Re: [Healeys] Laycock overdrive

[Robert Parker via Healeys <healeys@autox.team.net>]

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Generally speaking, if a spring load is such that it=E2=80=99s design fatigu=
e yield stress is not badly jeopardize, it can almost last indefinitely. How=
ever, practically speaking, does anything last forever? Spring design is not=
 a simple thing, and it takes a lots of cycles to prove that a particular de=
sign can meet design life expectations. It=E2=80=99s extremely expensive to t=
o do that in today=E2=80=99s environment. So then practically speaking, the d=
arn things will probably go forever. Given of course that those ideas you ha=
d above, good material etc., are in force. Bob ,61BT7.

Sent from my iPhone

> On Aug 13, 2023, at 12:04 PM, Roger Grace <roggrace@telus.net> wrote:
>=20
> =EF=BB=BF
> Yes totally agree that hi carbon spring steel does not age if not abused.=20=

> Having said that, it would be good practice to compare free lenghts agains=
t a known good quality one
>=20
> Found this on a spring manufacturers site.
> The first question is =E2=80=98could a spring last forever?=E2=80=99 and t=
he answer is yes, it could do if
>=20
> The operating stresses are not too high
> The working temperature does not cause the spring to lose too much load
> The environment does not cause corrosion
> The spring is not abused
> The spring is well-made and free from imperfections.
> If a spring meets the above requirements, yes it could potentially last fo=
rever!
>=20
> rg
>=20
>=20
>       Virus-free.www.avg.com
>=20
>> On Sun, Aug 13, 2023 at 9:40=E2=80=AFAM Michael Salter <michaelsalter@gma=
il.com> wrote:
>> Re: "Yes, springs wear out."
>> Correctly designed, manufactured and installed springs don't wear out.
>> Very occasionally they will suffer from fatigue cracking but that is rare=
 and a function of poor design.
>> Think valve springs or distributor point springs; millions and millions o=
f cycles and still as good as the day they were installed.
>>=20
>> M
>>=20
>>=20
>>> On Sat., Aug. 12, 2023, 2:25 p.m. Hank Leach via Healeys, <healeys@autox=
.team.net> wrote:
>>> Bob-good point.  I just got a set of springs from Moss (from OD Spares i=
n UK, I imagine). The cost was $99 or about $12/spring which in the scope of=
 things is really not relevant. Holding that clutch in tight contact to the b=
rake ring is paramount and just imagine the number of miles in direct drive t=
hat the car has experienced...many at high RPM. The other side of the brake f=
or overdrive position is the "lazy side" as the operating pistons under hydr=
aulic pressure have plenty of clout driving mostly steady RPMs. Yes, springs=
 wear out.
>>>=20
>>> I place them on the bench and line up the lengths. They should measure 4=
-1/2" for the long springs and 4-1/4" for the short ones but invariably ther=
e is differences in the resting length. After 50+ years of pushing you would=
 tend to get tired. When in overdrive, the springs are greatly depressed.  T=
hat is asking a lot for spiral metal to accomplish. So, yes they may look go=
od, but have poor stamina-oops, I just describe all of us. Hank
>>>=20
>>> -----------------------------------------
>>>=20
>>> From: "Bob Spidell"=20
>>> To: healeys@autox.team.net
>>> Cc:=20
>>> Sent: Friday August 11 2023 9:19:34PM
>>> Subject: Re: [Healeys] Laycock overdrive
>>>=20
>>> re: "... The health of the 8 springs that keep the unit in direct drive
>>> is important to keep the clutch from slipping...."
>>>=20
>>> I believe the shop manual admonishes owners to replace these when
>>> overhauling the unit, even if the old ones look and feel fine (some say
>>> not so). I think my old ones are in a box on a shelf somewhere if
>>> anybody wants them.
>>>=20
>>> Note the O/D pump is a positive displacement pump that will continue to
>>> produce pressure--driven by the full power of the engine--unless there
>>> is a pressure relief mechanism.
>>>=20
>>>=20
>>> On 8/11/2023 10:34 AM, Hank Leach via Healeys wrote:
>>> > Guys-this is a very lively topic and one of sometimes great mystery
>>> > and confusion.  The unit is complex but the end result is working well=

>>> > or not functioning at all.
>>> >
>>> > On the subject of pressure required to operate the shift into
>>> > overdrive there are many schools of thought. Some people replace or
>>> > stretch springs or add washers to increase the pressure needed. The
>>> > health of the 8 springs that keep the unit in direct drive is
>>> > important to keep the clutch from slipping.  The pressure supplied to
>>> > overcome the strength of these 8 spring , and effect overdrive, relies=

