CAD

The first hurdle was being able to draw up detailed plans. There are actually two sides to that hurdle. The first part was being able to illustrate what I wanted to build. But even more difficult then that was knowing what was needed...everything form external dimensions, to gauge of steel needed or to the amount bracing required. I collectively refer to all of this as engineering. If I under engineer the project, well obviously it will not function as well as I have envisioned. However, if I over engineer then it adds cost and weight. As the weight goes up, more horsepower and a larger volume hydraulics package is needed to meet the project requirements. Bigger power pack means higher cost and weight.

As mentioned previously, most of the CAD work has been done in SketchUp. It is a little light on some features, but is very quick and easy to learn. Free doesn't hurt either. It's primary focus is architectural design, but it can be used for mechanical design. As for subject material, the major source was a 1:35 scale model. With a pair of digital calipers, I worked out most of the dimensions. There was a couple of websites that also helped with the process: Achtung Panzer, Panzerschreck and PzFahrer.

One of the things that was a fairly big concern for me was accuracy in construction. While it is great to have plans laid out to the most minuet detail, actually building it that way is a different story. However, this is balanced against my desire to make the tank as accurate in detail and scale as possible. So there was a few things that had to be adjusted to allow for my current level of fabrication skills. A good example would be: a 8.015625" (8 and 1/64") long 14 ga 1" square tube with one end cut @ 23° and the other end cut @ 42°. Easy to draw, not so easy to cut to those specifications.

With all of this in my head, I tried not only learn the necessary CAD skills, but also design a tank I could actually build. Most of this was simply rounding up or down. The smallest fraction I used was that which is divisible by 8. Also, when possible I tried to keep angles to multiples of 5 as the gauge on my cut-off saw was only marked in increments of 5°.

Here is a look at some of my first CAD work.

Much of the final details (hatches, exaust vents, vision slits & etc) has yet to be modeled. As I continue learn, both in fabrication and CAD design, how I want to go about fabricating those details continue to evolve and improve.