[Diy_efi] RE: [offlist] Strain gauge on engine mounts

Wed Apr 20 18:08:51 UTC 2005

At 01:56 AM 21/04/05, you wrote:
>Seems to me that the engine mounting rubbers will move in much the same way that the prop shaft will twist.

No because they can only move a certain distance before things
can get fouled and rubber changes its properties over time,
esp temperature and humidity have high affect on spring properties,
I would imagine the shape of the curve ot torque vs deflection
would look like the BH curve of a transformer at the limits of
saturation...

>Why is the potentiometer / strain gauge from the inner wing to the engine cam / rocker cover not just as good and a whole lot simpler to read?

Maybe it is worht a try, though I'd think the repeatability given you'd
want to measure fairly small movements compounded by engine and
chassis vibrations at that point would be an interesting exercise in
filtering.

I'm really warming to the driveshaft scenario, much less to worry about,
I thought I had enough hobby projects already ;-)

Rgds

Mike

>Hugh
>
>
>----- Original Message ----- From: "Marc Reviel" <marc at powerlogix.com>
>To: <diy_efi at diy-efi.org>
>Sent: Wednesday, April 20, 2005 5:33 PM
>Subject: [Diy_efi] RE: [offlist] Strain gauge on engine mounts
>
>
>>One good thing about using rubber is it's easy to "calibrate" on the bench - just put a known torque on it and measure the twist. Not super-accurate, but probably get within a few % of actual. Can also correlate the torque curve of this to a real chassis dyno. I do think the same thing can be done replacing the rubber with the driveshaft. In any case, the only real challenge is getting the sensors rigidly mounted, and to where they float with any shaft/coupler movement.
>>
>>
>>-Marc
>>
>>
>>
>>At 11:03 PM +0800 4/20/05, niche at iinet.net.au wrote:
>>>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
>>>
>>>
>>>
>>>
>>>
>>>
>>>
>>>>Cheers
>>>>Rod
>>>>
>>>>-----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: Tuesday, April 19, 2005 11:13 AM
>>>>To: diy_efi at diy-efi.org
>>>>Subject: RE: [Diy_efi] Strain gauge on engine mounts
>>>>
>>>>
>>>>At 01:51 AM 20/04/05, you wrote:
>>>>>Anyone ever done or considered doing a simple DIY driveshaft torque design?
>>>>Heavy rubber coupler with two multi-toothed rings around each end, two
>>>>sensors mounted to display phase difference as torque increases?
>>>>
>>>>Now thats a good idea, far easier than the method in the link just posted,
>>>>probably be a lot cheaper too,  makes an inherent lot of sense, use an
>>>>all digital method  overall.
>>>>
>>>>There was a poster before who suggested something similar, use ABS
>>>>type pickup, think I misread that, thinking he was using only one, but of
>>>>course logical and clever to use two and look for phase difference.
>>>>
>>>>mmmm, Think I'll take a closer look under my car next chance I get
>>>>
>>>>Thanks for that,
>>>>
>>>>:o)
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>>>Dealing with nonlinearities of rubber engine mounts (amoung other
>>>>>>things) is asking for trouble (as in huge wasted time relearning
>>>>>>whats already been arrived at), far far more direct, efficient, effective
>>>>>>and less invasive to measure the twist of the tailshaft :o)
>>>>>>
>>>>>>Regards from
>>>>>>
>>>>>>
>>>>>>Mike Massen
>>>>>>Perth, Western Australia
>>>>>>VL Commodore Fuse Rail that wont warp or melt !
>>>>>>http://niche.iinet.net.au
>>>>>
>>>>>--
>>>>>Marc Reviel
>>>>>
>>>>>PowerLogix
>>>>>http://www.powerlogix.com
>>>>>_______________________________________________
>>>>
>>>>_______________________________________________
>>>>Diy_efi mailing list
>>>>Diy_efi at diy-efi.org
>>>>http://lists.diy-efi.org/mailman/listinfo/diy_efi
>>>
>>>Regards from
>>>
>>>
>>>Mike Massen
>>>Perth, Western Australia
>>>VL Commodore Fuse Rail that wont warp or melt !
>>>http://niche.iinet.net.au
>>>
>>>_______________________________________________
>>>Diy_efi mailing list
>>>Diy_efi at diy-efi.org
>>>http://lists.diy-efi.org/mailman/listinfo/diy_efi
>>
>>
>>-- 
>>Marc Reviel
>>
>>PowerLogix
>>http://www.powerlogix.com
>>_______________________________________________
>>Diy_efi mailing list
>>Diy_efi at diy-efi.org
>>http://lists.diy-efi.org/mailman/listinfo/diy_efi
>
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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