A new tractor design

Supermotive

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The decision has been made. I am going to build a side by side gyroplane, based off a Piper J3 platform. The chassis will be a cub-like frame, reduced in length to about 13 feet. The aircraft will have a large NACA airfoil horizontal stabilizer and be furnished with dual rudders. The horizontal stabilizer will be cockpit trimable. The engine will be the RX1 in stock form. The rotor head and wings will be Sport Copter’s latest and greatest. There will be a pre rotator that will allow a 10-20 foot take off in still air. I ordered the 4130N. I will begin the fuselage next month. Stay tuned.
 

wolfy

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Sounds interesting mate but I think maybe a little ambitious to think one of those little Yamaha engines will get a full size 2 seater of the ground in 20 feet.
Even if your prerotator gets you to flight rpm you are still going to need 20-30 knots of airspeed to get airborne, I think you will need more than 20 feet in still air.

But if it works for you I would like one also.

wolfy
 

Supermotive

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Sounds interesting mate but I think maybe a little ambitious to think one of those little Yamaha engines will get a full size 2 seater of the ground in 20 feet.
Even if your prerotator gets you to flight rpm you are still going to need 20-30 knots of airspeed to get airborne, I think you will need more than 20 feet in still air.

But if it works for you I would like one also.

wolfy
It is certainly an ambitious goal. We’ll see if it can be done. I think a good rotor system, a prerotator that exceeds flight rotor RPM, and a light weight airframe will be important.
 

Kevin_Richey

Yamaha gyro...Oregon, USA
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Being able to lift the mains up off the ground in a two place gyroplane takes considerable real estate, owing to the weight of the gyro (bigger engine than a single place requires), plus two people on board, a larger cockpit exposure to the oncoming airstream to carry two people SxS, and much larger rotorblades to fly 2-up, w/ more drag than a single place.

Looks great when one views a Sport Copter M-912 doing it in 10'-20', which is also piloted by one of the best gyroplane pilots in the world. Even better is video of the same pilot/machine being able to lift off w/ barely any rolling of the wheels in a breeze!

The M-912 prerotator can bring the rotors up to near flight speed while still on the ground (about 300 rrpms) for a single place machine w/ shorter rotors since it only needs to lift the machine & the pilot.

I haven't seen any video that shows any two place gyroplanes doing anywhere near that, nor heard of anyone having developed a prerotation system that can match that. The exception is when the rotorblades pitch is temporarily reduced & rotors can then be spun up past flight speed b/4 pitch is then restored , enabling the gyroplane to leap off the ground. The Air & Space 18A, Dick Degraw's Gyrhino aircrafts, the Carter Copter, & a few others are examples. They are a quasi-helicopter @ that point, due to their ability to have a collective control.

Usually the best one can expect out of a two place gyroplane is 140-180 rrpms prior to starting the takeoff roll, then build up past 200 & beyond up through flight speed when the rotors can lift the entire machine off the ground.

I believe Wolfy is not as correct regarding airspeed for a two place. 20-30 knots fits a single place gyroplane to starting the lift-off. Any two place gyroplane I've been in usually need much more to levitate. Usually over 50 mph & up, to about 55-65 mph. Larger, heavier rotorblades cannot be rushed into lifting off b/4 they can accept the oncoming airflow necessary for flight. It takes longer to get them up to speed than single-place rotors, which are smaller in disc size & lighter.

A worthwhile project you are embarking on, Supermotive! The drawbacks of the tandem gyroplane solved w/ a SxS cockpit. You're trading the better streamlined cockpit (and lower fuel consumption) that a tandem offers for what a majority of folks want when flying w/ another person, the SxS seating.
 
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Supermotive

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Being able to lift the mains up off the ground in a two place gyroplane takes considerable real estate, owing to the weight of the gyro (bigger engine than a single place requires), plus two people on board, a larger cockpit exposure to the oncoming airstream to carry two people SxS, and much larger rotorblades to fly 2-up, w/ more drag than a single place.

