Subject: [Healeys] Laycock overdrive

From: Hank Leach via Healeys <[email-masked]>
Date: Fri, 11 Aug 2023 17:34:46 +0000 boundary="=_b81e638730fccc491040b5bd10c8c1d6" Xu2GYBz8aaulOtvFU3ukq8KSwb+31MmsAqxon6YEC8tqQWHLGpDnm4RFW5HxRxmM7vE2JM6SoMxhkQ==

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Guys-this is a very lively topic and one of sometimes great mystery=0Aan=
d confusion. The unit is complex but the end result is working well=0Aor=
 not functioning at all.=0AOn the subject of pressure required to operat=
e the shift into=0Aoverdrive there are many schools of thought. Some peo=
ple replace or=0Astretch springs or add washers to increase the pressure=
 needed. The=0Ahealth of the 8 springs that keep the unit in direct driv=
e is=0Aimportant to keep the clutch from slipping. The pressure supplied=
 to=0Aovercome the strength of these 8 spring , and effect overdrive, re=
lies=0Aon adequate hydraulic pressure. The change from direct to overdri=
ve=0Aneeds to be smooth, not harsh, and if pressures are high the unit w=
ill=0Asnap into and out of OD rather than the smooth interchange we are=
 used=0Ato while driving.=0AWhen applied to the Austin Healey 100, the L=
aycock overdrive was=0Ainitially a 32% reduction unit. It was soon found=
 out in these early=0AWarwick cars that 32% was too much reduction. DHMC=
 swapped units three=0Atimes in the original DMH tour car until they fin=
ally found a=0Acombination that produced the smooth shift and compliment=
ary gearing=0Adesired.=0AIt is difficult, today, to find any information=
 on this original 32%=0Agearbox, however if you examine the booklet (att=
ached) supplied by=0ALaycock for the early cars, you will notice that th=
e casting allowed=0Afor a large accumulator piston (seen on p6 in brochu=
re). After some=0Aresearch and modified engineering, the company came up=
 with this alloy=0A"sleeve" called the piston housing (photo) which part=
ially filled the=0Achamber of the original large accumulator casting and=
 allowed for a=0Asmaller accumulator piston that we see in all the later=
 28% reduction=0Aunits. That size piston, in proper condition, produced=
 from 350-450=0Albs of needed hydraulic pressure to overcome the springs=
 influence.=0AI'm confident that the remark made by Geoff Healey in his=
 writings=0Aabout the early transmissions "harsh shifting" revolved arou=
nd this=0Ahuge accumulator piston producing too much pressure. Additiona=
lly,=0Athere were three various accumulator springs supplied which adjus=
ted=0Athe pressure. The early boxes produced about 350lbs and the later=
=0Aabout 450.=0AToday, Overdrive Spares supplies that sleeve housing wit=
h only one=0Arubber O-ring as it is basically a filler part and not unde=
r extreme=0Apressure. The accumulator piston within is under that pressu=
re. They=0Asupply a modified piston using O-ring technology. So, it is n=
ot=0Aunusual to get good pressures over the normal 450 lbs required. If=
 it=0Aworks well don't fix it. The only concern is if the pressure does=
 not=0Arelease when overdrive is not called for. A clean unit, with prop=
er=0A30W oil, will allow that to happen. All this some old theory and=0A=
history to ponder. Hank

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<html><body>Guys-this is a very lively topic and one of sometimes great=
 mystery and confusion.&nbsp; The unit is complex but the end result is=
 working well or not functioning at all.<div><br></div><div>On the subje=
ct of pressure required to operate the shift into overdrive there are ma=
ny schools of thought. Some people replace or stretch springs or add was=
hers to increase the pressure needed. The health of the 8 springs that k=
eep the unit in direct drive is important to keep the clutch from slippi=
ng.&nbsp; The pressure supplied to overcome the strength of these 8 spri=
ng , and effect overdrive, relies on adequate hydraulic pressure. The ch=
ange from direct to overdrive needs to be smooth, not harsh, and if pres=
sures are high the unit will snap into and out of OD rather than the smo=
oth interchange we are used to while driving.</div><div><br></div><div>W=
hen applied to the Austin Healey 100, the Laycock overdrive was initiall=
y a 32% reduction unit. It was soon found out in these early Warwick car=
s that 32% was too much reduction.&nbsp; DHMC swapped units three times=
 in the original DMH tour car until they finally found a combination tha=
t produced the smooth shift and complimentary gearing desired.</div><div=
><br></div><div>It is difficult, today, to find any information on this=
 original 32% gearbox, however if you examine the booklet (attached) sup=
plied by Laycock for the early cars, you will notice that the casting al=
lowed for a large accumulator piston (seen on p6 in brochure). After som=
e research and modified engineering, the company came up with this alloy=
 "sleeve" called the piston housing (photo) which partially filled the c=
hamber of the original large accumulator casting and allowed for a small=
er accumulator piston that we see in all the later 28% reduction units.=
 That size piston, in proper condition, produced from 350-450 lbs of nee=
ded hydraulic pressure to overcome the springs influence.</div><div><br>=
</div><div>I'm confident that the remark made by Geoff Healey in his wri=
tings about the early transmissions "harsh shifting" revolved around thi=
s huge accumulator piston producing too much pressure. Additionally, the=
re were three various accumulator springs supplied which adjusted the pr=
essure. The early boxes produced about 350lbs and the later about 450.</=
div><div><br></div><div>Today, Overdrive Spares supplies that sleeve hou=
sing with only one rubber O-ring as it is basically a filler part and no=
t under extreme pressure. The accumulator piston within is under that pr=
essure. 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.&nbsp; The only concern is if the pressure d=
oes not release when overdrive is not called for. A clean unit, with pro=
per 30W oil, will allow that to happen. All this some old theory and his=
tory to ponder. Hank</div></body></html>

