GTA
All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Topic started by: hw77grey on July 23, 2011, 02:14:45 AM
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Hey guys, I have just read the gas ram post and Gene made mention of top hat wieght, somthing I know nothing about. I have polished, lubed, debured, made brass washers and delrin top hat with guide for my phantom. Thing is I was sure I sacraficed a few fps with the top hat made of delrin (720 with 14.3 cphp) but gained a much smoother cycle. I am very pleased with my phantom but would gladly build another if I I could get better results.....
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Hi
Maybe the top hat is a little tight?
In my reading about gas springs the manufacturers recommend supporting the cylinder at the shaft end. The sleeve may be enough support.
This is something I have to try.
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........ made brass washers and delrin top hat with guide for my phantom. Thing is I was sure I sacraficed a few fps with the top hat made of delrin (720 with 14.3 cphp) but gained a much smoother cycle......
HW,
Glad to hear that the cycle smoothed out, ;D but the FPS.... :-\
The top hat that you replaced was metal? If that's true, then you greatly reduced the weight of the piston assembly and it is probably bouncing back before it has a chance to finish compressing the air.
I will let the experts explain the fine details.
But I did a similar thing on an old Chinese gun I had a long time ago. I drilled the piston full of holes to lighten it... thought it would move faster. Boy, was I wrong. FPS was cut in half. What a learning experience (disaster). :'(
Lloyd
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What kind of numbers are others getting with their b-19 platforms? I was under the impression that 15-17 flbs was great out of these ag's? I considered the lack of weight issue, but it seems in this gun the piston and top hat are very heavy, figured they could use a little diet!? Like I said The gun shoots great right now and I would gladly build another if I can get better results!
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HW77,
Maybe some of the folks on the China gate would have specific performance numbers for the B19. But if you say it shoots great, that by itself is a very good thing. ;D
By getting better results, I am guessing you mean getting more FPS while keeping the nice smooth feel?
If you want to experiment some, you might try moving the spring spacer washers (I'm assuming that is the brass washers you made) from the butt end of the spring up to the top hat end and see if the velocity changes. That will put the weight back like a heavier top hat. Might help, might not, but at least you'd know. It's a balancing act, and many things play into it, including pellet weight.
Thanks for telling us about the project.
Lloyd