of your use of the term, and will still be happy to take care of your every "coupler" need. We just ask for your forgiveness in advance if/when our packing slip, website, and everything else we cite incorrectly calls your favorite Lovejoy "coupler" a "coupling".