Bristol group visit Highbridge Part II

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martin goodall
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Re: Bristol group visit Highbridge Part II

Postby martin goodall » Fri Jun 15, 2012 10:50 am

I was sorry I had to miss the beer - maybe another time. Fuller's ESB puts hairs on your chest (but not so good if you are driving, so I suppose it would have to be London Pride instead).

Cheers!

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Paul Townsend
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Re: Bristol group visit Highbridge Part II

Postby Paul Townsend » Fri Jun 15, 2012 12:07 pm

I like it when the group come here as I can sink 2 pints and walk home!

At Highbridge there are over 50 wagons of the vanilla 4 wheel family. I will admit to occasional "random derailments" as Martin calls them that occur with perhaps 4 or 5 of these. They are all classic rocking compensated with a mixture of manufacturers W-irons. Years of investigating causes have failed to find a fault on them. ( I do have other occasional derailments but these are quickly diagnosed and faults cured.)

So I was pleased to invite Martin to demonstrate his 3 bogie coaches and 10 or so wagons with EM wheels. Due to incompatible couplings all the coach demo was necessarily propelling. They trundled several times on the Down GWR Main and through some complex pointwork in the fiddle yard including facing tandems, doglegs and 3 double slips. This is quite challenging! Not a single problem.

The wagon with P4 wheels that fell off in one place led to application of Mint Gauge which showed slight tightness there...easily remedied if other stock misbehaves there.

I will be laying in a small stock of Maygib EM wheels to put on those few annoying wagons, and then challenge the group on their next visit to eyeball identify the EM wagons in service :twisted:

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Noel
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Re: Bristol group visit Highbridge Part II

Postby Noel » Fri Jun 15, 2012 9:31 pm

Might be more interesting to challenge us to find out what the problem is with the wagons, then you wouldn't have to resort to such heinous un-P4 activities :twisted:. You never know, we might be as clever as we always say we are :geek:!
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LesGros
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Re: Bristol group visit Highbridge Part II

Postby LesGros » Fri Jun 15, 2012 10:06 pm

paultownsend wrote:
...The wagon with P4 wheels that fell off in one place led to application of Mint Gauge which showed slight tightness there...easily remedied if other stock misbehaves there...
:o
Surely, if the mint gauge showed a tight spot, a correctly set up P4 wheelset should be expected to fall off, or shuggle. In which case the solution is to deal with the tight spot... Or have I misunderstood the purpose of P4 standards? :?
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Paul Townsend
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Re: Bristol group visit Highbridge Part II

Postby Paul Townsend » Sat Jun 16, 2012 10:33 am

Noel wrote:Might be more interesting to challenge us to find out what the problem is with the wagons, then you wouldn't have to resort to such heinous un-P4 activities :twisted:. You never know, we might be as clever as we always say we are :geek:!


I will bring some rogues to Gordon's at next opportunity so we can see them on the test track and advise.

Doubtless someone will say, abandon compensation and use springing.
Oblox to that :!:

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Paul Townsend
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Re: Bristol group visit Highbridge Part II

Postby Paul Townsend » Sat Jun 16, 2012 11:00 am

LesGros wrote:Surely, if the mint gauge showed a tight spot, a correctly set up P4 wheelset should be expected to fall off, or shuggle. In which case the solution is to deal with the tight spot...:?


Well yes, but 70 of my wagons traverse it OK as do 25 + bogie coaches that regularly trundle over it.
The only item to fall off was Martin's visiting P4 wheeled wagon.
This is probably all down to tolerances....it is likely that Martin's wagon is on the wide end of the B-B tolerance or even a smidgeon outside which would make it particularly sensitive to minor track faults....in the rush for London Pride we didn't check it here. Maybe Martin will do so and comment.

The 3" length of straight track with very slightly tight gauge has been confirmed as 18.80 so WILL get attention as already noted...it is just enough to be felt when sliding with the wonderful Mint whereas my Studiolith triangle gauges as used for construction feel normal.

LesGros wrote: Or have I misunderstood the purpose of P4 standards? :?


No

PS my wagons don't shuggle even after 4 London Pride!

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Tim V
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Re: Bristol group visit Highbridge Part II

Postby Tim V » Sat Jun 16, 2012 12:02 pm

Since it was the one wagon, I would suspect Martin's wagon....
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Re: Bristol group visit Highbridge Part II

Postby JFS » Sat Jun 16, 2012 12:58 pm

Paul,

paultownsend wrote: Years of investigating causes have failed to find a fault on them. ( I do have other occasional derailments but these are quickly diagnosed and faults cured.)


