Non-adjustable Flat top Piston !

Underdog · October 15, 2016, 03:12:33 AM

Quote from: Davio on October 15, 2016, 01:08:52 AM
What gun model? What caliber?

A 1322 rear cocker. I got mine going to stock specs now, but would like just a little more umph out of it. Don't think that the 6.5 fpe is quite enough.

Gippeto · October 15, 2016, 04:26:32 AM

Quote from: eric on October 15, 2016, 12:45:00 AM
i think they went by the wayside due to cost --- look at their airguns of yesteryear and today ---THEN more real metal and real wood vs NOW plastic and pot metal ..... as well as trying to mass market and keep things at a price point for the average joe (sorry joe)

Agreed.

Flat top reduces head space in the pump, increasing effective compression ratio and potential to make pressure. That they're typically of stouter construction than the plastic fodder adds to that potential.

Swept volume is determined by stroke length and bore size...which are determined by the tube id and the linkages...swept volume remains un changed by flat topping. Most of the efficiency gains with a flat top come from reducing the head space. Getting the faced off portion as close to the sealing o-ring as practical pays dividends....parts do become more susceptible to damage from dropping as the pressure side of the o-ring groove gets thinner. Personally use .030".

Weaker valve spring will lower cracking pressure of the check valve, allowing slightly more of the compressed volume to actually enter the valve.

Opening force is very much a product of valve sealing area and has comparatively little to do with the force provided by any reasonable valve spring.

For example....

.290" sealing diameter equates to 66 lbs force to crack the valve for each 1000psi.

Nice little videos by Sean Pero; Adjustment is covered in part two.

[youtube]https://www.youtube.com/watch?v=5_y-OS5JZAQ]https://www.youtube.com/watch?v=5_y-OS5JZAQ[/url]

[youtube]https://www.youtube.com/watch?v=oMduvk5PVQU]https://www.youtube.com/watch?v=oMduvk5PVQU[/url]

Al

Noah · October 15, 2016, 06:32:45 AM

Well done, Al - a total "sticky" thread if you ask me

I will totally refer to this later when working on my pumpers. Thanks again and have a great weekend

o-townFLA · October 18, 2016, 04:44:11 PM

So here's Davio (Alchemy) non-adjustable setup...

And some chrony numbers from to stock to FTP

STOCK

Created: 10/09/16 10:40 PM
Description: STOCK 10 pumps CPHP
Distance to Chrono(FT): 1.00
Ballistic Coefficient: 1.000
Bullet Weight(gr): 14.30
Temp: 68 °F
BP: 30.05 inHg
Altitude: 0.00
# FPS FT-LBS PF
10 404 5.18 5.78
9 401 5.11 5.73
8 406 5.23 5.81
7 406 5.23 5.81
6 405 5.21 5.79
5 414 5.44 5.92
4 409 5.31 5.85
3 408 5.29 5.83
2 411 5.36 5.88
1 409 5.31 5.85
Average: 407.3 FPS
SD: 3.7 FPS
Min: 401 FPS
Max: 414 FPS
Spread: 13 FPS
True MV: 407 FPS

ALCHEMY

Created: 10/16/16 12:45 PM
Description: FTP 10pump
Distance to Chrono(FT): 1.00
Ballistic Coefficient: 1.000
Bullet Weight(gr): 14.30
Temp: 69 °F
BP: 29.98 inHg
Altitude: 0.00
# FPS FT-LBS PF
10 465 6.87 6.65
9 470 7.02 6.72
8 471 7.05 6.74
7 480 7.32 6.86
6 473 7.11 6.76
5 474 7.14 6.78
4 469 6.99 6.71
3 473 7.11 6.76
2 472 7.08 6.75
1 471 7.05 6.74
Average: 471.8 FPS
SD: 3.9 FPS
Min: 465 FPS
Max: 480 FPS
Spread: 15 FPS
True MV: 472 FPS

mudduck48 · October 18, 2016, 05:49:26 PM

Great review. Looks like it works.

o-townFLA · October 18, 2016, 07:24:52 PM

Granted I added my own little sauce to the mix with a lighter valve spring, trimmed some fat off the valve stem and added Davio's "boss buddy"....

o-townFLA · October 18, 2016, 08:53:13 PM

Here's a 3 pump to 16 pump chrony string... Purged the valve completely at 16 pumps. Just ran out of time to find that max....

Created: 10/16/16 12:24 PM
Description: FTP 3-16
Distance to Chrono(FT): 1.00
Ballistic Coefficient: 1.000
Bullet Weight(gr): 14.30
Temp: 68 °F
BP: 29.99 inHg
Altitude: 0.00
# FPS FT-LBS PF
14 544 9.40 7.78
13 525 8.75 7.51
12 522 8.65 7.46
11 500 7.94 7.15
10 490 7.63 7.01
9 473 7.11 6.76
8 458 6.66 6.55
7 448 6.37 6.41
6 430 5.87 6.15
5 410 5.34 5.86
4 387 4.76 5.53
3 344 3.76 4.92
2 325 3.35 4.65
1 285 2.58 4.08
Average: 438.6 FPS
SD: 79.7 FPS
Min: 285 FPS
Max: 544 FPS
Spread: 259 FPS
True MV: 439 FPS

Underdog · October 19, 2016, 05:12:00 PM

Curious to see the max on that thing now.

