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12-17-2013, 10:59 AM | #1651 | ||
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Remember a few pages ago when we were discussing all those math formulas and you said you didn't know what they mean. That was OK then, but now it's very relevant. Those same formulas explain the error and use of correction factors. At this point, I think swamp2 could explain the errors in your measurements better than I can. But it should definitely be confidence inspiring that I followed the manufacturer's instructions, calculated the correct correction factor, made the measurements, and they corroborated the ball anvil micrometer. Unfortunately, this just isn't the right way to measure bearings. |
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12-17-2013, 11:03 AM | #1652 | |
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http://bmwfans.info/parts-catalog/11247838088 http://bmwfans.info/parts-catalog/11247838089 |
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12-17-2013, 11:04 AM | #1653 |
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12-17-2013, 11:16 AM | #1654 | |
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I don't think you are understanding the method. It doesn't matter at all about the angle of the clock when used as a comparator. 45 degrees, 10 degrees, skewed to the side, they would all give exactly the same result when zero'd out on a 2mm slip compared to a 2mm item. Swamp will understand |
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12-17-2013, 11:28 AM | #1655 | |
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Snow if this turned out to be better, I would use it going forward. It just wasn't better for me. |
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12-17-2013, 11:34 AM | #1656 | |
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12-17-2013, 11:37 AM | #1657 | |
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Lay the 2mm slip down and zero the clock. Now remove the slip and replace with another identical 2mm slip (Or the same slip again). What would the clock now read if the lever was at 45 degrees? What would the clock read if the lever was at 5 degrees? I think you are introducing an error that's not there to start with. You should take the raw indicator reading, not calc for trig Last edited by Yellow Snow; 12-17-2013 at 11:50 AM.. |
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12-17-2013, 12:39 PM | #1658 |
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This has really turned into a pissing contest.
If anyone wants to say a ball mic that has a .00005 accuracy is not good enough to measure a bearing you are on crack plain and simple.
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12-17-2013, 01:59 PM | #1659 | |
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If members are sending $600 over for a service, they should expect accuracy. |
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12-17-2013, 02:05 PM | #1660 |
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I believe one must use correction factors for these indicators, it is not about the zero point those will indeed always be zero for any angle of the tip. The point is about CHANGES from the zero. Sorry YS - you're totally wrong here.
Think about this simple thought experiment - use the device totally incorrectly and place the tip vertically (or very close to vertical). What happens when you change from a cal gage to an item of a different height - the darn tip does not move! In this configuration it can only respond to fore/aft changes (or left right, however you are situated). Obviously though when level the tip does move and this is how the darn thing is designed and calibrated. Thus there is a simple trigonometric correction factor, not for the zeros but for the relative movement from zero. rg's measurements showing the very close correspondence between two techniques only with the correction factor also completely validates the method. Also, YS - do you have the audacity to claim the manufacturer of the equipment themselves don't understand how to get accurate measurements from it? I think it is time to close down the measurement debate technique. YS - you "won" the it's OK to measure at the bearing saddle with a ball indicator, rg has won the correction factor for tip angle. It turns out they are related! Let's move on to some real understanding.
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12-17-2013, 02:08 PM | #1661 | |
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Furthermore, when it really comes down to it the only measurement that matters is what it is torqued in the rod. Measuring bearing thickness is all fine and dandy but in the end it is a worthless number. The only two numbers that matter are clearance and crush. That my friend is fact and not up for debate.
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Last edited by kawasaki00; 12-17-2013 at 02:15 PM.. |
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12-17-2013, 02:50 PM | #1662 | |
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From the pics it looks like RG is zeroing the clock on the table, then laying a .050" slip under the clock so the clock is doing the measurement. (not a comparison test) In this instance, trig certainly needs to be considered. It's easy to see how a total .050" rotation of the dial will be skewed by cosin errors. That is what the manufacturer is referring to and I fully agree If he put zero'd onto a .050" slip, them measured another .050" item, the result would be absolutely accurate irrespective of lever angle. The dial would be in exactly the same position with no dial movement taking place. (A direct comparison test) How can you trig it out when the lever shows .0000" movement? Can you see what I mean? I guarantee I am correct. |
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12-17-2013, 03:22 PM | #1663 | |
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My method is 100% accurate whichever side of the globe you are on and whoever is doing the measurement. I have already stated that I agree with rod and journal sizes which are very easy to measure and consistent. They all appear to be within .0001" which is excellent. The only differences that crop up are when the bearings are fitted in the rods. That's why it's important to do a thorough size check of the bearing before it's fitted. Then again afterwards when it's torqued in the rod for a full diameter check. This will denote whether any problems are due to bad assembly or inconsistent bearings. Some of the assembled sizes are varying by .0005" which can only be down to these two points. |
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12-17-2013, 10:40 PM | #1664 | ||
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I think we can all agree that all that really matters is the measurement after installation so maybe we can focus on this.
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12-17-2013, 11:33 PM | #1665 |
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For those who are looking for some general info on bearings and tolerances:
http://kingbearings.com/files/Geomet...e_Bearings.pdf |
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12-17-2013, 11:59 PM | #1666 | |
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That's a great read. Thanks for posting the link. It gives me an idea to add a link to the front page of the thread. Let's see if I can remember to do it. |
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12-18-2013, 11:21 AM | #1667 |
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I have no idea how I overlooked this thread, but man I have some serious reading and studying to do.
Before I embark on this crazy rod bearing journey, I just wanted to thank everyone who was involved in collating and putting together all this information. Time to take out those reading glasses!
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12-19-2013, 12:27 AM | #1668 |
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Quick update:
Here's where we are so far. I've got the virgin 702/703 bearings, and already measured the thicknesses. You've seen a preview of the results here. I will post a full write up a little later when I also measure the clearances. There's still no word on the 088/089 bearings. It looks like 088 bearings are gone for good. But I've got a lead on a set of virgin 089 bearings. They are very pricey @ $40 per! I waiting to hear the final word on if I can get these bearings. Since 088's appear to be completely gone, I will have to make a set of my own using the best 088's that I have. I've got about 5 different bearing sets to chose from, and I'll be looking for the eight best I can find. I also have a near 13/16ths set of Calico coated bearings that I plan to measure at the same time. Don't ask me why 1.5 cylinders of shells were missing when they sent to me. I've already measured the thicknesses of these and will post the results later as well. So far, here's the expenses. 8 x 702 bearings @ 17.86 ea = $142.88 8 x 703 bearings @ 24.49 ea = $195.92 32 x Rod Bolts @ 5.51 ea = $176.32 9% sales tax = $46.36 Total = $561.48 Total donations: $950.00 Balance: $388.52 If the 089 bearings come through, then this will eat up all but $40 of the donations. If the 089 bearings fall through, then I'll do the same as 088's to make up the best set I can get. If that's the case, then I will refund the balance to everybody proportionally based on how much they gave. Friday I will pick up the crankshafts I left at Van Dyne. The next big data dump will come after Christmas. If anything of note comes up, I will update the thread. |
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12-19-2013, 05:40 AM | #1669 |
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Its going to be interesting to see what results you get...according to the person I've been exchanging emails with at BMW the rod bearing revision in 2011 was a materials change only and the "the dimensions remained the same".
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12-19-2013, 06:11 AM | #1670 | ||
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You can see a difference in overlay colour between old and new type bearings along with sizes here in RG's post from P1 Quote:
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12-19-2013, 09:47 AM | #1671 | ||
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Page-1 will soon be updated official thickness measurements for 702/703 bearings. For now, you can assume they are already posted here: http://www.m3post.com/forums/showpos...postcount=1643 |
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