flug wrote in Thu Mar 16, 2017 5:45 pm:
....................
FWIW I seem to recall that one of the issues early on with this model was inconsistent ground reactions, and that part of the solution was moving to 120 hz FDM rate and also making some other adjustments.
One of the issues with a model like this is that the original aircraft didn't really have any suspension per se. It's just a hard rubber tire mounted to a wheel, the wheel to an axle, the axle to some bracing, and the bracing directly to the aircraft fuselage.
So it's not like any more modern landing gear where there is likely to be some kind of damped spring arrangement that has X inches (or even feet) of compliance built into it.
Rather, with an aircraft like the Camel they were depending on the 'natural' inherent spring of the entire system--tire, wheel, axle, bracing, fuselage, etc--to absorb any forces. This is hard to get your head around modelling but more to the point of JSBSim, the entire system seems to act pretty much like a very short, stiff spring with quite a bit of damping and that is the very type of thing that JSBSim with its relatively slow modeling rate is going to have the most difficult time with.
..................................
It amazes me that you have spent so much time and effort in getting this plane's FDM historically accurate, and yet you can't bother researching further about WWI aircraft landing gear suspension.
All WWI planes had some sort of sprung suspension, be it either shock cords, coils springs or torsion bars or shock corded Oleo struts, no exceptions. These planes all flew off of rough grass fields and the technology for landing gear suspension was already available long before the Guns of August. You only need to load up Helijah's Bleriot XI and watch the castoring and shock absorbing complex of struts and wheels while it taxis across a grass strip. These early suspensions did not have much if any damping, so they were quite active and bouncy on rougher fields. So take that into consideration when adjusting your FDM.
Another thing: WWI aircraft tires (tyres) where pneumatically inflated, just like bicycle, car and motorcycle tires of their day, and used latex rubber and fine threaded cotton or linen casings/treads. They were meant to be very light. Hard rubber tires are really heavy.
Not having suspension on any aircraft that has to taxi up to a take-off speed approaching 40 to 50 mph is asking for a lot of damage to the airframe if the ground is really rough. The 'natural give' of the airfarme will never give enough without some kind of failure.
The Bleriot XI was first flown in 1909, with a working wheel suspension. In fact there were very few pioneering aircraft that did not have some sort of rudimentary L/G suspension. The Camel had a pair of V struts tied at their bottoms with an elaborate weldment, supporting two axles wrapped in shock cording at their pass through holes in the bottom of the V struts. You could have easily found this out by registering at the Aerodrome Forum and asked a few questions. There's a number of people around the world that restore original and build replica WWI aircraft, they might even be kind enough to send you images of their own work.