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From: firstname.lastname@example.org (N. Thornton)
Subject: Re: Project (was: Help with relays please.)
Date: 28 Sep 2002 09:36:15 -0700
References: <email@example.com> <3D937DB8.B2320A30@boeing.com> <3D9461CE.331A960A@boeing.com>
NNTP-Posting-Date: 28 Sep 2002 16:36:16 GMT
Paul Hovnanian wrote in message news:
> "N. Thornton" wrote:
> > > This question leads me to dredge up an old idea for a project.
> > >
> > > A winch monitor, to read the motor winding temp., current,
> > > voltage and (using some strain guages) the winch load.
> > >
> > > I never did find a source of strain guages that could be incorporated
> > > into the mounting bolts of a winch. The stall rating on winches is
> > > anything from 8000 lbs to 15000 lbs.
> > >
> > > Any ideas for parts sources?
> > Anyone can make a strain gauge. Just make one direct on the mounting
> > hardware. Its only wire and glue. A differential one would be best.
> This is true. But a strain gauge actually measures deflection, so I'd
> be depending on the vehicles frame/bumper/winch bracket to have a
> linear and repeatable stress vs strain relationship.
Well I assume it would be steel, not aluminium. And you'd zero it each
time before reading - automatically without the user noticing. Would
> To be technically correct, what I need is called a load cell, which
> is (usually) a strain gauge incorporated into some structure with
> a predictable spring constant.
But the you'd have to modify the mountings.
> > Wouldnt it be easier though to measure winch current? Either approach
> > would need to be calibrated.
> I'd like to do that as well. But there are times that the winch
> is under load even when the motor is off (the brake is engaged)
> and I'd like to get a reading then as well. In addition, the
> dynamics of accelerating a mass with significant inertia might make
> the motor current to winch load a messy relationship.
Mmm. Your reading would soon settle though... maybe thats not good
enough for your app.
There is another way: run the steel rope through a small box that
picks up its resonant frequency, then you'd know the tension. You
wouldn't need to ping it, real life'd do that.
It'd be a little box with a roller at each side, you open the lid, put
it on the rope, and close. Now you have a fixed length of rope between
the 2 rollers, and a moving coil pickup will pickup the rope section's
I'm trying to think of something that would avoid the end customer
having to make their own strain gauge and know where to put it... that
would really kill sales! I dont think I've got it there... but you
might be able to go somewhere from that perhaps.
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