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_______________________________________________

Archive: http://www.team.net/pipermail/healeys http://autox.team.net/archive/healeys

[email-masked]
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From: Hank Leach via Healeys <[email-masked]>
Date: Sat, 12 Aug 2023 16:40:10 +0000 boundary="=_8fedb783c929f1be4d943802d5436f8b" abC6Bs107XiBxvprgItm3r0bIDCgwp5pQoKIoWVmbs+E1p4JDG0yWWjNJSJs77qBk+4Vm9lFTgNHNBERPYY3K5ogtfaXqqCm6NY=

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Bob-good point. I just got a set of springs from Moss (from OD Spares=0A=
in UK, I imagine). The cost was $99 or about $12/spring which in the=0As=
cope of things is really not relevant. Holding that clutch in tight=0Aco=
ntact to the brake ring is paramount and just imagine the number of=0Ami=
les in direct drive that the car has experienced...many at high RPM.=0AT=
he other side of the brake for overdrive position is the "lazy side"=0Aa=
s the operating pistons under hydraulic pressure have plenty of clout=0A=
driving mostly steady RPMs. Yes, springs wear out.=0AI place them on the=
 bench and line up the lengths. They should measure=0A4-1/2" for the lon=
g springs and 4-1/4" for the short ones but=0Ainvariably there is differ=
ences in the resting length. After 50+ years=0Aof pushing you would tend=
 to get tired. When in overdrive, the springs=0Aare greatly depressed. T=
hat is asking a lot for spiral metal to=0Aaccomplish. So, yes they may l=
ook good, but have poor stamina-oops, I=0Ajust describe all of us. Hank=
=0A=0A=09-----------------------------------------From: "Bob Spidell"=
 =0ATo: [email-masked]=0ACc: =0ASent: Friday August 11 2023 9:19=
:34PM=0ASubject: Re: [Healeys] Laycock overdrive=0A=0A re: "... The heal=
th of the 8 springs that keep the unit in direct=0Adrive=0A is important=
 to keep the clutch from slipping...."=0A=0A I believe the shop manual a=
dmonishes owners to replace these when=0A overhauling the unit, even if=
 the old ones look and feel fine (some=0Asay=0A not so). I think my old=
 ones are in a box on a shelf somewhere if=0A anybody wants them.=0A=0A=
 Note the O/D pump is a positive displacement pump that will continue=0A=
to=0A produce pressure--driven by the full power of the engine--unless=
=0Athere=0A is a pressure relief mechanism.=0A=0A On 8/11/2023 10:34 AM,=
 Hank Leach via Healeys wrote:=0A > Guys-this is a very lively topic and=
 one of sometimes great mystery=0A > and confusion. The unit is complex=
 but the end result is working=0Awell=0A > or not functioning at all.=0A=
 >=0A > On the subject of pressure required to operate the shift into=0A=
 > overdrive there are many schools of thought. Some people replace or=
=0A > stretch springs or add washers to increase the pressure needed. Th=
e=0A > health of the 8 springs that keep the unit in direct drive is=0A=
 > important to keep the clutch from slipping. The pressure supplied=0At=
o=0A > overcome the strength of these 8 spring , and effect overdrive,=
=0Arelies=0A > on adequate hydraulic pressure. The change from direct to=
 overdrive=0A > needs to be smooth, not harsh, and if pressures are high=
 the unit=0Awill=0A > snap into and out of OD rather than the smooth int=
erchange we are=0Aused=0A > to while driving.=0A >=0A > When applied to=
 the Austin Healey 100, the Laycock overdrive was=0A > initially a 32% r=
eduction unit. It was soon found out in these=0Aearly=0A > Warwick cars=
 that 32% was too much reduction. DHMC swapped units=0A > three times in=
 the original DMH tour car until they finally found a=0A > combination t=
hat produced the smooth shift and complimentary=0Agearing=0A > desired.=
=0A >=0A > It is difficult, today, to find any information on this origi=
nal=0A32%=0A > gearbox, however if you examine the booklet (attached) su=
pplied by=0A > Laycock for the early cars, you will notice that the cast=
ing=0Aallowed=0A > for a large accumulator piston (seen on p6 in brochur=
e). After some=0A > research and modified engineering, the company came=
 up with this=0Aalloy=0A > "sleeve" called the piston housing (photo) wh=
ich partially filled=0Athe=0A > chamber of the original large accumulato=
r casting and allowed for a=0A > smaller accumulator piston that we see=
 in all the later 28%=0Areduction=0A > units. That size piston, in prope=
r condition, produced from 350-450=0A > lbs of needed hydraulic pressure=
 to overcome the springs influence.=0A >=0A > I'm confident that the rem=
ark made by Geoff Healey in his writings=0A > about the early transmissi=
ons "harsh shifting" revolved around this=0A > huge accumulator piston p=
roducing too much pressure. Additionally,=0A > there were three various=
 accumulator springs supplied which=0Aadjusted=0A > the pressure. The ea=
rly boxes produced about 350lbs and the later=0A > about 450.=0A >=0A >=
 Today, Overdrive Spares supplies that sleeve housing with only one=0A >=
 rubber O-ring as it is basically a filler part and not under=0Aextreme=
=0A > pressure. The accumulator piston within is under that pressure.=0A=
They=0A > supply a modified piston using O-ring technology. So, it is no=
t=0A > unusual to get good pressures over the normal 450 lbs required. I=
f=0Ait=0A > works well don't fix it. The only concern is if the pressure=
 does=0Anot=0A > release when overdrive is not called for. A clean unit,=
 with proper=0A > 30W oil, will allow that to happen. All this some old=
 theory and=0A > history to ponder. Hank=0A >=0A=0A ____________________=
___________________________=0A Support Team.Net http://www.team.net/dona=
te.html=0A /> Suggested annual donation $12.75=0A=0A Archive: http://www=
.team.net/pipermail/healeys [1]=0Ahttp://autox.team.net/archive/healeys=
=0A />=0A [email-masked]=0A http://autox.team.net/mailman/listin=
fo/healeys=0A />=0A Unsubscribe/Manage:=0Ahttp://autox.team.net/mailman/=
options/healeys/[email-masked]=0A />=0A =0A=0ALinks:=0A------=0A[1]=
 http://www.team.net/pipermail/healeys=0A

