Davey Posted December 18, 2011 Share Posted December 18, 2011 This is my first post on this site, so I aplogise in advance if this question has been asked before. I'm currently in the process of designing a Scale 7 layout based on the old Hull & Barnsley Railway c.1910. Amongst my locomotive fleet will ultimately be a couple of 0-8-0 locomotives. The question I have, is, what would be the minimum radius that a model 0-8-0 locomotive could negotiate. The locomotives in question would have rigid wheelbases of 16ft.-10ins. and 17ft-1in. respectively. Any direct answers or advice as to where I might find this informatio would be greatly appreciated. Dave Link to post Share on other sites More sharing options...
Western Star Posted December 18, 2011 Share Posted December 18, 2011 The question I have, is, what would be the minimum radius that a model 0-8-0 locomotive could negotiate. The locomotives in question would have rigid wheelbases of 16ft.-10ins. and 17ft-1in. respectively. The simple answer, although not necessarily easy to answer, is to find the minimum radius for the prototype and then reduce to 7mm scale. If the prototype minimum curve is of the order of 4 chains then gauge widening is desirable. An alternative answer, approach BIll Bedford who understands the mathematics of the calculation... you will need to specify the wheel diameters, the width over flanges and state if any wheels are flangeless. What might help you is to find out what level of side play was provided for each axle.... regards, Graham Beare Link to post Share on other sites More sharing options...
Davey Posted December 18, 2011 Author Share Posted December 18, 2011 The simple answer, although not necessarily easy to answer, is to find the minimum radius for the prototype and then reduce to 7mm scale. If the prototype minimum curve is of the order of 4 chains then gauge widening is desirable. An alternative answer, approach BIll Bedford who understands the mathematics of the calculation... you will need to specify the wheel diameters, the width over flanges and state if any wheels are flangeless. What might help you is to find out what level of side play was provided for each axle.... regards, Graham Beare Hi Graham, Many thanks for responding to my request, and thank you for the suggestions you've put forward. Best Wishes, dave Link to post Share on other sites More sharing options...
meil Posted December 19, 2011 Share Posted December 19, 2011 The question I have, is, what would be the minimum radius that a model 0-8-0 locomotive could negotiate. The locomotives in question would have rigid wheelbases of 16ft.-10ins. and 17ft-1in. respectively. It's what ever the model maker chose and built it to negotiate. Link to post Share on other sites More sharing options...
Davey Posted December 19, 2011 Author Share Posted December 19, 2011 It's what ever the model maker chose and built it to negotiate. Hi Meil, Firstly thanks for responding to my post. However I have to point out that your answer indicates that you don' t understand the question. Inevitably, as on real railways there is a minimum radius which any particular locomotive will negotiate. The longer the wheelbase, the greater the radius has to be. Going back to Scale 7 modelling, it is generally accepted that the minimum radius that an 0-6-0 locomotive will negotiate is around 6ft.-10ins. An 0-8-0 locomotive, by virtue of it's longer wheelbase will not negotiate a radius this small, unless you were to compromise the design of the kit. Where possible, I try make the dimension over the outside of the frames to scale width, but in certain circumstances it might be advantageous to narrow them slightly, thereby allowing extra side play on the wheel sets. Beyond this there is not much else you can do, so it all comes back to determining the minimum radius that the locomotive will negotiate. Regards, Dave Link to post Share on other sites More sharing options...
Poor Old Bruce Posted December 21, 2011 Share Posted December 21, 2011 There will have been umpteen 0-6-0 designs with a wheelbase of 16ft 6in (not significantly different fron the c17ft you give above) and some with longer wbs (e.g. the GER J19 at 17ft 8in and the J20 at 18ft 10in). Logically the lateral movement of the intermediate wheels on an 0-8-0 will be less that the middle wheels of an 0-6-0. the BR Standard loco diagrams all give a minimum radius of 3.5 chains. What prototype are you concerned with? This post edited to amend min rad. See Post #23 Link to post Share on other sites More sharing options...
Davey Posted December 21, 2011 Author Share Posted December 21, 2011 High P O B, Thanks for responding to my query. The two 0-8-0's I have in mind are the Hull & Barnsley 'A' Class (LNER Q10) having a wheelbase of 16ft-10ins and the Great Central 8A Class (LNER Q4) having a wheelbase of 17ft-1in. Regards, Dave Link to post Share on other sites More sharing options...
Poor Old Bruce Posted December 21, 2011 Share Posted December 21, 2011 Sorry Dave, the Q4 and Q10 are a bit out of my league. The RCTS green books seem to mention everything except minimum curvature. I see that J39s were 17ft wb BTW. Link to post Share on other sites More sharing options...
