I'm not going to release too many details at this point, but I have a new design and I am planning on building it. Here are the stats:
- LA: 2 feet
- CW drop: 6 feet
- CW: 15 pounds
- Projectile: Golf ball
- Sling: 4 feet
- Maximum possible design efficiency: 100%
- Axle height: 3 feet
- Total frame height: 3 feet
I'm quite happy to finally have a design where the efficiency is only limited by how well it is built (friction etc). That 100% requires no friction and perfect tuning, but not a massless arm, or anything like that. It also looks like the 100% efficiency should be possible with much higher mass ratios, and even more drop (CW drop is easy to add). I would also like to say that the only long beams in the whole design contribute to the CW, have no bending load (possibly a slight bending load during cocking depending on how it is cocked), and only a mild compression load. The whole machine should fold up very well (could be made to fold up just like merlin, but easier) and could be easily scaled up to trailer size. It has no rolling or sliding parts, and no moving parts that can hit each other excluding the sling and projectile. This means no arm vs. hanger whipper death, no FAKA end of track slamming, and no rolling axles, CW guides or anything like that at all. Because of this, and some other reasons, it should be relatively easy to build. There are some small complex parts, but nothing too bad really.
Also, it should be the easiest treb design to tune that I have ever seen. It should be able to be fully tuned by adjusting two things (one is the firing pin) which do not effect each other. You can literally adjust the release angle forwards of backwards any number of degrees (no guess and check ether!) with out messing up the other tuning (consisting only of the firing pin angle).
The one main issue that I see is that the sling can potentially hit the ground before and/or after the release. It is similar to a whipper in this respect.