The Impossible Rod Coupling - Does it exist? 5

[DistressedNerd]

Hello,

I am in search of 1/4" to 1/4" diameter Steel Rod Coupling with the following requirements:
1. Low profile (minimal expansion beyond 1/4" cross section of rod)
2. Quick connect/disconnect
3. Structurally sound and near equivalent strength to 1/4" steel rod itself
4. The catch all - practical to incorporate in mass produced product

Please send a hyperlink of a rod coupling that meets the criteria and I'll make custom rap about your username and grant an additional wish.

Thank you,

Edison

 

[MikeHalloran]

Does it have to allow angular or lateral displacement of the two rods, or do you want it to be 'rigid' in some sense?
Are tools allowed, or just bare hands?
How much load does it need to carry; axial? radial? moment? torque?
Can the rods rotate relative to one another?
Any specific end prep of the rods? Threading? Grooving? Upsetting?
Are there time limits on assembly or disassembly?
How many will you be needing each year, and how much are you willing to pay for each?
Carbon steel, corrosion resistant steel, or anticorrosion coating?
Environment?
Expected service life?





Mike Halloran
Pembroke Pines, FL, USA

 

[BUGGAR]

"Any specific end prep of the rods? Threading? Grooving? Upsetting?"
ditto. I have something in mind.

 

[Nescius]

Sleeve with internal splines, shaft ends made with external splines.

I use the term "splines" loosely, as the profile may not need to be anything fancy. A square or hexagon may suffice.

 

[rb1957]

and that'd be as strong as the rod away from the joint ... ?

do you need the coupling to disassemble ? (ie could you weld the rods ?)

what sort of temper are you thinking of ? 125ksi (pretty common, 1/4 hard) 90ksi (annealed, normalised), full hard (220 ksi) ??

another day in paradise, or is paradise one day closer ?

 

[drawoh]

DistressedNerd,

Are you planning to attach this (somehow) to 1/4" shaft?

--
JHG

 

[rb1957]

oops should have read the problem statement better (point 2)
however "minimal expansion" might mean a diameter of 1/2" (or maybe 3/8")

another day in paradise, or is paradise one day closer ?

 

[DistressedNerd]

All,

With 7 replies no and solutions or even answers I am upping the ante - I'll throw a video of a simple Rube Goldberg Machine that spells your username for a solution

Clarification:
1. Low profile (minimal expansion beyond 1/4" cross section of rod) - Ideally less than or equal to 3/8" in diameter

Additional design constraint:
5. Rigid when coupled in all planes of motion

The majority of questions are related to design constraint #4 - anything goes as long as it satisfies constraints 1 - 5:
4. The catch all - practical to incorporate in mass produced product

MikeHalloran - thank you for your interest
Design constraints, details, and specifications halt creativity - open ended parameters help creativity. I need at least a few ideas, answers and hyperlinks before we dig into the details.

Thanks,

Edison

 

[MikeHalloran]

Design constraints, details, and specifications halt creativity - open ended parameters help creativity

I call BS on that assertion. Mapping the solution space, especially in terms of constraints, forces focus on the possible solutions that might actually begin to solve the extant problem.

Dreaming about solutions that obviously don't fit may solve some other problem than the one you want to solve, but that's really a waste of time.

... and money. If you had to pay market rate for the advice you've already received for free, you'd be out several tens of thousands of dollars. Being coy about what you actually need does not drive the discussion in a useful direction.

Star for Greg.




Mike Halloran
Pembroke Pines, FL, USA

 

[dicer]

Easy stuff. A female thread in one shaft and a male thread on the other. If it turns bidirectional and unscrewing is a concern, use the appropriate Loctite.

 

[Nereth1]

Agree with Dicer re: threaded connection, but I would say that neither rod can have female threads as it would significantly reduce their CSA and thus reduce the strength of the joint.

But, a rolled in fine (to reduce radial size requirements) thread to the rods, and a double sided female threaded sleeve made of a harder material would do the job.

A more interesting (Read: cool but ineffective) solution would be a frictional fit between an outer sleeve and the two rods. Imagine a spring steel female tube, with a close sliding fit over the rods, with 3 slots cut in each end to 40% of its length (so basically, a double ended collet), with a fine taper so its diameter is larger in the middle.

