Johns 7mm Layout

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Of course the old bib and bob thing, I'll look that up. :roll:

John

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There has been some rethinking about this 7mm layout in 12'.  I (we) have realised that not only must the turnouts fit length wise but there has to be sufficient length to the layout to get the track spacing (or 6 foot) reasonable.  That wasn't happening here.

The problem is that standard Peco turnouts have quite a large radius so it takes considerable length until the turnout across the 6' will comfortably meet.

After scrutinizing Drewry Lane, it is clear that all small radius straight turnouts were used.

So, how to reduce the radius?

I had one of my moments and the bright idea to use OO peco small radius turnout templates blown up to 7mm (190% btw).  A check of how these look confirmed that the method will work.

My first step was to make common crossing jigs for the turnouts.



I cut out the crossings from LH and RH turnouts and taped these down to some scrap ply.  I then cut some copper clad to length.  These were nailed down with an angle that matches the vee in the template.  More on this later.

Comparison of the track:



These are LH turnouts.  On the left is a standard Peco medium turnout and on the right, a template for a Peco OO small radius turnout in 7mm scale.  The difference in length isn't great, about 1" but the real benefit is in the turnout rad. which significantly smaller.

This isn't ideal.  I haven't measured the turnout radius but it might be on the giddy limit for 7mm min rad.  Small radii can cause buffer lock problems when propelling loose coupled wagons.  I did check the Terrier on some track bent to the same radius and it seems comfortable.

John

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Genius. No other word for it.
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Perhaps idiot savant is a better term.  :pathead

John

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Sorry John, definitely not having that. You've proved far to often that you're anything but.


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Aw you are really too kind.   :thumbs

John

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Hi John,

Those Peco code 124 turnouts are about 16.3" long. A Peco short turnout in HO/OO has a #4 frog. If you went for a short curved-heel design with a #4 frog you could get the length down to around 14 inches with a 35" radius. There is no reason you couldn't use a #3 or #2.5 frog, all depends on whether the stock will get around the corners.

Going to a 9' curved heel and a #3.5 frog would give you a length of around 12.8".

Nigel



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It's not the overall length so much Nigel (although that is also too much for the layout), as the length of board required to get the diverging road out to a reasonable spacing between tracks.  The smaller radius of the blown up OO turnout lets that happen in a much shorter length.

I suppose I should do more reading so I would be able to understand your terminology better.  I just finished building a short Y turnout.  I'll take a picture to compare the O Peco.

The small rad turnout has a rad. of 58", while the Y rad. is 45" (derived from chord and segment).

I'm also finding that, as I do more of this, I am getting better.

John

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Hi John,

Curved heel will give you a shorter length for a given angle. Using a 9' curved heel and a 3.5 frog gives you a radius of 27".

In this type of turnout (no longer used) the heel of the switch blade is curved, as well as the closure rails. no reason why you have to stop the curve at the frog.

Check out Templot.

Nigel

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I've been working to put my theories into action.  I made a Y turnout using a blown up Peco code 75 template:



Note that I have lined up the tiebars.

 Standard Peco Y is on the left. 

I added some sleepers and rail at both ends to provide some flexibility when fitting.  My Y turnout is 4" shorter than Pecos and obviously the diverging roads have a much smaller radius.

I think this gives me a fighting chance to make things fit.

John

Last edit: by Brossard


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A couple more examples, this time straight turnouts:



On the left is one I made earlier to a Peco O gauge medium rad. template.

On the left is a turnout I just completed.  Comparing the common crossing, you can see it is significantly shorter.  Again the diverging road rad. is smaller meaning that 6 foot track spacing can be attaining in a much shorter distance.

John

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I wanted to get a sense of train length so I posed one on the sector plate:



The length of the train (less the loco) will drive the length of the arrival track on the layout.  This track must be able to contain the 5 wagons to permit the loco to uncouple and run round.

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Having had a good look at where things go on the layout I am getting more confident that the track will fit.

I wanted to start a new turnout tonight and began with the vee. 

The vee starts with two lengths of rail long enough to overlap the edge of the template.

