request of information

[giorgio]

Hi gentlemen,

we are an aircraft restoration group located in Italy (see our site www.gavs.it - also available in English language).

We are presently rebuilding (for static exhibition purposes only) a BM-8 gyrocopter, equipped with a McCulloch O-100-1 72 Hp engine.

Unfortunately we miss the Propulsive propeller; so that a complete rebuild cannot be done unless some of you give us information on :

- diameter of the propeller
- propeller pitch

We thank you in advance for your kind cooperation

Giorgio

[Bob Simmons]

contact gyro mike (Mike Gaspard). He has alot of data on the bensen and he owns one. good luck

[gyromike]

Giorgio,

You will have to measure how much clearance you have between the crankshaft center and the top of the keel. I have ~27 inches, so I swing a 52" diameter propellor (26" radius), and I have ~ 1" of clearance betweeen the prop tip and the keel.

If you have less than 27" you may have to use a 50" prop, like a 50" diameter x 24" pitch.

I use, and recommend, Tennessee Props.
http://www.tn-prop.com/prop.htm

[Caribean_gyro]

we use 50-30, can be an sterba, stcroix, troyer. Now if is to doit as original bensen did I think he used a lower pitch, I think was 50-26:cool:

[Passin' Thru]

If you're duplicating the original Bensen B8-M, the prop diameter was 48 inches for both the 72 and 90 HP Macs. The pitch was 26" for the 72HP and 28 for the 90Hp. The original Bensen "factory" props were manufactured by "Ariel" (sp?) someplace in Texas. Not the most efficient prop I ever used!
I used this prop on my first gyro which was pretty much to Bensen plans, but on later machines went to 50 and then 52 inch diameter Troyer props. The mast height of these later Mac powered machines was increased from the original 58 inches to 60 inches, and the engine raised 2 inches for prop clearance.

[giorgio]

thanks to all, guys!!!!!!!!!!!!

Giorgio