CROSS REFERENCE TO RELATED APPLICATIONS
BACKGROUND OF THE INVENTION
[0002] Bicycle rollers have been in use since the early 1900's. A bicycle roller is a dynamometer
for bicycles that is powered by the bicycle rider. A bicycle roller is traditionally
comprised of three rotatable cylinders positioned so that the rear wheel of the bicycle
rides on two closely-spaced cylinders, and the front wheel of the bicycle rides on
a third cylinder. In the typical application, the cylinder under the front wheel is
coupled to one of the cylinders under the rear wheel by an elastic band such that
the front cylinder is forced to rotate at approximately the same speed as the rear
two cylinders. This allows the rider to control the bicycle, with steering enabled
due to the rotation of the front wheel.
[0003] In the prior art, the amount of power, or wattage, that the bicyclist is required
to exert to ride at a given speed on a bicycle roller was determined by the amount
of rolling resistance resulting from tire distress as the tire rolls over each of
the cylinders plus the wattage required to drive any external devices which exert
resistance on one or more of the cylinders. Rolling resistance is predominantly a
function of the cylinder diameter, tire pressure, and bicyclist weight. Relying on
these factors alone provides a linear relationship of resistance versus speed. Simple
devices that add a predictable amount of resistance such as the magnetic eddy-current
device of
U.S. Patent 6,857,992 (incorporated herein by reference) can be added externally to the cylinders, but
these are undesirable since they provide a linear speed-to-resistance relationship.
[0004] Prior art bicycle rollers have a linear relationship of speed versus resistance.
This solution is unsatisfactory; when beginning to pedal the bike from rest on rollers,
low resistance is desired to allow the wheels to accelerate quickly enough to enable
sufficient steering dynamics to keep the bicycle stable on the rollers, however, to
obtain a meaningful training session, a high amount of resistance is desired when
pedaling at a rate suitable to achieve cardiovascular exercise benefit.
[0005] To achieve both objectives it is desired to have a "progressive" resistance relationship
with speed. In other words, a non-linear relationship between speed and resistance
where the slope of resistance versus speed increases with increasing speed is desired.
This relationship is preferred because it mimics the non-linear effect of combined
rolling resistance and wind resistance experienced when riding a bicycle in traditional
fashion.
[0006] Stationary trainers that use devices external to the rollers, such as fluid resistance,
friction, air-moving technologies or variable magnetic resistance devices (see
U.S. Patent 7,011,607, incorporated herein by reference) are designed to resemble realistic bicycle riding
conditions. Each of these devices is external to the roller. Other than adding this
type of device to a bicycle roller, and driving it through a power-transmission device,
or through a complicated mechanical coupling to one of the driven cylinders, no attempt
has been made to fully integrate progressive resistance technology within the drum
of a bicycle roller so that external devices are not necessary. As such, an improved
bicycle roller is desired.
SUMMARY OF THE INVENTION
[0007] This disclosure describes an improved progressive resistance device suitable for
integration with a bicycle roller training device. The progressive resistance device
is a conductive cylinder, or drum, having an outer wall defining an internal chamber.
One or more magnets is carried on a magnet carrier and housed within the internal
chamber and in proximity to the wall. Eddy currents produced in the conductive cylinder
as the cylinder spins alter the magnet's proximity to the wall by forcing the magnet
carrier to move in an eccentric orientation as relates to the axis of rotation of
the cylinder. A torsional spring opposes the force created by the eddy current and
causes the system to achieve a state of equilibrium force balance.
[0008] With the cylinder oriented such that rotation allows the magnet carrier to move against
the torsional spring, the result is a progressive relationship between speed and resistance.
