RFQ Questions 2.pdf

Question 1: Do you have specific load magnitudes for this force balance? And can you explain a little more about the acquisition system compatible with NI LabView software and NI cDAQ chassis with NI-9239, NI-9237 or other appropriate cards?

The load magnitudes have not been established at this point. As one of the parts of this bid, the winning company will have to work with USAFA to determine appropriate loads for our tunnel conditions and factors of safety for development.

In our lab, we exclusively use National Instruments (NI) products, so any system will need to be compatible with what we already have on hand. While we don't require NI products, any substitutions will have to work seamlessly with our existing hardware, software, and be able to sync properly across multiple other systems.

We would not consider a bid for force balance only. This is our first ever wind tunnel balance for this facility, and we do not have the necessary hardware currently to run the balance system, and we want a fully operational, turn-key system to be delivered to us that only requires software development on our part. In addition, the winning bidder will have to provide check-out testing and training, meaning we would not be able to test the balance without the appropriate acquisition hardware already in place.

Question 2: We contacted qualified force-balance manufacturers regarding solicitation FA700026Q0081. They advised that the current specifications lack sufficient technical information to design or provide firm pricing.

Please provide the following:

• Axial, normal and side force load ranges: Fx, Fy and Fz o Unknown at this time

• Roll, pitch and yaw moment ranges: Mx, My and Mz o Unknown at this time

• Maximum startup/transient loads o Unknown at this time

• Required overload capacity or safety factor o Not fixed yet, but probably a safety factor of at least 2

• Required accuracy, resolution and repeatability o To be determined once the above values are fixed

• Required bandwidth or natural frequency o Must be able to resolve loads at a minimum of 10 kHz

• Model, sting and balance interface dimensions o We currently have no models or stings. The winning bid will need to provide a sting and calibration models. Current estimates are for a 1" outer diameter balance.

• Operating temperature range o 60-120°F

• Required calibration standard and number of calibration points o Not determined at this time

• Additional details regarding the required tunnel startup-load testing o Will utilize some standard model geometries across our range of operating conditions

Please also confirm whether the Government will issue an amendment containing this information or whether offerors should propose a design based on stated assumptions.

-Even without answering the information above, we were able to successfully solicit bids from two vendors. Most vendors are familiar with the more standard practice of receiving these design values and building to spec, but since this is a new system with many unknown factors, the winning bid will need to work with USAFA on the actual design and calculation of these values.

These parameters are necessary for manufacturers to produce a technically compliant and firm-fixed-price quotation.

Question 3: I am reviewing the request for bid (FA700026Q0081) for a six-component force balance for the Mach 6 Ludwieg Tube wind tunnel, and I have some questions regarding this application.

• Is the proposed system an upgrade from an existing setup? Our six-component balances have previously been supplied with cDAQ chassis using the NI-9237 bridge module.

o This is a completely new system with nothing currently available

• Will the balance be installed on an existing model support fixture?

o We currently have no existing supports or stings

• Looking at the requirement to test the startup loads of the system, is there a standardized test article that has been used previously to quantify the transient regime of the system?

o There has been no previous testing done to quantify these values

• What are the anticipated aerodynamic loads for each of the components?

o Pitch o Yaw o Drag o Pitch Moment o Yaw Moment o Roll Moment

All of these are unknown at this time

• What types of models will be used for testing?

o Wide range of models from slender cones to blunt bodies

• What is the anticipated range of mass for the models under test?

o Most models are under 10 lbs, but that is not fixed at this time until the remaining constraints are determined

Question 4:

• Overall form factor and maximum allowable dimensions o Maximum tunnel diameter is 500 mm

• Mounting and interface requirements for mating components o Unknown at this time

• Full-scale load requirements for Fx, Fy, and Fz o Unknown at this time

• Full-scale moment requirements for Mx, My, and Mz o Unknown at this time

• Maximum startup/transient loads and required overload limits o Unknown at this time

• Diagram showing the force and moment axes relative to the balance o Unavailable at this time

• Required overall measurement accuracy, resolution, and repeatability o Unknown at this time

• Maximum allowable sensor mass, if applicable o Unknown at this time

• Minimum natural frequency or required stiffness o Unknown at this time

• Desired frequency response or measurement bandwidth o Minimum 10 kHz

• Minimum and maximum operating temperatures o 60 - 120°F

• Pressure or vacuum conditions o 1 - 1500 mbar

• Operating medium, such as air or another gas o Air

• Expected moisture and humidity exposure o No moisture, standard local humidity of CO

Please also provide any available tunnel drawings, sting/model interface drawings, previous load estimates, startup-load data, or related technical documentation.

-We are unable to provide tunnel drawings at this time. There are no current sting or model drawings. Load estimates for measurement or startup are not available at this time.

Could you please confirm whether this information will be provided directly or through a solicitation amendment? These details are necessary for manufacturers to develop a technically compliant, firm-fixed-price quotation.

-All of the information above will be determined in cooperation with the vendor and the Academy during the design process of the balance. The vendor will have to work closely with the Academy to estimate loads either analytically, or preferably, through measurement in the tunnel with their own provided equipment. The remaining requirements will be determined once initial estimates and design are complete.