question about 'heave'

I am in the design phase of my simulator and have a question. Is heave related to the feeling you get cresting or bottoming out on a hill? Does it add a lot to a sim having this as an axis on your simulator?

Thanks

Yes, you are correct about "hill"...........but you can also feel bumps in the road, curbs, dips, etc.....it's an added expense as you have to add an axis with motors etc.

Most people just add heave as a DOF in SimTools mixed into the axis of a 2DOF. For me with a seat mover I found heave then felt the same as 'Pitch', so as I was trying to get my sim as realistic as possible, I added a heave module into my seat which is driven by a separate motor. If you look at my build the design looks simple, but as you are basically moving a whole persons weight with a DC motor it is not. I although think it was worth it, as the seat now moves up and down for heave like it should and not just shaking back and forth. After saying all this, unless you have a background in these things, I would keep it simple for your first rig.

Heave is basically smaller bumps , potholes, kerbs on corners, wooden bridges (dirt3).
I run 2 DOF sims with balanced point and I run heave as part of the forces used.
Usually in a car, the first bump you feel is the front wheel, so having the sim jolt up slightly , well, for me gives me the impression , I am going over a bump and the front wheel feels it first, then the back wheel a split second later.
Now at speed its a mind trick that I am going over a lot of bumps depending on game and track.
In Dirts its a bumpy vibrating ride on dirt or gravel until I get to tarmac and then it settles off,
I assetto corsa on Monza is a very vibrating ride, feeling every bump and jolt of that track.
Heave can be set to feel really big bumps and not the small or set so you get small road vibration, going over ripple strips/kerbs and not feel big hits. (a good thing on Monza as cars tend to bounce a lot)
I have found the heave in most games will actually give me the feeling if I go over a pot hole on the left or right hand side, then the actuator on that side jolts me.
The guys have done a great job with Simtools to provide raw data out of plugins for that.
Back to heave, surge will also give some "heave" feeling as well , so it can be a balance of 2 forces, small heave number and bigger surge number.
Yes heave does add to that "bottoming out" on a down run of a hill.
The best way to find the heave you like is run only that force and fiddle with the numbers in tuning centre till you find what you like.

My next question was going to be 'does simtools allow you to separate things like bumps, curbs, texture etc and send the data to different motors or transducers'. I guess the answer is yes. What about blending of data, ie a bump in the road will send some data to the heave axis, and some data to a transducer. Does it allow this?

It's all about heave from my point of view and I'm going to have to agree with SeatTime on this one! If you want to have heave feedback on a 2dof setup, you have no choice but to attempt to add it in where it shouldn't be at all; in the pitch/surge and roll/sway axis! That's my opinion! I have tried doing something like this myself and I find it only confuses me on what feedback I am actually feeling. Using a 3dof rig that provides accurate and sustained feedback, I find that I drive as much from the "feel" of the feedback as I do using visual cues. Having a motion (dof) in an axis where it shouldn't be washes out the real feel of that axis making the feedback terrible to drive with! Again imo.

I suppose with heave on a 2dof you are limited to only small bumps, potholes, etc. or the larger ones. But it doesn't have to be that way on a 3dof rig with at least 250mm of heave and enough speed out the actuator. I get body jarring vibrations on rough tracks as well as the big sustained jumps you get with Dirt type titles so its possible to have both with the right setup. I plan on going commercial with my latest 3dof so I can't say much about it at this time but hopefully before the end of the year I can share more! I can say though, it can be either an all-in-one solution, or most will be able to use their current 2dof seat mover with it instead if wanted! Your power supply(s) won't be necessary if you use 12vdc though because it will have more than enough power already available to run it!

What kind of a motor would I need to heave me and my whole rig? Say, having an axis point on the front of the rig low down, and lifting/lowering the back of the rig near my center of gravity. If the distance was long enough between the 2 points, the heave would be almost verticle. Maybe use a chain drive? What kind of motor should I look at to power that amount of weight, and get good response?

There is not an absolute answer to your question because there are several variables that must be considered. What works for my design, may not work for yours at all. Rig design, total weight moved, actuator type or lever length and their mounting positions, ball screw pitch or gearbox ratio, etc. all come into play when considering what motor is required. But since a 3dof design normally requires a minimum of three motors anyway, you might as well use all of them when heaving. Generally speaking though DC motors are more responsive and controllable although it is more difficult and costly to get higher power outputs from them when compared with AC motors.

