Proto 120

Re: Proto 120

Postby taiwest » Tue Sep 28, 2010 10:53 am

I am turning them from scratch...so I can ream the center to fit any sized axle. I am planning on using a derlin axle for the non pickup wheels. I'm still toying with ideas for the wheels that will be powered, but most likely I will just use a derlin insert on one hub. So yes, one wheel will be insulated from the axle.
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Re: Proto 120

Postby ConducTTor » Tue Sep 28, 2010 11:50 am

That could become extremely useful to many of us.
My website: http://www.ttnut.com
It's the website you're already on. But if you want to be even more on it, click the link.
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Re: Proto 120

Postby taiwest » Tue Sep 28, 2010 11:57 am

I'll post some photo's after I turn a set.
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Re: Proto 120

Postby areibel » Tue Sep 28, 2010 10:54 pm

Yours sounds like a great project! I wish I had the skills to do something like that.

But a few observations that may help you in the planning. The original HP steam locomotives used a solid turned wheel with one side insulated at the axle. But they also had a cast metal steam chest (cylinders), so it required an insulated main rod on insulated axle side. HP actually used a standard rod that they cut and rivited a piece of fiber material into to achieve this. But it still wasn't a great set up, especially with the later HP locomotives when valve gear became more common with an all metal frame and boiler. There are many TT'ers that will tell you horror stories about trying to chase down a stray short!
If you can use an insulated steam chest of plastic or resin, I think it would make things simpler. I had always thought it might help to have them cast in resin with a small brass liner (or drilled and pressed in) for the cross head to ride in?
I'd be glad to hear any suggestions you have!
Al
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Re: Proto 120

Postby taiwest » Wed Sep 29, 2010 12:58 pm

Areibel,

Thank you for the suggestions. I am still trying to work out how I am going to isolate everything. Any idea how they do it with the store bought brass locos? Anyhow, an embossed brass liner over a resin cylinder would be an easy way to go.
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Re: Proto 120

Postby CSD » Wed Sep 29, 2010 1:39 pm

taiwest wrote:... Any idea how they do it with the store bought brass locos...


I have a kit for a brass TT loco that conceals the mechanism in the tender. It uses strategically placed strips of plastic or paper behind the wheels to isolate the wheels from the chassis and shell. Also the wheel centers are plastic.

P.S. plastova tycka = plastic stick, izolace pod sbiraci plisky. (napr. papir nebo folie) = isolation of the collecting strips. (eg. paper or film)
556.0 tender instructions.jpg


P.P.S. Welcome to the site! I'm excited to see your project progress.
Mark
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Re: Proto 120

Postby areibel » Wed Sep 29, 2010 4:26 pm

taiwest wrote:Areibel,

Thank you for the suggestions. I am still trying to work out how I am going to isolate everything. Any idea how they do it with the store bought brass locos? Anyhow, an embossed brass liner over a resin cylinder would be an easy way to go.


The insulated cylinder would solve most of the problems, and it is much easier to do an axle insulated wheel!

The brass locos are rim insulated, that is the center is mounted directly on the axle. The tire is turned from a separate piece (usually stainless steel now) and is pressed onto the center with a thin layer of insulating material (like Mylar) between the center and tire. The machining needs to be pretty accurate so the press fit will preserve the insulation but stay tight. The You can use a little Locktite to help hold the tire on the wheel. If you don't mind Yahoo groups, thre's a pretty good one called "brasslocobuilders" that gets into a lot of exactly what you're doing. Most of the guys on there are in O scale or S, but they're using the same techniques you are. And there are some links they've posted (and I can't find right now) about turning the centers and tires and fitting them together. They're a pretty knowledgable group.

Most other steam locos now in HO or N use plastic centers, that works well except they need to be assembled with the crank pin threads in exactly the same place on each wheel- most have a threaded brass insert for the crank pin that can be set into the injection mold when it's made.
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Re: Proto 120

Postby taiwest » Wed Sep 29, 2010 6:41 pm

areibel,

That is great info. Thank you.
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Re: Proto 120

Postby scaro » Thu Apr 10, 2014 6:24 am

Scalefour's P120 standards, for information.

http://www.scalefour.org/history/p4manual.html
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Re: Proto 120

Postby Marquette » Thu Apr 10, 2014 9:55 am

No idea. Seems to have just vanished.

I do have a friend locally who has been experimenting a bit with P:120 wheels, turning his own... I'm watching that with interest, I may end up going that way myself.
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