As one with an engineering background, unsolved mysteries always bug me and have caused me over the years to perhaps look for things which are not always on "the list".

I wonder if you are able to put your hands on these particular troublesome trucks and perhaps check a couple of things which I have found to be potential causes of "random derailments" (not that I have thousands of wagons nor miles of track you understand!).

Firstly, slackness of the wheelset - caused by either the axle having endfloat within the bearings (which is really difficult to eliminate) or by the rocking w iron having a degree of rattle around its pivot mechanism. (personally, I would rather chance an uncompensated wagon than a "dodgy" rocking w iron)

Secondly, the wheels not being exactly fore and aft of each other - in other words, if you put a straight edge across the face of one wheel, it would not align exactly with the face of the wheel on the other axle. One obvious cause of this would be that the axles are out of parallel (but that would not apply to your wagons - nor mine!) but a more intractable cause is that when we tweak the back to back, we move the wheels along the axles to some small degree, until they eventually become out of line.

Of course, you have probably checked and eliminated such issues long ago!

I wonder if anyone else could contribute other "further things to check"??

I have to be honest and say that when I first read Martin's idea of using pushed out EM wheels I - no doubt like others - scoffed. Now I am much less sure - t might be much easier to substitute EM Wheels than sort out the tiny issues :D

Best Wishes,

Howard.

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Captain Kernow
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Re: Bristol group visit Highbridge Part 2

Postby Captain Kernow » Sat Jun 16, 2012 4:04 pm

Tim V wrote:A further visit last night.
After all what one gets up to in the privacy of ones own home won't hurt the S4 society....


Excellent!!

Rock on, Tommy! :D :D ;)
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martin goodall
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Re: Bristol group visit Highbridge Part II

Postby martin goodall » Sun Jun 17, 2012 4:36 pm

I have just checked the errant P4 cattle wagon with the electronic digital calipers (a tenner from Maplins), and the back-to-back of the two wheelsets was 17.70 mm and 17.86 mm respectively.

But the point of the exercise last week was to see how the EM wheels behaved. They gave no problems. The P4-wheeled wagon was not there for comparison, but simply as a 'match wagon' to allow the rake to be coupled up to a loco (as my couplings are inconsistent with anyone else's). I just haven't got round to replacing the P4 wheelsets in that wagon yet.

As I mentioned during the running session, it causes me great amusement that some people get so worked up about anyone departing from the sacred P4 standards. I just enjoy doing what I do, and if it winds up other people, that just adds to the fun.

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Paul Townsend
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Re: Bristol group visit Highbridge Part II

Postby Paul Townsend » Sun Jun 17, 2012 6:47 pm

martin goodall wrote:I have just checked the errant P4 cattle wagon with the electronic digital calipers (a tenner from Maplins), and the back-to-back of the two wheelsets was 17.70 mm and 17.86 mm respectively.


Ta for that. The 17.86 IS outside P4 standard range but is just inside the "4mm scaled prototype" dimension used by some bods.
Thus it is not surprising that with wide B-B and narrow TG all tolerance was soaked up and wagon fell off. It is more surprising that it didn't misrun elsewhere!

Nevertheless, as you say this was a side issue from EM wheel evaluation, but it did show up a dodgy bit of my track so I am glad it happened.

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Re: Bristol group visit Highbridge Part II

Postby martin goodall » Mon Jun 18, 2012 11:57 am

This does in fact raise a interesting point.

As Paul has remarked, the 17.86 setting is just within the maximum permissible BB (and, from memory, is somewhere near the figure used in the 'Scale Four' standards, as Paul also observed). In fact, it is quite possible that I originally set the BB on this set of wheels using a 'Scale Four' BB gauge, as I did experiment with those standards some years ago. A wheelset which is set to the 'Scale Four' BB should run perfectly happily on P4 track, in fact slightly better than if set to the P4 BB, as it has less opportunity to 'hunt' - i.e. the running clearance (between the outside of the flange and the rail head) is significantly less than it would be if set to the P4 BB gauge.

