Our X-plane (beta version) is still available for a free download, but as we advance the model, it may disappear from the ‘free’zone (so get it while you can). Most of the aerodynamic engineering predictions on flight characteristics that came from DAR Corp match what we found in X-plane, and that is another validation of the design. Stall speed, stability, cruise speed, and trim changes all were in line with predictions, even though X-plane bases flight on the physical parameters of the plane and not through derived parameters (ie, you can’t tell it to stall at a certain speed – it stalls when the wing runs out of lift, just like it would in real life).
One thing we are not happy with is that when we drive it off the airport, the program automatically tells the vehicle it is ‘in the rough’. That has meant that even while on roads, the vehicle is bouncing like it is on a grass field. Understandable in a sense, as this is a Flight Simulator, not a race car program, but still not what we wanted to have happen. We are trying several ways to handle this, and if nothing else, will establish some scenery upgrades for download that you will be able to drive around on after landing.
Flight characteristics of the model are still fairly good, though it does exhibit more power related trim adjustment than we would like. One reason may be the way we modeled the ducted fan outlet. In the real vehicle, there is a lip projecting outward from the lower portion of the duct, which serves both as bumper on the ground, and to provide an unbalanced ducted fan outlet to counter the power related trim. With power on, the prop will tend to push the nose over. With the lower lip in place, we expected to counteract that by the prop wash acting on the lower lip aft of the propeller.
The X-plane model, however, has a straight duct end, and doesn’t get that benefit. What you ‘see’ in X-plane shows the vehicle like we designed it, but that is only graphics. The computer model is invisible beneath the graphics ‘skin’, and has a straight duct end. We will work to change that in the future, and if it makes a difference, we will let you know. Landings are just like we predicted, with the nose coming down smartly and the vehicle ‘driving’ from then on. I like this, as there isn’t the in-between flying and driving period of typical aircraft – it is either one or the other. Please let us know your experience with the vehicle by posting to the Contact page. You can be our unofficial test pilots.
The ground testing continues, but is nearly done. We will post a Youtube video showing the test vehicle driving by at something like 40 mph, and then flooring it and burning the tires as it accelerates away. We did this once already, and it is impressive! The vehicle is stable and fun to drive up to 74mph (fastest we have tested so far). The current rear springs are being replaced with compound springs to soften the ride but still provide stiffness for landings. We went from almost Cadillac softness to Rocket Sled! Somewhere in between the two lies the sweet spot we want. Regardless, you are going to really enjoy the ground ride on this vehicle. Porsche will have nothing on us!
One thing we did which was very successful was to change out the chain drive to belt drive. What a difference! Now we can really ‘get on’ the engine, and apply almost full power (full power spins the wheels almost every time). The whole drive system feels completely solid and quiet. We are very impressed with it, and will continue to try to break something to spot where the weakness lies. So far, no breakage, just exhilaration and acceleration.
Our last suspension system to test will be a torsion bar system, front and rear. This will handle the front end much more easily than other methods, but we have to keep the weight reasonable. We can do it the way we have been so far with motorcycle suspension, but if we can keep the weight of the torsion bar system in check and still provide a robust suspension with this, it would be easier to install and maintain.
We have some exciting news coming up. Negotiations are underway in a couple of key areas that will benefit the project and our overall business footing as well. I hope our next newsletter will be able to share some of the things we have been working on for many long hours to bring into being.
Happy Labor Day
To you and yours
The Samson Team