6029 King Stephen Posted October 27, 2016 Share Posted October 27, 2016 Hi, I have tried to build Comet GWR chassis kits in the past including the King and Hall and am now building a 28xx chassis to go under the K's kit body. This time the chassis itself has gone together really well and has reached the painting stage. I have assembled the cylinders OK and have fitted the slide bars but I have encountered the same problem as I have with previous attempts to build these chassis and that is when fitted the lost wax brass conrod (?) to slide in the cylinder, it pushes the slide bars apart and does not slide at it should do. I have tried to file the grooves on the conrod to deepen them so that it doesn't push the slide bars apart but I think it needs something more drastic to enable it to slide properly. I have thought about a cutting disc in a minidrill as lowish speed but does anyone have any other suggestions or know of any better replacements for the brass item that is invariably bent on arrival? Thanks, Steve Link to post Share on other sites More sharing options...
RMweb Premium Trainshed Terry Posted October 27, 2016 RMweb Premium Share Posted October 27, 2016 My first question when you folded slide bars up where they soldered up. I have made to of these chassis and they do go together if taken time to ensure that things are squire. As they need to cleaned up thoroughly and fettled to ensure that they are clean and free from solder for smooth running Terry Link to post Share on other sites More sharing options...
RMweb Gold Barry Ten Posted October 27, 2016 RMweb Gold Share Posted October 27, 2016 You have to widen/deepen the slots in the crosshead (the lost wax bit) a lot more than you think. A very narrow file is sufficient, just taking your time and opening up the slots until the crosshead is a good sliding fit, but absolutely not loose. I'd be wary of going near it with a power tool. I find that the bent brass can be eased back into shape with gentle action from a pair of pliers, taking care not to damage the brass. I talked to the late Geoff Brewin of Comet about getting a good fit between the crosshead and the slidebars and he said not to file the slidebars (other than fettling) but to make the crosshead fit the slidebars. The important thing is not to overdo it, as a sloppy fit is as bad as a tight one. One thing I've found is that, when you're getting close, drop a bit of lubricant on the assembly and you may find that's all you need to get a nice smooth fit. Link to post Share on other sites More sharing options...
DCB Posted October 29, 2016 Share Posted October 29, 2016 Sounds like you have the same problem as Churchward, He solved it with a huge motion bracket sweeping down outside the slide bars on the 2-8-0 and inside on the 4-6-0s. So for a proper job file up the crosshead and make up a good solid motion bracket to hold the slide bars firmly in place. It may well have to go through the footplate to make it strong enough (like Churchward did) I have a thin possibly etched Brass chassis for my K's 28XX with the same flimsy slidebar issues among others. Most "Scale" slidebars are hopelessly underscale which adds to the problems Link to post Share on other sites More sharing options...
6029 King Stephen Posted October 31, 2016 Author Share Posted October 31, 2016 The slide bars are sweated together as per the Comet instructions and this has been tidied up so that it is smooth along the edges. The solution would appear to be to file the groove in the crosshead to accept the slidebar without it splaying as the crosshead moves towards the cylinder. Regards, Steve Link to post Share on other sites More sharing options...
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