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Getting 108-3 N6635M back into the air

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BRUCE
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Joined: 2 years ago
Posts: 128
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Socket scare...

If you are like me, (I wish you luck if you are...) you would assume that a Craftsman socket with a model number stamped on it, if even from a long time ago, would yield the same socket today when you order the socket with the same model number. Well you (and I) would be wrong.

I ordered a socket for my spark plugs because the Craftsman 13/16" 47527 socket that I borrowed from Sammy's previous owner worked fine and Amazon told me that it was available and in stock. It came today. Well, here's what I got...

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You might notice a bit of a difference. Yes the new socket is shorter. Sheesh...will it even work? Secondly look inside.

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The new one (bottom) has a step making the upper clearance smaller. The original one has the same opening size all the way to the top. One more thing...

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In this shot it is clear that the body of the socket is thinner than the original one. This is OK in one sense...it will get into tight cavities where other sockets might not. But my friend's old socket had no trouble reaching into the cylinder to loosen the plug. So this is telling me that Craftsman is making the socket thinner to save material.

The good news is, yes, the socket did fit over the plugs and will work to extract them. So now I can return my friend's socket. 

Do you think he'd notice if I gave him my new one?


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BRUCE
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Joined: 2 years ago
Posts: 128
Topic starter  

Taking care of loose ends...literally

I decided that before I start working on Sammy's engine I should take care of several things I started but have not finished. I don't want to go forward with lots of things that need to be completed. I have found that when you start working on one thing three or four other things immediately open up and need attention too.

You may recall that a while back I delved into the electrical issues with Sammy's left wing. No position light...no landing light...stall horn doesn't work...the fuel sender is telling lies...

So I got out my electrical tools

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and pulled off the strips of faring on the bottom wing root and pulled back the head liner at the left side of the cabin and found...lots of disconnected wires.

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So I cut and tinned several 2 foot long of lengths of new wire and, using my meter, figured out which wires coming from the cabin needed to connect to which wires in the wing. I used a stiff piece of wire with a hook bent on the end to fish a path from the cabin to the wing root inspection hole.

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I then pulled in each new piece of wire and soldered it to the appropriate wire at the wing root and the cabin making the connection for...

The left nav light...

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The landing light...

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And the stall horn makes a loud beep...

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And the fuel sender.

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I used solder and heat shrink in lieu of the crappy spade connectors that had been used previously.

I have yet to install my broken 8 day clock and the fuel gauge. And the right wing still contains a wire from the fuel sender that appears to send intermittent data. 

Oh and the right position light is non existent. The hole at the end of the wing was fabric'ed over.

Anyone have a green Stinson position light they'd like to sell me?

On it goes...

 

 

 


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BRUCE
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Joined: 2 years ago
Posts: 128
Topic starter  

One of the problems with getting older is that things that used to be simple are now getting harder and harder. Contorting the body to work in tight spaces...climbing up and down a ladder all day...fingers cramping on a screw driver, etc. For me seeing close up is getting to be an issue.

I wear bifocals and the lenses are shaped such that the closeup view is at the bottom of the lens because most closeup work seems to be done looking downward at the object. Unfortunately when working on something above me, 

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the glasses force me to crane my neck back to a very uncomfortable position.

Here's a silly looking but effective solution an old-timer showed me some time back.

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Robert Picard
(@bob-picard)
Trusted Member
Joined: 4 years ago
Posts: 82
 

Bruce,

I had the same problem and I went to the dollar store and got a pair of readers/cheaters or whatever you call them and got the right strength with a full size lens instead of the "half" glasses. I just pop those on and when doing close-up work I can look up and down without moving my head. I keep them in my tool box.

Bob Picard

Bob PicardN6346M Stinson 108-3 Floats/Skis/Wheels
N48923 Taylorcraft L-2B skis/WheelsAnchor Point, Alaska


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BRUCE
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Joined: 2 years ago
Posts: 128
Topic starter  

Converting instrument panel lighting to LED

As I continue to work on “loose ends” before I start working on the Franklin, my attention has now been drawn to the instrument panel lighting. There are seven incandescent light bulbs on the panel. Only one of which works. They all are of the type that press in and twist. It looks like someone in the past used clear bulbs and painted the glass red.

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I could not find any supplier of these bulbs with red glass, so I do not know what was originally used, but I began to think: do I want to replace the bulbs with the same legacy bulbs and paint them red as well, or is there something better I can do?

I decided to try to replace them with my own home made LED lights. What follows is how I did it and I am quite pleased with the result.

It all began with a set of battery powered under-counter lights my wife and I put in our kitchen a couple years ago. They helped illuminate the counter as we worked on preparing food but they ate batteries as quickly as we ate the food we were preparing.

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So we stopped using them and I finally removed them. I looked at them yesterday and saw that they each had 5 chip LEDs. Each chip LED emits a very bright white light when energized. I thought perhaps I could use one of these chips to replace one of the original incandescent bulbs in the panel.

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It would have to be a plug-in replacement, so there is no modification to the panel, only a new light that replaces the original bulb.

I began by taking apart the plastic housing of the fixture and removing the circuit board that has the LED chips. I could see beneath the paint covering the circuit board traces that each LED chip had a copper trace coming to one side and going from the other. This is as expected. For those who may not know, diodes are two pole devices that function as electronic check valves. They conduct current in one direction and do not allow current to flow in the other direction. And Light Emitting Diodes do that with the added feature that when they conduct current they glow.

Of course a standard light bulb will glow no matter which way current flows through it. So keep in mind that a difference between a filament light bulb and a LED is that the LED will only glow if the current flowing through it is going in the right direction. If you reverse the polarity, there will be no current flow and no light.

