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  1. M

    I Making a heat shield for my car's exhaust

    To berkeman: I'm adding an aux. fuel tank and lines to an existing vehicle. I also have a race car (with turbo) that is fabbed. So this issues comes up more than once. :-) To Baluncore: Yes, thanks. My thought was to make one side of the heat shield more like a black body and the other side a...
  2. M

    I Making a heat shield for my car's exhaust

    I'm considering radiant energy.
  3. M

    I Making a heat shield for my car's exhaust

    Hello, I'm just wanting to make sure I remember this correctly. I have a hot exhaust pipe I want to shield from fuel lines. So I have a shield (stainless) that is going 1/2 way around the exhaust, with an air gap of about 1". I want to sand blast the side facing the heat and polish the side...
  4. M

    I Calculating the windspeed based on a brick being launched off of a closed dumpster lid

    I think it's safe to assume the brick did not slide down much once the lid started to rise up. Even just a little opening would cause the lid to flip nearly instantly. So the starting height above ground would be about 5'. So what I did was use a cannon ball trajectory and if I select a launch...
  5. M

    I Calculating the windspeed based on a brick being launched off of a closed dumpster lid

    Hello, We had a wind storm. We have a dumpster with a lid. On that lid we put a heavy brick to keep the lid closed during wind storms. It's worked great for years. But we had a very strong wind storm and it launched that brick quite a distance. I'm trying to figure out the wind speed that would...
  6. M

    Calculating Temperature Change for Heat Exchanger

    I'm sorry, I'm unable to provide a sketch. If you just imagine 2 plates parallel to each other, about 1/8" apart forming a channel for the air to go thru. (ends blocked so it creates a long thin tunnel for the air to pass.) The blocks will be kept at approx. 32F (or lower). Based on the speed...
  7. M

    News NYTimes: [Scientific] Fraud Scandals Sap China’s Dream...

    My point is from the perspective of the Chinese Govt, not the HK residents. They found the golden goose and all they did was changed who owned the goose not how the goose did it's work.
  8. M

    If maths was a food, which food would it be?

    Oh come on! If Math was food there is only one real answer: Chocolate! Nothing so bitter could taste so sweet with just a little imagination.
  9. M

    News NYTimes: [Scientific] Fraud Scandals Sap China’s Dream...

    The main reason China is anything at all is Hong Kong. Look at the history of the Chinese economy and exports. There is Pre-HK and Post HK. When the Chinese took over HK from the British at the end of the 99 year lease, they saw how well it worked and said, "if it ain't broke, don't fix it."...
  10. M

    Do people become less self-conscious as they get old?

    This is easy to illustrate why. There are lots of websites selling a chart. It's called "the number of weeks of your life." You print it out and you find our current age and mark all the weeks before that off. As you get older you realize the number of weeks you have left is getting smaller and...
  11. M

    Negative pressure in house after winterizing

    My opinion: Everything in the house creates heat. People, stove, water boiler, oven, TV, etc. That has to go someplace. So it's found a way out. Chimney, holes for the lights, wall outlets, door jams etc. That creates a current of air that is creating an negative (with relation to outside)...
  12. M

    Calculating Temperature Change for Heat Exchanger

    Hello, After the last post I completely changed the system. I now have a new system. Based on the feedback from last time I increased the time in contact with the block significantly. And I have made it a two stage unit. Here are the parameters for the first stage. An Aluminum block...
  13. M

    Need help with wiring motors in series and in parallel

    Yes, the the gearbox. The mount for the motor/pinion is not in the correct location. The pinion to first gear is binding, has zero backlash. It was so bad it wore down the center hub of 2nd gear (the pinion was pushing on first gear so hard it transferred the force to 2nd gear. First gear has a...
  14. M

    Need help with wiring motors in series and in parallel

    No bad smell. I'm going to put a fan in there to exhaust the hot air anyway. also see if I canfind a heat sink to fit them. they are popular with the RC folks so it should be possible. thanks
  15. M

