Design Challenge

JON POPE

It would seem logical that final drive systems should convert from mechanical and hydraulic to electric. It’s a much simpler system that results in less downtime, and it has also been tested and proved to be tough in the mining and railroad industry for many decades. Although traction motors can be found on some of the largest capacity dump trucks in the world, hydraulic systems are still being used to power components of the truck. Even though some hydraulic systems are converting from hydraulic oil to water to reduce environmental impact, hydraulic rams are still complicated and labour-intensive to manufacture, install and maintain. So how do you make a diesel-electric earthmover without hydraulics? One answer: electricity generated to power the final drive must also lift, push and dump.

While looking for an electrified solution, I studied R. G. LeTourneau’s approach to using electric motors with very large rack and pinion gears to move the loader arms and buckets. It’s an interesting concept, especially for the time period (1950s-1960s), but it made the machines very top heavy. Plus, the loaders were very tall, which is not good for stability and transport.
Another option I considered was linear screw actuators. They could replace existing hydraulic rams as they mimic the rams’ movements and would take up about the same space. But linear screw actuators are not well balanced in performance. They have either fast movement while sacrificing lifting capacity, or have great lifting capacity but with slow movement.

Then I thought, what if you could make a ram that acts like a linear motor on a Maglev train? The ram could be a magnet, and a coil in the cylinder would push the magnetic ram in and out of the cylinder by changing the polarity in the coil. After doing a quick search I found out someone had already created such a motor. It’s called a tubular linear motor and it was designed and patented back in the mid 1980s by Michael Cowan. It has since been further developed and manufactured by Copley Motion Systems, and is used in manufacturing as an alternative to pneumatic actuators.

A scaled-up tubular linear motor could replace existing hydraulic rams on existing machines because they have the same proportions and similar mechanics (piston in a cylinder). So instead of waking up one day and all of a sudden tubular linear motors have completely replaced hydraulic rams, tubular linear motors could initially be retrofitted into existing designs, before working their way into new machine design. Plus, it’s a far simpler system to install and maintain than hydraulic rams.

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BIOGRAPHY

I would have to say just about 100% of my Matchbox and Tonka toys were trucks and construction equipment. Basically I have been fascinated with heavy equipment for as long as I can remember.  I received a B.S. for Industrial design at University of Bridgeport and I have been an industrial designer for 15 years. The last 12 of those years have been specializing in heavy equipment. I have worked on projects for several different OEM’s while I was employed at Teague and later as a design consultant. I’ve had the pleasure to work on projects from a 400 ton dump truck to a powered wheelchair. I also have a bad habit of designing conceptual construction in my spare time.