May 2002

Thursday 2nd May 2002

I went to see Ian my local metal supplier to see what options I had for cladding the hog. I had worked out that if I used mild steel sheeting, it could be no thicker that 0.5mm if I was to stay within the weight limit. At this thickness I felt that it would be too flimsy to be of any use at all. Aluminium seemed to be the next best thing, and Ian had a 1.2mm thick sheet of it. I had spent the previous evening cutting out cardboard templates of the different panel I needed, so Ian set about cutting these out and bending them into shape.

I had also planned to get an approved CO2 bottle with a screw down valve. Unfortunately these were proving difficult to get hold of because they were not being made any longer. Apparently new European rules were coming out soon, and manufactures had stopped making the old types some time ago. They were also reluctant to make just a few at a time, and wouldn't contemplate starting up a production line unless there were several thousand needed. I'm not sure where this leaves me, but I will have to check whether the same situation exists with the 1.1kg bottles as it seems to with the 2kg bottles.

I had my first bit of press coverage today in the Mid Sussex Times. A local news correspondent had seen my web site and had asked for some more info so that he could put an article in the local papers. I had submitted a resume of what I had done so far, and had also sent a photo. The paper had included the photo and summarised my three pager into a few paragraphs. To see the article, click here.

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Monday 6th May 2002

I started to fix some of the aluminium panels to the front of the hog. The two front side panes had a fold in the middle, which provided a well needed bit of stiffening to the plate. It also showed how difficult it is to try and cut out accurate cardboard templates. I had to trim bits off here and there to get the sheet to fit snugly into place. Fixing the plates was done by making up some small metal tabs and welding these to the chassis' box sections. I then drilled them and "tack" welded a nut the back of each tab so that I wouldn't have to fumble around trying to hold the nuts in place while I screwed the plates on.

Head cladding, top view Head cladding

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Wednesday 8th May 2002

There was some confusion about what pneumatic bottle valves were acceptable and which ones weren't. After talking with Derek Foxell I established that a screw down type and a squeeze grip valve were both acceptable. This meant that I could use the CO2 bottles I already had, but would need to get them checked and stamped by a suitably approved agent.

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Wednesday 15th May 2002

I went to the company Life support service to get my CO2 bottles tested and stamped. I decided to get two of the bottles tested so that I had a spare should one get damaged. The guys Jim and Dave were extremely helpful and had already helped quite a few roboteers with their pneumatics. They also sponsored the robot "grim reaper" over the last few years so were quite up on what was needed. Jim was the guy who helped organise the Sussex Robot rumble event for the scouts earlier this year so I might try to enter this event next years. They provided me with a few adapters and fittings so that I could attach my paintball regulator to the fire extinguisher CO2 bottles. They didn't have all the adapters on the shelf, but said they would post them on early next week.

One bad bit of news was that the old Halon fire extinguisher bottle I was using as my buffer bottle could not be tested. It was a welded metal bottle, and unfortunately this type of bottle has a fixed life after which it could not be give a certificate. My options were to use one of the smaller aluminium bottles that they had in stock, but I felt that these were much too heavy. What I wanted was another light steel tank similar to the old one, but less than 5 years old.

It then dawned on me that I may be able to use the CO2 gas bottled that came with my MIG welder. This was under five years old, and held a similar volume of gas to my old bottle. Jim said that they could put a larger fitting on it to increase the flow rate, and give it a certificate of compliance. When I got home I emptied it of gas and packaged it up ready for posting to them tomorrow.

Late in the evening I started to make a bracket to mount the larger CO2 cylinder in the Hog. New CO2 gas bottle mounting bracket

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Friday 17th May 2002

I sent the gas cylinder off to Jim at Life Support Service for modification and pressure testing.

A dozen cladding mounting tabs I started to work again on the cladding and spent most of the evening making a dozen little mounting tags. They were only small, but took a long time to cut out, drill, tack weld a nut to make it captive, and then run a tap through it to clean out the threads.