Looks great when one views a Sport Copter M-912 doing it in 10'-20', which is also piloted by one of the best gyroplane pilots in the world. Even better is video of the same pilot/machine being able to lift off w/ barely any rolling of the wheels in a breeze!

The M-912 prerotator can bring the rotors up to near flight speed while still on the ground (about 300 rrpms) for a single place machine w/ shorter rotors since it only needs to lift the machine & the pilot.

I haven't seen any video that shows any two place gyroplanes doing anywhere near that, nor heard of anyone having developed a prerotation system that can match that. The exception is when the rotorblades pitch is temporarily reduced & rotors can then be spun up past flight speed b/4 pitch is then restored , enabling the gyroplane to leap off the ground. The Air & Space 18A, Dick Degraw's Gyrhino aircrafts, the Carter Copter, & a few others are examples. They are a quasi-helicopter @ that point, due to their ability to have a collective control.

Usually the best one can expect out of a two place gyroplane is 140-180 rrpms prior to starting the takeoff roll, then build up past 200 & beyond up through flight speed when the rotors can lift the entire machine off the ground.

I believe Wolfy is not as correct regarding airspeed for a two place. 20-30 knots fits a single place gyroplane to starting the lift-off. Any two place gyroplane I've been in usually need much more to levitate. Usually over 50 mph & up, to about 55-65 mph. Larger, heavier rotorblades cannot be rushed into lifting off b/4 they can accept the oncoming airflow necessary for flight. It takes longer to get them up to speed than single-place rotors, which are smaller in disc size & lighter.

A worthwhile project you are embarking on, Supermotive! The drawbacks of the tandem gyroplane solved w/ a SxS cockpit. You're trading the better streamlined cockpit (and lower fuel consumption) that a tandem offers for what a majority of folks want when flying w/ another person, the SxS seating.
Agreed. I spoke to a gentleman at Sport Copter that has a system that can spool up the rotor to about 300 rpm. I believe this immediately followed by a Yamaha RX1 motor singing at just shy of 10k rpm should thrust the copter forward to quickly pick up where the pre rotator left off. I will try to keep the weight below 600 lbs empty. I will also streamline the fuse and control surfaces. Hopefully all of that will pan out nicely.
 

WaspAir

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I think a good rotor system, a prerotator that exceeds flight rotor RPM, and a light weight airframe will be important.
If you're exceeding flight rpm in prerotation with flight pitch, what do you expect the aircraft will be doing at that moment, how will air be flowing through the disc, what will be resisting prerotator torque, and what power is going through the prop at that time?
 

Supermotive

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If you're exceeding flight rpm in prerotation with flight pitch, what do you expect the aircraft will be doing at that moment, how will air be flowing through the disc, what will be resisting prerotator torque, and what power is going through the prop at that time?
Let me try to answer your questions. I would expect to be marginally lifting. I would think some air would be fanned up and through the disc. I think while the wheels are on the ground, prerotation torque would be resisted by the wheels. The prop should be at a low enough rpm that the brakes could hold off forward acceleration. These are all assumptions. I have not empirically measured anything at this point. Are my assumptions reasonable? Please help me understand if I am ill informed.
 

wolfy

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Being able to lift the mains up off the ground in a two place gyroplane takes considerable real estate, owing to the weight of the gyro (bigger engine than a single place requires), plus two people on board, a larger cockpit exposure to the oncoming airstream to carry two people SxS, and much larger rotorblades to fly 2-up, w/ more drag than a single place.

Looks great when one views a Sport Copter M-912 doing it in 10'-20', which is also piloted by one of the best gyroplane pilots in the world. Even better is video of the same pilot/machine being able to lift off w/ barely any rolling of the wheels in a breeze!

The M-912 prerotator can bring the rotors up to near flight speed while still on the ground (about 300 rrpms) for a single place machine w/ shorter rotors since it only needs to lift the machine & the pilot.