RMweb Gold Donw Posted December 31, 2011 RMweb Gold Share Posted December 31, 2011 you may find the prototype had frames narrowed in some cases to reduce the wear on the flanges and rails. Extra sideplay can make quite a difference. Perhaps a test bed using two plain strips drilled to the wheel bases and just ry it out rather than make a fully detailed frame and find you have problems. Don Link to post Share on other sites More sharing options...
Miss Prism Posted December 31, 2011 Share Posted December 31, 2011 The amount of sideplay between wheelsets and the track will be critical. Where no additional wheel-to-frame sideplay is provided, the published Scaleseven standards (http://www.scaleseve...rack-wheel.html) indicate there is 0.8mm sideplay between gauge-widened track and the outer faces of a wheelset's flanges. If that sideplay is plugged into a versine calculation (http://www.clag.org....h-traverse.html), where v = 0.8mm and c is the length of the wheelbase (say 125mm allowing for flange length, in your 17' case): r = (c^2)/8v = (125^2)/(8 x 0.8) = approx 2450mm (about 8' radius). This represents the loco flanges squealing around a gauge-widened curve. You'll find however the biggest problem area is in the vicinity of crossing vees on turnouts, where no gauge widening should (officially) apply. For such non-gauge-widened track, wheelset to track sideplay is down to 0.36mm, so your limiting radius now becomes r = (125^2)/(8 x 0.36) = approx 5400mm - ouch!!! 8-coupleds aren't quite as bad as an equivalent-length 6-coupled because the 8- 'straddles' the curve more, but nevertheless, if we take a typical turnout 'radius' (yes, I know that is being simplistic) of approx 8' in 7mm scale, then you would be looking for at least 0.5mm wheel-to-frame sideplay (to be provided on both sides of the chassis of course) to get round such a turnout. Any additional wheel-to-frame sideplay is therefore extremely beneficial. Link to post Share on other sites More sharing options...
Davey Posted December 31, 2011 Author Share Posted December 31, 2011 you may find the prototype had frames narrowed in some cases to reduce the wear on the flanges and rails. Extra sideplay can make quite a difference. Perhaps a test bed using two plain strips drilled to the wheel bases and just ry it out rather than make a fully detailed frame and find you have problems. Don Hi Donw, Many thanks for suggesting that I make a test bed frame, to see what is the minimum radius I can get away with. I think it's time to stop pondering and to do something more practical. Regards, Dave Link to post Share on other sites More sharing options...
Davey Posted December 31, 2011 Author Share Posted December 31, 2011 The amount of sideplay between wheelsets and the track will be critical. Where no additional wheel-to-frame sideplay is provided, the published Scaleseven standards (http://www.scaleseve...rack-wheel.html) indicate there is 0.8mm sideplay between gauge-widened track and the outer faces of a wheelset's flanges. If that sideplay is plugged into a versine calculation (http://www.clag.org....h-traverse.html), where v = 0.8mm and c is the length of the wheelbase (say 125mm allowing for flange length, in your 17' case): r = (c^2)/8v = (125^2)/(8 x 0.8) = approx 2450mm (about 8' radius). This represents the loco flanges squealing around a gauge-widened curve. You'll find however the biggest problem area is in the vicinity of crossing vees on turnouts, where no gauge widening should (officially) apply. For such non-gauge-widened track, wheelset to track sideplay is down to 0.36mm, so your limiting radius now becomes r = (125^2)/(8 x 0.36) = approx 5400mm - ouch!!! 8-coupleds aren't quite as bad as an equivalent-length 6-coupled because the 8- 'straddles' the curve more, but nevertheless, if we take a typical turnout 'radius' (yes, I know that is being simplistic) of approx 8' in 7mm scale, then you would be looking for at least 0.5mm wheel-to-frame sideplay (to be provided on both sides of the chassis of course) to get round such a turnout. Any additional wheel-to-frame sideplay is therefore extremely beneficial. Many thanks for a more mathematical approach to my request for information on the minimum acceptable radius for an 0-8-0. This is exactly the sort of thing I was looking for. Regards, Dave Link to post Share on other sites More sharing options...
meil Posted December 31, 2011 Share Posted December 31, 2011 Hi Meil, Firstly thanks for responding to my post. However I have to point out that your answer indicates that you don' t understand the question. Unfortunately you don't seem to understand how real locomotives are designed. Locomotives are designed to go around the curves they are required to negotiate, not the other way around. The centre driver flanges of 0-6-0s were often different to the outside wheels. The BR 9F was provided with flangeless wheels and the Midland/LMS 4-4-0 had different width of frames ahead of the driving wheels. I believe the GWR Castles has dished frames at the leading bogie. I suggest you design your models in the same way. Link to post Share on other sites More sharing options...
