In his video, Nick wondered about the suspension on the Pz61/68 - I found some material about it in both Ogorkiewicz's Tank Technology and a series of old International Defense Review articles by Shreier called "The Modern Battle Tank"
Ogorkiewicz lists both total suspension travel (compression to the bump stop and rebound) for a number of modern tanks and the more important number of compression travel to the bump stop.
- For total travel, the Pz61/68 is only OK; better than the Horstman on the Centurion/Chieftain, about the same as the AMX-30, slightly inferior the M60A1, and substantially less than the Leopard 1.
- The characteristics of the bellvue washer suspension are somewhat different than torsion bars; measuring only on the travel that is compression to the bump stop, the Pz61/68 looks much better: it's advantage over Horstman is greater, it's slightly superior to the AMX-30 and M60A1, and much closer, but still inferior to the Leopard 1.
Shreier liked the disc compression suspension but talks about it's mixed bag of characteristics, since the suspension response is different than torsion bars, he calls it "heavily damped" in comparison. Thus Shreier says:
- The Pz61/68 will have very good performance on undulating terrain and will have less "jump" when firing the main gun, but . . .
- The Pz61/68 will be noticeably inferior when moving over small obstacles, where the tank will be sluggish compared to torsion bar tanks
- In general, the Pz61/68 suspension is stiffer against small shocks but softer against large shocks
Finally, Shreier thought the suspension system had great promise, but bad timing.
- The great promise was from developed versions that combined disc springs and coil springs to get rid of the small obstacle problems noted above (these were test run on a Marder with good results) while keeping all the advantages of simple construction, simple installation, and no bars running underneath the tank.
- The bad timing was that the development took place right when hydropneumatic suspension was coming into vogue, with a variety of possible benefits that disc springs were never going to match. Shreier doesn't say it specifically, but the implication seems to be that the "conservative" approach was to stick with torsion bars and the "new-fangled" approach was to use hydropneumatic, so there was no constituency for developing the Pz61/68 approach.
I am neither a tank suspension expert nor do I play one on TV; I just know what I read in these articles but I thought it might be some interesting material to add to the Pz61/68 discussion.