I haven't seen any video that shows any two place gyroplanes doing anywhere near that, nor heard of anyone having developed a prerotation system that can match that. The exception is when the rotorblades pitch is temporarily reduced & rotors can then be spun up past flight speed b/4 pitch is then restored , enabling the gyroplane to leap off the ground. The Air & Space 18A, Dick Degraw's Gyrhino aircrafts, the Carter Copter, & a few others are examples. They are a quasi-helicopter @ that point, due to their ability to have a collective control.

Usually the best one can expect out of a two place gyroplane is 140-180 rrpms prior to starting the takeoff roll, then build up past 200 & beyond up through flight speed when the rotors can lift the entire machine off the ground.

I believe Wolfy is not as correct regarding airspeed for a two place. 20-30 knots fits a single place gyroplane to starting the lift-off. Any two place gyroplane I've been in usually need much more to levitate. Usually over 50 mph & up, to about 55-65 mph. Larger, heavier rotorblades cannot be rushed into lifting off b/4 they can accept the oncoming airflow necessary for flight. It takes longer to get them up to speed than single-place rotors, which are smaller in disc size & lighter.

A worthwhile project you are embarking on, Supermotive! The drawbacks of the tandem gyroplane solved w/ a SxS cockpit. You're trading the better streamlined cockpit (and lower fuel consumption) that a tandem offers for what a majority of folks want when flying w/ another person, the SxS seating.
Yes agreed mate, 20 -30 knots for a two place was being extremely optimistic in an absolutely best case scenario when horsing it off the ground early, still not going to happen in two airframe lengths.

I have also flown a sport copter m912, and my own mustering machine was a very light(lighter than m912) single seat 912 (with climb prop) and sport copter pre rotator. My brakes could hold enough engine rpm to pre rotate to about 300 rpm and still air take offs would have been more like 60-80 feet ringing its neck.

wolfy
 

Supermotive

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Wolfy, what was your dry weight, what was your horsepower, and what rotors did you have when you needed 60-80 ft to lift?
 

Supermotive

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I am looking at building a tail dragger weighing less than 600 lbs empty, and having about 140 hp on takeoff. I will likely use a 29 foot rotor wing set with an 8 inch to 8.5 inch chord. Prerotating to 300 rpm is my goal.
 

wolfy

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Wolfy, what was your dry weight, what was your horsepower, and what rotors did you have when you needed 60-80 ft to lift?
Dry weight was about 180kg, 100 horse 912 and 27' rotors. 60-80 foot was a best guess from memory (been a few years), you have to remember its a rotary wing even at flight rpm we need airspeed to fly it takes real estate to get airspeed in still air.
wolfy
 

wolfy

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I am looking at building a tail dragger weighing less than 600 lbs empty, and having about 140 hp on takeoff. I will likely use a 29 foot rotor wing set with an 8 inch to 8.5 inch chord. Prerotating to 300 rpm is my goal.
I really like your idea as I am considering a side by side tractor also at the moment, but I think maybe you should consider 100 foot (still air) as a short take off and anything less a bonus.

What ratio will you use for your redrive? As best I can tell most of those yamaha's make there rated power somewhere around 10'000 rpm but a lot of the Yamaha conversions I have seen seem to run the engine upto around 7k meaning they are nowhere near rated power, ( I could be wrong havn't looked in great detail).

Pre-rotating to 300rpm will feel better with the tractor's longer wheelbase (especially if the tail wheel was non castoring).

There is a video on youtube somewhere " wolfie showing his agile gyro" (I think) that take off was into about a 10-12 knot headwind and its still probably 30-40 feet.

wolfy
 

Supermotive

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Wolfy, it sounds like you know your stuff. Wow, your machine is very light. To tell you the truth, I would be satisfied with a 100 foot takeoff. I am trying to make it shorter so I can safely take off on a small piece of land rather than someone else's airfield. I am a middle class guy that needs to put 2 kids through college still. I will be taking off at about 9500 rpm. The motor makes about 140hp there. The gear reduction will be 3.47:1. I am currently looking for the best option of preroting right now. 300 rpm is the goal. My options now that I am considering are flex shaft or electric. I am an Electrical Engineer so it is not difficult for me to whip up a speed control with soft start for a motor. I am still new here so I am happy to receive all criticism and advice.
 