[0009] Another benefit of the progressive resistance device described herein is that when
a linear relationship between speed and resistance is desired, the cylinder may be
reversed - such that the cylinder rotates in the opposite direction described above
- allowing the same progressive resistance device to provide either linear or proportional
training depending on the direction of rotation of the cylinder. With the progressive
resistance device reversed, the result will be a linear relationship of speed and
resistance. Therefore, the progressive resistance device described herein is unique
in that it allows the user to select progressive resistance or linear resistance,
as desired. The ability to make this selection is important because a user training
on rollers on any given day may prefer high wattage or low wattage at high speed.
In practice, the progressive resistance device is removable from the frame and is
reversible, to allow the user to select linear or progressive resistance.
[0010] For most bicycle riders, the use of a trainer having a single progressive resistance
device described herein may be adequate. However, because a bicycle roller comprises
three cylinders, typically identical, the use of one, two, or three progressive resistance
devices described herein may be used in the place of the roller's cylinders to achieve
differing levels of resistance.
[0011] By adjusting the spring rate, spring preload, number of magnets and other variables
it is possible to adjust the progressive relationship between resistance and speed
to suit the needs of the designer or the user.
[0012] An additional embodiment of this technology to achieve a higher level of resistance
on a single cylinder is to include stationary magnets on the outer side of the progressive
resistance device placed and oriented in such a way that: a) when the progressive
resistance device is at rest, the poles of the moveable magnets inside the cylinder
oppose the stationary magnets outside the cylinder, thereby reducing the magnetic
flux on the conductive cylinder wall and b) when the progressive resistance device
rotates during its normal operation, the moveable magnets inside the cylinder approach
stationary magnets on the outside of the cylinder in such a way that the magnets are
attracted by appropriate pole alignment, thereby increasing the magnetic flux on the
conductive cylinder wall.
[0013] Further, the progressive resistance device described herein is applicable to other
stationary trainers, such as those sold for use with bicycles, handcycles and tricycles
(see
U.S. Patents 7,011,607,
7,585,258,
6,964,633, and
6,042,517, each incorporated herein by reference). The progressive resistance device described
herein is distinguishable from the magnetic resistance system for rollers (
U.S. Patent 6,857,992, incorporated herein by reference) in that the progressive resistance device automatically
adjusts resistance level relative to speed, rather than being manually adjustable.
[0014] Applications of this technology are not limited to bicycle rollers and bicycle trainers,
but are suitable in any application where a resistance mechanism is employed and it
is desired that the resistance mechanism have a non-linear relationship to speed,
such as a stationary bicycle, hand cycle ergometers, and any similar device. Because
the progressive resistance device described herein is contained within a cylindrical
drum and requires only that the outer cylinder be rotated, it can be driven by direct
contact with a bicycle tire, or it can employ a chain and sprocket, a drive belt or
it can be driven directly by any means to cause rotation of a cylinder on an axle.
[0015] A roller-type stationary bicycle trainer includes a framework typically consisting
of two frame members flanking and adjoined to three cylindrical roller drums. Each
frame member consists of two parts: a front frame member that allows for various placements
of the front cylindrical roller drum relative to the two rear cylindrical roller drums
and a rear frame member which is adjoined to the two rear cylindrical roller drums.
In one instance, the frame members are pivitolly attached to each other to enable
the trainer to fold for storage. It is understood that this description is only indicative
of one type of trainer such as the type designed and produced by SportCrafters, Inc.
from Granger, Indiana known as the ZRO aluminum or ZRO PVC. Other configurations of
attaching cylindrical rollers with a framework intended to appropriately space the
rollers and allow for adjustment of the cylinders for use with various bicycles may
be employed.
[0016] A power transmission device, which can be a chain, belt or any similar device is
typically installed between the front cylinder and the middle cylinder, preferably,
an elastic belt. The power transmission device is typically carried in a groove formed
in the cap of the cylinder. In other applications the power transmission device is
installed between the front cylinder and the rear cylinder. In any case, the power
transmission belt is employed to cause the front cylinder to rotate in the same direction,
and at approximately the same rate, as either one of the rear cylinders.
