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

Marc Reviel marc
Wed Apr 20 17:55:51 UTC 2005


Sorry for not being clear. Yes, that's what I was talking about. If 
possible, all you'd need to do is remove the driveshaft and apply a 
known torque and measure.  It probably twists more than you think 
across that distance.

However, I don't think it's very critical on the pitch - almost any 
"convenient" number of teeth should work fine.  The only 
consideration is whether the applied torque *changed* between the 
sampling times of ring gear 1 and ring gear 2. Since the torque is 
relatively constant (certainly over the time each tooth goes by), and 
the entire ring gear is phase-shifted the same, it should be quite 
accurate. Again, I think the key to success for this is sensor 
coupling, dealing with run-out/wobble/movement of the driveshaft. 
Plus any movement of the sensors relative to each other would 
introduce potentially major error - that's one disadvantage of a 
longer distance.

(Hmm...maybe a laser pointed at teeth and detecting the 
reflection/back-scatter, or even precisely painted bars on the 
driveshaft itself?)

-Marc


At 1:18 AM +0800 4/21/05, niche at iinet.net.au wrote:
>mmm,
>
>I'm not quite sure I understand what u think I am getting at,
>
>I have a two part drive shaft, the bit from the end of automatic
>to center yoke is pretty well placed in transmission tunnel and
>doenst move around much. So I was thinking placing a ring
>gear on each end rigidly fixed to the drive shaft, the only piece
>of 'stuff' between the two ring gears is the driveshaft, no coupling,
>no rubber just hollow metal tube. Sure there wont be much twist
>of this tube at torque but there will be some, and what I'd like to
>know is just how much...so I can derive a ring gear pitch,
>
>Rgds
>
>mike
>
>
>
>
>
>
>At 12:33 AM 21/04/05, you wrote:
>  >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 Reviel

PowerLogix
http://www.powerlogix.com




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