Tweet
This has probably been tried before, but I"ll ask anyway...I was thinking the other day about roll overs and why they happen, some in part can be due to the wheels digging in, either at front or sideways.I got to asking myself "why can"t we make the mains caster the same as the front wheel, so that if the machine wants to tip over sideways it will merely roll, rather than trip over?"Taxiing would be more akin to flying than with a fixed mains wheel set, and if you wanted to make them partially fixed you could set them up so they centre themselves at straight ahead but will "break and caster", not brake and caster with an appropriate amount of sideways force. It would be like driving a shopping trolley until you got used to it. I suppose it would be more like a hovercraft on the water until you had sufficient air speed to make the rudder work properly.Can anyone see the benefits and failings of such an idea?Cheers,Nic.
-
-
I can see your logic Nick although I"m not sure that a gyro set up like you are contemplating, wouldn"t be a handful. I know its okay for me to say it but I firmly believe that with correct training, a bit of coordination the tip over should never be a possibility. I have been in some different situations and bent my share of gear but have never felt in danger of a tip over even in the earlier stages of learning..
-
I can see your logic Nick although I"m not sure that a gyro set up like you are contemplating, wouldn"t be a handful. I know its okay for me to say it but I firmly believe that with correct training, a bit of coordination the tip over should never be a possibility. I have been in some different situations and bent my share of gear but have never felt in danger of a tip over even in the earlier stages of learning..I"m with Brian, Training is the easy answer.But I think I know how we can DESIGN a gyroplane to be rollover proof!!!!!!!!All we need to do is look back at the very fist gyro, and its design features.Cieva"s C4, it had a fixed rotor, so pitch was via an elevator, roll was via ailerons, and yaw via rudder. Sounds very conventional dosnt it. Well I guess the other feature of the ailerons would be they could also double as anti rollover paddles, AND flyovers (forgetting the rotors are still flying/alive) during, and after a flair would be a thing of the past.
Comment
-
Brian, Sam,I"m going to introduce a terminology here - I will call it "mains caster", where the mains are allowed to twist and align themselves with a new direction of travel.I don"t disagree with either post, training is the answer based on the current design, but let me put this question, if a bloke who has 1000"s of hours of flight and instruction time can flip a gyro over with a side gust because his mains would not "caster" and slide sideways - instead they dig in and tip the machine over [ I refer to PB"s prior tip over on taxiing ] could this incident have been prevented by a modification to the design such that the gyro would caster and slide in preference to braking and rolling over? If the side elevation area favoured the tail such a machine would caster on its mains and weathercock into the wind on the tarmac. It could be a little dramatic, but not as damaging to the machine or the occupants, surely if it were to stay on its wheels rather than flipping over..For a design what I am thinking of is something like a fridge hinge, or on similar to toilet cubicles, where the wheel is set with definite caster - say 4", the weight of the the machine on the mains makes them bias toward steering straight ahead, see the arrangement below. Any significant sideways force would make the caster overcome bias to steer straight and would result in the machine sliding sideways... taking off in a crosswind would be similar to flying the machine off the ground, the same inputs would be required to flying crosswind in the air.What say you now??Nic.
Comment
-
Nic,Your idea is similar to one that was tried as a mod to the main undercart on large tail wheel aircraft around the 60"s to minimise ground looping. It is my understanding that it never took on because of the lack of acceptance based on the view that the conventional design approach was simple and easily managed as long as the pilot had good training and maintained currency by regular pratice. That said the great thing about experimental aviation in OZ is that we have the freedom to tailor our own aircraft to meet our personal desires- so if you think it is a good idea try it! My only advice is to become experienced and proficient as a pilot on conventional designs before you start test flying major mods to airframes and control systems.Just my 10c worth,Adrian
Comment
-
Adrian,Thanks, I"m assuming it would be the DC 3 that this may have been tried on - it being the most popular around that time and having flown in a few as a kid I knew them well.Any other takers on this one?Cheers,Nic.
Comment
-
Hi NicMy post was tougne and cheek.As per pure castering mains, well I see it having reduced control by the pilot. It would be like controlling a shopping trolley, imagine you have just flaired and stopped, when suddenly a side gust hits. Even though you have applied right stick into wind, it would cause the machine to rotate "weather ****" into wind as it strikes the tail, and even possibly blowing you across the runway into the runway gutter, eventuating in a rollover anyway.SamL
Comment
-
Sam,Thanks, anything is possible, I got to wondering who would be silly enough to put a gutter on a runway ?? Who would be stupid enough to make something that was hazardous enough already even more so by putting a big bump where aircraft are landing... oh, yeah, sorry... bureaucraps would.If you"ve come to a halt then the full weight of the machine would be on the mains and it most likely would not caster due to this - although the castering force may be varied by the angle of the cut on the cylinder in my prior post or from any extra pressure you might choose to apply to the assembly through the use of a preload spring or similar, not to forget the possibility of brakes on the gyro holding it in position. It would be a ferocious gust to push a machine sideways though.I would concede that this might happen if you had come to a halt and then decided to taxi back to the hanger with your rotors still going at near full tilt, but as I said you would most likely then be "flying it on the ground", so a side gust may weather **** you but at least [if you were still in flight mode ] you should react appropriately and compensate with power / rudder /steering. If it weather cocked then the tip over axis of the machine all of a sudden becomes significantly bigger than sideways across the mains so the tip over possibility is reduced and with significant input from the pilot even less of a risk. If there were a gutter there a side gust which results in an excursion would be a problem no matter if your mains are fixed or castering.My idea is as Adrian puts it, there to avoid ground loops and the likely tip overs associated with same, so there would be significant "rudder speed" which hopefully would result in sufficient control for the pilot to "fly it" out of trouble, even with the machine in full undercarriage contact. As with PB"s incident for the gyro to flip over it must become light on its mains, if they happen to break out and caster, the tip over moment is lost as the bottom of the machine starts to slide
Comment
-
Hi Nick,Always enjoy reading your ideas....
