B25 Miss Mitchell first bomb drop since WW2-video

tom d. friedman · **Posted:** Sat Mar 16, 2013 6:24 pm

wisler is a stand up guy, has great knowledge, a great reputation & inventory. i go back w/ him well over 20 years. you can do business w/ him with confidence 150%!!

turret nate · **Posted:** Wed Mar 27, 2013 7:53 pm

I now have the Seeburg B3 Intervalometer fully working. I found the + constant supply wire was capped in the bombardier's panel. I connected that to the buss of the master switch and the B3 now lights up when the system is energized. I had the output from the bomb panel to the bay A4 releases mistakenly wired to the pickle switch, I switched that to the output wire from the B3 - bomb releases are now correctly timed through the B3 intervalometer.

Next step is to dig into the Norden. I have a good understanding of how to get the arming bar retainer working, and the site reticule rheostat. Not sure on the mirror drive until I get the rate end computer off. But with the stabilizer not energizing I am worried what I will find in the lower portion.

The plane will start flying in mid April so I don't have much time left. The Norden piece may end up waiting until next winter's maintenance cycle.

Taigh Ramey · **Posted:** Fri Mar 29, 2013 10:09 am

It is simple to pull the sight out but it's a lot easier with two people. I'm sure you probably know how but just in case...

First remove the sight head by polling the dovetail locking pin. It is attached to the stabilizer with a ball chain. Then disconnect the clutch arm by removing the pin that connects the arm to the bronze sector gear in the sight. This pin is also secured with a ball chain or woven cable. Slide the clutch arm back out of the way. Then disconnect the sight head electrical cable from the stab. Now have the bombardiers escape hatch removed and a guy on a ladder waiting to receive the sight head. Pull the sight head straight up to get it off of the stab. You may need to swing it back and forth laterally to work it off of the dovetail bushing. Careful to not let the sight bash the stab while working it back and forth. A little oil on this shaft helps for the next install and to prevent problems. Hand the sight to your helper and be sure it is set down carefully. A sight cradle is ideal to protect the dovetail shaft but foam padding also works. The sight and stab are awkward to set down and service without stands.

For stabilizer removal you don't have to unbolt it but you can leave it on the upper half of the B-7 mount. Notice a dog bone like bar. It is a 3-4 inch machined rod on the right side of the stab mount with rounded knobs on each end. Also notice the slotted locking collar on its shaft. If you slide the locking collar away from the rod it will allow the rod to be rotated 180 degrees. Careful because this will unlock the upper B-7 mount with the stabilizer from the lower part of the B-7 mount and if you aren't ready it will fall forward and can break your bomb sight glass.

Once the stab/mount is unlocked you can lift it straight up to clear the lower mount. Now hand this off to your helper on the ladder and be extra careful to not let the clutch arm get bent or damaged. The gyro inside is also delicate and shouldn't get banged. Hopefully it still has its shipping plate installed that locks the gyro. The sheet metal servo cover on the stab is also easy to dent as its made from real soft aluminum.

The sight head and stab are about 25 pounds each. The stab with the upper B-7 mount is more.

Set the stab on the bench carefully and now you have easy access to open up the sight and stab.

Maybe your museum has the original shipping stands for the sight head and stab which will make it easier to work on. If not I can send photos of hem so you can build ones.

If the Dog bone bar is stuck you can try rocking the stab while turning it to help relieve he tension. If its really stuck then you might have to remove the three bolts that secure the stab to the mount. These are special shear bolts that are stepped and necked.

Also check the rubber shock mounts in the B-7 stab mount to see if they might need to be replaced.

I hope this helps

turret nate · **Posted:** Fri Mar 29, 2013 2:59 pm

Great info, I was unsure how to remove those items - your post helps alot. I don't think we have any of the shipping stands but I will check.

turret nate · **Posted:** Sat Mar 30, 2013 3:59 pm

Taigh, Big progress today. I got the sight rheostat freed up (still no light when powered so the bulb is probably dead) and the arming lever retainer working correctly. I removed the rate end plate with the stuck knobs and got the outer one freed up. I had to drive the pin out of the small clutch knob, then was able to remove the knob assembly. A thorough cleaning and oiling freed up the moving parts.

I also removed the rate end computer and found the mirror cable was off the pulleys. I corrected this and oiled the inside of the computer. Now the tachometer is spinning and the automatic portion of the sight is working as expected. I still need to get into the other side of the sight to oil the gyros. Any advice on the best way to open the other side and what points to oil? I have sewing machine oil ready to apply.

I also pulled the side (connector) panel and front panel on the stabilizer. I found all of the wires to be apparently connected. The inside of the unit looks very clean. The stabilizer continues to do nothing when energized.

Taigh Ramey · **Posted:** Sun Mar 31, 2013 2:27 am

It's strange that both the gyro and the servo in the stabilizer are not powering up. I have seen the gyro not spin up because of brush issues but with both not running it makes me wonder if power is making it through the stab switch on the stabilizer switch panel. Check for power coming out of the stab switch as power goes from the stab switch to the servo switch. If the stab switch has died then maybe it is what's causing your problem.

You can remove the top cover of the sight head by removing all of the screws around the perimeter. Lift the cover up and notice a very light coat of grease on the mating surfaces to keep it sealed up. You will be able to rotate the cardan assembly to get to the brushes and bearings. Use a syringe with a long needle to get to the bearings. Give a light pull on the leads attached to the brushes to be sure they aren't stuck to the armature. Watch out for the real fine wires that go from the cardan assy to the top of the gyro. They are carefully routed to impart as little drag or precession as possible between the cardan and the gyro. Delicate little cloth covered wires that were originally formed with wood tweezers.

Pretty amazing what all went into making and servicing these fine instruments. It sure gives you an appreciation for the guys doing bombsight surgery out in the field.

How about posting some photos of the operating room and your patient?

turret nate · **Posted:** Sun Mar 31, 2013 3:09 pm

Thanks Taigh. I stopped down today and check voltages inside the stabilizer. I found voltage to the input of the switch but not the output. I saturated the switch with contact cleaner and worked it to no avail. The servo switch did check out.

I bypassed the switch with an alligator clip and energized the master on the bomb panel, at which point the stabilizer activated. After a few minutes of spinning up I threw the servo switch, which worked.

Do you happen to have any spare vintage stabilizer switches? Otherwise I will put in a modern switch.

Thanks for the guidance on the top cover removal. I will work on oiling up those bearings next time I go to the hanger. I assume the stabilizer gyro should be oiled too?

For my work space I have been just working in the nose rather than pulling the sight out. Here is a new video showing the progress as of today, showing the running Norden stabilizer and intervalometer:

http://youtu.be/yfxo76axUq0

tom d. friedman · **Posted:** Mon Apr 01, 2013 5:14 am

jay is a stand up guy & business man. you can buy with confidence.

turret nate · **Posted:** Wed Apr 03, 2013 7:47 pm

Taigh, I replaced the STAB on/off switch today and got that working again. I had to use a modern switch with a slightly longer arm but its working well.

I then removed the top cover and oiled the bearings. Also oiled the bearings in the stabilizer. Both of those sound better when running now. But when I turn the servo on it sounds grindy, I need to get in there and oil it. The cover is hard to get the inside lower screw off do to the stabilizer mount being in the way. I think I will need to remove the stabilizer from the mount to get the cover off.

I also got the parts I ordered from Jay, including the Norden maintenance manual.

Thanks again for your help.

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B25 Miss Mitchell first bomb drop since WW2-video

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