Air Rifle Top Hats

[Gene_SC]

I had a request to post something on Top Hats. First let me explain what a Top Hat is for those who are not into working or playing with all the parts that make up a springer air rifle.. A Top Hat is not used in some model's of air rifles and let me explain why. TheTop Hat sits on the end of the main spring. It slides in the spring generally about one inch and has a head that is the same size as the O/D of spring. Generally it's weight determines the force it has moving forward when the sear is released and piston fly's forward. The heavier the top hat the harsher the recoil will be. Also the spring size is fingered into the equation as well. Now for the other models that do not use top hats. In a sense the weight of the piston plays a big part as well. For instance the RWS and Chines Clones use a heavier piston with a sear engagement pin welded to the inside of the piston. It protrudes out the back of piston which lets the trigger engage and lock and hold the sear end when cocked. This gives the piston allot of weight with the extra steel. On the ones that use Top Hats, they are generally light weight pistons and have a slot in the rear for seer engagement.

It has taken CDT many years of tuning to develop the best weight to spring ration for the Top Hats that he as made for tuning. There is a science behind all this and it is mathematics...:) Overthe last couple years or so since I have been working with CDT we have noticed that Gamo and others have changed there top hats making them heavy, then lighter and so on. But what the bottom line is that if you can match the proper weight of Top Hat with main springs you can end up with an excellently balance power plant.

Maybe CDT can add to this or even correct any errors I have made. We will not give out any secret formulas or dimension but you can see from what I have said that the weight of Top Hats play big part in the performance of a springer.

Below is a Top Hat From a Gamo typical power plant.

[mcmi]

Thanks Gene. I'd like to see one if possible and I'm going to watch this thread for input.

I appreciate the attention and explanation.

[shadow]

Thanks buddy for posting this for our fellow member's who are working their way through all the airgun lingo or part's and their function. Also great knowledge for the one's thinking about tunes and it's always a plus when you know what's going on inside of the shooter. Ed

[CharlieDaTuna]

Gene has pretty much included most of the majors. Perhaps I can add a little for what it's worth.

Many people refer to the tophat as the front guide and in a sense that is what it is. But its function goes far beyond just being a “front guide” and is much more critical. Being that it is not fixed as is the spring guide, it does need to be fitted both to the spring ID as well as the inside diameter of the piston and seat for those that use a tophat. This aids in not only reducing vibration and harmonics but to also assist in reducing spring cant. As Gene stated, the weight as well as the length and fit plays an important part in the firing cycle.

The setup for the tophat is determined by the spring used including the coil count and the wire diameter, the tophat spring seat in relation to the seating of the spring, the coil bind of the spring and in relationship to amount of compression space before the tophat and the spring guide come in contact with each other.  It’s a good idea to allow a minimum of .125 thousandths overall room to eliminate and cocking issues now or in the future. The one other thing that should be figured into the calculation of the tophat is the thrust washer if one is to be used. It can be a bit complex and unless you have some knowledge and experience and a little math background, it will probably require a little trial and error before you get it right.

The tophat can be machined to utilize the additional room normally considered for spacing up the spring. It can be made of either brass or steel and Delrin is not a good choice in my opinion as it does take a tremendous amount of abuse at a high impact unlike the rear spring guide.
 
In the pictures that Gene has posted, you can see that the tophat is made of very soft steel and is pretty rough and worn away on the surface. When disassembled, you will find small particles of the tophat (as well as other particles) imbedded into the seal surfaces. This latest Gamo tophat pictured is the one used in most of the Gamo’s and has been lightened to try to help reduce spring twang, the harshness of the firing cycle and to reduce detonation, which is in part due to seal damage caused during assembly.  When tuned correctly with a good spring, fitted spring guide, and a fitted tophat, you can add the additional desired weight with no adverse effect and yet vastly improve the firing cycle and consistency.

Guess I’ve said enough. Anymore and Gene will be cutting my tongue out and feeding it to Fritz and Missy

[CharlieDaTuna]

A custom tophat should be considered when tuning any gun if the tools and equipment along with the knowledge and skills needed are available. Any gun that uses a tophat  (as well as some that don't from the factory) will usually benefit from a custom tophat.

[Jaymo]

Excellent info from Gene and Bob. My question is, what caused that cool honeycomb pattern to the shadow?

[Gene_SC]

Just my funky camera Jeremy..:)

[daved]

Hey, Gene, you gonna let me pick your brain a little when I start working on my 440?  Shot it a little last night, typical Gamo, but it's a near 15 fpe rifle right now.  I want to get it down in the 10-12 fpe range, smooth, consistent, and easy on the recoil.  We all know what a wimp I am when it comes to recoil, that's why I went over to the Dark Side :-).  Later.

Dave

[Gene_SC]

First off Dave, you picked a good model to work with. A proper tune and the right pellet will give you what you want. I have a brand new Gamo 440 which I have not even shot yet just sitting here. I was gonna do the same thing to mine when I ever get around to it.

[hyounker]

I'm in the middle of tuning my old B3.  I am manufacturing a new spring guide (thanks for the pics Kev!) and have been thinking of a tophat.  Then I found this thread.

In playing with this rifle, I added a 1/2" bronze spacer in the piston with the factory spring, but didn't see any difference between having this spacer in the piston or on the spring guide.  Not much weight, but not sure what is needed and didn't want to add too much weight.  

I am sort of copying what I read about from Kev here:

http://www.gatewaytoairguns.com/airguns/forums/thread-view.asp?tid=12857&mid=101882#M101882

I noticed he didn't mention a tophat.

Can anybody recommend a good starting point or should I leave the tophat out of the B3?  Not trying to pry away any hard-earned secrets, so if i'm asking to much, just say so.

Thanks for any help.

[gamo2hammerli]

Thanks Gene and Charlie for the explanations on the Top Hat.....I just opened up my Sierra Pro to get the spring replaced....now I know what a top hat is.