US20110033235A1

US20110033235A1 - Concrete finishing trowel with speed control

Info

Publication number: US20110033235A1
Application number: US12/699,430
Authority: US
Inventors: Rob Leggitt; Jeff Gao
Original assignee: BARTELL MORRISON Inc
Current assignee: BARTELL MORRISON Inc
Priority date: 2009-02-03
Filing date: 2010-02-03
Publication date: 2011-02-10

Abstract

A concrete finishing trowel includes a frame, a power source supported on the frame and having an output shaft, at least one rotor assembly supported on the frame. Each rotor assembly comprises a driven rotor shaft with a plurality of trowel blades extending outwardly therefrom so as to rest on a surface to be finished and to rotate with said driven rotor shaft to finish a respective circular area. A transmission system operably couples the power source output shaft to the driven rotor shaft of the at least one rotor assembly. The transmission system includes a variable driving pulley operable coupled directly or indirectly to the power source output shaft and including a resiliently deflectable portion that is movable to change the effective drive diameter of the variable driving pulley, and a variable driven pulley operably coupled to the variable driving pulley with a belt. The variable driven pulley in turn is operably coupled directly or indirectly to the driven rotor shaft of the at least one rotor assembly. A rotor speed control system permits an operator to adjust the center-to-center distance between the pulleys, thereby to cause the drive diameter of the variable driven pulley to change resulting in an adjustment of the speed of the driven rotor shaft.

Description

FIELD OF THE INVENTION

The invention relates generally to concrete finishing trowels, and more particularly to a concrete finishing trowel having a rotor speed control system and a concrete finishing trowel having a steering force assistance system.

BACKGROUND OF THE INVENTION

Various machines are available for smoothing or otherwise finishing wet concrete. Of the known varieties of such machines, self-propelled finishing trowels, and particularly riding finishing trowels, are particularly useful for finishing large sections of concrete more rapidly and efficiently than, for example, their manually-pushed counterparts.
Riding concrete finishing trowels typically include a mobile frame including a deck, with two or more rotor assemblies mounted on an underside of the deck. Each rotor assembly includes a driven rotor shaft extending down from the deck and a plurality of trowel blades mounted on and extending radially out from the bottom end of the driven rotor shaft. The trowel blades are supported on the surface to be finished. The driven rotor shafts of the rotor assemblies are driven by one or more engines that also mounted on the frame of the finishing trowel. The one or more engine is typically coupled to a respective driven rotor shaft via at least a gearbox. The weight of the finishing trowel and the operator is transmitted frictionally to the concrete by the rotating blades, thereby smoothing the concrete surface.
The individual blades usually can be tilted relative to their supports, via operation of a suitable mechanical lever and linkage system accessible by an operator seated on an operator's platform in order to alter the pitch of the blades. When this is done, the pressure applied to the surface to be finished by the weight of the machine is altered. This blade pitch adjustment permits the finishing characteristics of the machine to be adjusted. For example, during a finishing operation, the operator may first perform an initial “floating” operation in which the blades are operated at low speeds (on the order of about 30 rpm) but at high torque. Then, the concrete is allowed to cure for another 15 minutes to one-half hour, and the machine is operated at progressively increasing speeds and progressively increasing blade pitches up to the performance of a finishing or “burning” operation at the highest possible speed. It is known to perform the burning operation at preferably above about 150 rpm and up to about 200 rpm.
In order to provide for steering of a power finishing trowel, the driven rotor shafts of the rotor assemblies are typically also tiltable relative to the frame. By tilting the driven shafts of the rotor assemblies, the operator can cause the forces imposed on the concrete surface by the rotating blades to propel the vehicle in a direction extending perpendicularly to the direction of driven shaft tilt. For example, tilting at least the driven shaft of the rotor assembly from side-to-side and fore-and-aft steers the vehicle in the forward/reverse and the left/right directions, respectively. Whereas the driven rotor shafts of both rotor assemblies should be tilted for forward/reverse steering control, it is known that only the driven shaft of one of the rotor assemblies needs to be tilted for left/right steering control.
It is known to drive rotor assemblies of the typical riding finishing trowel by a drive train that is connected directly to input shafts of the assemblies' gearboxes via a centrifugal clutch and a system of shafts, belts or chains, and other torque transfer elements of constant speed ratio. The drive trains typically require universal joints to accommodate tilting of the gearbox relative to the remainder of the drive train during a steering control operation. Alternatively, a flexible shaft may be employed, as discussed in U.S. Pat. No. 6,250,844 to Sartler et al., the contents of which are incorporated entirely herein by reference.
Various other proposals for drive trains in riding finishing trowels include variable ratio transmissions, such as that disclosed in U.S. Pat. No. 5,967,696 to Allen et al. In the patent, Allen et al. discuss a variable gear drive unit comprising a variable ratio pulley driven by a motor. A second pulley drives the gear box input shaft, with a drive belt entrained between the pulleys. A linear actuator causes the linear displacement of portions of the variable ratio pulley to change the effective pulley diameter.
In known concrete finishing trowels, operators achieve variations in rotor speed by adjusting the speed of the engine. While indeed rotor speed is adjustable in this way, there is the significant problem that the reduction in engine speed brings about a concomitant reduction in delivered power. This results in insufficient torque at the trowel blades. Therefore, improvements in the transmission of power from the engine to the driven rotor are desired.
Another issue known to those familiar with the concrete finishing trowel industry is that, after having used riding finishing trowels for an extended period of time, an operator can become physically fatigued. One cause of such physical fatigue is the requirement to repeatedly push and pull the steering handles against frictional forces so as to tilt the driven rotors thereby to steer the machine. As such, improvements in steering control and comfort are therefore also desired.
It is therefore an object of the present invention to provide a novel concrete finishing trowel.

