Quoted from DanLewell:
I think this clutch is used in King Tut as well.
I'm fixing one of those up at the minute, so might be in touch if the clutch on that is knackered.
Quoted from emspence:
Working on a King Tut here too that I picked up a couple days ago. Plastic cam is bad, attempting other hacks to tighten it down, but if you decide to sell these or share files, please let me know! Thanks for tackling such a vital, but missing part, looks great!
I have been trying to find out as much as I can about this group of Bally games including On Beam, Bowl-O, Joust, Rocket III, King Tut/King Rex and others that use a similar reset bank with a clutch. It looks like they all use different cam assemblies. A lot of the parts of the cam assembly are identical to those on Bally bingo reset banks, but unfortunately the bingos never used clutches.
Most Bally pinball reset cams, including King Tut, only use one clutch, and those definitely are different from On Beam. They may be the same internally. You can't just "tighten it down" - the clutch action has to work, it's a little hard to explain how it works - I'll do a video eventually. There is an outer collar that twists slightly one way to unlock and allow the clutch to be able to slip on the shaft. When it springs back, it locks to the shaft and turns when the shaft turns.
On King Tut, it unlocks to allow the score motor to turn without resetting the relays. It probably only locks at the end of a ball and the end of a game when the relays need to be reset. On Beam can reset each half of the relay bank independently during a ball, and has a separate score motor and reset bank motor. They were mechanical madmen at Bally in those days.
My broken On Beam clutch was glued and taped, which made it impossible for the clutch to work. If you just do that, it may unwind the spring (see below where I talk about my seized clutch).
There's a steel 2-piece spring clutch inside the On Beam cam assembly, and the spring has to be perfect for the clutch to work. My spring-making project is on the back burner right now, but eventually I will figure out how to wind them. I bought a roll of .040" music wire, so I can wind hundreds of them once I figure out how.
Take some good pictures of your cams if you can. If you take them apart, I'd really like to see what the steel clutch looks like inside. If it's the same, we should get a few made by a machine shop.
If the parts are similar to On Beam, it might not be too hard to modify my CAD model if I could borrow a King Tut clutch assembly to look at it and measure. I do it old-school, no 3-D scanner, just measure with calipers and do a sketch on paper first, then make the CAD model.
I took the whole reset cam assembly apart and cleaned everything up - it needed it. Anyone with a working game that uses a motorized relay reset bank should inspect the clutches carefully to make sure they can turn freely and operate properly. If the steel clutch gets some corrosion in it and seizes up, you have big trouble! On Beam has a snap ring and 2 roll pins that had to be removed to disassemble the cam shaft. Both metal clutches were stuck to the shaft and hard to get off. After cleaning up with solvent and 0000 steel wool, everything slides on and turns freely.
Mine looks like the clutch seized, causing the spring to be overtorqued and "sprung". I have tried to rewind it, and got it really close, but it has to be perfect for the clutch engage/disengage action to work. That one spring is keeping my On Beam from working properly right now...
Spring clutches are pretty cool little devices, actually. I tried to find a commercial replacement, and there isn't anything the right size. Bally either had them custom-made or bought a clutch that was available at the time, and made the plastic pieces themselves. Someone with a lathe could whip those out easily, and probably do the springs, too. I don't have any machine shop buddies nearby these days...
We're very close to having this totally figured out. A solid replacement for these clutches will bring back a bunch of games from this important Bally era!