Turnout construction - Question here please.

Discuss the prototype and how to model it.
petermeyer
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Re: Turnout construction - Question here please.

Postby petermeyer » Mon Sep 14, 2020 6:42 am

Its a while since I built turnouts but from what I remember the chairs are labelled on the sprue and the switch chairs are all included.

Either that, or there is an Exactoscale template that explains it. I think the old Exactoscale site is still active.

You will also need slide chairs, standard and other chairs that are not included in that pack depending on what you are building.

TEZBEDZ
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Re: Turnout construction - Question here please.

Postby TEZBEDZ » Mon Sep 14, 2020 8:22 am

Thanks I didnt think Exactoscale was still going. Will do some googling
Regards

Terry

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Will L
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Re: Turnout construction - Question here please.

Postby Will L » Mon Sep 14, 2020 8:35 am

TEZBEDZ wrote:Thanks I didnt think Exactoscale was still going. Will do some googling

See https://exactoscale.com/track-component ... positions/

Tony Wilkins
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Re: Turnout construction - Question here please.

Postby Tony Wilkins » Wed Dec 09, 2020 10:41 am

Just bumping this thread in case anyone is having difficulty finding it.
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Julian Roberts
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Re: Turnout construction - Question here please.

Postby Julian Roberts » Sun Dec 13, 2020 9:38 am

Hi Tony
Many thanks for the latest instalment on diamonds and slips.

One thing I didn't understand is how to use a check rail gauge when adjusting the fit of the first point rail.

Adjusting the fit of the first point rail using the wrong gauge. The check rail gauge should really be used but this is easier when making the initial fit.

SS9 Adjusting initial fit of point rail using wrong gauge.jpg



(The actual photo doesn't copy over to this)

Do you have any advice on the filed tip of the point rail - should it be slightly rounded as with a crossing V?

The other thing I'd like to ask is about the S4/P4 difference, as you model in S4. I'm not sure you've said this on the thread, could you confirm that a 1:8 is the flattest angle allowed on the prototype and thus in S4, because of the unchecked length? What is the flattest in P4 to give the same safety margin? Similarly, the table of curving diamonds must be slightly more restrictive in P4?

Lastly, ideally could that table of curves include a conversion to scale mm (or perhaps a link to John Donnelly's conversion thingy which was on the Forum recently?)

Tony Wilkins
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Re: Turnout construction - Question here please.

Postby Tony Wilkins » Mon Dec 14, 2020 9:17 am

Hi Julian.
I will come back to you on this if I may as there are several questions here and I need to think about some of them.
Regards
Tony.
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Julian Roberts
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Re: Turnout construction - Question here please.

Postby Julian Roberts » Tue Dec 15, 2020 11:31 am

Hi Tony
No problem, thanks for giving some time to consider. I don't subscribe to the modern expectation that we give instant responses in this age of electronic communications ;)

Tony Wilkins
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Re: Turnout construction - Question here please.

Postby Tony Wilkins » Tue Dec 15, 2020 1:56 pm

Julian Roberts wrote:Hi Tony
Many thanks for the latest instalment on diamonds and slips.

One thing I didn't understand is how to use a check rail gauge when adjusting the fit of the first point rail.

Adjusting the fit of the first point rail using the wrong gauge. The check rail gauge should really be used but this is easier when making the initial fit.

SS9 Adjusting initial fit of point rail using wrong gauge.jpg



(The actual photo doesn't copy over to this)

No, I can never get them to copy over either.
If one thinks about how a Check rail gauge is intended to be used to measure the distance between the check face of a rail and the running face of the opposite rail, it becomes apparent that in this situation there is no rail to measure it from. Hence my comment about using the Crossing Flangeway gauge to help temporarily set the first point rails. I fully expect further adjustments to be required in the alignment of the point rails, indeed the likelihood of getting them spot on first go is rather small.

Do you have any advice on the filed tip of the point rail - should it be slightly rounded as with a crossing V?

I make the Obtuse Crossing point rails the same way as I do for Acute crossing point rails except that for certain circumstances I make the end of the nose thinner than normal to help reduce the unchecked distance. I tend to make the obtuse check bends sharper than they should be for the same reason.

The other thing I'd like to ask is about the S4/P4 difference, as you model in S4. I'm not sure you've said this on the thread, could you confirm that a 1:8 is the flattest angle allowed on the prototype and thus in S4, because of the unchecked length? What is the flattest in P4 to give the same safety margin? Similarly, the table of curving diamonds must be slightly more restrictive in P4?


