Silent Cat Spring Buzz Question

[Tim40189]

Posted this on the Gamo Gate and thought I might post it here in the shop also in an effort to get somemore input.  Ed, Gene, Bob any ideas without compromising your trade secrets.  I really do appreciate all of the help garnered from this mutual brotherhood of addicts as we are.  Just finished a tune on my brother-in-laws Silent Cat .177 cal. The dang thing ain't so silent!! Had a major spring buzz before tuning it, the buzz is less now but still evident. Used 2 different springs in the gun and Delrin spring guide with brass top hat. Can't figure out where the buzz is coming from or how to eliminate it. Anybody got any ideas? I'm stumped at this time. Ordered a new Tarantula spring from JM and will try it that is the only thing that I can think of to do next. Used an E-3650 spring first and then back to a stock Gamo spring, and getting the same results. Any ideas would be appreciated. Thanks.

Tim

Thanks everyone for the input. Here's where I'm at now. The tar on the spring is heavier than on any other gun I have tuned. The stock is the cut away synthetic with the pistol grip and not much there to stuff. The delrin guides have both been fitted to the springs, and the brass top hat is isolated from the piston by a nylatron disc. The Whispers and Big Cats that I have tuned have not had this type of buzz even stock. The bad thing about this gun is at 35 yards it shoots 3/4" groups with the buzz. I would keep it as is if it were my gun, but the main thing he was complaining about was the buzz. I even thought about buttoning the piston to try and eliminate it. Don't know if this would make a difference though.  I have 2 Big Cats and 2 Whispers myself and none of them have been a problem to tune and they shoot like dreams. This one has me puzzled. I'm still looking for the miracle guys. Thanks again.

Tim

[shadow]

The spring is not fitted to the guide properly and with that you will still get a slight buzz. Ed

[Tim40189]

Thanks Ed.  I'll make a new guide when the Taranula spring comes in from JM and try to improve it.  I'll post the results then and thanks again.
Tim

[CharlieDaTuna]

Ed is right Tim. If the tophat and spring guide is properly fitted, there will be no buzzing of the spring and you won't need a heavy application ofthe heavy tar. In fact, if the innards are properly tuned, you need very little tar. When I was tuning for a specific outcome, I didn't even use any lube on the spring and there would be no twang or vibration. I would only lube the spring during the final assembly.

Also, someone made a comment about using Delrin for the tophat. That is usually not a very good idea (unless the power plant is designed without a tophat) and can cause  early spring reaction as the compression ratio comes up  and the diesel effect takes place lowering performance and power and quite often producing a dramatic velocity spread.

[shady816]

thank you for clearing up the delrin problem for the tophat charlie and tim i'm sorry for the delrin idea tim i never looked at it from a compression side of it i was thinking more on the vibration and isolation stand point so i've learned somthing.

[Tim40189]

Thanks Bob for the information.  I'm still going to wait on the Tarantula spring from JM and will be much more careful fitting the spring guide and top hat on that combination.  You guys are the best here and it's great to be in the company of such helpful folks.  Thanks again everyone for the help.

Tim

[CharlieDaTuna]

Thanks Tim and if I might make a suggestion…. HINT….TOP SECRET….keep this to yourself  

I would consider holding the weight of the tophat to between 47 and 54 grams regardless of what metal is being used. Staying on the light side will reduce the impact somewhat when the piston hits home. Regardless of the face/hat size or length, the weight can be decreased/adjusted by drilling a 3/8 inch hole in the face side, weighing it as you go.

Also, use a thin polished stainless steel washer between the face of the hat and the bottom of the piston lubed with moly. This will greatly reduce the spring torque and decrease the spring cocking resistance during the cocking cycle and make for smoother cocking. Do not use Delrin.

None is really needed at the opposite (spring guide) end and little or nothing is actually gained by using one there. Just be sure that the spring end is polished and there are no sharp cutoff edges.

 

[Tim40189]

Thanks Bob for the help.  You guys are the best, no doubt.  Great to have friends like everyone here when you get high centered on a fix.  Thanks to everyone here.  Bob you have performed a great service to the fraternity of Air Guners over the years by starting and maintaining this forum giving us all a place to share and seek information as well as brag a little when we do have a success story to share.  Seems those success stories don't mean near as much to our wives as they do fellow air gunners, I just can't imagine why that is.  lol  Congratulations to you and the "Staff" of the Gateway to Air Guns forum and God Bless.

Tim

[Tim40189]

Bob,

You and Ed pegged it straight away.  I refitted the guide in the gun and got rid of the spring buzz completly!!!  Now she is smooth, quite, and accurate.  I'm gonna put a few more rounds thru the gun before I give it back to my brother in law.  The 5 shot groups at 20 yards are still at appx. 1/2" or slightly more, trying to be consistantly accurate with a 15 mph cross wind is a little tough.   Thanks again for the help with this one gentlemen.  

Tim