GTA
All Springer/NP/PCP Air Gun Discussion General => European/Asian Air Gun Gates => German AirGun Gate => Topic started by: xyon on March 17, 2017, 07:12:16 AM
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Hi,
My Diana 52 has a fair amount of spring twang when firing. I dissembled it when I first got it and polished the spring ends and the washer between the spring and the guide. I also added a Teflon sleeve inside the piston. The sleeve didn't seem to make much difference. So now I'm making a Delrin/Acetal spring guide. I plan to copy the factory one but increase the diameter slightly to make a snug fit in the spring.
One question I have is the piston center rod is 10.00mm and hole in the guide is 10.7mm, should I try for a closer fit here? or does it not matter?
Any tips on machining the guide when the tube wall thickness will be only 2mm? I'm a bit worried about the rigidity of this while turning or drilling.
Last question, should I add a washer on the piston end of the spring?
Thanks
Bruce
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When I made mine, I figured anything that tightened things up was an improvement. Tight does not mean rubbing (in this case) but I did make the hole in the spring guide slightly smaller than the one that came from the factory. It is quite possible that this hole is made larger in order for the stem on the piston to find its way into the latch on the trigger mechanism too. This I can't say for sure
The outer diameter of the guide is another story. When the spring compresses, its inside diameter expands and that part of the guide can be made snug to the spring.
I have been successful in adding sleeves to the inside of the piston on other guns. I even put one in the piston of my TX200 with a Vortek kit in it. There is play between the sleeve that is in the kit and the piston, that my .004" inch sleeve took up, without dragging. I bought a steel shim kit off Amazon that has numerous thicknesses in it to choose from.
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Hi Springrrrr,
Thanks for the reply. I just finished making my guide tonight. I'll post a pic and dimensions in case it's of use to anyone. Have to install it tomorrow and check I can still cock the gun since I made it as long as possible.
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Hi Springrrrr,
Thanks for the reply. I just finished making my guide tonight. I'll post a pic and dimensions in case it's of use to anyone. Have to install it tomorrow and check I can still cock the gun since I made it as long as possible.
Kia Ora!
I'm on a trip and I don't have access to all my notes but anyway, dimensions are specific to materials and makers of springs.
Lately I've been preferring moly infused nylon for guides. I drill the center of the guide with a letter Z drill.
The length of the guide should take into account if you are going to use a TopHat or not.
I use a 0.002" interference fit at the REAR of the guide and a 0 to 0.001" slip fit on front.
In relation to the inside of the spring dimension taken at a point where you can measure without the interference of the closing forged loop.
Again, sorry for the late reply.
Héctor Medina
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Hi Héctor,
I had time to test my new guide briefly. It was my first attempt at making one. I think I may have made it a bit too tight. More line 0.02" than 0.002" :-[ It was quite tight to get the spring on for assembly. I was thinking I can always make it smaller, but I'm not sure if I will be able to get the guide back out from the spring in one piece.
This is the change different in fps before and after.
RWS Super Field 15.9 gr
Factory guide = 825 fps (24.0 fpe)
Custom guide = 770 fps (20.9 fpe)
Is there any problem using it like this (other than the loss of power)? I wondered if the spring might be putting too much pulling force on the guide and break it.
The up side is the twang is gone, it must be quieter now as I can here the pellet flying through the air now :D, where as before that was mostly masked by the twang.
I haven't had time to test for fps spread and accuracy yet.
Cheers
Bruce
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Hi Héctor,
I had time to test my new guide briefly. It was my first attempt at making one. I think I may have made it a bit too tight. More line 0.02" than 0.002" :-[ It was quite tight to get the spring on for assembly. I was thinking I can always make it smaller, but I'm not sure if I will be able to get the guide back out from the spring in one piece.
This is the change different in fps before and after.
RWS Super Field 15.9 gr
Factory guide = 825 fps (24.0 fpe)
Custom guide = 770 fps (20.9 fpe)
Is there any problem using it like this (other than the loss of power)? I wondered if the spring might be putting too much pulling force on the guide and break it.
The up side is the twang is gone, it must be quieter now as I can here the pellet flying through the air now :D, where as before that was mostly masked by the twang.
I haven't had time to test for fps spread and accuracy yet.
Cheers
Bruce
Kia Ora!
The plastic base/washer may be pulled too much and if it breaks you run the risk of getting little bits and pieces of plastic in the trigger mechanism.
Not good.
Turn a wooden dowel to a slip fit to the inside of the spring and use that to push out the guide.
If you run your lathe at very high speed and use very sharp tools with acute edge angles you can rework the guide.
If not, you can also sand it.
HTH
Héctor