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<html><body>Bob-good point.&nbsp; I just got a set of springs from Moss=
 (from OD Spares in UK, I imagine). The cost was $99 or about $12/spring=
 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 n=
umber of miles in direct drive that the car has experienced...many at hi=
gh RPM. The other side of the brake for overdrive position is the "lazy=
 side" as the operating pistons under hydraulic pressure have plenty of=
 clout driving mostly steady RPMs. Yes, springs wear out.<div><br></div>=
<div>I place them on the bench and line up the lengths. They should meas=
ure 4-1/2" for the long springs and 4-1/4" for the short ones but invari=
ably there is differences in the resting length. After 50+ years of push=
ing you would tend to get tired. When in overdrive, the springs are grea=
tly depressed.&nbsp; That is asking a lot for spiral metal to accomplish=
. So, yes they may look good, but have poor stamina-oops, I just describ=
e all of us. Hank<br><br><div class=3D"reply-new-signature"></div><p>---=
--------------------------------------</p>From: "Bob Spidell" <bspidell@=
comcast.net><br>To: [email-masked]<br>Cc: <br>Sent: Friday Augus=
t 11 2023 9:19:34PM<br>Subject: Re: [Healeys] Laycock overdrive<br><br>=
=0Are: "... The health of the 8 springs that keep the unit in direct=0Ad=
rive<br>=0Ais important to keep the clutch from slipping...."<br><br>=0A=
I believe the shop manual admonishes owners to replace these=0Awhen<br>=
=0Aoverhauling the unit, even if the old ones look and feel fine (some=
=0Asay<br>=0Anot so). I think my old ones are in a box on a shelf somewh=
ere=0Aif<br>=0Aanybody wants them.<br><br>=0ANote the O/D pump is a posi=
tive displacement pump that will=0Acontinue to<br>=0Aproduce pressure--d=
riven by the full power of the engine--unless=0Athere<br>=0Ais a pressur=
e relief mechanism.<br><br><br>=0AOn 8/11/2023 10:34 AM, Hank Leach via=
 Healeys wrote:<br>=0A&gt; Guys-this is a very lively topic and one of s=
ometimes great=0Amystery<br>=0A&gt; and confusion.&nbsp; The unit is com=
plex but the end result is=0Aworking well<br>=0A&gt; or not functioning=
 at all.<br>=0A&gt;<br>=0A&gt; On the subject of pressure required to op=
erate the shift=0Ainto<br>=0A&gt; overdrive there are many schools of th=
ought. Some people=0Areplace or<br>=0A&gt; stretch springs or add washer=
s to increase the pressure=0Aneeded. The<br>=0A&gt; health of the 8 spri=
ngs that keep the unit in direct drive=0Ais<br>=0A&gt; important to keep=
 the clutch from slipping.&nbsp; The pressure=0Asupplied to<br>=0A&gt; o=
vercome the strength of these 8 spring , and effect=0Aoverdrive, relies<=
br>=0A&gt; on adequate hydraulic pressure. The change from direct to=0Ao=
verdrive<br>=0A&gt; needs to be smooth, not harsh, and if pressures are=
 high the=0Aunit will<br>=0A&gt; snap into and out of OD rather than the=
 smooth interchange we=0Aare used<br>=0A&gt; to while driving.<br>=0A&gt=
;<br>=0A&gt; When applied to the Austin Healey 100, the Laycock overdriv=
e=0Awas<br>=0A&gt; initially a 32% reduction unit. It was soon found out=
 in these=0Aearly<br>=0A&gt; Warwick cars that 32% was too much reductio=
n.&nbsp; DHMC=0Aswapped units<br>=0A&gt; three times in the original DMH=
 tour car until they finally=0Afound a<br>=0A&gt; combination that produ=
ced the smooth shift and complimentary=0Agearing<br>=0A&gt; desired.<br>=
=0A&gt;<br>=0A&gt; It is difficult, today, to find any information on th=
is=0Aoriginal 32%<br>=0A&gt; gearbox, however if you examine the booklet=
 (attached)=0Asupplied by<br>=0A&gt; Laycock for the early cars, you wil=
l notice that the casting=0Aallowed<br>=0A&gt; for a large accumulator p=
iston (seen on p6 in brochure). After=0Asome<br>=0A&gt; research and mod=
ified engineering, the company came up with=0Athis alloy<br>=0A&gt; "sle=
eve" called the piston housing (photo) which partially=0Afilled the<br>=
=0A&gt; chamber of the original large accumulator casting and allowed=0A=
for a<br>=0A&gt; smaller accumulator piston that we see in all the later=
 28%=0Areduction<br>=0A&gt; units. That size piston, in proper condition=
, produced from=0A350-450<br>=0A&gt; lbs of needed hydraulic pressure to=
 overcome the springs=0Ainfluence.<br>=0A&gt;<br>=0A&gt; I'm confident t=
hat the remark made by Geoff Healey in his=0Awritings<br>=0A&gt; about t=
he early transmissions "harsh shifting" revolved around=0Athis<br>=0A&gt=
; huge accumulator piston producing too much pressure.=0AAdditionally,<b=
r>=0A&gt; there were three various accumulator springs supplied which=0A=
adjusted<br>=0A&gt; the pressure. The early boxes produced about 350lbs=
 and the=0Alater<br>=0A&gt; about 450.<br>=0A&gt;<br>=0A&gt; Today, Over=
drive Spares supplies that sleeve housing with only=0Aone<br>=0A&gt; rub=
ber O-ring as it is basically a filler part and not under=0Aextreme<br>=
=0A&gt; pressure. The accumulator piston within is under that=0Apressure=
. They<br>=0A&gt; supply a modified piston using O-ring technology. So,=
 it is=0Anot<br>=0A&gt; unusual to get good pressures over the normal 45=
0 lbs=0Arequired. If it<br>=0A&gt; works well don't fix it.&nbsp; The on=
ly concern is if the=0Apressure does not<br>=0A&gt; release when overdri=
ve is not called for. A clean unit, with=0Aproper<br>=0A&gt; 30W oil, wi=
ll allow that to happen. All this some old theory=0Aand<br>=0A&gt; histo=
ry to ponder. Hank<br>=0A&gt;<br><br>=0A________________________________=
_______________<br>=0ASupport Team.Net <a href=3D"http://www.team.net/do=
nate.html%3Cbr">http://www.team.net/donate.html<br>=0A/&gt; Suggested an=
nual donation $12.75<br><br>=0AArchive:</a> <a href=3D"http://www.team.n=
et/pipermail/healeys">http://www.team.net/pipermail/healeys</a> <a href=
=3D"http://autox.team.net/archive/healeys%3Cbr">http://autox.team.net/ar=
chive/healeys<br>=0A/&gt;<br>=[email-masked]<br></a> <a href=
=3D"http://autox.team.net/mailman/listinfo/healeys%3Cbr">http://autox.te=
am.net/mailman/listinfo/healeys<br>=0A/&gt;<br>=0AUnsubscribe/Manage:</a=
> <a href=3D"http://autox.team.net/mailman/options/healeys/gradea1@chart=
er.net%3Cbr">http://autox.team.net/mailman/options/healeys/gradea1@chart=
er.net<br>=0A=0A/&gt;<br></a>=0A</[email-masked]></div></body></ht=
ml>