This is an interesting question and the one I really had to think about.
Yes my own track is all built to S4 standards, but the same methods described are generally related to P4 standards.
Obtuse crossings are perhaps the situation where the difference can make itself most felt.
You are correct in as much as 1:8 fixed obtuse crossings are the flattest that are allowed on the prototype, flatter angles being of the switched type only, but that is only a partial answer as the situations is complicated where curves are concerned as already discussed.
Since S4 dimensions mirror the prototype, there is no reason why S4 track should perform any differently to the full size in any given situation.
The same cannot be said of P4 track however.
The S4 flangeways are 0.58mm and for the maths assuming a sharp end to the fine point, for a 1:8 obtuse crossing, the gap will be 0.58 X 8 = 4.64mm.
For P4 flangeways at 0.68mm the corresponding gap will be 5.44mm. To reduce this gap to 4.64mm requires a crossing angle of 1:6.82, so even a 1:7 crossing does not give the same level of security in P4 as a 1:8 does in S4.
This result was greater than I expected before I did the sums.
Lastly, ideally could that table of curves include a conversion to scale mm (or perhaps a link to John Donnelly's conversion thingy which was on the Forum recently?)


Not sure I can help with a link but I will see what I can do with the my construction thread.
EDIT: 4mm equivalents now added.
Regards
Tony.
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grovenor-2685
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Re: Turnout construction - Question here please.

Postby grovenor-2685 » Tue Dec 15, 2020 3:43 pm

There is a lot of misconception about the non use of a crossing flangeway gauge for checkrail gaps.
The standards are such that, with nominal guage track the crossing flangeway and check rail flangeway are equal and hence the CF gauge can be used for both. Which is what the prototype does when fixing the check rail to the stockrail with standard spacer blocks to give 45 mm flangeway. The need to gauge from the opposite rail only applies where there is gauge widening. Making straight diamonds there should be no gauge widening so the CF gauge should be correct for all 4 point rails and as mentioned its very difficult to use a check gauge at that location anyway. When making curved diamonds of a small enough radius to need gauge widening then you are in a different ball game and quite a bit of trial and error may be needed to get reliable running but it can be done.
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Martin Wynne
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Re: Turnout construction - Question here please.

Postby Martin Wynne » Tue Dec 15, 2020 4:56 pm

grovenor-2685 wrote:Which is what the prototype does when fixing the check rail to the stockrail with standard spacer blocks

Indeed, but when drilling and fixing the check rail chair to the timber, it is the check rail which is gauged from the opposite rail, not the stock rail.

In effect what this means is that yes, it is ok to use the CF gauge to set the check rail gap, but only if you fix the check rail first and use the CF gauge to set the stock rail from it.

In practice it is not that simple, but for an ordinary turnout quite a few model track builders like to fix the turnout-side check rail first (using the check gauge from the V-crossing), before adding the turnout-side stock rail.

If you do it the other way and use the CF gauge to set the check rail, you need to be sure that the stock rail is set exactly to gauge, otherwise you will be compounding any errors.

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Martin Wynne
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Re: Turnout construction - Question here please.

Postby Martin Wynne » Tue Dec 15, 2020 5:27 pm

Tony Wilkins wrote:You are correct in as much as 1:8 fixed obtuse crossings are the flattest that are allowed on the prototype, flatter angles being of the switched type only, but that is only a partial answer as the situations is complicated where curves are concerned as already discussed.
Since S4 dimensions mirror the prototype, there is no reason why S4 track should perform any differently to the full size in any given situation.
The same cannot be said of P4 track however.

There are 2 ways to improve the checking at fixed K-crossings:

1. use a deeper wheel flange.

2. raise the check rail above the level of the running rails, as is done nowadays on the prototype.

When the originators of P4 decided to increase the flangeway gap by 17%, they could usefully have made a corresponding increase in the flange depth to allow for the situation at K-crossings. They didn't, but that still leaves the option of raising the check rail, for example by using code 100 flat-bottom rail with the foot filed off.


Image

Image

Shows only the wheel flange, rest of wheel omitted. More words and music about these diagrams at:

https://85a.co.uk/forum/view_topic.php? ... d=6#p31536

N.B.

a. do not use raised check rails with locomotives having flangeless driving wheels. This is now causing route restrictions for some preserved locomotives running on Network Rail.

b. in the case of slips, the ends of raised check rails will need to be cut down where it is possible for the outer edge of a wheel running on the slip road to catch against them. This is sometimes done on the prototype even with normal check rails, to allow for future wear of the slip rail.