[0017] When the progressive resistance device is used, the driven wheel of the bicycle is
placed on the two rear cylinders and the front wheel of the bicycle is placed on the
front cylinder. When the bicycle is powered by the rider, the rotation of the rear
wheel of the bicycle will cause the rear roller drums to rotate, and through the belt
drive, this will also cause the front roller drum to rotate in the same direction.
Therefore, the front wheel of the bicycle will also rotate in the same direction and
approximate speed as the rear wheel of the bicycle.
[0018] In an additional embodiment, a similar roller-type stationary bicycle trainer is
provided which is suitable for use with tricycles and handcycles - where the need
for the user to balance on the trainer is not required- includes a framework of two
rails adjoining two cylindrical roller drums one of the roller drums is a progressive
resistance device. It is further understood that this illustration is indicative of
the type of trainer designed and produced by SportCrafters Inc from Granger, Indiana
sold under the name Mini-roller. In this application, not requiring the skill of the
user to balance, the driven wheel of the bicycle is placed between the two roller
drums and aligned in such a way that the tire of the bicycle, tricycle, or handcycle
remains in contact with the roller drums during use. In a manner as is known, the
user pedals the bicycle, tricycle or handcycle so as to rotate the driven wheel which
in turn rotates the two cylinders supporting the driven wheel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a perspective view of a bicycle on a training roller assembly including
a progressive resistance device in the place of one of the cylinders;
[0020] FIG. 2 is a cutaway perspective view of the progressive resistance device shown in
FIG. 1;
[0021] FIG. 3 is an exploded view of the progressive resistance device of FIG. 2;
[0022] FIG. 4 is a sectional side view of the progressive resistance device of FIG. 2 and
showing three positions of the magnets;
[0023] FIG. 5 is a sectional side view of the progressive resistance device of FIG. 2 and
showing the torsional spring;
[0024] FIG. 6 is a sectional side view of the progressive resistance device of FIG. 2 and
showing the rotational stop
[0025] FIG. 7 is a graph showing power output per rotational speed for various progressive
resistance device;
[0026] FIG. 8 is a perspective view of a recumbent tricycle on a training roller assembly;
[0027] FIG. 9 is a perspective view of a hand-cycle on a training roller assembly;
[0028] FIG. 10 is a perspective view of an alternative embodiment of the progressive resistance
device having upright members; and
[0029] FIG. 11 is a perspective view of the progressive resistance device having upright
members of FIG. 10.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0030] In the embodiment depicted in FIG. 1, a bicycle 1 having a front wheel 2 and a rear
wheel 3 - powered conventionally by means of a crank, chain or other means of applying
human power to rear wheel 2 - is positionable on top of a training roller assembly
4. The roller assembly 4 includes three rotating cylinders, or drums - a front drum
5, a middle drum 6 and a rear drum 7 - carried by a frame 43. In one embodiment, the
frame 43 is formed having two front frame members 9, two rear frame members 10, two
hinges 11, and an elastic drive belt 12. One of the front frame members 9 is attached
by one of the hinges 11 to one of rear frame member 10, the group forming one side
of the frame 43. Another of the front frame members 9 is attached by another of the
hinges 11 to another of the rear frame member 10, the group forming another side of
the frame 43. The one and the other sides of the frame 43 are joined together by drums
5, 6, 7 which span therebetween. Drums 5, 6, 7 are laterally spaced from one another
along the frame 43. The middle drum 6 and the rear drum 7 are spaced apart such that
the rear wheel 3 contacts both drums and will not tend to roll over the top of the
middle drum while under power. This is typically accomplished by using a ratio of
the diameter of the rear wheel 3 divided by the centerline distance between the drums
roughly equivalent to 2.5. Therefore, as an example, a 27-inch diameter rear wheel
would work well with an 11 inch distance between the cylinders. If the distance between
the drums 6, 7 were smaller, there may be a tendency for the bicycle to roll over
the middle drum when the bicycle is powered by the rider. If the distance were wider,
there may be excessive pinching of the tire resulting in very high rolling resistance
and tire wear. As the drums 5, 6, 7 rotate, they contact the surrounding air, and
are cooled by forced convection. The drums 5, 6, 7 are preferably formed from a material
which readily dissipates heat, such as aluminum.
