[Healeys] DW overdrive piston

[Bob Spidell]

Warren,

Your accumulator piston and housing look to have a bit worse scoring 
than mine; I used synthetic fluid for over half the life of mine, I 
wonder if that made a difference?


>
> Sent from Mail <https://go.microsoft.com/fwlink/?LinkId=550986> for 
> Windows
>
> This was the condition of my piston and housing with close to 200,000 
> miles. Tranny was well maintained.
>
> The original metal rings lasted 53 years. So I guess with unknown 
> quality of either of todays metal vs rubber
>
> O rings, let the experiments begin.
>
> *From: *Bob Spidell <mailto:bspidell at comcast.net>
> *Sent: *Wednesday, August 3, 2022 10:12 PM
> *To: *healeys at autox.team.net
> *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" <mailto: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 <bspidell at comcast.net>
>     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
>         >
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://autox.team.net/pipermail/healeys/attachments/20220804/f467177b/attachment.htm>