Testing model engine power output question

SuperDave Thu Nov 07, 2013 10:18 am

To my knowledge there is no such thing as a model engine dynomometer.

I've used them to tune full-size outboard motors and cars but what of model engines?

Huh...

SD

roddie Thu Nov 07, 2013 10:23 am

Hey Dave, I started a thread on this awhile back... check it out. It's still been on my mind, to test a design that I've been thinking about.

https://www.coxengineforum.com/t5779-engine-thrust-meter?highlight=thrust+meter

SuperDave Thu Nov 07, 2013 11:03 am

Good on you Roddie! Isn't it wonderful to have an inquisitive mind?

Too many believe that power is best measured by RPM. Not so IMO.

Mention torque and many will ask: "What?" Hmmmm........

On large (150hp and larger) outboards I used a hyrdraulic dyno attached to the prop shaft. It consisted of an adjustable hydraulic pump. The output pressure of the pump could be adjusted simulating RPM and loading light to heavy. This is helpful in propeller selection.

If a similar dyno device could be adapated to model engines some interesting revealations would result and myths disproven.

SD

Mark Boesen Thu Nov 07, 2013 3:59 pm

SD,

Remember Horsepower is measured by RPM x torque ( HP=(RPM * T) / 5252) you gotta have both, but if two engines have the same amount of torque and one turns more RPM, then that engine is going to have more power or horsepower.

roddie Thu Nov 07, 2013 4:27 pm

SuperDave wrote:Good on you Roddie! Isn't it wonderful to have an inquisitive mind?

Too many believe that power is best measured by RPM. Not so IMO.

Mention torque and many will ask: "What?" Hmmmm........

On large (150hp and larger) outboards I used a hyrdraulic dyno attached to the prop shaft. It consisted of an adjustable hydraulic pump. The output pressure of the pump could be adjusted simulating RPM and loading light to heavy. This is helpful in propeller selection.

If a similar dyno device could be adapated to model engines some interesting revealations would result and myths disproven.

SD

Well Dave, to me; it's the challenge of building a very useful performance tuning tool... especially where there aren't any generally available. The toughest part is accurate calibration, and building a device that will accept different engines/mounting styles. The new digital fishing scales have great possibilities, along with a floating fixture for mounting the engine. A small shallow "water-tub" to float the fixture, with hooks for holding the scale would be "friction-free" (important with sm. less powerful motors) and give direct/accurate pull-measurements.

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