Wright writes.....

[AndyID]

Is this a genuine attempt to re-invent the wheel?

 

My slightly coned wheels work very nicely on my slightly inclined rail, rather like the prototype so I won't be changing to something untried, unnecessary and unprototypical any time soon.

 

Too late I'm afraid. That wheel has already been reinvented. A lot of prototype railway equipment operates with wheel tapers of 1:40 and even less. (btw Romfords are 1:15)  A 1:40 taper on a 00 model is indistinguishable from no taper at all.

[AndyID]

On straight track the coning centres the wheels on the rails so that they do not hunt from side to side 

 

Hi Sandra,

 

Actually, it's the other way around. Hunting is a consequence of coning. It happens because coning steers the wheels towards center but they "overshoot" and then steer back towards center, overshoot again and so on. If the coning is too extreme hunting becomes really violent at high speeds. That's why high speed equipment uses very little tread taper.

 

Cheers!

Andy

 

EDIT: More that you will probably ever want to know about coning in this thread. 

http://www.rmweb.co.uk/community/index.php?/topic/102374-do-we-need-coned-wheels/page-6&do=findComment&comment=2002061

Edited October 28, 2015 by AndyID

[corneliuslundie]

Is it worth looking at attempts with the prototype to use compensation? I know that 4-point compensation has been used on steam locos but it hasn't become standard so presumably it did not perform too wonderfully. Does anyone know more?

 

Jonathan

[AndyID]

Is it worth looking at attempts with the prototype to use compensation? I know that 4-point compensation has been used on steam locos but it hasn't become standard so presumably it did not perform too wonderfully. Does anyone know more?

 

Jonathan

Hi Jonathan,

 

That would be interesting to know, but the problem I think is that so many effects are completely different when scaled down by a couple of orders of magnitude.

 

For example, IIRC I've read that real railway suspension systems are expected to accommodate maximum track "warp" of  1 inch over a length of 8 feet. That's not very much. If we are applying suspension systems to models in an attempt to accommodate far greater amounts of warp we are hardly applying "prototype practice".

 

The amount of track warp a real steam locomotive can handle must be quite small (maybe someone has some data?). I don''t think the coupling rods make any provision for non-parallel bearing axes, so any track warp has to be accommodated by clearance in the bearings and/or twisting of the coupling rods themselves.

 

Cheers!

Andy 

[billbedford]

Is it worth looking at attempts with the prototype to use compensation? I know that 4-point compensation has been used on steam locos but it hasn't become standard so presumably it did not perform too wonderfully. Does anyone know more?

 

 

Most American, and many European, locos had equalisation beams between springs. They were usually arranged so that there was a three point suspension. As far I know the only (relatively modern) locos that were entirely unsprung were some Aveling and Porters which were based on traction engines.

[LNER4479]

For example, IIRC I've read that real railway suspension systems are expected to accommodate maximum track "warp" of  1 inch over a length of 8 feet.

 

RSSB's Railway Group Standards website is your friend:

http://www.rssb.co.uk/rgs/standards/GMRT2141%20Iss%203.pdf

 

If you feel so moved, page 12 contains a virtually unfathomable diagram as to how real rail vehicles are assessed for 'derailment resistance'. The other relevant term is 'wheel unloading' which is railway euphemism for 'it's fallen off'. And the technical term for a 'warp' is 'track twist' (sorry!)

 

The EU Rolling Stock TSIs probably have some equivalent methodology.

[AndyID]

RSSB's Railway Group Standards website is your friend:

http://www.rssb.co.uk/rgs/standards/GMRT2141%20Iss%203.pdf

 

If you feel so moved, page 12 contains a virtually unfathomable diagram as to how real rail vehicles are assessed for 'derailment resistance'. The other relevant term is 'wheel unloading' which is railway euphemism for 'it's fallen off'. And the technical term for a 'warp' is 'track twist' (sorry!)

 

The EU Rolling Stock TSIs probably have some equivalent methodology.

 

Thanks! I believe "unloading" refers to the situation where, due to the suspension arrangements, a wheel tread is no longer in contact with the rail - something that also tends to happen on rigid chassis model locomotives with coned wheels

 

BTW, "warp" is the technical term in the US, but they might also use "twist".

