R/C Steam Tractor Tank
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Email: dogsbody@steamhobby.com     Home: https://steamhobby.com

1. Credits & Specs
2. Mechanics  
3. Body  
4. Materials

See Also:
Steam Locopede
R/C Steam
Face Shovel Excavator
Face Shovel
Turret Tank
R/C Steam
Turret Tank

1. Credits & Specs
Much kudos to Crabfu for his Steam Lobster tank.   All R/C steam & fire goodness.   I took one look & decided I must have one.   You can't buy these things off the shelf, so that meant building it!  

ChassisTamiya 1/16 King Tiger (clutch drive)
Power: Regner MIDI Marine Plant, plus PM Research steam whistle
Fuel: Propane/Butane mix (camping fuel)
Boiler Pressure: 30+ PSI
Body: Aluminum Sheet Metal & Brass Fittings
R/C: Spektrum DX6, two Futaba S3010 servos, one Spektrum S75 miniservo
Runtime: 15-20 minutes
Weight: 13 lbs (empty)

r/c steam engine powered tractor tank

2. Mechanics

Like Crabfu's lobster, my R/C steam tank uses 100% steam power for propulsion.   All told it took about 3 months to assemble, although a good portion of that was searching out then waiting for parts & various tools to arrive.   Much less than a month of actual fabrication, spending a couple hours per night cutting metal, drilling holes, etc... 

King Tiger King Tiger Inside
Tamiya 1/16 King Tiger Tank

The rc steam tractor is based on an old Tamiya 1/16 scale King Tiger (KT) tank from eBay, so there are numerous mechanical differences from Crabfu's 1/16 Leopard tank based design.  

The gearbox layout is dissimilar and located at the front of the tank, the torsion bar suspension complicates mounting brackets, and the chassis rear is open after the plastic body-work is removed.   For my tractor, I reversed things placing the gearbox at the back.

As did Crabfu, I used a Regner MIDI Marine plant for boiler & steam engine to replace the KT's original electric motor.   Not cheap -- nothing about live-steam is cheap -- but is compact & gives plenty of power. 
Regner MIDI Marine Plant
Regner MIDI

Engine Mounted Engine Transfer Axle
R/C Steam Engine Mount

The boiler & fuel tank base-plate was replaced with one fabricated to fit around the KT's torsion spring suspension.   The motor was fitted to a bracket sitting on top the KT's gearbox.   Meccano sprocket gears & chain drop to a 4mm axle, one end filed to match the original pinion gear. The pinion gear subsequently powers the unmodified skid steering clutch & gearbox.

I ground the axle by first sliding on two oiled flanged bushings, which were then held in my vise.   Attach a drill & you've a crude lathe.   Once running I carefully filed the 4mm axle down to 0.125" matching the pinion, occasionally adding more oil to the flanges.

New Brackets
Mounting Brackets
Wood heat shields made from oak protect the plastic Tamiya skid clutch (behind the boiler) and the servos (in front).   The rear heat shield is wrapped with aluminum on the clutch side, to avoid engine oil spatter soaking into the wood.

A PM Research whistle was added to the boiler.   Minor challenge there, since the whistle takes a 1/4" 40TPI threaded pipe, and the boiler a 6mm 0.75 pitch metric (M6x0.75) threaded pipe.  Fortunately the boiler threads are close to 1/4" 32TPI, so I took a 1/4-40 to 1/4-32 adapter & rethreaded the latter section.
PM Research Whistle

A bracket was fabricated to hold the servos & front heat shield in place.  Another bracket holds the R/C receiver, headlight adapter & battery.    The headlight adapter is basically a light switch controlled directly by the Spektrum receiver.

Servos control the skid steering clutch, engine reverse/throttle valve, and rc steam whistle.   All servos are tucked into the front of the tank, hidden behind the front heat shield.   For the most part, only control rods are visible when looking down into the boiler section.   A triangular shaped bracket redirects the horizontal whistle servo motion into a vertical tug on the whistle chain. 

Headlight Adapter


Internal Pictures

3. Body

Obviously, I based the tractor-tank's body on Crabfu's lobster.   I used ideas from both his concept drawings & metal work.   I also added various wood trim & brass fittings, in keeping with the organic Victorian Steampunk theme.

The body is mostly composed of 0.032" K&S Aluminum sheets, which are easy to cut & bend.   The design used up quite a few of them.   Hand tools, drill & a vise were all that it took.   Fasteners on the finished tank are brass hex screws, for a classic bolted-together look.   None of the fasteners are decorative -- they're all holding something together.

Tank before Painting

Other than a couple rough drawings, I mostly fabricated on the fly, starting with the lobster tail.   I penciled patterns onto the aluminum, checked symmetry with a ruler, started cutting, then filed away any rough edges.   After making one tail segment, it became the template for the others.

Next I made the track fenders (from a larger sheet bought at Home Depot), side boiler panels, then finally the various front end elements.  Some brass u-shape channel trim covers the raw aluminum edges around the boiler and front deck plate.

The open section in the center makes it easy to see the steam motor & boiler.   The lobster tail does a good job hiding the King Tiger gearbox.   The front aluminum top plate was J-B Welded (high temp epoxy) to brackets hidden inside, then trimmed out with Mahogany decking strips.   The strips were first attached to a dark paper backing, then to the deck plate as an assembly.

Thermal paint, soldered brass railings, search headlamps (functional!), and Union Jack attached to the KT's old antenna add some finishing touches.    Still left to do is blackening of the metal tracks & perhaps adding some brass portholes along the side.

Tank after Painting

4. Materials List & Vendors
  • Tamiya 1/16 King Tiger 56004 (from eBay)
  • Spektrum DX6 Radio & AR6000 Receiver
  • Two Futaba S3010 servo's & one Spektrum S75 miniservo
  • Meccano Sprockets 3/4" diameter, 1" diameter, plus chain (from eBay)
  • Other Supplies (Home Depot, Kragen, etc...)
    • Mahogany Strips (1/8" x 1/4" x 24") - Body trim
    • High Temperature Engine Enamel Paint
    • Oak Trim Panel (3.5" x 24" x 1/4") - Boiler heat shields
    • Aluminum Sheets (6" x 18" x 1/32") - Track fenders
    • 4-32 screws/washers/nuts
    • Loctite Thread Locker
    • J-B Weld

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