A few questions about hardware, theory only.

[Szyrs]

I'll just make it clear that I'm not mid-build or desperately seeking a quick fix. I'm pre-design, just flirting with ideas and doing research. It's possible that this is in the wrong section, but the hardware subforums seemed more specific than my queries.

From what I gather, there is no fixed formula here, there is popular hardware and common software but at the end of the day, it's every man and his shed.
My initial idea is to try a few different frame ideas and see what I like, then start looking at budget and how high I can afford to aim (lets be serious, i'm aiming to aim high and pay very little, just like everyone else. By happy chance, I can weld and play with bits of code and do things that most people tend to have difficulty with. My problem is that I always aim to high.

Originally I was quite taken with the idea of a 6dof platform. I arrived at the conclusion that I couldn't afford one. I just read a thread on this website that said that a 6dof platform is in fact simpler and cheaper to make. If that's true, why doesn't everyone have one? Can anyone explain this a little more to me? Or link me something on it?

Also the actuators/motors/whatever that people are using, what and why? I imagine that connectivity, range of motion, force of motion and speed of motion are the critical factors, then of course: size, weight, cost, colour of the box, ect..

Actuators - what is the slowest speed that one can really go for here? I notice that the 100mm and 150mm travel are the most popular, is that because of a happy balance of force/speed/stroke or are they really the absolute best parts for the job?I've seen other actuators about that apply foce in both directions, with much greater force, but at only 2"/s speed... I'm guessing no good?

Motors - Asynchronous DC seem popular but seems like you'd spend any money you saved on motors in heavy gauge wiring and power bills. Worm drive seem the most popular but the ones I have seen linked are not motors designed to hold. I would have thought that you would want the ability to hold, can someone tell me why not?
Also, what is the scalability of motors like? For example, if I have a high speed motor (or actuator, for that matter) but that does not supply the force that I require, will simply doubling up the motors/actuators give me double my delivered force or will I just run into problems with timing ect? Of course a well designed motion platform will require the minimum of energy to move, but I'm just an idiot with some tools anyway...

Misc. - I've seen a few more exotic builds floating about, I was wondering if anyone uses bike chain or anything instead of rods? It seems like it could be cheaper but probably quite noisy and would need to be designed in such a way that there is always tension on the chain, possibly just snapping it a lot..


Lastly, with frames, there seem to be a number of common design themes that all seem to go under one name. I guess that in all honesty, I want a force simulator more than I want my living room to look like a penny arcade. Im not really that bothered what it looks like, how hard it is to build or how long it takes me. I just want it. I know that I'll spend more than I want to, so really I'm not overly concerned with the price of parts. I refuse to buy things like this off the shelf though, so I'm always on the look out for bright ideas. If anyone has any experience with force simulators as opposed to car seats that tilt back and forth, I'd love to see your work or hear what you think/thought, once you'd completed your sim (or given up)

Many thanks for any feedback, cheers

[crs2012]

Greetings,

That's quite a list of questions.

From what I gather, there is no fixed formula here, there is popular hardware and common software but at the end of the day, it's every man and his shed.

That pretty much sums it up for the majority of DIY projects. The exceptions to this come from those who can innovate their own software and hardware entirely on their own, in which case the only limitations are based on their personal expertise, time and money.

Which leads to the 3 points to look at when considering all options.

Time - You mentioned that you have plenty of.
Money - You have a budget set in mind, given that 6dof is out of the max budget.
Expertise - You mentioned you can weld and play with code. Fantastic! You got the framing / hardware and some bit of software covered.

What's the end goal you seek? This part was not mentioned.

Before going down any given path, it's helpful to know what kind of motion sim you are looking to achieve? Driving simulator? Aircraft simulator? Rollercoaster?

just read a thread on this website that said that a 6dof platform is in fact simpler and cheaper to make

There is absolutely no way this is possible. It requires more motors which means more power, electronics, and hardware which is always more money.

If that's true, why doesn't everyone have one? Can anyone explain this a little more to me? Or link me something on it?

