N/A Inertia Assisted, Lightweight Top Hat

[Sqwirl57]

Ok so this is just proof of concept at this point and I won't be able to really test it until tomorrow but I can't imagine it won't show some promise. This idea was borrowed from the Theoben pistons and applied to work in a spring piston gun.

Ok so what we had was a gun with a heavy solid steel 55gr top hat as seen below:

While tuning a new gun for lower power I decided to ditch this top hat for a lightweight top hat. What I did was basically clone the factory top hat and drill out the center. It came to 7g so basically 48g lighter. Huge difference.

I then went to do some testing and thats where it went off the rails a bit. With 8.44gr I was getting pretty decent bounce and the shot cycle just felt off. I switch to a lighter 7gr and the gun felt perfect. Ok, so let's add a bit of weight to the piston and see what happens.

Then I got bored and decided to get creative. What I did was make a new top hat but this time only drilling 3/4 of the way through. I then added a little breather hole at the base of the guide as well as the top (pics below)

These holes are there to prevent a free floating brass weight, turned just slightly loose for the bore of the guide, from getting caught up in a vacuum when the piston fires. The brass weight is roughly 1/2" shorter than the open length of the top hat and weighs 22.5g (over 3x more than the top hat) so it can move back and fourth free. When the piston fires, the brass rod gets sucks to the back of the top and theoretically removes most of its weight/mass from the piston. As the piston bounces off the pocket of air, inertia pulls the brass weight forward and immediately adds 22gr to the piston to fight any bounce. More pics below:

After running a quick test afterwards, the excess bounce is relieved and the gun SEEMS to behave better. I'm off to class now so I can't do any further testing but tomorrow I'll scope it and see how it does. I'm hopeful for some positive results.

 

[markhooper]

sounds like you have a good idea.. will be interesting to see how it works for you..
do you get less recoil with it? or is that spring recoil only.. the reason I am asking is I used to have a rws 34 and 48.. I don't remember any recoil but I used to shoot large caliber powder guns.. now that I've gotten older and disabled I can't even shoulder my 357 lever action with 38s or 410.. so I pretty much just shoot airguns.. only have one spring gun and it's the gamo varmint shotgun 22 smooth bore.. very light gun but I rarely shoot it because after around 10 shots I get sore and it's not fun..
looking forward to hearing about your project
Mark

 

[Mycapt65]

I'm interested in your results. In theory it makes total sense. I want to see if it pans out. I had a RX1 which is a Theoben design. Like many the inertia weight was frozen in place. The gun had a lot of problems. I freed the weight and got it working as designed. There was no change in anything so I removed it and there was no change in anything. I eventually got the rifle working well but I never seen any difference with or without the inertia weight. For those familiar with the design it did have the vent hole.. Somehow some of the earlier ones didn't have vent holes.
Nothing ventured, nothing gained.

 

[cjtamu]

That’s is very trick. Interested to see the test results.

 

[AirShot]

This is a great example of what I have mentioned many times about getting the shot cycle timmed out as part of the tunning proceedure. Different weights in front of the spring will have a big effect on when or how quickly the pellet leaves the barrel and the cushion of air it builds up. I have talked about my own TX that shoots about 905 fps with 8.4 gn pellets yet it is almost as smooth as a 12 ft lb rifle because the shot cycle is perfect as I can make it. Sqwirl57....your experiment is what I have been talking about for years. Your going about it more technical than I ever have, but depending on the gun, spring and pellet weight you will find a sweet spot sooner or later if you have the patience. Can't wait to see your results....

 

[Sqwirl57]

sounds like you have a good idea.. will be interesting to see how it works for you..
do you get less recoil with it? or is that spring recoil only.. the reason I am asking is I used to have a rws 34 and 48.. I don't remember any recoil but I used to shoot large caliber powder guns.. now that I've gotten older and disabled I can't even shoulder my 357 lever action with 38s or 410.. so I pretty much just shoot airguns.. only have one spring gun and it's the gamo varmint shotgun 22 smooth bore.. very light gun but I rarely shoot it because after around 10 shots I get sore and it's not fun..
looking forward to hearing about your project
Mark

I'm hoping it will soften the recoil a bit and add a better shot cycle through a wider range of ammo weights by basically creating "on demand" weight for when the piston starts to get slowed by the pressure in the compression tube. Its all theory for now but I will certainly keep this thread updated as I go.

