March 2003Thursday 6th March 2003
Things we looking quite good, but it was now becoming a bit big for the work bench and a bit heavy to keep shifting around. What I needed was to find some room on the floor in the rest of the garage, but for the moment the Hassocks Hog 1 was still occupying this space. Over the coming weekend I will have to rearrange things to see if I can get some more floor space. |
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Sunday 9th MarchThis weekend was quite productive with me first managing to shift the Hassocks Hog 1 into a corner of the garage, thereby leaving a space on the floor to put Hog 2. Because Hog 2 was quite a bit shorter that Hog 1, I could rotate it without it snagging on any other object in the garage. This made it a whole lot easier to work on the flipper, which was now the focus of my attention. I took a few more measurements of the chassis and entered them into my flipper calculator to get the best geometry. According to the spreadsheet, it should be able to lift just under 600kg at the flipper tip, and toss a 100kg weight 40cm into the air. This seemed about the best performance I could achieve given the chassis measurements, so I spent the rest for Sunday building the flipper itself. By the evening it was 90% there with most of the structure cut and welded together. All than remained to do now was fit a shovel end of some sort at the tip, and to add a of small lever at the rear that would be used as a self righter should the Hog be stranded on its backside. |
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Monday 10th March 2003
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Wednesday 12th March 2003
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Thursday 13th March 2003I received some sample plastics from Display Development Ltd, who I had been talking with over the last week. They sent me small sample blocks of polycarbonate, polypropylene, and foam PVC for me to look at. I took some measurements and weights and worked out the density of each material type as follows.
With these I could now work out the weight of the cladding I wanted to fit simply by working out the dimentions and thickness of the plates I wanted to fit around the chassis. My first attempt was to used 12mm polycarbonate on the vulnerable parts and 6mm polycarbonate on the rest. This came to over 20kg of plastic, which I think will put me over the limit. I may have to use either more of the foam PVC and polypropylene to keep the weight down, or alternatively I might settle for thinner sheets all round. I will review the situation when I have all the rest of the components bolted in place. |
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Saturday 15th March 2003
I also connected up some more of the pneumatics, but couldn't complete all the piping because I didn't have a regulator or buffer bottle yet. During the week I had been talking to Jim from "Life Support Services" who had offered to make me a custom build high flow rate regulator. He was also going to make me a 1 litre buffer tank out of an old MIG welding gas bottle by welding large connectors at either end. I wasn't expecting these to arrive until the week after next, so it will be a little time before I can progress the pneumatics any more.
The motor controller still needed sighting on the robot, but I wasn't sure where to put it yet because I was giving the pneumatics priority. They could have gone either over the wheel axles, or at the front of the robot, but until the regulator arrives, I wouldn't know for sure where they would be best sited. I checked the weight of the robot, and found that it was about 75kg. This didn't leave a lot of weight for cladding, but I was almost finished with adding extra bits. Keeping to the weight limit was still going to be a challenge, but I won't get to this stage until a bit later on. |
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Thursday 20th March 2003
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Friday 21st March 2003
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Saturday 22nd March 2003I tested out the pneumatics as best I could today, given that I didn't have all the components like a high flow rate regulator, and valve controller. Instead I connected a few trailing wires to a couple of the relevant valves, and ran a long piece of pipe from my CO2 gas bottle to the buffer tank. By connecting a battery to the trailing wires I could fire the pneumatics while standing a safe distance away from the Hog. Initially the flipper shot a couple of go kart tyres a long way into the air, but its response in trying to self right was a little disappointing. I had based the pneumatics on the robot M2, which solidly threw itself back onto its wheels, whereas the Hog certainly was not throwing itself anywhere. I did a bit of head scratching and then wondered if the high flow rate valves were "soft starting". These valves had to be operated by a 10 bar gas feed which came from the main 16 feed through a second regulator. I hadn't bothered to check the pressure on the downward side of this second regulator so thought that maybe it wasn't high enough to operate the high flow rate valves quickly enough. To check it out I connected a pressure gauge to the downward side for this second regulator and noted that the pressure was about 5 bars. I adjusted it up to 10 bars and then tried the flipper again. This made a tremendous difference and not only did the flipper now shoot a couple of go-kart wheels as high at the roof of the house, but when trying to self right, it really did throw itself off the ground. You can see it in action on my video page, or by clicking here. Saturday 29th March 2003Now that I had gone as far as I could with the pneumatics because I was awaiting the delivery of my custom build high flow rate regulator, I turned my attentions to sighting the motor controller. I had initially hoped to put it somewhere at the front of the robot, as far away form the motors as I could. However, the routing of the pneumatic piping was occupying a lot of the space immediately above the batteries and would make it next to impossible for me to mount the gas bottle there as well. This left only the front of the robot in which to put the bottle, and therefore the motor controller could go nowhere else but right next to the batteries and motors. Not ideal, but I have little choice at the moment.
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Last updated 6th April 2003