How far should it tilt

[Doon1]

Hi Guys,
I'm new to this forum. I have a small flight chair set-up now that can be seen here http://forums.flightsim.com/vbfs/showthread.php?t=193685 I ran across first the skyflyer and then found thanos' website (very cool). So I've decided to build my own.
I've gathered most of the parts I need to build my platform but I was wondering just how much tilt i should build into it. I'm currently designing it with 60 deg. of movement (30 deg each direction) but could go less or more as needed.
John

[autocadplease]

The more the better - obviously! But in real life commerical pilots usually try to keep all banks to 20 degrees or less - for passenger comfort. 30 degrees each side should be good. I would think anything beyond that gets to be a problem in design / construction?

Love your setup too!

[ANDYSMITH]

As long as the "ball" is in the middle you will not need any side tilt during an even rather steep bank angle as there is nothing to simulate. From my two rides in a real sim the most you will feel is aout a 45 degree nose up on takoff roll to simulate LOTS of power on accelerating, and it feels like it is really pinning you back in your seat. And roughly the same for braking on landing, nose down about 30 degrees. Other than that not much movement at all. Big shudder when the wheels touch, constant minor shaking to simulate turbulance.But no side tilt unless uncoordinated flight.
Andy

[Doon1]

Thanks guys,
I got my flight training about 20 years ago. I remember doing 30 deg. turn around a point manuvers. There was a lot of tilt feeling while going into and coming out of the turn but there was also some while in the turn (bubble centered).
I just fly GA in FSX but I also fly IL2. Hopefully 30 deg will be enough. If not then I can (fairly easily) modify it to add extra rotation.
Several years ago I designed a chair that had 360 deg. rotation on both axis' but that would probably be overkill.
John

[Doon1]

Not to mention cost prohibitive.
John

[Roland]

Andy is right:

Allow bigger pitch angle for more acceleration feeling. Ian's site (buggies build for fun) has some explanation about the physics behind the tilt angles.
Roll angle can be much less, unless you plan to do a lot of high-speed steering on the runways.

[Doon1]

Thanks Roland,
Ian does have a great site. I've been there several times over the past year or so. I even downloaded the plans for his first platform that mounts to a wall. There's a nice piece of work.
My goal is to keep the entire platform under 26" wide. I will have sliding outriggers that will be deployed to maintain lateral stability whilst flying. I guess I'm undecided as whether to build a 3 point actuator platform that has heave or build a single universal joint platform that I can build with the junkyard parts I already have. The junkyard has an "everything you can carry for $50" day the first Sunday of each month. The single point system would require less part fabrication and uses no wooden parts which is a plus in my book. Heave vs. ease of fabrication. I just don't know. If anyone has experience with both types, 3DOF and 2DOF, I'd love to hear from you.
John

[Matt_Thomas]

Yes, like everyone is saying pitch is more important than roll (tilt). In normal coordinated turns in real airplanes you don't find yourself leaning against the door very much.

However, I think some roll movement is important. Personally, when I stand outside and watch a 2 DOF simulator, it just feels like a lot is missing. I just expect to see the thing tilt right and left a little, even if I know it's not 100% realistic.

[Roland]

Some roll tilt angle is definitely required. What's important to realize is that during most aircraft manouvres, there isn't a lot of sustained lateral force. (Driving circles on the taxiway would be an exception, where the continuous centrifugal force would keep pushing push you sideways).
The funny thing about a fully enclosed motion sim with good visuals is that your brain is easily fooled: you don't need a lot of platform motion to get a good feeling of acceleration, aircraft roll, ect. So when you look at a motion sim from the outside, it seems it is not doing a lot. However, the people inside may have a completely different experience, as they have no outside reference, and good visuals will do a lot to enhance the feeling of motion. Bigger platform movement easily leads to wrong cues, and these will quickly lead to unrealistic aircraf feeling.

So less platform movement is often better than too much.

[Doon1]

Hi Roland,
I have really enjoyed your site. Very informative. It seems as though your platform doesn't have a lot of tilt yet, like you said, it seems as though the effect is very realistic. How much tilt does your platform have? I didn't that find that spec on your site.
John

[Roland]

Note my 3DoF platform is a 3-point system.
The total actuator range of each actuator in my setup is about 45cm.
The platform base length between left-right and front-rear is 1.6m

From this you can calculate the max tilt angles: about 15 degrees for both pitch and roll. I will never use this angle with roll, but for B737 or Kingair full power take-off, you would like to use the full 15 degrees pitch. But I want to keep a bit actuator travel margin for runway bumps (heave), so the actual actuator full pitch travel is about 40cm (front 20cm up, rear 20cm down =14 degrees)

To have more actuator travel for rotation+heave at lift-off, the take-off acceleration has some washout. (can be tuned with Ian's BFF driver)

From the above you can easily derive the platform tilt limitations of a 3-point system.
Bigger distance between the actuator points will reduce the max angles, unless you increase actuator travel. In an 8-bit system, actuator travel cannot be too much or you will notice the steps. Less distance between actuator points means lower angular accelertion.

