Zipline Subject Matter Expert

Zipline Accidents

In 2016, I co-authored "Zipline Injuries on the Rise" with Rex Bush, Esq., published on and in Utah Trial Journal (2017). The article said that zipline injuries were increasing, and a Granite Insurance–North Carolina presentation validated the article at the 2020 virtual Association for Challenge Course Technology (ACCT) Conference and Expo. They told us that six to seven patrons settle lawsuits per 100,000 zipliners, and over half were from zipline braking failures. These numbers are incredibly high compared to other amusement park rides. For instance, roller coaster injuries are one for every 700,000 riders.

As a zipline expert witness, I know accidents are increasing; my investigations led to invent a 3-lb. RST in 2017. We have five new RST patents after our 25-lb. PCMR controlled braking trolleys. We also know most zipline platforms are small—shorter than ten feet—so a 60-foot spring array is unrealistic. Our zipline spring systems are service-proven and fail-safe-safe with a 3:1 FoS; telescoping springs add safety and reassurance. If your zipline has two brakes, adding a third brake—creating a 3:1 FoS—reduces accidents, and you become compliant with all zipline standards.

Not all ziplines have 3:1 FoS for braking; most ziplines use two brakes (2:1) because the standards are misleading. For instance, ASTM F2959 says a zipline brake must be fail-safe (2:1), and the ACCT only requires a primary and secondary brake (2:1). Zipline accidents increase because of this confusion; most zipline builders fail to realize that three brakes, not two, follow the standard. Reliance on inadequate two-brake systems has led to skyrocketing accidents.

To mitigate injuries, our company Momentum Engineering, a DBA of ZipSafe, LLC, only sells service–proven, fail-safe-safe zipline systems with at least a 3:1 FoS. Our three brake ziplines keep all participants safe because being fail-safe-safe would have stopped this multi-million dollar settlement. We maximize your safety with every product we design and go beyond the minimum safety standards. We continue to develop more fail-safe-safe zipline braking systems, and our five US patents, three in the last three years, stop accidents.

If your system has a 2:1 FoS, we hope you follow the braking standards and add another brake to slow your zipliners and decrease my zipline expert witness engagements (ten investigations annually). Mention this narrative when you place your order on or call us directly to receive a 15% discount on products and services.   

Controlled Zip Line Trolleys

Safe Ziplining

 The Richardson Safety Trolley (RST) history began in 2001 when we—AA Machining & Welding, Inc.—designed and manufactured a 60-mph RST for the giant zipline we built in 2002 at Park City (Utah) Mountain Resort (PCMR); the 3,500-foot-long zipline broke records with a 600-foot drop between platforms. Since then, over fifty ski resort ziplines have utilized RSTs; our RSTs have an unblemished safety record with zero braking accidents. We continually strive to improve our controlled-braking trolleys to function correctly for our customers. If a design fails to meet our client's expectations, we replace their RST with an improved version at no charge.

AA Machining & Welding, Inc. was the parent company of Momentum Engineering in 2015, and in 2020 to move forward with testing zipline trolleys with controlled-braking—our seventh-generation RST—is a 2-lb. (mini) trolley that controls the speed of all zipliners in one setting. Assessing the RST-23 (mini) began soon after the IAAPA (International Association of Amusement Park Attractions) Expo.

Last summer we assessed our RST-22 and it performed flawlessly; the braking trolley safely stopped test-weights of 35—315 pounds on a 10-degree slope; we found that pin/slope setting #8 was ideal (for the rider weights) and the RST still had five braking locations to move closer to the wheel—less braking force. So, we shipped two RST-22 to an east African zipline. We soon found their three-degree slope was no match for our trolley's fastest setting, #3—the lowest brake force—our RST stopped one hundred feet short of the platform. We learned that the RST needed one more pin/slope setting next to the wheel. So, we expanded the lever arm and slot to show numbers #2—#14. The RST-22 were returned for a full refund, and we sent them the RST-23FS.                                                

 The Richardson Safety Trolley rests on a zipline cable (see blue arrow) reducing the water factor. The vertical lever arms with circular handles identify the #5  pin setting. Notice that the participant's carabiner (see purple arrow) connects below the handles acting as a lever arm in one of the pin/slope settings to vary the amount of brake force.

