I'm looking for an alternative to needle roller bearings (springers)

[greenwayjames]

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[vobster]

Well, thats says it all really. Welcome to my ignore list.

[slugger]

getting back on track for a minute..... anyone got that link or egay number for a thrust baering to fit the tx ? or am i going to have to strip mine to measure-up

[Shed tuner]

getting back on track for a minute..... anyone got that link or egay number for a thrust baering to fit the tx ? or am i going to have to strip mine to measure-up

the ones I mentioned earlier are perfect for the rear.

But all mine are custom or mk2 guides, as the mk3 spring is rubbish...

[slugger]

mines a titan with delrin guide.... be ok you rekkon jon ?

[Shed tuner]

mines a titan with delrin guide.... be ok you rekkon jon ?

Lazy bugger -strip it and measure !

[slugger]

ok ok

[NickG]

You can always grind the bores out with a dremel. The fit isn't important

[Shed tuner]

You can always grind the bores out with a dremel. The fit isn't important

sure, but there's isn't that much clearance before you get to the retaining voids for the rollers...

[Loki_79]

I have also given in and ordered some thrust bearings to experiment myself, but the one thing that I cannot undertand is how the spring can cause a rifle with a fixed piston to rotate in the first place. In fact, the only way to generate rotational in the rifle, is for the piston to rotate in the opposite direction.

Imagine that the spring is welded at either end (i.e. to the rifle and to the piston).
(A) If the piston was free to rotate, then the angular momentum of the rifle due to rotation in one direction would be equal to the angular momentum of the piston due to rotation in the other direction, since angular momentum must be conserved.
(B) If the piston was fixed (e.g. via the cocking slot), then there is no way either can rotate relative to each other, and any rotational force generated by compressing or releasing the spring would remain stored in the spring.

So if anything, it is the rifle with a freely rotating piston that should exhibit the most rotation. Have I missed something??

[vobster]

So, I fitted one to the rear guide of my main 97, and it wouldnt cock. Odd. I'd removed exactly the same thickness of preload washer as well, so it was not coil bound.
I tried it in my second 97, also no cock....

I suspect the bearing and washers are too wide, and are stopping the piston going as far back as it should.

[bigtoe01]

So, I fitted one to the rear guide of my main 97, and it wouldn't cock. Odd. I'd removed exactly the same thickness of preload washer as well, so it was not coil bound.
I tried it in my second 97, also no cock....

I suspect the bearing and washers are too wide, and are stopping the piston going as far back as it should.

yep the skirt on the piston will be fouling on the bearing. You can either chuck up the rear trigger block and machine the face where the spring guide sits back a bit or remove some off the very hard skirt on the piston.

If you only need a 1mm or less I would take a look at the trigger block, just watch going to far as the main stock retaining bolt hole is close and you need plenty of meat there remember if it has to come off the piston its best to spin the piston in a lathe and using a mini grinder just take off the surface of the steel what you are going to machine off, they are case hardened so once the case is removed the rest will come off easy and dress up nice.

[bigtoe01]

Another way round it is to set the rear guide into the trigger block like the LGV, then the bearing will sit against the trigger block and give you more room.

[vobster]

Thanks Tony, I'll take a mm or two from the rear of the piston and see what happens

[bigtoe01]

In between nursing a sick puppy and work today I grabbed 15 mins and fitted the bearing, no ideas on power though as this has added 2mm preload so I may have to back things off unless its now sat at 11.3 up from bang on 11.

Fired 8 shots only with 3 before to just get a feel....it does feel more back and no twist even with a rotating piston. The guides in my gun are exact, tight but not too tight both rear and the top hat, my feeling was it would not work so well with the guide this tight...but it does look to have made a slight difference.

Will push 100+ thru it on thursday now and report back then