SUMMARY OF THE INVENTION

Accordingly, in one aspect there is provided a concrete finishing trowel comprising:
a frame;
a power source supported on the frame and having an output shaft;
at least one rotor assembly supported on the frame, each rotor assembly comprising a driven rotor shaft with a plurality of trowel blades extending outwardly therefrom so as to rest on a surface to be finished and to rotate with said driven rotor shaft to finish a respective circular area;
a transmission system operably coupling the power source output shaft to the driven rotor shaft of the at least one rotor assembly, comprising:

- a variable driving pulley operable coupled directly or indirectly to the power source output shaft and including a resiliently deflectable portion that is movable to change the effective drive diameter of the variable driving pulley;
- a variable driven pulley operably coupled to the variable driving pulley with a belt, and operably coupled directly or indirectly to the driven rotor shaft of the at least one rotor assembly; and

a rotor speed control system for permitting an operator to adjust the center-to-center distance between the pulleys,
wherein a change in the center-to-center distance causes the drive diameter of the variable driven pulley to change thereby to adjust the speed of the driven rotor shaft.
The concrete finishing trowel described herein provides advantages over prior devices due at least in part to its ability to provide both automatic torque response and operator-adjustable speed control. Whereas prior concrete finishing trowels required the operator to achieve variable speeds by adjusting the speed of the engine itself, the concrete finishing trowel described herein permits rotor speed control while maintaining a level of engine speed that delivers sufficient power and thus torque for the rotors to operate effectively during finishing.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described more fully with reference to the accompanying drawings in which:

FIGS. 1 a to 1 d show various views of a concrete finishing trowel according to an aspect of the invention;

FIG. 2 is a perspective view isolating portions of the engine, transmission and rotor assembly portions of the concrete finishing trowel of FIG. 1;

FIG. 3 is a perspective view isolating portions of the transmission and rotor assemblies portions of the concrete finishing trowel of FIG. 1;

FIGS. 4 is a perspective view isolating portions of the steering system and portions of the rotor assemblies of the concrete finishing trowel of FIG. 1;

FIGS. 5 a and 5 b are a perspective views isolating portions of the steering system including a steering assistance subsystem of the concrete finishing trowel of FIG. 1; and