 Every zipline slope varies as adventurers zipline over scenic terrain, so our test RSTs have over a dozen lever arm adjustments (pin/slope settings) to stop zipliners. To adjust the lever arm, remove the safety pin (see Image 2; orange arrow) and use the handles to lift the two lever arms and then horizontally adjust to the desired setting; then lower the lever arm and replace the safety pin. The fastest speed setting is close to the wheel, #2, and #14 is the slowest and closest to the RST brake (see green arrow).

 ​The advantage of RSTs over uncontrolled trolleys (two wheels) that traverse ziplines at ninety-five percent gravity (9.0 m/s). Our RSTs have slope adjusting speed control—via pin/slope settings—to equalize zipliners to control the speed for all weights in one setting for a determined slope. We compared the Petzl® two-wheel trolley to the RST in this video. The zipline slope is 10-degrees. The video the Petzl uncontrolled trolley arriving a 22-MPH, and our RST-22 arrives at 2-MPH. Zipline owners and designers can establish a pin setting that stops an 80-lb. rider safely—on the same slope—as a 250-lb. rider. Each zipliner applies controlled braking using friction and their weight (mass) to stop them safely. Notice in this 2019 RST video using the same pin/slope setting to stop all weights and established a benchmark to reduce RST rollback. Patron retrievals occur daily with two-wheeled uncontrolled trolleys.

In 2019, our telescoping spring patents solved that problem, and their different compression rates (pounds per inch) soften all stops. Our springs install in minutes, and meet the standards when properly tested and they can eliminate braking related lawsuits.


Industry Standards

Ziplines standards require a minimum 3:1 engineering factor of safety (FoS) or safety factor (SF). The FoS or SF guides the zipline engineer or designer to address the intended loads or level of safety required. For example, if a device breaks one pound above its maximum load (1,000 lbs.), and the standards require a 5:1 FoS, the load must not break or fail with a 5,000 lb. to be compliant. The minimum zipline standards have required a 3:1 FoS for decades, this confuses most operators who think the standards require two brakes. The confusion starts when the standards say there is a 3:1 FoS minimum for ziplines, but they say we require a primary and secondary or a fail-safe zipline brake, meaning 2:1. This discrepancy adds to the extremely high zipline accident rates, because ziplines need three brakes, to remove braking related injuries from being number one cause.

In 2002, Park City Mountain Resort (PCMR) set the zipline standard for trolley braking with a 3:1 engineering factor of safety (FoS) for zipline braking. We built their RST-02, which incorporated two brakes, and had an emergency brake—a sixty-foot-long compression spring array—at the end. Twenty-one years later, the PCMR zipline is still accident-free because RST systems are fail-safe-safe (3:1).

Most owners and builders think gravity is braking reliability. That is false! Gravity braking is never safe, and the accident rates prove it. Ziplines are not like steel bridges that expansion joints. The variables that are hard to control are zipline cables expand and contract, and the changing weights of zipliners; zipline builders must consider all the ziplining variables: the participant's mass (m), trolley friction, and outside temperature. These all affect arrival speed. Gravity (g) accelerates all zipliners downward at -9.8 meters per second (m/s); wind resistance is always present, but zipliners stop because of their upward travel. Due to physics, the heavier a zipliner is, the faster they travel upward, not downward; gravity is a constant for all falling objects.

Steel bridges, unlike ziplines, have expansion joints that allow steel to expand and contract without buckling due to outside temperature changes; zipline cables cannot have expansion joints—the cable would fall—so ziplines expand and contract, which increases or reduces the bottom curvature (the belly of the cable). Ziplines change all day, so controlling a zipliner's speed is difficult, especially when using free-wheeling trolleys. Heavy participants are in the greatest danger on ziplines, and adding colder temperatures has been disastrous. My zipline expert witness thrives because most ziplines utilize two-wheeled trolleys. Another two-wheeled trolley problem is retrievals; when temperatures go up, the small/lightweight zipliners stop too soon, slowing the progress and costing the zipline owner valuable time.



