Chrony Mods failed,ended up with Chrony Sheild

[PALTIK]

My alpha chrony arrived and I got to work on it immediately to mod it to a "master".
Bought phone cable, phone jacks from 99 cents store.
Opened the chrony up to see how the wires where connected and cut them to a config I thought would work.
After I did everything and it looked good, the thing didn't get signals from the sensors.
I was thinking maybe the cable was too long, so I went ang got a shorter one..didn't work either.
I didn't know if the power supply (9v batt) was low 'coz everything was connected and soldered right.
I even double checked my analysis and tested the circuit with a circuit tester and made sure there where no breaks in the connection.
Alas..to make the story short, I gave up and resoldered everything back the way it was.
I ended up buying LEXAN (GE brand of polycarbonate) which is virtually indestructible and made a chrony sheild instead.
These can be bought in the window section of Home Depot. This is not ordinary acrylic as this is polycarbonate that protective shop glasses are made of..or the canopy of a fighter plane.
It was a good thing though 'coz after I made my prototype, I accidentally shot the chrony twice with a 0.22 pellet with 540+ fps at almost point blank range!
I was aiming at the target and didn't notice that the barrel was already lowered to the level of the chrony.
You can see what happened to the prototype and the pellet it stoppped included in the pix!
Anyway, here are pix..first of the schematic of how I modded the alpha chrony to be a "master"...then of the lexan polycarbonate chrony sheild I ended up with.
I already have plans to make a remote as I also already bought an audio cable fron the 99 cents store to be cut up and connected to a momentary switch from radioshack.
The sheild can be unscrewed off when done shooting and reattached when needed. The hole drilled into the lexan is a bit smaller than the screw so that the screw tapped into it as it was screwed on.

talk about a stitch in time, thanks for reminding me to make something similar for mine, i got some 20mm thick acrylic, would never have thought a piece of polycarbonate that thin would stop a pellet, live and learn, live and learn, good idea putting a sheet on the inside to protect against rebounds, what did you use to bend the plastic, a heat gun ??

fin

[PALTIK]

A lot of recommendations say use a heat gun, but unfortunately i don't have those. Others recommend a torch but that is a little tricky as you might burn the plastic and make a mess of it.
Still ohters recommend heating it in an oven. I did the next best thing and heated it in an oven toaster.
Did it on trial and error basis as you can see from my prototype that the bend wasn't so sharp and the plycarbonate bacame wavy..it didn't look nice but it still did the job.
My 2nd try was still with the oven toaster but I only heated the part (I drew a pencil line) where it was to be bent. This time, I never placed the whole lexan in the toaster oven to sit.
I just held the part (to be bent) near the red hot heating coil up the top of the oven toaster. That did the job as it only heated and softened the strip where I needed to bend it..then out it went and I bent it against the table (use gloves of course). That made a better bend.
Maybe the third time I do it, it would look factory made..lol!
I just used a regular hacksaw to cut the lexan to my specs. The bending part was the hard part and was a learning experience.
Hope this helps!
By the way, I don't know about ordinary acylic sheet though as it isn't as tough as polycarbonate which is used for safety glasses.
Anyway,if it's what you have, it is better than none. Here is another pic as to what happend to somebody elses chrony when it got hit by shrapnel from real bullets I think.
This pix was a post from a guy in australia.

[TCups]

Excellent work on the shielding.  Whenever I set up to chrony, I am putting the pistol or rifle on a rest centered over the chrony'e sensors.  Haven't been brave enough to chrony anywhere other than near the muzzle (ie, shooting downrange at the chrony to check the velocity at the point of impact).  

Very likely the sensors are photoelectric  and give a very low voltage signal. Likely the signal is a very slight drop in voltage due to the "shadow" effect of the pellet.  If so, then the amplification circuitry in the module with the digital display.  Greater distances over a paired wire would, even with relatively low resistance, probably cause it to not work properly.  Just a guess, but seems logical

Think you might leave the amp circuitry in the chrony box and wire a parallel 2nd display LCD as a remote readout?

[TCups]

PS:  Gerry

With your newly acquired skills at bending polycarbonate sheets, given it's strength, you might be able to bend the stuff into a pellet trap with left and right side lips folded over to hold the target, epoxy on a top and bottom panel and perhaps get by with using a whole lot less of the duct seal putty needed for the wood models.  Much lighter too.   Pellet trap lite?

[Progun]

Great ingenuity Gerry. Don't feel bad though about shooting your chrony. At least yours survived. Two of mine didn't.I now place a brick in front of mine when shooting at distance,

[leadbottom]

Thanks for the tip about bending the polycarbonate.  I might try that for my new Chrony if I don't have to buy a big piece of the plastic.

[cliffspot]

How about putting just a poly face around the wood trap's facing so it won't get eaten up by stray shots! Save your trap, make it last longer!

[PALTIK]

You can get the small ploycarbonate sheet good for 2 sheilds and an extra rectagular faceplate for the front and back. It only costs about $3 plus.
I think its about 8 inches by 10 inches. It is already pre-cut by the window section of Home Depot. There is a bigger sheet though and it costs around twice as much.

[PALTIK]

That actually seems logical so I also thought of leaving the battery sensor side and not plugged to the Chrony CPU but I didn't have the patience to cut the battery leads also and relocate it.
As you can see, the chrony has 3 wire leads. Two of them are for the power supply and the third one is for the sensor feedback.
If I only had another chrony to copy it on, then I would have been able to analyze it better..plus I wasn't using alkaline batteries that was suggested.
I just used the heavy duty battery. I also thought that if a "master" chrony or a relocated chrony head unit needed that much power compared to what I have now which works on..let's say not full powered batts, then I would rather have this set-up that saves me on battery and just make a sheild instead.
It was pretty interesting though how I cut everything up and restoored it again as if nothing happened!
The modded chrony even looked good with the attached phone jacks and phone cord!
As for the remote LCD, that could work but then again, it would defeat the purpose of modding this thing at a very low cost compared as to just buying one that is already in a "master" set-up. Another LCD panel would cost more than just getting phone jacks and phone cable from the 99 store.
Anyway,thanks for all the input! If ever I get to see a master chrony up close and am able to take apart one...I would probably mod my alpha chrony again!

[PALTIK]

Good idea Tom but I'm still really am a novice at bending this and wouldn't like to make it into a business..LOL.
You've got great ideas as with helping out Tim with his wooden box target handles! Every once in a while it is really better to listen to others to get the best ideas.
Sometines we get too engrossed with what we are doing that we forget that there are other ways to skin a cat..or a squirrel..lol!

[PALTIK]

That's a very..very good idea! Specially after toasting two of them..LOL!
The prototype was actually touching the face of the chrony up the top edge that's why when the pellet hit, it actually also made a dent near the FU button.
It's a good thing the polycarbonate absorbed most of the shock.
That is also why the next sheild I made (as can be seen from the pix) are now about an half inch or more away from the front panel. I'm thinking that this time the sheild would spring forward then deflect the pellet upwards instead of leaning on the panel and absorbing the impact thereby also transfering some of force onto the front panel..'coz believe me, that thing got dented even with the lexan sheilding it!