Load cell or ??

[Ralph Weaver]

I'd like to log the measurements from a motor thrust stand. Any thoughts on an easy and not too expensive way to get thrust measurements? I'm assuming some sort of analog output. Load cell? Strain gauge? Calibrated spring and linear pot?

[vintage1]

well ball raced arm and a digital scale (or the guts thereof) seems to be favorite.

[Ralph Weaver]

Right, but I want an output that I can automatically log to the computer. I want thrust as a line on the graph along with current, voltage and RPM.

[AndyKunz]

Get an electronic scale with serial interface. Put the motor on a tripod with a single "front" leg and two rear legs. The rear legs are hinged. The front leg rests on the scale. You need to do some calibration (and drawing of some vector diagrams) to determine thrust, but this will give it to you safely and accurately once you do the math.

You might even find several such thrust meters already in use.

Another option (I don't like it because of safety issues) is to make a mount stand with the motor in a sliding tray. The tray pulls a cable which is attached to a right-angle fulcrum - the other end of the fulcrum presses on the electronic scale.

E-mail me if you want me to send sketches.

Andy

[Ralph Weaver]

Thanks. Who carries scales with a serial interface?

[andrew b]

Thanks. Who carries scales with a serial interface?

All supermarkets and shops, need them to talk to the POS register.

[jeffs555]

Most of the scales with a computer interface are rather expensive. I haven't seen too many under $200. You have to watch out because some of the cheaper postal scales only use the interface to update postal rates, not readout the weight.

I did find this one on Ebay for $37 that does appear to readout through a USB interface. It only goes down to 0.2 oz increments. Don't know anything about it. http://cgi.ebay.com/50-USB-Postal-Digital-Scale-w-Software-1-00-Shipping_W0QQitemZ270117546290QQihZ017QQcategoryZ1 09762QQrdZ1QQssPageNameZWD1VQQcmdZViewItem

PS Here an RS232 scale that goes down to 1 gram. Again don't know anything about it. http://scalesusa.zoovy.com/product/ECS22D