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[email-masked]

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From: Hank Leach via Healeys <[email-masked]>
Date: Sun, 13 Aug 2023 17:00:09 +0000 zuXfKMNWoHd3/v0zgd1i6rwUx5N5P+FPc0491/2IFlz4nPmAeknhyawUBs+KdujTSQX7z+EoOncpQ++xpm9KCX3VIzFQTiZS2AuInNjPdguhwMgNGY8plg6F 9dQ7rDQZYRScuMvw3xqbtQ==

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Guys-my thought on that is agreeing with both of you and additionally=0A=
I think the procedure for replacing the steel rings is very delicate=0Aa=
nd wasteful; if not careful, the rings will shatter. Slipping on an=0Ao-=
ring is much easier and less abrasive to the soft alloy body.=0ATo me, t=
he biggest "cost cutting measure" was by making the alloy=0Asleeve for t=
he smaller accumulator piston, they salvaged many=0Aon-the-shelf early c=
astings and did not have to modify the future=0Amolding of them to make=
 the piston area smaller. Only the Laycock=0Aengineers could explain it=
 now...from the grave. =0AA couple of reasons to replace the 8 springs:=
 they do not measure up,=0Aor if installed improperly, when previously r=
ebuilt, coil bound (bent)=0AHank=0A=0A=09-------------------------------=
----------From: "Michael Salter" =0ATo: "Bob Spidell"=0ACc: "Hank Leach"=
, "[email-masked]"=0ASent: Sunday August 13 2023 9:45:48AM=0ASub=
ject: Re: [Healeys] Laycock overdrive=0A=0A  Re: I think the fact Laycoc=
k went from steel rings on the operating=0Apistons to O-rings is telling=
  I would think that that was a cost=0Acutting measure. =0A=0A On Sat.,=
 Aug. 12, 2023, 7:34 p.m. Bob Spidell via Healeys,  wrote:=0A  I think t=
he fact Laycock went from steel rings on the operating=0Apistons to O-ri=
ngs is telling. Both will wear, but the steel rings=0Awill score the cyl=
inder.=0A=0AOn 8/12/2023 9:40 AM, Hank Leach wrote:=0A Bob-good point. I=
 just got a set of springs from Moss (from OD Spares=0Ain UK, I imagine)=
 The cost was $99 or about $12/spring which in the=0Ascope of things is=
 really not relevant. Holding that clutch in tight=0Acontact to the brak=
e ring is paramount and just imagine the number of=0Amiles in direct dri=
ve that the car has experienced...many at high RPM.=0AThe other side of=
 the brake for overdrive position is the "lazy side"=0Aas the operating=
 pistons under hydraulic pressure have plenty of clout=0Adriving mostly=
 steady RPMs. Yes, springs wear out. =0A I place them on the bench and l=
ine up the lengths. They should=0Ameasure 4-1/2" for the long springs an=
d 4-1/4" for the short ones but=0Ainvariably there is differences in the=
 resting length. After 50+ years=0Aof pushing you would tend to get tire=
d. When in overdrive, the springs=0Aare greatly depressed. That is askin=
g a lot for spiral metal to=0Aaccomplish. So, yes they may look good, bu=
t have poor stamina-oops, I=0Ajust describe all of us. Hank=0A=0A=09----=
------------------------------------- From: "Bob Spidell"=0A To: healeys=
@autox.team.net=0A Cc:=0A Sent: Friday August 11 2023 9:19:34PM=0A Subje=
ct: Re: [Healeys] Laycock overdrive=0A=0A re: "... The health of the 8 s=
prings that keep the unit in direct=0Adrive=0A is important to keep the=
 clutch from slipping...."=0A=0A I believe the shop manual admonishes ow=
ners to replace these when=0A overhauling the unit, even if the old ones=
 look and feel fine (some=0Asay=0A not so). I think my old ones are in a=
 box on a shelf somewhere if=0A anybody wants them.=0A=0A Note the O/D p=
ump is a positive displacement pump that will continue=0Ato=0A produce p=
ressure--driven by the full power of the engine--unless=0Athere=0A is a=
 pressure relief mechanism.=0A=0A On 8/11/2023 10:34 AM, Hank Leach via=
 Healeys wrote:=0A > Guys-this is a very lively topic and one of sometim=
es great mystery=0A > and confusion. The unit is complex but the end res=
ult is working=0Awell=0A > or not functioning at all.=0A >=0A > On the s=
