Hand crank turntable any good?

The hand crank was an option with the Diamond scale TT.   There is also a Diamond scale electric drive.  Diamond scale TT's are/were well built kits that if properly assembled were exceptional quality machines.  IMO. 
The Diamond Scale Website is still up, some of the parts may be available. I noted that the hand crank was still there.   Click on the underlined phrases to link.  TT parts are listed, O scale parts are listed separately and usually are more robust/ more expensive. than the N, HO, and ON3/30  parts.

Note the small 12 volt electric motor and gear box attached via a plastic universal joint.

A Diamond Scale OT 105 Turntable operating.  Click to access a video.

Access to a picture file of a semi-scratch build TT using a:

(1.) Diamond Scale drive

(2.) Diamond Scale parts

(3.) Bowser parts

(4.) Crow River parts

(5.) Kappler Lumber

(6.) K&S Metals

(7.) Woodland Scenic materials

(8.) Scenic Express materials

(9.) Atlas Track and screws

(10.)  other parts.

(11.) Aluminum bridge and pit wall were done locally at a fab shop.

(12.) 7/16" Drive shaft/T-bar were also done locally at a fab shop.

Have fun  Mike CT

I used one reliably for several years on my old HO layout. I needed one for the O Scale TT that I scratch built and decided the Diamond Scale hand crank setup was to much money. Built my own instead. I see absolutely no need to power a TT verses using a hand crank to turn it. But many folks are addicted to electrifying everything...not sure why.

Bob

I had the above kit but hooked it up incorrectly so I gave up on it. I made a large disc and a smaller pulley with a drive belt. I have not electrified it yet but I just pull on the belt and it goes around.

I love it!  The KISS principle at its finest.

Pete