[Theakerr]

I read that one of the reasons people purchase a Golden Age model is for the hauling capacity.  Further, I read that the reason they are such good haulers is because their driving wheels are all independently sprung ensuring  all wheels are in contact with the track.  So, does the collective feel this is valid as far as the impact of the sprung drivers?

[AndyID]

RSSB's Railway Group Standards website is your friend:

http://www.rssb.co.uk/rgs/standards/GMRT2141%20Iss%203.pdf

 

If you feel so moved, page 12 contains a virtually unfathomable diagram as to how real rail vehicles are assessed for 'derailment resistance'. The other relevant term is 'wheel unloading' which is railway euphemism for 'it's fallen off'. And the technical term for a 'warp' is 'track twist' (sorry!)

 

The EU Rolling Stock TSIs probably have some equivalent methodology.

 

Despite the confusing looking diagram, it looks like it comes out at a similar amount as the thing I read. 1:150 would be 1 inch in 12.5 feet.

[AndyID]

I read that one of the reasons people purchase a Golden Age model is for the hauling capacity.  Further, I read that the reason they are such good haulers is because their driving wheels are all independently sprung ensuring  all wheels are in contact with the track.  So, does the collective feel this is valid as far as the impact of the sprung drivers?

 

Only if you accept anecdotal statements as hard evidence

[billbedford]

So, if my friend fitted tension-lock couplings to his P4 wagons, it would cure any problems of derailments in propelling them through complex trackwork?

 

Yep.

 

And, though I have too many wagons still fitted with tension-locks (work in progress to remove them and fit better alternatives), the rake I was describing is fitted with Sprat & Winkle and three-links.

 

As far as propelling is concerned tension locks and Sprat & Winkles ate effectively very similar. Both use a single smooth point of contact on the wagon's centre line.

 

I know non-prototypical couplings aid the propelling of wagons without derailment, if only because they obviate the problem of buffer-locking (and, in my view sprung buffers are more of a problem in this). In my experience, buffer-locking between adjacent vehicles is the main reason for derailments under propulsion, and no amount of fancy compensation will prevent that. 

 

I disagree. I think the main reason that there are derailments while propelling is that there can be too much friction between buffer faces and that lead them to jamb together and if the track is not perfectly level can leave the wagon 'hanging'. This is probably less of a problem were the buffet are plastic, but steel buffer heads seem to be prone to this. I believe that something similar happened on full-sized stock since I remember that many wagon appeared to have a patch of geese in the centre of each buffer.

Edited October 28, 2015 by billbedford

[t-b-g]

Yep.

 

 

As far as propelling is concerned tension locks and Sprat & Winkles ate effectively very similar. Both use a single smooth point of contact on the wagon's centre line.

 

 

I disagree. I think the main reason that there are derailments while propelling is that there can be too much friction between buffer faces and that lead them to jamb together and if the track is not perfectly level can leave the wagon 'hanging'. This is probably less of a problem were the buffet are plastic, but steel buffer heads seem to be prone to this. I believe that something similar happened on full-sized stock since I remember that many wagon appeared to have a patch of geese in the centre of each buffer.

 

That statement is not correct. Sprat and Winkle couplings use the buffers of the wagons when propelling. The single centre fixed point only applies when hauling.

 

I find that the biggest problems propelling long trains over curves and points come when you have what is effectively a loco pushing some wagons against a heavy load going round a bend. It matters not what sort of couplings you use. The weight of the wagons at the far end away from the loco tend to force the wagons nearer the loco outwards on a curve as the loco pushes against them.

 

Pushing hard round a curve with a compensated wagon is more likely to cause it to tilt and give buffer height problems than a rigid wagon.

 

I have have seen some really long trains (40 plus wagons) in P4. It was many years ago on Whetstone (by Andy Gibbs - he scrapped it after a couple of shows because it never ran well - too many derailments) but I have certainly never seen one being propelled through complex pointwork. Has it ever happened?

 

I find that reliable propelling needs buffer heights to be consistent. It needs wagons to be evenly weighted (but not too heavy) and free running to reduce the forces pushing wagons sideways and it needs not too much sideplay in the axles and wheels so wagons can't "crab". This last one is where the finer scales do score over OO but it doesn't mean that it can't be done. Finally, well laid and aligned track is a big factor too.

