dpgibbons Posted September 7, 2020 Share Posted September 7, 2020 (edited) I have a Scorpio 7mm 0-6-0T kit bought cheaply on eBay. The chassis has been built up as far as pickups and with no compensation, but the build quality is poor and it's pretty clearly out of true. So how best to proceed? Could I resolder it up part by part using my newly acquired Avonside chassis jig? Should I unsolder the whole thing by say putting it into the oven (if that's feasible) and start again? Or should I trade time for money and ask Scorpio if they can resupply the chassis parts? Edited September 7, 2020 by dpgibbons Link to post Share on other sites More sharing options...
Brassey Posted September 7, 2020 Share Posted September 7, 2020 I have one of those gas blow torches now but in the past have resorted to the gas ring to unsolder entire jobs. It does not take much heat to loosen the solder. I would be concerned about getting the metal too hot as that might have some effect on it. Link to post Share on other sites More sharing options...
Matti8 Posted September 7, 2020 Share Posted September 7, 2020 I wouldn't recommend the gas torch, I have one. But if it were me I would definitely unsoldered and resolder using your jig. Not sure about the oven thing do people really do that? Link to post Share on other sites More sharing options...
TT-Pete Posted September 8, 2020 Share Posted September 8, 2020 I've only used the oven to heat up needle files that had become clogged with whitemetal filings (when hot you rap the file against a hard surface and the whitemetal blobs fall off), for desoldering I use desoldering wick: https://uk.rs-online.com/web/p/solder-wicks/3829832/ You place the wick over the part to be desoldered and put the iron on the wick, as the solder melts it gets sucked up/absorbed by the wick. Pull the wick away, snip the end off the wick, move forwards, repeat... A bit laborious perhaps, but the advantage is it does one part at a time and you can go over again on the same area and get just about everything off. 2 Link to post Share on other sites More sharing options...
dpgibbons Posted September 8, 2020 Author Share Posted September 8, 2020 Thanks. Having got my head around the chassis jig, Plan A is to ease the bearings into alignment one by one using a soldering iron. If it comes to a complete disassembly, I'm thinking a cheap hot air desoldering gun would be much safer than a blowtorch and much faster than solder wick. Link to post Share on other sites More sharing options...
brossard Posted September 8, 2020 Share Posted September 8, 2020 This is interesting. I have a second (or third?) hand Slater's 1F kit that is partially assembled. The chassis looks reasonable but the bearings will have to be replaced. I have the Avonside jig and the 7mm axle rods for it. It will be good to see how you get on. This kit is very much on the back burner as I work on the layout. John Link to post Share on other sites More sharing options...
dpgibbons Posted September 8, 2020 Author Share Posted September 8, 2020 So far so good. I have unsoldered the bearings and relocated them on the jig using the coupling rods and the long pins. The chassis is a fold-up so I'm trusting it will be horizontally square. Just need to make sure everything else is aligned before resoldering. Link to post Share on other sites More sharing options...
doilum Posted September 8, 2020 Share Posted September 8, 2020 Radical option. This is a fairly simple chassis, why not invest £5 in a strip of brass and scratch build a replacement. Assuming that the coupling rods are OK the hard work is already done. A supply of 1mm drills, pin vice and a jeweller' s saw and you are good to go. The Scorpio frames are not the thickest and if the soldering has been overdone may well end up anything but straight. A Dremel is a useful tool for this kind of salvage work. Link to post Share on other sites More sharing options...
dpgibbons Posted September 8, 2020 Author Share Posted September 8, 2020 Fortunately the chassis looks straight and any visual nasties will be hidden by the outside frames (it's a GWR Buffalo). As I'm fairly new to this, scratch building a replacement would be Plan Z. Link to post Share on other sites More sharing options...
O-Gauge-Phil Posted September 8, 2020 Share Posted September 8, 2020 Hi First thing I would do is remove the wheels and place a 3/16 rod in each axle hole . Depending on how out of square it is , you might just be able to remove the bearings open out holes and re-assemble using your nice new jig. lf the chassis is banana shaped you may have to remove the spacers and rebuild. dis-assembly will require a lot of heat , so preheating in an oven will save distortion and the part can be removed with a poke of the soldering iron. See not for Peter, he is the bees knees at this! Good luck. Link to post Share on other sites More sharing options...
hayfield Posted September 8, 2020 Share Posted September 8, 2020 Whilst it was a 4MM scale Southeastern Finecast chassis and a Hobby Holidays jig. The SEF chassis axle holes had been badly damaged by someone taking lumps out of the circle I took the chassis apart, then repaired the damage the best I could. I then set the jig up using the coupling rods and soldered axle bearings into the frames. Finally used the jig to assemble the frames into a chassis. In short have a go, you may have to carefully open up the axle holes a bit. Link to post Share on other sites More sharing options...