A pair of second sleeves (one for each end of the collet) of matching taper could be pushed up it, or even have threads and flats so it can be driven home by a spanner, which would then clamp the collet down. You get as much frictional force as you want because you can increase the length infinitely. As the collet/sleeve is widest in the middle, it has all the cross sectional area it needs to have equal strength to the 1/4" bars (there is more CSA in a 3/8 OD 2/8 ID tube, than there is in a 2/8 rod), and you can make it out of a stronger steel anyway.

 

[Jon286]

Fishing Pole - I win!

Cheers,
Jon

 

[Nescius]

By your own admission, you're being intentionally vague. Therefore, we're all giving responses that are strongly colored by our own experiences. Anyway, I'm a simple engineer with grit under my fingernails, so see the attached for a simple solution.

 

[DistressedNerd]

Dicer & Nereth1:
Threaded connection with locktite violates 2. Quick connect/disconnect

Nereth1:
Double sided female threaded sleeve - I am thinking one end of the sleeve is permanently attached the other is not threaded, but has a hexagonal female opening for the hexagonal. See attached picture.
I can't get a visual on the pair of second sleeves / collet idea.

Jon286:
Distraction force separates fishing poles violates 5. Rigid when coupled in all planes of motion

Clarification on Design Parameter:
2. Hand operated Quick connect/disconnect

The attached picture is a proposal I made in CAD - however drilling a 1/16" hole in the rod compromises its strength and for the pin to hold in place hand operation may be difficult (may need a lot of friction on the pin and require a pin punch tool)

One step closer,

Edison

 

[BUGGAR]

You know this guy is selling all our solutions on "Borrow an Engineer", don't you?

I made $7,000 on e-bay last month selling free solutions. You can too!

 

[Nereth1]

Re: Your interactions with Mike Halloran, You may be right that leaving things very open ended gives you a better brainstorming result, but unfortunately, you're not paying anyone here for their time to brainstorm. This website has some of the most experienced/talented engineers I've ever interacted with, but they don't have the time or inclination to throw ideas out for you for an hour straight in the hopes that one of them randomly suits the project you haven't fully disclosed to them. Ironically, if you were paying the people here for their time, you would probably give them full disclosure ASAP so you wouldn't have to pay for said hours of throwing random ideas out.

With your hex joint and pin, either the pin shears off or you get failure from the bearing stresses when it goes into tension.

With regards to the tapered idea, let me know my cut of whatever you're making and I'll draw it up. How do you know if it's suitable? You don't, and I don't, because I don't know your capital budget for setting up or production quantities, I don't know your per part cost expectations, I don't know how much axial space you have to play with, and I don't know your material or environmental requirements.

 

[chicopee]

The "phishing" pole idea by jon286 is the right path. With the radial stress distributed throughout the whole taper and perhaps a "thru" as an additional measure you have basically all the elements required in the post.

 

[Tmoose]

Hi DistressedNerd.

Posted a day or 2 ago by OP, DistressedNerd.
"Design constraints, details, and specifications halt creativity - open ended parameters help creativity. I need at least a few ideas, answers and hyperlinks before we dig into the details.

Posted by DistressedNerd back in January in his own different thread in response to a few replies by others -
"can you help me find (some paper/fabric holding commercial product on line) so I am not taking shots in the dark making 100 prototypes to figure out design principles."

===============================

OP feels A 1/16 inch pin in double shear is " near equivalent strength to 1/4" steel rod itself ." in tension ?
I think a few design constraints and specifications would speed this thread along nicely.

 

[wannabeSE]

The first thought that comes to mind is couplings for sectional sewer rods. But they are probably too big. The ones that I have seen, the ends of the rods are bent 90°, so the strength may be compromised and you have not mentioned what type of steel is being used.

http://southlandtool.com/shop/sewer-rods/

http://southlandtool.com/wp-content/uploads/2012/08/adapterrods.jpg

 

[IRstuff]

Why not just use the standard QD connector concept for air tools?

TTFN
I can do absolutely anything. I'm an expert!
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