Cost would be the first reason. Space would be the second. I guess the only other reason you don't see many of them floating around in this community would also fall into the interest category. If you look at the games which are supported by the X-Sim 3 software. You'll notice that nearly 90% of the games listed are racing games vs a handful of flight sim and 1 rollercoaster sim.

Which brings us to the next set of the questions.

2dof and 3dof are generally used for the racing sim games due to cost vs speed and accuracy of motion.

4dof and 6dof are generally used for flight simulators.

There are exceptions to this general concept when you come up with some different framing and building styles. In which case this will change a little bit. Such as flight sims built with 2dof in a rocker style motion sim.

The cost of 6 motors which have the ability to move 1,000 lbs will be much greater than a pair of motors which only have to move less than 30 lbs.
Hence the hardware and electronics required to handle these motors will also change based on the motors used. Thus the cost as well.

The reason 6dof motion platforms are geared towards flight sims is because those motors are big, strong, and slow. Perfect for flight motion. Not so great for going 100+mph in a racing car , jumping ramps, hitting curbs and bumps which requires extremely fast movement and reaction times in order to get a simulation of speed and accuracy. Not to say this isn't possible. Cost is the only limiting factor here. You could spend a small fortune on big, strong, and fast motors to handle a 6dof platform for racing simulation.

Which brings us to the 2dof and 3dof type simulators which are the general choice for racing sims due to only requiring 2-3 motors which lowers the overall cost of the build.

For the rest of the questions, you should go through the projects in progress section of the forum and take a peek at all the projects listed there. This will help give you a better idea as to why people choose the styles and hardware they chose.

There are many concepts, designs, ideas and opinions on what type of simulator and motion is more accurate, fun or realistic. It boils down to personal taste and how deep your pockets are.

[RacingMat]

+1 : i like your answer

[Szyrs]

Hahaha sorry, running errands all day, thanks very much for taking the time to respond to my post.

Time and ability are not a problem, budget is always a losing battle, so I'll do a bit more research before I get too serious about all that. There is no mention of cost in the thread that I was referring too, I had always suspected that 6dof would be getting more into the millionaire's section. Link is here if you're curious at all viewtopic.php?f=44&t=897&start=20

In terms of my final objectives, I am more partial to flight sims but they don't seem to make that many combat sims anymore, so it is possible (not my intention though) that I would end up doing more car racing than aircraft flying. I guess I'd like the ability to do either but I imagine that I'll have to choose one or the other. I am far more interested in motion/force simulation than I am with making anything look pretty, getting it done quicker or cheaper.

This question of speed vs travel vs force vs cost has got me scratching my head.
You mentioned that less responsive motion drivers (for want of a better term) may be suitable for something like FSX but not so good for racing sims. I imagine that the opposite would work, using racing actuators for flight sims - or do the faster, more responsive actuators/motors do such at the cost of clean movement?

Obviously the strength of force applied will depend on the design of the complete rig but there must be some ball park figures for the speed required for simulated motion?

For example, assume I have a perfectly balanced rig, with 20 degrees of motion (in whatever configuration makes this question easiest). How quickly do I need to be able to achieve that 20 degrees of movement?

So say racing requires the most responsive kit, what sort of response times are we looking for? And then how would that compare to a flight sims' desired response time? say -30%? The vibrations and rumble effects that I've seen in youtube clips of car sims are all fast action but seem to be very little travel, at least during these specific events...

As I said, just looking for ballpark ideas and concepts at the moment. Thanks very much for your help, I'm now in a position where I can do some more detailed research, without having to open 20 new threads. Thank you kindly!

[vicpopo]

So say racing requires the most responsive kit, what sort of response times are we looking for? And then how would that compare to a flight sims' desired response time? say -30%? The vibrations and rumble effects that I've seen in youtube clips of car sims are all fast action but seem to be very little travel, at least during these specific events...

There is a big ,big ,big difference looking at the simulator on Youtube and trying to evaluate the effects forces , vibrations and to be seated in!!!