ubject of pressure required to operate the shift into=0A > overdrive the=
re are many schools of thought. Some people replace or=0A > stretch spri=
ngs or add washers to increase the pressure needed. The=0A > health of t=
he 8 springs that keep the unit in direct drive is=0A > important to kee=
p the clutch from slipping. The pressure supplied=0Ato=0A > overcome the=
 strength of these 8 spring , and effect overdrive,=0Arelies=0A > on ade=
quate hydraulic pressure. The change from direct to overdrive=0A > needs=
 to be smooth, not harsh, and if pressures are high the unit=0Awill=0A >=
 snap into and out of OD rather than the smooth interchange we are=0Ause=
d=0A > to while driving.=0A >=0A > When applied to the Austin Healey 100=
, the Laycock overdrive was=0A > initially a 32% reduction unit. It was=
 soon found out in these=0Aearly=0A > Warwick cars that 32% was too much=
 reduction. DHMC swapped units=0A > three times in the original DMH tour=
 car until they finally found a=0A > combination that produced the smoot=
h shift and complimentary=0Agearing=0A > desired.=0A >=0A > It is diffic=
ult, today, to find any information on this original=0A32%=0A > gearbox,=
 however if you examine the booklet (attached) supplied by=0A > Laycock=
 for the early cars, you will notice that the casting=0Aallowed=0A > for=
 a large accumulator piston (seen on p6 in brochure). After some=0A > re=
search and modified engineering, the company came up with this=0Aalloy=
=0A > "sleeve" called the piston housing (photo) which partially filled=
=0Athe=0A > chamber of the original large accumulator casting and allowe=
d for a=0A > smaller accumulator piston that we see in all the later 28%=
=0Areduction=0A > units. That size piston, in proper condition, produced=
 from 350-450=0A > lbs of needed hydraulic pressure to overcome the spri=
ngs influence.=0A >=0A > I'm confident that the remark made by Geoff Hea=
ley in his writings=0A > about the early transmissions "harsh shifting"=
 revolved around this=0A > huge accumulator piston producing too much pr=
essure. Additionally,=0A > there were three various accumulator springs=
 supplied which=0Aadjusted=0A > the pressure. The early boxes produced a=
bout 350lbs and the later=0A > about 450.=0A >=0A > Today, Overdrive Spa=
res supplies that sleeve housing with only one=0A > rubber O-ring as it=
 is basically a filler part and not under=0Aextreme=0A > pressure. The a=
ccumulator piston within is under that pressure.=0AThey=0A > supply a mo=
dified piston using O-ring technology. So, it is not=0A > unusual to get=
 good pressures over the normal 450 lbs required. If=0Ait=0A > works wel=
l don't fix it. The only concern is if the pressure does=0Anot=0A > rele=
ase when overdrive is not called for. A clean unit, with proper=0A > 30W=
 oil, will allow that to happen. All this some old theory and=0A > histo=
ry to ponder. Hank=0A=0A _______________________________________________=
=0A Support Team.Net  [1]http://www.team.net/donate.html [2]=0A Suggeste=
d annual donation $12.75=0A=0A Archive:  [3]http://www.team.net/pipermai=
l/healeys [4] =0A[5]http://autox.team.net/archive/healeys [6]=0A=0AHeale=
[email-masked]=0A [7]http://autox.team.net/mailman/listinfo/healeys [=
8]=0A=0A Unsubscribe/Manage: =0A[9]http://autox.team.net/mailman/options=
/healeys/[email-masked]=0A[10]=0A=0A    =0A=0ALinks:=0A------=
=0A[1] http://www.team.net/donate.html=0A[2] http://www.team.net/donate.=
html=0A[3] http://www.team.net/pipermail/healeys=0A[4] http://www.team.n=
et/pipermail/healeys=0A[5] http://autox.team.net/archive/healeys=0A[6] h=
ttp://autox.team.net/archive/healeys=0A[7] http://autox.team.net/mailman=
/listinfo/healeys=0A[8] http://autox.team.net/mailman/listinfo/healeys=
=0A[9]=0Ahttp://autox.team.net/mailman/options/healeys/michaelsalter@gma=
il.com=0A[10]=0Ahttp://autox.team.net/mailman/options/healeys/michaelsal=
[email-masked]=0A

