Hi there! First of all..; make sure your QB can handle the pressures safely. Valves..; Yes it will probably work out just fine building it like you describe it. You dont need to glue it to the valve pin; a press fit is good enough, there is no force pulling the valvehead off. Make sure the valve sealing surface is somewhere between .5-1mm wide.. The easiest way to get a valve to seal is to pressureize it fast - like when you fill from a scuba bottle or buddy, a hand pump is harder. Out of words
Sounds like you are on the right track! When I have difficulties to get a valve to seal @ first fill I try to "shock fill" from a scuba bottle or similar. At times it's almost impossible to get new valves to seal when filling from empty by means of a hand pump. Once pressurized and fired a couple of times i seldom get any problems from my valves... But as you said I normally go with higher pressure. Out of letters!
@pyronathanpyro One thing to consider is that the force needed to knock open the valve is proportional to the "sealed area".. it takes a lot more hammer force to open a valve head with a diam of 10mm compared to a valve head of 5 or 6mm.. Also a bigger diam valve stem means higher weight and more inertia. If you go with a stem of 4,5mm you have enough material to fit an oring, and if you use a 4,5-5mm inlet in the valve body and turn down the stem just behind the head it's good for +900fps...
Another great vid. Love Acetal. My local supplier only has it in white :-(. Nylon only in black. Reminds me that BSA made a bad batch of Hornet internals with Nylon instead of Acetal. Swelled in rain & rifle stopped working ;-) Nylon horrid to machine by comparison. I need to grind a tool like yours for plastics - insert tooling not sharp enough for precision cuts on plastics.
yes a return spring can be fitted to the end that the hammer hits this will make the airflow around the valve head much better because there is no restriction from the spring and spring retainer
nice :) im gona build one on a friends lathe also your english well you trying to speak english i actualy understood you better than a fluent english speaker thx man also you know the end of the pin that gets hit by the hammer well how to i stop air leaking out of that bit when it opens ? can i put an o ring on the valve pin its self just past the exit hole ? inside the plastic housing so it stays air tight ? cheers
I still haven't managed to wear out a valve! I have put somewhere around 10000 pellets through the barrel of one of my guns - and it has a flat face valve, brass body, delrin head. Somehow i find the all metal pin/soft valve body design easier to make and easier to get to seal at first fill, so most of my recent guns have that type of valve. Cheers
yes it will and it will be better because it will not require a end cap to hold the spring in place i often use that method on my high powered airguns for .22 i use a 6.5 hole and a 7 mm valve the 6.5 hole leads to a 5mm hole in the breach this set up will give me over 50ftlbs
Great job your English is very clear. I have a question do you no what a safe wall thickness is for brass and or aluminum on a 3000 psi fill on a pcp valve. Looking to mod some valve similar to the one you built. I also would of never thought delron would be able to with stand high pressure air id be scared of the valve shattering just because I have seen it happen when being turned in a machine. ✌️👍👌 Thanks for your time and reply.
Probably... i think it's a bit on the soft side, but if nylon is what you have; go for it! It will most likely give a good seal, but it might not give as long service as a acetal valve body before it needs replacing. thanks
Since im shooting at a regulated 100 bar and you i guess 200? I think a heavier valve spring would do the trick. Already put a heavier one in it and is leaking just a little bit right now. I polished the seat and valve too, just put some polish paste on the valve head and turn it for a while in the valve seat so they kinda wear in to eachother. Im supprised how little pressure 100 bar gives on the valve. Since im still using the same hammer spring. I hope it will seal good when i shoot a while
Thank you for the kind words! Yes; the transferport hole is drilled in the top of the valve body.. I prefer to mount the valvebody in the receiver and then drill the transfer port through the receiver ( the metal part...) and in to the valve body in one set up.. That ensures that everything lines up perfectly.. Then it's just to drill a hole in "the bottom" of the barrel to let the air enter the barrel. A bit short of space to write here! do you get the idea? Thanks
You do nice work, I enjoyed watching you. I too have an interest in building my own pcp airguns, both rifle and pistol, you have inspired me. I couldn't tell the accent, where are you from, I'm in the States, Oklahoma to be precise. Keep the great videos coming!!
@pyronathanpyro Thanks! You are right aboutthe air loss past the valve stem during fireing.. I have built valves both with and with out o-ring on the stem. The valve built in this video has a stem diam of 2,3mm so it doesn't have enough material to cut a o-ring groove in. As long as you get a good fit between valve stem and the hole the air loss is acceptable. thanks
Emco and huvema is just all chinese too. For old machines, you still pay for technology from 20 to 70 like years ago. And cheaper no brand machines are almost just as wel at this time. And that old machines most of the time need a lot of maintnence and parts are often not much available. And yes i need to cut threads with it.
Ok thank you, it is leaking less and less. Hopefully after one more fill its 100% seated. Otherwise i try to make the sealing surface smaller or valve spring heavyer. If they all fail i go with the flat head valve. What dimentions did you use for it? Like a 6mm valve head and 5mm hole so 0.5mm sealing surface? Thanks again for sharing your information and skills with us !!