FIG. 6 is a perspective view isolating the steering assistance subsystem shown in FIG. 5.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Turning now to FIGS. 1 a to 1 d (hereinafter referred to as FIG. 1 for brevity), a riding concrete finishing trowel in accordance with a preferred embodiment of the invention is shown. The riding concrete finishing trowel comprises a rigid frame, an upper deck mounted on the frame, an operator's platform or pedestal provided on the deck, and right and left rotor assemblies. The right and left rotor assemblies respectively extend downwardly from the deck and support the finishing trowel on the surface to be finished. The rotor assemblies rotate towards the operator, or counterclockwise and clockwise, respectively, to perform a finishing operation.
A conventional ring guard is positioned at the outer perimeter of the finishing trowel and extends downwardly from the deck to the vicinity of the surface to be finished. The pedestal is positioned longitudinally centrally on the deck at a rear portion thereof and supports an operator's seat. Preferably, the pedestal and operator's seat can be pivoted via hinges (not shown) to permit access to components of the machine located thereunder, such as the machine's engine. Vibration damping means are provided for reducing the vibration imparted to the operator's seat. An operator presence switch is mounted beneath the operator's seat. A fuel tank is disposed on the deck, beside the pedestal. On the opposite side of the pedestal is a fluid tank for an integral retardant spray system. An electrical system, including four headlights for easing nighttime operation of the concrete finishing trowel at the site, is protected against the unwanted ingress of water and dust in accordance with the IP55 qualification set by International Electrical Standards (IEC).
Each rotor assembly is coupled to a respective worm-drive gearbox. The driven rotor shaft of each rotor assembly extends downwardly from its gearbox, and a plurality of circumferentially-spaced trowel blades are supported on the driven rotor shaft via radial support arms. The trowel blades extend radially outwardly from the bottom end of the driven rotor shaft so as to rest on the concrete surface. As can be seen, in this embodiment the trowel blades are mountable on multiple axial locations on the support arms, so as to enable an operator to alter the diameter of the circular area covered by each rotor assembly between finishing operations. The circular areas may be made to overlap by selective placement of the trowel blades on the support arms. Each gearbox is mounted on the undersurface of the deck but is tiltable relative to the deck for steering, as will be described.
The pitch of the trowel blades of each of the right and left rotor assemblies can be individually adjusted by a dedicated blade pitch adjustment assembly. The pitch blade adjustment is preferably electrically actuated. Alternative blade pitch adjustment systems are described in the above-noted U.S. Pat. No. 6,250,844 to Sartler et al., and U.S. Pat. No. 2,887,934 to Whiteman, the contents of which are incorporated entirely herein by reference.
Both rotor assemblies, as well as other powered components of the finishing trowel, are driven by a power source such as a gasoline powered internal combustion engine that is mounted under the operator's seat. It will be understood that the size of the engine will vary with the size of the machine and the number of rotor assemblies powered by the engine. For example, the illustrated two-rotor, 48″ machine typically will employ an engine of about 25 hp. A catalytic converter system is coupled to the engine exhaust and supported on the frame.
The rotor assemblies are operably connected to the engine via a unique transmission system and, along with their respective gearboxes, can be tilted for steering purposes via a unique steering system as will be described.
FIG. 2 is a perspective view isolating portions of the engine mounted on the frame, the transmission and the rotor assembly portions of the concrete finishing trowel of FIG. 1. FIG. 3 shows the various isolated portions without the engine. The output shaft of the engine is coupled to a clutch, which in turn is coupled to a driven pulley via a belt. The driven pulley is rotatably mounted on a jack shaft that is supported within the subframe of the concrete finishing trowel. The other end of the jack shaft is connected to a variable driving pulley which, via a variable driving belt, is coupled to a variable driven pulley. A U-joint drive shaft is coupled to the variable driven pulley via a shear pin hub, and extends to the tiltable right rotor assembly via its respective tiltable worm gearbox. The shear pin hub receives a shear pin which acts as a mechanical fuse of sorts to mechanically couple the rotor assemblies to the power source. As would be understood, the shear pin is designed to break under predetermined conditions such as overload or impact, thereby to impart little or no damage through the transmission system to the engine. A broken shear pin is easily replaced by an operator in the field and thus is a simple, inexpensive and effective way by which certain components of the concrete finishing trowel can be shielded from costly damage.
Another U-joint drive shaft extends from the variable driven pulley to another tiltable worm gearbox which is, in turn, coupled to the left driven rotor. During a steering operation, the tiltable worm gearboxes move in unison with their respective rotor assemblies, as permitted by the U-joint drive shaft.
In operation, rotational power is transmitted via the driven pulley to the variable driving pulley, then to the variable driven pulley via the variable driving belt, via the U-joint drive shafts to respective worm gearbox and finally to the respective rotor driven shafts of the rotor assemblies.
