SP GS-4 Drive Wheels

Re: Pullman Standard Passenger cars

Postby gerhard_k » Tue Apr 21, 2015 7:27 pm

Rob M wrote:If I were to do something like this (and I'm not) I would use some existing drivers, even if they weren't correct.

http://www.3smr.co.uk/wheelstock.html

At the risk of continuing off-topic:
It looks like none of those drivers have counterweights along the rim - I'm used to seeing a fairly heavy counterweight on the main driver (where the piston rod connects) and smaller ones on the others. These are essential (at least on the full-size :wink: ) for balancing the rotating forces. Do they have different laws of physics in Britain? :doh:
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Re: Pullman Standard Passenger cars

Postby areibel » Tue Apr 21, 2015 7:47 pm

Instead of having to make three or four different wheels with different counterweights, the modeler can cut the shape of the correct counter weight and glue it on as needed.
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Re: Pullman Standard Passenger cars

Postby j p » Wed Apr 22, 2015 2:18 am

Bernd wrote:[quote="j p]The wheels can be cast out of brass using lost wax technique, then add the tire. I am not sure if nickel-silver would make the correct steel color. Maybe. Same technique as in 1950s for spoked wheels. Just making the master is easier now with 3D printing.[/quote]

I see you haven't studied up on casting. Casting brass is a little tougher than aluminum. With brass if you don't add enough zinc the brass gets hard and brittle. Also you need a higher heat to melt brass.

Spin casting was always a technique I wanted to try just to see if something like this could be done. And as far as nickel silver is concerned it would be the closest to real looking steel as you can get. Remember a majority to the model railroad wheels are nickel plated.

Bernd[/quote]


:lol: :lol:
Bernd, I have a set for brass casting. You have to select the correct brass alloy for casting, of course. Same with Aluminum. Temperature is not a problem, specific heat capacity is. The casting temperature for BR10 is 1050 - 1080 Celsius.
The kit can be used for other metals too. Just not at the same time because of contamination. It was designed for hobby jewelers, for casting brass, bronze, sterling silver, and gold. It can do also copper, but only 50 grams.
http://www.compucutters.co.uk/

Jan
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Re: Pullman Standard Passenger cars

Postby TiTan downunder » Wed Apr 22, 2015 8:03 am

Another option for your wheel centres is Rapid Prototyping.
Several years ago one of my customers in On3 1/2 ( models South Australian 3'6" gauge ) had the driver centres done this way. They were cut out of 0.010" styrene, in layers, to give the spoke contour and the layers they glued together and a RTV mould made. He had Nickel silver tyres turned up and I then cast the wheel centres in urethane with the tyre recessed in the mould. Any failures in the urethane casting were discarded and the tyre used again for another try.
They were then left for several weeks to cure/harden off properly. As far as I know all loco's are still in operation.

Ian
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Re: Pullman Standard Passenger cars

Postby gerhard_k » Wed Apr 22, 2015 11:04 am

Bernd wrote:Ok, I need a drawing for the wheels of the GS-4 for research and development. Anybody?

I'm an SP modeler also, citrus industry emphasis - R40-23 reefers anyone? (sorry, off-topic) :silent:
I would take a GS-4 also!
Bernd, you may get some help by putting in a query at the discussion boards at
http://www.southernpacificmodelerssocie ... portal.php
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Re: SP GS-4 Drive Wheels

Postby j p » Wed Apr 22, 2015 2:04 pm

HP drivers are 75". Can that difference be accepted?
(Measured on 4-6-4 Hudson model which is supposed to have 79" drivers)
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Re: SP GS-4 Drive Wheels

Postby richardedmonds » Wed Apr 22, 2015 3:45 pm

Bernd wrote:Starting a new thread so Rob's thread won't get hi-jacked by talk of research and possible production of drive wheels.

I searched through my Mainline Modeler magazine archive and came up with a Union Pacific 4-8-4 with 80" diameter drivers.

Image

So now I have something to work with.

Bernd


Bernd do you mean you are going to make them or something
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Re: SP GS-4 Drive Wheels

Postby gerhard_k » Wed Apr 22, 2015 3:58 pm

j p wrote:HP drivers are 75". Can that difference be accepted?
(Measured on 4-6-4 Hudson model which is supposed to have 79" drivers)

Because the model flanges are so much larger than the full-size, it is usual for model manufacturers to make a compromise.
If the running diameter is kept the same, the overall diameter is much larger, and not only does the wheel look too large, but the spacing has to be increased, leading to a longer wheelbase and disrupted proportions.
If the overall diameter (flange tip) is made the same, the wheelbase can be correct, but the running diameter is decreased and the drivers will look much too small.
So usually they find an intermediate solution. Of course, having the smallest feasible flange size is a big help in this.
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Re: SP GS-4 Drive Wheels

Postby j p » Wed Apr 22, 2015 4:12 pm

gerhard_k wrote:
j p wrote:HP drivers are 75". Can that difference be accepted?
(Measured on 4-6-4 Hudson model which is supposed to have 79" drivers)

Because the model flanges are so much larger than the full-size, it is usual for model manufacturers to make a compromise.
If the running diameter is kept the same, the overall diameter is much larger, and not only does the wheel look too large, but the spacing has to be increased, leading to a longer wheelbase and disrupted proportions.
If the overall diameter (flange tip) is made the same, the wheelbase can be correct, but the running diameter is decreased and the drivers will look much too small.
So usually they find an intermediate solution. Of course, having the smallest feasible flange size is a big help in this.


That is true, except for the spacing (unless you have only 2 drivers) because the inner drivers do not have flanges. Some model manufacturers prefer not to make so many different wheels and use flanges also on the inner drivers. HP did not.
I thought that is was somehow wrong but then I found out that our little diesel 0-6-0 with spoked wheels did not have flanges on the middle axle either.
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Re: SP GS-4 Drive Wheels

Postby areibel » Wed Apr 22, 2015 10:44 pm

HP is HP Products, the originator of TT. They built several different steam locomotives, using three different driver sizes along with maybe a half a dozen different boiler castings, the frame was the only real piece unique to each model.
If you snoop around in the "Models" section under HP products you can see several examples, or Rob D. has a copy of one of the original catalogs on the Zeuke TT website. For example the 0-6-0, 0-8-0 and 2-8-0 were all built with small drivers and small boiler and cab. The built their Atlantic using the largest drivers along with the same small boiler and cab! The Mountains and Mikados used the medium sized drivers, but had different chassis and boilers. It's clever how they were able to use a little ingenuity to produce a bunch of different models!
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