Requirements

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There are several test-driven-designable components that are required to make a high-performance module. Here are critical design points and solutions:

• Self-contained unit - the motor is included. The only interface design is 2-hose connection for wheel motors. Motors without case drain are used to facilitate hose routing by 30%.
• Tensioning - easily accessible 1” bolt heads are used to tension the motor, and to tension the track. Motor and track tensioning is separate.
• Tensioning must fix final location to 50k lb - ie, stiff to retain track tightness without loosening.
• Move the motor for tensioning drive chain. This isolates chain tensioning from track tensioning,
• Move the idler - this isolates the track tensioning from the main drive sprocket.
• Quick connection - ½” flush face spill-less couplers are used, ideally. 0.15 ml fluid leak upon connection?
• Wheel mounting - geometrical fit + clamp-down to facilitate removal, as opposed to tight tolerance + keyway. Allows dually and more wheels. Around a 4” square shaft.
• Dually config is possible - must retain access for purposes of tightening each wheel.
• Must have long mounting shaft, not weldment to another frame member
• Protected gearing - shroud covers the chain drive from the environment and for safety.
• Idler - must self-align the tracks on idler without friction. Obtained by a sprocket-on-idler
• Track tension must be tight, so that a chain skip condition is met with excess resitance that locks the track instead of track falling off. Track tension must be to 2” of tightness

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Evolution:

• Multiple motors - 2 motors driving each track
• Use case: it’s cheaper to add a motor-only to an existing track unit, than to add a new track unit
• Intensively Scalable Drive Torque - By virtue of using anywhere from 2500 in lb (6.1 cu in) to 9000 in lb motors. The bulk structure handles either for up to 13,000 lb with dual 9000 in lb motor track unit, limiting drive factor is motor torque. 1” pins and ½” track steel is used.
• Extensively Scalable Drive - One or 2 motors. Possibly 3. Dual vs single drive sprocket.
• Larger motors - it turns out that the larger 9600 in lb motors are 2x as cost effective for the drive motor for the TORQUE, but not for the POWER. For a small machine, the cost is $800 extra - but the machine speed would be correspondingly slower. The advantage of such a motor is not there - cost per horsepower is the same. We care about power over torque, as power is the speed of work done.
• For practical scalability, the small motor gets us great power matching to power source for 72 hp for single motors per track unit at 10 gpm, to 144 hp when driven at 20 gpm, to 288 hp when driven with dual motors (4 power cubes per motor)
• This appears to be more than sufficient for practical scaling needs, if we don’t mind the dual motors - meaning more part, though no more unique parts. Is unique part count in the system more important that overall part count?
• From the OSE perspective, the extensive scalability route appears more attractive in terms of providing more freedom, pending effective design-for-scalability.

Scalability

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1400 lb drive trike

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$7200 for 36 small (6.1 cu in) motors, octo-deka drive, dual per track 50klb, 2 mph, 1 engine/track unit/2 motors, or 4 mph with electronic controls (more advanced). 360 hp.

$14,400 for larger motors

Octodeka drive, 192k lb, larger motors have more complicated power requirements and larger valve needs.

Steel is about 8000 kg/m³

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50,000 lb octodeka drive

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Concept: even a single Universal Track Unit can drive a vehicle.

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Concept: use as many drive units as needed. Feasible only if each one is sufficiently simple to build.

Concept. Side View.

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Motor

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Sprocket Small

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Bolt

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Chain

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Large Chain Sprocket

Triangle steel

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Track Drive Sprocket

Pull on this plate to tension motor. Bolts are tightened after tensioning. Come up with a simple tension mechanism

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Nut

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Motor Mounting Interface Plate

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3” min sprocket to 12” sprocket - 4x geardown. May be 3x only if space is tight.

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Double Geardown Concept

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Design Concept

• General: allows for use of a common motor instead of expensive high torque wheel motor at 4x the cost
• Eliminates the wheel motor from being a major cost
• $190 motors instead
• Small sprocket - 3.35OD - 0.75 for active D of 2.6”, or active radius of 1.3”.
• Means 6000 lb torque on chain.
• 2.5 geardown means 5000 lb torque on chain
• 2 geardown means 4000 lb torque on chain
• Motors are 2560 in-lbs. Cont.Motors ar
• This calls for 3x reduction on tracks for 1920 lb drive per track
• r=4 for track drive
• This calls for 9x reduction max for wheels with 100 weight chain
• Working load up to 5000 lb?
• 2560 in lb torque * 9 = 23k in lb
• Means 1300 lb drive
• But we can make the second drive wheel larger, say 4x
• 2560*12=31k in lb - means 1700 lb drive
• How about we make both larger, 7 tooth to 25 tooth (25/7 = 3,57)
• 3.57 reduction at each step - 12.75 (2 steps = 3.57*3.57 = 12.75)
• Good for part count, bad for larger torque on second stage - 6000 lb pull on chain vs
• Hybrid is best
• 3 on first and 4 on second is desirable - 1700 lb drive - 6800 lb for 4 wheel configuration
• For longer life - 2x and 5x get 10x or 1400 lb drive - 5600 lb drive on a tractor. Marginal minimum with 3’ diameter wheels
• For track s, the latter 5x gives 2560 in lb * 5 / 4 in = 3200 lb drive per wheel unit! Spectacular.
• Speed - 742 rpm / 5 = 150 rpm at 4 inch radius or 1 meter per revolution makes 150 m/min = 5.6 mph.
• With 3x it is 9 mph tops and 1920 lb drive per unit - very good.

