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Post by ejparrott on Jan 26, 2015 10:01:04 GMT
NGG16's have tapered horn guides
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Post by Deleted on Jan 26, 2015 11:29:10 GMT
NGG16's have tapered horn guides don't all classes have tapered adjustable wedges? the old films that I've watched seem to show this...4472 certainly does although I can't remember if they are self adjusting but suspect they are...Don's design has dummy bolts placed at the bottom through the hornstay and in the front facing side of each main horn. If they are self adjusting I would assume that these are sprung loaded.. Pete
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baldric
E-xcellent poster
Posts: 208
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Post by baldric on Jan 26, 2015 11:41:54 GMT
NGG16's have tapered horn guides don't all classes have tapered adjustable wedges? the old films that I've watched seem to show this...4472 certainly does although I can't remember if they are self adjusting but suspect they are...Don's design has dummy bolts placed at the bottom through the hornstay and in the front facing side of each main horn. If they are self adjusting I would assume that these are sprung loaded.. Pete No, the GWR didn't fit them, I guess they relied on closer tolerances to start with using the Zeus optical alignment equipment. Baldric
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Post by Deleted on Jan 26, 2015 14:33:36 GMT
-------- cast steel boxes etc. which tended not to flex, and across-the-frame grinding equipment for accuracy ....
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61962
Seasoned Member
Posts: 129
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Post by 61962 on Jan 27, 2015 0:03:14 GMT
Pete,
Adjustable axlebox wedges were not universal. In a quick review I see that Adams fitted wedges to his LSWR 4-4-0 express locomotives. The Ivatt atlantics, Gresley O2, K3, A1/A3 and A4, P1, P2 and V2 were fitted,, Robinson atlantics and 2-8-0s, Whitelegg 4-6-4 tanks and some Southern 4-6-0s had wedges, but there is no evidence of them on GWR, LMS or BR standards. The first Gresley K3s were built with wedges, but later engines didn't have them because the earlier locos had an issue with them working loose. It was then discovered that the retaining studs were fitted horizontal in the early engines which caused the problem and the later batches reverted to wedges with the retaining bolts fitted normal to the sloping face of the wedge which fixed the problem. Thompson's new designs, B1 & L1 didn't have wedges, but by this time manganese steel liners were being used which was supposed to reduce the rate of wear and make adjustment unnecessary between overhauls. The A1 & A2 pacifics had wedges. I cannot remember any mention of automatic adjusters on any of the LNER classes.
Eddie
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61962
Seasoned Member
Posts: 129
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Post by 61962 on Jan 27, 2015 12:29:29 GMT
Didn't finish my post last night, it was getting late, so I will bring us back on topic.
Conventional practice is to provide a clearance of a thou per inch of diameter on bearings, so on a typical 5" loco you would need around half a thou on the side rod bearings. In practice this is not easy for most of us to achieve and if you aim for that and get a thou that's fine and leaves some room for lubrication. On the coupling rods, whilst theory might say they would go tight on a dip in the rail, you have to consider all those thous of clearance in the bearings and axleboxes, so you could add to your thou in the crank pins another for the axle in the axlebox and one or two more for the axlebox in the horns, lets say four and then that is available at each end of the side rod so there's potentially eight thou of slack to take up that 1.3 thou of angularity, and on the rod with the knuckle joint another thou as well. So really the bumpy track is not a great problem.
For comparison on a full size pacific the clearances are about 18 thou in the axleboxes, 10 thou in the axle bearings and four to six in the crank pins which adds up to about a 32nd of an inch. There's no way you would want to make them tighter than this because the last thing you want is a box sticking up in a horn guide, a sure precurser to a hot box or worse, a derailment.
My advice is to make everything as tight as you can without the individual components being unmovable. Once its all done and ready to run you will find that a couple of laps of the track will see it nicely free. If its not then the problem is elsewhere, probably dimensional errors or quartering. And just to answer one other question. 5 thou clearance is slack, 10thou is rattling and anything above that is a shopping proposal.
Eddie
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Post by Deleted on Jan 27, 2015 13:06:05 GMT
Yes, I would work to 1 thou per inch when re-making rod bushes at B'North ( Plus a few thou. extra oversize on a hole to allow for shrinkage when the bush was pressed home)...One way of preventing boxes getting jammed ( especially on Heritage Track or MPD yards etc.) is to remove the "inner" flange from the axlebox altogether with the "outer" flange having a pronounced curvature from top to bottom.........I would achieve this on the jig borer by placing a short length of power hacksaw blade between the angle plate and box at one end then the other This would give}.. 1/3 slight angled---1/3 straight----1/3 slight angled along the flange profile.......
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