Zipline Expert and Seven-time U.S. Patent holder

Michael Troy Richardson

Mr. Richardson is a Aerial Adventure Subject Matter Expert with decades of experience, education, and knowledge. For seven years he has helped improve industry standards and best practices. His physics, engineering, and technical writing education helps attorneys, zipline owners, and zipliners. He serves on both sides of civil matters. His reputation and credibility make him a formidable opponent who leads his clients to successful resolutions.

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  • Rex Curtis Bush

    "I utilized Mr. Richardson’s services on a zipline death case and on a trampoline injury case. I was extremely happy with his services in both cases!"

    Attorney, Bush Law Firm 
  • Matt S.

    “Momentum Engineering, LLC provided our Zipline with over 200 Barrel/Telescoping springs this year. They sell Emergency Brakes! Other companies selling zipline brake systems cannot claim they sell true Emergency Brakes”

  • Bill Bernam

    “After you have had a chance to review the video, please kindly call me to discuss. ... I need to know exactly what I’m dealing with.  And I have several questions for which your input would be greatly appreciated.”

Daily Safety Inspections reduce Liabilities

22+ Years of Experience

Q: Why choose Momentum Engineering?

A: Decades of experience safely stopping zipliners is the #1 reason.

#2. State-of-the-art engineering
and precision design that can reduce zipline arrival platforms.

#3. Telescoping E-Brake Spring Arrays offer unparalleled reliability and performance.

With these advanced braking systems, zipliners enjoy smoother and more controlled stops, ensuring safer aerial adventures.

  1. Unrivaled Expertise: Backed
    by decades of engineering excellence, our team brings unmatched expert knowledge and experience to the zipline industry.
  2. Cutting-Edge Innovation: We are dedicated to staying ahead of the curve by developing innovative patents that refine our products to meet or exceed our customer’s goals and the evolving zipline industry safety standards (e.g., ACCT, ASTM F2959, ERCA, and PRCA).
  3. Customer-Centric Approach: Zipline
    success is our priority, so we will work closely with your team and
    help them understand our springs, trolley pin settings, and the momentum (p=mv)
    factor. Our Team is here to fill your unique needs and tailor these solutions
    to fit your operation perfectly.
  4. Proven Results: Our track
    safety record speaks for itself.
  5. Zipline standards are changing because
    we spoke up, and the standards listened. Owners who add our products see
    improved braking-related safety immediately.
  6. Peace of Mind: Zipline braking choices increase your confidence, so let us help you provide the BEST
    . Now, you can provide safer experiences and lower insurance premiums with us on your team.
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Zipline Safety is No Accident

Q: What else does Momentum Engineering do?

A: We’re certified inspectors and trainers. As Risk Management Specialists, we can help you.

Our elevations, audits, and staff training(s) reduce your
risks of having the most common lawsuits in the industry. Why? Because accident
investigations have found our team for a decade, and most are plaintiffs.


Our signature product is the auto-braking (Fail-Safe) trolleys that have improved zipliner safety since 2002 when Park City Mountain Resort (Utah Ski Resort) asked us to develop its World Record Breaking 3,500-foot zipline, with 600 feet of drop, reaching speeds of 60-MPH, and still
stopping zipliners safely for over 22 years

We also sell Telescoping/Barrel Spring Arrays that are simple to install and are easier to inspect. In 30 minutes—after installing our springs—you can stop 6-MPH 200-lb zipliners safely! Our products won’t take HOURS to install! OR DAYS, like some popular braking products requiring
annual shipping and recertification
. (Our products last up to four years.)

