Main Gear Suspension options?

[Sid]

Just after a bit of feedback about the suspension setup on the Bearhawk models for Bush plane type work.... it would appear to be very aerodynamic in comparison with most cub or Superstol options but how robust is it, and how forgiving in comparison.. ?

The just superstol is obviously plush but added drag, complexity and weight? I quite like what they do with the tail wheel though and that might be an improvement worth considering?

Any other systems worth thinking about or is standard good enough...

I am thinking Patrol with 26-29" rubber...

[Gavin Chester]

Similar tail wheel to a YAK

[Battson]

It works very well. We have been some rough places in the last few days, and combined with some oversize tires it really goes to work on rough surfaces.

Possibly the only downside is it doesn't cope with large side loads, but there is a simple mod to improve that.

[Sid]

It would be a pity to lose the aerodynamic advantage, and if reliable/functional enough for purpose I would prefer to stay with the stock design for the front. Added complexity and weight is not the end game.I just look at the tailwheel design and think its pretty uninspiring from an engineering perspective. There doesn't seem to be much in the way of recent thinking in some of this stuff. The advent of lightweight suspension systems in motorcycling, mountain biking and other areas could provide progressive damping and less shock/vibration at both ends..

Justs large hydraulic suspension aint the last word here of course.... for weight and drag reasons, but a small damped and sprung shock absorber mounted top side of the gear centrally just above(or below)the pivot point and enclosed could well provide all the advantage and little of the downside if faired and enclosed.

That and tied and chained tail wheels and linkage to rudders seem unnecessary and another maintenance issue...

This is not intended as criticsim, but coming from a non-aviation perspective, things often look historic when you consider the speed of development in other areas...

Often there are good reasons why, its probably healthy to also ask why not.... I am interested in both....

Cars and motorbikes were all unsuspended at one point, then they were all sprung, then they were all damped and sprung. We would think it odd to suggest that we should just spring or just dampen our vehicles today. The seeming generally accepted idea that small planes should bounce down the runway, taking off or landing seems to be more part of the culture of aviation than a reason to innovate?

Help me out with this, which end of the stick have I got?

[whee]

Car and motorbikes are ground vehicles so it makes sense that they have good suspension systems. While very cool, the suspension system on the SuperSTOL is unnecessary. I think a large soft tire is the better way to protect the airplane during rough off airport operations. A radical suspension won't help with rolling over big rocks and potholes but a large tire diameter will. I'm in agreement with F.E. Potts, author of "Guide to Bush Flying," touchdown in the off airport environment does not need to be any harder than on a paved surface. Plunking it on as demonstrated in many STOL videos is just not necessary. Check out Battson's videos; he sets it down nice and easy wherever he is landing. That being said the stock suspension on the Bearhawk does a great job absorbing a botched landing; it is sprung and dampened. Even with my poor pilot technique I don't go bouncing down the runway. I've splatted down pretty hard and the gear had plenty of spring and damping to absorb it and not bounce me back it the air. Bob did a great job designing the suspension system.

A shock absorber on the TW is also unnecessary IMO. Just more weight and complexity it one of the worst places to have it.

The great thing about EAB aircraft is you can build it how you want it. You want a huge travel suspension system go for it. I'll come drool on it because I love that kind of stuff but for me and my airplane I don't want it. I just don't think it is needed for real world off airport flying.

[Sid]

No I don't want huge travel, and I don't want to slap anything down as a matter of course. I would be more interested in control and rough ground ride, and reduction in shock and vibration. Just provides 10" or 12" shocks for the superstol, which give a heap more travel at the wheel... its a massive amount...

I appreciate that an aeroplane is only on the ground for a short time, and that it's not its core function... but it would be fair to say that not many have been using modern designed suspension systems on their planes. I wonder if they would still have the same attitude if they had been. History is littered with stories about the unneccessary development of things, that were deemed to soon fail; those same things that have become normal and when looking back, we all wonder how we existed without said "improvements." We are of course talking about off-field mission.

The feedback from those in the Superstol that I have seen is pretty positive in terms of the ride across rough ground and the control that you seem to have. I would argue that long travel progressive suspension does allow smaller rolling diameter for similar outcome, but where the ideal component match would be I have no idea. It is certainly true of dirt bikes for example, large obstacles can be negotiated with small wheels at speed with the mass of the bike remaining stable and level. This is all down to suspension. Essentially bush plane aviators are mitigating shock, impact and vibration by increasing wheel size to achieve the same thing. This is also an increase in weight complexity and drag, and cost.... In one respect there is nothing new in this...

The problem long since addressed in dirt biking is that increasing tyre size reduces control, becomes more wallowy, has greater rotational mass and greater weight. Increasing suspension performance and keeping rotational mass smaller is a better option particularly for bikes, that need to change direction, stop and accelerate.... less of an issue perhaps for planes..

I would expect that the Superstol tailwheel design will probably be lighter that many leaf spring/solid steel bush plane setups that I have seen on bearhawks... it is a pretty straight forward design. Its certainly something that I will look closely at come the time.

Thanks for your feedback on how Bobs suspension works, just out of interest how much wheel travel on the main gear do you have with Bobs system?

[Mark Goldberg]

Just a brief comment here. Sid - your posting has to do with modifications to Bob Barrows designs. I suggest first that you ought to buy a set of plans and see how Bob's designed shock struts and landing gear work. You see on this forum all the off airport use these planes are getting. The gear is quite strong and forgiving with the oil dampened spring shock struts. When you start modifying things, you might not end up with something better. Just my 2 cents worth. Mark

[Gavin Chester]

Modified Super Cub version.

https://m.youtube.com/watch?v=YPFMXB59Gyw

[Gavin Chester]

Pictures