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

Wed Apr 20 17:56:11 UTC 2005

Seems to me that the engine mounting rubbers will move in much the same way 
that the prop shaft will twist.

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?

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
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