I'm interested in your results. In theory it makes total sense. I want to see if it pans out. I had a RX1 which is a Theoben design. Like many the inertia weight was frozen in place. The gun had a lot of problems. I freed the weight and got it working as designed. There was no change in anything so I removed it and there was no change in anything. I eventually got the rifle working well but I never seen any difference with or without the inertia weight. For those familiar with the design it did have the vent hole.. Somehow some of the earlier ones didn't have vent holes.
Nothing ventured, nothing gained.

I'm looking forward to testing too. Like you said, "nothing ventured nothing gained" so at the bare minimum I will learn something, which I already did. After only a handful of shots the brass started to deform and get stuck inside the tube. I was afraid that may happen but brass was all I had to work with at the time. What I did was add a small acetal buffer to the mix and after 30 shots now it hasn't been a problem again.

I'm debating (at some point) testing light springs between the brass weight and trigger side of the guide to force the weight back into the piston as soon as the rearward pressure drops to a certain point prior to hitting the pocket of air. I am mostly just talking out loud here but there may be something there... idk.

 

[Mycapt65]

What kind of gun are you doing this on? All of the springers I'm familiar with have a latch rod running through the top hat.

 

[Sqwirl57]

What kind of gun are you doing this on? All of the springers I'm familiar with have a latch rod running through the top hat.

A .177 Cometa Fenix 400 USC that I'm testing Field Target tunes for

 

[dgeesaman]

Interesting!

 

[beerthief]

very interesting ,indeed ! but with pictures and script are you not thinking someone will steal all your work ?

 

[Sqwirl57]

very interesting ,indeed ! but with pictures and script are you not thinking someone will steal all your work ?

Go ahead and steal the idea and build on it with me. Forums used to be about doing stuff like this together.

I woke up this morning wondering now how well a sealed steel top hat semi-filled with mercury would work. Anyone have thoughts? Can a regular Joe buy mercury? Time to find out.

 

[beerthief]

in the 7th grade my science teacher poured a dime size puddle of mercury into the palm of my hand , i then poured said mercury into the next student's hand and so on down till all the students in class had a chance to experience this liquid stuff . Imaging the lawsuits now .














m

 

[bf1956]

in the 7th grade my science teacher poured a dime size puddle of mercury into the palm of my hand , i then poured said mercury into the next student's hand and so on down till all the students in class had a chance to experience this liquid stuff . Imaging the lawsuits now .














m

Never made it to me, got dropped and scattered like lead out of a shot tower.

 

[Mycapt65]

in the 7th grade my science teacher poured a dime size puddle of mercury into the palm of my hand , i then poured said mercury into the next student's hand and so on down till all the students in class had a chance to experience this liquid stuff . Imaging the lawsuits now .














m

Me too. And look were still alive! AMAZING.

 

[Star7]

Probbly a good time to refer to the Cardew book. "The Airgun from Trigger to Target"

 

[Sqwirl57]

Probbly a good time to refer to the Cardew book. "The Airgun from Trigger to Target"

I've been meaning to give that a read through for a couple of years now

 

[markhooper]

Go ahead and steal the idea and build on it with me. Forums used to be about doing stuff like this together.

I woke up this morning wondering now how well a sealed steel top hat semi-filled with mercury would work. Anyone have thoughts? Can a regular Joe buy mercury? Time to find out.

not sure about mercury but dead blow hammers used to have lead in them.. it would have to be in closed in something and I'm thinking it might turn to powder from repeating impact.. how about stainless steel for the top hat insert?? I'd also consider getting the grease that is usually in the spring guide area to lube the insert..
I don't know if you have access to a lathe but another thought is to make a identical one with no vent hole and thread the entrance to the tophat then get the smallest lead shot and fill it about 3/4 full and then screw in a short small setscrew for a plug.. just make sure you leave enough airspace inside for the shot to move around.. this will also tell over time if it turns to powder.. then I suppose a very lightweight oil could be added to lubricate and removed all air.. but then you will need to also use at least blue locktite for a seal on the setscrew plug..

