GB2490674A

GB2490674A - Alternator adapter for radio controlled vehicle IC engines

Info

Publication number: GB2490674A
Application number: GB1107678.3A
Authority: GB
Inventors: Trevor George Butcher
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-05-09
Filing date: 2011-05-09
Publication date: 2012-11-14
Anticipated expiration: 2031-05-09
Also published as: GB201107678D0; GB2490674B

Abstract

An alternator adapter 18 for an internal combustion engine 10 of a radio controlled vehicle comprises a driveshaft 22 for mounting in-line with the rotational axis of a crankshaft 16 of the engine 10 and an eccentric pin 24 at one end of the driveshaft 22 for engagement in an aperture 42 machined into the crankshaft 16, whereby rotation of the crankshaft 16 causes rotation of the driveshaft 22. The adapter is retrofittable to existing engines and supported in a replacement or modified original engine backplate 28 having a bronze bearing bush 32 with lubricant aperture 36, a central adapter shaft aperture 30 and carrying a mounting plate 40 to which the alternator 14 is attached by fasteners. The alternator may be based on a brushless motor and feed a vehicle battery pack. Extends battery endurance and reduces likelihood of crashes due to flat battery electrical power failures especially in radio controlled helicopters.

Description

ALTERNATOR ADAPTER

The present invention relates to an alternator adapter and particularly to an alternator adapter for use with a radio controlled device and most particularly to an alternator adapter for use with a radio controlled helicopter.

BACKGROUND OF THE INVENTION

It is a well recognised problem of a radio controlled aircraft, and particularly a helicopter powered by an internal combustion engine, that the flight duration is relatively short. Flight time is limited by fuel, which may be a methanol and synthetic oil mixture, and also by the onboard battery life. A radio controlled helicopter is controlled by a number of battery powered servos. For example, a 7 channel computerised radio system may operate 5 separate helicopter mounted servos. An onboard battery is typically a 4.8 Volt or 6 Volt nickel-metal hydride (NiMH) battery pack or a lithium polymer (LiPo) battery pack of 7.4 Volts. A helicopter having, for example, a 1.4m diameter rotor and an 8.2cc engine requires a battery capacity of around 2000 milliampere-hours (mAh).

In testing, it has been found that the current demand during flight varies from 0.2 Amps with the helicopter in a static position to around 3.0 Amps whilst manoeuvring, with 5 servos under load. Depending on the nature of the flying, e.g. gentle circuits or aerobatics, battery life is around 30 to 45 minutes. A tank of fuel may last typically around 12 to 15 minutes and therefore the battery pack needs recharging or replacing every 3 flights. This is a time consuming process and can be difficult, for example, at locations where there are few or no facilities. It will be appreciated that a loss of battery power results in usual catastrophic loss of the helicopter, with the associated risks to property and people.

One solution to the problem is to mount a larger battery pack in the helicopter with an increased capacity. However, this is only alleviates the problem to some very limited degree, because the increased weight of the battery pack becomes a problem and can severely limit performance and the balance of the aircraft.

The seriousness of the implications of losing electrical power during flight has led some model aircraft flyers to fit visual voltage checkers in the form of multiple LED displays on the side of the aircraft enabling a flyer to monitor the real time voltage being supplied from the aircraft's battery.

It is an object of the invention to provide an alternator adapter which reduces or substantially obviates the above mentioned problems.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided an alternator adapter for fitting to an internal combustion engine of a radio controlled vehicle comprising a driveshaft for mounting in-line with the rotational axis of a crankshaft of the internal combustion engine, an eccentric pin mounted at one end of the driveshaft for engagement in an aperture in the crankshaft, rotation of the crankshaft causing rotation of the driveshaft.

Preferable and/or optional features of the first aspect of the invention are set forth in dependent claims 2 to 8.

The adapter is advantageous, because it enables an alternator to be fitted to a remote controlled vehicle. This is highly desirable, particularly for a helicopter, because the engine typically generates an excess of power and the engine speed is high during most phases of flight.

According to a second aspect of the invention there is provided an internal combustion engine for fitting to a radio controlled vehicle, the internal combustion engine comprising a crankshaft with an aperture in an end thereof, a driveshaft for mounting in-line with the rotational axis of a crankshaft of the internal combustion engine, an eccentric pin mounted at one end of the driveshaft for engagement in the aperture in the crankshaft, rotation of the crankshaft causing rotation of the driveshaft.

