Benjamin Model 30/30 CO2 Carbine Repeater "Hot Shot"

Building or modifying BB, Airsoft, and Pellet type of guns. Show off your custom designs, find tips and other discussion. Target practice only!
User avatar
Five Star General
Five Star General
Posts: 26101
Joined: Thu Mar 15, 2007 11:28 pm
Has thanked: 477 times
Been thanked: 256 times

Donating Members

Sun Nov 13, 2022 11:16 am

mrfoo wrote:
Sun Nov 13, 2022 1:49 am
I would have left the resistor on a start capacitor, as it will live with charge on it - it's a shock hazard. there's also the risk of more arcing on the centrifugal switch as it switches, which could mean more wear and tear.
I thought it might reduce performance but less wear and tear is good so I put it back and it seems to work just as well. Incidentally there was no charge in the capacitor when I removed it so I suppose it's bleeding the voltage some other way.
My lathe is currently out of action as I stupidly believed the manual for a chinese inverter...
Alas... was it upside down?
hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
Specialist 2
Specialist 2
Posts: 244
Joined: Wed Apr 29, 2015 11:05 am
Has thanked: 65 times
Been thanked: 68 times

Sun Nov 13, 2022 1:42 pm

Haha no.

bought the inverter to run the mill, which is 380v three phase, it turned up and the documentation said it could run 4 separate motors (one at a time, obvs). The mill has a 2 speed dahlander motor, so effectively 2 motors, and the lathe also has a 2 speed dahlander motor, so 2 more motors, 220v three phase for the lathe, that makes 4. So a bit of electrotech later, which involved gutting the rotary phase converter and all of the lathe's control circuitry and we get something that looks like this:


All fine and dandy except that the inverter can, in fact, only be configured for 2 motors, and that as the lathe is 220v, under load it pulls more current than the inverter can supply even though the motor is less powerful than the 2.2kW it's supposed to be able to drive. Bah!
Doc j
Private 3
Private 3
Posts: 52
Joined: Tue May 19, 2020 5:59 am
Has thanked: 12 times
Been thanked: 12 times

Mon Nov 14, 2022 11:49 pm

jackssmirkingrevenge wrote:
Mon Jul 11, 2022 12:27 pm
I definitely have a weakness for old and unusual airguns :)
I like the idea because it comes out of the conceptual "box" and is repeated all the time. There is always a different way to do the same with its pros and cons for sure.
I was unaware of this design when I posted almost the same idea 15 years ago!


It's amazing how many ideas and designs we think are original that have already been thought up and, in this case, actually made and commercialised.

Hi M8,
Thanks for sharing .
Yeah I asked some time back NBB
I Done up this giff .
Another example how it's done .
(I'm a visual learner )
NBB example.gif
Doc j
Private 3
Private 3
Posts: 52
Joined: Tue May 19, 2020 5:59 am
Has thanked: 12 times
Been thanked: 12 times

Wed Dec 07, 2022 6:22 pm

jackssmirkingrevenge wrote:
Mon Nov 07, 2022 11:05 am
Finally found some time to think about this and I'm happier with this design:


Hi Jack ,

Popped up few times with balanced / timed valves .

If I may ,
Had play around few things on GGDT .
Seems 2MS , dwell , or close time .
Good number .

In the instance of designing or going about such a valve .
Considerations and calcs to do so.
Where tuning could be applied .

I see in this rethink , air isn't vented to atmosphere .

The hole in the centre ,
Vented to barrel .

As in the other example you shown .
Explaining difference in dump valve and timed / balanced valve .
(Had a port to valve chamber )
Activated / assisted by hammer.
Rethink design . ( Like the hammer part is valve )

Is it then the port does two things , open and to close the valve .
Assuming by , pressure from valve into barrel .
And is it then a calculation of pressure , volume and length to size = flow rate , thus determines what size I.D. the hole is .

So for example if , the valve volume was 1.01 millilitre .
8mm i.d X 20mm heigh
Using 7 bar pressure as example .
Wanted it to close in 2 ms .
Then 1.01 ml / 1000 is 0.00101mills per milli second.
Aim is fill ) close in 2 ms .
Divide by 2 , would give 0.000505 per ms
Convert that back to per sec X 1000
= O .505
Then convert that to litres per HR .
Using this calculator here :
I get 5.058 mm for that port .
To get that 1.818 ltrs per HR .

Or am I missing the volume of port to be filled as well , then wouldnt 1/2 step .
Take 1ms to fill stem , + 1ms to fill valve chamber .
So it would work out in the wash for 2ms.

Next consideration would be the spring , how that effects .

Is this right way to look at this .
Post Reply