>>> > on adequate hydraulic pressure. The change from direct to overdrive
>>> > needs to be smooth, not harsh, and if pressures are high the unit will=

>>> > snap into and out of OD rather than the smooth interchange we are used=

>>> > to while driving.
>>> >
>>> > When applied to the Austin Healey 100, the Laycock overdrive was
>>> > initially a 32% reduction unit. It was soon found out in these early
>>> > Warwick cars that 32% was too much reduction.  DHMC swapped units
>>> > three times in the original DMH tour car until they finally found a
>>> > combination that produced the smooth shift and complimentary gearing
>>> > desired.
>>> >
>>> > It is difficult, today, to find any information on this original 32%
>>> > gearbox, however if you examine the booklet (attached) supplied by
>>> > Laycock for the early cars, you will notice that the casting allowed
>>> > for a large accumulator piston (seen on p6 in brochure). After some
>>> > research and modified engineering, the company came up with this alloy=

>>> > "sleeve" called the piston housing (photo) which partially filled the
>>> > chamber of the original large accumulator casting and allowed for a
>>> > smaller accumulator piston that we see in all the later 28% reduction
>>> > units. That size piston, in proper condition, produced from 350-450
>>> > lbs of needed hydraulic pressure to overcome the springs influence.
>>> >
>>> > I'm confident that the remark made by Geoff Healey in his writings
>>> > about the early transmissions "harsh shifting" revolved around this
>>> > huge accumulator piston producing too much pressure. Additionally,
>>> > there were three various accumulator springs supplied which adjusted
>>> > the pressure. The early boxes produced about 350lbs and the later
>>> > about 450.
>>> >
>>> > Today, Overdrive Spares supplies that sleeve housing with only one
>>> > rubber O-ring as it is basically a filler part and not under extreme
>>> > pressure. The accumulator piston within is under that pressure. They
>>> > supply a modified piston using O-ring technology. So, it is not
>>> > unusual to get good pressures over the normal 450 lbs required. If it
>>> > works well don't fix it.  The only concern is if the pressure does not=

>>> > release when overdrive is not called for. A clean unit, with proper
>>> > 30W oil, will allow that to happen. All this some old theory and
>>> > history to ponder. Hank
>>> >
>>>=20
>>> _______________________________________________
>>> Support Team.Net http://www.team.net/donate.html
>>> /> Suggested annual donation $12.75
>>>=20
>>> Archive: http://www.team.net/pipermail/healeys http://autox.team.net/arc=
hive/healeys
>>> />
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>>> http://autox.team.net/mailman/listinfo/healeys
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>>> Support Team.Net http://www.team.net/donate.html
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>>>=20
>>> Archive: http://www.team.net/pipermail/healeys http://autox.team.net/arc=
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>>>=20
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>>>=20
>> _______________________________________________
>> Support Team.Net http://www.team.net/donate.html
>> Suggested annual donation  $12.75
>>=20
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e@telus.net
>>=20
> _______________________________________________
> Support Team.Net http://www.team.net/donate.html
> Suggested annual donation  $12.75
>=20
> Archive: http://www.team.net/pipermail/healeys http://autox.team.net/archi=
ve/healeys
>=20
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>=20
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r@juno.com
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<html><head><meta http-equiv=3D"content-type" content=3D"text/html; charset=3D=
utf-8"></head><body dir=3D"auto">Generally speaking, if a spring load is suc=
h that it=E2=80=99s design fatigue yield stress is not badly jeopardize, it c=
an almost last indefinitely. However, practically speaking, does anything la=
st forever? Spring design is not a simple thing, and it takes a lots of cycl=
es to prove that a particular design can meet design life expectations. It=E2=
=80=99s extremely expensive to to do that in today=E2=80=99s environment. So=
 then practically speaking, the darn things will probably go forever. Given o=
f course that those ideas you had above, good material etc., are in force. B=
ob ,61BT7.<br><br><div dir=3D"ltr">Sent from my iPhone</div><div dir=3D"ltr"=
><br><blockquote type=3D"cite">On Aug 13, 2023, at 12:04 PM, Roger Grace &lt=
;roggrace@telus.net&gt; wrote:<br><br></blockquote></div><blockquote type=3D=
"cite"><div dir=3D"ltr">=EF=BB=BF<div dir=3D"ltr"><div>Yes totally agree tha=
t hi carbon spring steel does not age if not abused. <br></div><div>Having s=
aid that, it would be good practice to compare free lenghts against a known g=
ood quality one<br></div><div><br></div><div>Found this on a spring manufact=
urers site.</div><div>
<p><i style=3D"font-family:comic sans ms,sans-serif">The first question is =E2=
=80=98could a spring last forever?=E2=80=99 and the answer is yes, it could d=
o if</i></p><ul><li><i style=3D"font-family:comic sans ms,sans-serif">The op=
erating stresses are not too high</i></li><li><i style=3D"font-family:comic s=
ans ms,sans-serif">The working temperature does not cause the spring to lose=
 too much load</i></li><li><i style=3D"font-family:comic sans ms,sans-serif"=
>The environment does not cause corrosion</i></li><li><i style=3D"font-famil=
y:comic sans ms,sans-serif">The spring is not abused</i></li><li><i style=3D=
"font-family:comic sans ms,sans-serif">The spring is well-made and free from=
 imperfections.</i></li></ul><p><i style=3D"font-family:comic sans ms,sans-s=
erif">If a spring meets the above requirements, yes it could potentially las=
t forever!</i></p><p><font face=3D"arial,sans-serif">rg<br></font></p>

