Low cost 2DOF/3DOF/6DOF motion simulator - DOF REALITY

There's a couple of things that may help here. The P6 has 2 different points on the motor arms that you can potentially mount the frame to. The outer ones are the ones that are shown in the assembly instructions but if you mounted the frame to the holes that are nearer the motor shaft, it would allow the same motors to lift a heavier weight at the expense of speed and a smaller amount of motion.

Also, I'm in the process of adding a gas strut to minimise the shake that can be experienced under certain motions. (I'll post a how to video once I have it properly sorted). It wouldn't be much of a DIY task to add 3 of these to provide some extra lift if required to offset some weight. Probably not necessary though, I think the DOF Reality weight limits are on the conservative side based on my own tests.

Here is a low cost solution for reducing the shake that can result from the backlash in the motor gearing. The video is from a P6, but it should work on other platforms too. It's not perfect as the front motors move initially quickly but take a further half second to find their final position. This is only for large movements though from one extreme to another and I haven't noticed any issue with false cues when using it in VR as a result. The added gas struts can be easily and quickly removed, but I prefer the motion with them on personally.

Good job!

I tried tension springs, weights, sliding my seat back a couple of inches to produce so "tension", but nothing really worked.

I stumbled onto a solution similar to yours precisely while searching for something like what you used, but it involves a couple of motorcycle steering dampers. I like them because they have an adjustment for the amount "tension" to provide, so I can kinda fine tune the resistance so as not to apply too much. I just applied a little tension at a time until the shake was gone.

I play Elite Dangerous, so a "smooth" ride is more important to me than all the "detail" you would want to feel in a car. I would NOT recommend this solution for sim racing. It would probably kill all the fine details of the track.

I'll post a video later.

The shaking is unreal!

Which rig do you have? The new H6/P6?

Ah no, I don't own it - I mean the low-speed shaking in the video I quoted. I'd heard people talking about it but had never seen an example before.

That's interesting, I was just about to ask on here if anyone had tried tension springs, similar to Barry's suggestion in his review of the M2 (50min 38secs...)

Anyone recommend trying this at all to remove some of the slack/jerkiness, or is this futile?

Thanks!

I tried some tension springs but could never get them in a position that seemed to help. I tested my P6 with a bungee cord pulling in different directions from the foot plate and found that I needed a fair bit of force ideally upwards to get the best result.

Heave down seems to be the hardest motion to eliminate shake from for me. I noted that DOF Reality commented on my video via youtube to say that they were working on a similar (gas strut) solution, so there may be an official upgrade available at some point.

I did try that. That vid is actually what got me going down this road.

However, I tried several different tensions of springs and did not have success. The problem being that, in order not to shut down the motors because of too much resistance towards the end of the movement, the tension had to be less than what was required to stop the shaking at about the first 60/70% of the movement. In other words, the rig still jerked the first 60-70% of the movement. If I upped the tension to alleviate that problem, then the tension was too much towards the last 30-40% of the movement and one or both motors "emergency stopped". Be advised that I tried 8 different tensions before giving up. It's not like I only tried once.

Honestly, it seemed like a great idea, but I'm not sure he actually tried it in practice. It seems he mocked up the rig to show what he meant in the video, but possibly didn't actually try it because he doesn't show the concept in action. If he did have some success, it would be nice to know how many pounds of tension he used and how much relief he got.

But here is someone using it for real and it looks to be working. I'm interested to do this, would like to hear more detail from @GWiz

Thanks!

What detail would you like? I mucked about with some springs initially but without any real success. I'm currently using one 400N gas strut on one side only (I found that using 2 was causing the rear motors to overheat). I get very little shake with any movements but one small downside as you can see from the video is that due to the dampening effect from the gas strut, when selecting a new position for the rig to move to, it moves there quickly but the motor nearest the gas strut has a slight delay in achieving its final position compared to the others. Having said that, I haven't noticed any bad motion cueing when using the rig like this in VR and it is preferable to the shake that can be experienced otherwise. I would compare it to using the washout filter for traction loss. (As long as this is not set too high, it is imperceptible in VR).

It's also worth noting for anyone considering a DOF reality rig that I was using the P6 quite happily without any modifications for racing and very rarely felt a shake. (It only occurs with very specific movement combinations, so is fine more than 90% of the time). I think a mod is required though for other games such as flight sims as these tend to use lower speed movements which can set off the shake much more easily.

I haven't a P2 or P3 but I would imagine they would work equally well with this mod, just a case of working out where to attach the gas strut to.

Here's a video showing the shake without any mods with my youngest son piloting a roller-coaster. Note the shake as he goes slowly over the crest but with smoother movements after.

Following on from this, a lot of the play/slack in my rig appears to come from within the 'bolts' (not sure what these are called!) that attach the front motor arms to the top half of the frame. I have attached a video showing what I mean - interestingly it only seems to rock in that diagonal movement from bottom right to top left.



Is this in line with what you guys are experiencing when unpowered?

Thanks

Hi
Maybe something is loose here?



or not set correctly?

@xxpelle thank you! Tightened up the bolts in that area and whilst there is still some slight movement (same with yours?), it has decreased significantly!

I wonder if this will loosen again over time.

I had the same situation. No play in motor gears but seat moved on the U-joint. I purchased a new Spicer U-joint and epoxied it into the holes. JB Weld it was. Solid as a rock. If you need to remove it, heat it with a propane torch and the epoxy will soften enough to pull it out. Now that I have the P6 I have the shaking problem as well.

@RAHULUS I had exact same issue (and still have slightly). Proposal as described by @xxpelle worked for me in past quite good, but this joint is a pain in the a**, as it is very weak and does have too much tolerance. Most critical is, that is gets loose in a while again. I really used max. controlled torque possible for those kind of screws and nuts, but I assume that pairing with coated surfaces (wich rub off in a while due to mirco movements) reduced friction and you loose force of contact - it starts to move again.

@BJU - thx very much, appreciate the feedback. Yeah I can already sense that it is starting to loosen with a bit of use. Will have a think to see if there's a better way to ensure a tight connection

For the P3 pivot point, i had the same problem where after some time the bolts became loose. I ended up using locking washers and no problem since.

After 6 months of working with DOF Reality I finally have a working simulator, and I couldn't be happier. It started off as an H6, but upgraded to a P6 along the way trying to fix the shaking and motor shutdowns. Turns out my control boxes had the wrong motor drivers. DOF Reality sent me new electronics for the control boxes and everything was fixed. This thing is amazing now. It's everything I was hoping it would be when I bought it and would recommend it to anyone. Thumbs up to DOF Reality for working with me for so long to get the problems fixed.



Also, note the new dampers they sent me to fix the shaking. These things are really high powered and were pretty tricky to install alone as it required all my effort to compress them to install them. There is absolutely no shaking now and it really smoothed the movement out. The bungee cords are to add just a little bit of tension to it to stop some vibration when using the bass shakers.