2025-12-25

Last modified: 2025-12-25 18:08:30

Old Bear Biplane

There is a biplane in "Old Bear", illustrated in the book as follows:

The plan is to build a replica.

There is some confusion because the biplane in the television series doesn't exactly match the one in the book.

This is the television version: https://www.youtube.com/watch?v=ePCof76DLO0

The biplane is first seen at 4m46s. Some stills from the television version:

So the visible differences are:

• the disc behind the propeller is clearly wooden in the book but could be brass in the television version
• the wings are thicker in the television version
• the wood grain on the fuselage is much more visible in the book whereas the television one appears to be painted yellow

Personally I think the version in the book looks much more elegant.

Obvious components are:

• fuselage
• 2x wings
• 4x wing struts
• horizontal stabiliser
• vertical stabiliser
• undercarriage
• 2x wheels
• axle
• propeller
• disc behind propeller (represents engine?)
• 7x brass screws
• 5x brass ferrules
• washers? to allow wheels and propeller to spin freely

And then the only sticking point is that in the book it is stated that Bramwell Brown "began to wind up the propeller of the plane", alongside the illustration of him turning the propeller:

This suggests that the propeller is powered by an elastic band or a spring or something, but there is no obvious place for this mechanism to be concealed. So either something like the fuselage is actually drilled out and there is a twisted-up elastic band running along the length of it, or else the "winding" of the propeller is as imaginary. There is precedent for imaginary behaviours because the plane is obviously incapable of flight and yet is later seen to be flying. So maybe we just say that the propeller is simply free to spin? Does the disc spin with it? Does the disc spin freely on its own?

I guess if you are saying that the disc represents the engine, then the disc should either be fixed to the fuselage (radial engine) or the propeller (rotary engine). There is no scenario in which it is reasonable for the disc to spin independently.

I think the plan would be to make the fuselage and undercarriage by hand on the tablesaw; buy appropriately-sized dowels for the wing struts; make the wings, tail, propeller from thin plywood on the CNC machine; and make the wheels and propeller disc by hand on the lathe.

I'm going to try to get it designed in FreeCAD and see how it looks.

The fuselage has a square cross section at the front, with chamfers on the leading edges. It tapers towards the tail. It's not clear exactly how it tapers, I guess just guess something and see.

In the book it looks like the fuselage is almost flat along the top and tapers "up" at the bottom, whereas on the television version it looks like the opposite.

Actually it depends which illustration you look at. Maybe the best thing to do is make it symmetrical.

OK this is what I have:

Sized so that the large square section of the fuselage is 75mm. It feels like that may be too big, I may want to scale everything by 2/3. Will leave it for now and come back to it.

I think the final important thing is that perhaps the fuselage taper wants more of a curve instead of being a straight cut.

One more thing: need to make sure that the wheels are touching the ground when it is sitting on the ground. I think currently it will balance on the tail and the back of the undercarriage, and the wheels will be raised up.

As regards finish: you can see reflections in some of the illustrations, most obviously there is a reflection of the lower wing in the side of the fuselage in the picture where Bramwell is winding the propeller. So I think the fuselage wants to be varnished rather than painted, and left glossy.