How well does a castor wheel type tail wheel work?
#26
Join Date: Jan 2004
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Speaking as a club safety officer, I'd like to ask a question.
Your plane with a castering tailwheel is ready for takeoff and there are several other pilots on the flight line. You throttle up to take off, there's a crosswind and you find your plane heading towards your buddy in the next pilot's box. You have no way to turn the tailwheel. Do you throttle up and rudder over hoping that the plane will finally turn before it hits him at full throttle? Or do you throttle back, meaning you have absolutely no rudder control, ergo, no steering? So you hit him but not quite as fast. Or do you rethink this and find a safer way to control your airplane while it is on the ground?
Please think about safety in addition to thinking about what's easiest to build. A .40 size airplane can cause severe injuries in a botched takeoff attempt.
You need to have positive control over your aircraft at all times. This means on the ground as well as in the air.
This isn't just theory. I've seen it tried and it wasn't pretty. They eventually went back and found a way to control the tailwheel. But that was after breaking the airplane a couple of times. Thankfully, there were no injuries but it was close on the second accident. An out of control airplane is a scary thing.
Dave
Your plane with a castering tailwheel is ready for takeoff and there are several other pilots on the flight line. You throttle up to take off, there's a crosswind and you find your plane heading towards your buddy in the next pilot's box. You have no way to turn the tailwheel. Do you throttle up and rudder over hoping that the plane will finally turn before it hits him at full throttle? Or do you throttle back, meaning you have absolutely no rudder control, ergo, no steering? So you hit him but not quite as fast. Or do you rethink this and find a safer way to control your airplane while it is on the ground?
Please think about safety in addition to thinking about what's easiest to build. A .40 size airplane can cause severe injuries in a botched takeoff attempt.
You need to have positive control over your aircraft at all times. This means on the ground as well as in the air.
This isn't just theory. I've seen it tried and it wasn't pretty. They eventually went back and found a way to control the tailwheel. But that was after breaking the airplane a couple of times. Thankfully, there were no injuries but it was close on the second accident. An out of control airplane is a scary thing.
Dave
I teach students to always control the plane, if you are controlling the plane the first few degrees you see it off coarse you put in the correcting inputs and it responds. If it does not respond something is wrong and you should shut down. I think that just about covers it.
When I am hovering the flow of air over the rudder and elevators easily moves the the tail forward and back left and right. Similarly when starting a takeoff and taxi rolling at slow speeds with the tail down little blips of the throttle move air over the rudder and I can and do point the planes nose in what ever direction I choose. Remember the grass presents fiction that requires force to over come.
The OP says he is working on a Big Stick ( sticks have about a 50 50 ratio of fixed vertical to rudder).
One note when I decided to reply in this thread I went in the shop and counted the tail dragging planes hanging up without steerable tail wheels. The count was 5 out of 8. On two electrics there was one fixed wheel and one skid. One of the planes has 1500 flights and no problems Kyosho Cap 232 OS .91 fs. Not hanging there because it in the car for a trip to the field is my .60 size stick (that would have been 9 if it was in the shop). That is me and it in my avatar pic. It has over a 1000 flights as well. It is powered by a Zenoah 20cc gas engine swinging a 16 x 8 prop. So believe me you have to respect its nose. Its not the largest of my free wheeling tail wheels, one is a 50cc DA swinging 22 x 8. That is 5 horsepower in a 16 lb Yak handles easy if you know what to do.
One plane that me and my buddies had some fun with on a very windy day was a PT 60 with an OS .70 fs. A Tricycle gear with tons of dihedral and a very large fixed vertical fin to rudder size and throw (The nose gear was streerable). That trainer was difficult to nearly impossible to handle in a strong cross wind because of design. The Cap and the Stick were not again because of design.
I am not saying that full castering tail wheels are my favorite choice. But for use off grass fields like where I mostly fly on planes without dihedral and large fixed vertical stabs they present no problem to me in wind conditions that scare the largest number of pilots out of the air (90 degree cross wind over 20 mph). And are handled very safely.
I find that unless you are willing to fly under these types of conditions you never get a chance to fly backwards to respect of your ground position or do a stationary rolling harrier.
Wow that "s__ety officer" thing really got me typing.
Last edited by kmeyers; 11-10-2015 at 06:39 PM.
#28
Join Date: Aug 2002
Location: Cisne,
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http://www3.towerhobbies.com/cgi-bin...&I=LXFV47&P=ML
Cary
#29
My Feedback: (1)
For what its worth and whats been under discussion is the Sullivan (or most conventional tailwheels will not work on any ugly stick with out abandoning the spring an resorting to an extened vertical rod soldered to the spindle of the Williams and the ninety degree bend at the top of the rod that is inserted into the rudder would require the rudders removal to install. That's the kind of modification work the OP is trying to avoid.
