In recent years several alternatives have arrived from sliding clutches to the (frankly dire) Werks Power Clutch, notorious for adjusting itself mid race. I've tried a few and never really found one I was happy with until I discovered the JVD-RC clutch system about a year back, since then I've been a convert and run one all season in my RC8T truggy. After a full year of racing and countless gallons here's the full SP.
The clutch in pieces
The JVD clutch is a four shoe arrangement, looking not unlike the Team Losi 8ight clutch at first glance. The main difference with the JVD is that the clutch pins are permanently attached to the flywheel as can be seen in the image above. Each aluminium shoe is drilled to accept a clutch spring, and the set contains a full set of each of the three common spring tensions (.9mm, 1mm and 1.1mm). The spring tensions with in the clutch can be set to precisely control the engagement of the clutch to help tune for track conditions, or to work around an engine with a weak low-end response. Typically I've run 4x1mm for most conditions in the truggy running a torquey but smooth Alpha Plus engine. In very loose conditions I'd probably drop to 2x.9mm and 2x1mm to ease the bottom end slightly.
Once all four shoes are fitted to their pins the main 'basket' can be added. It's at this point the JVD comes into its own, the basket tensions the clutch springs, but in doing so also serves as it's own clutch tool. Simply drop the basket on lining up the holes with the springs. Twist counter clock wise and the ramps on the basket will smoothly tension the springs. Finally press the clutch basket into place on the clutch pins and you're ready to fit the clutch to the motor. The photo below shows JVD's own tool for fitting the basket, in all honesty you don't need one as strong fingers are fine.
Using the clutch basket fitting tool to lock the clutch springs
The photo below shows the completed clutch ready to rock. One of the joys of the system is the the clutch can be fitted and removed from the engine as a piece. This means engine and clutch swaps mid race are a snap, and if you feel the need it easy to keep spare clutches built up ready to go in case the conditions change. Try doing that with your old three-shoe set up!
All done and ready to fit to the engine of your choice
The JVD set include a collet and specific clutch nut, plus enough shims to fit the clutch to pretty much any engine and chassis combination. It also runs a standard clutch bell (unlike the Losi clutch).
The clutch shown in the photos is the same unit I've run all year, the shoes having at least three gallons running on them, and they still have a ton of life left in them. I really do think that in terms of simplicity, ease of use and shoe life the JVD has every one else licked, and I can't recommend it highly enough. It's saved my butt on a number of occasions when I've need to change my clutch mid-race, with the JVD it's a snap and takes literally seconds.
So, what are the downsides? Well, it didn't fit my RC8B, the flywheel was too thick and rubbed the rear brake disk. Also, at present JVD only supply aluminium shoes and there's no UK supplier yet that I know of, so it's an internet only job.
On the upside, the unit is the same as the US Ascendancy clutch (JVD makes those clutches as well), and they offer three flywheel weights and composite shoes so if you're happy to order from the US you really can have the best of all worlds, and probably the greatest off-road clutch available anywhere.