Preferable and/or optional features of the second aspect of the invention are set forth in dependent claims 10 to 16.

I

According to a third aspect of the invention there is provided a radio controlled vehicle including an alternator adapter in accordance with the first or second aspects of the invention. The radio controlled vehicle may be a radio controlled helicopter.

The radio controlled vehicle may further comprise first and second light emitting elements for indicating operation of the alternator. The alternator adapter may be ananged intermediate the first and second light emitting elements. For example, the light emitting elements may be arranged visibly on or in sides of the radio controlled vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which: Figure 1 shows a side view of a single cylinder internal combustion engine of the type used in model aircraft fitted with an alternator adapter and alternator; Figure 2 shows an enlarged cross-sectional view of part of the single cylinder internal combustion engine, alternator and alternator adapter of Figure 1; Figure 3 shows a schematic perspective view of the driveshaft, backplate and alternator prior to assembly; Figure 4 shows a schematic view of the assembled driveshaft, backplate and alternator; Figure 5 shows a schematic view of an exemplary alternator rectifier circuit used in conjunction with the alternator; and Figure 6 shows a side view of a radio controlled helicopter fitted with the alternator adapter and alternator of Figure 1.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

With reference to Figures 1 to 4, a typical internal combustion engine for a radio controlled vehicle is indicated generally at 10. The engine 10 is a single cylinder engine with output shaft 12. The engine 10 has been adapted to drive an alternator 14 from the crankshaft 16 of the engine 10.

Refening particularly to Figure 2, the alternator 14 is connected to the engine 10 by means of an adapter 18, which is mounted to the crank case 20 of the engine 10. The role of the adapter 18 is to impart rotary motion from the crankshaft 16 to the alternator 14. The adapter 18 includes a driveshaft 22, and an eccentric pin 24 mounted at one end of the driveshaft 22. The eccentric pin 24 extends from a circular disc 26, which is balanced by several holes in the disc. The adapter 18 may be made from metal or metal alloy.

The original backplate forming part of the crank case 20 of the engine 10 has been removed and replaced with a new backplate 28. Alternatively, the original backplate of the crank case could be modified to provide the same features as the new backplate 28.

A central aperture 30 is provided through the backplate 28 and a bronze bush 32, which serves as a bearing is disposed around the aperture 30 within the backplate 28, on the engine 10 side of the backplate 28. It is envisaged that other types of bearing may be used. The driveshaft 22 of the adapter 18 is sized and shaped so as to be receivable into the central aperture 30 of the backplate 28. Furthermore, the driveshaft 22 is engageable with the alternator 14 so as to provide a driving engagement.

A circular recess 34 is provided in the end of the backplate 28, facing the engine 10, as more clearly shown in Figure 3. The shape of the recess 34 corresponds to the shape of the disc 26 of the adapter. As such, an alternative shaped recess 34 may be implemented provided that it corresponds with the shape of the disc 26. Preferably, the depth of the recess 34 is or is substantially the same as the thickness of the disc 26.

The circular recess 34 is provided centrally about the central aperture 30.

Optionally, a bore 36 is provided through the backplate 28 from one side thereof, to the upper side as viewed, for supplying oil from the engine 10 to the aperture 30 through the bronze bush 32.

A plurality of internally threaded apertures 38 is provided in the backplate 28 to facilitate connection with the alternator 14. The said apertures 38 extend into an external face of the backplate 28, spaced from the bore 36. In this arrangement, the alternator 14 is mounted to the backplate 28 via a mounting plate 40 using fastening means which couple with the apertures 38.

The crankshaft 16 of the engine 10 includes an aperture 42 which is utilised for engagement with the eccentric pin 24 of the adapter 18. The aperture 42 should be shaped so that it corresponds with the shape of the lateral cross-section of the eccentric pin 24 so that the aperture 42 and the eccentric pin 24 are interconnectable.

If the crankshaft does not already include an aperture, then one could be machined into the crankshaft.

The alternator 14 is preferably a brushless alternator 14 to reduce the number of wearing parts. Typically, the alternator 14 is based on a 90 Watt, 1100kV brushless motor which is modified to accept the driveshaft 22. The driveshaft 22 of the adapter 18 drives the magnetic rotor (armature) 44 of the alternator 14. The field windings 46 of the alternator 14 are stationary and fixed to the backplate 28 using the alternator stator plate 47 and mounting plate 40.