[0031] The distance between the front drum 5 and the middle drum 6 is adjusted by anchoring
the front drum 5 at any one of a plurality of adjusting holes 14 formed through both
of the front frame members 9 such that the front wheel 2 of the bicycle 1 is positioned
such that the axle of the front wheel 2 is offset above with the axle of the front
drum 5. An elastic drive belt 12 spans between the middle drum 6 and the front drum
5 such that the front drum 5 turns in the same direction as the middle and rear drums,
enabling the bicycle to be operated using the normal dynamics of steering and balance.
The elastic drive belt 12 is carried in a groove formed in the cap of the respective
drum.
[0032] This disclosure describes a typical bicycle roller assembly 4 as depicted by FIG.
1 whereby any one, two or three of the drums 5, 6, 7 house a resistance mechanism
42 as depicted in FIG. 2 and FIG. 3. For the purpose of illustration, the resistance
mechanism 42 in FIG. 2 is represented as the rear drum 7, but it can be positioned
in any of the three locations on roller assembly 4.
[0033] The resistance mechanism 42 is used in place of one or more of the drums 5, 6, 7
and is formed having a drum axle 23 which is a straight rod having threaded ends and
fasteners 13 suitable for securing the axle 23 to the roller frame 4. A cylinder 25,
made from electrically conductive material, forms the outer wall of the drum and defines
an internal chamber. An eccentric axle 20 encircles the axle 23 and includes a wall
having variable thickness. The eccentric axle 20 is rotatable around the axle 23.
A torsional spring 18 includes coils which encircle a portion of the eccentric axle
20, which spring provides an opposing force to the rotation of the eccentric axle
20, as described in greater detail below. One or more magnet bearings 19 encircle
the eccentric axle 20 and allow a magnet carrier 17 to rotate relative the eccentric
axle 20. The magnet carrier 17 includes a channel 46 for carrying one or more magnets
15. The magnet carrier 17 encircles the eccentric axle 20 with the magnet bearings
19 sandwiched between the eccentric axle 20 and the magnet carrier 17. The magnet
carrier 17 is preferably formed from a non-magnetic material. The eccentric axle 20
provides the centerline of rotation for the magnet bearings 19, said centerline being
offset from the centerline of the axle 23 by a predetermined amount. The end caps
21 cap the ends of the cylinder 25, with each end cap 21 having a drum bearing 22
installed into the end caps 21 which bearings allow the cylinder 25 to rotate about
the axle 23. The end caps 21 serve to locate the axle 23 in the center of the cylinder
25. A rotational stop 24 may be optionally employed to limit the rotation of the magnet
carrier 17 about the eccentric axle 20 to enable a limitation to the minimum or maximum
resistance as will be described below. The eccentric axle 20 includes one or more
axial grooves for accepting an end of the spring 18, thereby holding the end of spring
in fixed rotation with the eccentric axle 20. The magnet carrier 17 includes an aperture
for accepting another end of the spring 18, thereby the spring 18 is able to exert
a force between the eccentric axle 20 and the magnet carrier 17 when they are rotated
relative one another. In one embodiment, the magnet carrier 17 only partially encircles
magnet bearings 19, having an axial gap formed along the length of the magnet carrier.
A rib 47 is formed proximate the gap formed in the magnet carrier 17. The rib 47 contacts
the magnet bearings 19, and ensures contact therebetween; in one embodiment a rib
47 is formed on the magnet carrier 17 on each side of the gap. Similarly, a rib 48
is formed proximate the edge of a gap formed in the channel 46 for purposes of contacting
and holding firm a cylindrically-shaped magnet 15.