I was thinking to design a rig separating the forces as much as possible, hoping for the most realistic feel. Like what you were saying about having heave on a separate axis to avoid effect being washed out in other axis(s)

What I mean by this is;

a seat mover (for surge and sway)
on a motion platform holding the seat, wheel and pedals (for pitch and bank of the track)
on a final frame (that heaves and possibly yaws the platform above it)

I am making a rough drawing on sketch-up, and will post it tomorrow to give a better idea what I am thinking. It sounds cool to me, but I'd like to see what you guys think of the idea. I may be totally out to lunch...

The washing out is just my opinion based on my rig type so just because I don’t like it doesn’t mean others won't using their types of rigs.

But almost anything is possible with a budget and the other resources you need. We’ll wait for your sketch-up first.

I believe bass shaker and butt kicker support is in progress for this.
As for blending data in motion on a sim, thanks to @eaorobbie , he instructed me to do each force individually , and once happy , then mix then all up , test, rinse repeat till more or less satisfied.

Granted I havent played on a BIG movement 3DOF rig, only a dbox, but I should point out that the mind trick of it all makes you think you are moving further than you are.
Giant jolts can be un-nerving for me, so I prefer smaller motion. I know playing the Monza track i find it blunt annoying on my sim bouncing like anything going along the track, so I set the motion so its not so harsh for me, but I still get bounce, just not as much.
And with Dirt2 Trailblazer, China, its sheer brutal vibration, even on my 2DOF. Ive broken pot mounts on my actuators on that track.
Again, I set each force individually and once I get the right feeling, I then mix them all up and re-adjust if need be. Thats with 70mm throw.
Everyone will have personal preference in motion with their particular rigs, be it 2,3,4 or 6DOF.

Here is a rough model of what I have come up with so far.
The green objects are the 'movers', and the red are 'pivot points'. I did not draw in the motors etc, just trying to get broad idea down in a model. The green box at the back will not actually be a box shape, it just represents the mechanics of the 'heave'. There are a few different ways I can achieve the lifting motion which I am working on now, but I am looking for any ideas you may have that you may want to share. That is really the only area that is not worked out yet.

The front red 'T' is a up/down pivot axis for the heave, and also rotates for the sway. I could also use a ball joint in place of the 'T', but I think the 'T' would be more stable when things get moving a lot. Feel free to critique the model. Thanks

looks good.
Just a thing about the front up/down heave, if you intend to lift the entire frame in a up/down motion, you would need a 4th frame under it again with 3 or 4 powerful motors and a spring to compensate under the centre to allow direct up and down lift.
The 3 point is more for sway and would have to stay stable, just allow side to side movement.
Generally its a great concept, expensive I think to build, but a great concept.

The front of the rig will not move up/down. Just the rear will move. The front is where the pivot point is for the heave. The horizontal cylinder on the red 'T' a rotation axis for the rig to heave up/down in the rear only. So the rear part of the rig slides up and down the green rectangle in the back. Sorry the drawing is a bit primative. As I progress with the model I will make it more clear.

Did I read here somewhere that you can put a modeled rig in motion with some software available on this site?

The design looks like a 2DOF seat mover sitting on a 2DOF full frame, although if the second frame is only for heave then another Universal joint is not required, or for stability reasons recommended.

Yes, a seat mover on a full frame. The seat mover gives the g-force feel, and the full frame provides the pitch and banking of the tracks. Bsft and eaorobbie were saying that a seat mover provides a movement you get in a real car, that you don't get from a full frame. So I decided to include both. The frame located under the full frame provides the sway and heave.

Ive posted it before and here it is again

Comparisons between simulators. Other people will of course differ with this comparison, so please add your thoughts.

