2015

Item 2015

DESIGN: Electrotor-SloMo ~ Special Tool - Test Stand - Dynamometer II

Overview:

To test an individual motor and rotor.

Data to be Acquired;

Input;

Voltage
Amperage

Output;

RPM
Torque
Blade Pitch
Thrust
Coil temperature differential from ambient.

There are two braking devices; the aerodynamic rotor and the wheel brake &/or water brake.
There is only one source of power input; the electric motor.
This information will go in to Access - Motor to be used in evaluating the optimum RPM for the combined motor & rotor efficiency etc.

Questions and Requirements to be done:

Can the existing Test Bench I be used for any further testing?

How is thrust from blades to be measured?

Should the brake drum be uncoupable from the rotorhead so that its rotational inertia will not effect torque-pitch-rpm testing and its weight not detract from the recorded thrust.?

The RPM sensor must read the rotorhead.

Could the plastic female splines be used initially for one of both ends of the shaft?

Consider using cable(s) and weights for initial torque calculations. Eventually the requirement will be to read +100 ft-lb of torque.

Thoughts:

Consider making a four leg base for a single rotor etc. where the elevation is around 36" and the legs slope outward.

The widened leg would be cross braced at the bottom and this cross bracing would support the batteries etc. The 'h' beam might be part of the X-bracing or table for batteries, while adding additional weight.

For aerodynamic testing with blades installed this 4-legged 'table' could be located on leg extenders that increase to rotors elevation to perhaps 10 feet or more. The weights (batteries etc.) and more would be placed on cross bracing at the based of this elevated test stand.

Comparative evaluations of the different configurations would be done well into the future.

Concerns:

Will the mechanical brake hold a constant braking force for a desired period of time, or will the heating of the drum and linings change the force?

Drawing:

Note that on the lower (and simpler) alternative drawing above, the braking is still applied to the aero-rotorhub. Therefore, short stub shafts with a marker can be substituted for the blades to show what the pitch will be for a given torque and RPM is. Unfortunately, this braking is not the same as the induced and profile drag of the actual blades at this pitch.

The Intermeshing frame must be strong enough to handle the flight conditions plus a Safety Factor. This means that this frame can be the test-stand by attaching its 3 tripod leg mounts to a heavy test bed foundation. For the foundation consider using the heavy galvanized plates plus lead-acid batteries, etc.

The stand must have a battery rack, which will provide weight for stability.

The test control bench should be remote.

The cast brake drum and the rotorhead's hub must be on the same shaft (or tube).

The resistance to rotation is provided by the aerodynamic drag of the blades or the friction on the brake drum.
The RPM of rotor can be taken from the brake drum or the rotorhead's hub.

The rotorhead's frame and the sheet metal brake pad holder must be on the same tube (or shaft).

The produced torque can be taken from the frame or the brake pad holder.

A separate stand will be used to hold the bearings to the rotorhead's frame and brake pad holder, plus the other end of the torque sensor etc.

A separate table will be used and it can be attached or located remotely from the test stand.

Potential Requirements:

Testing of Single Motor only ~or~ Testing of Two Motors c/w Rotorhubs

Stand for testing of 1 motor only c/w rotorhub;

Development of motor's performance and reliability.
Torque-pitch coupling.

Stand for testing of 2 motors c/w rotorhubs will allow for testing of;

All of the above.
Synchronization _ Electrical and mechanical.

______________________

Consider building the basic stand for two motors but start out with just one motor;

Alternatively pay the reduced cost of 2-off in the beginning.

Testing for thrust?

Rotational Inertia:

Rotational inertia may only be of interest in respect to how it effects the controller. I.e. The rate of acceleration and deceleration.

The following is wrong and needs to eventually be corrected. See; DESIGN: Electrotor-SloMo - Rotor - Disk - Gyroscopic Precession

Brake Drum:

The weight of the motor's rotating rotor and stator w/o copper is approximately 10.lbs. [http://www.unicopter.com/1916.html#Weight]

The weight of the rotating brake drum complete with shaft and one bearing = 25.7 lbs. [Ref. The stock weight of rotor and stator is 10 lbs x 37.25 /14.5 = 25.69 lbs]. The mean radius of this weight is approximately 0.333 ft. This gives a moment of J_{M =}m * r², 25.7 * 4 * 4 = 411in-lb-sec², or 25.7 * 0.333 * 0.333 = 2.85ft-lb-sec²,

Aerodynamic Rotor:

3 three blades weighing 2.5 lbs at 70% of a 6 foot radius. 7.5 lbs * 4.2 * 4.2 = 132.3 ft-lb-sec².

The rotorhead c/w motor's rotor will weigh about 8 lbs and the mean radius will be about 0.5 ft.

The combined .....