[0034] The axle 23 mounts the drum (each of drums 5, 6, 7 having a separate axle 23) to
the frame 43. The cylinder 25 is rotatable about the axle 23. As described in detail
below, rotation of the cylinder 25 causes the resistance mechanism 42 to resist rotation
of the cylinder. As shown in FIGS. 4 and 5, when the cylinder 25 is at rest (not rotating),
the torsional spring 18 is at its free state and the position of the magnets 15 is
held by said spring and/or the optional rotational stop 24 in Positions A or B, or
anywhere in this general area. Position A is the point where a maximum gap exists
between the magnets 15 and the cylinder 25, and Position C is the point where a minimum
gap exists between the magnets 15 and the cylinder 25, the gap at position B is approximately
50% of the differential gap as measured at Positions A and C.
[0035] It is important to note that in Positions A, B, and C the magnets 15 must be sufficiently
close to the wall of the cylinder 25 to allow a flux field of the magnets 15 to pass
through the wall of the conductive cylinder 25. The presence of the flux field through
the wall of the conductive cylinder 25 will cause a flow of electrons, otherwise known
as an eddy current, when the cylinder is in motion relative to the magnets 15. The
strength of the resulting magnetic field from the eddy current must be sufficient
to rotate the magnet carrier 17 about the eccentric axle 20 as a result of the force
exerted on the magnets by the eddy current. The torsional spring 18 applies a force
which resists rotation of the magnet carrier 17.
[0036] Therefore, when the conductive cylinder 25 is rotated in the direction of the arrows
shown in FIGS. 4-6, the magnet 15 will cause an eddy current to form in the cylinder
25 and will create a localized magnetic field which opposes the field of the magnets
15; a force is exerted on the magnets 15 in a direction tangential to the surface
of the conductive cylinder in the proximity of the magnets. Constrained by the eccentric
axle 20 and magnet bearings 19 the tangential direction of force translates to a circumferential
rotation of the magnet carrier 17 resulting in a decreased radial gap between the
magnets 15 and the conductive cylinder 25 as the rotational speed of the cylinder
25 increases.
[0037] As depicted in FIG. 6, the relative rotation of the magnet 15 and the magnet carrier
17 can be constrained by a rotational stop 24 wherein the stop 24 has an inwardly-extending
tab 44 which seats in the groove 45 of the eccentric axle 20. An outwardly extending
tab 49 is formed on the stop 24 which restricts rotation of the magnet carrier 17
by contacting the edges of the magnet carrier which form the axially-extending gap
formed in the magnet carrier 17 opposite the channel 46, thereby limiting the rotation
of the magnet carrier 17 relative the eccentric axle 20.
[0038] There is a direct relationship between the speed of rotation of the conductive cylinder
25 and the degree of rotation of the magnet carrier 17. Said relationship is most
easily understood by the principle that faster rotation between a conductive surface
relative a magnet produces higher electron flow and eddy current in the conductive
material, resulting in a stronger magnetic field produced by said eddy current. This
magnetic field exerts a force on the magnets 15 which in turn rotates the magnet carrier
17 about the eccentric axle 20, which rotation is resisted by the torsional spring
18. Therefore, there exists a higher amount of induced torque on the torsional spring
at higher cylinder rotational speeds and the spring will wind up until the torque
balances the resistive spring force. For a given rotational speed of the conductive
cylinder 25, a given force balance will exist between the magnet 14 and the torsional
spring 18 which will correspond to a given resistive force acting against the rotation
of the conductive cylinder at that given speed.
[0039] Further, there is a direct relationship between the degree of rotation of the magnet
carrier 17 and the power required to continue rotating the conductive cylinder 25.
Since it was already established that the degree of rotation is directly related to
torque, and that power is proportional to torque times angular velocity, then it can
be said that more power is required to rotate the cylinder a higher velocity.
