Engineering Today for Tomorrow

Bicycle evolution indicative of overall technology evolution

2009-04-26T11:03:00.002-05:00

The ever increasing pace of technology evolution is simply amazing. Examples of this are everywhere from communications(pony express to the pda in 150 years); engineering computation(sliderule to desktop workstations in 30 years); to audio(vinyl records to the ipod in 80 years). Step changes at the start of the 2oth century would typically take 2 to 3 human generations. Now 2 to 3 step changes are occurring within 1 human generation.

An example I'm very familiar with is the technology evolution of "upright" bicycles. The same basic derailleur bicycle had not changed from the earlier 1900's to the late 1970's. That vintage bike had brazed thin-walled steel tubing. Aluminum components. Two chain rings. Five rear cogs. Downtube mounted derailleur friction shifters. Leather saddle on aluminum seat post. Cleated cycling shoes with leather toe straps. Wheels were thin walled aluminum with typically 32 to 36 14 to 16 gage stainless steel straight or double butted spokes. Tires were either clinchers with tubes or the lighter weight glue-on tubulars. Jerseys and shorts were wool with a soft leather seat chamios. Helmets, if they were worn, were leather strap nets. Racing weights were 20 - 21 lbs. The speedometer was a wristwatch and road markers.

Today's model is a monoque carbon fiber frame and carbon fiber fork. Handlebars, seatpost, cranks, deraulliers, saddle cage and wheel rims all have carbon fiber options. Triple chainrings are common. Ten spocket cogs are common. Handbar mounted index shifting with integrated brakelevers are standard. Step-in toe cleats are used. Wheels can be monocoque 3 trispokes to 12 -15 bladed spokes. Even full disked wheels are relatively common. All components can be had in aerodynamic shapes. Spandex skinsuits with synethic chamios are common. Handlebar cycling computers with gps, heartrate monitors and training programs with downloadable databases are available. Aerodynamic, plastic shelled helmets with built in head phones are used. Electric hand and foot heaters are available.

The racing bike has evolved so quickly that the governing racing associations have had to implement weight and dimensional standards to slow the progress. For example the UCI (Union Cycliste Internationale) weight standard has been set at 15 lbs even though technology can provide weights a few pounds less than this.

In the early 1970's a time under an hour would win most 25 mile time trials including the US nationals. Today it takes closer to 48 minutes. Some of this improvement is due to better conditioning and more participation but the bulk of the improvement has been the equipment. Compare this to the 10,000 meter world track running record improving from 27:39 in 1965 to the current 26:17 in the same time period.

If the "upright" bicycle is compared to the broader field of human powered vehicles the analogy becomes even more amazing as shown by the hour records in the graphic.

CAE Tool Effectivity and Opportunities

2009-03-27T19:29:00.005-05:00

CAE design tool development has made continual and sometimes amazing progress in the last 3 to 4 decades. 3D, interconnectivity and multiphysics are readily available. However, as an end user, manager of users and even developer of such tools I see several keys challenges or perhaps opportunities in the field:

- Expense: in many cases the expense of the tool(s) keeps a large engineering segment from using them. Some of the systems can be priced upwards of $50k and higher with correspondingly high hardware and maintenance costs. Certainly options exist for access to the tools such as consultants and in some cases pay as you go use but these options are many times cumbersome.

- Hardware capability lag: Even with 64bit processing, dual core, hugh RAM.....some CAE models take too much time to develop, execute and results process to really be effective in the design process. They at best may offer a final analytical validation but are ineffective for routine iterations for optimizing a complex design. I see some movement towards internet hosted systems and/or clustered systems that may help crack this problem coupled with the continual computer and memory improvements. Other options include supercomputer time sharing but that can be expensive.

- Casual users: Even though many software developers tout the user friendliness of their wares in most cases a casual user is always relearning how to use the tool. This reduces their effectivity. The larger and well funded organizations can perhaps afford the "full time expert" but it's not as common as in years past.

- Software sophification exceeding many users experience: In many instances the tool has too much capability for the users. Doing a 3D CFD simulation without understanding the assumptions behind the algorithms can lead to garbage in garbage out without anyone necessarily being the wiser until perhaps late in the process.

