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Converting Kroc 3356 and other older ones
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Offline owidgie  
#1 Posted : 28 August 2020 04:33:15(UTC)
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owidgie

United States   
Joined: 03/06/2007(UTC)
Posts: 149
I submit a question for the group. This will be for those who have knowledge of what I am talking about. Specifically when converting an older Kroc, the permanent magnet will contact the inner roof of the body on a curve and de-rail.

Now, I know I'm not the sharpest tool in the shed, but I know I'm not as dull as a sledge hammer. Basically I know how I solved this problem, and I have seen examples from Marklin in some locos, but I would like to know how others have done it.

Here is the basic problem:

The old field coil is narrower that the new permanent magnet.

1.JPG


The new permanent magnet fits as one would expect into the frame.

2.JPG


The problem is when the front truck goes around a curve, the magnet swings out. This would not be an issue if the magnet was thinner and shorter.

3.JPG


Once the magnet swings out, it contacts here under the roof.

4.JPG



So once again, for those who have had this problem, how have you overcome this issue?

Thanks in advance.

Rick
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Offline Johnvr  
#2 Posted : 28 August 2020 07:56:26(UTC)
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Johnvr

South Africa   
Joined: 03/10/2010(UTC)
Posts: 1,269
Location: Cape Town, South Africa
Hello Rick

Easy solution : file down the protruding corner of the magnet.
I did it quite easily, and it has no effect on the running performance.

RegardsBigGrin
John
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Offline ocram63_uk  
#3 Posted : 28 August 2020 09:40:35(UTC)
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ocram63_uk

United Kingdom   
Joined: 07/01/2015(UTC)
Posts: 704
Location: England, Suffolk
What John suggests has been done, by the Marklin repair center in Italy, on my 3352. If they do it then you can do it
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Offline PJMärklin  
#4 Posted : 28 August 2020 10:00:19(UTC)
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PJMärklin

Australia   
Joined: 04/12/2013(UTC)
Posts: 2,210
Location: Hobart, Australia
Originally Posted by: owidgie Go to Quoted Post
I submit a question for the group. This will be for those who have knowledge of what I am talking about. Specifically when converting an older Kroc, the permanent magnet will contact the inner roof of the body on a curve and de-rail...

Here is the basic problem:
The old field coil is narrower than the new permanent magnet...
The new permanent magnet fits as one would expect into the frame...
The problem is when the front truck goes around a curve, the magnet swings out. This would not be an issue if the magnet was thinner and shorter...

Once the magnet swings out, it contacts ... under the roof.

Rick



Hello Rick,

Thanks for the "heads up" re this problem - my 3352 Krok is not far down my list for conversions. It has a 3-pole DCM like your 3356 and I converted it initially with a 6080 many years ago. My old 3015 remains analogue (I thought to convert this might be considered sacrilege)

If you are committed to upgrading the motor to a 5-pole armature then with the usual methods you are stuck with the thicker permanent magnet since the 5-pole armature is longer than the 3-pole.

As John has commented, one option then is to file down the problem part of the magnet.


If you are not committed to changing to a 5-pole armature, then you can buy the magnet alone as a spare part (E389000 for the DCM) and it has been described on the forum that you can remove the excess leaves that make up the the magnet so as to bring it back to the thickness of the original electromagnet. I have been disinclined to do this.

My own preference (with which I will now approach my 3352 thanks to your warning) would be to exchange the previous electromagnet with the ESU permanent magnet for DCM - #51962 and retain the original 3 pole armature. The ESU magnet is thinner and the same thickness as the original electromagnet. This alternative is also described on this forum but I thank Ray for pointing it out to me in the past.

I will be interested to see some other solutions from the forum.

Regards,

PJ

Edited by user 29 August 2020 10:34:29(UTC)  | Reason: Not specified
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Offline owidgie  
#5 Posted : 28 August 2020 20:47:25(UTC)
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owidgie

United States   
Joined: 03/06/2007(UTC)
Posts: 149
Originally Posted by: PJMärklin Go to Quoted Post
My own preference (with which I will now approach my 3352 thanks to your warning) would be to exchange the previous electromagnet with the ESU permanent magnet for DCM - #51962 and retain the original 3 pole armature. The ESU magnet is thinner and the same thickness as the original electromagnet.




Hi PJ, this is a good point but if you are going to use the ESU permanent magnet (that I assume solves this problem), why don't you use a 5 pole armature since it is only the magnet that is the problem?


Rick
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Offline PJMärklin  
#6 Posted : 29 August 2020 03:29:41(UTC)
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PJMärklin

Australia   
Joined: 04/12/2013(UTC)
Posts: 2,210
Location: Hobart, Australia
Originally Posted by: owidgie Go to Quoted Post

... why don't you use a 5 pole armature since it is only the magnet that is the problem?
Rick


Hi Rick,

My previous comment :

Originally Posted by: PJMärklin Go to Quoted Post

... since the 5-pole armature is longer than the 3-pole.

Is actually incorrect. Only correct with the kits for FCMs. If converting the DCM with a 60941 motor upgrade kit, the kit's 5-pole armature (E386820) is the same length as the DCM's 3-pole armature, however the diameter of the circle traced by the winding arms of the 3-pole armature is wider than that of the 5-pole.

The ESU magnet #51962 has an I.D. to suite the 3 pole armature, not the 5 pole armature thus the permanent magnetic field would exert a weaker force on the armature windings field and I expect the motor would be less efficient (? Per ?)

PJ
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Offline ktsolias  
#7 Posted : 29 August 2020 18:14:09(UTC)
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ktsolias

Greece   
Joined: 01/05/2016(UTC)
Posts: 610
Location: Athens
This is my solution to the problem

https://www.marklin-user...dile--Digital-Conversion

Regards

Costas
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Offline owidgie  
#8 Posted : 29 August 2020 20:25:14(UTC)
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owidgie

United States   
Joined: 03/06/2007(UTC)
Posts: 149
Thanks to all - awesome and logical answers. I was a little concerned that I was over thinking it.

This was my solution which seems to line up with every else's answer: I was a little concerned that I was over thinking it.


I had purchased a small milling machine about 2 years ago. I love using it when needed for conversions. This is one of those tools that you don't need very often but when you do, you need it really bad!

5.JPG


Permanent magnet installed

6.JPG

7.JPG

Thanks again!

Rick
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