Patent Application
20190127012
Many motorcycles are modified from a two wheel motorcycle to a three wheel motorized cycle. The motorized three wheel motorized cycle has two back wheels attached to a drive train and a single front wheel used to steer the motorcycle.
While at a two wheel motorcycle utilizes both turning of the front wheel and leaning the motorcycle into the turn, a three wheel motorcycle utilized little to no leaning because the two back wheels prevent such movement. As such, a distance from where the front wheel touches the ground to where the steering axis intersects the ground (commonly referred to as trail) can be reduced to increase the responsiveness of the motorcycle to the steering of the front wheel.
A front fork for a motorcycle includes a bottom portion configured to engage an axle of a front wheel, the bottom portion having a center line at an angle relative to vertical. An angled middle portion extends from a top of the bottom portion at an angle relative to vertical that is larger than the bottom portion center line angle relative to vertical. A steering head attachment extends from a top of the angled middle portion.
A steering assembly for a front wheel of a motorcycle includes a front fork, a steering head secured to the angled upper portion, wherein the steering head has an axis of rotation that is substantially parallel with the center line of the bottom portion, and a suspension secured to the steering head and a main body of the motorcycle. The front fork includes a bottom portion configured to engage an axle of a front wheel, the bottom portion having a center line at an angle relative to vertical, and an angled upper portion extending from the bottom portion wherein the front fork reduces a trail distance relative to a substantially straight front fork.
A method of improving steering response of a three wheel motorcycle includes reducing trail distance of the motorcycle with a front steering assembly. Reducing trail distance includes displacing an axis of a front fork of the motorcycle from a steering axis of a steering head of the motorcycle. The axis of the front fork is displaced forward of the steering axis using the fork having a lower portion and an upper portion, and an angled portion coupling the upper and lower portions. The axis of the steering assembly is substantially parallel to the steering axis.
A three wheel motorcycle of the present disclosure includes a dual rear wheel set and a front wheel, an engine and a drive train, and a steering assembly for the front wheel of the motorcycle. The steering assembly includes a front fork having a bottom portion configured to engage an axle of a front wheel, the bottom portion having a center line at an angle relative to vertical, and an angled upper portion extending from the bottom portion wherein the front fork reduces a trail distance relative to a substantially straight front fork. A steering head is secured to the angled upper portion, wherein the steering head has an axis of rotation that is substantially parallel with the center line of the bottom portion, a suspension is secured to the steering head and a main body of the motorcycle
A schematic diagram of a typical front wheel and steering mechanism for a two-wheel motorcycle, such as a Honda Goldwing, is illustrated at 10 in FIG.1. A typical front wheel steering mechanism 10 includes a wheel 12 supported by an axle 14 that is attached to a front fork 16. A steering head 18 is non-rotatably secured to the front fork 16 and carries a handlebar configured to be gripped and manipulated by a driver to steer the motorcycle by rotating the steering head about an axis of rotation 19. A suspension 20, such as a compression spring attaches the front fork 16 to a frame of the motorcycle (where the frame is not illustrated).
The front fork 16 carries caliper 22 of a front brake where the caliper 22 is configured to frictionally engage a disk. In some motorcycles, the front fork 16 also carries a front fender 24 that is positioned about the front wheel 12 where the front fender 22 substantially prevents road spray from splattering on the driver. As such, the front fork 16 not only supports the wheel 12 but also provides a support surface for numerous other parts of the motorcycle, including but not limited to the caliper 22, the fender 24 and a front head light (not shown).
As mentioned above, the trail distance D1 or the distance between where the front wheel 12 touches the ground and where the steering axis 19 intersects the ground is designed to be used in combination with leaning the motorcycle when turning or steering. However, when a two-wheel motorcycle is converted to a three-wheel motorcycle with two back wheels, the ability to utilize lean to steer the motorcycle is substantially eliminated. To compensate for the loss of lean, the front fork is modified to reduce the trail, and thereby increase the responsiveness of the steering.