5050 Posted September 8, 2020 Share Posted September 8, 2020 I use the gas ring. Hold the offending parts(s) in a pair of long nose pliers in the flame for only a couple of seconds and it all falls apart. Won't damage the cooker as it's ceramic. Cleaning excess solder off can be a bit of a task at times but a desolder wick certainly helps. I've 'rescued' several 4mm etched kits like this. Link to post Share on other sites More sharing options...
dpgibbons Posted September 12, 2020 Author Share Posted September 12, 2020 I have now refitted the bearings using the chassis jig. This required some filing, which rather confirms that the original axle alignment was out of true. The chassis rolls a little stiffly but with rods fitted on one side there's no binding. Once I get hold of a 1.75mm Allen key to put the rods on the other side I'll know if all is well. I've also realised that the kit provides the option to use the outer hornblocks as bearings so that's the new Plan B. 1 Link to post Share on other sites More sharing options...
david.hill64 Posted September 12, 2020 Share Posted September 12, 2020 A bit late to comment now but you can use a gas ring or cooks blowtorch safely to disassemble a poorly built nickel silver or brass model. 'Normal' solder melts at about 186 degrees, far below the temperature when brass glows red (650 - 750 degrees). Obviously not suitable for whitemetal!!! Once apart the desoldering wick is useful for cleaning up. You do need to ensure that the chassis rolls freely without the rods on and that all wheels touch the ground at the same time and the axles are parallel to each other. Your jig will assist in that. I would also strongly recommend investing in a 3/16" and a 4.8mm parallel hand reamer. Run these through the bearings to ensure that the axles are a good fit (ie not too tight nor sloppy). Not cheap, but well l worth it. David 1 Link to post Share on other sites More sharing options...
doilum Posted September 12, 2020 Share Posted September 12, 2020 5 hours ago, david.hill64 said: A bit late to comment now but you can use a gas ring or cooks blowtorch safely to disassemble a poorly built nickel silver or brass model. 'Normal' solder melts at about 186 degrees, far below the temperature when brass glows red (650 - 750 degrees). Obviously not suitable for whitemetal!!! Once apart the desoldering wick is useful for cleaning up. You do need to ensure that the chassis rolls freely without the rods on and that all wheels touch the ground at the same time and the axles are parallel to each other. Your jig will assist in that. I would also strongly recommend investing in a 3/16" and a 4.8mm parallel hand reamer. Run these through the bearings to ensure that the axles are a good fit (ie not too tight nor sloppy). Not cheap, but well l worth it. David Old school fixed chassis often had centre wheels marginally high to avoid rocking over rough track. Link to post Share on other sites More sharing options...
david.hill64 Posted September 12, 2020 Share Posted September 12, 2020 3 hours ago, doilum said: Old school fixed chassis often had centre wheels marginally high to avoid rocking over rough track. True, but many more recent kits allow for a floating centre axle, which is a better solution. The only other point of course is to ensure that the axle bearings are at the same spacings as the coupling rods. 1 Link to post Share on other sites More sharing options...
dpgibbons Posted September 12, 2020 Author Share Posted September 12, 2020 19 hours ago, david.hill64 said: bit late to comment now but you can use a gas ring or cooks blowtorch safely to disassemble a poorly built nickel silver or brass model. My idea was to put the item on a grate above a drip tray and give it a gentle baking in an oven at say 220 degrees. That would remove any risk of overheating the metal and allow all the solder to drip away, with the mess contained below. A little work with the tongs would be required to keep flat surfaces vertical. However nobody has suggested an oven, so are there are unforeseen risks of pollution and marital strife? Link to post Share on other sites More sharing options...
O-Gauge-Phil Posted September 13, 2020 Share Posted September 13, 2020 (edited) If might not be necessary to strip everything down, sometimes just remove or reposition.. Preheating in an oven just makes things easier. I sometimes preheat white metal kits , usually keeping them on the radiator, it just means I can use a smaller iron to get to those hard to reach areas and the solder flows better. As for SWMBO are you man or mouse? Someone told me there's two types of blokes, those under the thumb and the liars. Cheers Phil Edited September 13, 2020 by O-Gauge-Phil Link to post Share on other sites More sharing options...
david.hill64 Posted September 14, 2020 Share Posted September 14, 2020 On 13/09/2020 at 07:56, dpgibbons said: However nobody has suggested an oven, so are there are unforeseen risks of pollution and marital strife? Don't forget that lead is poisonous, so I would not run the risk, however small, of contaminating the oven with lead and infusing it into the Sunday roast, or pizza or whatever floats your culinary boat. 1 Link to post Share on other sites More sharing options...
dpgibbons Posted October 25, 2020 Author Share Posted October 25, 2020 (edited) Further on this topic, I bought from eBay a cheap temperature-controlled hot air desoldering gun (like this one) on the basis that even if it wouldn't cure a bodged chassis it would certainly be useful for bodged PCBs, of which I have a growing number. Its first use was to unsolder a whitemetal chimney. It had been crookedly but very thoroughly attached using 100 degree solder onto a pre-tinned smokebox, so I did not hold much hope of getting it off unscathed. But after a few minutes of hot air, starting gingerly at 120 degrees and increasing to 160 (to overcome the heatsink effect), it popped off undamaged. No doubt I will soon give myself the opportunity to discover if it will deal as efficiently with 145 degree and electrical solder. Edited October 25, 2020 by dpgibbons Link to post Share on other sites More sharing options...
hayfield Posted October 25, 2020 Share Posted October 25, 2020 Thanks for the heads up on this, I tend to use steam for a kettle for 75 degree solder, even I assume 100 degree may work this way. Link to post Share on other sites More sharing options...
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