Marc:
My speedo is an 1120 speedo, and I think that means 1120
revolutions per mile(?)
I think you are mixing up the drive gear and the pinion gear for
the speedo in my article. The 6 start gear is the DRIVE gear. The
smaller gear that drives the cable is the PINION gear. The standard
Volvo PINION is 21 tooth. The standard TR6 PINION is 20 (?) tooth. I
switched to an 18 tooth spitfire PINION gear.
Let's do a little math.
Since later TR6s used a seven start drive gear, and Volvo used a
6 start, then the speedo will read 6/7 x 100 = 85.7% of normal, or about
15% low which is exactly what I measured with highway mileage markers
and a stopwatch (Using the Volvo 21 tooth pinion gear).
To correct the low speedo readings, I went to a spitfire 18
tooth pinion gear, so the new speedo reading becomes:
(6/7) * (21/18) = 100%, which means that the speedo is now
accurate.
Marc, if you have an 1120 speedometer, and a 6 start speedo
drive gear, then use the spitfire overdrive 18 tooth pinion gear and
your speedometer will be correct.
Cheers,
Vance
-----Original Message-----
From: Marc Nederkoorn [mailto:adsl709847@tiscali.nl]
Sent: Sunday, February 19, 2006 12:19 PM
To: Navarrette, Vance; 6pack@autox.team.net
Subject: J-type OD questions....
Vance and listers,
I took apart the 2nd OD. This one, off a Volvo, looks much better and
will
be the one I will use. Some questions though:
Vance explains in his write-up (see his website) that a different Speedo
pinnion gear to match the Volvo speedo gear might be sufficient to
'recalibrate' the speedo. I am affraid this is only true for the post
CF35.000 TR6's. AFAIK Volvo used a 6-start speedo gear, post CF35.000
have a
7-start and all CF TR6's before that used the 8-start?
I am curious what the number on Vance's speedo is (input shaft turns,
bottom
of scale)?
(The difference between a 6- and a 8-start is too much, there is no such
thing as a15 tooth speedo pinion gear; possibilities are listed here,
incl.
other OD parts: http://www.overdrive-repairs.co.uk/spare_order_3.html)
Did all Volvo J-type's use the 6-start speedo gear?
And for the output flange: I 'think' I have the long Volvo flange. The
holes
do line up with the driving shaft flange. However, not perfectly. I
would
think there should be no difference?
I happen to have a real Triumph flange also, it does however need quite
a
bit of tydiing up (sandblast, polish, paint,...).
I hope the combined wisdom can shed some light, it will help me compose
a
shopping list!
(And an interesting one: after disassembly of the 2nd OD I found a
little
spring and a ball on the garage floor. I am very puzzled: It looks like
OD
parts but I did not drop anything, nor do I miss anything according to
the
exploded view and Nelson's write-up????? The Volvo OD's innards are
somewhat
different by the way. Should I lose any sleep over it...oh well, can
wait
'till assembly of the OD with loosing sleep!)
Regards to all,
Marc
'74 TR6 (CF 208..) & OD apprentice
|