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grovenor-2685
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Re: Turnout construction - Question here please.

Postby grovenor-2685 » Tue Dec 15, 2020 7:43 pm

Martin Wynne wrote:
grovenor-2685 wrote:Which is what the prototype does when fixing the check rail to the stockrail with standard spacer blocks

Indeed, but when drilling and fixing the check rail chair to the timber, it is the check rail which is gauged from the opposite rail, not the stock rail.

Have you seen that done Martin? I've not seen P-way men with other than a standard track gauge that only measures beteen running edges. Why would they use a different gauge when the one they have gives identical results?

There are 2 ways to improve the checking at fixed K-crossings:

1. use a deeper wheel flange. etc.

But is this a real problem that needs addressing? Diamonds have not been problematic in my experience.
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Keith
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Martin Wynne
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Re: Turnout construction - Question here please.

Postby Martin Wynne » Tue Dec 15, 2020 8:14 pm

grovenor-2685 wrote:Have you seen that done Martin? I've not seen P-way men with other than a standard track gauge that only measures between running edges. Why would they use a different gauge when the one they have gives identical results?

Hi Keith,

Not with my own eyes, no. I will try to find the reference in the track maintenance manuals. Bear in mind that some check chairs are designed to provide gauge-widening, usually available in three different widths. Those chairs can't be fixed or checked with a standard track gauge bar. The only way is with a check gauge bar.

There are 2 ways to improve the checking at fixed K-crossings:
1. use a deeper wheel flange. etc.

But is this a real problem that needs addressing? Diamonds have not been problematic in my experience.

I didn't say it needed addressing necessarily, I was simply responding to Julian's questions. But some folks do have problems with diamonds, especially when built on a curve.

The prototype obviously thinks it needs addressing, now that some cast K-crossings are made with raised check rails.

cheers,

Martin.
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grovenor-2685
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Re: Turnout construction - Question here please.

Postby grovenor-2685 » Tue Dec 15, 2020 8:23 pm

Martin Wynne wrote: Bear in mind that some check chairs are designed to provide gauge-widening, usually available in three different widths. Those chairs can't be fixed or checked with a standard track gauge bar. The only way is with a check gauge bar.
cheers,
Martin.

But then you choose the check chairs according to the gauge widening and hence set the running rail to that figure, track gauges are usually adjustable or can use spacers so can still be used. In reality gauge widening in S&C is rare, the special chairs are mostly for continuous check rails on curves.
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Julian Roberts
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Re: Turnout construction - Question here please.

Postby Julian Roberts » Wed Dec 16, 2020 1:18 pm

Hi Tony

Thank you and Martin for all this helpful material.

grovenor-2685 wrote:But is this a real problem that needs addressing? Diamonds have not been problematic in my experience.


A friend who has exhibited his P4 layout many times didn't know his wagons could go the wrong way on his 1 in 8 slip till I asked him the other day to see if they would. They never have done in practice. But from the above it is clear that on the P4 model we rely on perfect alignment between 8 and 7 (6.82 to be exact), which is what I wanted to know for sure. Unless we take measures such as Martin has suggested.

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Re: Turnout construction - Question here please.

Postby Tony Wilkins » Wed Dec 16, 2020 2:44 pm

Julian Roberts wrote:Hi Tony

Thank you and Martin for all this helpful material.

grovenor-2685 wrote:But is this a real problem that needs addressing? Diamonds have not been problematic in my experience.


A friend who has exhibited his P4 layout many times didn't know his wagons could go the wrong way on his 1 in 8 slip till I asked him the other day to see if they would. They never have done in practice. But from the above it is clear that on the P4 model we rely on perfect alignment between 8 and 7 (6.82 to be exact), which is what I wanted to know for sure. Unless we take measures such as Martin has suggested.


Hi Julian.
I don't know that you can necessarily draw such a hard and fast conclusion as that from the figures I quoted. What my statement inferred was hypothetically comparing a 1:8 S4 obtuse crossing to one with a similar degree of checking using P4 standards. The other major variable (as has already been mentioned) is the size of the wheel and its corresponding flange length below rail level. Obviously the smaller the wheel the shorter the flange length available for checking and guidance. Therefore wagon and similar sized wheels are likely to be the first to reach a potentially critical situation. But it is difficult to work out when exactly that would be reached as there are so many variables that could impact the result. It could be derived empirically I suppose but just because one wheel set behaves in a particular way does not necessarily mean that they they all would.

