CottonGearBallUniversalJoint.

[Anonymous]

Hello,

This thing is driving me nuts... Can anyone explain to me how to make the proper mates?

http://feedback.autodesk.com/cloudservices/topics/cottongearballuniversaljoint_who_can_solve_my_puzz...

Thanks,

Seth Cotton

[Anonymous]

I'll whip something together for you tonight and have it to ya by the morning?

I usually just make the parts and then define them in the drawing... I remember all the tollerances in my head. I agree this kind of conseptual engineering can be sloppy, but its verry productive. You will recieve a well defined assembly.

[Anonymous]

I am going to use .050 total clearnance between the Gear ball and socket, so .025 between faces. I will make the tracks 0.50125 and 0.5 on the ball-bearing as these tolerances should be tighter. I will also put the rear ball-bearing in.

[JDMather]

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@Anonymous wrote:

I am not sure that 8 Ball bearing is the way to go for instance, ....

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I think you will need more than 8.

If you just have one in each slot - their position at any point in time is indeterminant.

[Anonymous]

It wont work like that... That paths cross each other at a 90degree angle leaving 8 diamond shaped windows (In this design) for the the 8 ball bearings to fit into, thus only one ball can fit in each subsequent set of tracks. The ball bearings need the rest of the inner and outer tracks to move into at different angles.

There has been much confusion as to how this works already, this is nothing like an Rzeppa and functions more like a gear than other universal joints. Power is applied from one face of a socket track to a ball bearing, this force is then transferred from the ball bearing to the 90 degree opposed track face on the ball gear. As the shaft is rotated off center, more energy is transferred into roll on the ball bearing and subsequently transferred into the gear ball at different angles. I hope this will make use of some of the lost energy an Rzeppa suffers in friction, but it could be worse... Who knows, probably has some application though.

To assemble, the ball gear with rear bearing should be placed into the socket. The output shaft for the gear ball should be rotated to its full extent, 45 degrees off axis. With the cup and gear ball at 45 degrees, line up the out most point on the ball gear track on the opened side of the joint, with the end of any subsequent socket track end. At this point the first ball bearing can be inserted. Keeping the output shaft at a 45 angle from the input shaft, rotate the shafts until another ball bearing can be inserted into the next track. Repeat this process until all 8 ball bearings have been installed.

At this point the Gear Ball output shaft can be re-alined with the socked input axis, and the ball bearings will move to their respective positions. The Socket Cap can now be installed, the socket cap contains the last bit 22.5 degrees of track, and allows the ball bearings to be inserted into the socket races. The Socket Cap prevents the ball bearings from escaping their races.

This is the only way to assemble this device as it is otherwise impossible to get all the balls into their respective positions as the diamond shaped chambers are behind the drive socket teeth edge one tooth over from their race end. I am almost done with your updated model, you should be ably to see for yourself in the assembly.

Have that to you first thing in the morning boss.

[Anonymous]

https://documents.cloud.autodesk.com/Public/Details?hash=c9tXZTZ

https://documents.cloud.autodesk.com/Public/Details?hash=c9tRVOy

https://documents.cloud.autodesk.com/Public/Details?hash=c9tlEgZ

https://documents.cloud.autodesk.com/Public/Details?hash=c9thCHZ

Here are some renders to better express the cross track.

Im fixing the cap for clearance to the output shaft.

The shaft grooves are intended for an adjustable colar.

[Anonymous]

https://documents.cloud.autodesk.com/Public/Details?hash=c9ZSJAN

https://documents.cloud.autodesk.com/Public/Details?hash=c9ZStKX

https://documents.cloud.autodesk.com/Public/Details?hash=c9ZJTJM

https://documents.cloud.autodesk.com/Public/Details?hash=c9ZJdp2

https://documents.cloud.autodesk.com/Public/Details?hash=c9ZJ3Q5

https://documents.cloud.autodesk.com/Public/Details?hash=c9ZJ2l0

https://documents.cloud.autodesk.com/Public/Details?hash=c9ZwPvu

https://documents.cloud.autodesk.com/Public/Details?hash=c9ZwJZ7

Here you go, I left the threads for you. Also, the dust cap is not nessicary but its in there.

The ball bearing are not in the correct position for previously mentioned reasons. Take some video?

[JDMather]

It would have been far easier for everyone if you had simply zipped a folder with the files and attached it here rather than link to another website.

I opened one part file - PlasticCupSeal and found that it was unconstrained and not modeled at what I would consider a logical location relative to the origin.

This is troublesome as it appears you are working too hard.  Inventor will add most of the missing constraints automatically.

This works the same in SolidWorks (which you claim to have prior experience with).

You might want to read this document http://home.pct.edu/~jmather/skillsusa%20university.pdf

Now to check the rest of the model.....

[JDMather]

oh, this is troubling.

Repeated dimensions (why) and undconstrained sketch?

[JDMather]

This dimension isn't even needed - the circle should be coincident with the projected point on the path.
Wayyy too much work.