Bearings:

Bearing 6005-2RS 25x47x12 mm ~ http://www.vxb.com/page/bearings/PROD/Kit479?gclid=CILcuKrR3KMCFQEMbAodXX7q9w Do not particularly want sealed due to testing of no-load.

Requirements for Test Bench with I or 2 Rotors:

At the least make the Test bench to accept 2 rotors.

Consider 2-off of all machined parts.

	Item:	Quantity I Rotor:	Quantity 2 Rotors:
	Basic stand:	1	1
	Electric brake:	1	2
	Water Brake:	1	2 ?
	Bearings:	4	8
	Stator mount	1	2
	Tachometer	1	1
	Strobe	1	1
	Multimeter	1	2
	Torque sensor	1	2
	Thrust sensor	1	2
	Bushing to stator mount	1	2
	Desk	1	1
Machining:
	Shaft	1	2
	Flange - Brake drum	1	2
	Flange - Brake lining frame	1	2
	Mid housing	1	2
	Top flange	1	2
	Spider assembly to hub	1	2
Electrical:
	Controller
	Relay
	Charger	1	1
	Batteries	x 1	x 2

Notes:

The blade pitch can initially be determined by putting scribes on the 3 blade inserts on the rotorhub.

The current test stand does nothing to develop and tes synchronization.

Torque Sensor:

Could the torque measurement be a custom (homemade) potentiometer that goes between the aero-rotor and the electro-rotor. It would measure the rotational advance of the electro-motor over that of the aero-rotor. Must test the device, while stationary, for azimuth deference at various torques. A commutator transfers the voltage to a meter.

Dynamometer:

Power absorber:

Electric Trailer Brake (have)

Water Brake Absorber:

Car radiator for cooling water

Particle Brake: Heat dissipation may be a concern.

http://www.stuskadyno.com/xs-19.html Much bigger than required.

KARTING DYNOMOMETERS http://www.foxvalleykart.com/dyno1.html

Kart DYNO mite Dynamometer http://www.land-and-sea.com/kart-dyno/kart-dyno.htm

The following quotes are from DYNAMOMETER Tech:~ HOW THEY WORK http://www.land-and-sea.com/dyno-dynamometer-article.htm

"Problems with friction brakes included much difficulty in accurately regulating the load and brake pad cooling."

"A more controllable load device is the hydraulic oil pump. These are occasionally seen on low rpm, moderate horsepower engine dynamometers. A positive displacement oil pump acts as the brake, and an adjustable oil discharge orifice valve sets the load. They can have a lower inertia than the DC generator and eddy current units if the pump is small, but sometimes required gear reduction units and coupling adapters push it back up. Like many absorbers, the oil pump units convert a test engine's power into a fluid's temperature rise. Since the oil can't be just freely discharged, a cooling system (typically an oil to water heat exchanger) must be used to keep the oil's temperature within safe limits."

"load cell transducer".

Oil pump vane or gear???? . Pressure valve

http://www.dynapro.co.uk/
Electric Motor Dynamometers:

Alternative or Supplement to Mechanical Brake:

Water Brake Absorber:

A sturdy cylinder with a reasonably large diameter.

Vertical vanes are located inside it with space between them for vanes on a central shaft.

The top and bottom plates of the cylinder will hold flange bearings.

The shaft will protrude on the top and have a flexible coupling on its upper end.

This coupling may be connected to the drum on the mechanical brake.

A viscose fluid that does not foam will be located in the cylinder.

A means of adding and removing portions of this fluid will be required.

This weight of this cylinder and its fluid will contribute to the stability of the stand.

If the torque must be measured off of the stator, since it and the rotor are creating the torque and rpm (i.e. power).

The brake lining plate, water brake absorber and/or rotor blades will be the cause of this torque reaction. They must be attached to the table and restrained from rotoating.

The water brake could be located below the cast wheel brake at some later date.

Load Cells:

The advantage; It will read values at any and all settings without having to change weights.

Can get torque/thrusts load cells. These are too small but are examples ~ torque range too small and thrust range too high.

Cooper Instruments and Systems;

Force: LFS 260/262 Universal Load Cell, Ranges from 0-10 Lbs to 0-1000 lbs

load cell transducer.

Battery Storage:

The 12 volt car battery is < 14" * 7" in plan view. 156 volts will require 13 batteries. 35" * 35" will store 12 batteries. 42" * 35" will store 15 batteries.
An alternative is to store them on 2 decks. Then the plan view dimensions will be 28" * 28"
These are approximately 7" high.
At 55 lbs each 12 will give a weight of 660 lbs.

Charging of Batteries:

How?

110 V or 220 V

Forklift-Battery-Charger.com PBM forklift battery chargers are available in a variety of models and output voltages (12 volt, 24, volt, 36 volt, 48 volt, and 72 volt)

Related Information:

This Site:

Access program 'Motor.mdb'

Outside Site:

Motor Calculations

Last Revised: January 1, 2012