The tail is manipulated by a string attached to the servo, which passes through a series of hooks before reaching the tip of the tail. So far the tail can only wave one way - I have to buy another servo to manipulate the tail in the opposite direction, but it will operate in exactly the same way.
I have reached my target of having a moving tail before uni starts, and with a week to spare so now I have to decide what to do next! After talking about it with dad, I decided that rather than using a chain of seperate servos to move the tail, I could use just one at the base of the tail to move the whole thing. To make it curve I needed a more flexible material than MDF. In order to make it possible to change between the existing MDF spine and the new material, I decided that it would be great if the new material could also be 6mm thick. To get the flexibility at this thickness I chose to use strip rubber, which is very flexible but has enough strength at 6mm to avoid collapsing on itself. This did mean cutting the tail off the dragon, but replacing it was very easy with a couple of joining plates and bolts. The tail is manipulated by a string attached to the servo, which passes through a series of hooks before reaching the tip of the tail. So far the tail can only wave one way - I have to buy another servo to manipulate the tail in the opposite direction, but it will operate in exactly the same way. The base of the tail tends to get stuck on the table - it works better on a flat surface, but I will still need to smooth the bottom of the rubber as it has far too much friction and bends towards the table too much.
0 Comments
It has taken me two days, but I have finally finished cutting the pieces of the dragon. Each piece was cut on the scroll saw, and they all fit together without any screws or glue.
I love working with this arduino Mega board - so far everything I have tried to do has just worked, and I can already see that it will make development much faster and less depressing, especially in comparison with my last attempt using PIC technology and hand wiring everything. About half an hour after I got home I had the first servo running, only to discover that actually I didn't know how to stop it... I was so surprised that it worked it took me a little while to remember to wire in a switch. I now have a momentary push button which enables the servos, which means that if I release the button they gradually come to a stop as they complete their respective routines. In future I will program this as an interrupt as it will be a safety device to stop the dragon trying to move further once it has reached the limits of the skeleton structure - I would hate for it to destroy itself on the first test! The button will also be replaced by a slider switch so that I can turn the dragon on and off properly rather than having to re-enable it each time it cycles through the main loop program. The circuits in this photo have been rigorously tested by a 3 year old who found the concept of pressing a button and having things spin fascinating for about an hour. I figure if it can survive that, I'm on the right path. My only issue so far is that the tower-pro servos are incredibly noisy - I think for a lot of the more important servos I will have to invest in better quality servos which have metal gears instead of plastic so that they are more accurate and less loud. Today some of the parts I ordered from littlebirdelectronics.com arrived. The order so far has been very prompt, and even arrived in a great box which I will use to store lots of bits and pieces while the dragon is under construction. This includes an Arduino Mega, which I hope will act as the dragon's sole control board. This board has 54 i/o and can control about 40 servos, so I hope it will allow me to expand significantly before I need a replacement. My order also included 2 servo motors, which will form the first part of the dragon's motion ability. These will probably both be used to manipulate the tail in the first stage of the electrical installation. This order also included a lot of hook up wire and other connectors so that I can get started on building and testing the electronics.
Tonight I cut the pieces out of an A3 copy of the skeleton drawings and traced them onto 3mm MDF in preparation for cutting them later this week. The Dragon consists of 24 seperate pieces which will have to be individually cut. The spine is not on this board, because it is going to be cut from a piece of 6mm MDF to give it extra strength. The pieces are laid out in strips so that the wood can be rough cut using a table saw in order to make it easier to handle. Each of the ribs and other symmetrical parts were cut from paper, folded in half and marked to indicate the center to both ensure that the parts are even on both sides and also to help allign the slots which will be cut into the parts to allow them to slot together. The actual layout is slightly different because I decided not to place pieces within the ribs to make it easier to cut. cutting layout for skeleton Well, if I'm building this thing I'm going to need some materials - I started tonight with some 6mm MDF for the spine/head and hips, and 3mm MDF for the ribs etc. as well as some hinges and some sand paper from Bunnings. I am going to start planning the electronics and what I need to buy for that tomorrow.
I finished the initial skeleton design work and rather impatiently wanted to see if the concept worked the way I was picturing it. To test it out I scanned the pages of the design and printed them onto A4 card. Overall I am pretty happy with how the design works - I was especially excited to have the shoulders and hips fit together and sit flat along the ground! I have already discovered that one of the most difficult parts of the dragon to get looking right is the head, and I have had particular trouble with the horns and nose regions. These are the only parts I have had to alter from the inital design (so far), and I expect that making the face look right will be an ongoing difficulty. The horns I started with had a wavy edge shape, which looked ok in theory but once I cut them out it looked like the dragon was wearing lollies on his head! The new horns are double arc shapes which look much more menacing. The jaw is designed to hinge from the skull, and is only attached by a split pin at the moment. When constructed from wood it will be made by two parallel sections connected at the tip and pivoting around a point on the base of the skull. In order to make it more realistically shaped, I may need to add in additional ribbing on the lower jaw. Fron the initial sketches I spent most of last night drawing the skeleton, and completed it today during lunch. The whole thing will hopefully fit together like a 3d Jigsaw. I have decided to build a 3d animatronic dragon.
After a couple of days of planning how to construct him I spent a fair bit of today designing what he will look like. So far, I have a sketch of the overall shape, and I have started to draw the templates for cutting out the body frame (skeleton). In fact, I got so into drawing that it is after midnight and I only have the tail section to go - that will have to wait until tomorrow! |
AuthorTess is an Engineer who sometimes gets a bit carried away with her hobbies, which include animatronics, uavs and millinery. Archives
March 2015
Categories
All
|