THRUST RIG

[GRIM]

I have tried various methods to measure thrust , none of them “as yet” really work well ,
The photo shows something I am considering,

I have no intention of starting the great thrust rig argument up again, just would like some feedback to see if it is worth doing ,

Thanks
G

[hinote]

I have tried various methods to measure thrust , none of them “as yet” really work well ,
The photo shows something I am considering,

I have no intention of starting the great thrust rig argument up again, just would like some feedback to see if it is worth doing

Hi Grim:

I can assure you (and Mike E.) that I WON'T be participating in this thread!

I wish you the best of luck in this endeavor.

[Mike Everman]

I'll get into it.
Creative, Grim, but a water bucket is really cumbersome. can you get a fish scale? far easier, and a decent ball bearing drawer slide would do the trick, IMHO.

[larry cottrill]

Grim -

Just to be argumentataive, I'll go against Mike and encourage you to use MORE water! Ha.

Instead of the water-filled bottle, use a steel cylinder weighted to just float with its shoulder above the water in a larger cylindrical bucket. Epoxy a water-proof meter scale on the side of the cylindrical weight (or just make marks on the side with permanent marker as you calibrate it). You can pull on the cable with anything you think is accurate enough for calibration, and note the scale reading (or make a mark) at the water surface for, say, each 1/10 kg as the calibrating force lifts more and more of the cylinder above water. The water level will drop, of course, but that doesn't matter -- the force is represented by how far the weight is pulled above the water level at a particular moment in time. If the width of the flotation bath isn't much larger than the diameter of the cylinder, you won't get much wave action, and the measurement will be quite sensitive (due to the small volume of water).

Yes, I've suggested this a few times before, and as far as I know, nobody's tried it. Just an idea.

I really like the pontoons. No method is perfect, of course.

L Cottrill

[PyroJoe]

How about this one, just add weight until the jet is not able to push the slide upwards. Then cut the engine, fasten scales to front of jet and suspend.
Joe

[Mike Everman]

Cool, but Joe, surely to goodness and mercy they have fish scales in Texas, right?

[GRIM]

Gentlemen , thank you for the feedback ,

I am at the stage with these engines that I need to be able to measure thrust repeatably ,
I do not currently need accurate figures , wrt Lbs force,
Just the ability to determine wether thrust is increasing or decreasing with modifications,

someting like a dial test indicator , never accurate but a good reference ,

What I am currently using is very unstable ,
The “skid type” setup I was previously using, was better, but still not reliable,

I am concerned about the effects a spring type scale may have on the repeatability especially if the frequency changes ,

I intend to “hold fire” and see where Forrest takes his thread first,

Peace

G

[Fricke]

Hi there.

This is my go at the ultimate thrust stand... =) (According to me... *lol*)