[Diy_efi] measurement of tailshaft Twist

[Daniel R. Nicoson]

#2 Your right, this isn't a perfect solution for every vehicle
configuration.

#1 Again, not an easy solution, I'm still thinking.  On my BMW the
driveshaft leaving the transmission goes back to a stationary differential,
only movement is all the rubber mountings.  Relatively little movement.

On my Mustang, the driveshaft leaves the transmission and goes back to the
rear axle, lots of movement.

The only solution I could see would be a solid driveshaft running through a
larger diameter tube.  At each end of the tube would be bearings between the
tube and the solid drive shaft.  The toothed wheels would be inside the
tube, mounted on the solid driveshaft near each bearing.  The two sensors
would be mounted on the tube looking through a hole in the tube-wall at
their respective toothed wheel.  The tube would not rotate with the
driveshaft because there would be a linkage to the floor pan to hold it
steady from rotation.  But the tube would be otherwise free to move with the
driveshaft as the suspension requires.  The only relative movement between
sensors and toothed wheels would be the bearing tolerance, well within the
specs of the sensors.  The tube's main purpose is to hold the sensors
rigidly with respect to the driveshaft .  The tube would have no torque in
it so would keep the sensors rigid with respect to each other allowing one
to measure the twist of the shaft.

One possibility.

Dan Nicoson

  -----Original Message-----
  From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
Behalf Of Bill Washington
  Sent: Wednesday, April 20, 2005 10:12 PM
  To: diy_efi at diy-efi.org
  Subject: [Diy_efi] measurement of tailshaft Twist


  Gents,
      A couple of questions:
      1. How would you compensate for vertical and horizontal movement of
the tailshaft (due to engine movement) relative to the sensors? While it may
be small I believe it could generate much larger phase errors than the
signal that you are trying to measure.
      2. This method is only (possibly) suitable for rear wheel drive
vehicles with an exposed tailshaft - I do not see how it could be
implemented of front wheel drives (and even 4WDs where the torque is split
between two - front and rear -  driveshafts) or vehicles with enclosed
tailshafts (torque tubes).

      Thoughts???

  Regards
  Bill




-----Original Message-----
From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
Behalf Of niche at iinet.net.au
Sent: Wednesday, April 20, 2005 8:03 AM
To: diy_efi at diy-efi.org
Subject: [Diy_efi] RE: [offlist] Strain gauge on engine mounts


At 07:51 AM 20/04/05, you wrote:
  Not sure that is such a good idea Mike ... the rubber is non
linear ... just like the mounts would be, and resolving the
edges requires some very fast counters at high speed and
quite big counters at low speed ... plus who wants that much
slop in the drivetrain ... it's not like you can swap this
thing in and out all that easily is it?

Interesting point, think I misread this initially too, way too
many mailboxes here...

I think it should be possible to do this without any rubber,
and avoid any drivetrain slop and be fully differential
in respect of drivetrain lateral or even axial motion... !

I mean, consider this:-

a.   Toothed ring gear (pitch to be determined) on tail shaft
      close as possible to universal joint, firmly attached

b.   Second toothed ring gear as above but at furthest other
     end so max length of tailshaft between gears

c.   Tailshaft balanced appropriately

Question arises, would there be enough twist of the tailshaft
over the most appropriate length for the dynamic range of
torque measurement needed ?

ie. At lowest extreme the tailshaft twist may be so low that
there wont be much discernible phase shift for a coarse
pitch ring gear.
At highest extreme it may well skip a cycle if too fine pitch,
so a sync method would be needed if one is interested in
wide dynamic range - which obviously is fairly easy to implement...

Any mech structural engineers here care to estimate degrees
of twist for say 100 newton metres of torque over length of say
650mm and 80mm dia... ?


  Regards from


Mike Massen
Perth, Western Australia
VL Commodore Fuse Rail that wont warp or melt !
http://niche.iinet.net.au

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