</div></div><div id=3D"DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br><table styl=
e=3D"border-top:1px solid #d3d4de"><tbody><tr><td style=3D"width:55px;paddin=
g-top:13px"><a href=3D"http://www.avg.com/email-signature?utm_medium=3Demail=
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ns/icon-envelope-tick-green-avg-v1.png" alt=3D"" width=3D"46" height=3D"29" s=
tyle=3D"width: 46px; height: 29px;" data-unique-identifier=3D""></a></td><td=
 style=3D"width:470px;padding-top:12px;color:#41424e;font-size:13px;font-fam=
ily:Arial,Helvetica,sans-serif;line-height:18px">Virus-free.<a href=3D"http:=
//www.avg.com/email-signature?utm_medium=3Demail&amp;utm_source=3Dlink&amp;u=
tm_campaign=3Dsig-email&amp;utm_content=3Dwebmail" target=3D"_blank" style=3D=
"color:#4453ea">www.avg.com</a></td></tr></tbody></table><a href=3D"#DAB4FAD=
8-2DD7-40BB-A1B8-4E2AA1F9FDF2" width=3D"1" height=3D"1"></a></div><br><div c=
lass=3D"gmail_quote"><div dir=3D"ltr" class=3D"gmail_attr">On Sun, Aug 13, 2=
023 at 9:40=E2=80=AFAM Michael Salter &lt;<a href=3D"mailto:michaelsalter@gm=
ail.com">michaelsalter@gmail.com</a>&gt; wrote:<br></div><blockquote class=3D=
"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(20=
4,204,204);padding-left:1ex"><div dir=3D"auto">Re: "Yes, springs wear out."<=
div dir=3D"auto">Correctly designed, manufactured and installed springs don'=
t wear out.</div><div dir=3D"auto">Very occasionally they will suffer from f=
atigue cracking but that is rare and a function of poor design.</div><div di=
r=3D"auto">Think valve springs or distributor point springs; millions and mi=
llions of cycles and still as good as the day they were installed.</div><div=
 dir=3D"auto"><br></div><div dir=3D"auto">M<br><div dir=3D"auto"><br style=3D=
"font-size:12.8px"></div></div></div><br><div class=3D"gmail_quote"><div dir=
=3D"ltr" class=3D"gmail_attr">On Sat., Aug. 12, 2023, 2:25 p.m. Hank Leach v=
ia Healeys, &lt;<a href=3D"mailto:healeys@autox.team.net"; target=3D"_blank">=
healeys@autox.team.net</a>&gt; wrote:<br></div><blockquote class=3D"gmail_qu=
ote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204=
);padding-left:1ex"><div>Bob-good point.&nbsp; I just got a set of springs f=
rom Moss (from OD Spares in UK, I imagine). The cost was $99 or about $12/sp=
ring which in the scope of things is really not relevant. Holding that clutc=
h in tight contact to the brake ring is paramount and just imagine the numbe=
r of miles in direct drive that the car has experienced...many at high RPM. T=
he other side of the brake for overdrive position is the "lazy side" as the o=
perating pistons under hydraulic pressure have plenty of clout driving mostl=
y steady RPMs. Yes, springs wear out.<div><br></div><div>I place them on the=
 bench and line up the lengths. They should measure 4-1/2" for the long spri=
ngs and 4-1/4" for the short ones but invariably there is differences in the=
 resting length. After 50+ years of pushing you would tend to get tired. Whe=
n in overdrive, the springs are greatly depressed.&nbsp; That is asking a lo=
t for spiral metal to accomplish. So, yes they may look good, but have poor s=
tamina-oops, I just describe all of us. Hank<br><br><div></div><p>----------=
-------------------------------</p>From: "Bob Spidell" <u></u><br>To: <a hre=
f=3D"mailto:healeys@autox.team.net"; rel=3D"noreferrer" target=3D"_blank">hea=
leys@autox.team.net</a><br>Cc: <br>Sent: Friday August 11 2023 9:19:34PM<br>=
Subject: Re: [Healeys] Laycock overdrive<br><br>
re: "... The health of the 8 springs that keep the unit in direct
drive<br>
is important to keep the clutch from slipping...."<br><br>
I believe the shop manual admonishes owners to replace these
when<br>