Another important difference to understand about LEDs compared to incandescent lights is that incandescent lights have their own built-in resistance, so if you place an appropriate voltage across an incandescent light, it will glow and it will intrinsically limit the current flow through the filament, achieving a stable state. A LED will not do that. When a LED conducts current (a state called “forward bias”) it is essentially a short circuit and in order to continue to work, it must have the current through it limited externally, by providing resistance in series with the LED.

The first thing I did was scratch off the layer of paint covering the copper traces feeding each side of the LED chip

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and then experiment with various resistances and my bench power supply set at 12 volts to determine what gave a good illumination and which side of the LED was positive and negative.

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I have a bag full of little resistors. There must be a red red red one in here some place!

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Yes, at 12 volts a 2.2k (2,200) ohm resistor gave good illumination and should keep the current low enough for the LED to tolerate it.

Next I took the little lamp and put it in a plastic bag and broke out the glass bulb.

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Then I used a Dremel with a side-cutting bit and, still in the bag, cleaned out all the remaining glass leaving the brass part clean inside.

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Next, putting the brass part of the lamp in a vise, I used a soldering iron to melt the button at the bottom of the lamp while I pushed the lead of the 2.2k resistor through the molten button and allowed the resistor to bottom out inside the lamp’s metal casing.

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I then clipped the excess lead and resoldered the button. I now have my current limiting resistor installed within the original metal case of the lamp with its other wire sticking up.

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I stripped the insulation off a piece of wire of similar size and carefully pushed it over the resistor’s lead all the way down to the body of the resistor. This would ensure that current from the button flowing through the resistor would not short out against the lamp housing.

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Next I soldered a fine piece of bare wire to the edge of the brass lamp housing.

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I found that a 5/16 inch wood dowel fit inside the brass housing nicely so I cut off about a half inch piece and

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Carefully notched opposite sides to allow clearance for the wires.

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Here I test fitted the dowel into the brass.

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I then cut the chip LED off the circuit board and carefully soldered a small dot onto each of the bare copper spots that I had previously scratched clean.

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Now, preparing a small batch of my favorite epoxy,

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I glued the wood plug into the brass and glued the LED chip on top of the plug.

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Once the epoxy was set, I trimmed and bent over the wires and soldered them to the correct dot of solder I had applied to the copper on the chip.

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Now to make it red.

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Not pretty, but it plugs into the receptacle in the panel and it is brighter than the original bulb! It won't be seen once the panel shroud is replaced.

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The one on the right is the original bulb (the only one of the seven that works). The other two are the LEDS I have done so far. Quite pleased with the results.

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Dan Bloemer
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Joined: 3 years ago
Posts: 12
 

Bruce, this is an outstanding series of "how-to's"; thanks!

Dan Bloemer

Amelia Island, Florida


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BRUCE
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Joined: 2 years ago
Posts: 128
Topic starter  

@bloemergmail-com Thank you, Dan. I am pleased you see value in what I am posting.

 Best wishes.

Bruce


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BRUCE
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Joined: 2 years ago
Posts: 128
Topic starter  

All the lights done. Looks like Christmas!

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Michael Samson Samson
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Joined: 3 years ago
Posts: 275
 

  Are those lights dimmable? 


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BRUCE
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Joined: 2 years ago
Posts: 128
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Posted by: @ecos36gmail-com

  Are those lights dimmable? 

No. Unfortunately, LEDs work on a completely different principal than incandescent lamps. So they are either on or off. I adjusted my panel light rheostat that is under the instrument panel and got what I expected...They were on full bright and then turned off when the rheostat made the current too low to hold the diodes in forward bias. 

You certainly can adjust the brightness of a LED illumination system if you use a technique called Pulse Width Modulation (PWM) which is not hard, but requires you to drive the LEDs from a microcontroller rather than a simple rheostat. 

But that would be way more than I wanted to accomplish with my light bulb replacement project. Maybe later...LOL

At least I got the bulbs replaced and now I can move on to the next issue...Pitot and Static.


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Michael Samson Samson
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Joined: 3 years ago
Posts: 275
 

As long as you don't need to actually use them at night, Merry Christmas!

As for a static system, maybe you don't need to bother with one. There is almost no difference between the static pressure inside your cabin and outside the cabin. Maybe if you got going really fast there would be a difference in indicated airspeed, but then you are about to crash, so it doesn't matter.

 


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BRUCE
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Joined: 2 years ago
Posts: 128
Topic starter  
Posted by: @ecos36gmail-com

As long as you don't need to actually use them at night, Merry Christmas!

Not sure why this would not be useable at night, Michael. Remember they are behind the shroud when it is installed. Is there any suggestion you have that would help me make a better solution than buying more incandescent lamps that soon burn out and painting them red?


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Michael Samson Samson
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Joined: 3 years ago
Posts: 275
 

Unless you do a lot of night flying, regular bulbs last years. You need to be able to dim the lighting to almost nothing.


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BRUCE
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Posts: 128
Topic starter  
Posted by: @ecos36gmail-com

As for a static system, maybe you don't need to bother with one. There is almost no difference between the static pressure inside your cabin and outside the cabin. Maybe if you got going really fast there would be a difference in indicated airspeed, but then you are about to crash, so it doesn't matter.

 

Interesting point. I am quite convinced you are right. It's a drafty cabin.


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Sean
 Sean
(@seancrottyaol-com)
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Joined: 2 years ago
Posts: 13
 

My only comment on this is these are certified aircraft. After I purchase N97679 in July I found all the static instruments had no hoses attached. I took them all out and had them bench tested. The ALtimeter was reconditioned but I had to replace the VVI as there was just too much damage from years of Dirt and grim. You certainly don’t want to be second guessing your primary instruments. OK - off my soap box.

 


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