Subject: Re: [Fot] Rear End Ratios

From: Larry Young <[email-masked]>
Date: Tue, 02 Jul 2013 15:01:08 -0500

That was with a close ratio gear set that has a high 1st gear and 
Hallett had one turn that is called "Stop and turn left".  Yeah, I did 
my first autocross in years in Waco last month with the street TR250.  
It's like Goldilocks and the Three Bears.  1st was too low, 2nd was too 
high, but 1st overdrive would have been just right. Maybe I will rewire 
the TR250 the same as the John's TR3.  There is a very simple way to 
wire them using only one switch on reverse.

On 7/2/2013 8:29 AM, [email-masked] wrote:
> In a message dated 07/01/2013 7:28:09 PM Central Daylight Time, 
> [email-masked] writes:
>
>
>> At
>> Hallett there is one very tight turn and with a close ratio gearbox,
>> first is too low and 2nd is too high but 1st overdrive is just right. 
>
>
> "Overdrive in 1st!"  What a concept.  Mike Belfer would be rolling 
> over in his grave to hear that.  He used to lecture me about not using 
> it in 2nd.  But it sure worked slick in traffic coming out of Turn 5 
> at Road America.
>
> My overdrive unit has been on the shelf for years now.  No longer 
> searching for faster laps.  Just trying to enjoy still being out there.
>
> Bill Dentinger
_______________________________________________
[email-masked]

http://www.fot-racing.com

Archive: http://www.team.net/archive

---

From: EDWARD BARNARD <[email-masked]>
Date: Tue, 2 Jul 2013 18:29:15 -0700 (PDT)

Larry:
I did the wiring through the reverse switch on Ray Josey's SpitSix. I
didn't have the special bracket used on GT6 trannies for the O/D switches so I
used the reverse as a disabler instead of the normal switches as enablers. It
does allow O/D in every forward gear. 
Get this...I built him a GT6 O/D tranny
I had sitting around the shop, then installed a 3.27/1 third member. He
cruises down the highway at 2000 - 2200 rpm. in 4th O/D
-Ed-
________________________________
 From: Larry Young <[email-masked]>
To:
[email-masked] 
Sent: Tuesday, July 2, 2013 3:01 PM
Subject: Re: [Fot]
Rear End Ratios

That was with a close ratio gear set that has a high 1st
gear and 
Hallett had one turn that is called "Stop and turn left".  Yeah, I
did 
my first autocross in years in Waco last month with the street TR250. 
It's like Goldilocks and the Three Bears.  1st was too low, 2nd was too 
high,
but 1st overdrive would have been just right. Maybe I will rewire 
the TR250
the same as the John's TR3.  There is a very simple way to 
wire them using
only one switch on reverse.

On 7/2/2013 8:29 AM, [email-masked] wrote:
_______________________________________________
[email-masked]
http://www.fot-racing.com/

Archive:
http://autox.team.net/mailman/options/fot/[email-masked]
_______________________________________________
[email-masked]

---

From: TR4 Tony <[email-masked]>
Date: Wed, 3 Jul 2013 10:10:50 +0100

Hi again fellas

You need to be aware that using overdrive in 1st gear with an a type unit will
give it a very short life.

Apart from the fact that you will cane the hell out of the bearings as you
load up on exit, the less obvious issue is the rear bearing set in the a type
unit, which is rated to about 9000 rpm.

This bearing set runs at 3 times engine speed. So do the maths, but in a 6000
rpm max engine, it's double the designed load rate on those bearings. With a
steel crank and 8500 rpm plus it's nearly 3 times. I regularly run upwards of
6000 rpm.

If you run at full revs in any gear for any pronged time this bearing seizes
and the overdrive cooks, and using it on first gets it to that failure point
very quickly. its worth remembering that the inside of the overdrive does not
recover coolness very easily as its snuck up inside the car, so the heat issue
is cumulative - ie once it gets hot it stays hot and the heat builds. I've had
my gearbox so hot after a half hour rest on a rally that it was a gloves on
job to check the oil level and the forward UJ on the prop.