I think though you are correct that often we rely on the wheel sets continuing in a straight line over the critical areas of trackwork without realising it. I have had experience of rolling stock behaving in situations where perhaps it shouldn't. The situation gets worse with the wider flangeways used in other standards.
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Tony.
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Re: Turnout construction - Question here please.

Postby davebradwell » Wed Dec 16, 2020 4:37 pm

For a long time I've felt that securing Jackson couplings to the opposite end of the vehicle can contribute to problems at crossings and elsewhere, particularly with longish or poor running trains and now use a pulling post behind the nearest axle as in MRJ 223. I suppose propelling round curved diamonds would be another difficult move as contact on a single buffer will impart a turning moment trying to push the vehicle down the wrong road.

Can't say I'd be comfortable knowing a vehicle could go down the wrong hole. It seems a bad place to start.

DaveB

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Re: Turnout construction - Question here please.

Postby Tony Wilkins » Wed Dec 16, 2020 8:37 pm

davebradwell wrote:For a long time I've felt that securing Jackson couplings to the opposite end of the vehicle can contribute to problems at crossings and elsewhere.
DaveB

Hi Dave.
I have often thought the same in spite of using them that way and for that reason try to attach the wire on the center line of the wagon if possible. The acid test will be when I can run really long trains on Brimsdown.
At the risk of going off at a tangent.
It came as something of a suprise to discover that full size wagons used a similar system with the coupling hooks at each end being linked by a long rod with a spring arrangement in the center taking all the draw gear forces thus effectively towing each wagon along by the rear coupling plate. I presume this was done to reduce the internal forces applied to wooden underframes as the practice was largely discontinued with steel underframed wagons.

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Re: Turnout construction - Question here please.

Postby davebradwell » Wed Dec 16, 2020 9:07 pm

At least the prototype arrangement guided the hook at the front so there was a tendency to pull towards the track centre. With Jacksons installed by the book and no front guide it's an unstable arrangement, especially on curves where the couplings follow the chord. Sorry for deviation but I was pointing out the existence of devilish forces trying to make a vehicle go the wrong way.

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Re: Turnout construction - Question here please.

Postby Julian Roberts » Thu Dec 17, 2020 12:50 pm

I haven't had those wagon problems nor any other on my very short test trains (just one buffer in contact) on my trial curved diamond even with a very heavy load - does the length of a train make a difference I wonder?

Having been thinking about obtuse crossings the last three weeks, I've just one more poser, which comes in this drawing

SRE42L 1 in 7.5 Obtuse Crossing.JPG
SRE42L 1 in 7.5 Obtuse Crossing.JPG (75.42 KiB) Viewed 1482 times


What stands out to me is 1. the curve at the middle on the knuckle of both the stock rails and check rails. Surely this will decrease the checked length? So why is that OK on the prototype - don't the same issues apply? and 2. do I detect a shaping of the point rails so that their ends are not actually on the gauge line, nor the check line? I've exaggerated this here - this is looking at the right point rail in the previous drawing:

Shape of point rail.jpg


The top drawing is what I have been trying to do, shortened till there is enough strength, the lower is what the prototype drawing might be showing? If so, that is the opposite of what Iain Rice suggests here, and which I've borne in mind.
20201217_120948.jpg
20201217_120948.jpg (16.12 KiB) Viewed 1481 times


Obviously in 4mm scale the difference would be minute, but perhaps worth bearing in mind, as we're talking about a few thou here and there making the difference in P4.

Going back to the knuckle and stock rail curve, I surmise that the jarring that might occur with a sharper bend would be more detrimental to the route of the wheel than the possible decrease in checked length...?
Last edited by Julian Roberts on Thu Dec 17, 2020 2:49 pm, edited 1 time in total.

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Martin Wynne
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Re: Turnout construction - Question here please.

Postby Martin Wynne » Thu Dec 17, 2020 1:25 pm

Hi Julian,

The knuckle bend radius in the K-crossing rails (and at the wing rail knuckle in V-crossings) serves the same purpose as the flared end on a check rail.