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Wheel Size vs Drive Force

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Tangent between wheel and ground determines pseudo-incline.

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Design Concept

• Small wheels means you are fighting pseudo-incline at all times
• Furthermore, wheel will sink more because of lower surface area, so the pseudoincline effect is amplified with small wheels for the same weight of machine.

Concept. Module Breakdown.

Chain

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Motor Drive module

Track Drive module

Motor Tensioner Module

Frame/Structure Module

Track Idler

module

Power Transmission

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Motor

Sprocket Small

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Bolt

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Chain

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Large Chain Sprocket

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How to Make a Keyway on a lathe

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Motor Mounting Interface Plate

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1-⅞” hub (off-the-shelf) with keyway and key welded to large chain sprocket. Needs keyway in shaft.

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Keyway

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Bolt

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Washer

Small Sprocket

Set Screw

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Small weld dot

shaft

Motor

shaft

Coupler

Track Drive module (cross-section)

Large Chain Sprocket

Set Screw

½” Key

Track Sprocket Coupler

Track Sprocket

Bearings

¼” space between shaft and triangle structure

To avoid rubbing

1-⅞” Hub

½” Key

⅜” Set Screw

(Hole in shaft is 1/16” larger)

Set Screw

Drive shaft

Motor Drive module (cross-section)

Motor

Sprocket Small

Bolt

Bolt

Washer

Small Sprocket

Set Screw

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Small weld dot

Coupler and Small Sprocket will be welded together

Source

Motor shaft

Coupler

Track Idler module (cross-section)

Track Sprocket

Bearings

¼” space between shaft and triangle structure

To avoid rubbing

⅜” Set Screw

(Hole in shaft is 1/16” larger)

Set Screw

½” Key

Track Sprocket Coupler

Idler shaft

Tensioning - Front view of Universal Track Unit

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Motor

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Easily accessible from outside - 1” bolt is turned to pull motor plate. Details of mechanism to be worked out.

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Nut

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Pull on this plate to tension motor. Bolts are tightened.

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Motor Plate

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Elongated bolt holes allow for motor tensioning

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Tensioning - Concept Detail

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Bolts in elongated holes through motor mount plate

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1” Pipe welded to motor mount plate

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Motor Mount Plate

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1” bolt

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1” nut

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1” nut welded to large structure triangle of track unit

Triangle Structure of Universal Track Unit (green)

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Welden on stop - allows bolt to spin freely so that stop pulls on the pipe when bolt is tensioned

Turning this bolt with a large socket (impact wrench) pulls the motor mount plate left to tension the drive chain

1” pipe

Tensioner Module (cross-section) - Variant 1

Hex Heat 1” bolt

Only when the head is fully outside the Triangle Structure it can be rotated to release the Mount Plate

1” nut

Turning it with a wrench will move the Mount Plate Inward/Outward

1” nut

Welded on Mount Plate

Sliding guides for Mount Plate

Triangle Structure of Universal Track Unit (green)

Mount Plate

(both for Motor and Ider)

Cost - Rough Budget is $1000/wheel unit

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Shafts

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Double Geardown Concept - Calculations

2560 lb-in (motor) / 1,675 in (7 teeth sprocket) = 1528 lb (force on chain 1)

MOTOR

1-⅞” SHAFT

3” SHAFT

FRAME

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1528 lb (force on chain 1) * 3,72 in (17 teeth sprocket) = 5684 lb-in (torque on 1-⅞” shaft)

5684 lb-in (torque on 1-⅞” shaft) / 1,675 in (7 teeth sprocket) = 3393 lb (force on chain 2)

3393 lb (force on chain 2) * 7,32 in (35 teeth sprocket) = 24837 lb-in (torque on 3” shaft)

24837 lb-in / 2560 lb-in = 9,7 geardown ratio

24837 lb-in (torque on 3” shaft) / 1,5’ (wheel radius)= 1380 lb (pull force on wheel)