The answers are firstly a higher rated bearing set to deal with those extra
revs (and by that I mean larger individual bearings with bigger gaps between
them for the oil to flow through and get that cooling done), secondly and / or
a gearbox oil cooler.

I was getting about 200 miles running out of an a type because of this revs
issue, firstly manifesting itself in the speedo drive melting like wax on a
stick (so both my speed and tripmeter failed - which is what alerted me to the
problem)  and secondly by the cage round the bearing melting and causing the
unit to seize (oh and the smell and racket wasn't great either) - the first
time the gearbox and overdrive unit were scrap, the second I was a little more
clued up and got it back to base intact, albeit utterly knackered.

So, if you do plan to use OD on first in an a type certainly, do make sure the
unit is suitably uprated otherwise you'll be taking it out again shortly
afterwards.

Regards

Tony

Sent from my iPhone

On 2 Jul 2013, at 21:01, Larry Young <[email-masked]> wrote:

> Donate: http://www.team.net/donate.html
> Forums: http://www.team.net/forums
> Unsubscribe/Manage:
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---

From: Larry Young <[email-masked]>
Date: Wed, 03 Jul 2013 17:47:07 -0500

I did not follow your logic concerning the overdrive bearings.  Are you 
referring the the two rear bearings that support the annulus and turn at 
drive shaft speed?  They will be turning slower when overdrive is engaged.

We used our A type for most of the 6 years we raced the car. Ours also 
had the large accumulator shimmed to about 525 psi.  We found it to be 
very stout and relatively trouble free despite the abuse. Our only 
problem with it was a broken circlip costing about $1.  On the rare 
occasions we used 1st overdrive, it was with a close ratio gear set 
where 1st is nearly as high as 2nd in a normal gear set.  I have no 
explanation for why our experiences differ.  Perhaps others will 
comment.  Tony Drews?

On 7/3/2013 4:10 AM, TR4 Tony wrote:
> Hi again fellas
>
> You need to be aware that using overdrive in 1st gear with an a type unit will give it a very short life.
>
> Apart from the fact that you will cane the hell out of the bearings as you load up on exit, the less obvious issue is the rear bearing set in the a type unit, which is rated to about 9000 rpm.
>
> This bearing set runs at 3 times engine speed. So do the maths, but in a 6000 rpm max engine, it's double the designed load rate on those bearings. With a steel crank and 8500 rpm plus it's nearly 3 times. I regularly run upwards of 6000 rpm.
>
> If you run at full revs in any gear for any pronged time this bearing seizes and the overdrive cooks, and using it on first gets it to that failure point very quickly. its worth remembering that the inside of the overdrive does not recover coolness very easily as its snuck up inside the car, so the heat issue is cumulative - ie once it gets hot it stays hot and the heat builds. I've had my gearbox so hot after a half hour rest on a rally that it was a gloves on job to check the oil level and the forward UJ on the prop.
>
> The answers are firstly a higher rated bearing set to deal with those extra revs (and by that I mean larger individual bearings with bigger gaps between them for the oil to flow through and get that cooling done), secondly and / or a gearbox oil cooler.
> W
> I was getting about 200 miles running out of an a type because of this revs issue, firstly manifesting itself in the speedo drive melting like wax on a stick (so both my speed and tripmeter failed - which is what alerted me to the problem)  and secondly by the cage round the bearing melting and causing the unit to seize (oh and the smell and racket wasn't great either) - the first time the gearbox and overdrive unit were scrap, the second I was a little more clued up and got it back to base intact, albeit utterly knackered.
>
> So, if you do plan to use OD on first in an a type certainly, do make sure the unit is suitably uprated otherwise you'll be taking it out again shortly afterwards.
>
> Regards
>
> Tony
>
> Sent from my iPhone
>
>> Unsubscribe/Manage: http://autox.team.net/mailman/options/fot/[email-masked]

---

From: Larry Young <[email-masked]>
Date: Wed, 03 Jul 2013 18:05:57 -0500

Ed,
Your wiring sounds similar to what I used.  I used a commodity SPDT 
Bosch relay with the overdrive solenoid connected to the normally closed 
contact.  The switches were wired in parallel so that the overdrive 
works when all switches are off.

