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Crank build for racing engine
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<blockquote data-quote="oexing" data-source="post: 179226" data-attributes="member: 1493"><p>The needle bearing at left side is allright, but the one at right side is NOT suitable for big ends. Think centrifugal forces on the cage when the bearing is positioned at half stroke on a crank. So it gets flung out onto its o.d. floating in the big end bush on oil film. For that it needs substantial faces for floating and the right sort is not designed for this condition. So only take the left type, it was the biggest type 40-48-20mm INA ever made for big ends and many years out of production and no stock so I wonder where it is from. Possibly some dealer had INA make a number of them on order or found a supplier in China who was supplier for INA at that time. I got a number from there as well, so can still supply a bunch of these , the size 35-42-20 too, at € 10.- each. The smaller type was used in the NL ABSAF Goldstar engines when I looked a while ago.</p><p> The most important factor for high mileage is clean oil, not the dimension of the bearing. Even when the bearing looks quite strong, any grit entering the track will produce micro defects in the suface and this will go on and destroy the tracks in time, see the Ducati 860 crank pin and conrod with about 30 000km only from new. Well, was a trip to New Delhi and back plus a trip to IOM and not quite back.</p><p> When looking at the Maugham cranks I am a bit underwhelmed seeing they still do pressed in mainshafts and bolted up crank pins. Not acceptable for me 30 years ago when I started a lengthy reconstruction of my B Raps, only one piece crank webs plus 30 mm mainshafts would do. My lady Helga spent many hours on that long gone big old lathe roughing out the blocks of ht steel rounds. Yes, finishing them was awkward, unlike a dead simple job with Maughams cranks. But roughing out for integral mainshafts is just some time on a CNC lathe , no troubles with all other details with pressed in mainshafts. Same goes for crank pin nuts - no thanks, pressed in 40 mm pins will only do for me. Even when having my jig for pressing up the lot I got 0,06mm runout that I was unable to true up by hitting the lot with big steel hammer and alu plate on the crank - it would not shift. Well, obviously I am too weak at my age now for hitting it hard enough, the press did it finally. But in fact the heat treated high tensile crank webs plus 40 mm pressed in pin will never ever twist the tiniest amount.</p><p> A while ago when in another long telephone conversation with Brufnut we agreed a conical press fit for mainshaft or crankpin with 1 degree taper or half that would be desirable. So you could put shafts in by half the depth , no cocked fault from this then. Next stage you put that under the hydraulic press for final position and good press fit as calculated. Certainly you´d have to machine tapers on mainshafts plus flywheels but no big drama I think.</p><p></p><p> Vic</p><p></p><p>YT t.s. runout check clip, metric indicator !! :</p><p><a href="https://www.youtube.com/watch?v=A_h9m3NWmr4" target="_blank">crank check</a></p><p></p><p>drive side check:</p><p><a href="https://www.youtube.com/watch?v=1p1gYmmwr1s" target="_blank">d.s. runout check</a></p><p></p><p></p><p>[ATTACH=full]62109[/ATTACH]</p><p></p><p>[ATTACH=full]62111[/ATTACH]</p><p></p><p>[ATTACH=full]62112[/ATTACH][ATTACH=full]62110[/ATTACH]</p></blockquote><p></p>
[QUOTE="oexing, post: 179226, member: 1493"] The needle bearing at left side is allright, but the one at right side is NOT suitable for big ends. Think centrifugal forces on the cage when the bearing is positioned at half stroke on a crank. So it gets flung out onto its o.d. floating in the big end bush on oil film. For that it needs substantial faces for floating and the right sort is not designed for this condition. So only take the left type, it was the biggest type 40-48-20mm INA ever made for big ends and many years out of production and no stock so I wonder where it is from. Possibly some dealer had INA make a number of them on order or found a supplier in China who was supplier for INA at that time. I got a number from there as well, so can still supply a bunch of these , the size 35-42-20 too, at € 10.- each. The smaller type was used in the NL ABSAF Goldstar engines when I looked a while ago. The most important factor for high mileage is clean oil, not the dimension of the bearing. Even when the bearing looks quite strong, any grit entering the track will produce micro defects in the suface and this will go on and destroy the tracks in time, see the Ducati 860 crank pin and conrod with about 30 000km only from new. Well, was a trip to New Delhi and back plus a trip to IOM and not quite back. When looking at the Maugham cranks I am a bit underwhelmed seeing they still do pressed in mainshafts and bolted up crank pins. Not acceptable for me 30 years ago when I started a lengthy reconstruction of my B Raps, only one piece crank webs plus 30 mm mainshafts would do. My lady Helga spent many hours on that long gone big old lathe roughing out the blocks of ht steel rounds. Yes, finishing them was awkward, unlike a dead simple job with Maughams cranks. But roughing out for integral mainshafts is just some time on a CNC lathe , no troubles with all other details with pressed in mainshafts. Same goes for crank pin nuts - no thanks, pressed in 40 mm pins will only do for me. Even when having my jig for pressing up the lot I got 0,06mm runout that I was unable to true up by hitting the lot with big steel hammer and alu plate on the crank - it would not shift. Well, obviously I am too weak at my age now for hitting it hard enough, the press did it finally. But in fact the heat treated high tensile crank webs plus 40 mm pressed in pin will never ever twist the tiniest amount. A while ago when in another long telephone conversation with Brufnut we agreed a conical press fit for mainshaft or crankpin with 1 degree taper or half that would be desirable. So you could put shafts in by half the depth , no cocked fault from this then. Next stage you put that under the hydraulic press for final position and good press fit as calculated. Certainly you´d have to machine tapers on mainshafts plus flywheels but no big drama I think. Vic YT t.s. runout check clip, metric indicator !! : [URL='https://www.youtube.com/watch?v=A_h9m3NWmr4']crank check[/URL] drive side check: [URL='https://www.youtube.com/watch?v=1p1gYmmwr1s']d.s. runout check[/URL] [ATTACH type="full" alt="P1050474.JPG"]62109[/ATTACH] [ATTACH type="full" alt="P1050608.JPG"]62111[/ATTACH] [ATTACH type="full" alt="P1050616.JPG"]62112[/ATTACH][ATTACH type="full"]62110[/ATTACH] [/QUOTE]
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Crank build for racing engine
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