request of information

[giorgio]

Hi gentlemen,

we are an historical aircraft preservation group located in Italy (see our website: www.gavs-torino.it).

we are rebuilding (for static exhibition only) a BM-8 gyrocopter, equipped with a McCulloch 0-100-1 72 Hp engine.

thanks to some infomation drawn from the Forum members we succeeded in rebuilding the missing propelles.

Now we come back to this powerful tool to locate the drawings of the last missing item:

- the mechanical link between the rotating mast (linked to the engine) and the rotary wings.

we will simply make a scale-model (wooden or metal) to represent the actual item.

Is there the possibility to get a drawing representing it?

Should you need any further clarification, pls let me know....

Giorgio from Torino (Italy)

[jcarleto]

Giorgio,

I've read your post a couple of times and believe there may be a misconception. Either that, or you may need plans for a either rotor head, cyclic control system or pre-rotator. Let me clarify a few points:

1. There is no mechanical connection between the engine and rotors in normal flight for a gyrocopter. While there may be a temporary connection (an optional item on the BM-8), called a "pre-rotator," that starts the blades spinning prior to take-off, such a device is normally disengaged before the aircraft takes flight and it is the force of air from forward motion moving up through the blades that moves the main rotors, not the engine.

2. The mast does not rotate. It is a stationary pole that supports a hinged bearing assembly at the top (called a rotor-head). The main rotor rotates around the hinged bearing on top of the stationary pole and is "tilted" fore, aft, left and right along the hinges via push-rods connected to the cyclic or "control stick" for general steering.

3. The rudder is also part of the steering process, but 90% of the directional and attitude control comes from manipulating the angle of the plane of the free-spinning rotor blades.

I apologize in advance if I am mentioning items you of which you are already aware. From this explanation and knowing what you already have perhaps you could ask again. Pictures of what you have would help.

[jcarleto]

OK, I looked at your site and see a 2 place trainer with a Mac engine. Difficult to tell from the picture, but it looks like everything to do with rotor control is in place...perhaps one push-rod is missing..but it could just be an old setup I've not seen before. You are missing only a pusher prop on the back of the Mac engine from what I can tell....and a chunk of rudder. :D

There is something at the rotor-head I don't quite recognize. It might be part of one of the little mini-engines used for a pre-rotator or part of a pre-rotator of some other kind. Pre-rotators have always been a "work in progress" and remain so today. There are many varieties and dozens of unique, one-of-a-kind installations.

[jcarleto]

OK Part II...

I found a better picture of the engine and see that it once had a Wunderlich (or something similar) pre-rotator. It still has the friction wheel, but is missing the drive drum, the casing and the flex cable that goes to the bendix at the rotor-head. I can't see enough of the rotor-head from the pictures I have found so far to tell if anything else is missing. Keep in mind that pre-rotators were and to some extent still are optional.

Fortunately, Wunderlich pre-rotators are still made by Calumet Air. There is a good PowerPoint presentation on the Calumet Air website here:

Http://www.calumetair.com/files/prerotator.pps

That should show you the missing bits.

[giorgio]

Hi guys!!

you are always very useful.

I will make a rough sketch of what we think is missing and some better photo of the present situation of the Bensen.

Accept my best regards....

Giorgio from Torino

PS: in the website some picture of the new propeller, while it was under construction, are available.