Tuesday, June 16, 2009

Adapting a starter to the McCulloch engine

The McCulloch engine was never meant to carry man or woman in flight. It was designed during world war 2 for the military. It was used to power small drone airplanes which towed a long banner for the military pilots to practice shooting at. The engine was meant to make one flight, period.
Along came gyro pilots looking for a small
light-weight powerful engine to use on their gyrocopters. I was one of them.
After first trying heavy Volkswagen engines and various motorcycle engines on their gyros, the pilots generally discarded them and began to use the surplus McCulloch engine. The Mac, as it was called , was readily available, lightweight, inexpensive and unbelieably unreliable .
The gyro pilots didn't give up easily , so they set about learning ways to make the Mac reliable. There were a number of modifications necessary , such as cam grinding the skirts of the pistons, using new and different bearings, proper oil and av gas mixture, and a host of other mods. Finally the Mac was fairly reliable. The weight to power ratio of the engine couldn't be beat for it weighed only 72 lbs. and came in a 72 or 90 hp. version. The weight was the same for each version.
Down through the years more modern engines became available for gyros but some of the gyro pilots stayed loyal to the McCulloch engine. I am one of them. To use a different engine would mean changing many things on my Bensen gyro and I didn't want to change the configuration of the gyro for I love it the way it is. I don't mess with perfection!
The Mac doesn't come with a starter...that wasn't a problem as long as I had my husband who was always right there whenever I flew the gyro. Docko would pull the prop through to start the engine for me. Propping the engine is not something you ask just anyone to do. The person handlling the prop has to know exactly what he is doing for it is a dangerous procedure . Carelessness in proping could result in losing a hand, fingers or an arm.
So, that gave me a problem when I returned to gyro flying some years after the passing of Docko. My gyro pilot friends who were knowledgable about starting the engine would prop the Mac for me but they were not always available when I wanted to fly.
Then one day, someone on the rotary wing forum on the internet posted something about making a starter for the McCulloch engine...that got my attention big time. I ordered one, it arrived soon afterwards , then the frustration began. Some modifications were going to be necessary if the starter was going to work on the Mac engine.
My gyro has a prerotator which is a device that spins the rotors and shortens the take off run. I am convinced I can't live without the prerotator!!! The problem is that the prerotator drive drum and drive wheel are located right where the starter has to go.
I contacted Dave Bacon, a friend who is a gyro pilot and who also flies a McCulloch engine. He is in the process of adapting the starter to my engine. He is having to make several modifications to the prerotator and I don't know what else but I am confident he will get the starter up and running soon.
In the photo above, Dave is the one in the white shirt kneeling . The gyro pilot on the left in the colorful shirt is Teddy Udala . Dave's dad, Eber Bacon, an old time gyro pilot from the 60's , is in back of Dave and farther back is Ron Klock, who flies a powered parachute.
We expect to be able to fire the engine up with the starter ( I'll just push a button for that !!!) in a couple of weeks. I'll keep you posted.
Till next time.
Marion Springer

1 comment:

jerry said...

I have a McCulloch engine on my Gyrocopter with the same starter and prerotator together they work well. I had to make some modifications to both the stgater sytem and the prerotator to get them to work together any one needing help email me at geralddevereaux@hotmail.com i will forward pictures to your email address.