--=_58c0d00b408840181ad5a6fc891707d6
Content-Transfer-Encoding: quoted-printable

<html><body>Guys-my thought on that is agreeing with both of you and add=
itionally I think the procedure for replacing the steel rings is very de=
licate and wasteful; if not careful, the rings will shatter.&nbsp; Slipp=
ing on an o-ring is much easier and less abrasive to the soft alloy body=
<div><br></div><div>To me, the biggest "cost cutting measure" was by ma=
king the alloy sleeve for the smaller accumulator piston, they salvaged=
 many on-the-shelf early castings and did not have to modify the future=
 molding of them to make the piston area smaller. Only the Laycock engin=
eers could explain it now...from the grave.&nbsp;</div><div><br></div><d=
iv>A couple of reasons to replace the 8 springs: they do not measure up,=
 or if installed improperly, when previously rebuilt, coil bound (bent)=
 Hank<br><br><div class=3D"reply-new-signature"></div><p>---------------=
--------------------------</p>From: "Michael Salter" <michaelsalter@gmai=
l.com><br>To: "Bob Spidell"<br>Cc: "Hank Leach", "[email-masked]=
"<br>Sent: Sunday August 13 2023 9:45:48AM<br>Subject: Re: [Healeys] Lay=
cock overdrive<br><br>=0A<div>=0A<div>Re: <span style=3D"font-size:12.8p=
x;">I think the fact Laycock=0Awent from steel rings on the operating pi=
stons to O-rings is=0Atelling.&nbsp;</span></div>=0A<div>I would think t=
hat that was a cost cutting=0Ameasure.&nbsp;<span style=3D"font-size:12.=
8px;"><br></span></div>=0A<div><span style=3D"font-size:12.8px;"><br></s=
pan></div>=0A<div><span style=3D"font-size:12.8px;"><br></span><br><div=
 class=3D"gmail_quote">=0A<div dir=3D"ltr" class=3D"gmail_attr">On Sat.,=
 Aug. 12, 2023, 7:34 p.m.=0ABob Spidell via Healeys, &lt;<a>healeys@auto=
x.team.net</a>&gt; wrote:<br></div>=0A<blockquote class=3D"gmail_quote"=
 style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;=
">=0A<div>I think the fact Laycock went from steel rings on the=0Aoperat=
ing pistons to O-rings is telling. Both will wear, but the=0Asteel rings=
 will score the cylinder.<br><br><br><div>On 8/12/2023 9:40 AM, Hank Lea=
ch wrote:<br></div>=0A<blockquote>Bob-good point.&nbsp; I just got a set=
 of=0Asprings from Moss (from OD Spares in UK, I imagine). The cost was=
=0A$99 or about $12/spring which in the scope of things is really not=0A=
relevant. Holding that clutch in tight contact to the brake ring is=0Apa=
ramount and just imagine the number of miles in direct drive that=0Athe=
 car has experienced...many at high RPM. The other side of the=0Abrake f=
or overdrive position is the "lazy side" as the operating=0Apistons unde=
r hydraulic pressure have plenty of clout driving=0Amostly steady RPMs.=
 Yes, springs wear out.=0A<div><br></div>=0A<div>I place them on the ben=
ch and line up the lengths. They should=0Ameasure 4-1/2" for the long sp=
rings and 4-1/4" for the short ones=0Abut invariably there is difference=
s in the resting length. After=0A50+ years of pushing you would tend to=
 get tired. When in=0Aoverdrive, the springs are greatly depressed.&nbsp=
; That is asking=0Aa lot for spiral metal to accomplish. So, yes they ma=
y look good,=0Abut have poor stamina-oops, I just describe all of us. Ha=
nk<br><br><p>-----------------------------------------</p>=0AFrom: "Bob=
 Spidell"<br>=0ATo: <a>[email-masked]</a><br>=0ACc:<br>=0ASent:=
 Friday August 11 2023 9:19:34PM<br>=0ASubject: Re: [Healeys] Laycock ov=
erdrive<br><br>=0Are: "... The health of the 8 springs that keep the uni=
t in direct=0Adrive<br>=0Ais important to keep the clutch from slipping.=
.."<br><br>=0AI believe the shop manual admonishes owners to replace th=
ese=0Awhen<br>=0Aoverhauling the unit, even if the old ones look and fee=
l fine (some=0Asay<br>=0Anot so). I think my old ones are in a box on a=
 shelf somewhere=0Aif<br>=0Aanybody wants them.<br><br>=0ANote the O/D p=
ump is a positive displacement pump that will=0Acontinue to<br>=0Aproduc=
e pressure--driven by the full power of the engine--unless=0Athere<br>=
=0Ais a pressure relief mechanism.<br><br><br>=0AOn 8/11/2023 10:34 AM,=
 Hank Leach via Healeys wrote:<br>=0A&gt; Guys-this is a very lively top=
ic and one of sometimes great=0Amystery<br>=0A&gt; and confusion.&nbsp;=
 The unit is complex but the end result is=0Aworking well<br>=0A&gt; or=
 not functioning at all.<br>=0A&gt;<br>=0A&gt; On the subject of pressur=