And in my opinion when you think that is slow motion , consider that in reality that moves faster.

Look at this video and give back your opinion !!

http://www.x-sim.de/forum/viewtopic.php?f=37&t=293&start=40#p6537

And believe me 10 minutes with this treatment i step down of my simulator !!!

The best is to test simulators ...

As I wrote in this topic for me the most difficult effect to reproduce is the lateral force because in a curve with a car this lateral body pressure can take a few seconds.When you balanced your simulator in lateral and the dynamic of the movement is finished ,the only force you can have is your body tilted on the simulator.In this case ,long curve, you haven't enough force to reproduce the reality.

[DEADBEEF]

I've been toying with the idea of using wheelchair motors for a 4DOF rig (one will be rotation).

Obviously there's no way 3 smallish 24v motors will be able to support the weight required as well as move things around at a decent speed, so I'm probably going to attempt to use torsion springs (like you see on garage doors / mouse traps etc) to support the weight. That way the motors only have to deal with movement & inertia.

Here's a quick video I made using sketchup to test out a few rig options.

The one on the right is the one I'm most considering. It'll use DC motors and will have wound up torsion springs to carry the weight of the seat & user. Closeup pic

Just to test out the motors & controller I'm planning on using I spent last weekend making a quick 1DOF platform using a spare wooden rig I had lying around. It works pretty good and was fairly cheap to convert.

[crs2012]

This question of speed vs travel vs force vs cost has got me scratching my head.
You mentioned that less responsive motion drivers (for want of a better term) may be suitable for something like FSX but not so good for racing sims. I imagine that the opposite would work, using racing actuators for flight sims - or do the faster, more responsive actuators/motors do such at the cost of clean movement?

The simple answer is, no. It's more of a balance of power vs requirement to do the job.
You wouldn't buy a 18 wheeler truck to move a gallon of milk to your neighbors house down the street.
You also wouldn't buy a VW Bug to move a 3 bedroom 2,000 sq/ft home full of furniture across the city.

The correlation of movement is based on several more complicated factors which I'll try to explain a little better below.
When shopping for motor / actuator solutions, there are a few general specifications to look at which are in common for all scenarios.

AC or DC
Voltage
RPM or travel speed under load ( torque )
These specifications come from the manufacturer for each specific motor/actuator.

Some of these variables will be predetermined by your simulator design needs, and some will be capped by your budget. But, all of these MUST be in unison for your project to be successful. Each one of these variables can change your design and budget needs considerably. Hence, it should be chosen carefully once you have a fairly good idea what your mechanical, structural, and electronic needs for your simulator will be.

To further complicate this process, there are probably just as many variations on motor specifications as there are projects listed on this forum.

Then we can compound this with selecting a corresponding power source and compatible motion control boards.

So, in general these are the type of motor specification combination and outcomes....

(2dof-3dof) Low power & high speed motor has a lower stall torque & lower cost.
(2dof-6dof) High power & high speed motor has a higher stall torque & highest cost.
(none) Low power & low speed motor has a lower stall torque & lowest cost, undesirable for most simulation needs.
(4dof-6dof) High power & low speed motor has highest stall torque & higher cost.

Obviously the strength of force applied will depend on the design of the complete rig but there must be some ball park figures for the speed required for simulated motion?

Exactly! The ball park for a racing sim, is as close to real time as you can get. Basically you need your motor position to align with the software's force position reacting as fast as it can each time it updates within those milliseconds. Generally a good feeling is between 100-300 position updates per second.

Keeping this in mind, you can start to see how applying more weight (torque) to your motors having to shift back and forth staying within this position per second necessity will affect the type of motor required to do the job optimally.

Next, you will have to take a look at your electronics budget to decide which motor controller & power supply solution you will ultimately decide on. Once you begin researching these options, the motor options will start becoming much easier to narrow down.

[Szyrs]

Thanks very much everybody, that's a great deal of information to get stuck into; I'll report back soon!