Consider Walther Free Pistol Electronic Boards

[Bob LeDoux]

Sometime back I had the chance to fire a Walther free pistol. They are now considered orphans, especially because of the electronic trigger units.

I’ve seen the stories about owners who’ve had the units burn out, making the pistol an expensive club. Is anyone rebuilding or producing a replacement board for these guns? The reason I’m asking is because the board doesn’t appear to be very complex. It shouldn’t be that difficult or expensive to create a replacement board. Would this be a worthwhile endeavor, for the good of the sport?

[Richard H]

There is one very smart gentlemen who I believe has made one. Hopefully he will appear on here and tell us about it.

There is also rumours that Walther is gonig to make a new free pistol with an electronic trigger. It would be nice if they made the electronics so that they could be retrofited into the older pistols, it might take the bad taste out of the mouths of some whom have been bitten.

My Walther FP works great. I was also told that some of the problems were due to the screw that holds on the battery cover, if it is tightened too much it pushes on a compent on the circuit board and has damged a few. Others I know who have working models have just shaved a little off that screw, I just make sure that I don't tighten it too much as it is only holding in the battery.

[Bob LeDoux]

I posted my query in two places. Here, at Target Talk, and on the Yahoo Free Pistol group.

I was hoping the broader membership at Target Talk would respond to my idea. But it appears pretty quiet here.

There is interest at the smaller Yahoo group, which also deserves support.

http://sports.groups.yahoo.com/group/Free_Pistol/

[marcialvs]

this model and brand of free pistol i think is the worst in market is better a water tube to shot, electronic system inside is only a nasty cheaper circuit, i so angry whit this pistol that i have it under ground in my back garden in a shoe`s box. i realy recomend to serious shoters of free pistol TOZ 35 or MC55, world havent something better than this free pistols, isn`t it ?.

[Bob LeDoux]

I don't think anyone argues they were not a good free pistol. They are a piece of history and I feel they deserve to be kept in shooting condition.

That said, I'm not going to personally go out and spend $400 to buy one just so I can turn it into an expensive project. I thought there might be enough interest that a few people could coordinate efforts to design an alternate electronic board.

I guess I was wrong.

[jrmcdaniel]

While not quite ready to replace the board for someone, I have created a capacitive discharge version of a Crosman 2240 with off-the-shelf components so it should be easy to create a board to replace that in the Walther.

My approach was to use a scrounged disposable camera flash power supply for the high voltage. (Didn't Walther just use a high-voltage battery? The circuit diagram for the original Walther was in their patent and was quite simple.) The SCR to do the actual firing is the only other active part although one might want to add some voltage regulation.

If someone wants to loan me a Walther for an indefinite period or sell me a broken one at a reasonable price, it might be an interesting project.

Best,

Joe

[Bob LeDoux]

Can you share the patent drawing or a patent number with us? Was it patented in the USA? If so, a patent number is sufficient. (I don't know how I could have missed the patent as I publish a book of US airgun patents.)

The camera strobe uses a transformer to generate about 300 volts needed to fire the strobe tube. I don't think the Walther pistol uses this mechanism. It might use a diode double or tripler to generate something less than 30 volts from its 9 volt battery. If you pursue your project be careful about exceeding the breakdown voltage of the firing coil.

The newer Morini pistols utilize some type of voltage generator to create 15 to 20 volts from 3 volts. The older Morini pistols used a 15 volt battery.

Thanks for your information.

[jrmcdaniel]

US PO numbers are 4,134,223 and 4,009,536.

I have used standard magnet wire at 250 - 300 volts in my coils. The regulator I mention could be set to limit the charge on the capacitor. The usual power supply for the disposable cameras is a single AA battery.

Best,

Joe

[Bob LeDoux]

I stand corrected.

The earlier patent does indeed specify a high voltage 300 volt firing pulse so a firing system based on a strobe flash makes sense.

I'd like to see more details about the Crossman firing system you developed.

[jrmcdaniel]

Right now, it is a "board" gun (literally, disassembled 2240 with barrel/receiver mounted on a wood board).

I replaced the spring and bolt with a hand-wound solenoid and rod (with a return spring). A simple circuit consisting of the power supply, capacitor, scr, and a switch for the trigger will fire the gun. Most of the circuitry in the patent is the power supply. This can be replaced (as I did) with a photoflash power supply.

The power supply from a disposable camera is really very small and can be constructed with only one integrated circuit, flyback transformer, plus a few passive components. Only problem is getting the components in small quantities hence the disposable camera route. The capacitor for the usual camera is too small for firing an airgun but might be more than enough to fire a .22 firing pin.

Anyone attempting to play similar games be warned -- 300 volts will give you a good jolt! Opening these cameras can be dangerous as the capacitors often have a charge!

Best,

Joe