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R/C Steam Turret Tank
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Email: dogsbody@steamhobby.com     Home: http://steamhobby.com


1. Credits & Specs
2. Mechanics  
3. Body  
4. Turret  
5. Materials
See Also:
Steam Tractor Tank
R/C Steam
Tractor Tank

Steam Locopede
R/C Steam
Locopede
Face Shovel Excavator
Steam
Face Shovel


1. Credits & Specs
  
The next generation in R/C steam tank design.   This is my second variation on Crabfu's Steam Lobster tank.   Fire, water, steam, motion!   After finishing my original tractor tank, I longed for one with a working turret & more power.  Thus my R/C live steam powered tank with turret & gun!   The build is a little complicated.   See build details in my Steam Turret Tank Instructable!

ChassisTamiya 1/16 King Tiger (clutch drive)
Power: MaccSteam 3.5" Horizontal Steam Boiler, two Regner Piccolo Steam Engines
Fuel: Propane/Butane mix (camping fuel)
Boiler Pressure: 30+ PSI
Body: Aluminum Sheet Metal & Brass Fittings
R/C: Spektrum DX6, one Futaba S3010 servos, four Spektrum S75 miniservos
Runtime: 15-20 minutes
Weight: 13 lbs (empty)
   

Steam Turret Tank
R/C steam engine powered turret tank




2. Mechanics

The R/C steam turret tank uses 100% steam power for propulsion.   Batteries only power the R/C, lights & gun effects

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

As before I used an old Tamiya 1/16 scale King Tiger (KT) tank from eBay.  There the similarities end.   The original gearbox slipclutch was removed, and gearbox frame shortened to make room for the new boiler, engines & fuel tank.

Motive power is generated by a MaccSteam 3.5" Horizontal Steam Boiler feeding two Regner Piccolo Marine steam engines.   Engine output is routed around the fuel tank with some reduction gears to increase torque.

The reduction gearing is 15t/38t on the engines, and 19t/56t on the gearbox.   Mounting brackets for the gear axles are made from 13 hole Meccano strips.  The ends are bent to fit within the chassis as shown below.

Regner Piccolo Engines Gearbox
Regner Piccolo Engines Gearbox

  
Fuel Tank
Fuel Tank

Reduction Gears
Reduction Gears

The engine mount holds the two engines & attaches to the chassis.

A 4" x 6" piece of 0.064" (1/16") aluminum is placed over the suspension brackets, and marked to locate the tabs. 1" slots are cut and the tabs bent as shown.

The tabs are ~1/2" deep, and carefully fitted between the suspension springs.  Adjust/trim as necessary.

A center punch is used to mark each tab, and drill through the bracket and chassis. Sheet metal screws attach the bracket from below.

  
Engine Mount Sketch
Engine Mount Sketch




A triangle of aluminum redirects whistle servo motion. The corner is anchored to the chassis. When the servo tugs horizontally, the other corner moves vertically.

A piece of brass chain connects the triangle and the whistle, and 1/16" brass rod to the servo control rod, with s-curves bent on both ends.

To mount to the chassis, I used a 3/16" standoff, a couple washers & sleeve for tightening the nut against while letting the bracket turn freely.


Whistle Control
Whistle Control




The servo mount bracket holds the engine servos, whistle servo, R/C receiveR/Controller, and battery pack.  It's made from 0.032" aluminum and has stiffening flanges bent on all four sides. A pocket for the receiver is formed with a couple more bends.

Servos are installed & holes marked & drilled for mounting holes.  The receiver & controller slip into the pocket. Pieces of cut-open 3/8" shrink tube & electrical tape insulate the electronics where necessary. The battery sits on the front of the bracket held by double-side sticky tape.


Servo Bracket Sketch
Servo Bracket Sketch
  
Manifold Bottom Steam Manifold Fitted Manifold Pipes
Manifold Side Steam Manifold
Steam Manifold Pictures

Steam from the boiler needs to reach the engines, whistle & displacement lubricator.

