Modern Steamers - plastic bottom-plate

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Modern Steamers - plastic bottom-plate - The bent bottom-plate strikes again.

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Poor Skeleton		#1 Posted : 01 August 2021 16:29:15(UTC) Retweet
Joined: 09/10/2015(UTC) Posts: 550 Location: England, Cambridge		Some of you will remember the problems husafreak and I had with our 88889 locos caused by the bottom-plate that holds the wheels and gears in place being distorted and causing a variety of problems. https://www.marklin-users.net/fo...sts/t45352-Marklin-88889 I've been running a variety of trains this weekend following yet another set of mods to my controller and I noticed my 88740 was stalling (either electrically, mechanically of a combination of the two) at specific points (that is turnouts/switches) on the layout. My 88742, by contrast, was running round the layout as sweet as a nut. After a bit of investigation and a lot of head-scratching I checked the flatness of the bottom plate to find it was bowed outwards in the middle. This was causing the loco to bottom out when it passed over the switch rails. Having removed the bottom plate I softened the plastic a bit in boiling water and the held it straight as it cooled. On replacing it, I took great care not to over tighten the fixing screws. (I'm learning with Marklin that you should never tighten screws beyond the point they start to "bite".) Back on the track, I now have another nice runner. Anyway, another potential problem to be on the look-out for. The new steam locos with their brake gear and enhanced valve gear really do look the part, but the increased sophistication does seem to bring with it a number of problems! All the best Chris

3 users liked this useful post by Poor Skeleton		parakiet, Carim, Zme
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marklinist5999		#2 Posted : 01 August 2021 16:56:08(UTC) Retweet
Joined: 10/02/2021(UTC) Posts: 3,117 Location: Michigan, Troy		Don't overtighten screws, and if it is abit warped, a small spacer washer one one screw may help.


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husafreak		#3 Posted : 01 August 2021 18:37:40(UTC) Retweet
Joined: 09/04/2019(UTC) Posts: 558 Location: California, Bay Area		Ah, another “fish belly” type warp. Really glad you tried boiling it and bending it, and that it worked! I have one of these (or similar-have to check) which occasionally hangs up on my Rokuhan switches, especially at slow speed, and I always thought it was something to do with the sand pipes hanging down so far. Further inspection required.


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Poor Skeleton		#4 Posted : 01 August 2021 20:55:34(UTC) Retweet
Joined: 09/10/2015(UTC) Posts: 550 Location: England, Cambridge		Originally Posted by: husafreak Ah, another “fish belly” type warp. Really glad you tried boiling it and bending it, and that it worked! I have one of these (or similar-have to check) which occasionally hangs up on my Rokuhan switches, especially at slow speed Sounds very much like it could be the same thing. It's a real flaw of the design that the bottom plate isn't supported in the screw area so any tension on the screw will tend to cantilever the plate and distort it. Quote: I always thought it was something to do with the sand pipes hanging down so far. I have had that, too! Good luck! Chris


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Poor Skeleton		#5 Posted : 01 August 2021 21:00:27(UTC) Retweet
Joined: 09/10/2015(UTC) Posts: 550 Location: England, Cambridge		Originally Posted by: marklinist5999 Don't overtighten screws, and if it is abit warped, a small spacer washer one one screw may help. Trouble is, in this context not over-tightening the screws seems to mean leaving them so slack they might work loose in normal use! I don't understand why the design doesn't include a bush to support the bottom plate and prevent the plate from distorting. (Interestingly, the rear bogie of 88889 does have such a bush, but it's not long enough to support the plate!) Cheers Chris

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