TOPIC: Jetex type thrust rig.

Intriguing and way beyond my knowledge set, I note that there is a wide variation in the thrust each second, presumably due to the mixing of the propellant? What motor was that? The graph will be interesting.
A refinement we could have done with on earlier Rapiers would be a set of strain gauges to measure up and down and sideways thrust that would tell us how true the nozzles were or is that gilding the lilly?? Just thinking!
Clever stuff.

ahmetcalfe wrote: I note that there is a wide variation in the thrust each second, presumably due to the mixing of the propellant?
A refinement we could have done with on earlier Rapiers would be a set of strain gauges to measure up and down and sideways thrust that would tell us how true the nozzles were or is that gilding the lilly?? Just thinking!
Clever stuff.

Hello Howard, I think the second by second variation could be due to noise, my next attempt will take more readings per second and average them. This was a Tendera L2 with a 1.5mm nozzle.
Yes, I've provisioned for a second strain gauge in the vertical direction. I have a notion to do some measuring with tabs in the exhaust flow and the controller could accept a third on the remaining axis.

There is room for improvement in the basic system though. Mechanically it's a bit of a mess but when I've finished designing it I'll tidy it up! (he always says that, don't believe him!)

It certainly looks a potent motor easily equivalent or better than the best Rapier L2HP's and runs for longer too.

Well, let's just hope my calibration is about right!

I have some drills on order so I'll try some tests with 1.6 and 1.7mm nozzle.

You'll note also that we don't see a thrust build up. This is because the software waits until the thrust reaches a threshold value before logging starts. Maybe I'll change that so I can 'bump' start it logging and then we can see the thrust increase.

I also want to increase the logging rate to once per 0.2S and add the filtering/averaging I mentioned earlier.

Hi Terry,
this is good stuff. As a matter of (great) interest, how did you calibrate the apparatus? These figures are quite a bit higher than I measured.
Did you measure more than one motor?

But if your results are correct, this is indeed one helluva (too) powerful motor for most of my little jets!