I fabricated a manifold from brass, and started with a 5/8" square brass rod.  I cut a 3/8" thick piece & drilled #1 holes in two sides and a face halfway through so they joined up inside.

The manifold tube is made from 5/16" solid brass rod, and drilled 5/32" through the center.   One end is #1 drilled & 1/4-40tpi tapped for the lubricator.   Two 0.1" holes are drilled for the engine feed pipes & 6-32tpi tapped.  Two brass standoffs are dirilled through & trimmed to just grab the tube threads, then everything was silver soldered together.

  


Manifold  Sketch
Manifold Sketch



3. Body

As before I based the look on Crabfu's steam lobster tank.

I penciled patterns onto 0.032" (1/32") K&S Aluminum sheets, checked symmetry with a ruler, and started cutting. If you've the grip, the K&S aluminum is soft enough to cut using scissors. Otherwise use metal shears, coping saw, metal nibbler, etc... Keep a file handy for cleaning up sharp edges.

After making one tail segment, it became the template for others. I curved the segments using a 3" PVC plumbing coupling as a form. I then trimmed the segments down to length.

The end-most segment is ~7-1/4" in length. Others are ~1/2" longer, but set at an angle.

The tail segments overlap so any given pair of segments shares one or two common mounting holes. Mahogany strips (1/8" x 1/4") give structure to initially hold the segments together.

  
Lobster Tail Sketch
Lobster Tail Sketch


Lobster Tail Segment Sketch
Lobster Tail Segment Sketch
Certain segments need openings for boiler fixtures & the funnel port. I eyeballed the location of these. Drill a starting hole, use a metal nibbler to rough the shape & file smooth.

Final positioning of segments depend your boilers fixture locations. To preserve the "lobster" look I made sure to keep the top-most lobster shell "points".

Lobster Tail Shaping
Lobster Tail Shaping

Body Rear
Body Rear



For the front of the body, first I made a u-shaped piece from a 4"x7" 6061 aluminum sheet.

It covers the fuel tank & supports the turret. It has a 2-3/4" diameter hole (based on a Meccano ring gear) for clearing the fuel tank valve, turret gears, wiring to the turret, etc... The 6061 aluminum coupled with the steel ring gear makes it strong enough.

Designing the remaining front panels took quite a while to flesh out. Lots of prototyping with paper, cardboard & tape. ie: cutting, bending, taping a little back on, repeat, etc... 

The sketch shows my final design. Once the side panel shape was final, I continued the curve onto the front-most lobster shell.

2-56 x 1/2" brass hex bolts, washers & nuts hold everything together except the front apron. It's held with #2 x 3/16" brass hex lag screws for battery access.
  
Body Panel Sketch
Body Panel Sketch

Gear Ring
Gear Ring

Body Front
Body Front



The track fenders are made from 3" x 18" strips of 0.032" 6061 aluminum. I used the stronger aluminum here since fenders are exposed to abuse.

I used a bending brake to make a 3/8" flange on the inner edge & 5/8" on the outer. The chassis tracks are 2" wide, so that determined the center-width.

Removing a couple inches of flange from the front/rear allows shaping the fender. I sketched a smooth curve which ended on the outer flange, rough cut with metal shears, and filed the edges smooth.

Holes were traced from the Mahogany strips made when assembling the body & 3/32" drilled. I kept the Mahogany strips in the final build to add extra width & enhance the look. Loctite secures the 2-56 nuts during final assembly.

The hand rails are made from 15mm flat stanchions and 1/16" brass rod. The stanchions are placed every 2 to 2-1/4" along the fender, bending in before the headlights. Drill mounting holes, insert stanchion mounting tab, and twist with pliers to affix.

Holes for head/tail lights were marked & drilled. The headlights are STE162 Gimbaled & Fixed Clear Searchlights. The tail lights STE152 Bullet-Style Navigation lights.
  
Fender Rough Cutout

Fender Shaped

Fender Drilled



4. Turret
 
A 3-1/4" diameter needle roller thrust bearing from eBay sits on the ring gear supporting the turret.

