Twins crankshaft sludgetraps early and late.

[chasdev]

My early G9 "full round" crankshaft has four sludge trap screws, the two normal small angled ones at the edges of the journal throw bosses and one large one at the outside center of each journal throw behind the outer main bearings.
All four when removed revealed solid plugs of sludge.
I also have two 1956 twins crankshafts with normal small sludge trap screws but the locations of the larger sludge trap plugs/screws seem to have been filled with pressed in plugs (or perhaps had the heads of whatever threaded body plugs ground off leaving just a center tapered hole and no observable means to remove them).
My question is, how are the later/larger plugs/screws serviced?
Unless the later cranks journals lack the early cranks version of this sludge cavity, it would seem to be a sludge and/or grinding grit time-bomb waiting to ruin a rebuild.
Although my early G9 rebuild should take many months, at some point In the distant future I plan on building a 56 twin as well, but the seemingly non-removable sludge trap plugs is giving me pause.Edited by - chasdev on 27 Dec 2010 1:37:53 PMEdited by - chasdev on 27 Dec 2010 2:48:39 PM

[Don Madden]

I cannot speak for the early crankshafts but the later ones do not really have sludge traps. The screws blank off the oilways drilled from the flywheels to the journals leaving very little space to collect sludge. They should be cleaned out when the crankshaft is serviced but since the drillways are the same diameter from end-to-end, I use extension drill bits of proper size. I see no reason that you cannot run the bits from the journal down to t he flywheel without removing the plug. Just be sure the flywheel end is securely plugged before fitting the shaft. As I recall, a speedometer inner cable also fits & the wire ends act as a scraper the ream out debris. Cheers, Don.

[chasdev]

I'll take some pictures to compare early "full round" cranks removable screws and and the later cranks non-removable plugs.
While the later versions may not have a true sludge trap, the fact that there is a plug in the same location as the removable large screws (found in the earlier version) seems to indicate or perhaps threaten a hidden depost of sludge needing attention.
I'm scratching my head over why there is an extra cavity in the journal in the first place, unless it was required for gas burping during the casting or perhaps they wanted to lighten the throw?

[chasdev]

I've got four nice photos of the early and late sludge trap screws/plugs that I can't post.
If anyone wants to see them, send me an email and I'll send them along.
Photobucket is not my cup of tea.Edited by - chasdev on 27 Dec 2010 7:15:29 PM

[zwarts]

I think you will find that the later 'non-removable' plugs are in fact the centres on which the crank is located when regrinding the crankpins.They are not plugs, but are simply machined into the crankwebs during manufacture.
Bob.

[chasdev]

I assure you that not only are the rod journal plugs not part of the crank but even if they were, the crankshaft is not mounted in the grinding machine using the rod throws as the centerline mount point.

[chasdev]

Pictures?[img]http://s226.photobucket.com/albums/dd158/chasdev/[/img]

[Don Madden]

I have worked on a lot of the later twin engines & none had a plug at the center of the journal. Perhaps a previous owner drilled & plugged there. There were only locating holes for centers so why do the machining if not used as such? Cheers, Don.

[chasdev]

I've got two 1956 cranks, one 500 and one 600 and other than the balance holes (and degree of wear/damage to the journals) they are identical which is to say they both have a countersunk taper hole in the center of the "plugs", one for each throw on both cranks.
Just for fun I may weld a bolt to one of the blind plugs and see it it's threaded or it I can slide hammer it loose.Edited by - chasdev on 28 Dec 2010 01:38:23 AM

[Duncan]

Chas, from the above descriptions I am afraid that the only fun you will get is a ruined crank, as the previous posters have stated the countersunk holes are not plugs. I have a later broken crank in front of me now and can confirm that there is no axial oil way running from this point. For a sectional drawing of the engine and crankshaft "CLICK HERE"