Underdog · October 19, 2016, 05:47:42 PM

Quote from: o-townFLA on October 18, 2016, 08:53:13 PM
Here's a 3 pump to 16 pump chrony string... Purged the valve completely at 16 pumps. Just ran out of time to find that max....

Created: 10/16/16 12:24 PM
Description: FTP 3-16
Distance to Chrono(FT): 1.00
Ballistic Coefficient: 1.000
Bullet Weight(gr): 14.30
Temp: 68 °F
BP: 29.99 inHg
Altitude: 0.00
# FPS FT-LBS PF
14 544 9.40 7.78
13 525 8.75 7.51
12 522 8.65 7.46
11 500 7.94 7.15
10 490 7.63 7.01
9 473 7.11 6.76
8 458 6.66 6.55
7 448 6.37 6.41
6 430 5.87 6.15
5 410 5.34 5.86
4 387 4.76 5.53
3 344 3.76 4.92
2 325 3.35 4.65
1 285 2.58 4.08
Average: 438.6 FPS
SD: 79.7 FPS
Min: 285 FPS
Max: 544 FPS
Spread: 259 FPS
True MV: 439 FPS

At your fifteen pump mark you're at 525 FPSwhich is almost 50 FPS faster than my stock 1322 with the same size pellet. Your FPE is also about 1.5 FP higher. Your fifteen pumps still gets better results than even my 20 pumps. At 20 pumpsI get an average of 491.6 FPS, and average of FPE of 7.676. Your FPS is still about 30+ higher, and FPE is 1 FP higher. I'd say it was worth it... I dunno would I get the same results from the flat top and modified valve, but it's certain worth a shot at some point.

Created: 10/01/16 11:43 AM
Description: 1322- 15 pump Cros Destroyer .22
Distance to Chrono(FT): 0.25
Ballistic Coefficient: 1.000
Bullet Weight(gr): 14.30
# FPS FT-LBS PF
5 478 7.26 6.84
4 475 7.17 6.79
3 472 7.08 6.75
2 479 7.29 6.85
1 482 7.38 6.89
Average: 477.2 FPS
SD: 3.8 FPS
Min: 472 FPS
Max: 482 FPS
Spread: 10 FPS
True MV: 477 FPS
---------------------------------------------------------------------
Created: 10/01/16 11:37 AM
Description: 1322- 20 pump Cros Destroyer .22
Distance to Chrono(FT): 0.25
Ballistic Coefficient: 1.000
Bullet Weight(gr): 14.30
# FPS FT-LBS PF
5 498 7.88 7.12
4 494 7.75 7.06
3 487 7.53 6.96
2 489 7.59 6.99
1 490 7.63 7.01
Average: 491.6 FPS
SD: 4.4 FPS
Min: 487 FPS
Max: 498 FPS
Spread: 11 FPS
True MV: 492 FPS

arkmaker † · October 19, 2016, 06:19:58 PM

Those are great numbers

Good job Dave!

o-townFLA · October 19, 2016, 07:40:17 PM

@UNDERDOG

I'd say go for it! As mentioned, I did add a few extras as shaved plunger, lighter valve spring, even polished the bolt and lubed it w/ moly paste.

I ported, angle grinded the transfer port on the valve, stuffed the stock piston myself but cut to many threads off, resulting in a catastrophic failure. One reason why I bought the Alchemy Airwerks piston/flattop setup...

Here my chrony #'s with the self mod

Created: 10/11/16 11:01 PM
Description: mod 10 3-15
Notes 1: Catastrophic Failure On 16th Pump
Distance to Chrono(FT): 1.00
Ballistic Coefficient: 1.000
Bullet Weight(gr): 14.30
Temp: 62 °F
BP: 30.06 inHg
Altitude: 0.00
# FPS FT-LBS 18.24mm
13 530 8.92 7.58
12 523 8.69 7.48
11 507 8.16 7.25
10 496 7.81 7.09
9 481 7.35 6.88
8 464 6.84 6.64
7 452 6.49 6.46
6 429 5.84 6.13
5 409 5.31 5.85
4 381 4.61 5.45
3 354 3.98 5.06
2 317 3.19 4.53
1 283 2.54 4.05
Average: 432.8 FPS
SD: 79.6 FPS
Min: 283 FPS
Max: 530 FPS
Spread: 247 FPS
True MV: 433 FPS

Davio · October 21, 2016, 09:00:41 PM

It is always good to see (and learn from) independent chrony numbers. I'm glad you guys are getting the type of results that I get.

o-townFLA · October 25, 2016, 05:24:05 AM

Quote from: Davio on October 21, 2016, 09:00:41 PM
It is always good to see (and learn from) independent chrony numbers. I'm glad you guys are getting the type of results that I get.

Thanks brother for the stellar work and quick shipment! Now to justify the purchase of your breech... Lol

Could you PM me a price for your breech and explain the benefits of either a steel or aluminum breech