I had SOOOO many inquiries on LWCV's yesterday/last night I thought I'd create a CV Workshop...
as there is so much misinformation/disinformation out there regarding CV's I think the only way to approach these is by information sharing. |
CV Workshop Part 2... In this pic you can see where a new "real deal" Audi/Lobro driveshaft CV has been ultrasonically cleaned and then lightened. Some CV's may exhibit additional "light" machining marks where they are also trued for axial/radial run-out at the same time. This will show up as "shiney" machined areas on the front face, OD or rear face and in some cases, all 3. Goal is "0" indicated run-out on all 3 outer surfaces. Inner race is also checked for run-out and concentricity and corrected if present. Any run-out found in these parts will have a dramatic affect on CV dynamic balance and operating smoothness once assembled. Zero imbalance/run-out is the "only" accepted number at 10k RPMs on driveshaft CV's and 6k RPM's on all inner axle CV's after modification. If it can't be achieved by shuffling balls and/or roating inner race 120/240 degrees within the outer race then it's done assembling parts for least imbalance then chamfering bolt holes for absolute balance. No brand new CV to-date has been found by me that outta-the-box will sustain even 800 RPMs without "some" measureable imbalance! And no CV is placed on the balance machine that is not a fully assembled unit! This particular CV and its opposite-end driveshaft counter-part as well as all 4 inner axle CV's being sold in this set will also be cryogenically treated like those on my car per customers request (add $15 per CV) after machining/balancing. All stock ball bearings provided with new CV's are discarded and replaced with new "Grade 10" ball bearings being ultra-close tolerance balls with enhanced sphericity compared to the Grade 8 balls provided by Lobro and are weighed down to .001 grains (not grams) so they don't contribute to or exaggerate any existing imbalance once assembled. And don't think for a minute that ball bearings all weigh the same or are even close!! Out of 100 balls I'll usually get 3 identical tho slightly varying weight "sets" of about 30-31 balls per set which I can usually assemble 14-15 CV's with a matched ball set weighing EXACTLY the same in all 6 CVB races. 2-3 ball bearings out of every 100 will inevitably be tossed as they simply cannot be weight-matched to each other or any other balls in the box. I will also substitute the ball cages in EVERY CV I'm not satisfied with as that relates to it's fit to ball bearings and/or the CV inner/outer races with special cages made specifically for me and this application. If stock cage is a good, tight fit it stays. If I'm unhappy with it for any reason it goes in the trash. Too much time/effort put into these to compromise on a $20 part! Lightening these involves the use of radiused corners to prevent stress risers forming. Weight removed is 12ozs (3/4lb) per 100mm inner axle/driveshaft and 14ozs per 108mm inner axle CV's. This makes the larger 108mm inner axle CV's after conversion to LWMS specs even lighter than a stock 100mm inner axle CV! I try to keep 12 driveshaft CV's lightened and on the relieving bench for 10 days to two weeks before further work so that they take their "set" and relieve themselves. This means they will shrink over a period of 4-5 days and I like to afford them some additional time. I can't do anything to them as it relates to lapping, honing and polishing until "after" they've taken a measureable and confirmed .xxxx" amount of stress relief. More on this as this CV is massaged into LWMSCV spec. |
CV Workshop Part 3... Today I'll show the final pre-assembly results of the same driveshaft CV I showed in Part 2. I finished both driveshaft CV's yesterday which took a little over 6 hours to complete. And thats about as much work as I can tolerate on this phase of CV work in a single day. And I don't want to do that more than once/twice a week as it's very meticulous and fidgety work requiring a LOT of focus and mental concentration. Additionally it's messy work as these are lapped/honed either completely submerged in coolant or when out of the "soup" under a heavy spray of coolant. Without cooling these during lapping/honing they get hotter-n-hell and will warp/deform a thousandth or so if one area gets hotter than another. Only way to retain the concentrricty of the part attained during lightening and run-out correction is to insure nothing gets above room temperature during this process. You can see a slight tinge of "rosiness" in this CV that