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

 

[MJCronin]

I am getting very suspicious .... Based on the conversation and responses above, are we dealing with an MBA here ?

MJCronin
Sr. Process Engineer

 

[DistressedNerd]

All,

The democracy has spoken - here are additional design details

Product: Collapsing Sand Auger
Environment: Marine
Material: T316 Stainless Steel
Action: Ascending & descending through 32" worth of sand via rotational motion of auger

wannabeSE - sewer pipe connection requires tool and violates #2
2. Hand operated Quick connect/disconnect

IRstuff +Great Post!
Pneumatic Quick Connect was my original idea, however I could not find one that is "rigid" they all seem to freely rotate or spin.

One step closer,

Edison

 

[BUGGAR]

Posted June 3: "Any specific end prep of the rods? Threading? Grooving? Upsetting?"
ditto. I have something in mind.

Per your last post, I'm sure my idea will work. I'm thinking of the sand retainers we used in pile driving back in the 70's - are you sure this is not a reinvention?

 

[DistressedNerd]

BUGGAR - Anything goes keeping in mind #4
4. The catch all - practical to incorporate in mass produced product

Lets here it

Thanks,

Edison

 

[IRstuff]

So, rigidity is the the same a rotation, since rigidity usually refers to a bending stress situation.

So, what's the issue with the coupling rotating? If this is a real problem, then you can simple have defined circular detents for the balls, which would keep the rods from rotating relative to each other, but that presumes that there's sufficient rotational freedom to get the balls to align with the detents.

TTFN
I can do absolutely anything. I'm an expert!
faq731-376 forum1529

 

[DistressedNerd]

IRStuff
In order to screw the sand auger into the ground the coupling must satisfy 5. Rigid when coupled in all planes of motion To include radial planes.

Circular indentations for the balls makes sense - my idea was to fill the void of the air channel (they are all pneumatic couplings) with a hexagonal female/male connections to prevent rotation - it's got to be filled anyway for structural integrity. What's your counter argument?

Thanks,

Edison

 

[IRstuff]

OK, that's a requirement, rotation is typically specified through axes, not planes, or specified relative to 6 DOF vs. 3 DOF.

Hexagonal is probably OK, but since you're applying torque, you might be better off with a square profile

TTFN
I can do absolutely anything. I'm an expert!
faq731-376 forum1529

 

[KENAT]

Replace your pin with an R-clip or similar derivative of safety pin.

Posting guidelines faq731-376

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

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

 

[prex]

DistressedNerd, I don't think you can get all your requirements wrt strength satisfied, that is full strength in axial, bending and torsion, and in both directions.
You should start to release some of them: e.g. full strength in pushing (easy to achieve), but reduced strength (by how much?) in pulling. Or: same strength in torsion in both directions, but, when inverting the direction of torsion, the joint could disengage if pulled at the same time. Or you could ask for a rigid coupling in pushing when turning clockwise, and in pulling only when turning anti clockwise.
What else can you release?
This is the same argument as by others: you need to narrow down more your specifications, if you want a solution. And don't say you don't know, you must fully know the functional requirements of your device, otherwise 'what the hell are you looking for?'

prex
[URL unfurl="true"]http://www.xcalcs.com[/url] : Online engineering calculations
[URL unfurl="true"]http://www.megamag.it[/url] : Magnetic brakes and launchers for fun rides
[URL unfurl="true"]http://www.levitans.com[/url] : Air bearing pads

 

[SnTMan]

Driving a "sand auger" (whatever that is) w/ a 1/4" dia. rod? Well, OK.

All kinds of real drill strings are coupled with threads, one male, one female.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Nereth1]

Please see below a quick section view mockup of the coupling I had been trying to describe earlier. You can see in the middle a double ended collet, and on the left hand side is a sleeve with matching taper to drive up it to close it up. You have a second one of these sleeves on the other side. The rods to be joined go inside.

This can be made as long as you want in theory - in reality it is limited by machining tolerances, particularly as that taper becomes extremely fine.

Link

 

[rb1957]

i suspect that the design is impossible as first posited.

to make a joint as strong at the connecting elements,
(this design constraint kills any idea at the get go; none of the suggestions achieve this),
that is hand installable, mass producible,
that fits within a very tight envelop.

The best solution seems to be your original idea, 'cept i'd do it with three pins (matching the hex. shape suggested). Mind you a hex profile fitting within a 3/8" diameter with a 1/4" bore doesn't provide much thickness in the coulping.

I assume you can't thicken the rod locally, so that if you cut both sides to be mating semi-circles (or mating 1/2s) and pin them together.

unfortunately all these ideas fail to retain the pins in any acceptable manner.

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

 

[SnTMan]

Buy a rifle cleaning kit

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[rb1957]

doubt that meets the strength and stiffness requirements

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

 

[monkeydog]

I can't believe you guys are still playing his game.

 

[ameyerrenke]

http://www.amazon.com/Tools-1869517...mpact quick&qid=1465497600&ref_=sr_1_4&sr=8-4

 

[MadMango]

I like games on a slow day. Something similar to this might work.

"Art without engineering is dreaming; Engineering without art is calculating."

Have you read faq731-376 to make the best use of these Forums?

 

[rb1957]

is the coupling as strong as the typical rod section ?

in tension ? in bending ?

how big is the circlip ?

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

 

[KENAT]

Seriously, the pin part is the easiest aspect of this use an R pin or similar - bit too small for a pit/pip pin.

Hard part may be making the socket in cost effective manner depending on volumes etc.

Any concern of stress corrosion cracking?

Posting guidelines faq731-376

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

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

 

[MikeHalloran]

MadMango, your drawing shows promise, but it has two flaws:
1. The typical E-ring will not meet the diameter requirement.
2. Because the E-ring has three teeth and three gaps, the assembly can be disassembled axially if the E-ring is aligned rotationally with either set of jaws. If each rod had two jaws instead of three, it would sort of work, but probably be a little wobbly.


Perhaps it could be improved by threading the OD of the rod ends instead of grooving them.
One rod threaded a little more than the length of the jaws, and equipped with an upset shoulder at the proximal end of the thread.
The other rod threaded for a little more than twice that distance, allowing withdrawal of:
A sleeve, threaded internally, knurled externally, length roughly equal to the jaw lengths.
Spin the sleeve away from the jaws to allow disengagement.
Spin the sleeve over the jaws and tighten it against the shoulder to secure the joint.

I might further enhance the joint, getting rid of the sharp corners, by giving the jaws roughly the same shape as the finger joint used in woodwork. ... and maybe reduce the number of jaws, perhaps as far as two jaws on one rod and a complementary tongue on the other, again with the finger joint profile. ... given that, the central pin and socket may not be required.




Mike Halloran
Pembroke Pines, FL, USA