now as far as sharing what you are doing.. yes I don't see any reason not to.. maybe someone will take off with the idea and make a better product for the us, and also there's lots of people who don't have any business touching tools you know the ones who fix something that needs service and then it's trash..
myself I designed a sliding axle hydraulic lowbed rollback trailers for nut harvesters, never patented it.. just too hard for me.. sold them for years.. another big trailer manufacturer got ahold of one of my trailers and reverse engineered it.. but added their own improvements but they had no experience with the hydraulic sliding axle and theirs weighs a 1/3 more than mine and also has problems.. I used to build 4 per year and most were sold about halfway through making..by word of mouth to other neighbors that farmed..most of my sales were just by happy customer telling others and showing off their toys..I made good money since it was my home shop and later on I became disabled and I sold the complete thing to a new small manufacturer.. unfortunately he was young and made improvements that I told him won't hold up.. but he's young and well he will have to deal with replacing parts and keeping customers happy..
there's another guy that was posting on here about a new PCP he designed.. the tequila gun, a pistol and he got harassed so much, I'm not sure he's actually still on this site.. but he is now manufacturing in batches and selling a good product..because he was doing testing and well one nasty comment when he had a piece fail was "" put up or shut up ""
so if we are not into sharing then we all might as well stay away from forums like this.. and actually if we shared and treated each other like we want treated there would be so much less trouble in the world.. I hope this is not too political but it used to be more common..

now I'm very slow and I don't do much each day.. but if you don't have machine tools, I do and I am willing to contribute to this project.. id either need a sample of the top hat or a drawing with good measurements.. id try several ideas and then you can test them.. I mostly do machine work during rainy days in the winter so we are getting there.. PM me if you want any help.. and no I am not interested in taking you idea, just helping come up with something that is better for all..
Mark

 

[Sqwirl57]

not sure about mercury but dead blow hammers used to have lead in them.. it would have to be in closed in something and I'm thinking it might turn to powder from repeating impact.. how about stainless steel for the top hat insert?? I'd also consider getting the grease that is usually in the spring guide area to lube the insert..
I don't know if you have access to a lathe but another thought is to make a identical one with no vent hole and thread the entrance to the tophat then get the smallest lead shot and fill it about 3/4 full and then screw in a short small setscrew for a plug.. just make sure you leave enough airspace inside for the shot to move around.. this will also tell over time if it turns to powder.. then I suppose a very lightweight oil could be added to lubricate and removed all air.. but then you will need to also use at least blue locktite for a seal on the setscrew plug..

now as far as sharing what you are doing.. yes I don't see any reason not to.. maybe someone will take off with the idea and make a better product for the us, and also there's lots of people who don't have any business touching tools you know the ones who fix something that needs service and then it's trash..
myself I designed a sliding axle hydraulic lowbed rollback trailers for nut harvesters, never patented it.. just too hard for me.. sold them for years.. another big trailer manufacturer got ahold of one of my trailers and reverse engineered it.. but added their own improvements but they had no experience with the hydraulic sliding axle and theirs weighs a 1/3 more than mine and also has problems.. I used to build 4 per year and most were sold about halfway through making..by word of mouth to other neighbors that farmed..most of my sales were just by happy customer telling others and showing off their toys..I made good money since it was my home shop and later on I became disabled and I sold the complete thing to a new small manufacturer.. unfortunately he was young and made improvements that I told him won't hold up.. but he's young and well he will have to deal with replacing parts and keeping customers happy..
there's another guy that was posting on here about a new PCP he designed.. the tequila gun, a pistol and he got harassed so much, I'm not sure he's actually still on this site.. but he is now manufacturing in batches and selling a good product..because he was doing testing and well one nasty comment when he had a piece fail was "" put up or shut up ""
so if we are not into sharing then we all might as well stay away from forums like this.. and actually if we shared and treated each other like we want treated there would be so much less trouble in the world.. I hope this is not too political but it used to be more common..

now I'm very slow and I don't do much each day.. but if you don't have machine tools, I do and I am willing to contribute to this project.. id either need a sample of the top hat or a drawing with good measurements.. id try several ideas and then you can test them.. I mostly do machine work during rainy days in the winter so we are getting there.. PM me if you want any help.. and no I am not interested in taking you idea, just helping come up with something that is better for all..
Mark

I appreciate the offer to help! I do have a lathe which I made all of the parts from from the original post on. Its nothing fancy but it gets the job done. Stainless steel is my next step I think. I found a good scrap stainless bolt at work that I can turn down to work perfectly.

 

[Star7]

I was a little surprised that the Cardews did not try the mercury approach. The mercury capsules were quite common in various powder burners to spread the recoil impulse out over time.

 

[Sqwirl57]

I was a little surprised that the Cardews did not try the mercury approach. The mercury capsules were quite common in various powder burners to spread the recoil impulse out over time.

I actually managed to luck into some mercury here so I have it to try. I'm thinking mercury should work very well. Being denser than brass it should be able to throw its weight around a bit better. My only concern is re-sealing the steel top hat to keep it in.