wasn't there in yesterday's pic. That comes from the final polishing using jeweler's rouge on the bearing races. That stuff is nigh-on impossible to remove completely with standard brush & soap cleaning but every individual component of a blue-printed/lapped, honed and polished CV is ultrasonically cleaned a 2nd time before assembly and balancing. Ultrasonic cleaning scrubs the rouge right off (something about a quadrillion tiny bubbles with an internal temp approaching 1,000* F that rouge just can't quite stand up to ;-). They are then moved to a "clean-room" (a spare bedroom) where I keep all my ultra-close tolerance precision measuring tools. There they are wiped down with a lint-free cloth, then assembled with a weight-matched set of upgraded "Grade 10" ball bearings and again blown out with compressed air. They are then checked for "rough" imbalance on a cone balance ball setup to sub-1 minute of absolute "static" balance, measured from both sides. They are disassembled/reassembled as many times as necessary to accomplish this. Once sub-1 minute angle of imbalance is attained on my table-top machine they are blown out again, this time with filtered/clean air and dipped in WD-40 and placed in individual plastic "zip-lok" type bags and stored until 6 or more at a time can be taken to the balancing shop as my special pricing for balancing is based on "6 per visit" and I retain the special balance jig arbors I CNC'd specifically for this purpose that is required for balancing. The 3 jig arbors used for the 3 different LWMSCV's have been balanced to 14k RPM's with no measureable imbalance so they cannot influence or affect CV balancing. And each balancing arbor is re-checked and corrected if necessary for zero imbalance at 14k RPM's every visit to the balance shop before any CV is balanced on it. This pic also shows the stock inner ball cage on left and one of my ultra-close tolerance custom ball cages I have made for all LWMSCV's I offer on right in pic. If I can't get the perfect fit I'm looking for with the stock ball cage then I opt to use a custom cage in that LWMSCV. Most stock cages are perfectly acceptable/useable. Maybe 1 out of 18-22 is slightly too large/loose-fitting for my liking and doesnt provide the ultimate fit I'm seeking. When that happens I go for one of the known-good ones. And even then I "sometimes" get a loose one tho the ratio is closer to 1 in 60 that are slightly "outta whack" and subsequently tossed. The polishing on the ball bearing races is purpose-designed to have the same micron finish as the Grade 10 ball bearings used. I want a true "glass-on-glass" surface bearing/race relationship. If my polish is rougher or less than the ball micron finish then all I've achieved is "glass-on-cinder block" and that just doesn't suit me or the goal with these. After balancing they are put back in their plastic bag and returned home or sent out for cryogenic treatment if specified then home where they undergo a 3rd ultrasonic cleaning while fully assembled "as-balanced", blown out again with filtered/clean air, dipped in WD-40 again and placed in a new zip-lock where they remain until shipped to end-user. It is of utmost importance they remain sealed/unopened until such time as they are to be packed with grease by the purchaser and that too should be done in a meticulously clean area so as to avoid contamination of grease and CV. And they should NEVER be dis-assembled without all 9 parts, ie; outer ring, inner race, ball cage and all 6 balls be marked/indexed so they can be re-assembled EXACTLY as they were before disassembly. If you don't you've ruined a LOT of work and wasted a ton of money. Sure it's smoother than a stock CV but it's a LOT less CV than you paid for!! The pic above would appear that the outer mass internal ball races have a lesser/duller polish than that on the internal splined race. It's an illusion caused by the outer ring internal races picking up the reflection of the silver table underneath. Both are mirror-finish pieces. They are identical in every way... they have to be as they are lapped, honed and polished while mated together and both have the same Rockwell C-hardness of 60-62. Funny thing in all this is that the outer weight removal area has no polishing done to it.. just touched with a ScotchBrite pad before turning the lathe off removing from it's centering fixture. Thats EXACTLY how it come off the lathe after lightening. It's nowhere near as polished as it looks in this pic and the races are a LOT more polished than they appear. Capturing polished mirror surfaces in pics is tricky bidness! |