    Need help with wiring motors in series and in parallel

    Yes, I got a msg from the seller. They believe one of the gears is binding on the axle. I will pull the "gearbox" apart and check to see that the gear is spinning freely. I just hope it didn't gall the shaft from our test runs. Thanks. (I put "gearbox" in quotes because I can't with a straight...
  16. M

    Need help with wiring motors in series and in parallel

    The seller says to "break them in" by running free wheel for 15 minutes. Which we did. With the car off the ground, and low power to the motors (motors in series) they both start to spin in the same direction, then w/in a few seconds the one will slow down to stop, and reverse for just a 1/4 to...
  17. M

    Need help with wiring motors in series and in parallel

    I will make a little video showing it in action, however I have cut and spliced the wires so many times I'm out of wire so I have to rewire it and I'm going to use banana plugs and posts so I can just plug and unplug as needed. But I have to order some so it'll take me a few days to get back...
  18. M

    Need help with wiring motors in series and in parallel

    What is especially weird is the one motor will start to run for a few seconds and then reverse direction for a second and then stop completely. I have tried to load them with the motors installed in the car and my son riding it, but it just spins the one wheel like heck and the other does...
  19. M

    Need help with wiring motors in series and in parallel

    I think they are these with a different label on them: https://traxxas.com/products/parts/motors/titan775 I know they are called 775 motors.
  20. M

    Need help with wiring motors in series and in parallel

    Hello, I'm working on my kids ride on cars. He has two of them. On the first it was 6V and came with one motor on one wheel. I updated it to 2 motors, one on each wheel and 12Volts. I put in a DPDT switch so he could select high and low. On high the motors are run in parallel and on low they...
  21. M

    Rate of heat transfer/temperature change

    If I knew the formula to use, I would not be posting here.
  22. M

    Rate of heat transfer/temperature change

    Thank you Insightful. Can you give me the formula that you used? So I can make modifications to the system? Thank you!
  23. M

    Rate of heat transfer/temperature change

    Hello, I have another crazy project I'm working on and I need to know if this is viable before I spend a bunch of time and money. Here is the situation: I have a small block of Al. 1/4" x 1/4" x 1" long. Thru the length I drill a 1/16" hole. The surface will be whatever a standard drill bit...
  24. M

    Calculating temp change releasing a compressed gas

    Or is the problem my expectations? Do we only get a temp drop of it involves a phase change? Compressing "air" will not get a phase change. :-(
  25. M

    Calculating temp change releasing a compressed gas

    Sorry boss, but I'm not getting it. I have 2 transformations. P1V1/T1=P2V2/T2 I can't solve this because I don't know V1. I only know the pressure I'm staring with 1ATM, Temp I'm starting with 100F, or 310K So T2=P2V2T1/P1V1 But at this point I don't know T2 because I don't know V1. Then...
  26. M

    Calculating temp change releasing a compressed gas

    Pressure is 4500psi. Not sure if you consider that "ridiculously high" or not.
  27. M

    Calculating temp change releasing a compressed gas

    Hello, I understand when you release a compressed gas generally it comes out cooler than atmosphere. But here are my questions: When you fill the container, the gas warms up as the pressure builds. Generally it takes a long time to compress and I believe the temperature of the gas when it's...
  28. M

    How many BTU/hr needed to cool 500 CFM of air 100F degrees?

    And does it matter if you are going from 200F to 100F or 500F to 400F? ie, is it temperature dependent? Thanks
  29. M

    Got asked, "Why does there 'need' to be a UFT"

    Generally the "need" comes from the desire to answer the question: Is the universe created or did it just happen. If a UFT can be found, their is a reasonable next question: Why? Pretty much everyone wants to have a firm belief system. There are atheist that are sure of their position just like...
  30. M

    Experiment to measure the thermal conductivity of a material

    Thanks to all. At least I know i can give a reasonably accurate no. if we get to that point. Thanks you to all!
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