[AndyID]

it needs not too much sideplay in the axles and wheels so wagons can't "crab". This last one is where the finer scales do score over OO but it doesn't mean that it can't be done. Finally, well laid and aligned track is a big factor too.

 

That's one of the arguments for EM, and the dreaded "EM-2". There is a large side clearance between the flanges and the rail with 00, so even if there is little to no sideplay with the axles (there usually isn't any with pin-point axles) vehicles can still crab, a lot, and that also tends to make the flanges climb up the rails,

[Tony Wright]

Only if you accept anecdotal statements as hard evidence

An interesting observation.

 

I have a Golden Age A4. Why I bought it, I'm not sure now, but it was originally offered to me FOC because I'd done a lot of photographs for Golden Age. I was about to write a review (which I did) and I was not prepared to take the risk of being accused of giving a favourable review. As it was, all the Golden Age OO A4s I photographed were very accurate.

 

But, and this is very interesting because the evidence is empirical. Despite its every driven axle being sprung, it is far less sure-footed than any of the three Wills/SE Finecast A4s I've built rigid. Weight-wise they're much the same, but the GA one slips violently when opened up on a heavy train, even at speed. The ones I've made just walk away with any train.

 

As a footnote, and to prove I cannot win, when I photographed the 7mm GA A4s, I refused to take pictures of KING FISHER and LORD FARRINGDON, for obvious reasons. 'Trust you to notice' was the comment! 

[t-b-g]

That's one of the arguments for EM, and the dreaded "EM-2". There is a large side clearance between the flanges and the rail with 00, so even if there is little to no sideplay with the axles (there usually isn't any with pin-point axles) vehicles can still crab, a lot, and that also tends to make the flanges climb up the rails,

 

It is one of the reasons why I chose EM 35 years ago and have stuck with it ever since. Better looking than OO (or it was 35 years ago - the best OO track runs it close nowadays but I still prefer the look of locos with wheels sitting better in splashers) and more reliable than P4. A very happy middle path that I have never regretted for one moment.

 

Either reducing the gauge or increasing the back to back and adjusting checkrails can help in OO and/or whatever 16.2mm gauge is called this week.

 

I fully appreciate why people want to try new things to see if they can come up with an improvement and the hobby would never have got to the stage it has unless new developments were made.

 

But when the equipment and standards that we have available can produce the sort of running that people like Roy Jackson (in EM) and Tony W (in OO) get, then it makes me think that we just need to use what we have more effectively, rather than searching for new answers.

[Porcy Mane]

"warp" of  1 inch over a length of 8 feet. That's not very much.

 From memory, it was a 1inch drop over 8 feet that was guaranteed to derail standard suspension Palvans at anything above 25 Mph. The prototype railway had problems too.

 

P

[Tony Wright]

That statement is not correct. Sprat and Winkle couplings use the buffers of the wagons when propelling. The single centre fixed point only applies when hauling.

 

I find that the biggest problems propelling long trains over curves and points come when you have what is effectively a loco pushing some wagons against a heavy load going round a bend. It matters not what sort of couplings you use. The weight of the wagons at the far end away from the loco tend to force the wagons nearer the loco outwards on a curve as the loco pushes against them.

 

Pushing hard round a curve with a compensated wagon is more likely to cause it to tilt and give buffer height problems than a rigid wagon.

 

I have have seen some really long trains (40 plus wagons) in P4. It was many years ago on Whetstone (by Andy Gibbs - he scrapped it after a couple of shows because it never ran well - too many derailments) but I have certainly never seen one being propelled through complex pointwork. Has it ever happened?

 

I find that reliable propelling needs buffer heights to be consistent. It needs wagons to be evenly weighted (but not too heavy) and free running to reduce the forces pushing wagons sideways and it needs not too much sideplay in the axles and wheels so wagons can't "crab". This last one is where the finer scales do score over OO but it doesn't mean that it can't be done. Finally, well laid and aligned track is a big factor too.

Thanks Tony. 

 

I think Bill might be right with regard to the later-style of Sprat & Winkle couplings, which have a sort of forward-facing hook at their inner ends. But, all the ones I have use their buffers to propel - and they work very well. 

