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Delayed magnetic uncouplers (Kadee 321) or rare earth magnets?

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Delayed magnetic uncouplers (Kadee 321) or rare earth magnets?
Posted by IDRick on Monday, November 7, 2022 1:39 PM

I have code 100 atlas track (HO) and have two uncoupling locations (one with a 321 Kadee above ties magnet and a second with rare earth magnets).  My test boxcars have Kadee couplers, P2K metal wheelsets, and lead weights.  At present, the 321 magnet consistently performs drop uncoupling and delayed uncoupling. 

The rare earth magnets are 3/8" in diameter and 1/16" in thick (Magcraft Part NSN0732/N40).  At present, there is a single pair of vertically stacked magnets under each rail.  The magnets are resting on top of 1/16 inch styrene and are level with the underside of the ties.  Railcars will uncouple correctly over the magnets for a drop uncoupling but I cannot perform a delayed uncoupling move (uncouple and push to spotting location).  The coupler that moves away from the magnet automatically reverts to a centering position.  When I back up and push the car off the magnet, both  cars revert to a centering position and couple.

Any thoughts why I can't do a delayed uncoupling with the rare earth magnets?  Is my magnetic field too short?  I could increase the length of the magnetic field by adding another pair of magnets below the rails.

Which is more likely to give me reliable service, the 321 Kadee magnet or the rare earth magnets?  All would be placed in sidings not on the main.

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Posted by MisterBeasley on Monday, November 7, 2022 2:07 PM

If the magnets correctly uncouple in both intended modes, perhaps the problem isn't with uncoupling but rather with keeping the cars where they are.

The problem may be the metal wheel or at least the axles.  I initially replaced almost all of my couplers with Kadees, and then sometime later slowly replaced all the wheelsets with Intermountains.  I used my Truck Tuner on all the trucks, and replaced those that seemed worn out or weak.  This process greatly improved rolling resistance.

Then I put a large permanent under-track magnet below a crossing so i could take care of two sidings that came off of it.  It worked fine in one path, but there was a bit of a slope on the other and cars wouldn't stay spotted.  The magnet was drawing the new metal wheelset towards it.

Since these were sidings, the solution was both simple and scenic.  I put down a bit of glue and planted some field grass between the rails.  The tall grass would hold the cars in place under gravity, but would not inhibit motion by an engine or a pushed string of cars.

It takes an iron man to play with a toy iron horse. 

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Posted by doctorwayne on Monday, November 7, 2022 3:59 PM

As an experiment, I removed a couple of ties from an industrial siding, and then drilled two shallow holes in the plywood, side-by-side within the rails.  I then added an 8mm wide x 3mm thick rare-earth magnet in each hole, with the tops flush with the top of the plywood (both with the same polarity facing upward).
Next, I put the two ties back in place, then added some real rock ballast, wetting it, then adding diluted white glue.
The next day I tested the uncoupling procedure, which worked surprisingly well. 

Based on the above comments regarding the offset of the uncoupled couplers, I may add more to other sites, but perhaps use either slightly larger magnets, or double-stack the pairs.

The two-magnet test did offset the disconnected couplers, but not always to a degree which would allow moving the uncoupled car to another spot.

Wayne

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Posted by IDRick on Monday, November 7, 2022 5:54 PM

Thanks for your comments and clear explanations!

Success!  I should have tried this before posting!  Increasing the magnetic field fixed the issue.  I drilled 4 holes in scrap styrene.  Each hole received two magnets with the magnetic attraction from right rail to left rail.  The magnets are 19mm apart on center (right rail to left rail) and 14mm apart on center between magnet pairs.

right rail-----------------------------------

      HO track                                             19 mm apart on center

left rail------------------------------------

 

pair 1     pair 2    14mm apart on center

Results are excellent!  I get a nice click when the cars are placed over the magnets, wide separation. I could pull a car away and then bring it back to successfully push the second car to the desired spot.  Works well with cars with metal P2K wheelsets and lead weights.  Works equally well for delayed uncoupling with Athearn steel axles and boxcar weight. 

The total cost for 8 magnets is $3.  Cheaper than a commercial between-the-rails magnet and no need to immediately replace steel weight with lead or change to IM wheelsets.

Using 1 magnet per hole was not as effective as two magnets per hole.  The success rate for uncoupling changed from 100% to about 50% or less.

The next step is figuring out how to drill 3/8 inch holes in cork roadbed.  It tears up when the bit is too close to the edge...

Based on Wayne's comment, I should be able to ballast over the styrene and create a shoulder to match the cork roadbed and hide the magnets.

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Posted by wvgca on Tuesday, November 8, 2022 8:43 AM

i don't have any problems with delayed uncoupling, how ever my magnets are quite a bit different .. 1/8 diameter by 3/8 long, both aligned the same way .. strength was N52, and they were placed [one on each side], just inside the rails flush with the top of the ties ..

