(4/20-4/24) Electrical Reflection

Jeff wanted us to answer the following questions in regards to our introduction to electrical:

1. How do you know what you know you know?

2. How do you know what you know that you don't know?

These questions were referencing to shorts, voltage drops, and opens in a circuit. I know these things because we have seen them demonstrated in class.

A short, for starters, is a pathway that provides less resistance than the intended route for current to flow through. This results in the circuit not providing the intended load with power. In many cases a short will cause a larger amount of current to flow through the circuit causing the fuse within the circuit to overload and blow. An extremely useful technique we learned to help isolate where the short in the circuit is located was "replace the fuse that blows with a fuse that glows". In other words, replace the fuse with a light bulb. This will allow you to isolate where in the circuit the short is located. If the circuit is still shorting out the bulb will illuminate.

Voltage drops are areas of the circuit that are placing excessive resistance to the circuit and thus causing the voltage in the circuit to drop. They may be caused by loose connections, corrosion of the cables or wires, improperly sized wires or cables, and improperly crimped connections. Voltage drops may be found on the power side of the circuit as well as the ground side of the circuit. Once completing the test on both sides, both measurements will be added together to find the total voltage drop in the circuit. A general rule of thumb to use is if more than half a volt (.5) is found in the circuit, then the circuit has a problem that will need to be found and fixed.

Finally, we have opens withing a circuit. Opens are fairly easy to explain. A circuit needs to have a pathway to the ground of the circuit for the current to flow freely. If an area of the circuit is damaged, say a wire has been cut, now the circuit has been "opened". The current cannot complete it's intended course and the system does not operate.

This is just the tip of the iceberg for electrical. But at least we now have a firm foundation in the basic knowledge of a circuit and I know it will greatly assist me in my career in the future.

In regards to the second question, I suppose I have a hard time seeing how to use this knowledge in the real world. I know that once I get more experience in real world scenarios, it will make more sense. It's hard for me to visualize these circuit boards as actual trucks versus a board laying on the table. Most of my uncertainty comes from there I suppose. 

BTC Hours: 12
Total Hours: 192.5

4/13-4/17: Light Bulb!

The most profound thing I learned last week had to be in regards to a circuit board we used that simulated the running lights on a truck. Everything worked as it was supposed to on the board, however, we were asked an interesting question. Why did the turn signal light alternate on/off opposite as the brake/turn signal light when the turn signal was activated?

As you can see, power goes to both bulbs when the lights are activated. However, when the turn signal is activated through the board, a relay is activated and sends power down through the right hand side of the circuit which leads to the RH Front park/turn light and sends positive flow to the other side of RH right marker light and thus taking away its closed circuit. When the relay disconnects the current flows back through RH right marker light and has a complete circuit by making RH front park/turn light essentially a ground. 

O2 vs "Air"

Terminology is critical. Especially when using an acetylene torch. Oxygen should be referred to as an oxidizer or just O2. When you call it "air", it can be misinterpreted and used for tools that should never have pure oxygen plumbed into them. Such as a die grinder. The following image was from the VMMC that the Lincoln rep was passing around. The gentlemen who used this tool miraculously lived. Just because there is an attachment that looks slightly like an air compressor hook up does not mean it is just compressed air. In this case a custom attachment was made to plumb his die grinder into pure O2. The result was a bright flash of blue and temperatures that melted the tool. Always know what you are using and make sure you know the terminology.

 

4/7-4/10 Introduction To Electronics

We are getting an introduction to electronics this last week. A lot of information to process and hold onto. For starters, we learned about Ohm's Law, which states, "that the current through a conductor between two points is directly proportional to the potential difference across the two points. Introducing the constant of proportionality, the resistance, one arrives at the usual mathematical equation that describes this relationship." 

A very useful visual picture to help in the application of this law has been the following pie chart 

There are three basic circuits: Series, Parallel, and Series-Parallel 

Series is, as the name suggests, all the loads in the circuit are in series. 

Parallel circuits have there loads branching off of the main line and are placed along side of each other. 

And as you can imagine, series-parallel is a combination of both. 

We had an introduction course to the basics of electronics which had a practice test at the course. It did not give me a final grade so I took video. 

Hours: 10
Hours Total: 168.5

3/9-3/20 Catching Up

I missed last weeks blog post, so you are in luck! A double feature is now showing here!

The first week which would be 9th-13th was a pretty straight forward week. At my internship I did more annual maintenance on lawn equipment. At school I was able to fabricate a new engine hook for one of the engines at school. It was actually a lot of fun and gave me an excuse to use the acetylene torch. I cut an approximate 11" of  3/8x4" steel, constituting a "0" bit for my torch. I set the torch to 15-20 O2 and 3-5 for my acetylene. After cutting and drilling my steel I gave it a sleek flat black paint job to give it that clean cut look.

The old one was looking kind of... sketchy. 

Flat black does wonders. 

Looks clean cut now. 

 The second week I learned about vacuum and pressure testing on the fire engine pumps at the shop. By shutting all of the discharge valves and running the primer pump with no water we were able to create a vacuum in the pump, we then observed the gauge to note any significant loss in vacuum pressure. We then pressurized the system with shop air while covering the discharge ports with latex gloves to see if any air was escaping. Once we completed these tests we concluded that the pump packing needed to be replaced and set about taking the old packing out. To take out the old packing we took the plungers out and pressurized the system by flowing water from a secondary tender (T63) to the engine 70's intake/suction port. As the pressure built to about 170psi in the 2 1/2" hose, it forced the old pump packing to be blasted out.

Pretty cool system they use. 

E70 Is a classy Ol' Girl. 

Wood paneling

Detroit 92 still kickin'

NWFR Shop Hours for March: 40.25

BTC Shop Hours for 3/1-Present: 31

3/2-3/6 Weather Packs

Last week I learned how to properly install weather packs for electronics. Sadly, I did not take any pictures but here are a few web images of what I used

After stripping the wire I installed the male/female ends to the bare wires for proper connection. There is a crimp tool specifically designed for weather packs to use that will make your life much easier. However, they can be installed without it but it just becomes more difficult.

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Rigging, MIG Welding (2/23-2/27)

This week at school we had two assignments to complete by weeks end. The first, was to properly and safely rig some miscellaneous items around the shop. A few engines, a concrete block, a press, and a fork lift to top it all off. We had to estimate the weight of each item before we rigged it then show how we would safely rig it for lifting by finding the center of gravity and using the proper rigging straps or chains. A spreader bar came in handy with the engines. 

We were also to complete the first initial passes on a steel "x" for a lack of a better term. We used 1/4"x4" steel with 1/4"x2", tacked them together in an "x" pattern, then proceeded to weld them together. For my first layer of welding I used the MIG welder, I hope that this next week to start in on stick welding. A very useful tool I have been using is a YouTube channel called Welding Tips and Tricks. He also has a website with weekly uploads on everything welding.  

Forklift weighed more than we estimated. By a lot. 

Was right on the money for the Duetz engine.

Second time in my life using a MIG welder, not to shabby I think. 

BTC Shop time for this week: 12 hours

Shop time at NWFR: 16 hours (69.25 total hours for FEB)