So that a wheel back coming under control of the check rail does so progressively as it first makes contact.

Likewise the front of a wheel flange running against the rail head can progressively make contact with the wing rail (the running rail) after crossing the flangeway gap.

There is a drawing showing the machining of K-crossing point rails in the NERA reprint book. I will get it scanned later and post it.

For the best running, always take a few thou off the top of the nose of crossing vees and point rails to allow for the coning angle on the wheels as they run along the wing rail. And round over the filed running edge to match the the top corner 1/2" radius on the rail section.

cheers,

Martin.
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David Thorpe
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Re: Turnout construction - Question here please.

Postby David Thorpe » Sat Dec 19, 2020 7:19 pm

Isn't all this ply and rivet construction just a bit old hat now? Surely most people are using Exactoscale or C&L chairs and sticking them directly to the sleepers and I'd certainly like to see a bit more about how that is done, including the positioning of chairs in the more awkward areas and ensuring there is no gauge widening. For those that are using ply and rivet, I assume that you are then having to apply cosmetic chairs and I'd be interested to know how you go about that. I've found it something of a nightmare as the holes in the base of Exactoscale chairs are just a little bit smaller than the head of the rivet in the sleeper which means that in order to get a close fit of the chair it is necesary to file away some of its base. Doing that for all the chairs - or more accurately all the half chairs -in a turnout is an extreme pain, especially when a rivet is not directly under the rail or ones soldering is not as minimal as might be hoped.

I cannot help but think that anyone contemplating starting out in P4 who then reads this page will gain the imoression that trackwork construction in P4 is exceptionally complicated and will start thinking about EM instead, especially now that Wayne Kinney's new point kits are to become available. I was rather disappointed to see the negative attitude shown on this forum towards these and their possible application to P4.

DT

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Re: Turnout construction - Question here please.

Postby Terry Bendall » Sat Dec 19, 2020 8:21 pm

David Thorpe wrote:Isn't all this ply and rivet construction just a bit old hat now?


Well it has been around for a long time David but it still has its place. I have in the past used a mix of riveted sleepers and functional chairs successfully but that method can cause problems with expansion and I have used about 8 Exatoscale turnout kits on two different layouts. I have also built some Colin Craig kits for turnouts using flat bottom rail. I have just built a fairly complicate set up of two tandem turnouts and two plain turnouts which form two crossovers with two sidings off and used ply and rivet since it was for me the easiest way of doing things. and the advantage is that when adjustments have to be made simply heating the soldered joints allows this to be done. With glued functional chairs that is far more difficult.

Once everything has been tested I shall fit cosmetic chairs and my plan is to grind off any rivets that are visible either side of the rails, cut the chairs in half, trim to fit and then glue. I have done this successfully before so I know it works. Tedious but there is not a lot to do.

David Thorpe wrote:gain the imoression that trackwork construction in P4 is exceptionally complicated and will start thinking about EM instead,


I don't think the construction is any more complicated in P4 compared to EM, but because the tolerances are a bit tighter you just need to be a bit more careful how things are done.

Terry Bendall

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Re: Turnout construction - Question here please.

Postby davebradwell » Sat Dec 19, 2020 8:31 pm

You're completely ignoring the Masokits etched chairs which Julian has just used successfully - these must be the best way to make soldered pointwork.

I recall that the negative comments about potential new point kits was genuine concern over whether the technique could meet the P4 tolerances and given his existing commitments, whether they could be made available in a reasonable timeframe.

The abundance of information we have now seems to drown out the basics of this subject occasionally but there's nothing to stop anybody from using the good old 60's technique of just soldering rail to sleepers cut from pc board should they wish - we have to choose our own level of complexity.

DaveB

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Re: Turnout construction - Question here please.

Postby barhamd » Sat Dec 19, 2020 10:15 pm

Terry Bendall wrote:I don't think the construction is any more complicated in P4 compared to EM, but because the tolerances are a bit tighter you just need to be a bit more careful how things are done.

Terry Bendall


I'd completely agree with Terry, I've built both EM and P4 trackwork and it is next to identical, you just use different size jigs and need to be a little more careful of the tolerances using the P4 jigs as it is a little less forgiving. I used ply sleepers and exactoscale chairs on my model of Clare, I don't bother with rivets at all, just use a bit of scrap etch under the rails of the crossing. Dare I say it but the new Peco bullhead functional fishplates are actually quite good and can be used in P4.

David


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