Apr 17

silver-jetpack-martin aviation company-himmelsturner       

This Jetpack consists of a built-in gasoline engine driving twin ducted fans which produce sufficient thrust to lift the aircraft and a pilot in vertical takeoff and landing, enabling sustained flight.

01-martin-aircraft-jetpack-commercial jetpack manufacturers-personal flying  machine jetpack- jetpack machines

Jetpack Development:

Since the beginning of time man has dreamed of personal flight – the ability to fly as free as birds and escape gravity’s pull.

From the 1920s this dream has been refined in film, books and television, with the jetpack portrayed as the ultimate tool for the freedom of flight.

In the 1950s the first serious attempts at building a jetpack produced the Bell Rocket Belt. But the Bell Rocket Belt has some limitations. It is powered by an expensive and hazardous fuel, needs a light weight pilot, is incredibly hard to fly, and, after 50 years of development can only fly for 30 seconds. It is not the practical jetpack the world has been waiting for.

In 1981, as a New Zealand student, started his quest to a build a jetpack that overcame the limitations of the Rocket Belt. With enthusiasm and commitment Glenn has been able to capture the support of a large network of experts who shared his dream.

01-jetpack-30 minutes of flight time-gasoline engine-two ducted fans

The rest is history. On 29 July 2008, the world’s first practical jetpack, was revealed to the world and became an international media sensation.

Jetpack Technology:

01-carbon fibre composite jetpack-VTOL-vertical take off and landing aircraft- fan jet technology-martin-aircraft-jetpack-commercial jetpack manufacturers-personal flying  machine jetpack

The Jetpack is constructed from carbon fiber composite, has a dry weight of 250 lbs (excluding safety equipment) and measures 5 ft high x 5.5 ft wide x 5 ft long. It’s driven by a 2.0 L V4 2 stroke engine rated at 200 hp (150 kw), can reach 8000 ft (estimated) and each of the two 1.7 ft wide rotors is made from carbon / Kevlar composite.

There is always risk associated with flying so the Aircraft has been careful to equip the pack with redundant systems that will take over in the event that the main system goes down. If a crash-landing is required, a pilot-operated toggle will rapidly fire a small amount of propellant deploying a ballistic parachute (similar to a car airbag) which will allow the pilot and jetpack to descend together. It also has an impact-absorbing carriage, patented fan jet technology and 1000 hours engine TBO (Time Between Overhaul). Small vertical take-off and landing aircraft (VTOL) are not subject to the same limitations as other helicopters and fixed wing aircrafts but Aircraft have built it to comply with ultra light regulations and therefore suggest it as at least as safe to operate, and claim it is the safest of all jetpacks yet built.

01-jetpack-a personal aircraft

The Jetpack achieves with 30 minutes of flight time and is fueled by regular premium gasoline.

Safety Development:

Roll cage:

01-steel roll cage

A roll cage is a specially constructed frame built in (or sometimes around) the cab of a vehicle to protect its occupants from being injured in an accident, particularly in the event of a roll-over. A roll bar is a single bar behind the driver that provides moderate roll-over protection. Due to the lack of a protective top, some modern convertibles utilize a strong windscreen frame acting as a roll bar. Also, a roll hoop may be placed behind both headrests, which is essentially a roll bar spanning the width of a passenger’s shoulders.

Factor Of Safety:

The Jetpack has a number of mechanical things moving fast….a drive train, Fan jets. All these are designed with far higher "factors of safety" (FOS) than is normal for an aircraft. This was done because of the newness of the design and to cover for unforeseen factors. For instance the Fan blades have a FOS of 5, at the hub and over 10 at the blade.

Parachute:

01-parachute-in aircrafts-jetpacks

Production versions of the Jetpack are equipped with a Ballistic Parachute system from Ballistic Recovery Systems. This enables the pilot to be saved from a catastrophic failure down to a reasonably low altitude. Ballistic parachutes can open at very low altitudes, particularly if the aircraft has some forward speed. For this reason the "flight profiles" will be calculated to have the lowest risk possible.

01-jetpack-parachute compartment-flying controls-twin turbo jets

Application:

  • Emergency response,
  • Defense and recreation, with numerous applications in each sector.

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Apr 05

01-factor of safety-chair design

It is common practice to size the machine elements, so that the maximum design stress is below the UTS (Ultimate Tensile Stress) or yield stress by an appropriate factor – the Factor of Safety, based on UTS(Ultimate Tensile Stress) or Yield Strength. The factor of safety
also known as Safety Factor, is used to provide a design margin over the theoretical design capacity to allow for uncertainty in the design process. Factor of safety is recommended by the conditions over which the designer has no control, that is to account for the uncertainties involved in the design process.

01-Gearbox-Casing-FOS-Study-Results-Factor of Safety

The uncertainties include (but not limited to),

  • Uncertainty regarding exact properties of material. For example, the yield strength can only be specified in between a range.
  • Uncertainty regarding the size. The designer has to use the test data to design parts which are much smaller or larger. It is well known that a small part has more strength than a large one of same material.
  • Uncertainty due to machining processes.
  • Uncertainty due to the effect of assembly operations like riveting, welding etc.
  • Uncertainty due to effect of time on strength. Operating environments may cause a gradual deterioration of strength, leading to premature and unpredictable failure of the part.
  • Uncertainty in the nature and type of load applied.
  • Assumptions and approximations made in the nature of surface conditions of the machine element.

Selection of factor of safety

 

safeunsafe-FActor of safety-simulation xpress study result-displacement distribution-safety in design

The selection of the appropriate factor of safety to be used in design of components is essentially a compromise between the associated additional cost and weight and the benefit of increased safety or/and reliability. Generally an increased factor of safety results from a heavier component or a component made from a more exotic material or/and improved component design. An appropriate factor of safety is chosen based on several considerations. Prime considerations are the accuracy of load and wear estimates, the consequences of failure, and the cost of over engineering the component to achieve that factor of safety. For example, components whose failure could result in substantial financial loss, serious injury or death usually use a safety factor of four or higher (often ten). Non-critical components generally have a safety factor of two. Extreme care must be used in dealing with vibration loads, more so if the vibrations approach resonant frequencies. The vibrations resulting from seismic disturbances are often important and need to be considered in detail. Where higher factors might appear desirable, a more thorough analysis of the problem should be undertaken before deciding on their use.

  • 1.25 – 1.5
    - Material properties known in detail. Operating conditions known in detail. Loads and resultant stresses and strains known with with high degree of certainty. Material test certificates, proof loading, regular inspection and maintenance. Low weight is important to design.
  • 1.5 – 2
    - Known materials with certification under reasonably constant
    environmental conditions, subjected to loads and stresses that can be determined using qualified design procedures. Proof tests, regular inspection and maintenance required.
  • 2 – 2.5
    - Materials obtained for reputable suppliers to relevant standards
    operated in normal environments and subjected to loads and stresses that can be determined using checked calculations.
  • 2.5 – 3
    - For less tried materials or for brittle materials under average
    conditions of environment, load and stress.
  • 3 – 4
    - For untried materials used under average conditions of environment, load and stress. Should also be used with better-known materials that are to be used in uncertain environments or subject to uncertain stresses.

Usually the factor of safety is kept larger, except in aerospace and automobile industries. Here safety factors are kept low (about 1.15 – 1.25) because the costs associated with structural weight are so high. This low safety factor is why aerospace parts and materials are subject to more stringent testing and quality control. Now computers are being used to provide more accurate simulation of stresses that occur in components, particularly in the case of high value products where safety and saving weight is essential.

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