overhauling the unit, even if the old ones look and feel fine (some
say<br>
not so). I think my old ones are in a box on a shelf somewhere
if<br>
anybody wants them.<br><br>
Note the O/D pump is a positive displacement pump that will
continue to<br>
produce pressure--driven by the full power of the engine--unless
there<br>
is a pressure relief mechanism.<br><br><br>
On 8/11/2023 10:34 AM, Hank Leach via Healeys wrote:<br>
&gt; Guys-this is a very lively topic and one of sometimes great
mystery<br>
&gt; and confusion.&nbsp; The unit is complex but the end result is
working well<br>
&gt; or not functioning at all.<br>
&gt;<br>
&gt; On the subject of pressure required to operate the shift
into<br>
&gt; overdrive there are many schools of thought. Some people
replace or<br>
&gt; stretch springs or add washers to increase the pressure
needed. The<br>
&gt; health of the 8 springs that keep the unit in direct drive
is<br>
&gt; important to keep the clutch from slipping.&nbsp; The pressure
supplied to<br>
&gt; overcome the strength of these 8 spring , and effect
overdrive, relies<br>
&gt; on adequate hydraulic pressure. The change from direct to
overdrive<br>
&gt; needs to be smooth, not harsh, and if pressures are high the
unit will<br>
&gt; snap into and out of OD rather than the smooth interchange we
are used<br>
&gt; to while driving.<br>
&gt;<br>
&gt; When applied to the Austin Healey 100, the Laycock overdrive
was<br>
&gt; initially a 32% reduction unit. It was soon found out in these
early<br>
&gt; Warwick cars that 32% was too much reduction.&nbsp; DHMC
swapped units<br>
&gt; three times in the original DMH tour car until they finally
found a<br>
&gt; combination that produced the smooth shift and complimentary
gearing<br>
&gt; desired.<br>
&gt;<br>
&gt; It is difficult, today, to find any information on this
original 32%<br>
&gt; gearbox, however if you examine the booklet (attached)
supplied by<br>
&gt; Laycock for the early cars, you will notice that the casting
allowed<br>
&gt; for a large accumulator piston (seen on p6 in brochure). After
some<br>
&gt; research and modified engineering, the company came up with
this alloy<br>
&gt; "sleeve" called the piston housing (photo) which partially
filled the<br>
&gt; chamber of the original large accumulator casting and allowed
for a<br>
&gt; smaller accumulator piston that we see in all the later 28%
reduction<br>
&gt; units. That size piston, in proper condition, produced from
350-450<br>
&gt; lbs of needed hydraulic pressure to overcome the springs
influence.<br>
&gt;<br>
&gt; I'm confident that the remark made by Geoff Healey in his
writings<br>
&gt; about the early transmissions "harsh shifting" revolved around
this<br>
&gt; huge accumulator piston producing too much pressure.
Additionally,<br>
&gt; there were three various accumulator springs supplied which
adjusted<br>
&gt; the pressure. The early boxes produced about 350lbs and the
later<br>
&gt; about 450.<br>
&gt;<br>
&gt; Today, Overdrive Spares supplies that sleeve housing with only
one<br>
&gt; rubber O-ring as it is basically a filler part and not under
extreme<br>
&gt; pressure. The accumulator piston within is under that
pressure. They<br>
&gt; supply a modified piston using O-ring technology. So, it is
not<br>
&gt; unusual to get good pressures over the normal 450 lbs
required. If it<br>
&gt; works well don't fix it.&nbsp; The only concern is if the
pressure does not<br>
&gt; release when overdrive is not called for. A clean unit, with
proper<br>
&gt; 30W oil, will allow that to happen. All this some old theory
and<br>
&gt; history to ponder. Hank<br>
&gt;<br><br>
_______________________________________________<br>
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