[Diy_efi] Strain gauge on engine mounts

[dh at busb.com]

Actually, you're quite wrong.  But instead of a simple desultory philllipic,
I shall elucidate.

Thing is there's no need for a strain gauge.  The motor mounts are elastic
and repeatable.  You only need a displacement sensor - say like the one on
the throttle position sensor connected to the engine block from the frame on
each side.  Increase the length of the lever from the sensor so that there
is adequate range of motion.  Connect the sensor to the frame.  Connect the
arm to the engine block (a custom bracket from an exhaust bolt should be
fine.)  I believe that one side should be adequate, but if not the same will
work in the other direction.  Remember that deceleration is a significant
torque (compression + friction)

An ordinary torque wrench can be used for calibration.

dh

----- Original Message ----- 
From: <niche at iinet.net.au>
To: <hugh at sol.co.uk>; <diy_efi at diy-efi.org>
Sent: Tuesday, April 19, 2005 11:22 AM
Subject: Re: [Diy_efi] Strain gauge on engine mounts


> This is by far the hardest way you could measure torque...
>
> Mike
>
>
> At 11:16 PM 19/04/05, you wrote:
> >Milosz,
> >
> >I have accelerometers on the vehicle as well, but the two axis
> >accelerometers will not resolve for bumps in the road / hills etc. A
three
> >axis accelerometer set-up might be better as it would resolve out the
> >unknowns.
> >
> >I beleive airbag accelerometers are very cheap to buy and might provide a
> >reasonable and complete solution.
> >
> >I also have a digital speed measurement which is easier to use, but also
> >does not allow for bumps in the road / hills etc.
> >
> >Thanks
> >
> >Hugh
> >
> >
> >Original Message:
> >-----------------
> >From: Milosz Kardasinski miloszk at gmail.com
> >Date: Tue, 19 Apr 2005 05:23:14 -0400
> >To: diy_efi at diy-efi.org
> >Subject: Re: [Diy_efi] Strain gauge on engine mounts
> >
> >
> >>Using one on each mounting point will, I hope, allow you to delete the
> >>effects of bumps in the road.
> >
> >It's a bit more complicated than that because the loading on your engine
> >mounts
> >is combined loading...axial, lateral, bending and torsion. Don't forget
that
> >strain
> >gauges have a temperature drift that you need to account for and lastly,
> >they are
> >fragile devices, when I played with them 10yrs ago you could break them
> >pretty
> >easily not to mention that it was a pain in the but to get them to bond
> >well.
> >
> >>Going over a bump, each strain gauge will be compressed by the weight of
> >>the engine, but the difference should I think still equal the engine
> >torque.
> >
> >Probably not, the reason is that I have seen very few engines that have
> >their
> >CG colinear with centerline, but you might be lucky something you have to
> >check. You'll have to figure what the weigh distribution is side to side
and
> >front to back if the mounts are not on the same plane.
> >
> >>There will obviously be calibration issues, but I am looking for a
tuning
> >>aid rather than a definitive torque number.
> >
> >Complicated way of going about it...but that shouldn't stop you. How
about
> >using an accelerometer instead? You could zero all the extra variables
> >introduced
> >by using systematic and methodical approach to your testing. A one axis
> >accelerometer
> >will give you acceleration, braking....with a 2-axis you could measure
your
> >lateral
> >accel (cornering) as well.
> >
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> 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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