Turbine Generator

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1 inch scale

1.5 inch scale

Design Principles

RichD wrote:

There are lots of ways to find an end to a problem, but don't overlook K.I.S.S. ! Think about the entire system and how it works, what is available for input and most of all, what you want out of it. I have built enough miniature "dynamos" to find that simple is as simple does.

  • 1.5" scale units must have small turbine wheels and the resulting need for high speeds.
  • A rotor built with speed in mind has no problem with 100K + RPM should it occur.
  • Steam issuing from a nozzle has a limited velocity and the blades will likely not attain 50% of that especially when driving a load. Always keep a load ON.
  • Control the steam feed with small pipe. 1/8" copper tube is plenty. Flow is controlled by the nozzle aperture. For best velocity use a venturi. Convergent-divergent tapers.
  • Don't forget the boiler operating range. Still having lights at 60 psi would be nice. So, having a wide range of output voltage followed by an electronic regulator is similar to the locomotive boiler. Reserve pressure is useful when needed.
  • Spinning magnets in a wound field makes an alternator (think automotive). Full wave rectify the output in the unit and ground the minus lead. Now one hot lead is all you need. Less mess. The loco chassis is ground (circuit return). Use Teflon #20 lamp leads.
  • A simple 3 terminal regulator chip (LM317 from Radio Shack) is adjustable and self limiting for over temp and current. It shuts down in case of a fault. Use as many as needed for different circuits/lamps. See the spec sheet for limitations (operating area).
  • Use low voltage lamps (large selection of 3V types - or LEDs) to avoid the need for large numbers of turns in the field thus allowing large dia wire to keep the internal resistance as low as possible. Resistance eats amps. #22 or 20 works well.
  • The schematic attached is as simple as it gets. Don't forget a heat sink.
  • The dyno can attain nearly 400° F in operation sitting on top of a boiler. Internal electronics have to be pretty tough to servive and work as well. Ventilation is a must.

By the way, the MO-6 Pyle National Dyno has 3 speed control systems built in. Centrifugal governor steam valve, over-speed brake and an eddy current drag disc for over-current. Can't fit all that in a miniature. Shaft rotates CCW. 3450 RPM. 32V. There are also 4 nozzles. Two primary and two secondary.

RichD toolman8(at)copper(dot)net

Locomotive Lighting Schematic

Pressure Regulator

Rich Carlstedt provided drawings for the Moseley pressure regulator:


Don Carr posted the following in Chaski.org, December 2003:

Here is a listing of construction articles and notes (both published and unpublished) on miniature working turbo-generators for live steam locomotives. I am going from the earliest material which I have to the more recent.
1. The Miniature Locomotive, September - October (part 1), November - December(part 2) 1952, "3/4 Inch Scale Steam Turbo-Generator" by R. E. Thompson. Refers to a design originally developed by Otha Hege of Lexington N.C.
2. Model Engineer, November 11, 1954 (part 1) and November 18, 1954 (part 2), "Miniature Steam Turbo-Generators" by E. Rowbottom (South Africa). This turbo-generator is for a 5 inch gauge locomotive.
3. Model Engineer, March 10, 1955, "A Miniature Turbo-Generator" by R. E. Thompson (U.S.A.) Basically, this is a technical summary of The Miniature Locomotive articles.
4. A blueprint sized 18 inch by 30 inch dated July 21/71, DWG C-5005 drawn by WHD with note "Original design by O. Hege in 1951. Modified and clarified by WHD 1971". I am certain that this print is one that I purchased from W. H. (Bill) Dykeman of York Central Railway, Prince Edward Island, Canada. A very clear, interesting and informative blueprint.
5. Model Engineer, 17 January 1986, "A Steam Turbo-generator" by Terry Timms. Designed for a 5 inch gauge Sweet Pea locomotive.
6. Live Steam, "A Turbo Generator" by Richard Chiapparelli, September/October 1998 (part 1) and November/December 1998 (part 2). Originally for a 1 inch scale Atlantic but increased in size for a 1-1/2 inch scale locomotive.
7. Unpublished notes taken in 1998 for a design and drawings (dated Feb 1983) by Ian Wynd of C.O.A.L.S (Central Ontario Association of Live Steamers) for a 3/4 inch modified and updated Hege/Thompson type turbo-generator. He made a number of these units and at one time some may have been sold through Miniature Power Products (Ted McJannett) but they are not available now. I have one photo showing the units disassembled and some of the tooling used in their construction.

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