And you get this.... I just recently installed a J-type overdrive in my 
Model T boat tail speedster - very slick.  It goes about 55mph at 2000 
and I don't care to go much faster.
Larry

On 7/2/2013 8:29 PM, EDWARD BARNARD wrote:
> didn't have the special bracket used on GT6 trannies for the O/D 
> switches so I used the reverse as a disabler instead of the normal 
> switches as enablers. It does allow O/D in every forward gear.
> Get this...I built him a GT6 O/D tranny I had sitting around the shop, 
> then installed a 3.27/1 third member. He cruises down the highway at 
> 2000 - 2200 rpm. in 4th O/D
> -Ed-

---

From: EDWARD BARNARD <[email-masked]>
Date: Wed, 3 Jul 2013 20:34:52 -0700 (PDT)

Yes, that is exactly how I did Ray's O/D. I like to use the term enabler or
disabler because it makes it easier for people to understand how the switches
are actually working. The five terminal generic relay does the trick great,
but I am like you and prefer to use a Bosch one for better reliability over
the $4.95 Chinese ones
I can't wait to see the Speedster.
-Ed-
________________________________
 From: Larry Young <[email-masked]>
To:
EDWARD BARNARD <[email-masked]> 
Cc: "[email-masked]"
<[email-masked]> 
Sent: Wednesday, July 3, 2013 6:05 PM
Subject: Re: [Fot]
Rear End Ratios

Ed,
Your wiring sounds similar to what I used.  I used a
commodity SPDT
    Bosch relay with the overdrive solenoid connected to the
normally
    closed contact.  The switches were wired in parallel so that the
overdrive works when all switches are off. 

And you get this.... I just
recently installed a J-type overdrive in
    my Model T boat tail speedster -
very slick.  It goes about 55mph at
    2000 and I don't care to go much
faster.
Larry

Larry: 
>I did
the wiring through the reverse switch on Ray Josey's SpitSix. I didn't have
the special bracket used on GT6 trannies for the O/D switches so I used the
reverse as a disabler instead of the normal switches as enablers. It does
allow O/D in every forward gear.  
>Get this...I built him a GT6 O/D tranny I
had sitting around the shop, then installed a 3.27/1 third member. He cruises
down the highway at 2000 - 2200 rpm. in 4th O/D

---

From: Tony Drews <[email-masked]>
Date: Wed, 03 Jul 2013 23:37:20 -0500

I'm interested in which bearing(s) this refers to.  I've been beating 
the heck out of an A-type for 10 years now.  I did manage to frag the 
one way clutch arrangement by loading the driveline with rear lockup 
and a detroit locker (which is quite a jarring thing to experience - 
I thought someone hit me).  Didn't know I had a problem with the OD 
until I changed the oil and significantly sized chunks came out with 
the oil.  I do use 2nd OD semi-frequently although lately I've been 
more prone to lug it in 3rd and be able to skip the time-wasting 
shift from 2nd OD to 3rd.  It's normally on just one corner per lap 
that 2nd OD is the "perfect" gear (turn 5 at Road America, 3A at 
Blackhawk, the hard right entry to the esses at VIR).  But, I don't 
run for more than 30 minutes at a stretch and normally only about 20 
minutes of that is under full race conditions so I may be allowing 
enough heat to dissipate before bad things start to occur.  I know 
the driveshaft tunnel is uncomfortably hot after a 30 min session on 
a hot day, so I would imagine that the Tranny and OD are pretty 
toasty by then.  I also generally shift at 6000 even though I have 
the good crank / rods / etc. so that may help.

