Newbie Question Regarding Damping Actuators

Hi there!

Currently considering building a 2DOF motion simulator (for iRacing), based on the 150mm motion starter kit by Simxperience and a 80/20 aluminium frame like that of Mr. Burns.

Still doing a lot of reading, but one of my questions concerns the damping between the actuator units and the base frame. I see that Simxperience sells a lovely damper unit for their actuators, although I am trying to keep costs down. In another example, I've seen people using the same rubber vibration mounts that they use for the central seat pivot, to dampen between actuator mount and the rear section of the frame. On the Frex Simconmotion there are rubber bobbins between the actuator mount and the base frame.

Is some sort of damping between actuator and frame strongly advised? Is the rubber antivibration mount a good solution?

Many thanks!

Thanks for the compliments.

IMHO, the biggest problem with the aluminum profiles is that they don't weigh much and therefore your simulator is jumping around on the floor resulting in loss of motion quality. A typical aluminum profile simulator is rarely in the same spot on your floor as where is started a few laps earlier. Mr. Burns wound up placing a mattress beneath his simulator to try to keep the noise down for his neighbors.

The vibration mounts rely on the fact that your base has some weight to it. If you can find a way to stop your aluminum base from hopping around, then I would recommend the vibration mounts.

Basically, the actuators are very fast and very abrupt. Any dampening that you can add will make your motion more fluid and realistic. Without dampening, you wind up reducing the acceleration rate of the actuator (to smooth things out) too much for fast movements to be realistic.
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Thanks for your clear reply Bernard. It sounds like a heavy wooden base to tether the aluminium profiles would be a good idea, coupled with a vibration mount for each actuator.

How much would a very basic steel welding kit set me back? I didn't realize how expensive the 80/20 profiles were and now that it looks like I'll have a garage, I might try to build the base and front frame out of steel.

I was shocked by the cost of the 80/20 the first time I looked at it too.

Most of the known welder brands are between $500 and $1000 for the most basic welders. You might be able to find something used or non name brand for less.

Thanks - looking into beginner welding kits... What's a good size and thickness of steel to go for, for the base frame and seat frame? Can you just pick steel tubing up from Home Depot? Sorry for the newbie questions, but I'm totally new to this!

40mm , thickness not sure what mine is. I think it's 3mm

I'm afraid there is no one size fits all answer to your question about steel thickness. It really depends on the part and its purpose. For some parts we use solid steel and for others, square stock.

I don't know where the typical DIY guy would buy steel, but I don't think it's Home Depot. We get deliveries from a local steel house. Due to shipping expenses, you'll definitely want to find some place local.

Thanks guys. May I ask which parts solid steel bar is necessary for?

Mainly the cross members, especially where the seat sits.

A sim is not unlike a real car in that structural rigidity results in better performance. In the case of a sim, flexing and hopping result in motion cues that were not intended.

Another solution will be like Prosimu, you use 80/20 aluminium and steel. look this video, the simulator is well dampened.

http://www.youtube.com/watch?v=Qrn1ENcJ2a8

AK

It's probably not fair to compare the low actuator acceleration rate Frex motion sytem video above with the detailed road surface that can be created by X-Sim for the purpose of judging dampening mechanisms. It's the detailed road surface that makes the dampening and rigidity necessary and it's largely missing from the video above.

Here are some X-Sim videos for comparisons sake. Most of them are 1080p so you can see the detail if you change the YouTube setting.


A high resolution video download (right-click & Save As) in iRacing with agressive actuator acceleration settings demonstrating the need for dampening and an initial test of a triple screen setup that doesn't require side supports.
http://downloads.SimXperience.com/Videos/iRacing Dalarra Triple Screen Beta.mpg

Same video as the download, but on Youtube
http://www.youtube.com/watch?v=7vuOiSv2Tec

An X-Sim video with good road surface detail and rear traction loss applioed in the third axis. This video intentionally shows minimal lateral forces. (In rFactor)
http://www.youtube.com/watch?v=_50rtcm135c

An X-Sim video with some road surface detail and lateral G-Forces applied in the third axis. (In RACE 07)
http://www.youtube.com/watch?v=2M5t5mg5iiI

An X-Sim video with a crash. (In rFactor)
http://www.youtube.com/watch?v=aiwDr-ru9KE

In all of these videos, you can see the road surface simulation and the dampening bar / inline actuator dampeners doing their job.

There may be a better way to get dampening, but it isn't by using a Frex system with inadequate road surface simulation.

Thanks Bernard for this nice videos. Now I cannot even await more to get my parcel (lays at the German Customs at the moment). I would have liked to order your whole solution, because I hate trouble and time wasting with trying things out by myself, but getting this big thing to Germany would have been to expensive and time consuming.
The Iracing Profile you used for the Dallara, is it in the Commander Software? Can you give me the dimensions for distance Balljoint-balljoint head and bottom bar and the distance from the pivot point under the seat to the rear bar with the joints?

I saw on prosimu website that he use X-Sim, like you.

I doesn't see any difference between your system and prosimu.... exept that you have 3 screen and 3 actuators. the two simulators are frex like.
Prosimu use the big square under the seat to do a mechanical dampening functionnality, in your system you use a damper kit.

I think, it would be better to separated your screens from the simulator, because sometimes your 3 screen move a lot.


AK

@ Prosimu Guy
Maybe you should play both videos in full screen. I'm pretty sure the video is Frex motion. The tell tale sign is the missing road surface effects.

Also, this design misses the point for why we use dampeners in the first place. There are two reasons for dampening. The most important is to be able to run the actuator acceleration rate higher than we otherwise could have without inline dampening and to be able to adjust it to your personal taste. The other is to prevent hopping and jumping. The Prosimu design is an improvement on the original Frex which hops around alot, but doesn't provide a dampening mechanism that will allow for increased actuator acceleration.

The three screens move only when the rear traction loss moves and that is intentional. You'll understand why when you see my next project.

@ Henning - I'm trying to find the thread where we discussed all of these dimensions so you not only understand what they are, but why they are. I will update this thread as soon as I find it.

@Henning
UPDATE: Here is the dimension discussions thread I was mentioning. building-a-proper-motion-base-for-scn5-s-t2216.html?hilit=building a proper motion base for scn5#p21121

It seems not all dimensions are listed here. I will collect some more information for you.

I would also be interested in a complete list of the critical dimensions Bernard! Thanks!

I knew that I had posted these dinmensions somewhere. Johnakar has taken my posted dimensions and created a drawing for the community here: building-a-proper-motion-base-for-scn5-s-t2216-30.html?hilit=building a proper motion base for scn5#p21321

I did not verify the metric conversions, but I do know that others have had success building from this drawing.

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