andyman7 Posted May 20, 2016 Share Posted May 20, 2016 I've started a new post for this as the previous thread 'revitalizing Wrenn locos' focuses on re-magnetizing. One of the Wrenn City of Birmingham locos I've acquired isn't running. A few checks have established that the driving wheels appear semi-seized. The loco looks to have spent the best part of 25 years stored either in it's box or in a cabinet and I suspect that original lubrication has dried out and gummed up the axles. Now where Rovex/Triang models are concerned this is very straightforward to deal with, whip out the motor and remove valve gear and the axles can be freed up. If really necessary the wheels can be removed - that entails re-bushing and quartering but at least I know what to do. I've however had much less experience with HD/Wrenn mechanisms. I don't know what the best technique is for removing the armature and what to watch out for, and of course would need to apply some sort of keeper to prevent demagnetising. The valve gear isn't screwed on like Tri-ang and I have no idea how to get that off either. The loco itself is worth enough for me if required to pay a specialist to do it but having been happily servicing Tri-ang models for years I feel somewhat inadequate where this one is concerned All help/advice appreciated! Link to post Share on other sites More sharing options...
Golden Fleece 30 Posted May 20, 2016 Share Posted May 20, 2016 Removing the valve gear needs a carefull prise with a small jewellers screwdriver BELOW the connecting rod, and above the coupling rod. This is to prevent damaging the return crank. These are pressed into the wheel as they have splines on just like axles. To remove the armature you need to unscrew the bearing above it although you may need to slacken the locknut first. When taking the bearing out becareful not to loose the ball bearing inside. After taking the armature out watch out for the ball bearing in the lower bearing. Upon installation make sure there is a very slight vertical movement to prevent the armature binding if it expands with heat. Hope this helps you. Garry Link to post Share on other sites More sharing options...
stewartingram Posted May 20, 2016 Share Posted May 20, 2016 I suspect that you may not need to remove the armature at all. Loosen the grubscrews on the gearwheel on the driven axle. This will allow you to turn the wheels by hand, without moving the armature (and conversely, run the armature alone, without moving the wheels). If the wheels are stiff to turn, a drop of penetrting oil might free them up, followed by proper lubrication. Worth a try? (Please don't mention that bodger's tool, WD40, which I hate!). As for remagnetising, I have a proper remag tool from my days as a service engineer for model shops. I'll do it free of charge (postage excepted) for RMWebbers. Stewart Link to post Share on other sites More sharing options...
andyman7 Posted May 20, 2016 Author Share Posted May 20, 2016 Thanks - I did wonder if loosening the grubscrews might work but due to the loco being such a nice one definitely wanted to ask first before finding out the hard way what does and doesn't work. My ability to strip Tri-ang models was learnt over many years of trail and error often with very playworn examples... It's useful to know about the valve gear attachment being a force fit - that is always worth knowing before you ease something off with a bit of pressure only to find you've stripped a thread or similar! Thanks for the offer on remagnetising, once the running gear is moving freely I can ascertain how strong the mechanism is. Link to post Share on other sites More sharing options...
Il Grifone Posted May 21, 2016 Share Posted May 21, 2016 This is common with mechanisms (not just trains!) that haven't been used for a time. The lubricant goes hard and sticks everything together. First of all dismantle the pick up assembly and then loosen the two grubscrews on the gear wheel. Take care they can break. The wheels should not turn, though I have had the gear seized to the axle! Next apply some solvent to the axle bearings, valve gear etc.*. I use white spirit/turps substitute, but IPA or penetrating oil will work. This usually turns black as the crud dissolves. A good wash and dry with a hair dryer and things should then turn freely. The motor bearings and gears should also receive attention. Now, apply power directly to the motor which should turn energetically in both directions. If all is well retighten the grubscrews and oil the mechanism. Next reassemble the pickup and track test. A good Dublo/Wrenn Coronation should go like the proverbial bat out of hell! * The use of an ultrasonic jewellery cleaning bath is ideal if one is available. It should not be necessary to remove the armature, but, if it is, first remove the brushes and springs taking care not to lose them (the springs are typical examples of the breed with a tendency to fly across the room...). remove the magnet using a keeper - essential or it will need remagnetising. Loosen the locknut (usually very tight) and unscrew the bearing. (Don't lose the ball bearings. - Initially the crud will hold them in place but once this has gone they could fall out.- they are even more expert than springs at losing themselves!) There is a groove on one side to allow the armature to come out clean and replace. There are several variations of armature:- Dublo and I think early Wrenn had a large commutator. Later production has a puny small one (why?) and longer brushes to suit. There is also a 5 pole armature fitted to some models. Hope that helps and I didn't include too much useless/obvious information. but a Dublo or Wrenn loco that doesn't work properly is a serious matter! Link to post Share on other sites More sharing options...
andyman7 Posted May 22, 2016 Author Share Posted May 22, 2016 Thanks for a very comprehensive rundown, that all makes sense! Link to post Share on other sites More sharing options...
Il Grifone Posted May 22, 2016 Share Posted May 22, 2016 You're welcome! I hope she's OK now. Link to post Share on other sites More sharing options...
andyman7 Posted May 23, 2016 Author Share Posted May 23, 2016 You're welcome! I hope she's OK now. I haven't had a chance to tackle it yet, pesky requirements of work etc mean that I will need to wait for the Bank Holiday weekend. I will post an update in due course..... Link to post Share on other sites More sharing options...
Il Grifone Posted May 24, 2016 Share Posted May 24, 2016 I'm retired now , but I've spent a lifetime, with first school/university and then work getting in the way of important things like trains.... Link to post Share on other sites More sharing options...
andyman7 Posted May 28, 2016 Author Share Posted May 28, 2016 Now I have got down to business the problem has been identified as binding/mangled valve gear. One of the con rods has a distinct 'u' shape to it which I am going to have to try and gently ease out or it will need replacing. Goodness knows what has been done in the past because the model shows very little sign of having been run but one con rod was on upside down and the gear behind one of the cylinders was completely out of position. I released both the grub screws on the main drive gear but it didn't seem to let the axle run free inside. I'm going to try and sort the valve gear without having to remove the armature but ideally of course valve gear should be fettled with no mechanism in place to ensure it is free running and with no tight spots. Still, as befits these projects I'm taking it slowly and methodically - at least Bank Holiday/Half Term gives me a bit more time to go back to it. The benefit is at least that the more I work on it the more I am getting familiar with the assembly and construction of the chassis, which remedies a long standing gap in my knowledge of British R-T-R 00 mechanisms - it's definitely sturdier than a Triang chassis, and bears no comparison with Mainline/Lima/Airfix.... Link to post Share on other sites More sharing options...
Il Grifone Posted May 28, 2016 Share Posted May 28, 2016 The service sheet for the Dublo version is here http://www.freewebs.com/mainlytrains/PDFs/Service%20Sheet%2012.pdf There may be slight variations for the Wrenn models of course. If the two grub screws are loose the wheels should turn freely (as should the armature under power). Obviously bent rods will not help. Luckily they are nickel-plated brass and usually amenable to straightening. I suspect replacement of coupling rods will mean removing the wheels, because the crank pins are probably riveted over on the back. Link to post Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.