Dual Ball Bearing Bolt Lift Mod

[squirrel_slayer]

been playing with the lathe to get some more time on it and thought i'd show my latest creation. I remember seeing the 38/357 ball bearing bolt lift mod a long while ago so I thought i'd take it to the next level. I decided to machine the BAS down and center drilled it to put a second ball bearing. I even made sure that the whole assembly mic'd out to the same total installed length (in my case my BAS was .8835 long) from the bottom of the rim to the top of the BAS it's back at .8835 so no worries about changing the preload on the firing pin spring. Feels much better now!

http://i1372.photobucket.com/albums/ag357/garred8787/Dual%20BB%20lift%20mod_zpst5aragul.jpg

[Robinhood]

Love it when guys experiment. Now to use your torque wrench and barrel vise to test the result.

[scope eye]

Cool mod

Dean

[sharpshooter]

I tried that once, and found that the single ball bearing works the best. The problem with 2 bearings stacked.....if they are not dead center to each other, the one in the BAS will push the other off center and make the cocking sleeve drag. There is enough clearance for the sleeve to move from side to side inside the bolt body, and it will push it off center like a wedge. One surface needs to be flat.
You can't beat simplicity......

[squirrel_slayer]

I tried that once, and found that the single ball bearing works the best. The problem with 2 bearings stacked.....if they are not dead center to each other, the one in the BAS will push the other off center and make the cocking sleeve drag. There is enough clearance for the sleeve to move from side to side inside the bolt body, and it will push it off center like a wedge. One surface needs to be flat.
You can't beat simplicity......

interesting. is this something you could feel when opening the bolt or did it cause damage? I have some valve lash caps maybe i'll buy another BAS and machine a pocket to put the lash cap in so it has a hardened surface to rotate against and try the tq wrench method to test cocking force.

[BillPa]

interesting. is this something you could feel when opening the bolt or did it cause damage? I have some valve lash caps maybe i'll buy another BAS and machine a pocket to put the lash cap in so it has a hardened surface to rotate against and try the tq wrench method to test cocking force.


Many years ago when play'n with this getup I made a small 'dimple ' in the end of the set screw for the bearing to ride in to keep cocking piece centered. To test it I used Dykem on the the face of the screw . After working the bolt about 20 times the only indication of contact was in the dimple, nothing outside around it.
http://oi45.tinypic.com/fxrpea.jpg
Now when I shorten a BAS for the bearing I do the same thing,
Bill

[J.Baker]

Apparently we're going to have to rehash this old topic yet again.

http://www.savageshooters.com/content.php?126-Understanding-Bolt-Lift-Kits

Trust me, if there was a better way to do it or an option that offered less friction Fred would have already found it. Not only do you have the possible alignment issue Fred mentioned above with this method, but it's also more machine work for zero gain. The pin point of contact on the detent ball is going to be the same size whether it's on a flat surface or on another detent ball, so it's a zero net gain with a possibility of negative side effects.

[RC20]

Love it when guys experiment. Now to use your torque wrench and barrel vise to test the result.

Get data with original and then get results!

[Robinhood]

Get data with original and then get results!

That Idea originally came from the post Jim linked to with Fred doing the work just to make sure the right guy gets credit for the Idea.

[squirrel_slayer]

good read. guess it's back to the drawing board. don't feel like buying a new BAS so i'll just use a lash cap I have and recess it to the correct height. I don't want to jack up the cocking sleeve

[sharpshooter]

The end of the BAS just has to be flat, no dimple is needed. If it's perfectly flat, it provides the minimum contact area and there is nothing to make it walk around.

[squirrel_slayer]

yeah but once I remove the bearing there is a hole and it would be too short so I have a small engine valve lash cap that i'll put in the BAS to fill the void and recess it to the correct depth to get everything back where it's happy.

Thank you for the info.

[Robinhood]

...or a hard flat thin piece steel that sits on top of the cocking piece for the ball in the BAS to ride on..