Is there some sort of beefed up bearing arrangement that can be implemented?

I'll need to look at the exploded diagram again to better understand 
this one.  Maybe it's the bearings in the planetary gears?  Those 
seem small and would be spinning pretty quickly...

Tony Drews

At 05:47 PM 7/3/2013, Larry Young wrote:
>I did not follow your logic concerning the overdrive bearings.  Are 
>you referring the the two rear bearings that support the annulus and 
>turn at drive shaft speed?  They will be turning slower when 
>overdrive is engaged.
>
>We used our A type for most of the 6 years we raced the car. Ours 
>also had the large accumulator shimmed to about 525 psi.  We found 
>it to be very stout and relatively trouble free despite the abuse. 
>Our only problem with it was a broken circlip costing about $1.  On 
>the rare occasions we used 1st overdrive, it was with a close ratio 
>gear set where 1st is nearly as high as 2nd in a normal gear set.  I 
>have no explanation for why our experiences differ.  Perhaps others 
>will comment.  Tony Drews?
>
>
>>You need to be aware that using overdrive in 1st gear with an a 
>>type unit will give it a very short life.
>>
>>Apart from the fact that you will cane the hell out of the bearings 
>>as you load up on exit, the less obvious issue is the rear bearing 
>>set in the a type unit, which is rated to about 9000 rpm.
>>
>>This bearing set runs at 3 times engine speed. So do the maths, but 
>>in a 6000 rpm max engine, it's double the designed load rate on 
>>those bearings. With a steel crank and 8500 rpm plus it's nearly 3 
>>times. I regularly run upwards of 6000 rpm.
>>
>>If you run at full revs in any gear for any pronged time this 
>>bearing seizes and the overdrive cooks, and using it on first gets 
>>it to that failure point very quickly. its worth remembering that 
>>the inside of the overdrive does not recover coolness very easily 
>>as its snuck up inside the car, so the heat issue is cumulative - 
>>ie once it gets hot it stays hot and the heat builds. I've had my 
>>gearbox so hot after a half hour rest on a rally that it was a 
>>gloves on job to check the oil level and the forward UJ on the prop.
>>
>>The answers are firstly a higher rated bearing set to deal with 
>>those extra revs (and by that I mean larger individual bearings 
>>with bigger gaps between them for the oil to flow through and get 
>>that cooling done), secondly and / or a gearbox oil cooler.
>>W
>>I was getting about 200 miles running out of an a type because of 
>>this revs issue, firstly manifesting itself in the speedo drive 
>>melting like wax on a stick (so both my speed and tripmeter failed 
>>- which is what alerted me to the problem)  and secondly by the 
>>cage round the bearing melting and causing the unit to seize (oh 
>>and the smell and racket wasn't great either) - the first time the 
>>gearbox and overdrive unit were scrap, the second I was a little 
>>more clued up and got it back to base intact, albeit utterly knackered.
>>
>>So, if you do plan to use OD on first in an a type certainly, do 
>>make sure the unit is suitably uprated otherwise you'll be taking 
>>it out again shortly afterwards.
>>
>>Regards
>>
>>Tony
>>
>>Sent from my iPhone
<snip>

---

From: TR4 Tony <[email-masked]>
Date: Thu, 4 Jul 2013 10:19:12 +0100

Hi both

This issue relates to the bearing in the epicyclic gear (around which the
three planet gears spin) - which therefore runs at three times engine speed.

The mainshaft bearings are not such a problem, although using a high first and
hefty revs shortens their life too as the shaft bends in the casing, which is
weak. You'll see a series of failures recently with those using dog gear sets
rather than the gentler engaging bevel sets as the shafts push apart bending
and cracking the main segment of the casing - this is even happening with the
late TR 6 cases which are the strongest.

In the case of the overdrive bearings It may not be happening because you're
not running for long periods of time - remember that I'm running for 4 to 6
hours at a stretch with out a break.

