Need help building a mechanical "forcer"

[xEden]

Hello!

First, I should inform you that this isn't exactly for a robotics project, but since there seem to be a large amount of knowledgeable people around here when it comes to mechanical systems, I thought this would be a good place to ask! Here is what I'm working on:



You might be wondering what this is, so I'll explain. This is a NeoGeo board, which is an ages old arcade system that uses interchangeable cartridges. Among all arcade boards, it is the most common target for "Consolization" projects (Transforming the arcade board into a home videogame console). I've designed a nice looking case for it, and I'm throwing in a couple of extra gimmicks.

One of them is a mechanical cartridge ejector. Take a look at this:



See those holes around the cartridge connector? They are unused, and my idea for the ejector is as follows:

A metal rod would rest on each one of the holes (2 on each side). When a momentary button is pushed, the metal rods move forward, forcing the cart outwards. A decent amount of force is required, but it isn't too much. I'll use 1 motor per rod if I have to.

I've thought about a way to do this (4 motors with piston-like mechanisms), but I'd like to hear you out first. What do you recommend?

[Soeren]

See those holes around the cartridge connector? They are unused,

Bad design! They really ought to have been bolted in these holes (which is there for the very reason), to avoid straining the solder joints.

and my idea for the ejector is as follows:

A metal rod would rest on each one of the holes (2 on each side). When a momentary button is pushed,

How often do you change the cartridges?
Sounds like overdoing things to me, but hey, your choice.

A decent amount of force is required, but it isn't too much.

Ahh, then you need 1 or 2 or 4 motors that is suitably strong, with a current supply that isn't too big, but not too small either.
And the available room behind the edge connectors is what... Ample, considerable, a bit small? 

I've thought about a way to do this (4 motors with piston-like mechanisms), but I'd like to hear you out first. What do you recommend?

Well, it's rather hard to say what would work and what wouldn't, when you leave out important stuff as where and how much room is available to do it, how much distance there is between the cartridge and the connector part with the hole and so on.

If there's room for it, an axle with a cam rotating 90° could be the ticket. A flat headed bolt could be pushed or turned up against the cartridge through the holes etc. Plenty of ways to shave that goat, but impossible to device without some technical drawings (however crude) showing the metrics around the connectors and showing how much room is available.

So, present some data and use numbers rather than adjectives, then I'm sure you can get all the help you want.

[Aberg098]

Just to reinforce Soeren's point: It's hard to suggest ideas when I have no reference as to the force needed to eject the cartridge.

Is it similar to old Nintendo consoles, like the NES or SNES where this is easy? Is it similar to the amount of force needed to insert a PCI card in your computer's motherboard where this is not so easy?

I think you should also consider where you will be applying this force to the cartridge. Is this area well supported and able to take and transfer the ejection load? Will you wear out this area by pushing a metal pin into it?

[xEden]

How often do you change the cartridges?
Sounds like overdoing things to me, but hey, your choice.

I am overdoing it, no doubt about that, this isn't essential in any way. However, I'm doing this just for the fun of it, so that's exactly the point   

Well, it's rather hard to say what would work and what wouldn't, when you leave out important stuff as where and how much room is available to do it, how much distance there is between the cartridge and the connector part with the hole and so on.

As for the room available behind the board, I was originally planning on 4cm deep & 7cm high, but since the case hasn't been made yet, both height and depth can be adjusted at will. A custom enclosure for the mechanism can be built.

Between the area of the cart the pins will push on and the holes on the connector, the distance is 13mm, and the cart needs to be moved at least another centimeter forward in order to be fully detached. From the cart surface to the back of the board, it's 18mm. The holes themselves are 3.4mm wide.

The bottom holes are 47mm high and the top holes are 55mm high, but the board can elevated up to 2cm if needed.

The power supply this board runs on is a 5V/3A wall adapter, but I can replace it with one up to 16V if necessary.

Just to reinforce Soeren's point: It's hard to suggest ideas when I have no reference as to the force needed to eject the cartridge.

Is it similar to old Nintendo consoles, like the NES or SNES where this is easy? Is it similar to the amount of force needed to insert a PCI card in your computer's motherboard where this is not so easy?

It's hard to give you an exact idea, but it's considerably harder to remove than a PCIe card. I can loosen up the connector pins slightly, if necessary.

I think you should also consider where you will be applying this force to the cartridge. Is this area well supported and able to take and transfer the ejection load? Will you wear out this area by pushing a metal pin into it?

I have. It's 4mm thick plastic, and I will coat the pins with soft rubber to prevent damage.


Thanks to you both   

[Soeren]

Hi,

The bast way to separate from an edge connector is by applying pressure between the two points (if that makes sense, as then, nothing else is strained.

A very rough and ugly sketch of how this could be done:

A single gear head motor could pull a wire , with a pulley on each bolt, so releasing both sides simultaneous.
You could use small springs or similar to return the "separators", or you could let them slide back when a new cartridge is inserted.
Besides wire, the separator could be made in one piece for both sides of a connector.

Whichever solution you end up with, make sure it doesn't bend the PCB or something like that.