Author Topic: Choice of Material for Kozo's A3 Switcher  (Read 3079 times)

Offline Bobsmodels

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Re: Choice of Material for Kozo's A3 Switcher
« Reply #15 on: July 23, 2017, 05:59:07 PM »
Hi

there was some discussion of materials substitution in this build of the A3

http://www.homemodelenginemachinist.com/showthread.php?t=20460

Bob

Online Kim

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Re: Choice of Material for Kozo's A3 Switcher
« Reply #16 on: July 23, 2017, 09:52:25 PM »
Thanks for the link Bob.

So, I read some of that, and they seem to be singing the praise of Hot Rolled Steel, rather than Cold Rolled.  They seem to think it has less stress rolled into it when being formed, so it will go banana shaped on you less as you mill it into shape.  But I remember Hot Rolled steel being very hard to work with (though, granted, I don't have a lot of experience with it).

I know you have to do some stress relief in CRS.  But if I'm going to bother to do that, will it be better just to anneal hot-rolled stuff and save even a little more money, hoping that annealing makes it easier to work with?  Or should I stick with the CRS and just do my best at stress relief?

So many questions! :)
Thanks,
Kim

Offline Bobsmodels

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Re: Choice of Material for Kozo's A3 Switcher
« Reply #17 on: July 24, 2017, 01:11:17 AM »
Kim

I am partial to things that do not move when machining them.  So I would use either hot rolled or 4140​ or 1144(stress relieved stuff) where things need to stay put ie fluting a side rod or making linkages.  Hot rolled has the disadvantage of not being dimensionally accurate (rounded edges)so you need to buy larger size and mill down ie if you need a 1 x 1/2 a 1 1/8 x 1/2 would need to be purchased.  Use as little 12Lxx as possible as it rusts.  The use of steel in places where Kozo calls for brass might be better from a strength point of view but this is a small model so I doubt it would actually make a difference.  If silver brazing is necessary then stick with the brass.  Stainless is good for looks sometime, like the side rods nice and polished, but if you do not intend to polish them bright then just steel.  Making fasteners from stainless has advantage of nice looking and removal later with no rust.

Remember when making the copper boiler NO BRASS for anything ie bushings, manifold etc, use only bronze. If you opt for a steel boiler, same thing no brass.

In a model this size you are not using that much material so cost is usually not an issue, use the material that will make your life easy.


Hope this helps


Bob

Offline Dave Otto

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Re: Choice of Material for Kozo's A3 Switcher
« Reply #18 on: July 24, 2017, 01:24:38 AM »
Hi Kim

I guess it really depends on the part and how much machine work is involved in it. HRS tends to have rounder corners (unless you are cutting from plate) and of course the the mill scale that needs to be removed. I haven't found HRS any more difficult to work with than CRS (we're not talking bead frames here). Keep in mind that SS bar stock will also go banana on you just like CRS.

If you are going to paint I don't see any reason to go with SS, I personally prefer the look of steel and cast iron on a model; yes SS will not rust but is just doesn't look the same.

I do agree with your thinking, there is no reason to make a model entirely from brass or SS unless that is your desire.

Just my thoughts,
Dave


Online Kim

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Re: Choice of Material for Kozo's A3 Switcher
« Reply #19 on: July 24, 2017, 04:06:28 AM »
Thank you Bob and Dave for your thoughts.

I do appreciate everyone taking the time to reply!
Kim

Offline Stuart

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Re: Choice of Material for Kozo's A3 Switcher
« Reply #20 on: July 24, 2017, 10:42:02 AM »
Kim

If you have charcoal barbecue cut up your CRS into suitable lengths,get the BB going put in the steel cover it with charcoal and just leave it until itís gone out and cold , that should do the trick

Note do not quench from red as you will have a very thin case harden

Stuart
My aim is for a accurate part with a good finish