Archive for May, 2012


When you put pen to paper, there is a connection made between your mind and the words you are writing. That connection gets your mind working on the getting across that thought you put to paper. I do mean the physical connection of a physical pen and actual paper.

When you sketch your ideas and thoughts on a design, it gets your creative function running because you have to think about how you want to describe it. Believe me, once you start, you may have several ideas, several iterations, probably partials that you can continue with later.

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It is hard for some to get up and share your thoughts by sketching in front of someone or a crowd of engineers and mechanical designers. They will make comments about your sketching ability, so get over it now, and move on. Sharing your thoughts through sketching will get others on board with your idea and motivate them, and yourself, to do more iteration through sketching.  image

 

 

 

 

Sketching your idea to yourself will help you develop and effectively explain your design idea to a fellow engineer, mentor, or manager.

 

 

 

 

 

 

White write-on boards are great for sharing and capturing ideation.

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…sketching thoughts and ideas on a white board works just as well, but remember to take a quick photo for your records. These notes could be used for patent work, so it is always a good idea to get your initials and date in the photo, or on the sketch page.

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There are instances in mechanical design that you know what you want, but a sketch will make it clearer to the others what you see in your design. Once the understanding starts, there will all kinds of input as to what might be better…that will be up to you.

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Just let your thoughts flow from your mind through the pen. You will surprise yourself on how the design will flow and morph. And, as you go through page after page, your thought pattern will become clearer. Perhaps you have not considered something that is critical, or important to the design overall function. As you continue to let the ideas build on each other you will find that after spending time going over the various iterations, that it will be much easier to get those ideas into 3D on your MCAD system.

Always have a note book with you, to capture your thoughts. You may see a mechanical design that intrigues you, and reviewing and getting it sketched may spark some thought towards a design solution.

I have sketched ideas my whole life, perhaps to help me remember, or for further thought. As anyone who has written a paper knows, it is good to get it written, then let it sit for awhile. You will be thinking about what you wrote, and how well you are getting your subject across to the reader. When you pick up the paper and begin reading, you will find that there will be additions and corrections that will be obvious, making your subject come alive to the reader. You will experience the same with sketching your ideas. Your mind goes over thoughts sketched on the paper, and begins the thought process all over.

Have you had the opportunity to use strain gages in your design verification process? Early in my career I had the opportunity to work in a design analysis and testing group. I had been in the road grader product design engineering group, working on a new grader, specifically a hydraulic powered front wheel drive assembly. The design analysis group needed someone to help in the analysis, and then verification using strain gages. Now, I had several courses in college relating to and application of strain gages, but this was going to be the first real world application for me.

ScreenHunter_05 May. 05 10.38Galion Grader analysis

Our department engineering manager, Lazlo Keves, gave me an opportunity to practice and learn the protocols for mounting, wiring, connecting, reading the gages, and gathering data. I had worked on the design of a new crane, and the outriggers were ready to be gaged and loaded.

Galion 150 P-CScreenHunter_08 May. 05 16.57

I went through my calculation sheets, and sketches and determined where I wanted to place the gages. These were single element gages due to the fact where I was going to place them the strain was in line with the outrigger body and easy to determine orientation.

ScreenHunter_09 May. 05 17.01

I had performed numerous design calculations on a variety of parts and welded structures, but this was the first time that I had my calculations checked with real world measured strain conditions. My partner positioned the crane, lowered the outriggers, and prepared to lift the designated load. He then lifted the load off the ground, while I monitored the gages. The indicated strain was within about 5% of what I had calculated, in the gage location on the outriggers.

Lazlo took me aside and reviewed my calculation, the strain gage installation, and the results. He told me that considering all the variations that could effect the hand calculations, 5% was considered acceptable. Most design margins are somewhat larger, and the main idea behind any mechanical design and load analysis was to account for the major variances that have the most effect.

The strain that the gage indicates is true strain on the surface of the object. Then, the engineering stress value is calculated using the modulus of elasticity, with the equation; clip_image002, which solved for stress: clip_image002[4]. We then use the stress value in our design analysis efforts to meet our design margins and project goals. And, there are variations of the section, and assumed load application. All of these variables need to be considered during the design process.

As a mechanical engineer, if you get the chance to be involved with the strain gage testing of your design, take it. You will develop an appreciation for all the variables in the design process, and be better at identifying what is most applicable to your design analysis. It is very satisfying, predicting how a structure will respond to a given load, and then see that effort verified with real world loads and the associated strains.