rwdfresno wrote:
Taigh,
I remember sitting in the turret of your AT-11 when Tim was being the bombardier. I remember him dropping a practice bomb on the bomb bay doors and sand pouring out and blowing around. I also remember you not being so happy about that
. It was great being a 12 year old around old airplanes. Tim was sure a character but he sure was talented. I think we still have some obliterated 100 pounders around. Lately we have had regular C130 cargo drops. It is pretty cool to watch.
Ryan,
Too funny. I had forgotten about Tim dropping the bomb on the AT-11 bomb bay doors. He sure was talented and a fun guy to play with. I miss him and all the fun we should have had.
Nate,
Sorry for the slow response as I have been on a trip for a while now. I saw your video and I think you have some real problems going on. I have noticed that many Norden that have been in the nose of an aircraft for any period of time, especially where the public can play with it, it is likely to be in real bad shape. The Norden is a delicate piece of equipment and will not stand up to too much public attention or exposure. We keep the running sights in a display case or in storage and use a beater for general flying. If your museum has a good sight then you might want to try a different one or its time to learn about internal Norden maintenance.
A couple of observations:
Some sights and stabilizers were sold that were restored cosmetically. Sometimes you open them up and you may find that they are not so nice inside. I have seen stabilizers with the internal wiring cut out but the wiring from the input from the stabilizer through to the bomb sight was still good. I would open up the electrical panel with the switches and connectors on the stab and see how it looks. It's just 4 screws.
As soon as you turn on the stab switch the stab gyro should power up. When the servo switch is thrown then the servo/erection motor should spin up. Since both of these do not work I would suspect that they have been disconnected as often seen on the 'restored' stabs.
A word of caution here. The gyros in the sight and the stab have large counterweights that turn at high speed and have high precision bearings. It is important that they are in good shape because if the bearings are rusted or worn out then the gyro could become unstable. A small amount of good bearing oil is often needed to keep them lubricated since they probably haven't seen any oil in many decades. The manual actually has a time needed for the gyro to spool down once power was removed. The shorter time was indicative of bad bearings. Mostly you can tell by the sound of the bearings and you hear if they sound dry or kind of grindy. From what I could hear in the video your sight head gyro sounds good but I would recommend oiling the bearings.
the outer knob on the sight head that is real stiff is the displacement knob and drives, among other things, the optics through a real fine cable. This knob should be real smooth and be sure not to force anything as you might break or stretch the cable or do other damage. The sight is real delicate and if something does not work smoothly then it can be easily hurt. Open it up and see what is going on inside. The whole rate end can be removed carefully to see what is going on. Besides the screws around the circumference you need to remove the pin that connects the rack on the trail arm.
The top casting (the one that has the caging knob) comes off of the sight easily with removing the screws too. This will give you access to the gyro and optics. You will then be able to see the fine cable that comes from the rate end through the pivot bearings and around the pulleys to drive the mirror on the optics cradle.
The caging knob simply releases the gyro. The gyro in the sight head keeps the optics cradle stabilized and level to the ground. The two silver knobs on the end cap of the sight head are for leveling the gyro. These knobs are often stuck and need help to operate properly. They can be pushed in and rotated to adjust the gyro cardan an assembly to level the gyro with the two level bubbles on top of the gyro. These knobs should spring back freely and not touch the cardan. When your gyro is spooled up then uncage the gyro and try to adjust the cardan with the leveling knobs. You can also move the sight around and see that the optics and gyro stay level. There is usually enough slop in the sight mount that you can rock it enough to see the gyro move when uncaged.
The lever you mentioned is the firing trigger for the sight and is normally held in place with the plunger. Yes the plunger should be free to ratchet into place so it will also need some attention. The fine stainless steel wire that sticks out just forward of the trigger lever and plunger can be pushed forward slightly to release the trigger. This mechanism can be accessed by removing the whole housing (4 screws). Some oil should help to free it up.
When the contacts come together in the firing circuit as the sighting angle equals the dropping angle or when the indices come together a single pulse of electricity comes out of the sight to the bombardiers panel and to the intervalometer is selected. Normally the firing mechanism is armed with the trigger lever and the sighting angle is lower than the dropping angle. As the sighting angle meets the dropping angle the contacts come together and then snap away. In the video it looks like ou are coming at it with the rate knob and holding the contacts instead if it making and breaking contact like it normally should when it operates in the opposite direction. I am not sure but this could be messing up the intervalometer. The intervalometer should just get one firing pulse and it should instantly fire off and then each successive pulse should go out in equally spaced timing. It could be that instead of one pulse the intervalometer is getting a steady 28 volts which may be messing it up. The whole having to hold down the firing button says to me that something is wrong in the intervalometer. If you have another one try swapping it out. There is an electron tube inside the the intervalometer that usually needs to warm up. From the video it almost looks like it is getting power and having to warm up to then start working. Please be sure the power circuit is wired correctly and also be sure you have the correct type of intervalometer in use for the wiring diagram. There is one with larger pins for B-29's and other aircraft that needed larger capacity circuits and I am not sure if the pin outs may have been different between the two types. Also some intervalometers were modified by the navy for firing rockets so double check to be sure the wiring in and out is correct for our circuit.
Lots of things to check.
Great work Nate
_________________
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Thank you!
Taigh Ramey
Vintage Aircraft, Stockton, California
http://www.twinbeech.com'KEEP ‘EM FLYING…FOR HISTORY!'
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