Posted by: Vampyr on June 07, 2003 at 17:33:39

: No intent to be argumentative here, but what you're saying is quite different from what I've been doing (the 'Ravi method') :) : There seems to be one fundamental difference, and it may be in order to maximize ROF, but it does not make intuitive sense to me. So, unless I misunderstood what you were saying: : It seems that the main difference in our approaches is I set my back block such that it is at rest at the max forward limit of the ram. Thus the back limit of my stroke is where the hammer/mainspring 'bottom out'. This is before the maximum ram extension and so, the bolt's rearward travel is set by the length of the cocking rod. ***The full forward is correct, but it should also be the ram that limits the full rearward travel. Again to avoid beating the sear and jug too much. If you depend on bottoming the main spring for your rearward limit, what happens when you have to adjust your velocity?? you just changed the rearward travel of the bolt. this has the potential for creating loads of headaches. : From your description, and the comment that the bolt position is set by the pump arm, it would seem your goal is to set the rearward travel of the bolt at the maximum extension of the ram (before the hammer/mainspring bottom out). This would result in the back block being at rest prior to the forward limit of the ram. **** ???? I'm missing something here. Use the bumpers in the ram to set the travel. It should run from fully retracted to fully extended. Then the back block is adjusted for proper body gap. : The conventional thinking is that the part of the ram's travel that is the weakest, is at either of it's limits. Thus, setting the back block & cocking rod as I described allow the ram to compress the main spring when the ram is stronger rather than at it's maximum extension (weaker part of the stroke). Your method forces the ram to use it's maximum extension at the very point when it needs the greatest force. On the other end of the stroke, my (Ravi's) method uses the ram's weakest part of the stroke when it is only moving the back block and bolt, rather than compressing a spring. Your method would have the ram doing this at it's strongest. Additionally, by not allowing the ram to reach it's full forward stroke, the back block would slam into the back of the body with each cycle. ****the rams force is linear. It does not vary across it's stroke with perhaps the posibility of a bit of lag if the lines are too restrictive... : It also is interesting to me that you say that having the bolt travel as much as 1/4 inch past the breach is a good thing. I would assume that for the fastest cycling, any unnecessary movement of the back block & bolt should be eliminated. *** This is counter intuitive, but woks by experiment. I tried to explain this, but it's kind of... well, when the ram is only moving the bolt, and not compressing the main spring it can move the fastest. as the spring compresses the velocity reduces. Since the bolt has to mostly clear the feed tube for the ball to drop, and that the bolt still moves much faster than the ball drops, it is more beneficial to allow the ball to drop earlier in the compression of the main spring. Lets imagine that you have a stroke of 2" (way to long, but this is a thought exercise.) In either case, you will compress the main spring say 1/2" we'll say that the bolt move 1/2" in 2ms until it compresses the spring, which takes about 10mS. it takes 65mS for the ball to feed. we will assume that the ball doesn't start to feed untill the tube is fully cleared (bolt has moved 1") from start of feed cycle a standard would take 2+10+65 +4 to close or 81mS (1st 1/2" + spring comression+feed time + 2* 1/2" closing time). (not bad for estimates, that is reasonably close to reality... I'll have to go find my math to see what it actually is...) In our modified version, it would take 4ms+65+8 or 77. (2*1/2" opening time+ ball feed time+ 4* bolt closing time) the rest of the main spring compression occures at the same time the ball is feeding. this also assumes that you don't start the bolt forward 4mS before the ball is fully fed. These numbers are not exact due to assumptions made, but they are reasonably close and we applied the same assumptions to both cases so as long as you are looking at the difference between the two rather than overall.... : So, either I misunderstood some of the things you were saying, or my assumptions about ram power being greatest during the middle of the stroke are incorrect. But, if I didn''t misunderstand, and if I'm correct about the ram stroke, then I'm convinced that the 'Ravi method' is still the best :)