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Posted by IDRick on Tuesday, November 8, 2022 9:09 AM

My approach does work but is significantly more expensive than others.  For example, RR_Mel used 1/8 inch diameter magnets that were 3/8 inches long (one on each side next to the inside of the rail).  According to KJMagnetics, each 1/8 x 3/8 round magnet has about 1 pound of pull force.  Conversely, in my case with a 3/8 inch diameter by 1/8 inch deep magnet, the pull force is a whopping 4.4 pounds!  LOL, that better pull those pesky Kadee whiskers apart!  It appears that I followed the procedure from the "wrong" youtube video!

Since I have the 3/8" magnets on hand, I'm going to try putting them closer together.  Right now, they are centered under each rail and there is a ~10mm gap between the magnets.  Moving them closer, say 5mm apart, may result in success with 1 magnet per hole and reduce my cost from $3 to $1.50 per uncoupling location.

Alternatively, MagCraft sells a 1/8 inch diameter by 3/8 inch deep rod magnet for 32 cents each.  The pull force is 2.5 pounds.  Much easier to drill a 1/8" hole between the ties than messing around with 3/8" holes in styrene!  A possible option but there may be better...  Can anyone suggest a better alternative?!

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Posted by IDRick on Tuesday, November 8, 2022 9:17 AM

wvgca

i don't have any problems with delayed uncoupling, how ever my magnets are quite a bit different .. 1/8 diameter by 3/8 long, both aligned the same way .. strength was N52, and they were placed [one on each side], just inside the rails flush with the top of the ties ..

 
 Thanks for sharing!  Can you tell me which company you purchased from and product ID?  I've been using MagCraft because I can order their product through Home Depot and not have to pay shipping.  Right now, I'm considering this one from HD.
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Posted by maxman on Tuesday, November 8, 2022 9:24 AM

Dr. Wayne places the tops of his magnets flush with the top of the plywood.

Wvgca says flush with the top of the ties.

So I guess when describing the proposed magnet substitutes it would be important to know how they are intended to be installed.

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Posted by fwright on Tuesday, November 8, 2022 9:24 AM

I haven't tried it yet personally (still using a pick), but my take was always a row (2-4 magnets) on each side was the proper setup.  This was with 1/8" diameter, 3/8" long magnets polarized axially, mounted vertically.  This gave an uncoupling zone of about 1" so that precise spotting was unnecessary.

In all the working examples I have seen, top of magnets were barely covered by ballast, which would put them just under tie top height.  If the holes are drilled in advance, the magnets can be slightly higher under the rail base.

Fred W

....modeling foggy coastal Oregon in HO and HOn3, where it's always 1900....

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Posted by IDRick on Tuesday, November 8, 2022 9:52 AM

maxman

Dr. Wayne places the tops of his magnets flush with the top of the plywood.

Wvgca says flush with the top of the ties.

So I guess when describing the proposed magnet substitutes it would be important to know how they are intended to be installed.

 

 
Excellent point Maxman!  Mine were mounted just below the ties because the magnets are too wide to be at top of tie height without significant alteration of ties.  I suspect DrWayne had the same issue which influenced his mounting procedure.  If I buy new magnets, I'll buy 1/8 inch diameter and mount them slightly below the top of ties.
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Posted by IDRick on Tuesday, November 8, 2022 10:00 AM

fwright

I haven't tried it yet personally (still using a pick), but my take was always a row (2-4 magnets) on each side was the proper setup.  This was with 1/8" diameter, 3/8" long magnets polarized axially, mounted vertically.  This gave an uncoupling zone of about 1" so that precise spotting was unnecessary.

In all the working examples I have seen, top of magnets were barely covered by ballast, which would put them just under tie top height.  If the holes are drilled in advance, the magnets can be slightly higher under the rail base.

Fred W

Thank you Fred, very clear explanation!  I had previously read several threads on how to set up an uncoupling area.  As frequently is the case, there were many divergent approaches taken which confused me (easy to do, LOL).  I found an easy approach on youtube and went that way.  Your succinct description clarified matters for me.  wvgca's comments match yours very well.  Great to have clarity and agreement going forward!

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Posted by rrebell on Tuesday, November 8, 2022 10:07 AM

Magnets go by size and by strength. Placement is also important. Tested mine on a scrap setup with a cork over foam base so I could try all kinds of combos and did both straight and curved. Never been a big beleiver in Kadee everything for couplers but their consistincy in this case helped alot. I got my magnets off ebay and they were fairly cheap. Ended up using 48 strength, the 52's did not impove performance and were way more expencive.

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Posted by IDRick on Tuesday, November 8, 2022 10:24 AM

rrebell

Magnets go by size and by strength. Placement is also important. Tested mine on a scrap setup with a cork over foam base so I could try all kinds of combos and did both straight and curved. Never been a big beleiver in Kadee everything for couplers but their consistincy in this case helped alot. I got my magnets off ebay and they were fairly cheap. Ended up using 48 strength, the 52's did not impove performance and were way more expencive.

