Test stand
 

Here is a stand that I build. It has a bar attached to the sled and it pulls on the scale.

http://www.quickclic.net/~wildrice/stand.jpg

Thrust Measuring Scale
 

very nice. I'm impressed! :cool:

Thrust Measuring Scale
 

Tommy,
Why use a pulley system to reverse the thrust to pull on the fishing scale, why not use a ballraced bellcrank from a helicopter ?

Boy, are we going to do some flying after the rains come !
BRG, David Gladwin

Thrust Measuring Scale
 

D.G.
Correct me if I have missed something. Just looked at bellcranks and most seem to have an insert between support bolt and the crank itself.
You bolt those things to a fixed suface, it there was no side load force why not just connect them with sticky tape?
When a line under load changes direction thru a fixed position the attachment comes under load. The load the turning fixture has to offset is directly related to the change of direction of the line.
Ding. I think I may have misinterperted your post. I'm sure the bell crank would work, but the thrust measured would have to adjusted for the change in angle also.
mikenlapaz

Thrust Measuring Scale
 

You have a very good point, I will try it on a test rig.
But if the bellcrank has a force on the pivot so will a pulley !
BRG, David Gladwin.

Thrust Measuring Scale
 

D.G.
Exactamente, we are almost on same wavelength! Refer to prior post on loads with change of angle of line.
On a bell crank other factors change. the angles of input and output change as well. More math than I can figure out tonite but I think principle remains the same as both angles change uniformly at least on a 90 degree bellcrank.

Where would you get the load on the scale if it were as pictured at about 90 degrees?? Would it not just load the bellcrank mounting bolt?

mikenlapaz

Thrust Measuring Scale
 

It's all getting a bit too hard. I think I will just fly the damn thing.!!! I am sure it will have plenty of power anyway.

I do know I have to hold the workmate with my foot to stop it tipping over at full throttle.!!!

test stand
 

You could also just buy a stand already built. They are not that expensive.
test stand post]