Comment
-
Paul,That"s a f"ing brilliant idea! I like it too..One thing though, if the left wheel acts as a brake while the right side slides, how does that affect the
Comment
-
Another consideration is cross wind take off. I have many atimes taken off in a 15-20 knot cross wind. Why, because there was only one runway. The issue is during take off the machine is balanced on its mains while you keep it traking straight down the tarmack with rudder. Then on breaking ground the machine weathercocks nose into wind. Now what would happen while balancing an your catering mains, prior to lift-off????Sam....
Comment
-
Sam,Acknowledge that point, that is what I referred to prior as "flying on the ground", where your inputs are the same as per in flight responses, you would probably be in the right shape by the time you got off the ground because your rudder and stick inputs would be close to if not near right for when you do break ground.. What would your inputs be in such a situation - can you work through it in your imagination Sam?Not forgetting there would be a break - out torque on the castering where it did and did not have steerage, you may well just have full flight control of the situation before that point is reached and be able to react much as you do now with the fixed mains.I"m exploring this for all that it is worth so if you can work it through in your imagination and try to envisage the stick / rudder / power inputs you would have then I would like to see that here, if not for me but anyone else who might be considering the concept.Thanks,Nic.
Comment
-
i have already put castors on as main frame wheels. only to work on my machine in the workshop, usually to work on main frame and/or spar and wheels. its another steel box about 1.5 mt long with the castors bolted on the ends. i bolt this[clamp] under my keel.at just the correct height to hold my main frame wheels off the floor. i"ve done this to set up suspensions and such so it won"t fall over on my head while working on it without hanging from a crane.
Comment
-
Nick,did you ever ask your wife how difficult it is to steer a shopping trolley, or better yet try paddleing a canoe in a cross current with a head wind from the rear seat in the canoe.you may get an appreciation of the forces involved!What you are suggesting is pure folly. If you are worried about a "wheel digging in" try looking at the specially designed , tuned length, wind direction meter that we commonly call the "piece of string".Should any of us have a worry that we may dig a wheel in, we are either trying to land in a bog, loose sand or a wheat silo. If this is the case, Make sure that the string is pointing directly towards you and try to ensure that the landing speed is appropriate for the surface that you intend to land on.In most other cases, try to land on a grass strip as many times as possible before attempting Bitumen or other such scary surfaces.After some time not flying since my last mouthfull of dirt and the subsequent rebuild, I was not too proud to seek out an opportunity to get some hours up in a two seater with someone to rebuild my skills, Time and effort well worth the choking gulp of pride.why on earth would anyone want to extend the transition stage from takeoff to flying to being at the mercy of cross winds in a powered shopping trolley, I couldnt begin to imagine?!Use your string!Mark.
Comment
-
Gents,Thanks, but - can you answer these questions?For all to answer - this could be interesting:Would you be flying in conditions like this anyway? Most likely I wouldn"t...but you might have flown cross country into this.How would you instinctively react if you had fixed mains and you"re tipping to the right from a left gust?Would full right rudder to go downwind get you out of trouble if you turned right and bought on full back stick to shut your rotors down? [watch the gutter!]What would you instinctively do with a castering main if your machine started to tip over to the right and then started sliding sideways to the right and then tipping back to the left and then turning left once the mains started to caster? [sounds complicated but this is probably what would happen]How would you handle this in a tail dragger gyro like a Cierva gyro?Please oblige - how would you handle it??Mark - I"ve driven a shopping trolley myself, possibly many more times than you could imagine, seemingly - with the right application of power and vector they are no problem at all - just shove in the right direction and they go. No point asking a woman how to drive a shopping trolley, you"ll end up having a heart attack over the prices of the goods therein... even if you don"t have the HA you still wont have a hands on idea of how to drive one.The string can be misleading, as it gives you the vector of the wind on the string, not the vector of the wind on the ground, not forgetting that PB had one of these too - why didn"t it work for him? As you slow down the wind - if a corss wind presents more prominently from the side - why is it so - because the wind from the front slows down..Thanks,Nic.
Comment
Comment