My Field Target Project

[Sfttailrdr46]

Beautiful work!  I'm very familiar with how much work is involved when you custom build every part of gun, then add some electronics to boot, A trying task to say the least.

I'm curious why CD and not direct drive?  A simple regulated  boost topology could give you the power you need with out the discharce curves, temp and tolerance issues associated with HV caps. You could also control the current in the winding via PWM.  Just thoughts .

Tom

Stop speaking GREEK !!!

Lol ... had too

Thy are not speaking Greek they are speaking "geek" . Former USN ETR Telecom central office switchman and now HVACR manager

[michaelthomas]

Awesome project Michael, I might have to try this someday after seeing your 30yd FT scores.. 

Simply an amazing design, well done!!!

Thanks Joel,

Over time, I think I will post the drawings, schematics, and material list so others can have a go at the build if they feel like it.  I worked from a basic drawing, but some things changed on the fly and I have not gone back to revise them yet.  On an individual part level, there is nothing complicated.  I suppose it's a bit unconventional, but certainly not complicated.  The main part is just a bunch of tubes and threads......all doable on a regular lathe and mill. 

I have also given a little bit of thought of maybe offering some of the more difficult parts for sale if there was any interest.   I don't know.

The electronic part is ridiculously simple..... and so far it has proven itself to be very, very consistent.

I need to finish up mine, first.

Mike

[QVTom]

I need to finish up mine, first.

More appropriate words never spoken 

[michael1969]

Beautiful work!  I'm very familiar with how much work is involved when you custom build every part of gun, then add some electronics to boot, A trying task to say the least.

I'm curious why CD and not direct drive?  A simple regulated  boost topology could give you the power you need with out the discharce curves, temp and tolerance issues associated with HV caps. You could also control the current in the winding via PWM.  Just thoughts .

Tom

Stop speaking GREEK !!!

Lol ... had too

Ναι, μπορο να σας βοηθησο ? (yes,i can help you ?)
Very nice job.

[Tomg]

Hi Lloyd

You talked about Solenoid city and their more powerful solenoids.
I was contemplating building a solenoid striker for a Benjamin Discovery.
I dont know yet the particulars about the hammer spring force on the mechanical version yet, or the strike cycle in ms. (research here I come)
But any help would be appreciated. I was looking at this: s-20-100hp1
Which is 1" dia, might be to big. but they come in .25 increments, so I am sure there is one who nicely would fit inside the Disco tube.

Love your write up, very informative.

T

[michaelthomas]

I'm not Lloyd, but I assumed that you were addressing me.  He probably has a lot of info on this sort of thing too, though.

Yes.....solenoid city seemed to have solenoids with much lower resistances available. (Compared to the 9ohms of the one I used.)

I suppose you would have to find the largest physical size that would fit into your space......then just keep increasing the voltage (or possibly capacitance) until it does what you need.  Lowering resistance is pretty much the same as increasing voltage.

Increasing voltage will shorten lock times, whereas increasing capacitance probably won't.

I don't know exactly what the lock time on my rifle is.  For all practical purposes, it seems instantaneous.  Mathematically, it was somewhere around 2-5ms for the solenoid plunger to do it's work.....but in reality, I don't know.

I can say that when shooting my rifle......it sure doesn't seem slow.

Mike

[QVTom]

Lowering resistance is pretty much the same as increasing voltage.

Slight correction.   The power in the winding goes up by the ^2 of the voltage.  If you double the voltage there is 4 time the power in the solenoid.

Edit:

I had this wrong although the statement is correct as typed but confusing. Thanks to Mike for calling me on it. 

The power (Watts) does go up by the ^2 of the voltage but the motive force is linear.  As you raise the voltage the efficiency goes down the inv^2 of the voltage.  This is why these things are designed to operate at specific voltage.   For the ultra low duty cycle of this application there is a lot of voltage leeway.


Tom

[Tomg]

Thanks guys!

Making the hammer action solenoid powered rather than spring/mechanical seems to me to be an interesting option for tuning the power.