Turning now to Figure 5, a battery 48 is provided in electrical communication with the alternator 14 via a rectifier circuit, indicated generally at 50. Operation of the alternator 14 produces a three phase output to the rectifier circuit 50.

The battery 48 may be a 6 Volt NiMH battery or a 7.4 Volt LiPo battery. It is the battery 48 that initially supplies the electrical energy required to operate any servo motors of the radio controlled vehicle. In time, the alternator 14 becomes the source of electrical energy, as will be described in further detail below.

S

The rectifier circuit 50 includes a plurality of rectifier diodes (Dl to D6) 52, a 3 Amp Schottky diode (low forward voltage drop, D7) 54, 150 mA silicon diodes (D8 to D9) 56, 1⁄2 Watt resistors (Ri to R2) 58 and, optionally, a 100 mA voltage regulator 60.

This rectifier circuit 50 is provided for example only and alternative suitable rectifier circuits may be used. The voltage regulator 60 is not essential since it is not required when the alternator 14 acts uniquely as a power source for servos on the remote control system. It should be noted that the alternator 14 may include an onboard battery charging circuit for which the voltage regulator 60 controls the voltage/current depending on the type of battery being used, i.e. NiMH or LiPo. As such, the alternator 14 may have dual functionality: to act as a direct power source and also to act as a recharging system. Operation of the battery charging circuit typically only occurs when the engine 10 is running at 9500rpm and above. Voltage/current regulation ensures overcharging cannot occur, whilst ensuring that the battery 48 retains a reasonable amount of charge.

The rectifier circuit 50 typically outputs 8 to 16 Volt for use in the radio control system 62. This is well in excess of a 6 Volt, 3 Amp demand typical of a radio control circuit for a radio controlled vehicle.

One or more light emitting elements 64 may be included as part of the electric circuitry to indicate operation of the alternator 14. Preferably, the or each light emitting element 64 is a light emitting diode.

In use, as indicated in Figure 6, until the engine 10 speed reaches 9500 rpm, the battery 48 acts as the main source of electrical power for the radio controlled vehicle, which in this Figure is shown as being a helicopter 66. Above 9500rpm, using solid state circuitry, the alternator 14 becomes the main source of electrical power and the battery 48 temporarily becomes redundant in flight. The transition between the two power sources is automatic and occurs seamlessly, thus providing a steady power supply to the radio control system 62. Use of the battery 48 generally only occurs at the beginning and end of flight.

Should for any reason the engine 10 fail mid-flight and therefore operation of the alternator 14 halt, the radio control system 62 is able to continue to function due to the battery 48.

A light emitting element 64 is disposed on either side of the helicopter body 68 and provides a visual confirmation to the pilot of the helicopter 66 that the alternator 14 is acting as the main power source.

Although the alternator adapter 18 has been described in use with a helicopter, the radio controlled vehicle may be a motor boat, aeroplane or land vehicle.

The alternator adapter 18 provides peace of mind to the pilot that the power source should not fail mid-flight, thereby avoiding or reducing the risk of the aforementioned consequences. With the alternator 14, it is possible to operate the helicopter all day without having to recharge the battery.

Worked Example

Taking the model above as an example, a typical 8.2cc (0.50 cu in) engine produces 1.2 to 1.8 HP (900 -1350 Watts) depending on the manufacturer. The normal operating speed of the engine is between 13,000 to 16,000 rpm depending on model of helicopter and the style of flying. The power required to drive the alternator on average load of 6 Volt/2 Amp is about 12 Watts. Allowing for only 65% efficiency, overall the average power required would be 18 Watts. This equates to 1.5%-2.0% of the engine power. This power requirement has been shown to have a negligible effect on the engine/helicopter in flight, during which full power is used for short durations only.

Typical Installation Weight Alternator: 36 grams (1.3oz) Control circuit 18 grams (0.63oz) Backplate/shaft 48 grams (1.7oz) Total: 102 grams (3.6oz) Less original backplate: -16 grams (0.S6oz) Total: 86 grams (3.Ooz) For reference Total model weight (T-REX 600 with 0.5 cubic inches engine): 3.20kgs (7lbs) 6 Volt NiMH battery: 146 grams (5. loz) 7.4 Volt LiPo battery: 96 grams (3.4oz) If a 7.4 Volt LiPo battery was substituted for the equivalent NiMH battery, this would result in a mass saving of 50 grams. If the alternator was then fitted, the total weight would increase by 36 grams (1.3oz). This mass increase can easily be accommodated by the capability of the exemplary model of helicopter.