Two options are a simple tailskid or solidly fixed tailwheel which work well on the OP's airplane (free swivel or limited free swivel on the OP's airplane does not work well. The second only practical option is a conventional tail wheel with a side or T tiller and a second pushrod to the opposite side of the rudder servo or possible clamped well forward with the air rudder pushrod.
John
Two options are a simple tailskid or solidly fixed tailwheel which work well on the OP's airplane (free swivel or limited free swivel on the OP's airplane does not work well. The second only practical option is a conventional tail wheel with a side or T tiller and a second pushrod to the opposite side of the rudder servo or possible clamped well forward with the air rudder pushrod.
John
#30
My Feedback: (1)
This photo of one of my ships illustrates two methods of double pushrods. In this case the upper servo with two rods is the rudder and the rods go to separate air rudder and tailwheel.
The lower servo in this case illustrates two rods clamped together with wheel collors for separate elevator halves but the same method can be used for air rudder/tailwheel rods.
Either of these methods can work well for your ugly stick.
John
The lower servo in this case illustrates two rods clamped together with wheel collors for separate elevator halves but the same method can be used for air rudder/tailwheel rods.
Either of these methods can work well for your ugly stick.
John
#31
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Join Date: Nov 2010
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This photo of one of my ships illustrates two methods of double pushrods. In this case the upper servo with two rods is the rudder and the rods go to separate air rudder and tailwheel.
The lower servo in this case illustrates two rods clamped together with wheel collors for separate elevator halves but the same method can be used for air rudder/tailwheel rods.
Either of these methods can work well for your ugly stick.
John
The lower servo in this case illustrates two rods clamped together with wheel collors for separate elevator halves but the same method can be used for air rudder/tailwheel rods.
Either of these methods can work well for your ugly stick.
John
Believe it or not my brain was running through that idea earlier today.
Now I see that it works.
Jimmy
#33
I flew my Giant Big Stik for a couple of years with a free castering tailwheel on grass and it was ok unless you are taxiing with a crosswind. With a crosswind, I could not taxi it. i eventually put a small Hitec HS82MG with pull-pull wires steering the wheel. The Great Planes Big Stik series are designed to accommodate a steerable tailwheel if you assemble the plane with a taildragger setup to begin with. The fuselages have a notch at the tail end that you can cut out to pass through a tailwheel wire. I bought my Giant Big Stik used and originally built for trike gear and then modified to taildragger. So, the previous owner did not take the opportunity to build the steerable tailwheel to begin with.
#36
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I have decided how I'm going to do this, I will use the FORCE.
Well ok, this is how I will do this.
Servo on bottom of fuse, rod to tail wheel.
Can I use a Hi Tec micro servo for my throttle?
Jimmy
Well ok, this is how I will do this.
Servo on bottom of fuse, rod to tail wheel.
Can I use a Hi Tec micro servo for my throttle?
Jimmy
#37
My Feedback: (1)
I have done this on a few airplanes and it does work usually plugged through a Y harness with the air rudder or a mix argualbly there is no real advantage to using mix other that electronic independent rate control.
The down side of course is the same as discused before putting a second servo on the side and that of course is the extra weight that far aft on a small airplane.
If what you mean by micro servo is the Hitec HS80/85 series on throttle the answer is yes they work ok for throttle if you ca accept the plastic gear version strip gears rather easily even on the throttle during had landings or otherwise firm arrivals.
John
The down side of course is the same as discused before putting a second servo on the side and that of course is the extra weight that far aft on a small airplane.
If what you mean by micro servo is the Hitec HS80/85 series on throttle the answer is yes they work ok for throttle if you ca accept the plastic gear version strip gears rather easily even on the throttle during had landings or otherwise firm arrivals.
John
#39
My Feedback: (1)
They are fine especially on your small stick. Actually My all time favorites are the HS 225 minis plastic or metal. I use these even on ailerons of typical sixty sized airplanes that have two aileron servos. have used them on rudder a lot and of course throttle.
In the case of most ARF's they usually have large servo tray holes for the so called standards and where I use a 225 I just cut a stick to cross the servo hole and allows the servo to be screwed down.
John
In the case of most ARF's they usually have large servo tray holes for the so called standards and where I use a 225 I just cut a stick to cross the servo hole and allows the servo to be screwed down.
John