A friend of mine has a 70 lb thrust trolling motor on his 16 foot boat. I think it should move his boat along great. The problem is that even on 5 it seems pretty slow. There's not much difference between 3 or 5. Is there a way to test and see how many pounds of thrust it actually puts out?

Not easy to test thrust.

If multiple speeds are the same, it's likely a speed coil problem.

The most useful test is to measure motor current with a clamp-on DC ammeter. If the draw is the same on multiple speeds, there is a problem.

Worth verifying that it is getting more than 25V to the motor. Easy to run one on 12V and think something is wrong with the motor.

I'd start with voltage at the trolling motor should be closer to 26volts than 25.

then across each battery in the back , perfect should be 13.2 but not realistic 12.8 is good.

then I'd check from battery 1negative to battery two positive should match what you found up on the bow, if this all checks out looking at measuring thrust, also if a trolling motor has a rheostat that controls how the power is applied/adjusted to the motor this part can be failing but still working.

When choosing motors and propellers for mini quad, we often just listen to rumours, or what&#;s suggested by the manufactures. To determine the optimal motor and propellers combination for your quadcopter and multirotors, the most scientific way is to test it yourself. I tried to look for a ready-made motor thrust measuring stand, most of them are either too heavy (made of metal), too expensive, or out of stock. Looks like it&#;s time for some DIY fun.

Goto Wing Flying to know more.

Test video at the end of post. For more quadcopter tools check out our list.

Simple Motor Thrust Test Stand Design

The trickiest part of this project was the design. Even with mini quad motors, such as or sizes can easily generate over 1KG of thrust on 4S. If the thrust stand is not well designed the result error can be large, and it can be dangerous if the stand is not stable with the fast spinning propellers. I went through quite a few usual thrust station designs, most of them has this common configuration. They all have relatively strong base to ensure stability (one of the reasons why many commercially available thrust stand are made of metal).

Basically, there are two wood pieces, the right angle arms, and the base. The two parts are connected by a hinge so the arms are movable. The motor is mounted on one arm, and as the motor drives forward, the other arm pushes against the scale to indicate thrust generated by the motor and propeller. It&#;s simple enough to build, but requires tools and material that I don&#;t have on hand (drill, wood pieces etc). So I did my usual thing, sketched random stuff on paper and finally I settled on two even more simple designs.

The first design is quite similar to the above example, only it would be using only one straight wood piece, and it works like a balance or seesaw. The disadvantage compared to previous design is that the motor/prop is too close to the ground, which affects aerodynamic and the thrust generated.

Second design is my favourite, it involves no moving parts (no pivots), and I am able to utilize material that is available to me, some ZMR250 spare arms, and some spacers. The thrust will be pointing downward, so in theory this thrust stand should be relatively stable, I just need to make sure there is enough friction between the bottom board and the scale. Drawbacks are again, it&#;s too close to some surface and affects accuracy (thrust generated), also the props size that can be tested is limited by the size of the arms (how far the spacers are from centre). But I am mainly going to test 5 inch and 6 inch propellers only, so that&#;s not a problem.

Of course you also need a watt meter for recording current / voltage as well, and a servo tester to control the ESC/motor speed.

Building DIY Thrust Stand

So once the design is done, the rest is easy and straight forward. Here are the material and parts used.

Find the centre of the base plywood board, and find out where we need to drills holes.

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I used a sharp knife and a pair of scissors for the job.

I glued the two arms together with Epoxy Glue. Once you fasten the motor on the arms, it also holds the two arms together firmly, so in theory you don&#;t even need to glue the arms together, but it&#;s more convenient to do so.

And I am happy with the result :D Added some foam at the bottom to make it a bit less slippery.

And finally tested it with a motor with watt meter, worked perfectly.

Here is a quick video showing the test:

Just another example :)

https://www.youtube.com/watch?v=LDu3Aww-koU

Accuracy?

Many are doubtful about how accurate this DIY gadget is. Some pointed out there is air flow issue as the propeller is so close to the bottom board. Indeed this is a issue that can affect final reading, and I did observe some inconsistency when measuring larger props on power setup.

I concluded that this thrust stand is good for measuring thrust range up to 500/600 grams. Anything larger than that, reading will be reduced than actual figure. I had pretty accurate reading with / motors with 5inch props, compared to manufacturer&#;s data.

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