 

 
Thanks for the response rrebell!  I was able to find an earlier thread where you identified your magnets as 1/8" diameter and 1/2" long.  I am using a similar test bed (cork roadbed over dense insulation foamboard).  Very helpful to have results from similar construction!
 
How many pairs of magnets did you use?
 
What the spacing between magnets (tie width apart or every other tie)?
 
Magnets on curves, cool!  Tell me more, how did you arrange the magnets? 
 
Does curve radius impact performance or change the positioning to achieve high performance?
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Posted by wrench567 on Tuesday, November 8, 2022 1:38 PM

  Beside the magnetism to consider. You also need reliable couplers, springs, and centering springs. Before I install my KDs I file the back face of the knuckle to remove the flash and parting line. I also hit them with Lock Lube from the hardware store. It's a thousand times cheaper than the greasum KD sells. Works great.

    When I built my track scale gauntlet I used 5/16 square super magnets left over from another project. I didn't really worry about poles and north/south. Just pressed them in the foam flush and laid down the gauntlet and stained boards. They work fantastic.

  I get my magnets from K&J magnetics. Awesome pricing and quick shipping. Large selection too.

      Pete.

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Posted by IDRick on Tuesday, November 8, 2022 3:30 PM

Great points Pete, very important to tuned kadee couplers for any chance of success with magnetic uncoupling.  I used cars with that met NMRA RP for weight, tested coupler height above track and relative to standard.  All were spot on for the tests.  Good reminder to check all cars added to the layout.

Interesting, that you could randomly place magnets without specific care relative to N/S orientation.  I thought that was one of the keys but I must be wrong!  Not the first time!  LOL

I have compared prices between K&JMagnetics and Magcraft.  K&J was more expensive due to shipping versus free when ordering Magcraft through Home Depot.  I am surprised that the 1/8" diameter, 3/8" length magnets have such dramatically different pull strength (2.5 versus ~0.9 pounds).  I have emailed Magcraft hoping to get clarification on why their pull number is so much higher...

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Posted by wvgca on Tuesday, November 8, 2022 6:55 PM

IDRick

  Thanks for sharing!  Can you tell me which company you purchased from and product ID? 

 

i do remember where they came from, ebay , but no idea as to seller or product number, been too many years ..

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Posted by rrebell on Wednesday, November 9, 2022 8:07 AM

IDRick

 

 
rrebell

Magnets go by size and by strength. Placement is also important. Tested mine on a scrap setup with a cork over foam base so I could try all kinds of combos and did both straight and curved. Never been a big beleiver in Kadee everything for couplers but their consistincy in this case helped alot. I got my magnets off ebay and they were fairly cheap. Ended up using 48 strength, the 52's did not impove performance and were way more expencive.

 

 

 
Thanks for the response rrebell!  I was able to find an earlier thread where you identified your magnets as 1/8" diameter and 1/2" long.  I am using a similar test bed (cork roadbed over dense insulation foamboard).  Very helpful to have results from similar construction!
 
How many pairs of magnets did you use?
 
What the spacing between magnets (tie width apart or every other tie)?
 
Magnets on curves, cool!  Tell me more, how did you arrange the magnets? 
 
Does curve radius impact performance or change the positioning to achieve high performance?
 

It was after every tie but ended up using only two because I wanted as few as possible. I painted the tops and needed weeds placed on the ballast to make sure I found the right spot when uncoupling. You could use more if wanted, tried 3 but didn't go for 4 spots. Got a bunch of magnets left and they end up so hidden I might go back and add more so I don't have to be as pecise in switching.

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Posted by IDRick on Wednesday, November 9, 2022 4:48 PM

Thanks rrebell!  Would love to know your secret on how to setup uncoupling on curves!

On a side note, did not receive a reply from Magcraft about pull strength number for their 1/8 x 3/8 magnets.  K&J did reply and reviewed the specs for Magcraft, thought appeared to be similar to their magnets based on specs, felt K&J's estimate was more accurate.

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Posted by rrebell on Thursday, November 10, 2022 8:28 AM

For curves I found out you have to follow the air hose, if it is in 1/8" on the curve, then you do so with the magnets. Turned out I didn't need any curved placements on my layout except a very slight one. I have 18" radius at many places as I run small stuff and didn't have the space for larger, the magnets ended up being on the outside of the rail as close as possible to the rail on the outer part of the curve and 1/8" in on the inner rail

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Posted by IDRick on Thursday, November 10, 2022 12:59 PM

Thank you for sharing rrebell! Excellent observation!  I can try your approach when I receive my new 1/8" diameter x 3/8" depth magnets next week.  I have 18-inch radius sectional track and can also try varying radii with flextrack on a test bed.

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