 

I think his assertion that tension-locks will cure any (my emphasis) problems in propelling P4 stock should be broadcast to the relevant societies. I'm sure they'll be delighted to find the universal panacea. Perhaps if Andy Gibbs had used them on Whetstone it might not have been scrapped. I saw it (at Manchester, I think) and though I was impressed with its overall appearance, the running left much to be desired. It seemed to be (just about) all right if trains just ran round, but any cross-over movements and (especially) shunting resulted in too many derailments. The reason? Not a tension-lock in sight.

 

I'm pleased with so many responses to the various discussions on this thread, particularly the likes of yourself, but I wonder whether much of what I post has any real relevance to many. Like you, I'm much more interested in how reliable running can be practically achieved, not by theory or silly suggestions. I've just counted up how long I've spent on the computer today, answering questions and being involved in discussions. After the second hour, it's no wonder I've done nothing of what I really wanted to do today. These tasks included continuing with my B17 build, write-up my article on building a pair of DJH Klondikes and begin a potted history of Gresley's O2s. Of course, it's a delight to take and process pictures (and post them) of friends' work, and to help the likes of less-experienced modellers in their quests. 

 

I don't have all the answers (to some, I probably don't have any), and I feel it's probably better not to say anything in many ways. I think I'll take my own advice. 

 

But, many thanks for your support. 

Edited October 28, 2015 by Tony Wright

[AndyID]

An interesting observation.

 

I have a Golden Age A4. Why I bought it, I'm not sure now, but it was originally offered to me FOC because I'd done a lot of photographs for Golden Age. I was about to write a review (which I did) and I was not prepared to take the risk of being accused of giving a favourable review. As it was, all the Golden Age OO A4s I photographed were very accurate.

 

But, and this is very interesting because the evidence is empirical. Despite its every driven axle being sprung, it is far less sure-footed than any of the three Wills/SE Finecast A4s I've built rigid. Weight-wise they're much the same, but the GA one slips violently when opened up on a heavy train, even at speed. The ones I've made just walk away with any train.

 

As a footnote, and to prove I cannot win, when I photographed the 7mm GA A4s, I refused to take pictures of KING FISHER and LORD FARRINGDON, for obvious reasons. 'Trust you to notice' was the comment! 

 

Hi Tony,

 

Just a thought:

 

Does the GA version have a bit more play in the coupling rods than the rigid chassis versions? If so, the non-geared wheels will tend to accelerate and decelerate relative to the gear driven wheels during each revolution. That's not a good thing because it forces the treads into sliding rather than static friction. Under light load it's not a problem because the rails tend to keep the wheels properly synchronized, but under heavy load the gear driven wheel-set will try to lead (get ahead of) the other wheels and periodically force them to accelerate and decelerate. 

 

One advantage of the rigid chassis is that it's possible to maintain a very strict phase relationship between all the driven wheels. Of course that only happens if everything is made very accurately.

 

Cheers!

Andy

[corneliuslundie]

Just a small comment on Sprat & Winkle couplings. It depends on what form of bar you use. I think the original idea was a piece of wire fixed across the buffers. In that situation the buffers will contact the wire (if your heights are EXACTLY the same the wires will make contact) and buffer locking is unlikely. If, like me, you use a U-shaped loop or wire fixed to (or in one case I have seen under) the buffer beam, then you are reliant on buffer contact. The over-ride part of the etch only comes into play for advance uncoupling.

 

I think the comment about outward forces on curves is very relevant. It is much more of a problem with the curves we use than with most prototype track. A relatively short train can have the loco and final vehicle at right angles or worse.

 

And re coning, I think there is a demonstration at the Science Museum or somewhere similar of a pair of cones fixed back to back running down a sloped "track". They stay on without any flanges - in fact I think there may even be a video of it on the web.

 

Jonathan

 

Edit as I posted and then realised that I had said something which was not completely true, though it does not affect subsequent comments. There are two versions of the Sprat & Winkle coupling, one without and one with the over-ride bar. I know that a good number of modellers prefer the former. However, the error was in saying that the override bar only comes into play for advance uncoupling. I should have said that on the straight and on large radius curves the contact is between the override bar and the wire but on sharp curves, when you most want to avoid it, the buffers make contact - at the very time of course when there is most likely to be buffer locking. .