The variable driving pulley includes a resiliently deflectable portion that is automatically movable to change the effective drive diameter of the variable driving pulley in response to changes in torque. In this embodiment, the resiliently deflectable portion is one half of the pulley that is biased to a “home” position relative to the other half of the pulley. When the deflectable pulley half moves away from its other half, the variable driven pulley belt traverses a smaller pulley diameter, thus causing the variable driven pulley, and accordingly the driven rotor, to turn slower. A spring biases the deflectable pulley half back towards its home position. As the deflectable pulley half moves back towards the home position, the variable driven pulley belt traverses a larger pulley diameter, thus causing the variable driven pulley and accordingly the driven rotor, to turn faster.
The resiliently deflectable portion will move automatically as the operating conditions fluctuate, accordingly widening the space between the pulley halves. Thus, such changes permit the engine speed to remain constant through changes in the rotational speed of the rotors.
Advantageously, the concrete finishing trowel is provided with a rotor speed control system that permits an operator of the machine to adjust the speed of the driven rotors without necessarily adjusting engine speed. In order to decrease the driven rotor speed of rotation, the operator turns a speed control handle (shown as item 1 in FIG. 3) clockwise. Turning the speed control handle clockwise causes a yoke end to move upwards. This counterclockwise turns a front control shaft to which the yoke end is connected (when viewed from the right of the machine in FIG. 3). Turning of this front control shaft causes the tie rod to which it is connected to shift to the left (again, when viewed from the right of the machine) causing in turn the rear control shaft to which the tie rod is connected to rotate counterclockwise. As the rear control shaft is rotated counterclockwise, the shaft supporter that supports the shaft connecting the driven pulley and the variable driving pulley is moved upwards. As the shaft is moved upwards, the variable driving pulley is accordingly caused to move away from the variable driven pulley. More particularly, the center to center distance between the variable driving pulley and the variable driven pulley is increased. At this point, the tension on the variable driving belt increases so as to cause it to force itself between the two pulley halves of the variable driving pulley. As a result, the deflectable pulley half is pushed away from its other half, and the effective pulley diameter is decreased. This decrease leads to a decrease in the speed of the variable driving belt and accordingly a decrease in the speed of the driven rotors.
In order to increase the driven rotor speed of rotation, the operator turns the speed control handle (shown as item 1 in FIG. 3) counterclockwise. Turning the speed control handle counterclockwise causes the yoke end to move downwards. This clockwise turns the front control shaft to which the yoke end is connected (when viewed from the right of the machine in FIG. 3). Turning of this front control shaft causes the tie rod to which it is connected to shift to the right (again, when viewed from the right of the machine) causing in turn the rear control shaft to which the tie rod is connected to rotate clockwise. As the rear control shaft is rotated clockwise, the shaft supporter that supports the shaft connecting the driven pulley and the variable driving pulley is moved downwards. As the shaft is moved downwards, the variable driving pulley is accordingly caused to move towards the variable driven pulley. More particularly, the center to center distance between the variable driving pulley and the variable driven pulley is decreased. At this point, the tension on the variable driving belt decreases and due to the spring-influenced resilience of the deflectable pulley half the pulley halves are moved closer together. As a result, the effective pulley diameter is increased. This increase leads to an increase in the speed of the variable driving belt and accordingly an increase in the speed of the driven rotors.
It will be understood that, at any given speed set by the operator of the concrete finishing trowel, the transmission system will still have automatic torque response because the deflectable pulley half will be able to move relative to its other half in response to changing conditions. As such, a manually adjustable speed control with integrated automatic torque response has been provided in a triple reduction transmission system
FIGS. 4 is a perspective view isolating portions of the steering system and portions of the rotor assemblies of the concrete finishing trowel of FIG. 1. The steering system comprises a pitch sensor bracket, a limit switch adjustment bracket, a gearmotor, a pin-block U-joint, a screw jack, a jack mount bracket, a yoke arm, a limit switch, a pressure plate, a switch mount bracket, and a steering control arm. The steering system is supported on the subframe of the concrete finishing trowel.
FIGS. 5 a and 5 b are perspective views isolating portions of the steering system including a steering assistance subsystem of the concrete finishing trowel. A control panel supports operator hand grips and gauges for giving an operator visual indications of trowel blade speed in revolutions per minute, the relative degree of blade pitch, the battery charging status, the fuel level, the total run hours, a “system on” indicator lamp, and a “low oil pressure” indicator lamp. It will be understood that other indicators and controls can be supported on the control panel. The control panel is supported atop a single steering column, which is pivotable in various directions to, in conjunction with a steering assistance system (shown in isolation in FIG. 6) change the position of left- and right-side steering control arms in order to accordingly tilt the driven rotors in the rotor assemblies to effect steering. The left-side steering control arm is mounted onto the back of the left side gearbox, while the right-side steering control arm is mounted on the back of the right side gearbox. A steering bracket is fixed to the vertical steering shaft within the steering column, and there is no relative movement between the steering bracket and the steering shaft.
