The Importance of Volume - QB 78 vs 79

[lloyd-ss]

Jeez Bob ! 
You must be approaching some sort of airgun efficiency Nirvana.  And at healthy power levels, too. 
Dual power adjuster??? hmmmm. This sounds good!

Lloyd

[Motorhead]

Nice job ! .... After your input on my about to be started QB rework, going to hold off until reading the whole story on these most excellent results !

[TimmyMac1]

That is outstanding performance. It is smart to have the reg output exceed the guns power curve so you can get some more shjots as it falls off the reg.
I would lock everything down and enjoy it. It looks like you have arrived. Congrats!
Don't get greedy. Shoot like that till it stops doing that.

[rsterne]

That would have been good advice, but I had a valve poppet here with a Delrin seal instead of the stock soft seal which I had been using.... It was beautifully done, the poppet pressed apart, the soft seal removed, replaced by a delrin "donut/washer", pressed back together and faced off flat and then polished into the valve seat.... It sealed perfectly, and I expected that with the harder material, and less of a "dent" in the seal surface for the air to flow around, it would give me a slight boost in velocities.... and even if it didn't it would outlast the orignal material which looked about ready to fail with the big groove hammered into it by the high pressures.... I profiled the outside brass part to the exact same shape as my previous one (ie no differences in the flow around the poppet) and reassembled the gun to find I had lost ~20-25 fps.... NO OTHER CHANGES....  

If you are following my "Dual Power Adjuster" thread you will know how it and it's adjustment works.... I had to unscrew the adjuster 1/2 turn (0.025") to get back to the velocity I had previously, with the corresponding loss in shot count (now about 50 per fill).... The efficiency is still 1.10 FPE/CI so I can't really complain, that's great at 32+ FPE.... but I am puzzled by the velocity loss with the Delrin seal.... Have you ever experienced this Tim, or have any idea why it would occur?....

Bob

[TimmyMac1]

The Delrin is hard and when sealing points are the outer edge on a concave arrangement they can slightly bell out at the sealing point and narrow the margin between the valve and head.
You can often see the contact area growin as the seal seats in. The more surface area in contact the morte of the hammer momentum will get sucked up trying to unseat it.
If saling was accomplished with a sharp edged seat as it digs in more you get less lift. It is nice to run small sealing area so the forces require to knock the valve of the seat is less and flow is greater.
The Shot curve you have is more of a plateau and that is very difficult to achieve. If you hange a thing the balace will go away. I'd sroiously leave it alone and carefully take it aart and measure everything.
No point in obsessing over a few feet per second as that is eaily a half pellet width vertical that is not important i the scheme oif things.
What you have happened across is about as good as unregulated or regulated guns ever get.
The Data you showed would satisfy the most discriminating customer as long as the barrel could be worthy of those kinda numbers.
Velocity is a Number that is as pointless to seek as anything you could do. Since that gun will group at the speed it want to let it decide what it likes by focusing on the groups. It'll tell you how fast i wats to go if your paying attention to the CTC.
Whenyouhave a Chrono it is difficult to resist the temptation but one of the Regularorr Gurs Dave Welham always breeched back it dow 15 fps from Max. That was his solution to letting the gun do whatcame natural rather than asking for MAX MAX.
Dave Welham was responsible for some of the best reg designs we ever saw. Naturally he got copied galore and others took the monicker of Mr Reg but Dave was a pioneer and those guys always get my respect.
Copying is easy once you know who does the best work.
My bet is you will not best those numbers but it is always a challenge to prove me wrong.
I made one Regged QB and it was so much work we figured it was not worth doing but a very good deveopment exercise(read wallet exercise). I never did a Production version. At the time there was no place for a $700 Chinese gun.

[rsterne]

Yeah I'm aware of the effect of hammer momentum being sucked up opening a valve.... That's why I was so surprised when the harder Delrin seat lost velocity compared to the super soft (and badly dented) stock seat.... Not much I can do about it, but I'd sure like to understand WHY !?!?!

I'm not one to chase the last few fps, in fact if anything I'm more than willing to give up a few to get better accuracy or more shots per fill.... I was more than pleased when I went from 37 shots at 32.8 FPE to 60 shots at 32.3 FPE and took the efficiency from 0.85 FPE/CI to 1.20 FPE/CI.... Who needs the extra 7 fps when you can give it up to get over 60% more shots....

Bob

[Motorhead]

Do you plan on sharing the finite details ? .... or selling them as work to be done on customers guns by yourself ?

Really have a clean slate new QB sitting here ready to be operated on .... waiting patiently info if your going to it post up ?

Regards,
Scott

Yeah I'm aware of the effect of hammer momentum being sucked up opening a valve.... That's why I was so surprised when the harder Delrin seat lost velocity compared to the super soft (and badly dented) stock seat.... Not much I can do about it, but I'd sure like to understand WHY !?!?!

I'm not one to chase the last few fps, in fact if anything I'm more than willing to give up a few to get better accuracy or more shots per fill.... I was more than pleased when I went from 37 shots at 32.8 FPE to 60 shots at 32.3 FPE and took the efficiency from 0.85 FPE/CI to 1.20 FPE/CI.... Who needs the extra 7 fps when you can give it up to get over 60% more shots....

Bob

[grand-galop]

Hey !!  Do you have any recent développements on this project???  I was wondering what the final product would look like and perform...  Thanks

[Geoff]

tagged in case I ever pick up a QB.

thanks for the info and photos

[rsterne]

The followup to this project is detailed in this thread....  http://www.gatewaytoairguns.org/GTA/index.php?topic=49943.

Bob