I would get lazy and start letting the software do the work.

[JDMather]

Why are you using Extrusions rather than Hole features.
In SolidWorks I would use Hole features - same in Inventor.

By the .25 I'm assuming that you really want a 1/4-20 fastener - but you should be using the Hole feature or at least look up the tap drill size in your Machinerys' Handbook.

I would probably use Metric in this century.

[Anonymous]

Thats the way I use the program. No offence, but it seems to be working just fine for me.

So um, where is the new universal joint you designed?

Sorry, but so far all you have done is bitch and try and discredit me. 

Will all your 15 years of vast experiance what have you actually created?

[JDMather]

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@Anonymous wrote:

Thats the way I use the program. No offence, but it seems to be working just fine for me.

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The point is - it's not working for you.  The holes have been the wrong size - twice.
Have you ever worked out on the shop floor on a mill and lathe?
This is pretty basic stuff.

I had to make quite a few changes - but it is off to the RP machine.
Should be ready in about 4 hrs if there aren't any jobs ahead of mine on the machine.

Well, there are two jobs ahead of mine - should have it in hand sometime tomorrow - will post some pics.

[Anonymous]

Thanks for helping,

I do not have any "formal" training but I was a packaging engineer for two years designing crates for every kind of god awful mechanism you can think of, MRI machines, robots ect... Packaging is actually a much larger challenge than I originally perceived. Usually my days consisted of five or more projects happening simultaneously, this eventually caused me issues as I was later diagnosed with Severe Bi-polar disorder and the stress was causing me to have anxiety attacks. 

I managed to become the lead engineer in just one year, I had three crates not interface with the parts correctly and one broken part (I believe that was a "reader head" for Motion Industries) in two years over several thousand crate designs... Not to bad. I have done projects for every industry you can think of... In fact, if your in manufacturing and your in the bay area its quite possible we may have met before.

I taught myself to use solidworks and inventor, it does what I want it to so I have never changed the way I work... Never had an issue with the guys in the shop translating my drawings into parts.

Hope that is a suitable explanation

Edited by
Discussion_Admin

[Anonymous]

I used 0.25" holes cause I wanted to leave material for the threads, I though you were gonna hadle that lol 😛

[JDMather]

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@Anonymous wrote:

I used 0.25" holes cause I wanted to leave material for the threads, I though you were gonna hadle that lol 😛

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So what size fasteners are you intending to use?  The clearance holes and the "thread" holes were both .25

I thought you would use the Hole feature and have it create Cosmetic threads that I would simply change to cut threads.

In any case - I set to 1/4-20 and sent to the machine.

[Anonymous]

Well, your going to love this...

When I had solidworks and I wanted to make threads I would create a tool profile sketch for the thread and then make a sweep on an helical curve set to define the pitch, revolutions and cut depth. Its actually allot of work for A thread and I'm sure there is a faster way to do it. This why I was using the thread feature incorrectly 😞 Going to read your paper, hopefully I get something from it.

[JDMather]

That paper won't go through this - but if you go into the Hole feature command at the bottom right of center you will see an option to create threaded holes.
Inventor will then come up with a setting to select standard (in this case ANSI - Inch I would presume) and then the size.
It will automatically create tap drill size hole.
Same goes for the clearance hole - you could pick SHCS and counterbore and it will create "proper" size clearances.

Given the nature of the assembly though - I didn't expect this as a custom fastener might be appropriate.

SolidWorks Hole Wizzard does the same thing (but in a convoluted way in my opinion).

What you really want to lock down though is how you create your sketches - Inventor should do most of the geometry constraint work for you - with you adding the manufacturing measurment dimensions.

Some people think this is too much work at the conceptual stage - but actually once you get the hang if it - it dramatically reduces work and makes changes far easier.

On this design I would have used multi-body solids for the design so that everything could be controlled by 2 or 3 simple sketches.  http://home.pct.edu/~jmather/content/DSG322/Inventor%20Tutorials/Inventor%202011%20Tutorial%2014.pdf

[Anonymous]

Wow, taking me to school...

This joint is actually a side project from my internal combustion engine, I am designing an entire car from scratch actually. Its a daunting task, but since I have already finished a new motor design (Currently being redesigned to be simpler have less parts and be a bit tougher) and I have a new compressor design, a new suspension design, and a new type of frame design, plus the passion to pursue it. I think maybe at some point in my life I just might see my automodream come to fruition. It sounds crazy, but just think, 100years ago guys were building their own internal combustion engines in their home shops! Thank god they did, or we would not have half the knowledge of engines we enjoy today.

 I see you are in Pennsylvania?

[JDMather]

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@Anonymous wrote:

Were are you located? If you dont mind me asking...

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Short bio bottom of first page of this document

http://home.pct.edu/~jmather/skillsusa%20university.pdf

[Anonymous]

My shoe dont taste good...

I can learn allot from you.

Would you mind emailing me your phone number?