Well after looking around and seeing that quite a few people are building antweights and hearing rumours that antweight walkers are possible i'm going to make one, to add to my collection of junk around my room.
I will go through the various steps as they happen to show what happened and what went wrong! (if it does, which it will).
Also need a name? Type 0 seems appropriate at the moment. The end of the old generation of robots and the beginning of a new. I might use that next time Philippa asks me why I went out early.
Looked at the internet to see what was happening, did a bit of work, got bored and thought about the walking sequence and how many legs to have. I've seen the Stamp robots which have 6 legs but they look very unstable as they walk. When trying to work out the sequence no matter how many legs you have ideally some are in the 'up' state while others are in the 'low' state. See sequence below:
I was very impressed by the Protech servo's I used in Oddysey so I'm going to get 2 more of those at the weekend @ £17 each. I should also get another 40Mhz receiver as I will need a replacement for RW anyway. Nothing special as I have 300g to play with which is quite a lot considering the normal ants will be 150g.
The round things are gears which power little legs providing go. There are 8 vertical legs at the moment as that seems the easiest option at the moment. It might go to 6 legs at an angle later to provide more stability.
The batteries will probably be the Maplins ones as they have proved their worth and are easily made into little 6V, 26g battery packs.
I'm not sure about a weapon at the moment but I do have a spare big servo at the moment which spins continuously when turned off (controller burnt out), which I might use on one of those Dremmel cutters. I've seen nice little 40mm diameter diamond cutting disks!! Could even made a gripper on the front to hold robots.
Looked on the internet today while at work and found lots of pictures of other walker robots people had built. Pics left at work but there are a few nice pictures i'll post soon.
Well I went home over the weekend to fix my brothers computer and also very convienently went to a local model shop at the same time. This is what I brought for the walker:
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Here are 3 Protech servos, 2 to be modified as motors and 1 as as a weapons motor or
just as a spare I will show the steps in modifying one of these servos soon. I also saw another type of servo at the model shop. The Protechs are 16g with 2.5kg/cm at £16.99. At the same cost are 9g servos which produce 0.8kg/cm of torque (yes I know kg/cm isn't right, blame the radio control enthusiasts). At the bottom is a stripped down big servo which I accidently overloaded a while ago (IC burnt out and now spins continuosly). |
| Clockwise from top left. 27MHz receiver, 40MHz receiver as a spare for RW and as a receiver for the walker (28g), mixer (essential for a walker as the legs need to go on both sides for it to turn well), and last of all a 27MHz stripped receiver. |  |
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Batteries! 4 loose ones at the bottom, with a constructed battery pack at the top. |
| Materials. 1mm aluminium on left, 1.5mm polystyrene on the right and aluminium car body mesh in the middle. It looks good and doesn't weight much. |  |
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Ah ha.... Found my Maplins catalogue at home at looked at the Dremmel cutting disks,
too small (22mm diameter). Turned the page to find a Dremmel bench circular saw, and beneath it spare cutting disks. The picture shows the 60mm wood cutting disks but there are also 50mm diameter metal cutting disks. |
However for all this stuff I brought I had some troubles finding some decent gears to use, I have found some but my brother is getting a bit upset every time I steal his LEGO stuff.
ALSO: I thought most of the people who look at my page are semi technical but no-one worked out that the pictures above of a walking sequence would not work! You need an idler gear between the big gears so all the gears spin in the same direction (something that the pics do without the gears).
Sorry about the file sizes (210K, 130K) but when I converted them to RealVideo quality was lost and you couldn't see what was happening. I did however zip them to 167 and 97K respectively.
I also found these pics showing the splayed leg approach which would obviously give more stability but make the robot wider:
Over the weekend I modified the servos to spin continuosly and there are quite a few pics and I know not everyone has fast modems so click HERE TO SEE HOW TO MAKE AN ANTWEIGHT MOTOR
I also sorted out the receiver, mixer and batteries which will be shown in a few days along with a 'finished' walking robot 'a la LEGO'.
Sorry about the delay, I did the video grabbing a while ago but didn't get round to updating my page due to a hard week at work. The files are in Real Video format and zipped:
The Short legged version (H,W,L=65*120*120mm) was very stable and hapily plodded about with the walking gait that you don't realise till you see it. The turning rate was a bit too large so I increased the leg length.
With Long legs (75*120*120mm) the walker turned a lot better but it looked unstable in the way it walked. It also kept breaking as the video shows with one of the legs falling off and one of the servos slipping from the gear train.
 I've got too make
a few adjustments such as changing the gear ratio to make the walker walk faster as well
as the various dimensions to see what happens:Various dimensions are easily altered such as the leg length B, and the lengths C+D. The radius A is slightly harder to adjust as I'm using LEGO at the moment but I have now read that a company called Muffett produce small plastic gears which might be appropriate. At the moment the LEGO gears have a large diameter but a relatively small A dimension. This results in my walker being 120mm long (<5") when the rules state that the walker is to be contained within a 4" cube. However once the walking sequence is mastered the weight (225g) and size issue can be worked out. I also found out that Maplins sell gears and small chains but at a relatively high cost for the amount I need. I will investigate and report back as Maplins also sell the big saw weapon I will be using. |
Sorry about the delay but I've been waiting for a Muffett catalogue to arrive but it hasn't yet. I'll chase them up tomorrow. However I found these two pics from the American RW, but these are BIG robots. The leg mechanism is the important bit however and the way the pivot is above the cam.
Sorry about an even bigger delay. I eventually receiced a Muffett catalogue with CD!! I decided whcih gears I wanted and emailed off my order (one type of gear not in stock so I choose another), and then received the order the next day. Hows that for service??? Well I now have my final gears which I am going to use in my final antweight walker. Here are a few pictures of the LEGO based walker I have at the moment, with the short and long legs.
Here are a few CAD pics I knocked up before ordering my gears, just to be sure that they would work. The gears are MOD 0.7 and have 15/30t respectively. The two big end gears will be driven from the servo motors.
Bit of a delay there, one of the reasons for using LEGO is that it doesn't need tools to put it together. I had the gears from Muffett but I did not have the tools to make the walker, but once I got them from home I had a good play and this is what I came up with:
The gear on the left is powered by the servo and a gear train makes all the large gears Mod1, 28t all turn in the same direction. At the moment the small gears are held in with small bolts but this will be corrected. Also I only have one side og the robot done as it took 2 days to get the above work doen due to the fact that the metal legs are very hard to attach to the rotating gears and keep the gears turning. I will get a picture sometime but essentially a bent paper clip goes through the gear and holds the metal leg. Two black bits of rubber then hold the leg in place and stop it falling off. The metal things at the top hold the legs so that when they go round the bottom of the legs move but the top stays stationary, thus it walks.
I will get a video of it moving sometime but the problem is that the small gear attached to the servo gear tends to jump out of position as it is not securely held in place (double sided tape).
Right since I made one side of the robot as above I haven't done any work on as I've been thinking and working on Griffon.
I finally got some time to develop this robot and give it a name, and after long consideration it is going to be known as TYPE 0. i.e. the first antweight. The pics below show the latest stage:
The new legs are made from 3mm diameter aluminium tube section from Hobby stores in St Albans. Considering the look of it it moves very well and as the saying goes "turns on a penny", it also has quite a lot of push available even though it doesn't have grippy feet yet. The top gears are held on with screws which has to change, but the big bottom gears are held in with little plugs I made from PTFE to cut down on friction.