T

[QVTom]

Yes, Mike has done a fantastic job demonstrating this.  The technology is very compelling, especially in the sub 20fpe range where the components and power remains small and easy to manage.

Tom

[Rescue35]

That said, I'm pleased with the barrels.  I really don't know what other options are available, either. 

Mike

Mike,

Nice work. I love to see a project like this come together.

For pellet use there is not many options. Lothar Walter, BSA, FX, and Crosman IIRC. I considered using LW once. After the trials to just receive the PO I decided to use a company that is based in this century.

I have had a lot of luck using Green Mountain. http://gmriflebarrel.com/barrelblanksround

Of course I tend to shoot larger lead and cast my own bullets.

TJ barrel liners is another option. I have not tried any but may in the future.

[joel w]

How many amps/volts for the diode that you used and also the watts of the resistor?

Thanks Michael!

[michaelthomas]

I used a 10a 1KV diode, and a 1/2w 1k resistor.

Mike

[michaelthomas]

Rescue35.....thanks for the GreenMountain link.  Hadn't heard of those, before.  How do they compare for accuracy to the LW?

Mike

[Rescue35]

Rescue35.....thanks for the GreenMountain link.  Hadn't heard of those, before.  How do they compare for accuracy to the LW?

Mike

I've never used a LW. I have used .25, .30, 9mm, .45 and all where excellent. Green Mountain supplies Crosman with the .25 barrels for the Marauder.

[AmBraCol]

Rescue35.....thanks for the GreenMountain link.  Hadn't heard of those, before.  How do they compare for accuracy to the LW?

Mike

I'm not Rescue35, but know folks who swear by the Green Mountain barrels.  As mentioned, Crosman uses them in the 25 Marauder - which has a reputation for a tack driver.  They also supply muzzle loading and other barrels, all of which have a good rep.  A good barrel deserves good fitting and crowning.  A poorly fitted and crowned Lothar Walther will shoot worse than a run of the mill Crosman that is set up properly.  Good quality components with good quality work = good quality shooting.

[Bent]

Moved to: http://www.gatewaytoairguns.org/GTA/index.php?topic=53284.0

Sorry for hijacking..

[willbird]

Couldn't help...... needed to share... 

Woow, haven't worked much in Solidworks before... It's amazing what you can make... to make it look goooood.. 

The gun will be made as a semi auto.
Right now I'm working on how to lock the probe when firing. One solution is to have an arm locking it, but I'm worried about problems and wear..
The power to make the probe go back comes from a piston inside the shroud.

The simple solution is having the probe so heavy and the returnspring so strong that the probe stays in place during the shot. Heavy spring won't do it alone, then the shroudpiston can't give enough force to cycle the probe.

Anyone know how to calculate that?

Data:
2200 psi (max-regulateded)
.25 kaliber
Maximum energy 890fps / 48 grains >> 84FPE
Barrellength 600mm

Don't think I'll get that high, but just to play it safe

If you can get your hands on an ar-15 bolt/carrier it contains a simple way to convert linear motion to rotary motion and thus lock a bolt with a lug or a cross pin, then unlock it when you pull the assembly to the rear.

Hmm maybe AR-180 picture shows the feature better.


Bill

[QVTom]

Very nice design work!  The force is significant at 83 lbs.  It's simply the bolt face area * the  peak operating pressure, SW will give the area easily or use pi*r^2.   Keep us posted.

Rotating bolts are easier designed than executed, they are great if you can create the  geometry and finishes needed to operate smoothly. Other options are over center and falling block mechanisms.  Also consider a pneumatic pin type lock that can be operated by the same source as your bolt, orifice and piston size can be used as timing control.

Tom

[Bent]

Moved to: http://www.gatewaytoairguns.org/GTA/index.php?topic=53284.0

[michaelthomas]

Hi Bent......drawings look nice.

You should probably open your own build thread..... so this one doesn't pile up with a bunch of posts that are unrelated to this particular build.

Mike