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Steel Cobra

Day 8 - Sunday 25th May 2003

Okay, so it's been a while, and as a result, it was about time I spent some more time on it. However, I do have a number of excuses, the main two being "running out of steel", and "being on a very short notice to fly to Germany so I couldn't order any more".

It eventually arrived. All 98 metres of it. 98 is quite a lot, and to be honest, only a small amount (20m) was actually for the Cobra, with the next two projects' steel being ordered as well. I also tidied the steel so that it's hanging on a wall:

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Making the seats

I've got a pilot, but he's got nowhere to sit. That means it's time to make some furniture for him. First of all, a simple plan - a piece of right angle, and a flat bar:

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Now the basic design and size has been defined, it's time to make two seats (pilot and copilot):

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Once welded, the look a little more like seats:

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Altering the pilot

Although the pilot's nice and silver, he does have an annoying feature - the hood of his jacket. In order to make him sit right, a little surgery is required:

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Pilot's seat in position

I'm British. This means we drive on the left, with the driver to the right. So that's the first seat to put into place.

After trying various positions, I needed to cut the bottom of the seat quite dramatically, and I also put a crossbeam on the floor to weld the seat to:

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And with the pilot in place:

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And now putting the copilot's seat into place:

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Edging the windscreen

The windscreen is designed to take some perspex, but it needs a ledge for it to rest on. Some small (13mm, ½" wide) strips were welded just inside the windscreen to give it a ledge.

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The problem with the undercarriage

Ever since I'd made the undecarriage, I'd had this nagging doubt that what I'd done was the right way to do it. The weight of it all was about a third of the weight of the frame, and the motor was under a lot of stress. As a result, I decided to experiment with the gas springs I'd bought a long time ago.

Experimental gas spring

The gas springs are quite long:

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Unfortunately, I've only got two of them, so if I want three legs, I'll have to get another one. The idea was to use this one as an experiment to see if it would be possible to latch them in the closed position, and then allow them to spring open when the undercarriage was down.

The first stage was to put a ring around the end of the spring, to give the latch something to hang on to. An M8 washer was welded to the end for this purpose:

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Next, the spring was bolted to a bracket that was made from 25mm wide strip, like the main frame:

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Then, the front was held in place:

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A simple latch was made - this was mark 1:

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This needed somewhere to affix to:

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Unfortunately, the latch part didn't mate with the washer, as it was too high. Putting a kink in the latch allowed it to fit:

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Mark 3 of the latch allowed it to be opened easily by extending the back:

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Finally, a bar was added to the bottom to aid in stability and strength. This also allows the actual spring length to be adjusted by welding a stop onto it:

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With it extended, it looks quite impressive:

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Holding it in place

I decided to replace one of the side legs, as this was the easiest to get to. I added two more pieces of frame work to the top of the model:

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And then I welded the spring with its latch into place:

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The problem with the spring

After making the spring, I decided that this wasn't the way to do it:

  • It took a very long time to make the latch and the frame to hold the spring.
  • It was very difficult to push the latch in (I could've lost some air in the spring, but that may have meant that the spring would've shut under the weight of the model).
  • The spring was a little too long.To me, it would be amateurish to have to push the legs in one by one.

As a result, I decided that pneumatics were the way to go. Three smaller cylinders, a welding gas bottle, some pipes and a pneumatic switch was ordered on the 27th May, with all but two cylinders arriving on the 28th. I've now got the cylinder moving up and down with the switch (it was the first time I'd done anything with pneumatics, so I was quite surprised that I'd ordered all the right bits). Once the other two cylinders arrive, I'll be able to fit them.

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Updated: 2013-03-24 11:45:43 | Comments: 0 | Show comments | Add comment
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