I fabricated an aluminum ring base with tabs for attaching the turret body. The outer diameter was determined by a 4"x10" sheet of K&S aluminum. The inner diameter matches the thrust bearing.

Upward bent tabs on the outer edge attach to the turret body. Downward bent tabs on the inner edge align the thrust bearing. Straight tabs on the inner edge are for idler gears & servo (see sketches). The gears keep the turret overall centered within the ring gear.
 
I reused a servo from the original tank here. The servo gear is cut from a 25T Meccano gear. It's 1/8" thick with a thin hub. A #1 hole was drilled about halfway through to fit the servo spline gear.

        

Turret Base Sketch
Turret Base Sketch


Thrust Bearing
Thrust Bearing
Turret Servo Gear
Turret Servo Gear


The turret body started simple (a cylinder), but I didn’t like the look so added the curved gun port bump-out & rear box structures.

The front bump-out is three pieces. Two sides & a curved front plate. Either freehand or use a drafting compass to sketch the curves onto some 0.032" aluminum. 2-56 brass bolts hold it all together.

The turret top is made from 0.064” (1/16") aluminum sheet, with Mahogany strips glued on. To attach the top to the turret body, several L brackets from scrap aluminum are glued on.

Finishing touches involved bending some 1/8" brass u-channel to hide the aluminum, and adding railings. I eyeballed positions for 15mm stanchions (same as fenders), drilled holes, and fitted/soldered the 1/16th brass rod railings. After painting, the turret sides are adorned with lion crests taken from some brass buttons.



The gun mount is a 4-1/8" x 5/8" aluminum rectangle folded into a narrow box, with a tab for the gun elevation servo. It's folded & the joint JB-Welded. A 5/32" hole drilled through is for the gun pivot axle. When bending its important to preserve the 1/2" internal gap otherwise the gun barrel doesn't fit.

The gun barrel is formed from two pieces of aluminum tube. A 1/2" tube and a polished smaller 3/8" tube that slides smoothly within.

A solenoid sits within the larger tube, and pulls the smaller one inwards to simulate cannon fire. Combined with an ultra-bright yellow LED, WTV020-SD sound module & Railmaster DHB8 8-ohm 2W miniature speaker (w/enclosure), the effect is pretty good!

The solenoid proved annoying since it dropped the battery voltage enough to brownout/reset/disconnect the R/C receiver & controller logic.  Some 1F capacitors & a current mirror for charging them fixed that problem.
       
Turret Unpainted
Turret Unpainted
Turret Top
Turret Top

Gun Mount Sketch
Turret Crest
Gun Port Sketch
Gun Port Sketch

Rear Housing
Rear Housing
Gun Barrel Sketch
Gun Barrel Sketch
Gun Barrel Assembly
Gun Barrel Assembly
  
Gun Barrel Parts
Gun Barrel Parts
Gun Mount Sketch
Gun Mount Sketch
Gun Mount Cutout
Gun Mount Cutout
Gun Mount Formed
Gun Mount Formed
Solenoid Driver Schematic
Solenoid Driver
 
Barrel Bottom View
Barrel Bottom View
Turret Assembly
Turret Assembly
Turret Bumpout Rear View
Turret Bumpout Rear View


R/C steam turret tank demo2

5. Materials List & Vendors
  • Other Supplies
    • Mahogany Strips (1/8" x 1/4" x 24")
    • Aluminum Standoffs (3/4")
    • Ceramic Fiber Paper (1/16")
    • High Temperature Engine Enamel Paint
    • Oak Trim Panel (3.5" x 24" x 1/4") - Boiler heat shields
    • Aluminum Sheets - 0.032" (1/32") and 0.064" (1/16") thicknesses
    • Brass Square (5/8") & Round rod (1/16", 5/16" & 1-1/4" sizes)
    • Brass 1-1/4" Round tube
    • Brass 1/8" U-Channel
    • Acetal Plastic Rod (3/8" diameter)
    • Zinc-Core Candle Wick (52-32-18)
    • Various screws/washers/nuts/etc...
    • Loctite Thread Locker, Cyanoacrylate glue, JB-Weld

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