[0040] A non-linear relationship between power and cylinder rotational velocity is established
by causing the magnets 15 to change their flux density through which the cylinder
must pass as the speed of the cylinder increases. In the first embodiment, this is
done by the magnets 15 rotating on a centerline that is eccentric to the axis of rotation
of the conductive cylinder 25. In this embodiment, the centerline of the axle 23 and
the centerline of rotation of the magnet 15 and the magnet carrier 17 are offset from
one another by the eccentric axle 20.
[0041] The resulting relationship between speed of rotation and power is demonstrated by
FIG. 7, which shows data points taken from product testing of the configuration represented
herein. The X-axis represents bicycle speed as measured in miles per hour (MPH), which
is directly proportional to cylinder rotational speed. The Y-axis represents power
produced by the rotation of the cylinder 25, as measured in Watts. The non-linear
increase in power with increasing speed is similar to actual conditions when riding
a bicycle outdoors, representing the combined effects of rolling resistance and aerodynamic
resistance.
[0042] In one embodiment, a rotational stop 24 is employed to limit the rotation of the
magnet carrier 17 relative the cylinder 25, as described above. Limiting rotation
in either direction of rotation will limit the range of magnet gap between the cylinder
and magnet which will have a corresponding effect on resistance to allow production
of a desired power/speed curve.
[0043] The resistance mechanism 42 described herein can be employed on other devices used
with human-powered three-wheeled vehicles such as tricycles and handcycles. As shown
in FIGS. 8 and 9, a smaller roller assembly using two rotating drums is employed to
allow the driven wheel to rotate under human power while the vehicle remains stationary.
One or both of the drums in this embodiment can house the resistance mechanism of
the present disclosure.
[0044] FIG. 8 shows an alternative embodiment where the rear wheel 27 of a recumbent tricycle
26 is mounted on top of a trainer 29 consisting of two cylindrical drums - a front
drum 30 and a rear drum 31 - and a frame having two rails 32 to which the drums are
affixed. In this embodiment, either the front drum 30, the rear drum 31, or both,
house the resistance mechanism 42 as heretofore described.
[0045] FIG. 9 shows an additional embodiment where the front wheel 34 of a handcycle 33
is mounted on top of a trainer 35 consisting of two cylindrical drums - a front drum
36 and a rear drum 37 - and a frame having two rails 38 to which the drums are affixed.
A pair upwardly-extending arms 39 are affixed to the frame, each extending upwardly
from one of rails 38 in such a way that each arm can be adjusted to contact one of
the outer rails of the handcycle's leg rests 40. The arms 39 are positioned in such
a way that they contact the leg rests forward of the axis of steering rotation so
that the handcycle remains stable as it is being pedaled on the trainer 35 by the
user. In this embodiment, either the front drum 36, the rear drum 37, or both, house
the resistance mechanism 42 as heretofore described. FIG. 10 shows an alternative
embodiment of the trainer 35 as used with a handcycle 33.
[0046] A further embodiment includes a cylindrical magnet (not shown) which is mounted in
close proximity to the outer surface of the conductive cylinder 25. In this embodiment,
the magnet does not rotate on a concentric centerline to the drum centerline, but
instead is initially oriented such that the equator of said magnet(s) is oriented
toward said conductive cylinder when the cylinder is at rest. As said cylinder rotates,
the cylindrical magnet(s) (not shown) will rotate on their axis against a torsional
spring 41 (not shown) such that one of the poles of the magnet will become oriented
in the direction of the conductive cylinder as the cylinder 25 increases in rotational
speed. Since the magnetic flux field near the equator of a cylindrical magnet is less
dense than the magnetic flux field at the magnet's poles, the effect of power versus
cylinder rotations speed is comparable to the embodiment with magnets positioned inside
the conductive cylinder.
