The ball turret itself, carrier and ring gear are identical for both the B-17 and the B-24. The differences between the two were in how the turret ring gear was mounted or hung from the ceiling or overhead structure in the aircraft. Early on the B-17 hanger assemblies were essentially one piece and the B-24 hangar that used a shorter sawhorse type of hangar and sa hydraulic cylinder for retracting. Later B-17's changed over to the same sawhorse as used on the B-24 and had a welded up solid tube assembly instead of the retracting cylinder used on the B-24.
This may be confusing so I will try to use photos to explain:
In this shot from a manual showing the full turret is broken up into its major sub assemblies. What's labeled the turret ball structure and the trunnion ring support and azimuth ring gear are is the parts that are identical and are interchangeable between the B-17 and the B-24. As i mentioned there are stencils and placards on the later turrets for both B-17 and the B-24 as the factory didn't differentiate one turret for one specific aircraft. The differences came in the mounting.

The hangar tubing assembly and collector ring shown in the photo above are the later more common ones used in both the later B-14 and in most all of the B-24's.
This is the early B-17 hangar assembly. One piece welded with a real long slender slip ring, or collector assy (for power and interphone) built into the tube. This is early B-17 only.

The actual ring gear is identical between both aircraft but how it mounts is different. In the B-17 it is mounted through shock mounts and is fixed to the aircraft structure.
In the B-24 the ring gear is in a carrier assembly that is attached to the the trunnion ring support and has four large bushings that slide up and down in tubes to allow it to retract in the B-24.
Here is the ring carrier for the B-24 and you can see some of the bushings that the four tubes ride in.

Back to this image that shows the solid hangar tube and ring gear for the B-17.

In the B-24 instead of the tube they used a hydraulic cylinder to retract the whole turret, hangar, trunnion and ring carrier.

This post seems pretty muddled so I hope it helps to explain that the turrets are the same and only the mountings differ between the Flying Fortress and the Liberator. Sure there are other variations but this covers the basics and common installations.
_________________
To donate to the PV-2D project via PayPal click here
http://www.twinbeech.com/84062restoration.htmWe brought her from:

to this in 3 months:

Help us get her all the way back

All donations are tax deductible as the Stockton Field Aviation Museum is a 501c3 nonprofit organization. Tell a friend as the Harpoon needs all the help she can get.
Thank you!
Taigh Ramey
Vintage Aircraft, Stockton, California
http://www.twinbeech.com'KEEP ‘EM FLYING…FOR HISTORY!'