In order to propel the concrete finishing trowel forward during operation, the operator grips both hand grips and pushes the steering column forward so as to pivot within a spherical bearing (see item 13 in FIG. 6). The steering bracket 14 then moves forward and the ends of the rods 26 and 27 move forward. In turn, the steering shafts 9 and 28 are turned counterclockwise (when viewing FIG. 5 a from the left side), and the pivot plates 3 and 29 are turned clockwise. Ends of rods 2 and 30 then move downwards and both gearboxes are tilted so as to cause the concrete finishing trowel forwards.
In order to propel the concrete finishing trowel backwards during operation, the operator grips both hand grips and pulls the steering column backward so as to pivot within a spherical bearing (see item 13 in FIG. 6). The steering bracket 14 then moves backwards and the ends of the rods 26 and 27 move backwards. In turn, the steering shafts 9 and 28 are turned clockwise (when viewing FIG. 5 a from the left side), and the pivot plates 3 and 29 are turned counterclockwise. Ends of rods 2 and 30 then move upwards and both gearboxes are tilted so as to cause the concrete finishing trowel to travel backwards.
In order to turn the concrete finishing trowel to the left, the operator pulls the left hand grip and pushes the right hand grip. The vertical steering shaft accordingly is turned counterclockwise (when viewed from the top). The rod end 26 then moves backwards and rod end 27 moves forwards. Accordingly, the left side steering shaft 9 turns clockwise while the right side steering shaft 28 turns counterclockwise. When this occurs, the left side pivot plate 3 turns counterclockwise and the right side pivot plate turns clockwise. As this occurs, the rod end 2 moves up and the rod end 30 moves down. The left side gearbox accordingly tilts outside and the right side gearbox tilts inside, causing the concrete finishing trowel to turn left.
In order to turn the concrete finishing trowel to the right, the operator pushes the left hand grip and pulls the right hand grip. The vertical steering shaft accordingly is turned clockwise (when viewed from the top). The rod end 26 then moves forwards and rod end 27 moves backwards. Accordingly, the left side steering shaft 9 turns counterclockwise while the right side steering shaft 28 turns clockwise. When this occurs, the left side pivot plate 3 turns clockwise and the right side pivot plate turns counterclockwise. As this occurs, the rod end 2 moves down and the rod end 30 moves up. The left side gearbox accordingly tilts inside and the right side gearbox tilts outside, causing the concrete finishing trowel to turn right.
In order to move the concrete finishing trowel laterally to the left, the operator moves both hand grips to the left. The vertical steering shaft is thereby caused to move leftwards about its pivot point on the spherical bearing 13, and the steering bracket 14 accordingly moves left. The rod end 24 moves left, while the L/R pivot plate 17 turns counterclockwise. The L/R steering lever 8 then turns counterclockwise and the rod end 25 moves up. Accordingly, the right side gearbox is caused to tilt backwards (when viewed from the top), causing the concrete finishing trowel to move left laterally.
In order to move the concrete finishing trowel laterally to the right, the operator moves both hand grips to the right. The vertical steering shaft is thereby caused to move rightwards about its pivot point on the spherical bearing 13, and the steering bracket 14 accordingly moves right. The rod end 24 moves right, while the L/R pivot plate 17 turns clockwise. The L/R steering lever 8 then turns clockwise and the rod end 25 moves down. Accordingly, the right side gearbox is caused to tilt forwards (when viewed from the top), causing the concrete finishing trowel to move right laterally.
FIG. 6 is a perspective view isolating the steering assistance subsystem shown in FIGS. 5 a and 5 b. The steering assistance subsystem makes it easier for an operator to move the vertical steering column from its neutral position. Springs 16 are compressed, such compression being adjustable by way of movable adjusting nuts 18 and lock nuts 19 being moved up- or downwards. A cross pivot bracket 22 is pivotable about pin 32 on vertical steering shaft 12, and pivot bracket 15 is pivotable about the pins on cross pivot bracket 22. As a result, pivot bracket 15 can remain parallel to the pressure plat 10 under the equal pressure of the four springs 16, while the vertical steering shaft 12 moves in the spherical bearing 13.
At a neutral position, the four springs are compressed, and accordingly push the pivot bracket vertically downwards to the centre of the spherical bearing 13. When the vertical steering shaft is moved either backwards or forwards by the operator of the concrete finishing trowel, the pivot bracket moves forwards or backwards causing the springs to leave their neutral position. The springs extend and provide a level of assisting force to push the steering shaft in the direction in which it has been moved. As a result, the vertical steering shaft tends to remain in the position in which it is moved by the operator to provide assistance to the operator. A similar operation occurs when the vertical steering shaft is moved either backwards or forwards.
When the vertical steering shaft is twisted as described above, the pivot bracket is turned, causing the springs to extend and provide twisting force assistance.
While the above has been set out with reference to an embodiment, it will be understood that alternative embodiments that fall within the purpose of the invention set forth herein are possible.
Although embodiments have been described with reference to the drawings, those of skill in the art will appreciate that variations and modifications may be made without departing from the spirit and scope thereof as defined by the appended claims.

