airspeed

For an experiment I would like to create airspeed between 100 mph to 135 mph.

The airspeed has to go into 3 Ventura’s that the entry is 1.0625” diameter each.

As cost has to be considered would I be able to use some form of fan or propeller preferable home constructed and what size and motor speed, hp would be required?

Also an airspeed indicator is needed a slow wind speed one is easily constructed small hand held ones in the lower price range do not go to the airspeed I require.

For 100 mph plus would a pitot tube be required and a means of calibrating it.

I prefer to construct these myself if not too difficult unless there are some for sale that don’t cost an arm and a leg.

PS I still do not get Email notification to my threads despite being on my bookmarks so have to check the bookmarks for replies..

Suggestions please.

Paul

I can't seem to find it on the net, but the Mythbusters tv series set up an experiment to see if bullets fired vertically came back to earth with lethal force. They set up a vertical wind tunnel using about 50mm plastic tube and airspeeds of around 130mph. Bullets dropped into the tube were supported by the airstream, leading to the conclusion that the bullets terminal falling velocity was about 130mph.

I have a hazy memory that they used a shop compressor to generate the air velocity in the tube with a hand held airspeed meter to measure the speed.

A manometer could be made with some plastic tubing, not sure how you would go about calibrating it though.

Paul,

At those speeds, I think you should be able to use a Pitot tube

This paper is worth a read.

MichaelG.

Thanks Michael it was an interesting read I will be talking to a chap from the University tonight and will see if he can help.

Paul

It's easy enough to make a water manometer and pitot head to measure airspeeds in the range specified. It shouldn't need calibrating. If one wants to be precise one can take into account the variation in dynamic pressure with density, but unless one is half way up a mountain I doubt it'll make much difference. There are also errors at higher airspeeds from assuming that the dynamic pressure is exactly 1/2 rho V squared, but at 130kts these are less than 1%.

I've used a home made water manometer to calibrate aircraft ASIs for full size gliders.

Regards,

Andrew

Paul, a pitot system using a light aircraft air speed indicator would be your best bet for those airspeeds!

Ask around local aero clubs to see who maintains their aircraft and talk to the engineers, they'll most likely have a pitot head and ASI kicking around for not a lot that's not up to scratch for certification or repair!
Common Cessna and Piper models generally operate around 90Knots and well within the scope you're looking at!

Chances are for training aircraft on a public cat CofA, they'll all use the engineers at Sturgate airfield near Gainsborough, but more local fields near York may yield glider, microlight or ultralight aircraft bits, although may be more limited on speed range!
Also see if there are any PFA groups too, their aircaft are self maintained on a permit to fly, so a local inspector/owner may point you to some useable spares!

I think Sherburn in Elmet Aero club have their own maintenance facility, may be worth asking there!

Not sure what you could use for the air feed, how about a high revving ducted fan I.C.engine? that ought to shove a bit of a draught out

John

Edited By RJW on 29/01/2014 15:02:35

Hi Windy

Have you looked at using a reversed domestic vacuum cleaner or cleaners if you need more flow (some are around 1500 watts) maybe with a speed control that works with brush type universal motors. Maybe an electric router or hand drill controller will do.

I tried in vain on the net to get the typical air speed.... Hmm

The pipework may need to be designed carefully to smooth out the turbulence from both the machine and the pipework if your experiment requires it.

Regards
John

Hi Paul

As Andrew says the water manometer method is commonly used in gliding club workshops. Why not pay your local club a visit and seek their assistance? Pretty much all work on gliders is d-i-y work by members and you are likely to find them friendly lot. Whilst there, maybe take a trial flight?

( Be warned though - gliding is very addictive!)

Norman

Many years ago, when I did an industrial placement at RAE Farnborough, we were investigating the efficacy of various fire suppression systems in aircraft wing fuel tanks. In order to test these we fired canon shells (from a captured soviet gun) at a full size mock up of a wing section with a tank of fuel in it. In order to simulate the airflow over the wing we used the exhaust from a RR Avon engine (which for some historical reason was mounted on a coach chassis). The exhaust was directed into a venturi that induced an airflow down some ducting. One of my jobs was to measure the air speed over the wing using a pitot tube on a stick- with 2 other guys holding on to me. Usually about 120mph. Sometimes the fire suppression systems worked but it was much more fun when they didn't!

Sorry, this doesn't help at all - unless you have an Avon handy.

Rod

I might have a solution for creating the airspeed a friend suggested a leaf blower depending on size etc. they can go up to 200mph.

Paul

This idea is probably to crude for your usage, but it might be of interest-- some years ago I needed to measure wind speed and asked my brother, who was working for the met office then, if he had a wind speed indicator. He didn't but gave me a method. Hang a suitable sized flat plate from a "goalpost " structure. Calibrate by driving a car and stick the thing out of the window, mark the inclination at a few speeds. interpolate for intermediate speeds. This worked for my needs but have no idea how accurate it was.

I'v got a little gadget here that Andrew, and some others may know, It's a Dwyer Wind Meter, it's basically a plastic tube about 6" long, with an air intake at the bottom, an a graduated outlet at the top. In the tube is a small (about 1/8" dia.) plastic ball that indicates the air speed against a scale up the side of the tube. It only reads to 65mph.

Ian S C