JoelW
Posts: 121
Joined: 7/17/2002
From: Darby,
MT, USA
Status: online
|
Roger,
Looking over the photos your PT25 looks very nice. I can't see anything that might be causing the problem from looking at your photos. My PT25 flew like yours as far as the constant climbing tendency. The PT25 was intended to be used with a .25 engine from the start because I think it was meant to be a trainer. The thing I didn't like about it was the tendency to always climb when power was added. My preference was to fly faster because I tend to want to do more interesting manuvers than just flying around the pattern. These PT25's are doing what they were designed to do as a training autogyro to give new people a chance to become autogyro pilots. In the past when autogyros were used before the helicopter was invented they flew very much like the PT25 does now. By this I mean, they got the rotor spinning up to autorotation, took off then added enough throttle to climb to altitude needed then backed off the throttle to decend when they needed to. We in our model hobby have much more power than we really need just to take off and fly. One of the things I did to make myself happy so that I could fly faster and be more aggresive as in sport plane type flying was to build another PT25 of my own design that would be more fun and do some aerobatic type flying. I built another PT type gyro that would fly fast and be very manuverable. I moved the mast a little aft, used 2 inch aerobalsa blades instead of the 2 3/8" blades because they provided less lift, then shortened the blades as well since the mast was moved aft a little. The last thing I did was provide more rudder area and increase the rudder throw till it would move 45 degrees left or right.
I found that by making these changes, If I provided left or right rotor tilt of at least 15 degrees while holding full rudder in the same direction, I could do a snap roll with no problem providing I had enough airspeed and altitude to recover.
You changed the servo on your left and right tilt to a HS645 and left the HS225 on the fore and aft tilt. I think I would possibly change the HS225 on the fore and aft tilt to a stronger servo to keep the drag and air loads from allowing the rotor disc to possibly tilt aft and cause the gyro to climb
without being commanded to do so. With all the muscle the stronger servos provide, your pushrods could possibly flex and possibly allow unintended movement of the rotor pitch angle. You might consider using a stiffer push rod for the pitch control?
I wonder if you have changed the length of your push rod for your pitch control? I also wonder if you tried adding some weight to the nose to keep her from climbing so much?
Don't give up, it's too much fun,
Joel
|
Printable Version
All Forums >> RC Helicopters >> AutoGyros >> PT-25 Help 
PT-25 Help - 