Ian's first platform had independent DoF, that can have much bigger tilt angles w/o limiting heave excursions, but it was more complex to build. So it's always a compromize between platform complexity and performance.

[Doon1]

Thanks Roland,
For starters I've decided to build a 2DOF. I will be building it with a heave function that will/can be added later that will be totally independent of the pitch and roll functions. I doubt there is software for this but maybe I can get one of you programming genius' to help out with that when the time comes ;) . I've aquired all the parts I need and am in the processes of refining my CAD drawings so I can begin the build. I've allowed for 30 deg. pitch in each direction but will, from watching your videos and what you've said, probably only use a portion of it's capabilities. Well I'm back to drawing.
John

[Roland]

For starters I've decided to build a 2DOF. I will be building it with a heave function that will/can be added later that will be totally independent of the pitch and roll functions. I doubt there is software for this but maybe I can get one of you programming genius' to help out with that when the time comes ;)
John

Ian's driver software allows you to select independent pitch/roll/heave. Good idea to start with 2doF, and keep possibility for 3doF. That's the way I started as well.
Please keep us updated on the progress.

[Doon1]

Ok, the first design ran into constraint issues that presented themselves once the 3D model was finished. I was disappointed but a design rarely works right out of the gate. I was at work and was thinking of different options while cleaning my work bench (I'm a Ford Service Technician) and behold there on the bench was the answer to my problem. So 12 hours of design work and 3D modeling and viola a workable design that fits my size constraints with only 2 moving parts (plus the 4 motors of course). It's in fact MUCH better that the original design. As it's designed there is 60 deg. of motion for each the X and Y axis. I can make it more compact ( which would be even better) if I loose some of the motion. As I want this to be both a flight and driving sim is 60 deg overkill? I hate to keep asking this but I haven't asked about the driving sim motion needs.
John

[Doon1]

I forgot to add that there is actually 70 deg motion for each axis but I'm allowing 5 deg room for each direction before the hardstops are reached.
John

[wannabeaflyer]

Hi John .. have been around this forum for awhile now and am still Faffing about with my 2 DOF motion Cockpit but wanted to ask a general question .. What will you be using as actuators ..Linear or Rotary ? am having to look at DIY soloution for a More Powerfull Motor to drive my Current actuator setup.. which is a Power steerng rack from a BMW and a Steering Box as Per Jims design .. both of these were driven by Wiper motors and proved the concept worked but as the Bodywork gaot built up and Joe blogs put on weight i soon found that i needed something Beefier and am still not at the stage of being able to cough up £500.00 eac for decent off the shelf gearbox motor combos.. by the way guys and this is an open question :-) what sort of inches/mm per second is generally required for platform movement.. seriously looking at screw jacks as a means to move my Pitch/ Roll axis but seems speed is a factor i need to sort out. By the way my system was able to Pitch and roll to just under 20 Degrees and that was limited by The Universal Joint the platform was mounted on (a BMW Prop Shaft Universal Joint ) and the Actual Throw of the Steering Rack .. My Cable and Pulleys seemed fine with the load just tooooo slow under load ( Poor Motors :-( )

[Doon1]

I too am curious about what the recommended deg. per sec. rotation rate should be. I've done a loaded test of my drive element and am getting 90deg rotation in 1.7 sec. Is this too low?
John

[Roland]

For normal flying, the pitch and roll rate don't need to be so fast. For other dynamic effects, (turbulence, runway bumps, touchdown) actually the small signal angular acceleration is more important than angular speed. (dynamic effects are normally small excursions, so how fast can you platform start a roll is more important than the max speed of the actual roll) motor rpm and gear ratio have impact here. Another important thing to keep in mind is the reversal capability of your platform. Small dynamics require continuous reversal. Put a sinewave on your axis input (making is wobble a bit) and see how the system responds when sine frequency is increased.

Have a look at my platform #2 pages for angular acceleration calculations.
Keep in mind: Car simulation requires much more dynamics than airplanes. Maybe Thanos can give more input here.

[wannabeaflyer]

hi guys thanks to link on e-bay my pocket is now £76.00 lighter found these and had to give them a try if all elses fails i'll put them back up for auction but seemed to good to pass up so bought 3
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... %26otn%3D2 have seen this guys work and even though the motors are slower i think they have possibilties for my sim
http://www.youtube.com/watch?v=MxXEOcYY1M0
I realise the motor speed is very low but thought there may be scope for Gearing up ... i know i'll loose Torque so its another trade off but at the price i had to give it a shot :-)

Guy's would appreciate any pros , cons shoot me down but not in flames feedback :-) not too hot on the maths but they are 51Nm torque output so im hoping for in excess of 200Nm when the leverage is at 250mm ... chain drive ?? to increase speed but will loose torque :-( open to suggestions :-) Cheers for any info in advance