Electrical conductivity of ballast.

[scafellpike]

A couple of years back it was reported to me that a part of our club layout was becoming warm, in fact so warm that you could hardly keep your finger on it.  After much searching for the problem and isolating various sections of track the problem was discovered to be a buffer stop (made of plastic) which had a pile of ballast on it, and around it, which was conducting electricity.  The solution was simple cut the rail immediately in front of the buffer stop - problem cured.

I have now  just completed laying the track for a fairly large engine shed layout, tested all track, points all working fine, no shorts or other problems so moved on to ballasting.  After the ballast was dry checked for any problems, ballast in checkrails, movement of points etc.  I discovered that there was a small current draw on the layout and instead of the test meter reading clear between rails there was a small resistance reading between the right and left rail.  As a test I made up a test track laid on plasticard and ballasted it.  I also  made up a ballast pile and glued that also.   Both tests showed that the ballast when set was conducting electricity.  Has anybody else noticed this and have there been any problems created as a result? 

[Free At Last]

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Edited May 8, 2021 by Free At Last
Topic moved.

[RFS]

Sounds like it's a bit damp. I've ballasted track in the usual method and although apparently dry there was still enough moisture to conduct a bit of current for some time afterwards. 

 

I would suggest testing the ballast area with a dampness meter. 

[TheSignalEngineer]

Very prototypical. We had no end of problems in the 12 inches to the foot world with ballast affecting the electrical performance of track circuits.

[rue_d_etropal]

I wonder, who knows what is in some ballast?  Many years ago I built one of my annual exhibition layouts using LGB brass track. As ballast is big in big scales, I used some ballast from a local garden centre. I think it might have been from the fish tank department.

I used my normal method of using diluted PVA glue,and when it was dry, everythng short circuited, and only way to fix it was to remove the ballast and replace . The replacement ballast(model railway supply?) worked perfectly, no problems, but the brass rail showed signs of some type of chemical reaction .

I assumed there must be something in the original ballast the conducted electricity, possibly only when it was in contact with PVA glue, as that is known to react with some metals.

I have used varous ballasts since, many from pet/garden centres and no problem .

[phil-b259]

1 hour ago, TheSignalEngineer said:

Very prototypical. We had no end of problems in the 12 inches to the foot world with ballast affecting the electrical performance of track circuits.

 

Yup

 

I was told that during the mid 1990s there was a ballasting job on the BML which got cancelled due to wet ballast getting frozen inside the hopper wagons after overnight temperatures plummeted. The next night Some bright spark had the idea of spraying the ballast wagons with salt water so the ballast didn't freeze and could be discharged from the wagons.

 

Things seemed to have gone well until the line was opened for traffic at which point the S&T started having numerous issues - track circuits flicking, poor drop shunt tests, low relay voltages / currents yet high feed currents. The top S&T bods were puzzled, equipment was changed with no improvement, etc - it wasn't until a S&T tech literally went and licked a piece of shiny looking ballast did they realise all the S&T problems were because of the salt contaminated ballast!

 

The 'licking the ballast' comment subsequently went down in local S&T folklore and was always bought up when difficult track circuit issues were encountered in subsequent years

 

As for the original problem, water tanks were bought in and the track given a good drenching to try and wash the salt out - and although it helped a bit, the track circuits were still a bit unstable until another possession was arranged and all the contaminated ballast stripped out and fresh non salty ballast laid!

[TheSignalEngineer]

A couple I remember concerning salt. During the late 1960s and early 1970s some bright spark decided to convey rock salt from Cheshire for road use in unsheeted open wagons during the winter peak demand. When I was in our Crewe office we had a heavy snowfall and everything was stopped for a few hours including a train of salt at Salop Goods box. When it eventually moved on the track circuit stayed down due to snow having melted on the salt and drained out of the wagons, coating the sleepers and rails. Despite everywhere else being covered in snow about 200 yards of ballast was completely clear. On another occasion during heavy rain a train which had been looped left about half of the track circuits on the Grand Junction line between Bescot and Stechford failed. It was stopped and put inside until it had dried out. 

 

Edited May 8, 2021 by TheSignalEngineer

[Titanius Anglesmith]

On 08/05/2021 at 11:20, phil-b259 said:

a S&T tech literally went and licked a piece of shiny looking ballast

 

I’ll have to remember that one. Or better yet, convince a colleague to do it instead......

[Mark Saunders]

51 minutes ago, Titanius Anglesmith said:

 

I’ll have to remember that one. Or better yet, convince a colleague to do it instead......