[0047] It is understood that while certain aspects of the disclosed subject matter have
been shown and described, the disclosed subject matter is not limited thereto and
encompasses various other embodiments and aspects. No specific limitation with respect
to the specific embodiments disclosed herein is intended or should be inferred. Modifications
may be made to the disclosed subject matter as set forth in the following claims.
[0048] Further aspects and advantages of the present teaching will be appreciated from the
following numbered statements.
- 1. A cylindrical drum comprising:
an outer wall defining an internal chamber;
a magnetic resistance device is mounted is in said internal chamber, said magnetic
resistance device is rotatable about an axis which is offset from the axis of rotation
of said drum;
a magnet is mounted to said magnetic resistance device, said magnet is in sufficient
close proximity to said outer wall to allow the magnetic flux field of said magnet
to induce an eddy current in said outer wall.
- 2. The cylindrical drum of clause 1, and a roller-type bicycle trainer having a plurality
of rollers, said cylindrical drum is one of said plurality of rollers.
- 3. The cylindrical drum of clause 1, and an axle mounted along said axis of rotation
of said drum, and an eccentric axle forming a part of said magnetic resistance device
and circumscribing said axle.
- 4. The cylindrical drum of clause 3, and a magnet carrier forming part of said magnetic
resistance device and mounted around said eccentric axle, said magnet carrier carrying
said magnet.
- 5. The cylindrical drum of clause 4, and a stop limiting rotation between said magnet
carrier and said eccentric axle.
- 6. The cylindrical drum of clause 5, and said magnet carrier having a gap which contacts
said stop.
- 7. A cylindrical drum as in clause 1, wherein the cylinder wall is formed from an
electrically conductive material.
- 8. A cylindrical drum as in clause 1, wherein the structure to which said magnet is
mounted is made from a non-magnetic material.
- 9. A cylindrical drum as in clause 1, and a stop is mounted about said eccentric axle,
said eccentric axle having an axial groove, said stop having a tab which nests in
said groove, said stop having a second tab which is cabined within said gap of said
member thereby limiting the rotation of said member relative said eccentric axle.
- 10. A cylindrical drum as in clause 1, wherein when said cylindrical drum is rotated
in a first direction there is a linear relationship between power and resistance.
- 11. A cylindrical drum as in clause 10, wherein when said cylindrical drum is rotated
in a second direction there is a progressive relationship between power and resistance
1. A progressive resistance device comprising:
a cylinder having an outer wall defining an inner chamber;
an axle about which said cylinder is rotatable;
an eccentric axle surrounding said axle and is rotatable relative said axle;
a magnet carrier partially encircling said eccentric axle;
a magnet is carried by said magnet carrier;
a bearing is nested between said magnet carrier and said eccentric axle, said magnet
carrier is rotatable about said eccentric axle on an axis eccentric to the axis of
said axle, whereby the distance between said magnet and said outer wall is variable
as defined by the rotative position of said magnet carrier relative said outer wall.
2. The progressive resistance device of claim 1, and a roller-type bicycle trainer having
a plurality of rollers for supporting a bicycle, said progressive resistance device
is one of said plurality of rollers.
3. The progressive resistance device of claim 2, and a frame supporting said plurality
of rollers, said frame foldable for storage.
4. The progressive resistance device of any preceding claim, and a stop sandwiched between
said eccentric axle and said magnet carrier, said stop having an inwardly extending
tab holding said stop in fixed rotational alignment with said eccentric axle; said
stop having an outwardly extending tab limiting rotation of said magnet carrier relative
said eccentric axle.
5. The progressive resistance device of claim 4, and a groove formed in said eccentric
axle for accepting said inwardly extending tab.
6. The progressive resistance device of claim 4 or 5, and a gap formed in said magnet
carrier for accepting said outwardly extending tab.
7. The progressive resistance device of any preceding claim, and a roller-type bicycle
trainer having a first roller and a second roller supported on a frame, one of said
rollers is said progressive resistance device.
8. The progressive resistance device of claim 7, and a pair of upright arms extending
upwardly from said frame.