Hi! I'm not sure i get the idea.. that should work,,, but you need toadd some extra lenght to the valve pin, un-supported lenght that is.. will make the valve pin more prone to bending, and also adding extra weight = more inertia.. Valve should be keept as light as possible IMHO.. Thanks
Man, you sure have built some great PCP airguns compared to others!! I just have a question; from the last video, the diagram shows what you call an 'air transfer port'. Is that drilled in to the top of this knock-open valve? And how does that connect to the slider/loading chamber? Thanks!!
@alehax27 ahh right i sea how would i go about sealing it or shoudl it be ok ? if not i can make a deeper groove and oil it so it doesnt create friction
Sorry to hear that your valves are leaking! Anyway, is there any signs of wear on either valve head or seat? The fact that the valve seals for 50 shots indicates that the desing is right, but the parts (material) might not be up to the strains. What type of aluminium did you cut the seat from? Debris in your system? Bent valve pin? Width of sealing surface? I have never tried 45deg, but have use flat valve seats - should work, just cut the sealing surface to proper width. thanks
Yes, those machine tools are mine... I have actually five lathes... none of the has cost me more than 300usd, but a lot of hours to rebuild. I prefer to buy good quality second hand machines instead of new low end machines. My oldest lathe is something like 70 y/o..
Hello, Will it seal good? I just got a cheap QB78 CO2 gun. Converting it to PCP. But i want a other valve too couse original has too much distriction. If i cut the brass valve head in a 60* angle with an inside tool and make a like pvc kind of valve head wich later can be glued to a steel rod. Wil i it seal if both cut to 60*? i first have to save up for a lathe anyway haha. Nick
I have no experience of Huvema machines.. IMHO it's (almost..) always better to go for an good quality second hand machine... Try to get one with as much tooling as possible.. Do you need to be able to cut threads? Otherwise a plain turning Schaublin 102 is good... even if it's 70 years old. Myford, Boxford, South Bend are good solid machines that last a couple of lifetimes if properly taken care of. Used quality machines is sometimes cheaper than new low quality stuff.
@wyz2285 When i use a valve return spring i make a recess for it in the air tube/bottle adaptor that screws into the same hole that the valve body sits in... Hope you understand what i mean... would be a lot easier if i had a picture of it! Thanks
Generally speaking; the lower the pressure, the thinner the sealing surface of the valve/seat in order to get it to seal properly. Most of the time a width of .5 - .75mm works well. If you gun is safe for higher pressures you might try some shots at lets say 200bar, just to slam the valve shut more forcefully and thereby aid in forming the valve and seat to match each other. Don't spend your money on valves - buy tools instead! Take care
Hey, I am modding an QB79 CO2 gun to HPA and made this valve too. With the body from aluminium and the halve head of delrin. But i can't get it sealed well. First try was with a 7,5mm hole and second valve with a 6mm hole. First one worked well but after like 50 shots it starterd leaking. Second valve didn't make 10 shots. Should i try a 45 degree angle on the valve and seat or just a flat valve face and a rim in the body of the valve? I don't know.
By the way. do the Delrin valve/valvehead wear out quick if made correct without burrs or whatever? Which ones wear out quicker, your dezign here or the oposite hard body soft valve head? Did you ever had to replace a valve due to wear? TY!
Sealing surface is to your recommendations around 0.75mm. What did you mean by cut the sealing surface to proper width? You mean that the valve head is like 1mm bigger then the hole? Or what do you recommend for that? And that is just flat valve head to flat body right? I can't emagine how that could seal haha but i will try everything to make a good valve. I refuse to order a 60 euro valve ( 35 shipping + 21% dutch taxes) from US and have a crappy chinese valve.
Do you get good duration of the seat using delrin? When the metal valve slams closed, does it damage the seat over time or is it lasting a very long time?
Thanks for your comment Antonio! I still haven't worn out a valve seat. Some of my guns have fired several thousands of pellets, so the valve seat seems to be pretty though. Thanks/Ola
Its getting EU screws on the pressure tube, Not chinese shit. Airtube is rated for like 2000/2500 PSI. It will be running at a regulated pressure of loke a 1000 PSI. For the valve head i think im going for PTFE rod. Yes no need to glue indeed, in my head i had drilled it all the way trough haha but littlebit past half way would be ok, pressure and spring will keep it in place. I would like to get a Emco Maximat Mentor 10 lathe:) Or just a Huvema lathe.... Its cheaper Emco is like 1600E :(
and how the valve moves in the original position? Does it have a spring that is pushed back to its original position to seal the high pressure air?a retainer spring? plss reply plss.
richard cero Hi! A spring..; well.. yes, and no.. A valve can be used witout a return spring since the high pressure air acts as a very powerful return spring and forces the valve shut after fireing your gun. A return spring is good to have if you are about to fill a pressure vessel that is emty. The return spring will then keep the valve shut until the pressure in the vessel is high enough to take care of that. I suggest that you go for a valve with a return spring to start out with. best regards
I am making my onw pcp airgun,(tunning a springer actually) here in brasil, is a ofensive price, to buy a air gun, hatsan bt65 elite 2000 reais(us 670). e brasil same gun 7000.0 reais,fucking insane man...i guess you are from switzerland...home of fx impact ....cheers...
