Category Archives: Experimental

Transport Calculations

Education, Experimental, Gallery, Outreach, Sighting,

Here’s a cool calculation from Angela Coburn of ubc.

This is part of Physics 420 where they learn to demonstrate physics to the public.

I think this is an awesome idea to teach young physicists to discuss and demonstrate physics to the general public (including children).

This is great for the cause of physics and for any individual who works in the field.

I realize that the purpose of these calculations isn’t to model the situation perfectly but it’s to open the door to understanding.

I’m curious if anybody has any comments or other ways of performing this calculation.

I also noticed Zach Hulbert from the same class did a blurb on the Physics of Rubber Bands.

First, I measured the force exerted on the propeller by the twisted rubber band.  I did this by using a digital scale.

After twisting the rubber band, I placed the outside edge of the propeller on the scale, as shown in the following picture.

The scale measured in grams, so I needed to convert this to Newton’s.

Where,

m = the reading on the scale

a = 9.8 m/s2

Then I measured the radius of the propeller and calculated the work.

Where,

F = the previous calculation

d = 2πr X (number of turns)

Then the power could be calculated by measuring the time it takes for the propeller to unwind.

Where,

W = work

t = time in seconds

These calculations can be seen in an excel spreadsheet here, Spreadsheet. (RubberEnergy1)

In order to calculate the transport cost, the glide slope was determined by measuring how far the airplane “glided” when launched without the propeller powering it.  This was done several times to get an average estimate.

Where g is the acceleration due to gravity.

Note: the units of transport cost, m/s2 are equivalent to J/kg/m

Then convert the units to kWh/tonne/km and compare to a Boeing 747.

1kWh = 3.6MJ

Link to excel spreadsheet, Transport Cost (transport_cost)

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Squirrel predecessors

Experimental

Dinkar received two of the three boxes that were sent out. The one missing is the camera I sent him so we’re still using his phone camera. Pictured below is his postman whom he says is a very nice person. You can see that the boxes made from reused cardboard survive quite well.

The lubricant which I bottled and double bagged leaked. I’m surprised. There must be a lot of temperature and pressure variation during shipping. I will send some lubricant to some more addresses to see if I can get it to survive shipping. Also I was surprised to find that some of the sticks on the AMA Cub arrived broken.

I sent the Minnow and the AMA Cub. The minnow was designed by my friend Lloyd Shales. It’s a great indoor model.

The AMA Cub is the Squirrel’s predecessor. Designed by Frank Ehling around 1957 it was revolutionary. It still requires tools and many steps and parts and when I used it to introduce people to model aviation, I found that it was still too much work.

So that’s why I designed the Squirrel. To make it easier.

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Voice design progress

Experimental

I think I’m onto something here as you can see from these pictures from the lab.

On the design I’m still working on a few challenges. I’m convinced it flies well with just webbing rather than the banner. I flew that configuration it in the lab. It’s tricky to get a good assessment indoors but I’ve used to it. 🙂

A couple things about assembly and a couple things about aerodynamics are on the table. There are some configurations that get into an accelerated phugoid. I think I may learn something about aerodynamics here as I can’t imagine what could cause that.

But it’s pretty clear that this will gel pretty soon.

This thing has more wing area than a Squirrel but actually less balsa parts. It also has a lot of space to add a message which I think will be very exciting. People can decorate the banner with markers and so forth and then attach it to the plane.

I’m going with a fixed wing attachment rather than a sliding one (since I haven’t figured out how to make it slide). It’s difficult for prototyping since I have to add ballast or move the propeller fore and aft. But in the end I think it will be predictable to fly without trimming. We’ll see if I can get that to gel. I need to spend at least another a hundred hours or so on this. I’m pretty excited as I see some potential here.

The working name “voice” is a little dry. But it’s a cool working name since the plane can deliver a message through it’s banner. “Tweet” is nice. Since a tweet is short and limited to physical proximity. I will name it after the design is finished.

My original idea was that this plane could make some rounds at various protests and public events and carry peoples’ messages. That’s where the working name “voice” came in.

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