e required to operate the shift=0Ainto<br>=0A&gt; overdrive there are ma=
ny schools of thought. Some people=0Areplace or<br>=0A&gt; stretch sprin=
gs or add washers to increase the pressure=0Aneeded. The<br>=0A&gt; heal=
th of the 8 springs that keep the unit in direct drive=0Ais<br>=0A&gt; i=
mportant to keep the clutch from slipping.&nbsp; The pressure=0Asupplied=
 to<br>=0A&gt; overcome the strength of these 8 spring , and effect=0Aov=
erdrive, relies<br>=0A&gt; on adequate hydraulic pressure. The change fr=
om direct to=0Aoverdrive<br>=0A&gt; needs to be smooth, not harsh, and i=
f pressures are high the=0Aunit will<br>=0A&gt; snap into and out of OD=
 rather than the smooth interchange we=0Aare used<br>=0A&gt; to while dr=
iving.<br>=0A&gt;<br>=0A&gt; When applied to the Austin Healey 100, the=
 Laycock overdrive=0Awas<br>=0A&gt; initially a 32% reduction unit. It w=
as soon found out in these=0Aearly<br>=0A&gt; Warwick cars that 32% was=
 too much reduction.&nbsp; DHMC=0Aswapped units<br>=0A&gt; three times i=
n the original DMH tour car until they finally=0Afound a<br>=0A&gt; comb=
ination that produced the smooth shift and complimentary=0Agearing<br>=
=0A&gt; desired.<br>=0A&gt;<br>=0A&gt; It is difficult, today, to find a=
ny information on this=0Aoriginal 32%<br>=0A&gt; gearbox, however if you=
 examine the booklet (attached)=0Asupplied by<br>=0A&gt; Laycock for the=
 early cars, you will notice that the casting=0Aallowed<br>=0A&gt; for a=
 large accumulator piston (seen on p6 in brochure). After=0Asome<br>=0A&=
gt; research and modified engineering, the company came up with=0Athis a=
lloy<br>=0A&gt; "sleeve" called the piston housing (photo) which partial=
ly=0Afilled the<br>=0A&gt; chamber of the original large accumulator cas=
ting and allowed=0Afor a<br>=0A&gt; smaller accumulator piston that we s=
ee in all the later 28%=0Areduction<br>=0A&gt; units. That size piston,=
 in proper condition, produced from=0A350-450<br>=0A&gt; lbs of needed h=
ydraulic pressure to overcome the springs=0Ainfluence.<br>=0A&gt;<br>=0A=
&gt; I'm confident that the remark made by Geoff Healey in his=0Awriting=
s<br>=0A&gt; about the early transmissions "harsh shifting" revolved aro=
und=0Athis<br>=0A&gt; huge accumulator piston producing too much pressur=
e.=0AAdditionally,<br>=0A&gt; there were three various accumulator sprin=
gs supplied which=0Aadjusted<br>=0A&gt; the pressure. The early boxes pr=
oduced about 350lbs and the=0Alater<br>=0A&gt; about 450.<br>=0A&gt;<br>=
=0A&gt; Today, Overdrive Spares supplies that sleeve housing with only=
=0Aone<br>=0A&gt; rubber O-ring as it is basically a filler part and not=
 under=0Aextreme<br>=0A&gt; pressure. The accumulator piston within is u=
nder that=0Apressure. They<br>=0A&gt; supply a modified piston using O-r=
ing technology. So, it is=0Anot<br>=0A&gt; unusual to get good pressures=
 over the normal 450 lbs=0Arequired. If it<br>=0A&gt; works well don't f=
ix it.&nbsp; The only concern is if the=0Apressure does not<br>=0A&gt; r=
elease when overdrive is not called for. A clean unit, with=0Aproper<br>=
=0A&gt; 30W oil, will allow that to happen. All this some old theory=0Aa=
nd<br>=0A&gt; history to ponder. Hank<br></div>=0A</blockquote>=0A<br></=
div>=0A_______________________________________________<br>=0ASupport Tea=
m.Net <a href=3D"http://www.team.net/donate.html"></a><a href=3D"http://=
www.team.net/donate.html">http://www.team.net/donate.html</a><br>=0ASugg=
ested annual donation&nbsp; $12.75<br><br>=0AArchive: <a href=3D"http://=
www.team.net/pipermail/healeys"></a><a href=3D"http://www.team.net/piper=
mail/healeys">http://www.team.net/pipermail/healeys</a> <a href=3D"http:=
//autox.team.net/archive/healeys"></a><a href=3D"http://autox.team.net/a=
rchive/healeys">http://autox.team.net/archive/healeys</a><br><br><a>Heal=
[email-masked]</a><br><a href=3D"http://autox.team.net/mailman/listi=
nfo/healeys"></a><a href=3D"http://autox.team.net/mailman/listinfo/heale=
ys">http://autox.team.net/mailman/listinfo/healeys</a><br><br>=0AUnsubsc=
ribe/Manage: <a href=3D"http://autox.team.net/mailman/options/healeys/mi=
[email-masked]"></a><a href=3D"http://autox.team.net/mailman/opti=
ons/healeys/[email-masked]">http://autox.team.net/mailman/optio=
ns/healeys/[email-masked]</a><br><br></blockquote>=0A</div>=0A<=
/div>=0A</div>=0A</[email-masked]></div></body></html>

