How to remove a Howard Yeoman rotavator clutch?

[jwilkes]

This question has been asked when I look at web searches a couple of times. As I am part way through the process of rebuilding the drive train I thought I should document the process.
Several references will be made to the Howard yeoman Manual (copy found here: https://www.allotment-garden.org/rotavator-manuals/yeoman1957handbook.pdf
Item numbers as listed
The following description is based on observations from a strip of machine number 5298 originally fitted with the BSA 420cc power unit
What should be possible
1) Remove “Cover Plate” (45)
2) This should give access to the “P.T.O. shaft” (64)
alternatively remove the “Sliding Dog” (66) DO NOT REMOVE the “Clutch Housing” (74)
3) Engage High or Low gear lock the “P.T.O. Shaft”
4) Now unscrew “Clutch Shaft Nut” (13)
You will probably need to make a special tool for this as there is insufficient access inside the Bell housing to get access with a conventional “C” spanner
There is a high breakaway torque as the nut is peened to prevent unscrewing
5) The clutch assembly (Items 14-21) should then be pulled off the spline and disassembled

With regards to the clutch itself. As I am planning on fitting an uprated engine to the gearbox I needed to inspect the plate for wear before is wears out. The original plate is about 8mm thick, in my case there is still 5mm of wear plate left – Drawing “jrw-00050.PDF” for anyone interested.

Attachments:

1. jrw-00050.pdf

[jwilkes]

Thought an update would be useful to record

Clutch nut is 9/16 BSF thread having damaged the threads I am in process of repairing with Helicoils.

I found that with the dog clutch removed a 17mm rounded but socket can be used to lock the PTO shaft.

[jwilkes]

After stripping the engine off to get the new mounting plate painted I managed to break the drive teeth off the old clutch plate. New plate arrived today and is process of fitting. Thought I should mention “Industrial friction materials” in Cardiff. Although took several weeks they took the flywheel, cleaned and painted the unit then cut the new plate to match the flywheel. Not necessarily the cheapest solution but I can say that the quality of the service and attention to detail really could not ne faulted.

Anyone needing new friction plates – they can also make the metal plates in a multiplate system could do worse than contact this supplier

Attachments:

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