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Monday 20th May 2002

I mounted the upper side panels to the Hog and then weight it. It was horribly close to the 99kg, and this was without all the extra pneumatics I still needed to install. This convinced me that I would have to cut some more metal off somewhere. I was reluctant to spend a lot of time drilling holes and cutting metal off the thinner box sections of the robot since I would have to drill and awful lot of metal to get any sizeable weight reduction. Also if I removed metal from the smaller box sections, it would leave the already weakest items even weaker. I therefore decided to have a go at the self-righting tail. This was made 6mm aluminium that was bolted together into a T section. I could cut out quite sizeable holes and still leave the structure strong enough support the Hog during self-righting. It took a long time to cut one sizeable hole, but that was all I had time to do this evening.

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Wednesday 22nd May 2002

I decided that I wanted a break from cutting and filing lumps of metal off the tail, so had a go at building a support frame that would allow the Hog to be raised off the ground for testing purposes. This was one of the items that rules said I must have in order to test the robot without it being able to move. I had given the design a bit of thought, and wanted the framework to be able to support the Hog safely on it's back or sides as well, so that I could work on it more comfortably without having to chock it up with large lumps of wood. By the end of the evening I had a framework that seemed to fulfil three functions.

  • Hold the wheels off the ground while the robot was in its normal running position.
  • Support the Hog on its bum so that it was stable enough to be worked on without falling over and without getting in the way of any bolts or fixings.
  • Support the Hog on its side so that it was stable enough to be worked on without falling over and without getting in the way of any bolts or fixings.
Hog in its cradle, running off the ground Hog in its cradle, sitting on its bum The hog in its cradle, sitting on its bum The hog in its cradle, lying on its side

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Friday 24th May 2002

I received the pneumatic parts from Life support services that allowed me to connect the larger CO2 fire extinguisher bottle to the paint ball regulator.

The MIG gas bottle had been fitted with a larger outlet and given a pressure test certificate as well.

MIG CO2 bottle with standard welding outlet
MIG CO2 bottle with new larger outlet adapter

Also included in the parcel was my filling rig that now had the correct adapters to allow it to recharge the CO2 fire extinguisher bottle.

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Sunday 26th May 2002

I welded on four handles to the Hog's carrying cradle and gave the whole structure a coat of undercoat. It was looking quite good now, but the only trouble was that there wasn't' a great deal of room in the garage to roll the Hog around on it. If I took the robot out into the driveway, I could fit the cradle to it, and then roll in about onto each side. When within the garage I would have to manhandle the Hog onto it's side and then fit the cradle to it afterwards. A bit inconvenient, but at least the cradle would hold the Hog a lot steadier that resting it on blocks of wood while I worked on it. The Hog's cradle, now with handles and an undercoat
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Wednesday 29th May 2002

The weight limit was still praying on my mind, but a couple of bits of inspiration popped into my head today. The first was concerning the cladding I wanted to use on the Hog's ears. I had initially thought of covering them with thin sheets of steel or aluminium, but the area was quite large and would have added a kilogram or two to the weight. I popped down the road during my lunch break to have a look at a couple of fabric shops. There I found some leopard skin looking furry material that might do the trick. They had an offcut from the end of the roll that they let me have for a fiver that should cover both ears. There should also be enough left over to cover the side wheel panels as well. Using this material should substantially reduce added weight on the ears.

The second thought I had was about the pneumatic buffer bottle. The new one I recently had modified by Life Support Services weighed about 1.5kg, and was supposed to provide a small reserve of CO2 gas for the sudden demand needed by the flipper. However, it dawned on me that I had a reservoir of CO2 already in circuit. Under normal conditions with the self righting tail down, the upper half of the self righting ram is being fed with pressured CO2. Since it has a bore of 65mm and stroke of 200mm, it holds about 650cc of pressurised CO2. If the worst came to the worst at weigh in time, I could remove the buffer bottle completely without too much impact on the flipper performance. I had a quick look through all my spare pneumatic adapters, and I reckoned that I had enough of them to remove the buffer bottle completely, but still ensure that all the pneumatics worked okay, and I had all the safety features required still in place. It would not be my preferred option, but at least I could compete in the wars and still be legal.

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Last updated 11th June 2002