Beware of yellow snow or blue ice!

[NIK]

Hi Scafellpike,

 

I think I remember somebody probably on RMWeb having a problem with conductive ballast/glue on their layout.

 

The conductivity will depend on the glue used. Was it PVA or possibly PVA with other stuff added by the manufacturer?.

 

I've just read PVA reacts with metal salts.

 

This is a long shot is the water you diluted the PVA with (if you did) very soft or very hard?.

 

When a club member brought along some ballast collected from a foundry I tested the particles did not conduct and were not magnetic but I didn't do a resistivity test on a test board with the ballast glued around a bit of track using PVA. If we ever fit block detection using 10k resistors on vehicle axles we shall find out.

 

Regards

 

Nick

 

 

[tomparryharry]

The section of line  between Llandaff & Cardiff Queen Street was re-laid with ex-BSC steel slag. Lasted about a week before the decision was taken to remove, scrape & relay. Llanwern steelworks used to produce slag, which had a high iron content.  Quite good for ballast on preserved railways, as long as you keep it away from the track circuits. 

[scafellpike]

Hi as an addition to my original post the ballast is that which is commercially available.  A mixture from Carrs, Woodland Scenics etc.  The Ballast is cinder type (the layout being a large MPD.  The glue used is Ballast Magic.  The layout is workable and broken down into 7 power districts,  the districts with the most amout of track hence the amount of ballasting show the lowest resistance.  Regarding the moisture content, I do not have a moisture meter but the ballast was laid in January and the layout kept inside a centrally heated hous with no moisture level issues.   The humidity level in the house is around 49-50% (well within the recommended range of 30-60%).   I just raised this post as a matter of interest, my curiosity askes has anybody else had this issue in model form.  As we are still as at 13/05/21 not able to have club meetings it is difficult to test other club layouts myself.

[NIK]

Hi Scafellpike,

 

What was the value of resistance that you got and what sort of meter did you use in the test?.

 

I don't have any Ballast Magic - I don't suppose they have put what chemicals are used in it on the packaging?.

 

Some evaluation of Ballast Magic was done in my club for Deluxe Materials prior to it going on sale.

 

It was found that the pre production liquid didn't glue all the ballast down (at least in the evaluation).

 

Perhaps something was been added (such as an ionic surfactant?) before Ballast Magic went into production?.

 

Regards

 

Nick

[Derekl]

Looking at the Ballast Magic web-site there is no reference to composition (not surprising, as I don't suppose they want it copied), but it is a powder to be mixed with the ballast, placed in position and set by water spray.  Perhaps this is a different product to that mentioned by Nik above, which appears to be a liquid.

 

The system is similar to using Cascamite mixed with ballast and then fixed suing water spray. The Ballast Magic can be released by soaking in hot water, which doesn't sound much like Cascamite, as far as I am aware.

 

[NIK]

Hi,

 

Sorry I forgot Ballast Magic was a powder not a liquid. I think I didn't see it out of the bottle, only the test bits of board with track and ballast glued on.

 

I used Cascamite 45+ years ago on my first scenic model railway and any powder that didn't get wetted by the water spray tended to get on point blades, rail heads and pickups causing poor conductivity.

 

Regards

 

Nick

[scafellpike]

Hi All,

A little more information and a correction although the ballsat was obtained from various suppliers, Carrs Woodland scenics etc. the initial glue used was Ballst Magic.   It has come to light that a number of' bald spots appeared after the ballast had dried and been vacuumed.  Those bald spots were re-ballasted and Ballast Bond used for that purpose. Ballast Bond was also used for the mass ballasting of the buffer stops.

 

On my test ballast I used Ballast Bond and Woodland Scenics and Carrs ballast mix (alll that was available to me at the time)  Regarding the resistence it is a difficult question to answer as it all depends on where you read from and to.  Ballast 5mm wide 2mm deep over a 15mm distance could read as little as 103 ohms and in another length read clear.  On the buffer stopsimulated mound  the ballast mound reads 52 ohms tests across the 16.5mm from rail to rail, different parts on the ballast mound give different readings as do different mound heights but the results seem fairly consistent taking into consideration that the centre of the mounds could still be slightluy damp. 

 

On the actual layout all tracks where the ballast has been laid at a depth of 1.5 to 2mm there is no reading between the rails

 

I am using a standard multimeter for the readings, I tried a second and gained slightly different readings but within 5% of the initial readings.  That is not suprising as poking a probe into ballast I cannot guarantee to hit the same spot twice.