Strengthen Your Case

Troy is a Product Design Engineer, Master Machinist, Board-Certified Welder, Physics Expert with decades of industry knowledge, education, and experience. Owner/operator/trainer in multiple Gyms, Adventure Parks/Theme Parks. He is a spring designer and manufacturer with several US Patents for Aerial Adventure Safety Devices. As of 2019, his continuing education accumulated more than 30 semester hours of Advanced Physics.

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About Troy

My mother tells me how early my passion for inventing began; her stories help me remember my childhood memories of disassembling old toys to create new ones. I excelled at math and art in grade school, which ties into my high school welding class leading to a good career. My welding class had math, and the metal construction with beautiful weld beads holding the parts together was art. I began assembling the welded parts to create innovative designs for myself and others. After high school, I worked at a foundry, welding and polishing bronze statues sculpted by Stanley Johnson.

My parents raised me to work hard, and I grew up in what I would call a typical alcoholic home. My parents’ drinking seemed normal, so I, too, began drinking in my early teens. Not long after, I was in legal trouble for drinking, forcing me to attend Alcoholics Anonymous (A.A). The A.A. meetings are a gift from God, and I took my last drink at age 24. A few years later, I became a first-generation college student earning a two-year degree in Machine Tooling with a welding emphasis. 

In 1995, my welding ability and machining degree led to my starting A.A. Machining & Welding, Inc.; the company was a job shop that could manufacture, machine, or weld almost anything. We frequently catered to inventors who found my company could help them with their ideas. We designed and built dozens of prototypes. Here, I learned about intellectual property laws and rules that could protect me as an inventor.

In 2001, Park City Mountain Resort (PCMR), a Utah ski resort, hired my company to design a 60-MPH autobraking zipline trolley for the 2002 Winter Olympics; I was in the engineering program at Southern Utah University learning AutoCAD, so my designs converted prototype assemblies into 60-MPH trolleys. The trolley applied a friction brake to slow zipliners down the entire zipline. A year later, PCMR awarded my machine and welding shop the contract to build: two giant zipline towers, thirty Richardson Safety Trolleys (60-MPH auto-braking trolley), and two emergency brake systems consisting of a 60-foot long compression spring arrays with weights per cable. Afterward, my zipline career faded for about a decade as I focused on raising my family and three autistic grandchildren.

In 2009, I built a commercial zipline in my hometown. Shortly after, a plaintiff’s attorney contacted me as an expert regarding a fatal zipline accident in Reno, Nevada. I soon realized my time away from the fast-growing zipline industry had left participants vulnerable to zipline braking accidents, and PCMR’s zipline trolleys are still: immune from zipline braking accidents (which account for over half of all injuries). For twenty-one years, RSTs have been accident-free.

So in 2011, I returned to college to earn a design engineering degree; three years later, I earned a Bachelor of Science in Engineering Technology. I wanted to be a Patent Attorney and thought my degree and three more years of law school would get me there. I knew several patent attorneys, but one of them advised me that my expert witness career was more lucrative than law school. He was right.

In 2015, I sold my company and started Momentum Engineering; the design company grew from the increasing number of zipline accidents, which catapulted my career as an expert witness. My zipline patents, experience, and degrees added credibility to my work as an expert witness. The best part is more time to develop zipline safety products. In my role as a zipline expert, I try to reduce zipline accidents, which reduces my expert witnessing, and preventing injuries is a better use of my time.

In 2021, I partnered with Mike Holder to develop stackable spring array for primary and secondary emergency brake system. He is an ACCT Preferred Vendor Member and the owner of American Adventure Park Systems in Historic Banning Mills, Georgia  Mike and I are seasoned U.S. Patent holders and developed the invention to reduce zipline braking injuries. That same year, I took the United States patent bar exam, Category B, after earning over thirty-two physics semester hours needed with my undergraduate degree. My first attempt failed, so I plan to retake the exam someday. Also, that year I was accepted into Technical Writing & Digital Rhetoric, a graduate program at Utah Tech University. This degree will further advance my direction to earn a Ph.D., which will no longer be associated with being a pretty heavy drinker.  On 02/04/23, I celebrate 33 years of sobriety.    

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