Leopard 2 No.12: General Improvements and Conversion to 2A4M CAN Standard

[Chang]

A very dedicated modification on this wonderful tank Aaron. Thanks for sharing the details.

Expecting for more to come.

With best regards,
Lerh Chang

[Aaron Cheng]

Sometimes, things don't go quite as planned.

Left to right: a disassembled bumper type B, 3 bumper type Bs assembled and brazed, and a very melted test piece.

Finished the bump stops for the no.4 and 5 road wheels about 2 weeks ago, but while practicing brazing the two halves of the bump stop together, I got a bit overzealous with the torch and ended up melting the aluminum. In hindsight I probably should have learned on the original kit-supplied bump stop instead of the parts I was going to use in the end, but better to learn the lesson on something that can be easily remade than on the hull plates, which is what I really wanted to braze.

The surface bubbling could be fixed with some careful filing and sanding, but the rear is pretty badly eroded, so I opted to just make another set. The M4 screw and washer hold the two parts in position during brazing, and is replaced with the rubber stop (CV0231) during assembly.

The bump stop is split into two halves to keep the geometry as close to the real thing as possible, and uses the original rubber stop supplied with the kit to make replacing the wear components easier (for me, at least).

In addition to making the replacement bump stop last week, I started prototyping for the type A bump stop as well, which finished this week. Other than the spring, all other components are new. The steel housing is pinned to the aluminum base via 2x6mm dowels to take up the spring pressure instead of the screws.

The plunger is actually a three-part assembly, with a hardened and ground steel dowel pin press-fit into the plunger base, and a Delrin (Polyoxymethylene/POM) cap to protect the paint of the suspension arms if they do contact. In my opinion the polished finish of the new plunger looks much better than the turned finish of the original part, and more accurately resembles the real thing.

A comparison between the original and the new bump stop. Unlike the return rollers, the bump stops will use the same mounting holes as the original parts so no additional holes need to be added to the hull side plates. Both bump stop types are tapped instead of cleared for their respective screws (M3 for type A, M4 for type B), so that the hull plates can be countersunk to keep the hull insides pretty clean compared to the original specification of using nuts.

I only made one type A bump stop first, mainly so I can confirm that the components are actually machinable, and to consider any machining fixtures that could be made to speed up the process.

For example, the aluminum base is a complex enough shape that a machining fixture is pretty much necessary for the final setup to prevent deformation to the part. That is why there are 2 additional 2mm holes in the back of the part; the machining fixture has a matching set of holes for a repeatable setup when doing the full batch of parts, even though there are no matching locating holes being added to the hull itself.

On the other hand, the steel housing does not actually need a fixture. You can hold it in a machine vise with some clever use of parallels, but I plan to make a machining fixture for the top and bottom setups (boring the cylinder holes) to cut setup times significantly. I actually spend more time putting the part in the vise, indicating and picking up the work piece than the actual machining, so using a fixture to significantly reduce the setup time on the other 8 parts (one is already done, and the 1st will always need to be picked up anyways) is the way to go for medium-sized batches of parts like this.