First things to consider, angle of actual swing of the frames and the profile written. Also, its a brain trick.
If you want a big swinging frame, go hard, the biggest swing I have had is 14 deg total, but others have frames up to 25 deg. And thats for race, not just flight.
Both frames use same motors and JRK control boards

Seat mover with shoulder mounted motors.
Generally ,a seat mover can give more precise motion detail as it has less over all weight to move than a full frame. However, too much movement can make it hard to hang onto the wheel or mash the juice pedal. And yes, the wheel and pedals are stationary, so proper placement to allow you being pulled away and pushed around has to be taken into consideration. But as said, it does give you the feeling of being moved around in a seat in a vehicle, even with a race seat to hold you in more. You tend to shift your body around to compensate for movement and also what your brain thinks you are moving like. You can still feel pitch and roll of track, but maybe a bit less as legs are still.
Some SCN seat movers on videos have HEAPS of throw. It might look like fun, but can be too much and eventually make it tiring to drive the game.
As mine is DIY and has 70mm travel of motor lever and at 600mm from the pivot , total angle is 6.5 degrees. Not much, but then again, too much may make it too hard. Other people will of course differ with this comparison.
I had a seat mover of 12.5 degrees at one stage, so with a good profile, it was nice, but a harsh profile and WHOA! Fun but hard to hang on.

Full frame with motors mounted near feet
Full frames allow you , wheel and pedals to move with you. You dont really get sensation of being pulled, pushed around from pedals and wheels. Obviously not as much as a seat mover, but still there. You tend to feel a bit more of the motion of roll and pitch , when your whole body is getting moved around, I find.
Seat mover can lose this a bit, but not really much.
Motors mounted at feet on the frame in question, may take away some of the finer vibration and motion that shoulder mount gives, but then again, shoulder mounting motors would return that finer detail due to higher leveage point. It may lessen a bit due to the fact that a full frame requires a bit more power to move. But hey, just change the profile and increase the motor power a bit more.
Although, I must say, once again, a good profile can give the same sensation in motion, be it from a different spot. Feet or knees instead of shoulders.
Full frame is about 8 deg total swing. May not sound like much considering 4 deg from centre, but again, throw a decent profile in it and you feel like you are moving a lot more.

Summary
After a while I get the same sort of feeling from both my frames, even though they are different in design.
In your choice of motion sim build, It will come down to watching videos of other frames, opportunity to play on sims when they are around to do so. Taking a look at pics, seeing what takes your fancy. Heck, even a seat mover can be converted to full frame later, add the extra bit, move pivot, and off you go. 2 seat movers I have sold, the owners have since converted them to full frames, their choice of course. They enjoy both frames they tell me.

Again I agree with SeatTime’s assessment! A 2dof seat mover on a 2dof platform mover still equals a 2dof. There are two differences though. The center of gravity of the platform will be lower than the seats cog. And moving the seat will take less power to overcome inertial forces than moving the platform with the seat on it.

Your platforms center of gravity will be low with this design. The roll and pitch of the platform will change the center of gravity because it will be throwing your whole body instead of keeping a common center of gravity. That may or may not be a problem but likely will be. And it’s easier to get tactical vibrations out of a seat mover since it has less mass than moving it with a platform to do it.

Pitch and surge operate on the same axis as do roll and sway unless you are doing a Stewart type 6dof or a surge and sway table. Therefore, I don’t expect you will see much if any improvement in the motion by separating them. And it adds a lot of extra expense and weight to heave around also!

Heave is probably the most difficult to achieve with a racing sim in particular. Ideally you will get body-jarring jolts out of road bumps etc. while still having enough stroke to simulate jumps and going up and down long steep hills. I have been working on it for years now to finally get something that will give the responses I stated above while not quickly tearing itself to pieces in the process. In the end, I had to make extensive modifications to the components I started out with by machining and adding my own parts. But since I plan on attempting to commercialize my simulator, I can’t share details atm. But once you get a final design and have some specifications to share, I or someone else can help you determine what you will need for heaving wattage wise.

ps bsft states many good points in his post above also!

this is Dirt Showdown on my former foot motor sim. Granted its a full frame. 70mm throw up and down total travel.
I have dialed in on a 2DOF, sway , surge, pitch, roll, heave. So 5 forces can be done to give the desired effect on a 2DOF.
If you look at the video carefully, you can see the pitch going over the jumps and up and down the hills, the heave of the bumps, the sway cornering and the roll of the camber of the track.