Sunday, 20 February 2011

FMP - Three (18/02/11 - 20/02/11)

As promised I made a similar working model to that in the last update, but with a bar instead of a rod. The same principle applies, but to highlight the problem of only using one CAM I had one of each design along side each other (one CAM and then two CAMS):

As I was using a bar instead of a rod, to achieve the maximum grip between parts, I had to lasercut my own gears. This bar was slotted through acrylic rod which was in turn threaded and glued to the vertical dividing pieces, to strengthen and maintain the bar at an equal height along its length:
Back to the CAMs; the two different CAMs next to each other:

As you can see, the CAM device on the left is comprised of two CAMs; a secondary one fitted between the outer CAMs which freely rotates on a rod between these two outer ones. The vertical pole which is attached to the horse is also attached to the other end of this inner CAM and is again, allowed to freely rotate. So that when the outer CAMs are rotated up the inner one is also brought up, but as it's allowed to rotate freely, the end where the vertical pole is attached can maintain its vertical stance (due to it remaining over its centre point) while being lifted up:

And vice versa when it comes down:

The same can not be said for the other CAM device (the one on the right), which angles the vertical pole while going up and down, and as a result, needs a larger hole to be slotted through. Going up:

And coming down:

This angle at which this vertical pole becomes when completing its journey is obvious when compared to that of the outer CAM device. And as I mentioned before, the idea that the horse goes back on itself when brought up is clear in the following comparison photos. The nearer horse is attached to the two CAM device, with the further horse being attached to the one CAM device:

That is them going up, and it's clear to see the idea of the horse going back on itself.

And coming back down, notice the angle at which the vertical pole is at compared to the nearer one. Now the same comparison but from a different angle:

This has lead me to believe that even though I don't have concrete proof that in actual carousels they use this secondary CAM device, they must incorporate something incredibly similar as to prevent the horse going back on itself, which could possibly slide a rider off. It's also interesting to note that the secondary CAM horse doesn't go nearly as high as the other one.

This design is also titled as the most reliable method of getting a carousel to work and provides the smoothest ride. But from my perspective, via the making of these working models, it's also the most complex and fragile, requiring more engineering than lasercut acrylic pieces. For this reason I'm going with the below CAM design which I used on my first working model.

In other news, my gearbox motor finally arrived:

It's smaller than I thought, so I plan on attaching it upright instead of using bevel gears. Also from my working models the idea of using a bar is far more reliable than that of a rod, so I'm going to mill the rod coming from the motor square, and do the same with a larger vertical rod which will be the main centre point which everything rotates from. To attach the two I plan on milling out a square indent in one end of this centre point rod so that rod from the motor can slot up into it.

Along with the motor, and in preparation of using the below CAM design I've brought a small tyre (I had to order in 11 more as this is all they had, they should be available by Wednesday) and some springs:

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