A novel type of bushing has helped Garmendale Engineering to reduce costs on a mineshaft-style railway ride for a new European theme park.
The Dodge Grip Tight Bushing system from Baldor Australia allows the drive wheels to be attached directly onto the shafts without the cost of machining keyways, providing a completely concentric grip.
The bushing's 360-degree fit and easy disassembly mechanism will also simplify routine maintenance of the ride, allowing trouble-free removal in seconds, as it eliminates the damage and corrosion that can often be caused by vibration-prone keyway style couplings with set screws.
Garmendale Engineering specialises in one-off engineering projects and has a considerable reputation in creating trains and rides for the leisure industry, with installations at almost all of the UK's well-known theme parks.
Garmendale Engineering’s recent project in this area is an underground railway system with mineshaft-style wooden wagons. Three trains of four wagons each have been built for the park.
Typically, Garmendale Engineering would couple this kind of wheel to the shaft by machining a keyway and securing with set screws.
The machine and assembly time required for each of the wheels would probably take one to two hours, adding in excess of 50 skilled labour man hours onto the total project costs.
However, Garmendale Engineering became aware of the new bushing system during a routine visit by one of its suppliers — Bearing Transmission & Pneumatics. The significant savings that could be made were immediately obvious.
The simple way the bushing system assembled was also viewed as useful, as it would simplify routine maintenance — allowing the non-specialist maintenance personnel that are often employed at theme parks to remove the wheels without trouble in order to change treads and get access to the bearings.
Keyway style mounting can often lead to fretting damage and corrosion, making wheels difficult to remove. Keyway systems can also cause vibration, as the set screws usually force the shaft to a slightly eccentric position — shortening the life of bearings.
To make the maintenance even easier, Garmendale Engineering made up a dedicated C-spanner tool to unscrew the size of Dodge Grip Tight Bushing used, eliminating the need to use a hammer and drift pin or an adjustable wrench.
Dodge Grip Tight Bushing is made up of two split sleeves and a locknut. The locknut draws the sleeves, which have opposing tapers together, closing the inner sleeve around the shaft until the grip is tight.
This provides a concentric 360-degree fit. As the nut is loosened, the spring makes the sleeves open slightly, allowing them to slide off.
For this application, each wagon is independently powered by a compact electric motor fitted with a differential gearbox to accommodate tightly twisting rail track, mounted on a swivelling bogey.
The wheels are connected through half shafts fitted with mounted bearings. In this instance, the drive system comes with American shafting, and the typical availability of Dodge bushing in a choice in either metric versions or to American or British shafting specifications, provided a simple solution.
A wide range of Garmendale's engineering disciplines have been involved in this project, including mechanical, electrical and electronic design, and metalwork and wood construction.
"The Grip Tight Bushing has saved us a couple of thousand pounds on this project, and provides a number of performance and maintenance advantages to the end user," says Garmendale Engineering's lead engineer on this project, Chris Hurt.
"The bushing system is ideal for many of the low-speed rotating shaft applications we design for leisure transportation, as well as many other forms of machinery and automation," says Chris Hurt.