[Healeys] DW overdrive piston

[gradea1 at charter.net]

I checked with David at OD Spares as to availability. Here is his
response:
Hi Hank we use both styles the steel piston rings are all still
available as are new pistons and the aluminium housing they both work
equally wellWe can supply any of your overdrive requirements
best regards Dave

_OVERDRIVE SPARES__10 ARCHES BUSINESS CENTRE__MILL
ROAD__RUGBY__WARWICKSHIRE__CV21 1QW__ENGLAND_
_EMAIL: ODSPARES at AOL.COM__TELEPHONE NUMBER: 01788 540666__FAX NUMBER:
01788 570777__WEB: WWW.ODSPARES.COM_

	-----------------------------------------From: "Bob Spidell" 
To: healeys at autox.team.net
Cc: 
Sent: Wednesday August 3 2022 7:15:22PM
Subject: Re: [Healeys] DW overdrive piston

 The rings will score the inside of the piston housing, though not
badly (photo at 205K miles). Looks like there's a side load on the
piston, probably from the spring.

 I donated this accumulator to another owner; never heard how they
worked. Moss shows the rings available (but who knows?).

On 8/3/2022 12:36 PM, Henry G Leach via Healeys wrote:
  I assemble ODs using the original metal rings and have not had any
issues with pressure or engagement/disengagement. 
 When Mr. DeNormanville stayed up in the middle of the night to
engineer the operation of the unit, I think he decided that the use of
softer rings (sacrificial metal) against a hardened casing was the
best solution for control and wear. If a rubber o-ring was a better
solution, he would have used one with the proper buna rating. 
 I think the bigger problem, now-a-days, is the availability of the
metal piston rings. Rubber O rings are a dime-a-dozen. If you contact
Overdrive Spares in the UK, they should be able to supply the proper
rings. If they too, have decided to go with rubber, then plan on a
breakdown/rebuild in a shorter period of time than units equipped with
the original parts that last a long, long time. Hank

	----------------------------------------- From: "Michael Salter"
 To: "healeys at autox.team.net"
 Cc:
 Sent: Wednesday August 3 2022 9:38:15AM
 Subject: Re: [Healeys] DW overdrive piston

 I have a question about the "O" ring type of accumulator. The way the
accumulator works is that when it is fully charged the piston moves
against the spring until the rings reach the radial holes in the wall
of the housing which acts to relieve any excess pressure. My concern
is that at 3 - 400 p.s.i. oil will obviously get behind the "O" ring
and force the material of the "O" ring into those radial holes and
then, as the piston moves back over them, a piece of the ring will
shear off. I'm guessing that Laycock-DeNormanville used the complex
cast iron rings rather than "O" rings because they recognized the
possibility of this happening.
 I'm sure that tiny pieces of the "O" ring would be found in the
filter if this was a problem. Anyone found them or noticed damage to
their accumulator "O" ring upon disassembly?

 M

 On Wed, Aug 3, 2022 at 9:08 AM Bob Spidell  wrote:
  I put one in my BJ8's O/D. It's subjective*--O/Ds seem to work a
little
 quicker with cold, thick oil than hot oil--but it cuts maybe a third
off
 engagement time on average. I had the O/D on the bench and
disassembled,
 and the current one had a scored barrel so, why not? Engagement isn't
 much, if any, harsher than before which, I believe is the reason DMH
 wanted the weaker, smaller spring. If I'd known about it, I might
have
 bought AHSpares' with an O-ring instead.

 * I've never really 'timed' O/D functioning, it would be a bit
awkward;
 anyone done it? I usually tap the clutch pedal when engaging O/D, and
 give a little throttle when disengaging. I thought mine engaged a
little
 quicker when I switched to synthetic fluid from engine oil, but in
all
 cases confirmation bias may be involved.

 On 8/2/2022 8:09 PM, Joseph Costa wrote:
 > Has anyone installed their upgraded overdrive piston? If so, is it
 > worth the trouble ?
 >
 > Joe
 > BN1 #923
 >


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