It is understood that variations may be made in the foregoing without departing from the scope of the invention. For example, the elements and teachings of the various illustrative embodiments may be combined in whole or in part in some or all of the illustrative embodiments. In addition, one or more of the elements and teachings of the various illustrative embodiments may be omitted, at least in part, and/or combined, at least in part, with one or more of the other elements and teachings of the various illustrative embodiments within the scope of the claims.

Although illustrative embodiments of the invention have been shown and described, a wide range of modification, changes and substitution is contemplated in the foregoing disclosure. In some instances, some features of the invention may be employed without a corresponding use of the other features within the scope of the claims.

Claims

CLAIMS1. An alternator adapter for fitting to an internal combustion engine of a radio controlled vehicle comprising a driveshaft for mounting in-line with the rotational axis of a crankshaft of the internal combustion engine, an eccentric pin mounted at one end of the driveshaft for engagement in an aperture in the crankshaft, rotation of the crankshaft causing rotation of the driveshaft.
2. An alternator adapter as claimed in claim 1, in which a backplate is provided for attachment to a crankcase of the internal combustion engine, the backplate having a bearing mounted therein for receiving the driveshaft and an aperture for allowing the driveshaft to pass through the backplate.
3. An alternator adapter as claimed in claim 2, in which the backplate bearing is a bronze bush.
4. An alternator adapter as claimed in claim 2 or 3, in which an aperture is provided through the backplate for supplying oil to the bearing.
5. An alternator adapter as claimed in any one of claims 2 to 4, in which a circular disc is mounted co-axially at the end of the drive shaft and the eccentric pin extends from the circular disc.
6. An alternator adapter as claimed in claim 5, in which a circular recess for receiving the circular disc is provided in the backplate.
7. An alternator adapter as claimed in any one of claims 2 to 6, in which the driveshaft extends through the aperture in the backplate and is in driving engagement with an alternator.
8. An alternator adapter as claimed in claim 7, in which a plurality of internally threaded apertures are provided in the backplate for receiving fastening means for attaching the alternator to the backplate.
9. An internal combustion engine for fitting to a radio controlled vehicle, the internal combustion engine comprising a crankshaft with an aperture in an end thereof, a driveshaft for mounting in-line with the rotational axis of a crankshaft of the internal combustion engine, an eccentric pin mounted at one end of the driveshaft for engagement in the aperture in the crankshaft, rotation of the crankshaft causing rotation of the driveshaft.
10. An internal combustion engine as claimed in claim 9, in which a backplate is attached to a crankcase of the internal combustion engine, the backplate having a bearing mounted therein for receiving the driveshaft and an aperture for allowing the driveshaft to pass through the backplate.
11. An internal combustion engine as claimed in claim 10, in which the backplate bearing is a bronze bush.
12. An internal combustion engine as claimed in claim 10 or 11, in which an aperture is provided through the backplate for supplying oil to the bearing.
13. An internal combustion engine as claimed in any one of claims 10 to 12, in which a circular disc is mounted co-axially at the end of the drive shaft and the eccentric pin extends from the circular disc.
14. An internal combustion engine as claimed in claim 13, in which a circular recess for receiving the circular disc is provided in the backplate.
15. An internal combustion engine as claimed in any one of claims 10 to 14, in which the driveshaft extends through the aperture in the backplate and is in driving engagement with an alternator.
16. An internal combustion engine as claimed in claim 15, in which a plurality of internally threaded apertures is provided in the backplate for receiving fastening means for attaching the alternator to the backplate.
17. A radio controlled vehicle including an alternator adapter as claimed in any one of claims ito 8.
i8. A radio controlled vehicle including an internal combustion engine as claimed in any one of claims 9 to 16.
19. A radio controlled vehicle as claimed in claim 17 or claim 18, in which the radio controlled vehicle is a radio controlled helicopter.
20. A radio controlled vehicle as claimed in claim 19 when dependent on claims 7 or 15, further comprising first and second light emitting elements for indicating operation of the alternator.
21. A radio controlled vehicle as claimed in claim 20, in which the alternator adapter is ananged intermediate the first and second light emitting elements.