The first step is to bend the straight rail to the angle of the other one.  Then the angled part of the straight rail is filed off (in this case I used a grinding wheel and files) so that there is a bevel on the inside.

Next take the angled rail and file/grind a bevel of that.

You will end up with rails as follows:



The lower rail is the straight and you can just see where it was bent.

Slide the two rails into the jig:



Solder the joint making sure that the rails don't lean and are snug in the jig.  Turn it over and solder the other side.  There will be a bit of unevenness at the joint, fill that with solder but don't desolder the joint.  I use high temp (188) solder for this.

The final result:



The vee sits accurately on the template.  Note the nose, it is rounded over as are the tops of the rails.  The idea is to make a gentle transition for the wheel to negotiate.

I'm making a crossing jig which I tried tonight.  I found a couple of problems with it so it is being redone.

John

 

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Interesting method for creating the V, Hand built track is something I would like to give a go sometime in the future, Something to log till then.

Kind Regards

Aaron

Kingsmead Station

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The methods are the same for both 4 and 7mm Aaron.  I've built a lot in copper clad in 4mm and I'm getting my hand in on 7mm.  There is a learning curve, mistakes will be made (and I've made more than I'm willing to own up to).

A couple of books that I recommend:

Finescale Track

https://www.amazon.co.uk/Track-Design-Construction-Using-TRAX/dp/0954203593/ref=sr_1_4?s=books&ie=UTF8&qid=1481304807&sr=1-4&keywords=jeff+geary

John

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Many thanks for the references, Now noted for the future, Best way to learn is from mistakes I find, at least that way I remember what not to do.

Kind Regards

Aaron

Kingsmead Station

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Hi John,

One of the issues I've had when using the bent/beveled method is that the bent one always has some vertical distortion due to the foot being a different dimension to to the head. The only way I've found to overcome this is to file a small nick in the foot where the bend will be made, and then grind back the rail to the bend and then grind the angle. I've stopped using this method, and now bevel both rails and use a jig to get the correct position when soldering.

Are you providing a support underneath? (As in a plate cut to the frog outline). 

Nigel

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Hey Nigel, I haven't seen (noticed?) the distortion and I'm quite happy with the way this vee came out.  More than one way to do it no doubt.

As to support for the vee, the trick is to find something that is precisely the right thickness and I suppose a cut down chair will suit.  On the last turnout I used a piece of plastic strip that looked right but wasn't.  I did end up with distortion due to that but by pressing the vee while applying the soldering iron to the rail I got the vee to bed itself.

Some interesting pointers here:

http://www.templot.com/martweb/gs_realtrack.htm

I thought the bit about set was very interesting.  Filing a rebate in the stock rail doesn't seem quite the thing, although it does work.

John

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Hi John,

Could be just code 100.

Templot is full of good stuff, whence my suggestion re a curved heel (and curved frog) to gain a few inches.

Nigel

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I was unhappy about the fiddling about to make common crossings.  I decided to make a jig similar to the EMGS jig:



I bought this already made up but never had a chance to use it.

There are instructions in the EMGS Manual on how to make this and there is a brass etch that can be purchased for those who want to make their own.

I thought I could do something similar with one obvious difference being the thickness of pins and uprights, these had to be 1.75mm (or as near to it as possible) which is the 7FS flangeway width.  The other difference is the pin spacing - this had to be roughly timber spacing.

Here's my Mk 2 in the process of construction:



Two pieces of 1x2.  The pins and uprights are thick brass strip glued together to give me a thickness of just less than 1.75mm.  (It is better to be too tight than too loose.  If you are tight you file to relieve that, too loose and there is sod all you can do).

The jig assembled:



One other difference from the EMGS jig is that I left out the middle pin which stopped me getting a straight edge through the gap.

Here's a crossing I made with the jig:



The design allows you to clamp the vee and wing rail accurately in position and then solder to the 1mm copper clad strip.

Here's the crossing laid on the template, pretty accurate I think:



I need to trim off the excess copper clad.

This is the heart of the turnout and where most people go wrong.

John

Last edit: by Brossard


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