Edited October 29, 2015 by corneliuslundie

[Buhar]

That (or an identical demonstration) is at NRM York.  IIRC it's two take-away coffee mugs joined at the rim.  It doesn't half hunt though!

[AndyID]

And re coning, I think there is a demonstration at the Science Museum or somewhere similar of a pair of cones fixed back to back running down a sloped "track". They stay on without any flanges - in fact I think there may even be a video of it on the web

Yes, coning is essential on real railways because it minimizes contact between wheel flanges and rails. Unfortunately, it cannot prevent flange/rail contact on typical model railway curves. It's the flanges that keep the wheels on our tracks. (If you look at the link I posted above you will see that I actually made a two-cone test "wheel" to prove the point.)

[Tony Wright]

Hi Tony,

 

Just a thought:

 

Does the GA version have a bit more play in the coupling rods than the rigid chassis versions? If so, the non-geared wheels will tend to accelerate and decelerate relative to the gear driven wheels during each revolution. That's not a good thing because it forces the treads into sliding rather than static friction. Under light load it's not a problem because the rails tend to keep the wheels properly synchronized, but under heavy load the gear driven wheel-set will try to lead (get ahead of) the other wheels and periodically force them to accelerate and decelerate. 

 

One advantage of the rigid chassis is that it's possible to maintain a very strict phase relationship between all the driven wheels. Of course that only happens if everything is made very accurately.

 

Cheers!

Andy

Thanks Andy,

 

The science-bit tends to do my head in. As I've said before, I'm really interested in the results - the result in this case being that my 'solid' A4s are much better at starting and hauling heavy trains than the GA one. Why, I don't know (nor, with the greatest of respect - because I'm old and reactionary - do I care). There is far more slop in the coupling rods, so that might contribute to the problem.

 

A few years ago, at the Glasgow Show, there was a rake of ten Golden Age Pullmans placed on a layout, which a GA A4 struggled with, yet one of my rigid DJH A1s just flew round with it. Again, why I cannot say.

 

All the best,

 

Tony.  

[Tony Wright]

Just a small comment on Sprat & Winkle couplings. It depends on what form of bar you use. I think the original idea was a piece of wire fixed across the buffers. In that situation the buffers will contact the wire (if your heights are EXACTLY the same the wires will make contact) and buffer locking is unlikely. If, like me, you use a U-shaped loop or wire fixed to (or in one case I have seen under) the buffer beam, then you are reliant on buffer contact. The over-ride part of the etch only comes into play for advance uncoupling.

 

I think the comment about outward forces on curves is very relevant. It is much more of a problem with the curves we use than with most prototype track. A relatively short train can have the loco and final vehicle at right angles or worse.

 

And re coning, I think there is a demonstration at the Science Museum or somewhere similar of a pair of cones fixed back to back running down a sloped "track". They stay on without any flanges - in fact I think there may even be a video of it on the web.

 

Jonathan

Thanks Jonathan,

 

My Sprat & Winkles have 'U'- shaped loops protruding through the wagons' headstocks. When propelled, the buffers act upon each other, not the loops.

 

I'm also a bit puzzled when folks 'disagree' with personal empirical evidence. Yesterday, I conducted some tests propelling various non-bogie vehicles of different types fitted with a variety of couplings (obviously compatible with each other). There were very few derailments (largely, I believe, because my curves are fairly generous), but where there was a derailment (on a reverse curve) it was always due to buffer-locking; not buffers causing friction between each other (both metal and plastic) but because one buffer head went behind another, and subsequently pushed one, or both, wagons off the track. This even happened with the later-style of smaller tension-lock types, where one rode over the other and then caused subsequent buffer lock, in this case one buffer riding over its neighbour (so, tension-locks are not the universal panacea for propelling ills). The most reliable coupling for propelling, I found to be the ones I made myself (which have been described in these pages). This is no more than a 'goalpost' through the headstock of one vehicle and a 'hook' through its neighbours. The buffers touch each other when being propelled. I admit it is entirely un-prototypical, but so are Sprat & Winkles, Tension-locks and Kadees on most British stock. 