- Keeping with the prior generation process box. The example I repeatedly cite are the teams that spend hours and hours developing 3D CAD models and then revert back to creating 2D drawings for communicating to other team members like suppliers. I see no technical reason why this is necessary. The 3D model with perhaps referenced specs should contain all necessary information.

- Forgetting Occam's Razor or probably better known as the KISS principle. Many models end up being way too complex for the need. The software has so many features and capabilites that the user is too easily pulled into trying to model virtually everything and many times ends up with a very cumbersome model. This is more of a management issue. It needs to be continually reinforced that modeling should be taken in progressively more complext levels and never beyond the need of the design. If it doesn't work for the simple hand calculation it likely won't work for the 100,000 node FE model that might take days or even weeks to develop.

- Accuracy understanding. Many users lose sight of the bigger picture with respect to precision. An FE stress analysis will never be any more accurate than the certainity of the loads, boundary conditions and/or material properties.

- Virtually all the analytical CAE tools available today performing analyses on an existing concept. This certainly is a value added capability but the next leap forward will be evolving them to direct design tools. In other words, the tool will provide direct design content with assist from the analytical tools semi and or fully automatically. This will likely bring expert systems and intelligent design to bear in the process. Today's process is to layout a concept generally in a CAD system. The design is then ported to the various analytical simulations for stress, dynamics, CFD, thermal and so on. Each simulation provides feedback to the team for decisions on needed changes. The next generation tools will take the set of design needs and criteria and the tools will provide the design or at minimum various options.

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vibration/shock isolators provide double benefit

2009-03-26T16:35:00.004-05:00

Vibration and shock isolators have been used forever in countless applications. A recent application I have been associated with highlights a double benefit that can be gained by their use. A diesel engine propulsion system on a railroad locomotive has isolators that are used to mount the engine to the locomotive frame. The engine is very dynamic and has relatively high vibration levels from the normal sources like driveshaft unbalance, piston firing and so. The isolators reduce the amount of this vibration that gets transmitted to the frame. The benefits are lower noise, reduced dynamic loads on the frame and adjacent equipment, increased crew comfort, etc.

The second benefit is for the engine itself. Locomotives experience high shock loads from coupling into rail cars and other locomotives in building up the consists and from pulling and braking. The coupler shock loads are somewhat attenuated by the coupler draft gear which is typically a laminated rubber bumper, however, some shock load still occurs at the frame and makes its way to the engine mounts. For this case the shock load is isolated from the engine by the isolators.

A generally inexpensive device serving two important functions: reducing engine loads passing into the frame and reducing the frame transmitted shock loads passing back to the engine.

Occam's Razor

2007-10-27T20:31:00.000-05:00

William of Ockham (c. 1285–1349) a 14th-century English Franciscan friar is credited with the principle that states that one should not make more assumptions than the minimum needed. This is more commonly known as Occam’s Razor or the principle of parsimony which originates from the Latin phase “lex parsimoniae” or “entia non sunt multiplicanda praeter necessitatem” which translates to “entities should not be multiplied beyond necessity.” This is a principle perhaps better known as KISS or "keep it simple, stupid."

Some examples of this principle in engineering:

As the part count increases for a design, the reliability generally decreases. For example, a bracket that uses bolts to attach it to another structure will have lower reliability if 4 smaller bolts are used rather than 2 larger bolts if each bolt has the same safety factor and hence the same probability of failure.

A design load with a 20% uncertainty used in a sophisicated computer simulation with high precision results will have no better certainty than 20%. Select the simulation method based on the level of certainty of the model parameter certainties.

Sensors have failure modes. Will a sensor used to monitor a design function improve the overall reliability when considering the sensing reliabilities?

Regression models should always be checked against first principles and limiting conditions. If they fail this review then the model and/or data is likely wrong. The simpliest regression model should always be used and in many cases will be linear.

Test data should always be used in the context of the test and measurement methods. It is very difficult to simulate the real world useage in the laboratory.

A simple test is better than no test as long as the context of the test and quality of the data are understood.

The first calculation ever made for any concept and idea should be by pencil on a single sheet of paper. Anything more is a waste of time. If the concept doesn't pass the first principle test it doesn't have a chance of passing a sophisicated computer simulation.