Digital peak torque dyno project

[ekd]

I am attempting to build a Peak Torque Dyno, for testing intact powerplants and motors using this torque adaptor.

Alltrade 940759 Powerbuilt Digital Torque Adaptor for 1/2-Inch Driver | eBay

To get useful numbers from this as a dyno, I believe I have to be able to apply the load (gradually, to stall) to a turning shaft. I'm thinking that testing with a solid connection will give varied results, depending on where the armature is, in reference to the magnets.

I'm currently considering a simple lever actuated clutch using a T-Maxx disc brake as the friction disc. Is there a better way?

I'd appreciate any input here.

[rangercat23]

Found this online, the last paragraph suits what you want to acheive. sounds like you just need to make an adapter from motor to torque device and bump the motor with a batt to find peak. if you do it off of a speed control since that will apply different voltages full throttle would show peak.


Machine torque:

Torque is part of the basic specification of an engine: the power output of an engine is expressed as its torque multiplied by its rotational speed of the axis. Internal-combustion engines produce useful torque only over a limited range of rotational speeds (typically from around 1,000–6,000 rpm for a small car). The varying torque output over that range can be measured with a dynamometer, and shown as a torque curve. The peak of that torque curve occurs somewhat below the overall power peak. The torque peak cannot, by definition, appear at higher rpm than the power peak.

Understanding the relationship between torque, power and engine speed is vital in automotive engineering, concerned as it is with transmitting power from the engine through the drive train to the wheels. Power is a function of torque and engine speed. The gearing of the drive train must be chosen appropriately to make the most of the motor's torque characteristics. Power at the drive wheels is equal to engine power less mechanical losses regardless of any gearing between the engine and drive wheels.

Steam engines and electric motors tend to produce maximum torque close to zero rpm, with the torque diminishing as rotational speed rises (due to increasing friction and other constraints). Reciprocating steam engines can start heavy loads from zero RPM without a clutch.

[ekd]

The readout is here, and I think I'll try a sleeve type coupler first.

The plan is to close the sleeve with hex screws, using ball end wrenches. It's the easiest way I can think of to do it without adding/detracting torque with the actuator.

These things have been independently tested, and found accurate within 1% (factory rated at 2%) down to 3.4 ft lbs. If it turns out it's needed for less, I'll set up a 10:1 torque multiplier (trans).

It is in line with other stuff, but I'll post progress here.

[rmdesignworks]

Originally Posted by ekd

The readout is here, and I think I'll try a sleeve type coupler first.

The plan is to close the sleeve with hex screws, using ball end wrenches. It's the easiest way I can think of to do it without adding/detracting torque with the actuator.

These things have been independently tested, and found accurate within 1% (factory rated at 2%) down to 3.4 ft lbs. If it turns out it's needed for less, I'll set up a 10:1 torque multiplier (trans).

It is in line with other stuff, but I'll post progress here.

Yeah you definitely want an inline coupling from the Motor/Trans/Axle to the adapter...if it requires a heavier load then a 1 pound weight including the weight arm holding it could be attached to the coupling parallel to the earth's surface..just deduct the 1 pound when giving test results.

[ekd]

To make this produce repeatable and consistent #s, I have to eliminate all potential variables. To this end, I'm considering running it with a car battery... to always supply more amps than any motor could draw.

I'm also thinking about setting up a concurrent peak amp readout. Any suggestions for a device for that?

[rangercat23]

would a car batt be to much juice???
12v is just a little more than a 3cell LiPo but what about the amps???

[losikid]

@rangercat (multi quotes arnt fun on a phone)

To begin with an speed control doesn't change the voltage. It simply pulses the full input voltage on and off really fast...longer the pulse, faster it'll go

Also a 3s lipo puts out 12.6 volts fully charged, so its equivalent to a car battery (voltage size) and amps are irrelevant the way you have it posted

@ekd- they sell watt meters that will record the current and/or peak current. I know hobbypartz sells one and there are better ones as well elsewhere

[ekd]

The motor will only draw the amps it is capable of using, and if there isn't an excess always available, the readings will only indicate the peak as limited by the power supply.

If needed, the battery can be tapped at the bridges between the cells, giving 1.5V increments... but, this is just for r/c, so I shouldn't need to. I'm hunting relative figures, for design purposes.

"...if it requires a heavier load then a 1 pound weight including the weight arm holding it could be attached to the coupling parallel to the earth's surface..just deduct the 1 pound when giving test results. " I should have mentioned that the readout is accurate to 150 ft lbs. There is only need for a clutch with the ability to stall any input to that level. A slipper sleeve clutch, as long as the tool tightening it doesn't add any forces as it's being cinched (hence the ball ended wrench), should be repeatable without undue time/motor heat problems.

To give an idea of the torque we're working with in r/c... 3.4 ft lbs is 40 in lbs... the rating of a quality cordless screwdriver. To accurately test motors alone will require the multiplier.

[ekd]

Originally Posted by losikid

@ekd- they sell watt meters that will record the current and/or peak current. I know hobbypartz sells one and there are better ones as well elsewhere

Thanks. I'll check it out.