-- MarkCutkosky - 7 May 2010 added link to Takram You Tube video

iSprawl is the first fully autonomous member of the Sprawl family and represents a transition between the Biomimetic Robotics MURI and the new RiSE project.
iSprawl development on this page:

AquaSprawl (April 2003)

The idea was to explore hydaulic power transmission to distribute power to the legs. The tubes contain water and the system works like hydraulic brakes on a car, with a single master piston and slave pistons at each leg. Aqua Sprawl is assembled in a bathtub to prevent air bubbles.

After many design iterations, including remachining the original Sprawlita pistons to put in double seals to handle negative pressure on the return stroke, a version of Aqua Sprawl was produced that ran fairly well:
A movie of Aqua-Sprawl

TIP Although Aqua Sprawl ran reasonably well, there is a fundamental limitation to the achievable speed because while retracting the pistons, only atmospheric pressure is available. On the other hand, this could be a good design for underwater use!

Cable Sprawl (iSprawl) (June, July 2003)

Following an undergraduate design project sponsored by MarkCutkosky during Spring 2003, it was decided to investigate low-friction push/pull cables instead of hydraulics. For more information on the cables, see the ME113 report.. Instead of the paint ball gun drive investigated by the ME113 students, I decided to try a crankshaft:

Click to see video

* push-pull cable.AVI: New push -pull cable leg thrusting system

The investigation culminated in a rough prototype with a styrofoam body. As the video shows, it is fast but unstable due to poor location of the center of mass and insufficient leg stiffness. (The legs are just bare cable ends):
* "StyrofoamSprawl": "Critical functional prototype" of New I-sprawl

iSprawl V1 (August 2003)

This version has an aluminum chassis and legs with flexures manufactured by ManufacturingHome, like the other Sprawl robots.

Click to enlarge picture

Click to see video

Top view Bottom view Side view

(June 2004)

NEW updated video and results Click the picture below!


New pictures (June 2004) of iSprawl v2


iSprawl V2: Retuned iSprawl is now running at 15 body-lengths/second (over 2.3m/s).

Details to be posted soon.
3Mb movie 14Mb movie

Click to see video

High speed video

Click to see video

Before I impliment axial(thrusting direction of the leg) compliance, the robot was less stable and much slower as video shows below.

Table of specifications for iSprawl V1:

Part Specification
Part Specification Weight
RC Servo
  • Model: cirrus CS-5.4
  • Torque(in-oz): 14 = 98 mNm (per Futaba conversion table )
  • Speed(sec/60deg): 0.1
  • Size(mm): 20*17.5*8
  • Type: Lithium Polymer Cells
  • Capacity: 3.7V 250mmAh per pack(5~6 pack)
: Advantages over Li-on is at


  • 250mmAh: 7g per each pack
  • 700mmAh: 16g per each pack
  • Model: Maxon 2.7W 2023909
  • size(mm): 23*31.4(dia*L)
  • Terminal resistance: 4.3 Ohm
  • Nominal speed(7.2V): 9000rpm
  • Maximum torque : 4.51mNm
  • Maximum current : 626 mA
  • Size(mm): 20*17.5*8
  • Model: Maxon 20:1
  • Type : spur gear- 4stage
  • size(mm): 24*17.4(dia*L)
  • Output axis Dia.: 3mm
  • Type : polyurethane 72DC & 90A by SDM
  • Small: joint with cable
  • Big : joint independent cable
  • Small : 2.6g
  • big : 4g
  • Cable & tubing
    • Type : Multistrand steel cable in teflon sheath D:0.84mm (0.03 in)
    • size : 0.84mm
    • tubing : Teflon 16 gauge
    • Steel ends : Dispensing needle 18 gauge
    • Holder : plastic nylon tube(ID=1.8mm OD=3.5mm)
  • Cable : 2.5g/m
  • Chassis,crank & Mounts
    • Chassis :Aluminum (CNC)
    • Mounts & Crank : Aluminum (Hand milled)
    • Cranks : double crank shaft driven by belt
    • stroke length : 2.54mm (1 inch)
    • Size(mm): 155*116*70 (without cables)
    • Power consumption : approx. 12W
    • Voltage : 19~22.5V (5~6 pack)
    • current : 0.5A
    • Motor speed: 20000rpm(when running)
    • Motor torque: ?
    • Robot speed: 2.3m/s (15 bodylength/s)
    • Stride frequency : 17 Hz
    315g (6 pack battery & RC receiver)

    Connections for iSprawl

    There are 3 battery power sources. Two of these sources (front and rear) are stacks of 3 Li-polymer batteries that are put in series to power the motor (~24V). The other (currently above the middle right servo motor) is used to power the servo/motor controller and receiver. The following steps may be useful to activate iSprawl.
    • Turn on the transmitter power (it should make a funky noise).
    • Connect the green tagged wires, black to black, red to red.
      • This activates the receiver and powers the servos
    • Connect the blue tagged wired, black to heat shrink (black), red to red.
      • This powers the motor, which has a mini, in-line circuit that blinks RED when in use.

    useful Links:

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