Now we come to the interesting bit. EM wheels not only have deeper flanges than P4 wheels, but the flanges are also fatter. When set to the P4 BB gauge, the running clearance for EM wheels on P4 track is virtually identical to what it would be for a P4 wheelset if set to the 'Scale Four' BB gauge. So the running clearance on the other (EM-wheeled) wagons we tried out on Paul's layout must have been pretty-well the same as on the 'wide' P4 wheelset on the W3 cattle wagon. Yet the other wagons showed no sign of distress when running through the slightly under-gauge crossing. In theory, they should have experienced the same problem, but it seems that the deeper flanges were enough to avoid any potential derailment, whereas one of the P4 wheelsets under the cattle wagon de-railed.

I should also mention that when I said that none of the wagons had compensated suspension, that only applied to the EM-wheeled wagons. The P4-wheeled W3 cattled wagon has a rocking W-iron - probably the most commonly used method of compensation.

Does this possibly suggest another reason for using EM wheels in preference to the orthodox P4 wheel profile? :twisted:

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Re: Bristol group visit Highbridge Part II

Postby Horsetan » Mon Jun 18, 2012 12:03 pm

martin goodall wrote:......Does this possibly suggest another reason for using EM wheels in preference to the orthodox P4 wheel profile? :twisted:



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Re: Bristol group visit Highbridge Part II

Postby iak » Mon Jun 18, 2012 12:08 pm

I am going to try this and damn the torpedoes... :D
I'm no engineer but I'm intrigued...
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Tim V
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Re: Bristol group visit Highbridge Part II

Postby Tim V » Mon Jun 18, 2012 3:41 pm

martin goodall wrote:This does in fact raise a interesting point.
Now we come to the interesting bit. EM wheels not only have deeper flanges than P4 wheels, but the flanges are also fatter. When set to the P4 BB gauge, the running clearance for EM wheels on P4 track is virtually identical to what it would be for a P4 wheelset if set to the 'Scale Four' BB gauge. So the running clearance on the other (EM-wheeled) wagons we tried out on Paul's layout must have been pretty-well the same as on the 'wide' P4 wheelset on the W3 cattle wagon. Yet the other wagons showed no sign of distress when running through the slightly under-gauge crossing. In theory, they should have experienced the same problem, but it seems that the deeper flanges were enough to avoid any potential derailment, whereas one of the P4 wheelsets under the cattle wagon de-railed.
:twisted:

I find this worrying Martin.
1. That wagon should have had it's BB setting checked as a matter of routine. Just changing the wheels to EM ones means you've not got to the bottom of the problem with your stock.
2. As the EM wheels are on the limit of the over flange width, it reminds me why the society recommends the P4 BB as postulated by the MRSG, as opposed to the "correct" BB used by Ray Hammond. Because of our use of sharper curves, the MRSG went for the reduced BB. We'll have to try the same stock round Clutton's 3' radius curves.
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Re: Bristol group visit Highbridge Part II

Postby grovenor-2685 » Mon Jun 18, 2012 4:11 pm

it reminds me why the society recommends the P4 BB as postulated by the MRSG, as opposed to the "correct" BB used by Ray Hammond. Because of our use of sharper curves,
Not just the use of sharper curves but more importantly the provision of practical tolerances, for manufacturing error, wheels out of true, track construction accuracy etc. which are inevitably proportionally much greater than the prototype. Working to strict prototype dimensions, while proved possible by Ray and others needs significantly more care in checking everything is correct. Using EM wheelsets removes some of this tolerance in relation to gauge and BB settings but perhaps adds a bit more tolerance of line and level errors. Take your choice. One of the primary objectives of P4 was to enable use of scale wheels, using bigger flanges is IMHO a backward step. I would also note that the max. BB to comply with P4 standards is !7.75 mm. 17.86 mm is well outside the standard and can be expected to give trouble unless the track is modified to suit, this is a faulty vehicle issue not a faulty standard issue.
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Re: Bristol group visit Highbridge Part II

Postby Philip Hall » Mon Jun 18, 2012 5:02 pm

Using a B-B gauge set to the bottom end of the P4 standards has been my practice all along. The principle advantage of so doing has always (to me) been that there is a little more play between the railheads, which in turn means that when a wheelset is out of true ( ie wobble) the effects are less evident and less troublesome. However good your workmanship in the first place, wheels can and do move on axles and unless you want to be always checking and adjusting, which I don't, a little more tolerance is a good idea. I know this may not seem like The One True Path, where as much as you can manage is exactly to scale, but I want a layout (like Tim) that consistently runs reliably and with much the same occurences of stock in the ballast as did the prototype.