Supermotive

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Dry weight was about 180kg, 100 horse 912 and 27' rotors. 60-80 foot was a best guess from memory (been a few years), you have to remember its a rotary wing even at flight rpm we need airspeed to fly it takes real estate to get airspeed in still air.
wolfy
I am confused. I thought with a rotary wing it only took wing speed (rrpm) to get lift and air speed to maintain rotor rpm. What am I missing?
 

wolfy

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Wolfy, it sounds like you know your stuff. Wow, your machine is very light. To tell you the truth, I would be satisfied with a 100 foot takeoff. I am trying to make it shorter so I can safely take off on a small piece of land rather than someone else's airfield. I am a middle class guy that needs to put 2 kids through college still. I will be taking off at about 9500 rpm. The motor makes about 140hp there. The gear reduction will be 3.47:1. I am currently looking for the best option of preroting right now. 300 rpm is the goal. My options now that I am considering are flex shaft or electric. I am an Electrical Engineer so it is not difficult for me to whip up a speed control with soft start for a motor. I am still new here so I am happy to receive all criticism and advice.
Sorry to keep bursting your bubble mate, but I think maybe your redrive ratios are less than ideal. To do what you want to do you need a large diameter prop, for that means slow prop rpm. At 9500rpm with 3.47 your prop is doing around 2700 that means your limiting your diameter to keep the tip speed acceptable. You would benefit from a higher ratio something around 4-4.5:1.

I am interested in what someone like you could do with modern electric motors for prerotators, electric is nice and simple.
29' rotors take a bit of torque to get started, an engine that needs 10000rpm to make its power is not going to have much torque especially at low rpm while driving a prop and engaging the pre rotator might bog the engine down. Might be okay though they can be engaged very gradually.
wolfy
 

Supermotive

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I apologize. I told you wrong. The Yamaha has a built in gear reduction of 1.19:1. My gearbox is 3.47:1. The total reduction is 4.13:1. Sorry for the confusion. I am considering a 72-76 inch prop right now. The 72 would likely be a 3 blade, and I am not sure if the 76 would be a 3 blade or 2 blade.
 

Supermotive

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I apologize. I told you wrong. The Yamaha has a built in gear reduction of 1.19:1. My gearbox is 3.47:1. The total reduction is 4.13:1. Sorry for the confusion. I am considering a 72-76 inch prop right now. The 72 would likely be a 3 blade, and I am not sure if the 76 would be a 3 blade or 2 blade. Do you have any estimation of the torque required to prerotate the 29 inch to 300 rrpm?
 

ultracruiser41

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Ambitious indeed. My suggestion would be to learn to fly a gyro and start with a proven design for a few years before trying to re-invent the wheel. There is much to learn about gyroplane flight characteristics that can only be learned from putting hours in the air.

As you said in another post.....safety is your number one concern.....so a proven, safe design seems to be the more logical decision. A lot of people here want to see you succeed.......and taking the proper steps will help ensure you will.
 

Supermotive

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Ambitious indeed. My suggestion would be to learn to fly a gyro and start with a proven design for a few years before trying to re-invent the wheel. There is much to learn about gyroplane flight characteristics that can only be learned from putting hours in the air.

As you said in another post.....safety is your number one concern.....so a proven, safe design seems to be the more logical decision. A lot of people here want to see you succeed.......and taking the proper steps will help ensure you will.
I will likely train with a local CFI, for a while, in an RAF 2000. My build starts next month and will take years.
 

wolfy

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That sounds a better ratio, not sure about the torque required but your engine will do it it's just getting them started at low engine revs will be the challenge untill the belt is fully engaged then you can start adding throttle.

wolfy
 
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