RMweb Gold Stubby47 Posted October 15, 2015 RMweb Gold Share Posted October 15, 2015 Hi all, As I am scratch building the chassis for the PSMT loco I have been wondering how to ensure the extended axles are quartered correctly. Then it occurred to me - does it really matter ? I understand on a prototype loco the application of steam power through the pistons and associated mechanicals is a finely tuned engineering masterpiece, and quartering is needed to allow the application of that power in an efficient way. But as model wheels and valve gear are driven by a motor, is the same level of accuracy necessary ? Stu Link to post Share on other sites More sharing options...
micknich2003 Posted October 15, 2015 Share Posted October 15, 2015 A degree or so either way won't matter, but it helps if all axles are set exactly the same. think about it, whatever the "Angle", the rod centres and crank pin centres must match. Link to post Share on other sites More sharing options...
RMweb Gold Stubby47 Posted October 16, 2015 Author RMweb Gold Share Posted October 16, 2015 Thanks Mick. Yes, I understand they do have to be the same on each axle end for each side, it was at the ends of each of the axles I was musing about. Link to post Share on other sites More sharing options...
Guest Lyonesse Posted October 16, 2015 Share Posted October 16, 2015 Hi all, As I am scratch building the chassis for the PSMT loco I have been wondering how to ensure the extended axles are quartered correctly. Then it occurred to me - does it really matter ? I understand on a prototype loco the application of steam power through the pistons and associated mechanicals is a finely tuned engineering masterpiece, and quartering is needed to allow the application of that power in an efficient way. But as model wheels and valve gear are driven by a motor, is the same level of accuracy necessary ? Stu Somewhere near 90 deg is good enough, provided it is consistent from axle to axle. And note that some three cylinder locos had crankpins set 120 deg apart. Link to post Share on other sites More sharing options...
Spitfire2865 Posted October 16, 2015 Share Posted October 16, 2015 Honestly, what matters isnt the angle they are at, but consistency. Its just easier to go the prototype route and make them as close to 90 as possible. Link to post Share on other sites More sharing options...
Kenton Posted October 16, 2015 Share Posted October 16, 2015 Never been one to use a tool to the job and have always done it with the No 1 eyeball. You will be surprised just how good an eye can be at getting things like alignment correct. As close as makes no difference. But there is always a GW quartering gauge if you have wonky* eyes. If it is way out you will soon know about it and the loco will appear to limp or lock up completely. It will also impart uneven wear on pistons and even crank pins. Both of which will gradually go from discernible to a cripple**. * a medical term ** not a medical term Link to post Share on other sites More sharing options...
34theletterbetweenB&D Posted October 16, 2015 Share Posted October 16, 2015 Somewhere near 90 deg is good enough, provided it is consistent from axle to axle. And note that some three cylinder locos had crankpins set 120 deg apart. The 90 deg setting is the most tolerant of error, so getting as close as possible to a true 90 deg setting is a good plan. Successful 4mm models with the 120 deg setting have been made, but it's a whole lot more 'picky' about consistency from axle to axle. Before the variable astigmatism I now 'enjoy' kicked in, I would do 90 deg by eye without hesitation, but wouldn't ever have considered 120 deg without some form of jig - such as a wheel press modifed with an extra crankpin locating hole - to ensure the best possible consistency wheelset to wheelset. Link to post Share on other sites More sharing options...
RexAshton Posted October 16, 2015 Share Posted October 16, 2015 A degree or so either way won't matter, but it helps if all axles are set exactly the same. think about it, whatever the "Angle", the rod centres and crank pin centres must match. 90 degrees plus 1 or 2 is what you're after. Under 90 degrees you'll almost certainly get lumpy running particularly on a 4 or 6 coupled chassis. Link to post Share on other sites More sharing options...
RMweb Gold Enterprisingwestern Posted October 17, 2015 RMweb Gold Share Posted October 17, 2015 I once put rods on a Hornby shunter mirror image, ran perfectly, so I would say as very few people can see both sides of a locomotive simultaneously, does it matter? Mike. Link to post Share on other sites More sharing options...
M Wright Posted October 17, 2015 Share Posted October 17, 2015 Hi, I set my one off locos, both electric and steam powered by eye. I have built about 50 so far from 2mm to the foot to 4" to the foot. If I ever built a three or four cylindered steam loco I would not quarter a loco by eye given the huge investment of time in such a model. Jigs and gauges would have been made at the start. If you want YOUR model to be as perfect as you can make it, make a gauge to ensure your quartering, obviously it is utterly reliable and removes time wasting hassle and usually when trying to do this three or four hands!. Three factors in my experience are essential to smooth running and the use of jigs (whether made or built in. In the case of kit building the designer of the etch/laser cut will have incorporated this) essential (1) That the axle centres exactly coincide with the centres on the coupling rods (2) the crankpin is exactly vertical to the face of the wheel or crank and consequently parallel to the axle. (3) The throw of the crankpins are identical. If any of these three conditions are not met building your chassis will be a pain. It will have a limp, you will waste hours trying to get rid of the limp using a rat tail file in the coupling rods holes and other horrid practices. When you buy in parts like wheels assume nothing, check they are concentric, check the crank throw with a clock gauge, check the crankpin hole is parallel to the axle. The other 300 or so locos I have made over the last decades are batch built steam powered engines. Each loco type has its own box of jigs and gauges to try to make assembly rapid and consistent. One of the jigs is always a quartering jig. SO if its for me I often use my eye and take time, If it is for one of you I use jigs. The last thing I want to do is waste hours trying to get a lumpy runner to run sweetly! Link to post Share on other sites More sharing options...
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