jimmymc wrote:Jesus whitworths way before my time! Haha!
I'll dig some out!
I have only now noticed this thread, it looks as though you have a good project to get your teeth into there.
I repaired and overhauled lots of these things for a number of years before running some myself and can tell you that you don't need any Whitworth spanners.
The compression bolts for the slew clutches are 7/16 UNC. They are 2.1/4 inches long and need the thread turned down at the end to form a spigot.
I think from memory the spigot was about 5/16 inch long and 3/16 in. diameter. Hopefully you wont need them, but I will be happy to answer any questions you may have as you go along.
The only bolts on the Drotts which don't have UNF or UNC threads are the specials which secure the front cross beam to the track frames these have fine NS threads but they still have AF heads.
This may sound strange but I have in the past had good success with freeing rusty , (seized), bores as you describe by letting them stand with vinegar in them for a few days before putting diesel in them, then removing the starter and baring the flywheel round. You will need to lift the loader arms out of your way to get at it .
I can't agree that they are difficult to bleed or start, but good starting is very dependant on the heater plugs being in good order like all indirect injection engines