Peter Eggington at Overdrive Repair Services can supply these S78 bearings at
modest cost, so it's not a big money fix. If you talk to him on the phone he
remembers this failure particularly as I have him the mess to post mortem as I
didn't know where to start.

Regards

Tony

Sent from my iPhone

On 4 Jul 2013, at 05:37, Tony Drews <[email-masked]> wrote:

> I'm interested in which bearing(s) this refers to.  I've been beating the
heck out of an A-type for 10 years now.  I did manage to frag the one way
clutch arrangement by loading the driveline with rear lockup and a detroit
locker (which is quite a jarring thing to experience - I thought someone hit
me).  Didn't know I had a problem with the OD until I changed the oil and
significantly sized chunks came out with the oil.  I do use 2nd OD
semi-frequently although lately I've been more prone to lug it in 3rd and be
able to skip the time-wasting shift from 2nd OD to 3rd.  It's normally on just
one corner per lap that 2nd OD is the "perfect" gear (turn 5 at Road America,
3A at Blackhawk, the hard right entry to the esses at VIR).  But, I don't run
for more than 30 minutes at a stretch and normally only about 20 minutes of
that is under full race conditions so I may be allowing enough heat to
dissipate before bad things start to occur.  I know the driveshaft tunnel is
uncomfortably hot after a 30 min session on a hot day, so I would imagine that
the Tranny and OD are pretty toasty by then.  I also generally shift at 6000
even though I have the good crank / rods / etc. so that may help.
> I'll need to look at the exploded diagram again to better understand this
one.  Maybe it's the bearings in the planetary gears?  Those seem small and
would be spinning pretty quickly...
>> I did not follow your logic concerning the overdrive bearings.  Are you
referring the the two rear bearings that support the annulus and turn at drive
shaft speed?  They will be turning slower when overdrive is engaged.
>>
>> We used our A type for most of the 6 years we raced the car. Ours also had
the large accumulator shimmed to about 525 psi.  We found it to be very stout
and relatively trouble free despite the abuse. Our only problem with it was a
broken circlip costing about $1.  On the rare occasions we used 1st overdrive,
it was with a close ratio gear set where 1st is nearly as high as 2nd in a
normal gear set.  I have no explanation for why our experiences differ.
Perhaps others will comment.  Tony Drews?
>>>
>>> This bearing set runs at 3 times engine speed. So do the maths, but in a
6000 rpm max engine, it's double the designed load rate on those bearings.
With a steel crank and 8500 rpm plus it's nearly 3 times. I regularly run
upwards of 6000 rpm.
>>>
>>> If you run at full revs in any gear for any pronged time this bearing
seizes and the overdrive cooks, and using it on first gets it to that failure
point very quickly. its worth remembering that the inside of the overdrive
does not recover coolness very easily as its snuck up inside the car, so the
heat issue is cumulative - ie once it gets hot it stays hot and the heat
builds. I've had my gearbox so hot after a half hour rest on a rally that it
was a gloves on job to check the oil level and the forward UJ on the prop.
>>>
>>> The answers are firstly a higher rated bearing set to deal with those
extra revs (and by that I mean larger individual bearings with bigger gaps
between them for the oil to flow through and get that cooling done), secondly
and / or a gearbox oil cooler.
>>> W
>>> I was getting about 200 miles running out of an a type because of this
revs issue, firstly manifesting itself in the speedo drive melting like wax on
a stick (so both my speed and tripmeter failed - which is what alerted me to
the problem)  and secondly by the cage round the bearing melting and causing
the unit to seize (oh and the smell and racket wasn't great either) - the
first time the gearbox and overdrive unit were scrap, the second I was a
little more clued up and got it back to base intact, albeit utterly
knackered.
>>>
>>> So, if you do plan to use OD on first in an a type certainly, do make sure
the unit is suitably uprated otherwise you'll be taking it out again shortly
afterwards.