Davey Posted December 31, 2011 Author Share Posted December 31, 2011 Unfortunately you don't seem to understand how real locomotives are designed. Locomotives are designed to go around the curves they are required to negotiate, not the other way around. The centre driver flanges of 0-6-0s were often different to the outside wheels. The BR 9F was provided with flangeless wheels and the Midland/LMS 4-4-0 had different width of frames ahead of the driving wheels. I believe the GWR Castles has dished frames at the leading bogie. I suggest you design your models in the same way. Hi Meil, I do indeed understand how real locomotives are designed and what constraints are in place. I refer you to the last post by Miss Prism, above, which deals with the complex geometry involved in permanent way design. I should point out that I am not designing a locomotive, but merely intend to build a kit to scale 7 standards. The question I asked originally was about designing the track, not designing the locomotive. Regards, Dave Link to post Share on other sites More sharing options...
7mm Mick Posted January 5, 2012 Share Posted January 5, 2012 Hi Dave, I'll apologise in the first instance as this post is somewhat off topic but what make are the kits you have of the Q4 and Q10 ?? I only ask as I too model in S7 and intend to eventually build a model of Holderness Drain North which is a junction with sidings for timber just east of King George Dock and the period I model is immediately post nationalisation so there were still a few Q4's around which may have worked there. Also the whole location is on a curve so the outcome of this thread will be hugly helpful for me. And finally I have a L&Y Class 31 0-8-0 on the bench and was pondering starting the frames? Please post your progress so that I may follow your lead, ATB Mick Picture courtesy of Mick Nicholson, cheers Mick Link to post Share on other sites More sharing options...
Davey Posted January 5, 2012 Author Share Posted January 5, 2012 Hello Mick, It's nice to make contact with a fellow Scale 7 modeller and I look forward to seeing how your project progresses. At the moment I don't have a kit for the Q4 or the Q10, as my Hull & Barnsley based layout is still in the planning stage, which is why I started this new topic regarding the minimum radius for an 0-8-0. Having said that, I was contemplating building the Q4 from a Gladiator kit. At the moment there is no kit for the Q10, (H&BR A class), but Zenith Works do a 4mm kit, and my understanding is that at some time in the future, Paul Gram the owner, is contemplating producing a 7mm kit as one of his range of 7mm Hull & Barnsley locomotives, which are to be marketed by Laurie Griffin. Fellow Scale 7 modellers at the club I attend, have suggested that I get the layout built first, as they reckon once the track work is laid, it will motivate me to get locomotive building under way. I'm close to finalising the track plan now and am planning to start building track towards the end of this month. Once that's completed I can experiment with test bed frames as suggested by 'Donw' earlier in this thread. Sorry for the rather convoluted reply, but rest assured I'll keep you informed on developments as I progress. Regards, Dave Link to post Share on other sites More sharing options...
micknich2003 Posted January 6, 2012 Share Posted January 6, 2012 Attached a few pages from the specifications sent out by the H&B to the various loco builders when seeking tenders for the Class "A" engines. Hopefully they will be of interest. The specifications are silent on "Minium Radius". Best Wishes, Mick. Link to post Share on other sites More sharing options...
Davey Posted January 6, 2012 Author Share Posted January 6, 2012 Hi Mick, Many thanks for posting those pages of the 'A' class tendering specification. Best Wishes, Dave Link to post Share on other sites More sharing options...
7mm Mick Posted January 11, 2012 Share Posted January 11, 2012 Hello Mick, It's nice to make contact with a fellow Scale 7 modeller and I look forward to seeing how your project progresses. At the moment I don't have a kit for the Q4 or the Q10, as my Hull & Barnsley based layout is still in the planning stage, which is why I started this new topic regarding the minimum radius for an 0-8-0. Having said that, I was contemplating building the Q4 from a Gladiator kit. At the moment there is no kit for the Q10, (H&BR A class), but Zenith Works do a 4mm kit, and my understanding is that at some time in the future, Paul Gram the owner, is contemplating producing a 7mm kit as one of his range of 7mm Hull & Barnsley locomotives, which are to be marketed by Laurie Griffin. Fellow Scale 7 modellers at the club I attend, have suggested that I get the layout built first, as they reckon once the track work is laid, it will motivate me to get locomotive building under way. I'm close to finalising the track plan now and am planning to start building track towards the end of this month. Once that's completed I can experiment with test bed frames as suggested by 'Donw' earlier in this thread. Sorry for the rather convoluted reply, but rest assured I'll keep you informed on developments as I progress. Regards, Dave Dave apologies if there is a thread elsewhere detaining this already but i'd be interested to know more about your project. Where abouts are you planing to model on the H&B ? I always liked Kirk Smeaton which was a reasonable size and had a fw yard facilities and even a turntable. Incidently my brother works at the station now as he is a mechanic and the place is now a garage. He assures me the turn table pit is still there. Any chance of posting your track plan and how you're drawing it up, templot etc..,.? ATB Mick Link to post Share on other sites More sharing options...
