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Help with a Basic design

  1. Nov 5, 2009 #1
    Hello Everyone,

    Okay so I am new to the engineering stuff and am starting off with some basic ideas. I wont get into all of them but I had a question.

    I want to build a push button flag pole. I am talking something maybe 2 feet tall that would raise and lower one of those small scall flags. It is novelty but I am trying to learn some basic stuff before I start going bigger.

    I know I could build a one way pulley system but I dont know how to make the thing stop at a certain point and stuff.

    Thanks for the help.

    Feel free to ask me about anything relating to old chevy motors!!!

    Donnie
     
  2. jcsd
  3. Nov 5, 2009 #2
    There are a number of ways to do this. A basic approach would be to use some SR flip-flops to control the power to a motor which drives the pulley system. Stops on the rope would trigger buttons to turn off the motor when the flag reaches the desired location.

    Driving the flag in one direction is fairly easy because it only involves one set and one reset (on and off). Getting it to go the other way is a little more complicated because you need to reverse the power to the motor. You should get familiar with the flipflop and h-bridge before attempting that.

    Another way to get the flag going both directions would be to use a motor that runs only one way but a drive train that is reversible. The electronics would be similar as far as tracking where the flag needs to go, but you might not need the h-bridge driver.

    Check out the wikipedia page on flip-flops and on h-bridge drivers. The h-bridge is useful because it has two inputs that give you 3 states, forward, backward and idle (actually there are 4 states, but the 4th one is usually 'self-destruct', so you generally want to avoid that one). The flip-flops are useful because they will latch on or off after a momentary button press. The first button press can turn on the output, and the second button press would come from a limit switch installed on the rope which turns off the output. During the time between the two button presses the motor runs on it's own with no buttons being held.

    Once you understand how they work you have to analyze the logic to see how to get the states that you want.

    Ok, what might cause a '71 350 with a stock cam, headers, RPM Performer intake and Edelbrock 1407 carb to tend to bog down badly when pulling away from a stop, and occasionally back-fire through the carb, but stop bogging down right after backfiring? Carb get's all sooty, it's quite a mess. I have the jet/rods/springs kit, but lack the knowledge to choose the right configuration.
     
  4. Nov 5, 2009 #3

    The answer is simple but the solution will require some additional information. The problem is a fuel and air mixture. The fact that you said after your backfire it continues to run makes me think that it is a fuel problem specifically.

    My recommendation would be to check all your vacuum lines first. This will ensure that you are not losing any of your airflow. The next thing is to open the hood and manually rev the engine using the throttle cable attatchment. If it bogs down with no load then it is definately a jetting issue.

    On the front of your carb there are two adjustment screws. Try and adjust those to the left, once the engine starts to idle badly, turn them a quarter turn to the right. Try running it like that. If that doesnt work go to the right using the same technique with a quarter turn back left.

    It also wouldnt hurt to shoot some carb cleaner in there and loosen every thing up. There are several online tutorials to rejet a carb. Let me know if that fixes the problem and I can see if there is anything further. I have a similar carb on my 72' Nova and had some issues with it and ended up switching to a holley.
     
  5. Nov 7, 2009 #4
    An electric automobile antenna mechanism sounds ideal for the little flagpole.
    If you are willing to hold the switch, then you are set right out of the junk yard.
    If it's to be one-touch button, then you need limit detection and some logic.
    If you use logic gates to control the 12v motor, you'll need IRLZ44 or similar logic FETs (or similar) so the logic circuit can switch the power and snubbing diodes on the motor to damp kickback EMF. This needs to be an H-bridge configuration so you can reverse the motor.
     
  6. Nov 9, 2009 #5
    2 pulleys (1 big, i small), a loop of string, 2 microswitches , a push button, and a motor, and source, reverser relay.
    the micro-switches do the "logic" in an analog means. the "trip" is when ever the connection of the loop comes back to the same place push button bypasses the tripped microswitch.

    E carbs seem to always have this problem. It is an "off idle" lean (most likely) or rich condition. The metering rods and springs can be changed to tune it out. The moment that you "crack the throttle" (vs idle) your engine needs: additional fuel. more timing. make sure that the vacumn advance works (suck on tube to dist, idle speed should increase) and is hooked to ported vacumn (no vac at idle, crack throttle, instant vac) and not direct (constant) vacumn.
    I have NEVER put one of those carbs on anything and not had the problem. Those are a variation of the old AFB, with all the better engineering removed...lol
    stock HP old mopars used those a lot.

    heck just come on over, bring some beer and I'll look at it for nothing

    dr
     
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