I am wondering how much stronger the
drilling and pinning is than the welding of the input shaft. Are there
any disadvantages or drawbacks to drilling and pinning (other than the effort
involved in making the modification)? As I understand it, Dave Leonard’s
engine was backfiring when the shaft broke (I do not know about Steve Brook’s
incident). Absent some abnormal torque pulses, such as backfiring, can we
still expect that a 13B Turbo engine will break a welded shaft? If
drilling and pinning is the superior method, why wasn’t that method used
to begin with?
Bob Rogers
(agonizing over having to remove my RD-1B
Redrive - again)
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Tracy Crook
Sent: Saturday, January 07, 2006
10:52 AM
To: Rotary motors in aircraft
Subject: RD-1B Service alert
Service Alert on B
drives
I will publish a
service alert later today on the website (www.rotaryaviation.com)
on B drives used on turbo charged 13Bs and 20B engines.
Decided to do this
after reviewing Steve Brooks input shaft problem. His input shaft was
previously used for well over 100 hours on Ed Anderson's drive (fairly early
drive) with no problems. It used the welded style sun gear attachment to
the input shaft. Steve's turbo engine apparently had enough torque to break
the weld in the same way that Dave Leonard's (another turbo) did.
Shortly before starting C drive production (4-23-03) we changed over to a drilled and pinned input
shaft. This service alert requests (strongly) that any B drive used on a
turbo charged 13B or 20B engine delivered before this date be inspected for
presence of a pinned input shaft. If the sun gear is welded instead of
pinned, the input shaft should be returned to RWS to have it drilled and pinned
prior to any flight. This service will be performed for only the
cost of materials and shipping. No problems have been encountered on
RD-1, RD-1A or RD-1B drives used on normally aspirated engines but if you wish,
this update can be done for a nominal service charge ( parts &
shipping + shop time TBD).