Davey Posted January 11, 2012 Author Share Posted January 11, 2012 Hi Mick, I started out wanting to model an actual location, South Cave being my preferred choice, with Wrangbrook Junction a close second, but unfortunately due to space limitations, few of the track plans I've looked at could be scaled down to fit into my garage. Those that would, I deemed to be lacking in operational interest. So what I have come up with, is a might have been. In the early years of the 20th century the H & B was casting coveteous eyes on the lucrative Nottinghmshire and Derbyshire coalfields. The layout I'm planning to build, (c.1910) will be called Staircliffe Junction and will feature a H & B mainline leading to exchange sidings with the Great Central in the Annesley district of Nottinghamshire. The branch off the junction will be a H & B line tapping into the Great Central Railway (ex L.D. & E.C.R) near Clipstone. These connections with the G.C.R. will allow some foreign loco's to be seen The track plan, (designed on 'Templot') is almost finalised. I'm still trying to incorporate a turntable into the design to add more operational interest, the idea being that locomotives working trains into Annesley exchange sidings (one of the fiddle yard traversers), will run back light engine to Staircliffe Junction to be turned and serviced, prior to running back light engine to the exchange sidings prior to working their trains back north. As soon as I'm happy with the plan I shall post it on Templot for critical appraisal. If and when that's done, then I'll post the plan on this forum. Best Wishes, Dave Link to post Share on other sites More sharing options...
richard carr Posted February 12, 2012 Share Posted February 12, 2012 Dave I'm a scale 7 modeller too. I wouldn't worry what radius curve you can get a loco round that you haven't built yet. If I was you I would build your track and then build your loco to go round the curves. It is amazing how tight a radius you can get a loco to go round with very little modification from the real thing. Remember on the real thing the frames would flex to allow a loco to go round curves, sadly that feature of the real thing doesn't scale down and our frames don't flex, we build them rock solid. I have a couple of long wheelbase locos, a DJH 9f, with a flangless centre driver, but unfortunately that isn;t a realistic comparison as the frames are only about 3 foot 3 inches wide on the real thing, although it does have outside bearings. My JLTRT Class 40 diesel though has an effective 0-8-0 wheelbase of 21 feet 6 inches, it has very little side play and does not really like anything under an 8 foot radius curve (no gauge widening) you can see where the paint has rubbed off the wheels from contact with the frames. I also have a MMP class 40 its frames are much thinner so it has an extra 1mm of of sideplay and will go round a 6' 6'' radius curve. Richard Link to post Share on other sites More sharing options...
Katier Posted February 12, 2012 Share Posted February 12, 2012 If I understand Mick's scans correctly.. then the real thing had a 4'1" outside frame width and 4'5" back-to-back for the wheels. That gives about 2.1mm!!! in other words the .5mm mentioned earlier may well be SMALLER than the prototype. I personally would not be surprised if my math's isn't far out.. why? Because it's a loco which by it's very nature will be called upon to visit collieries where I imagine it will be faced with some challenging curves. Thus it would be designed to negotiate pretty challenging curves. Link to post Share on other sites More sharing options...
Poor Old Bruce Posted February 12, 2012 Share Posted February 12, 2012 Humble Pie time folks. Sorry but I got my numbers a bit (!) out in Post #6. Having looked at the diagrams again I see that the quoted "Minimum radius curve without gauge widening" is actually "6 chains (4.5 chains dead slow)" Just goes to show that one'smemory is not always reliable. Link to post Share on other sites More sharing options...
RMweb Gold Donw Posted February 13, 2012 RMweb Gold Share Posted February 13, 2012 Humble Pie time folks. Sorry but I got my numbers a bit (!) out in Post #6. Having looked at the diagrams again I see that the quoted "Minimum radius curve without gauge widening" is actually "6 chains (4.5 chains dead slow)" Just goes to show that one'smemory is not always reliable. 4.5 chains dead slow sounds typical dead slow means there will be some wheel squealing as it goes round. Thats 2.079m in 0 but how to you get the squeal. Don Link to post Share on other sites More sharing options...
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