I think Martin has some valid points, and a little bit extra in the depth of the flange is no bad thing in some cases, so long as the flange isn't any thicker. This is where I differ from Martin, as the thicker EM flange does take us straight back to the 'slightly less slop' situation that you would have with P4 wheels set to the maximum B-B. I know Martin is using Ultrascale and Kean Maygib wheels, which don't generally wobble, but there's still no allowance for movement.

One of the best articles I ever read on reliable running was a piece by W E Ward-Platt in an early Railway Modeller. An October issue, I think (it had a dark blue border), maybe 1965. I'll look it up when I've posted this. He worked to EM and jigged the standards around where he could see they didn't work. Perhaps we wouldn't need to go to the lengths he did, but he was firmly of the opinion, backed up by extensive testing with heavy trains, was that however accurate a wheelset may be when you set it up, it will move, and a slight wobble can result. And we have to accommodate that movement.

Philip
Last edited by Philip Hall on Mon Jun 18, 2012 8:49 pm, edited 1 time in total.

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Re: Bristol group visit Highbridge Part II

Postby Tim V » Mon Jun 18, 2012 5:45 pm

That article is also on my bookshelf, October 1965. A useful article.
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Re: Bristol group visit Highbridge Part II

Postby Will L » Mon Jun 18, 2012 6:18 pm

I can't say I'm surprised that you get a more tolerant wheel by using an increased flange depth, or presumably OO/EM wheels wouldn't have them. Although as they have thicker flanges than a P4 wheel, use through through P4 point work means the tolerances on the Back to Back setting will be tighter. You can avoid that problem by increasing the flange way a bit.

EM standards may be just what Martin is looking for.

Will
Last edited by Will L on Mon Jun 18, 2012 9:22 pm, edited 1 time in total.

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Paul Townsend
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Re: Bristol group visit Highbridge Part II

Postby Paul Townsend » Mon Jun 18, 2012 6:19 pm

Tim V wrote:That article is also on my bookshelf, October 1965. A useful article.

Bring tomorrow night?

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Re: Bristol group visit Highbridge Part II

Postby Tim V » Mon Jun 18, 2012 6:27 pm

Mark's tomorrow.
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Re: Bristol group visit Highbridge Part II

Postby Philip Hall » Mon Jun 18, 2012 9:06 pm

Will L said


I can say I'm surprised that you get a more tolerant wheel by using an increased flange depth, or presumably OO/EM wheels wouldn't have them. Although as they have thicker flanges than a P4 wheel...


I am quite happy with the usual P4 profile, but at the risk of opening a whole new can of worms, I have always thought an ever so slightly deeper (say .005") P4 flange would be of benefit in extreme conditions, which on a model we are more likely to have where tight curves are concerned. I think one or two people have done this already when turning their own wheels and reported no adverse effects and some benefits. But the standard profile works well, so for me it would merely be an experiment.

Philip

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Will L
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Re: Bristol group visit Highbridge Part II

Postby Will L » Mon Jun 18, 2012 9:22 pm

Philip Hall wrote:
Will L said


I can say I'm surprised that you get a more tolerant wheel by using an increased flange depth, or presumably OO/EM wheels wouldn't have them. Although as they have thicker flanges than a P4 wheel...




Oh B*****r these is a missing "'t" That should read
I can't say I'm suprised...
and it does now.

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Re: Bristol group visit Highbridge Part II

Postby martin goodall » Tue Jun 19, 2012 1:55 pm

Picking up on the points made by Tim and others, I have never had a problem with my stock. The derailments I experienced when using P4 wheels were few and far between, but they were random and untraceable. If there is a problem with a particular vehicle or with a particular piece of track, the problem will repeat itself until the fault is dealt with. The type of incident I had in mind was truly random and could not be repeated.

I came to the conclusion that the microscopic flanges on P4 wheels may occasionally lead to a combination of factors which can cause a derailment where a wheel with a deeper flange would not do so. Compensated suspension or springing, plus moderate weight (say roughly 25g per axle) obviously helped, but could not eliminate the gremlins altogether.

