Boat Ride Guide Wheel

Most theme park boat rides employ a series of lateral wheels on each side of the boat. These wheels perform the following functions:

• Provide lateral guidance in the flume. For this function, the wheels should be relatively soft and have a large stroke to minimize the impact loads to the passengers as the boar bumps around the serpentine trough. However, they should not absorb too much energy, as that would slow the boat too much.
• Center the boat in the load/unload areas and other control points. For this function, relatively stiff wheels are desired to minimize the tolerances on the gap between the station platform and the boat.
• Absorb the loads generated when a backup occurs and boats collide. When this happens, the boats tend to “jack knife” and large lateral loads are imparted when a moving boat impacts a string of stationary boats. For this case, the wheels need to absorb very high loads without failing.

In all cases, the wheel must be designed for long life scuffing against steel and/or abrasive concrete surfaces and be impervious to degradation from the treated flume water and ultraviolet radiation.

TWT was asked to investigate a new wheel design for a boat ride when conventional wheels were not providing satisfactory ride quality, durability and impact resistance. This required a significant upgrade to TWT’s proprietary wheel analysis tools. Our analysis and performance prediction tools were designed around high-speed roller coaster load wheels, which are thermally limited or load limited and have relatively small deflections.

For the boat guide wheels, temperature and running loads are not design drivers, but these wheels see very high impact loads and require deflections on the order of 10% of the diameter. The wheel had to be designed to tolerate large deflections without creating excessive strain in the urethane wheel material, while providing the desired spring rate characteristics, and the analysis tools had to be modified accordingly.

TWT’s design, shown below, is dubbed the X5 because the cross section of the tread is shaped like the number 5. This wheel features large radial deflections with a relatively low spring rate, coupled with a very high load capacity when it is bottomed out. As a result, the wheel offers excellent ride quality as the boat bumps its way around curves in the flume. However, in the event of a back-up or a collision with a brake, the wheel compresses and successfully transfers the high load to the supporting structure. In addition, the X5 incorporates features to make it more compatible with treated water than conventional wheels.

After completing the analysis and design, TWT manufactured a batch of X5 wheels in various hardness levels for testing. TWT ran tests to verify that the load-deflection curve matched analytical predictions, and the Client evaluated the ride quality and impact resistance of the various test wheels on the ride. The Client then placed production orders for the wheels that best met their needs. Harder wheels are used for the leading and trailing locations, as they take the brunt of heavy impacts. Softer wheels of the same design are used in intermediate positions to improve ride quality in corners and to prevent pinch points.