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Lynch Motor Marine Drives

1. MOTOR CONTROLLER COMBINATIONS

These drive systems use Lynch motors and Curtis controllers in the appropriate combinations for continuous running. In all cases the limitation is the heat capacity of the electronic controller rather than that of the motor. It is found from experience that if the continuous current of the controller exceeds 25% of its peak current - which is the current that can be sustained for one minute - the controller may start to limit the output current at this value. However, the manufacturers quote a 1-hour rating of about 33% of peak current, and this will prove satisfactory for many applications.

In choosing the controller for a given maximum output a realistic assessment should be made of the continuous running time at peak current and the controller should be sized accordingly.

When comparing alternative products it is important to check that the same safety factor is being applied in each case - eg 25% or 33% of peak current. For a given power the maximum and continuous currents should be worked out using the following relation: Power in Watts = Volts x Amps.

The controllers have in-built thermal cutouts which automatically reduce the output current to a safe working level - there is, therefore, no danger of damage from overheating, but the controller will then be working at its limit which cannot be exceeded until it has been allowed to cool down.

The preferred drive systems have a tooth-belt and pulley reduction which has the following advantages:
a) More power is obtained by running the motors at higher speeds, and therefore a less costly motor can be used for a given application.
(b) Propeller speed can be precisely `tuned' to hull performance, to give the desired range and speed.
However in certain cases a direct drive to the propeller shaft may be required and this is also included in the
attached table.

Controllers should preferably be mounted on an aluminium plate - 3-6 mm thickness - as heatsink (See Sect. 3, Drive Panel). It is essential that the temperature of the air around the controller should not be higher than external ambient temperature. Controllers should NOT be mounted where they will pick up heat from the motor airstream. If mounted near the motor they should be in the cool inlet airstream. Where controllers are enclosed, we can supply a suitable fan ventilating kit to bring in fresh air from the exterior. In boats with metal hulls a section of the hull under water can be used as a heatsink if good thermal contact can be made with it.

2. SPECIFICATION OF DRIVE SYSTEMS

Electric Motor Suppliers

NOTES:
(1) R = Reduction drive, D = Direct Coupled, Contr = Controller supplied by Curtis UK.
(2) Speeds down to 250 rpm can be achieved with reduction gear if highest efficiency required.
(3) Curtis UK Ref, starts SC981- followed by 3-figure code given here.
(4) Curtis to issue code.

3. MOUNTING PLATE AND DRIVE-TRAIN

The Lynch motor is mounted on a slotted steel plate which allows for tooth-belt adjustment and also holds the reduction gearing and propeller thrust bearing in the correct positions for the reduction ratios required. (C1147, C1148)

The mounting plate can be supplied to a fixed size for mounting on brackets supplied by the customer or, at customers' request, the outside edges can be flame-cut to suit the hull profile, so that the plate can be bonded into the boat. In the latter case the customer should provide us with a full-size paper template of the profile to
be cut.

The standard drive is designed for a 25 mm dia. propeller shaft. Other sizes can be accommodated at a small extra cost.

4. DRIVE PANEL AND CABLES
The controller, circuit breakers for main and auxiliary circuits and cables/connectors for motor and batteries are mounted on an aluminium plate which also acts as heatsink for the controller.

Heavy current cable is supplied either in a continuous length of 12M with all necessary connectors to be cut and fitted by the customer, or cut to the following lengths with all end connections fitted.

Battery to drive panel 2 x 2M
Drive panel to motor 2 x 1.5M
Drive panel to drive head 2 x 2.5M

Cable size is 35 sq mm up to 2 Kw, and 50 sq mm above 2 Kw. Cables can be supplied in longer lengths at additional cost if specified by the customer.

All control cables are provided cut to length in a single harness with plug-in connectors and are tested at our works

5. DASHBOARD PANEL

A control drive-head, keyswitch and state of charge meter are mounted on an engraved panel for fitting to the boat's dashboard. Alternatively an elapsed time meter with ammeter and voltmeter can be fitted in place of the state-of-charge meter. The user will then know the total elapsed time that can be run at the current required for the preferred cruising speed.

Electrical contactors can be supplied to order where required, in which case a panel operating lever is provided. The drive-head contains forward, reverse and resistive braking contacts and also operates the controller at the required speed, all from a single pistol-grip handle on the panel.

The mechanical drive head has the advantage of reliability and simplicity of maintenance over the earlier arrangement of electrical contactors - of which 3 or 4 were required. These added to the cost and also consumed current unnecessarily, thus reducing the boat's range.

As an optional extra the mechanical drive-head can be mounted at up to 5 metres from the panel, operated by dashboard lever and mechanical cables.

5.2 Mechanical Control Heads

The control heads are based on a long-established design of rotary switch having silver-plated copper roller contacts running on massive silver-plated fixed contacts, giving a 2 second current rating of 2000 Amps. They are suitable for off-load switching in combination with electronic controllers up to 400 Amps. The control head for electronic controllers contains forward, reverse and resistive braking contacts and also operates the controller at the required speed, all from a single pistol-grip handle on the panel.
The mechanical drive head has the advantage of reliability and simplicity of maintenance over the earlier arrangement of electrical contactors - of which 3 or 4 were required. These added to the cost and also consumed current unnecessarily, thus reducing the boat's range.

As optional extras the mechanical drive-head can have a marine type push-pull lever mounted either through the dash panel, or up to 5 metres from the panel, operated by dashboard lever and stainless steel mechanical cables. This allows control head to be positioned close to motor/battery drive system allowing very short electrical high-current connections and avoiding the cost, complexity and power losses of long electrical cable runs.

The options are as follows:

5.21 Changeover switch only; forward, reverse and plug braking with resistor, permitting rapid reversing while in motion without damaging motor or controller, with pistol grip for mounting through panel.

5.22 As 5.21 with additional proportional output 0-5K resistance in both forward and reverse directions for driving electronic controller.

5.23 As 5.22 with marine type push-pull lever through slot in dash panel and engraved plate with forward, reverse and increasing speed markings.

5.24 As 5.23 with control head body separated from dash lever by up to 5 Metres of stainless steel mechanical cable.

6. BATTERIES

The sizing of the battery pack can be determined from our paper `Design of Electric Drives for Boats' (C1069) The batteries may be 6 Volt or 12 Volt monoblocs or they may be made up of separate traction cells. One advantage of traction cells is that they are relatively thin and can often be put in the keel of a boat - particularly in sailing boats where an auxiliary drive is required.

in general, for a boat of 5-8 metres a cruising time of 8 hours at about 4.5 knots will require a battery pack of about 250Kg.

A typical installation of this weight might comprise 8 off 6 Volt 175 Ampere-Hour monoblocs connected to give 350AH at 24 Volts, or 6 off 700AH traction cells giving 700AH at 12 Volts. Other combinations of cells would give the capacity required at voltages from 12 to 72.

We supply the following battery types: Monobloc, semi-traction
CMP - 3ET175 6V, 175AH (5hr), Weight 30Kg
- 3ET205 6V, 205AH (5hr), Weight 33Kg
- 3GMF161 6V, 161AH (5hr), Weight 32Kg, Maintenance-free

Banner- 96351 12V 140AH (5hr), Weight 48Kg

Traction
CMP to British Standard or DIN sizes.
Specific capacity is about 3 KwHrs per 100Kg at the 10Hr discharge rate.

 
         
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