There were other factors which encouraged me to try out EM wheels. First and foremost was a desire to avoid the time-consuming business of arranging for compensated suspension, which on some kits can involve quite drastic surgery. Another consideration was the desirability of cutting down on the tendency of vehicles to ‘hunt’ on the track (due to the over-generous running clearance in P4).

As Ray Hammond convincingly demonstrated, and others who follow ‘Scale Four’ standards can confirm, there are advantages in pushing out the BB setting of P4 wheels to the permissible maximum, thereby reducing the running clearance. Contrary to what many people seem to believe (but have never bothered to find out for themselves), this causes no problems at all. The over-generous running clearance in P4 was devised to cater for the unlikely event of someone wanting to run a ‘King’ or ‘Castle’ through a B6 crossover [i.e. a tightish reverse curve] (something that would never be attempted on the prototype). Such a generous running clearance is entirely unnecessary on plain track, even if it is curved down to 3-foot radius. Tim will encounter no problems on ‘Clutton’ whether he uses either P4 wheels set to the ‘Scale Four’ back-to-back gauge or EM wheels set to the P4 back-to-back. As I mentioned the other day, the running clearance will be nearly identical in both cases.

Keith’s remarks on this same point might have some validity if they were based on empirical evidence. The theoretical elimination of tolerances might be expected to lead to the sort of problems Keith predicts. But in practice, they don’t. I can confirm this from practical experience (in relation to the use of EM wheels), and I am not aware of the users of ‘Scale Four’ standards having encountered any problems in practice.

Philip expressed concern about the use of thicker flanges which, as he correctly observes, gives 'slightly less slop' than you would have with P4 wheels (but not if you set the P4 wheels to the maximum B-B – as I mentioned above, the running clearance is virtually the same for EM wheels set to the P4 back-to-back as it is for P4 wheels set to the ‘Scale Four back-to-back dimension). Philip is right in pointing to the quality of Ultrascale and Kean Maygib wheels, but I also use Alan Gibson EM wheels, and they have given no trouble either – if I have any reservations about them (apart from an occasional lack of concentricity), it relates to the turning of the tyre treads, which is not quite so smooth as the other makes, and so they seem not to roll so freely. However, my own experience has shown me that Philip (and others) need have no worries about a lack of allowance for movement. It has never caused me any problem in practice, nor (so far as I am aware) has it troubled the users of ‘Scale Four’ standards.

Incidentally, I too read W E Ward-Platt’s article in the Railway Modeller in 1965, and it was one of the factors which influenced me a few years later to pursue finescale standards.

Turning to Will’s comment, it has to be very clearly borne in mind that if a wheelset is set to the P4 back-to-back gauge, the clearance behind the wheel as it traverses P4 pointwork will be exactly the same, whatever its flange profile. It is the running clearance (on the outside of the wheel) that is reduced. Thus there is absolutely no need to increase the flangeway or check rail clearances, and it wouldn’t make a scrap of difference if you did. My track is all built to the standard P4 settings, and I have not eased the clearances in any way.

If EM wheels had proved to be a tight fit through P4 pointwork, I would have abandoned the experiment immediately. On the contrary, they sailed though without the slightest indication of any difficulty. As I explained some months ago, the only problem I encountered (which, as it happened, was solely on plain track) was that these EM wheels would bump or jump (but could not be persuaded to derail) if they encountered a spot where the track gauge was slightly less than 18.83mm. Use of a roller gauge quickly identified one or two places on the layout where this had occurred (despite careful use of track gauges when building the track) and these were quickly eliminated. No other adjustment has ever been required.

There is no need to resort to EM track standards, which leave a grossly over-generous running clearance, with an even greater propensity of wheels to ‘hunt’ than on a P4 layout. I am satisfied that EM wheels set to the P4 back-to-back gauge, running on track laid to orthodox P4 standards is the perfect combination. The extra depth and width of the flanges are both advantageous features of this combination. The result is faultless running with uncompensated stock, saving time and hassle all round.

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Will L
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Re: Bristol group visit Highbridge Part II

Postby Will L » Tue Jun 19, 2012 5:09 pm

I'm afraid you missed my point Martin.

While I'm all for not getting judgemental over the little perversions others may chose to practice in their railway room, what your suggesting may work, may be easier to make work, but it isn't P4.

Going P4 was all about NOT making the sort of compromises implied by the use of EM /00 profile wheels. I can accept you might have a point if you suggested the implication of this should be going the Ray Hammond rout.

Will


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