 

Obviously, all the vehicles were rigid, as was the propelling locomotive. I admit I have no evidence (empirical or anecdotal) as to whether compensated/sprung stock would have derailed less-frequently under propulsion. Since the cause was buffer-locking, I doubt it.

 

Regards,

 

Tony.  

Edited October 29, 2015 by Tony Wright

[sandra]

Tony was very kind to post photos of the locomotives I took with me to operate on Little Bytham on Tuesday. These locomotives were the C2X, the A8 the O2 and the Collett 38XX. I must say that on looking at the photos that my first reaction was "could do better". My defence is that, with the exception of the 38XX, they were built between 20 and 30 years ago. I do think I could do better now and as I have started building locomotives again I may be able to post photos of my latest efforts in due course.

 

However I will say a few words about these locomotives. The C2X was built from a DJH kit which was actually purchased from the Puffers stand at the MRJ exhibition at Central Hall Westminster in (I think) 1990. It has Romford wheels and an Anchorage D11 motor and Romford gears. Even after all these years it is still incomplete as there is no front number plate, fall plate or crew. When first placed on the track at Little Bytham it did run but was very noisy. However after about 10 circuits of the layout it started to improve. It just goes to show it does really help the running of a locomotive to let it have a long run hauling a reasonable train load. I believe that this kit is still available from DJH and I would strongly recommend it as a first kit for someone who has not built a locomotive before. It goes together very well and as it does not have outside valve gear it does not present too much difficulty particularly if bought together with the DJH Motor/Gearbox and wheelset.

 

The A8 is also from DJH but it was from their days at Banbury. It has an Anchorage D13 motor and Romford wheels. I am told it would be much improved if I had used the correct LNER pattern wheels but I am afraid that when built it I did just build the kit out of the box without worrying if the kit was accurate. The same applies to the O2 which is a Wills Finecast kit given to me by a female friend as a birthday present. The kit did not come with a chassis, this had to be bought separately and when you did buy it, it was a rather inadequate white metal effort. However the locomotive still has has the white metal chassis and it does still run so I should not complain too much. I believe that the kit has been revamped by Southeast Finecast but I suspect that the latest kit does not bear too much relation to the one I built. I do know that it now has an etched chassis included because I have recently bought one to replace the chassis on this locomotive.

 

The GWR 38XX is a tender drive Hornby body on a Comet chassis. It has Romford wheels and a Comet gearbox with Mashima motor. The tender is Bachman. This locomotive was built long before the latest Hornby model was available and I think the photograph shows how poor the old Hornby tender drive effort was. The Comet chassis is extremely good and accurate, however Hornby seem to have used the chassis from their Stanier 8F as the basis for the model and as a result they have made what is quite a long locomotive even longer. The locomotive was a product of the period when Hornby was still producing models aimed at the toy end of the market rather than at the serious modeller.

 

I hope these comments are of some interest.

 

Sandra

[Barry O]

just gone through lots of posts here.. some ineteresting inputs but ...

 

hopefully Tony may see DCC in a new light if he listens to Bob Harpers' talk at Warley this year - he tried to operate his ON3/ON2 layout in dc but it was impossible so dcc is teh way he has gone and he will explain why.

 

Mike Edge fits dcc chips into kit/scratch built locos - including portescap fitted ones and these work. Like wise mugging here has fitted sound to an awful lot of DJH Duchesses, A3s, A1s, A2s etc) - in EM the use of two "sugar cubes" fitted facing down toward the track in between the frames under the chimney gives a good sound. In OO I have fitted standard round speakers in the boilers of a DJH Duke of Gloucester and DJH Britannia recently and they sound good. 

My biggest problem has been fitting sound to diesels - Heljan CoBos - the pipework falls off and there is a problem housing the speaker - I fitted it in the fuel tank after milling a part of the chassis away with my dremel end mill and a Bachmann 10000 as the prefitted system for adding the speaker is not a particularly well engineered solution.

 

It isn't just dcc which has a nasty affect on portescaps - a well known make of controller does have high frequency noise on its "dc" outputs. Due to the way the portescaps work this is not good for them.. something I learnt the hard way in the late 1980s when designing control circuits for them in a defence based application.

 

Baz