Follow Ups: Thanks for your response... BodyByHostess 10:00:50 06/09/03 (0) Post a Followup Show your name as: DefaultRealnameBothNickname E-Mail address (eg: joeschmoe@aol.com): Show your e-mail address? DefaultYesNo Your Password: Don't have a password? CLICK HERE - Forgot your password? CLICK HERE Subject: Subject:Message: : : No intent to be argumentative here, but what you're saying is quite different from what I've been doing (the 'Ravi method') :) : : There seems to be one fundamental difference, and it may be in order to maximize ROF, but it does not make intuitive sense to me. So, unless I misunderstood what you were saying: : : It seems that the main difference in our approaches is I set my back block such that it is at rest at the max forward limit of the ram. Thus the back limit of my stroke is where the hammer/mainspring 'bottom out'. This is before the maximum ram extension and so, the bolt's rearward travel is set by the length of the cocking rod. : ***The full forward is correct, but it should also be the ram that limits the full rearward travel. Again to avoid beating the sear and jug too much. If you depend on bottoming the main spring for your rearward limit, what happens when you have to adjust your velocity?? you just changed the rearward travel of the bolt. this has the potential for creating loads of headaches. : : From your description, and the comment that the bolt position is set by the pump arm, it would seem your goal is to set the rearward travel of the bolt at the maximum extension of the ram (before the hammer/mainspring bottom out). This would result in the back block being at rest prior to the forward limit of the ram. : **** ???? I'm missing something here. Use the bumpers in the ram to set the travel. It should run from fully retracted to fully extended. Then the back block is adjusted for proper body gap. : : The conventional thinking is that the part of the ram's travel that is the weakest, is at either of it's limits. Thus, setting the back block & cocking rod as I described allow the ram to compress the main spring when the ram is stronger rather than at it's maximum extension (weaker part of the stroke). Your method forces the ram to use it's maximum extension at the very point when it needs the greatest force. On the other end of the stroke, my (Ravi's) method uses the ram's weakest part of the stroke when it is only moving the back block and bolt, rather than compressing a spring. Your method would have the ram doing this at it's strongest. Additionally, by not allowing the ram to reach it's full forward stroke, the back block would slam into the back of the body with each cycle. : ****the rams force is linear. It does not vary across it's stroke with perhaps the posibility of a bit of lag if the lines are too restrictive... : : It also is interesting to me that you say that having the bolt travel as much as 1/4 inch past the breach is a good thing. I would assume that for the fastest cycling, any unnecessary movement of the back block & bolt should be eliminated. : *** This is counter intuitive, but woks by experiment. I tried to explain this, but it's kind of... well, when the ram is only moving the bolt, and not compressing the main spring it can move the fastest. as the spring compresses the velocity reduces. Since the bolt has to mostly clear the feed tube for the ball to drop, and that the bolt still moves much faster than the ball drops, it is more beneficial to allow the ball to drop earlier in the compression of the main spring. : Lets imagine that you have a stroke of 2" (way to long, but this is a thought exercise.) In either case, you will compress the main spring say 1/2" : we'll say that the bolt move 1/2" in 2ms until it compresses the spring, which takes about 10mS. it takes 65mS for the ball to feed. we will assume that the ball doesn't start to feed untill the tube is fully cleared (bolt has moved 1") : from start of feed cycle a standard would take 2+10+65 +4 to close or 81mS (1st 1/2" + spring comression+feed time + 2* 1/2" closing time). (not bad for estimates, that is reasonably close to reality... I'll have to go find my math to see what it actually is...) In our modified version, it would take 4ms+65+8 or 77. (2*1/2" opening time+ ball feed time+ 4* bolt closing time) the rest of the main spring compression occures at the same time the ball is feeding. this also assumes that you don't start the bolt forward 4mS before the ball is fully fed. : These numbers are not exact due to assumptions made, but they are reasonably close and we applied the same assumptions to both cases so as long as you are looking at the difference between the two rather than overall.... : : : So, either I misunderstood some of the things you were saying, or my assumptions about ram power being greatest during the middle of the stroke are incorrect. But, if I didn''t misunderstand, and if I'm correct about the ram stroke, then I'm convinced that the 'Ravi method' is still the best :) [ Follow Ups ] [ Post Followup ] [ WARPIG Tech Talk - Autococker / Minicocker ]