So.... I was over at a Friends house last week working on the transmission in his Son's race car.... He is an Electrical Engineer who owns his own consulting firm. He knows I'm big into older pinball machines, he's seen my collection & we've talked about electrical issues with them in the past. I was talking to him about cutting some windings off of coils for more pop, & reaching point of diminishing returns etc, to point where you can make the coil weaker etc. I know this is a semi common trick at least on EM's... & he made the comment, why not just lighten the plunger, rather tan try to make the coil field stronger? Hmmm... never thought about that.... I'm an automotive machinist by trade, so drilling a coil plunger is no big deal.

I'm working on restoring a 1979 Stern Trident I picked up at Allentown.... This machine has 4 slingshots.... & I do love a powerful sling... So I decided this would be my test bed. I'm in middle of finishing clear coat job on PF & will be soon ready to start putting it back together, so tonight I took first slingshot coil plunger & drilled it out to .265" ID. It is a "normal" .4375" OD (7/16") Plunger.... Weighed it on my digital cartridge powder reloading scale at 36.5 grams with the fiber link & roll pin left in place before machining.... after the .265" hole, it's at 24.3 grams, so lightened it about 1/3. 12 Grams in the palm of the hand is very noticeable.... I machined the tip flat from the light edge left by drill bit, touched up the edge bevel & polished the OD on the buffer. This plunger was in pretty good condition to begin with, no mushrooming etc.

Now, I imagine that coil stop life is going to be considerably worse, since it now has a hole in the end of the plunger to work against.... but for a game that may see 100 games a year on it? How bad can it be?

Just curious if anyone else has ever messed around with lightening their plungers or arms etc to make their pop bumpers, slings, flippers etc faster/hit harder? I don't think this is something I'd really want to do on the flipper plunger due to how much use they see compared to slings etc, but maybe I'll try a pair in one of my games just to see... plungers & coil stops are cheap, so don't see the harm in trying it once?

Thoughts?

I won't know the results till the game is back together..... I may pull a couple out of working games this weekend & get some before & after results, before I continue on with any more in this Trident.

Drilling from the rear & leaving the tip alone, could certainly be done, but it will reduce my ability to run larger diameter holes, as I don't want to interfere, or mess with the "legs" that stick out for the roll pin on that side....

I had another thought last night about the coil stop end.... I could also drill an even larger diameter hole... & then tap the end & put a pipe plug or set screw in the end & make it 100% flush again, but I would still have the majority of the weight out in the center. I stopped at .265" because I don't want to go any bigger, to leave some material at the end to hit the coil stop... I think .265" is already pushing it... but that's what it took to get 1/3 the weight out.

Also from limited research, & just drilling on this one last night, I believe the majority of these are just Iron.... Iron is much more brittle than steel, & if you get too crazy, they will eventually crack/fall apart I suppose. So I'm not sure I could safely do too much bigger hole.... I may have already went too large, Dunno...

I did the remove some windings trick on the ball shooters on my Space odyssey before & after & didn't notice a huge difference in power.... I would say it was negligible.

Yes, I realize I can get these too powerful & will probably start breaking plastics & I could see some of these slingshot designs actually starting to rip the screws out of the PF etc...

I was just curious to see if anyone has ever done it before.

I had about 10 minutes or less in doing this first plunger, so not really a big deal to me time wise.

I have also seen some of the smaller diameter plungers in some of my games.... I assume that was done for weight, once the coil energizes & the mag field is up, the plunger is instantly centered in the sleeve, so having a plunger smaller OD is not that big of a deal. It will cause little more premature wear on the link end of the plunger it seems from my unscientific observations of the smaller OD ones but.... again, these machines are not on location anymore & seeing 10's of thousands of games a year, so not sure it matters to the average Joe like me...