A front fork of the present disclosure is illustrated at 100 in
The bottom portion 104 has a centerline 105 that is substantially parallel to the axis of rotation 19. Having the centerline 105 substantially parallel to the axis of rotation 19 allows the fender 24 and the caliper 22 to be mounted at substantially at the same angle relative to the earth as illustrated in
Further because the axis of rotation 19 is at substantially the same angle and substantially in the same location, the same suspension 20 can be utilized to mount the front fork 100 to the main body. As such, the front fork 100 of the present disclosure can be mounted to the main body without any substantial modifications.
Steering head attachment 106 extends at the angle of the steering head of a motorcycle, so that the steering head attachment 106 and the axis 105 of the fork lower portion 102 are substantially parallel. In this configuration, the steering axis 19 of the motorcycle, the steering head attachment 106, and the steering head 18 are aligned. The fork lower portion 102 axis 105 is substantially parallel to and in front of the steering head attachment axis, relative to the front of the motorcycle. The fork portions comprise in one embodiment a single solid fork. It should be understood that the fork may be assembled from multiple pieces without departing from the scope of the disclosure.
The angled portion 104 of fork 100 extends the fork axis 105 forward from the steering axis 19 of the steering assembly of the motorcycle 400. Accordingly, the trail distance D2 for the fork 100 on motorcycle 400 is reduced from a traditional fork 16. Specifically, the angled portion of the fork 100 moves the fork axis 105 forward from the traditional steering axis 19, but does so in a way that the steering orientation of the motorcycle 400 is maintained. A turning operation of the handlebars of the motorcycle 400 with fork 100 is more sensitive than a turning operation of the handlebars of a motorcycle using a traditional fork. At the same time, the steering operation is consistent with traditional steering because the axis 105 of the fork 100 and the steering axis 19 are substantially parallel.
The rake of a motorcycle is the angle of the steering axis to a vertical line perpendicular to the ground, often drawn through the axle of the wheel. In general, as rake increases so does trail. However, the rake of a motorcycle using the fork embodiments of the present disclosure does not change, since the steering axis and the fork axis are substantially parallel. Fork embodiments of the present disclosure reduce trail distance, without reducing rake. Reduction in trail distance improves steering and steering response, traditionally with a corresponding loss in stability. However, reducing trail distance for a three wheel motorcycle does not have the same potential negative effect of reducing trail in a two-wheel motorcycle, since three road contact points inherently increases stability. With a motorcycle having three points of road contact, a reduced trail distance improves steering without decreasing stability. The embodiments of the present disclosure provide a fork with increased steering ability due to the reduced trail distance.
An increased rake typically increases steering effort and trail distance while also increasing stability. Fork embodiments of the present disclosure do not increase rake, while at the same time decreasing trail distance. With a three wheel motorcycle, stability is much less of an issue that with a two wheel motorcycle, so the increased wheel base and reduced trail distance due to the offset of the fork axis 105 of lower portion 102 of the fork 100 from the steering head attachment 106 and the steering axis 19 do not negatively affect stability of a three wheel motorcycle. The fork embodiments of the present disclosure also aid in turning, as they do not increase rake and they do decrease trail distance.
In one embodiment, motorcycle 700 is a three wheel motorcycle, comprising a dual rear wheel set 704 and a front wheel 702, and an engine and a drive train. A steering assembly 706 for the front wheel 702 of the motorcycle 700 comprises a front fork 100. Front fork 100 comprises a bottom portion 102 configured to engage an axle of the front wheel 702, the bottom portion 102 having a center line 105 at an angle relative to vertical. An angled upper portion 104 extends from the bottom portion 102 wherein the front fork 100 reduces a trail distance relative to a substantially straight front fork. A steering head 18 is secured to a steering head portion (106, not shown in
While a fork has been described that includes two straight portions and an angle portion coupling the two straight portions, it should be understood that other configurations may be employed without departing from the scope of the disclosure.
Although the present disclosure has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the disclosure.
The present application is based on and claims the benefit of U.S. provisional patent application Ser. No. 62/579,602, filed Oct. 31, 2017, the content of which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62579602 | Oct 2017 | US |