22. An alternator adapter substantially as described herein with reference to and as illustrated in Figures 1 to 6 of the accompanying drawings.Amendments to the claims have been filed as followsCLAIMS1. An alternator adapter for fitting to an internal combustion engine of a radio controlled vehicle comprising a driveshaft for mounting in-line with the rotational axis of a crankshaft of the internal combustion engine, an eccentric pin mounted at one end of the driveshaft for engagement in an aperture in the crankshaft, rotation of the crankshaft causing rotation of the driveshaft, and a backplate for attachment to a crankcase of the internal combustion engine, the backplate having a bearing mounted therein for receiving the driveshaft, a through aperture for allowing the driveshaft to pass through the backplate and a bore provided in the backplate to the bearing for supplying oil from the engine to the bearing.2. An alternator adapter as claimed in claim 1, in which the bore extends from one side of the backplate to the bearing. C\J3. An alternator adapter as claimed in claim 1 or 2, in which the backplate C\J bearing is a bronze bush.C) 20 4. An alternator adapter as claimed in any preceding claim, in which a circular C"J disc is mounted co-axially at the end of the drive shaft and the eccentric pin extends from the circular disc.5. An alternator adapter as claimed in claim 4, in which a plurality of holes are provided in the circular disc for balancing the eccentric pin extending from the circular disc.6. An alternator adapter as claimed in claim 4 or 5, in which a circular recess for receiving the circular disc is provided in the backplate.7. An alternator adapter as claimed in any preceding claim, in which the driveshaft extends through the aperture in the backplate and is in driving engagement with an alternator.8. An alternator adapter as claimed in claim 7, in which a plurality of internally threaded apertures are provided in the backplate for receiving fastening means for attaching the alternator to the backplate.9. An internal combustion engine for fitting to a radio controlled vehicle, the internal combustion engine comprising a crankshaft with an aperture in an end thereof, a driveshaft for mounting in-line with the rotational axis of a crankshaft of the internal combustion engine, an eccentric pin mounted at one end of the driveshaft for engagement in the aperture in the crankshaft, rotation of the crankshaft causing rotation of the driveshaft, and a backplate attached to a crankcase of the internal combustion engine, the backplate having a bearing mounted therein for receiving the driveshaft, a through aperture for allowing the driveshaft to pass through the backplate and a bore provided in the backplate to the bearing for supplying oil from the internal combustion engine to the bearing. c\J10. An internal combustion engine as claimed in claim 9, in which the bore (\,J extends from one side of the backplate to the bearing.C) 20 11. An internal combustion engine as claimed in claim 10 or 11, in which the C\I backplate bearing is a bronze bush.12. An internal combustion engine as claimed in any one of claims 9 to 11, in which a circular disc is mounted co-axially at the end of the drive shaft and the eccentric pin extends from the circular disc.13. An internal combustion engine as claimed in claim 12, in which a plurality of holes are provided in the circular disc for balancing the eccentric pin extending from the circular disc 14. An internal combustion engine as claimed in claim 12 or 13, in which a circular recess for receiving the circular disc is provided in the backplate.15. An internal combustion engine as claimed in any one of claims 9 to 14, in which the driveshaft extends through the aperture in the backplate and is in driving engagement with an alternator.16. An internal combustion engine as claimed in claim 15, in which a plurality of internally threaded apertures is provided in the backplate for receiving fastening means for attaching the alternator to the backplate.17. A radio controlled vehicle including an alternator adapter as claimed in any one of claims 1 to 8.18. A radio controlled vehicle including an internal combustion engine as claimed in any one of claims 9to 16.19. A radio controlled vehicle as claimed in claim 17 or claim 18, in which the radio controlled vehicle is a radio controlled helicopter.20. A radio controlled vehicle as claimed in claim 19 when dependent on claims 7 or 15, further comprising first and second light emitting elements for indicating operation of the alternator. r(.1 21. A radio controlled vehicle as claimed in claim 20, in which the alternator o 20 adapter is ananged intermediate the first and second light emitting elements.22. An alternator adapter substantially as described herein with reference to and as illustrated in Figures 1 to 6 of the accompanying drawings.