--=_58c0d00b408840181ad5a6fc891707d6--

--===============0880942275432681079==
Content-Transfer-Encoding: 7bit
Content-Disposition: inline

[email-masked]

--===============0880942275432681079==--

---

From: Robert Parker via Healeys <[email-masked]>
Date: Sun, 13 Aug 2023 16:11:31 -0700

--===============0203875267597060283==
Content-Transfer-Encoding: 7bit

--Apple-Mail-661C72C0-4626-49DE-93FA-21D022AE6996
	charset=utf-8
Content-Transfer-Encoding: quoted-printable

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 <[email-masked]> 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: [email-masked]
>>> 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
>>> />
>>> />
>>> Unsubscribe/Manage: http://autox.team.net/mailman/options/healeys/gradea=
[email-masked]
>>> />
>>> 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
>>>=20
>>>=20
>>> Unsubscribe/Manage: http://autox.team.net/mailman/options/healeys/michae=
[email-masked]
>>>=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/arch=
ive/healeys
>>=20
>>=20
>> Unsubscribe/Manage: http://autox.team.net/mailman/options/healeys/roggrac=
[email-masked]
>>=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
>=20
> Unsubscribe/Manage: http://autox.team.net/mailman/options/healeys/rd_parke=
[email-masked]
>=20

--Apple-Mail-661C72C0-4626-49DE-93FA-21D022AE6996
	charset=utf-8
Content-Transfer-Encoding: quoted-printable

<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=
;[email-masked]&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=
&amp;utm_source=3Dlink&amp;utm_campaign=3Dsig-email&amp;utm_content=3Dwebmai=
l" target=3D"_blank"><img src=3D"https://s-install.avcdn.net/ipm/preview/ico=
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">[email-masked]</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:[email-masked]" target=3D"_blank">=
[email-masked]</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:[email-masked]" rel=3D"noreferrer" target=3D"_blank">hea=
[email-masked]</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>
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