Gear Systems

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Jet Model Products

211 North Mullen Road
Belton MO 64012

(816) 331-0356 - Voice

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            Tom Cook


	Landing Gear Door Cylinder 5/16" i.d. x 1" stroke 4-40 threads Overall length-2.8" .125 pivot/mounting hole

Retract Gear and Accessories

MK-20 Retract Gear System

The MK-20 Retract Gear System was designed to meet the needs of models in the 17-30 lb. weight range. It had to be light enough for ducted fan applications and tough enough for scale models operating from rough grass fields. It is hand-crafted from aircraft grade aluminum with an emphasis on simplicity of design and ruggedness.

The MK-20 operates off compressed air. The 2-way valve is controlled by a servo and activates the cylinders attached to each individual retract gear to either retract or extend the struts.

All of the gears are mechanically locked down and pressure held up. By eliminating the need for up locks and holding the gears retracted with pressure, it allows the modeler a variety of installations possibilities.

Many variations in strut geometry require less than 90 degrees of strut travel. It is possible with the MK-20 System to stop the gear retraction wherever desired by merely adding a stop in the wheel well.

The actual weight limitation on the gear is somewhere around 30 lbs. of aircraft weight, but this largely depends on the strut length, field conditions, and ultimately piloting techniques.

MK-20 RETRACTABLE LANDING GEAR	340.00
Mk-20 Main Gear (ea.)	110.00
Mk-20 Nose Gear (ea.)	120.00

MK-30 Retract Gear System

The MK-30 Retract Gear System was designed to meet the specific requirements of turbine models in the 20-35 lb. weight range. Light, but tough enough for models operating from rough grass fields, the MK-30 retract gear are CNC machined from aircraft grade aluminum with an emphasis on simplicity of design. Down locks and up locks are used with a 90 degree retraction angle as standard. Massive �� bored pivot blocks receive and clamp the upper strut body. The main gear struts retract away from the actuating cylinder and provide a high retracted strut center line. The nose gear strut can retract over the cylinder or away from the cylinder. The retract unit dimensions are as follows. Height 1.375�-Width 2.5�-Length 5.0�

A 2-way valve driven by a standard JR or Futaba mini servo controls the retract gear system. Installations that include gear doors utilize the JMP Gear Door Sequencer. The gear retraction and door closing is timed by the Sequencer. Also available is the Air Line Manifold which maintains equal line pressure and simplifies air line routing.

The actual weight limitation on the gear is somewhere around 35 lbs. of aircraft weight, but this largely depends on the strut length, field conditions, and ultimately piloting techniques.

MK-30 RETRACTABLE LANDING GEAR	775.00
Mk-30 Main Gear (ea.)	250.00
Mk-30 Nose Gear (ea.)	275.00

T-33 Scale Retracts 1205.00

The T-33 scale retract gear are built on the reliable MK-20 mechanisms and are scale right down to their shock absorbing struts and intricate detail. The full scale 6 degree forward retracted angles are duplicated precisely. The nose strut features a machined fork with scale wheel and tire.

Retract Gear Installation Kit 110.15

Featured in the retract installation kit are air tank, tubing, two-way valve, brass T�s, and 1-way fill valve to complete the package.

Gear/Door Airline Manifold (see Accessories page)	65.95
Firebird Retracts/Complete with struts, tires and brakes	1205.00
Brake Installation Kit	145.00
Retract Airline Tubing (I/f)	0.65
TAPERED FILL ADAPTOR WITH MINI-COIL A simple but effective way to couple your air pump to the 1-Way fill valve. Just push the tapered nylon fitting into the valve to create a temporary seal. The line automatically recoils, stays neat and out of the way. Available in red, green, or yellow. TAPERED FILL ADAPTOR WITH MINI-COIL 15.00 1-WAY FILL VALVE 22.00 see JMP Accessories .144 Airline Clamps 3.60 .144 plastic air line clamps for the retract gear cylinder fittings, air line manifold fittings, and door actuating cylinders.

T-Fittings Brass (4 per pack) 15.00

Wheels and Tires
T-33 Main Gear Tire 4.5"	14.85
Firebird Main Gear Tire 4.0"	38.50
T-33 Nose Gear Tire 3.5"	13.50
Firebird Nose Gear Tire 3.5"	13.50

JMP Gear/Door Sequencer 99.00

The JMP Gear/Door Sequencer has four timed control options available. These options are illustrated below. The servo that activates the door control valve is plugged into the top position with the black or brown negative wire to the inside. The servo that activates the retract gear control valve is plugged into the lower position with the black or brown negative wire to the inside.

Servo throw travel volume is preset to match most available control valves. The green LED on the top of the case indicates that the sequencer is active.

Contained in the sequencer computer code is a Gear Up Fail Safe. If the model receiver is turned on with the transmitter retract gear switch in the up position, both gear and door control servos will hold in the down position. Gear and door control servos will become active when the transmitter retract gear switch is returned to the down position. This fail safe feature will prevent accidental retraction of the gear on the ground. An easy way to understand this function is that the sequencer must see a down switch before it can respond to an up switch.

	Dip Switch Positions	Retraction Cycle	Extension Cycle
	1 2

Option #1	OFF OFF	Gear up	Door open
		3 second delay	1 second delay
		Door closed	Gear down

Option #2	OFF ON	Gear up	Door open
		5 second delay	1 second delay
		Door closed	Gear down

Option #3	ON OFF	Door open	Door open
		1 second delay	1 second delay
		Gear up	Gear down
		3 second delay	3 second delay
		Door closed	Door closed

Option #4	ON ON	Door open	Door open
		1 second delay	1 second delay
		Gear up	Gear down
		5 second delay	5 second delay
		Door closed	Door closed