Claims

1. A concrete finishing trowel comprising:

a frame;

a power source supported on the frame and having an output shaft;

at least one rotor assembly supported on the frame, each rotor assembly comprising a driven rotor shaft with a plurality of trowel blades extending outwardly therefrom so as to rest on a surface to be finished and to rotate with said driven rotor shaft to finish a respective circular area;

a transmission system operably coupling the power source output shaft to the driven rotor shaft of the at least one rotor assembly, comprising:

a variable driving pulley operable coupled directly or indirectly to the power source output shaft and including a resiliently deflectable portion that is movable to change the effective drive diameter of the variable driving pulley; and

a variable driven pulley operably coupled to the variable driving pulley with a belt, and operably coupled directly or indirectly to the driven rotor shaft of the at least one rotor assembly; and

a rotor speed control system for permitting an operator to adjust the center-to-center distance between the pulleys,

wherein a change in the center-to-center distance causes the drive diameter of the variable driven pulley to change thereby to adjust the speed of the driven rotor shaft.

2. The concrete finishing trowel as defined in claim 1, wherein said power source comprises an internal combustion engine.

3. A concrete finishing trowel as defined in claim 1, wherein said transmission system further comprises a gearbox from which said driven rotor shaft extends and which tilts relative to said frame during a steering operation, said gearbox having an input shaft which is operatively coupled to said variable driven pulley via a U-joint drive shaft.

4. A concrete finishing trowel as defined in claim 1, wherein each of the at least one rotor assembly further comprises a plurality of support arms which extend radially outwardly from said driven shaft and on which said trowel blades are mounted, and wherein said trowel blades are mountable on multiple axial locations on said support arms so as to alter the diameter of said circular area.

5. A concrete finishing trowel as defined in claim 4, wherein said finishing trowel is a riding trowel comprising at least two rotor assemblies each for finishing a respective circular area.

6. A finishing trowel as defined in claim 5 and further comprising:

a deck mounted on the frame;

an operator's pedestal positioned on said deck; and

an operator's seat supported by said pedestal;

wherein said pedestal and said seat are hingedly attached to said deck to permit access to components of said finishing trowel located thereunder.

7. The concrete finishing trowel of claim 1, further comprising:

a shear pin hub associated with the variable driven pulley, the shear pin hub adapted to receive a shear pin for mechanically coupling the at least one rotor assembly to the power source, wherein a shear pin is designed to break under predetermined conditions thereby to mechanically decouple the at least one rotor assembly from the power source with little damage.

8. A concrete finishing trowel comprising:

a frame;

a power source supported on the frame and having an output shaft;

a transmission system operably coupling the power source output shaft to the driven rotor shaft of the at least one rotor assembly;

a steering system comprising a steering column operably coupled to the rotor assembly and operable to tilt the rotor driven shaft relative to the frame thereby to effect a steering operation, the steering system comprising a steering assistance subsystem operable to provide mechanical assistance to aid an operator when moving the steering column away from a neutral position.

9. The concrete finishing trowel of claim 8, wherein the transmission system comprises:

a variable driving pulley operable coupled directly or indirectly to the power source output shaft and including a resiliently deflectable portion that is movable to change the effective drive diameter of the variable driving pulley;

a variable driven pulley operably coupled to the variable driving pulley with a belt, and operably coupled directly or indirectly to the driven rotor shaft of the at least one rotor assembly;

the concrete finishing trowel further comprising: