2 motor flight sim rig with centre universal joint.

i am getting there with my design. 2 motor as in title. i have a question about the centre universal joint. i was going to use a car or truck one but from reading others designs it seems that they only have about 18 degrees of movement. this would be fine for cars but to be realistic wih aircraft you need at least 30 degrees for a airliner or GA aircraft. even more for military fighters and helicoptors. how have people got around this apart from going for 6 dof. there are industrial joints that would work but they are very expensive.

Hi Bob
I designed a UJ Joint, and had some brackets manufactured by a company called Lasermaster in Redruth, the assembly uses a Land rover UJ Joint.

This alows me to have 45. deg of movement on my sim in both pitch & roll.

Large angles don‘t necessarily make a simulator more realistic. You would just have the angles, but not the lateral forces. This will very likely imply unnatural sensations.

hi david, thanks lasermaster are just up the road from me. i used them to make a couple of rotors for my windturbine. good people. do you have the drawings? if not i can get them to make some from your picture if they dont still have the files.

what do you suggest. 6 dof instead.?

Thanks, @noorbeast. Yes, that was exactly what I meant.

@bob golding , a 2 DOF simulator can provide great results and is a really good starting point. I suggest to give it a try. As a next step you could add G-seat paddles to the seat base and backrest for getting sustained heave, surge, and sway forces. You will find lots of G-seat projects in this forum.

About the angles: I would recommend to use the angular velocity rather than the absolute roll and pitch angles. This does not require large angles and can provide great sensation even when it comes to 360° loops or screws. Even more when using a VR headset.

thanks i have a hp reverb g2 headset. my main concern was keeping in sync with the simulator. i use xplane and the new a330 has realistic pitch and roll inputs. i assume that as with low frame rate if the platform is not if sync with the aircraft angle you would lose the effect. 30 degrees seems to be the maximun roll angle a modern airliner would normally encounter. i wont know till i build it but i have been in a fairground simulator with a tornado flying around the uk. didnt notice the angle at the time,but imagine you dont want your customers being sick! so i susept it is toned down a lot. this was a few years ago so not sure what he modern ones are like.

thanks i am still gathering info on things like motor speed and response time. i imagine GA aircraft and airliners have very different response times than cars. once i decide on the final design i will be doing a lot of reading and asking questions about that no doubt. i have got an old pair of wheelchair motors most for free to experiment with. still not decided between cranked motors and linear actuators. linear actuators have few parts so less lag but that could tuned with the xplane joystick profile settings. its more down to cost really. that why i want to start simply and see how get on first. the jump from screen to vr is pretty dramatic.

hi david is the cross just clamped between the brackets or is it secured in some way. ? i have ordered a land rover defender 63mm one.

Hi Bob
The UJ is a Propshaft UJ Universal Joint 82mm x2 for Land Rover Series 2 3 - RTC3346.

I am currently on base as I work at RAF Benson, I will give you more information when I get home tonight.

David

Hi Bob

I can give you the information for the UJ,

The width of the bracket is 10.mm there is a bearing carrier for the Land Rover RTC3346 Universal Joint the dimensions are: eternal depth is 15.mm x 35.mm width, internal width 27.mm internal depth 11.mm / on the rear of the bearing carrier is a mounting lug the dimensions are 6.mm x 20.mm to go through the center of the UJ Bracket, and then welded together from the rear.

There is a center spacer to join the two brackets together 90.mm x 15.mm with a 10.mm thread taped.

My UJ was designed to fit on to a 50.mm x 25.mm steel beam with 4 spacers per side 22.mm x 14.5.mm with a 120.mm hex head bolt x 2.

thanks david got all that. i have ordered a uj. i am still confused about how the bearing is secured to the bracket. it looks from the photo like it is just pushed up against the bracket. could you elaborate on the fixing please. normally it would go into the hole in the uj bracket so i am a puzzled about what stops it sliding about.

Hi Bob
Bob if you PM, i will give you s link to my Google server and I can upload all of the information you require
what type of simulator are you going to build, with regards to my simularor I have based it on the DOF Reality design but with lots of modifications .

David

Hi Bob

The bearing fits in to a bush that is welded to the bracket, and the two sides are held together by the center spacer.

David

thanks all clear now. i thought what i was seeing was the outside of the bearing.