Rotary transmission with linear guidance

[CharlesF]

HI all,

My background isn't in engineering so please excuse any ignorance. I'm Designing this mechanism driven by two powerful DC motors to automate the goal keeper on a Foosball table.

For obvious reasons I'm trying as hard as possible to keep the inertia of the moving parts as low as possible. With this in mind I designed the system the system below but I'm having a hard time finding the ball spline shaft that allows the linear guidance whilst providing the rotary drive for the kick.

The quote came in at 450euro which is a little over my budget. THK Ball Splines Model SLF
So my questions are;
Is there an obvious and simpler alternative which I'm missing?
If not, is the shaft pictured below the appropriate solution?

Any further input is highly appreciated.

PS: Ignore the frame, it's WIP

 

[MikeHalloran]

You could probably save money by renting an engineer.

Mike Halloran
Pembroke Pines, FL, USA

 

[CharlesF]

That's not a helpful answer!

The mechanism is fairly simple, I'm just looking better alternatives should there be one.

 

[hendersdc]

McMaster can get you there for about half the price: [URL unfurl="true"]https://www.mcmaster.com/#spline-bearings/=192k5wk[/url]

 

[hendersdc]

Misumi may be even cheaper: [URL unfurl="true"]https://us.misumi-ec.com/vona2/mech/M0100000000/M0106000000/[/url]

 

[gruntguru]

Since you only need about 120 degrees of rotation you could use one segment of a geneva wheel with a long "pin" for the driven wheel to slide along. The motion ratio (slow-fast-slow) might be advantageous for accelerating the shaft smoothly.
Link

je suis charlie

 

[CharlesF]

Fantastic, many thanks!

@gruntguru That's an ingenious solution, as you said the non-linear acceleration may would contribute towards the kick. Am I right in guessing it reaches it's peak when the pin is closest to the center of the geneva wheel?

 

[gruntguru]

Max velocity at the centre point. (assuming constant input velocity) Acceleration will peak somewhere between start and centre point and goes negative after centre.

je suis charlie