The Ham IV uses a different lower bell housing than the older Ham M, and
Ham II series. and a wedge that's more square than the older rounded tip.
Both upgrade parts are available from the Rotor Doctor, the lower bell
housing is $25(USD). He has 2 different styles of wedges, the stock
(square) wedge and his own improved version. Don't recall the
price, someplace in the $10 - 15(USD) range for the wedge.
I haven't followed this thread, but make sure the mast isn't slipping vs
the brake assembly needing replacement.
If you do open the bell housing, get one of those cheap plastic storage
bins at Wal-Mart. Separate the bell housing with the rotor laying in the
storage bin. This will keep the 98 ball bearings contained just in case
they decide to go traveling.
>I *believe* the brake wedges in the HAM-M are 'rounded',
>sort of like a bunch of 'speed bumps' around the base of
>the rotor on the inside. The brake wedge fits between those
>bumps. If you have a high torque antenna (long boom,
>large area antenna), the wedge can be dragged over those
>bumps, wearing them down. A new rotor bottom cover
>might (temporarily) solve the problem. A permanent fix
>would be a rotor with a stronger brake such as the tailtwister
>(which has it's own problems...the brake wedge tends to jam
>in the Square brake bumps). I'm not sure if the HAM IV
>has higher 'bumps' than a HAM-M. Perhaps the Rotor Doc
>or Norm's can tell you.