Introduction by way of apology

[binto100]

Hello.

I jumped into the middle of a thread about removing display cases then proceeded to post a couple pictures and talk about my project; it was rude and I apologize.  This is a remarkably talented group of people from whom there is much knowledge and wisdom to be gained.

My name is Bruce, I live in Mukilteo, WA (a community just N. of Seattle) and I'm a 56yo fishing company pencil pusher.  I've always wanted to build a simulator and now it has become my passion.  My first order of business is to construct a 3dof moving platform and I have taken steps in that direction.  I first built this crude proof of concept machine:  http://www.youtube.com/watch?v=sDR3a5U_hZE

I have since taken delivery of three Exlar Tritex II linear actuators, run 60amps of 240v residential power to my 2nd floor bonus room and designed an offset u-joint that will be used on the center column of the platform; it was fabricated by Integrity Machining, a machine shop in Ballard (suburb of Seattle).  This weekend I begin construction in place of a working wood platform so I can determine the best placement of the Tritex actuators.   Then I can get on with the final motion platform build which will be made out of aluminum.  I'm using a Galil controller for the actuators and Ian's BFF motion software.

I started this journey about eight months ago and hope to have my platform working within three months or so.  Deciding to purchase the Tritex actuators was a painfully expensive experience that I hope will pay back huge dividends in operational joy.  I just took delivery of them yesterday and they are a sight to behold.

The projects on this website are inspirational and if I were able to  accomplish 50% of what I see hear I would be very happy indeed.

Regards,

Bruce

[ak49er]

Wow, talk about starting a build right!

Two Q's

What is the purpose of the wooden hinge devices is your prototype, and why did you offset the U-Joint?

[binto100]

Wow, talk about starting a build right!

Two Q's

What is the purpose of the wooden hinge devices is your prototype, and why did you offset the U-Joint?

The wooden hinges are anti-yaw devices.  The upper platform on a 3dof has pitch, roll, and heave and must be prevented from yawing because the yaw forces want to tear the bottom of the center column off.  To prevent yaw many commercial 3dof setups use a very beefy center column support that incorporates a spline shaft similar to a driveline setup; it's not only beefy but it's heavy and weight is a issue since I'm building my motion platform/sim in a 2nd floor room.  One of the main reasons I chose the Tritex actuators is they are only 26 lbs ea but produce over 1,250 lbs force peak power ea and about 750 lbs force continuous ea vs. larger 2hp electric motors with gear boxes.  So.... the crappy wooden hinges setups will ultimately be constructed of highly stiff aluminum bar stock with the majority of material hogged out by a 4 axis cnc machine at the machine shop.  They will have 1 1/2" pressed oil impregnated bearings on the ends and will be joined by stubby ground steel shafts.  They will be stiff, very stiff, and there will be one on each side.  I foresee no yaw in my future (though it would be nice!).

I designed the offset u-joint for three reasons.  One, I was frustrated with the limited angles available on commercial u-joints, two, I was concerned about weight bearing capacity and three, I can't help myself.  The u-joint is the connection between the top of the center column and the upper platform and I wanted one with both a lot of angular potential and weight capacity.  I'm a bean counter and not an engineer so I only know how to employ overkill capacity; in other words I'm incapable of making engineering calculations so I made one stout mo fro.

The u-joint is neither small nor timid however it only weighs 33lbs and has significant weight bearing capacity; way more than I'll ever need.  The end result is I only need to use a lightweight aluminum cylinder (a Rexroth Taskmaster air cylinder 4" x 14", the actuators have a 12" stroke therefore 12" maximum heave) as the center column because I will have created platform stiffness by using the anti-yaw assemblies.

[bussgarfield]

Hi Bruce.

Very ineresting concept and one worthy of future updates on your progress.

As a mere 'bean pusher' you certainly seem to have done your home work on this project and I for one wish you well with it.

If I read it correctly, your actuators are going to have a 12" stroke which will equate to a 6" up and 6" down movement wont it ? Awesome. Better than most commercial moving platforms. Just dont forget to take your sea sickness tablets.

I don't recall seeing in your thread which cockpit you are going to mount on the platform.

Gary

[ak49er]

As an industrial mechanic, I'll say those are some very nicely engineered joints...with an amazing range for sure.

I have collected enough parts to make the conventional design you spoke of, with the slip joint to a U-Joint, and heavy center spring, with telescoping center post, to make a 6 DOF Base, but have not found any actuators yet.

Your choice looks very capable. What else goes into the power train, do you use motor controllers? What are your position sensors? Have you chosen a software yet? Last time I looked for SW a few years back, there was a program that took XYZ data straight from the Attitude Indicator (Artificial Horizon) of your FS A/C and converted it via (Serial Cable?) to your Motor Controllers. I cant remember what it was, but it was super simple, and I was able to command my Deskjet Printer motors with it...as a test using FS9.

[binto100]

Hi Bruce.

Very ineresting concept and one worthy of future updates on your progress.

As a mere 'bean pusher' you certainly seem to have done your home work on this project and I for one wish you well with it.

If I read it correctly, your actuators are going to have a 12" stroke which will equate to a 6" up and 6" down movement wont it ? Awesome. Better than most commercial moving platforms. Just dont forget to take your sea sickness tablets.

I don't recall seeing in your thread which cockpit you are going to mount on the platform.

Gary

Last December I decided to quit thinking about it and just get busy so I bought a welder, a metal cutting band saw, and proceeded to hack together the proof of concept.  There was very steep learning curve as I'm neither a fabricator nor an engineer but I kept  learning as I struggled with a multitude of concepts.  I had a house in Seattle that I was renting to a mechanical engineer and his family (they bought the house about 6 months ago) and he was kind and patient enough to spend a several hours with me over time explaining this and that and helping to turn the lights on in my head.  There were some great revelations along the way!

Like all of us I have spent countless hours researching, looking at other people's work , grappling with ideas, and finally setting some things in stone (the u-joint and linear actuators) to move ahead.

The actuators have a 12" stroke, a max rate of 13.33 inches/sec.  The degree of angle and rate of movement of the platform plus the load handling requirements of the actuators are all directly related to the distance between the center column and actuators.  At 56 years old I'm not looking for a violent ride but I do want as much flexibility as possible.  You are correct in that there will be 12 inches of total movement (heave), 6 up and 6 down assuming the platform starts at mid-stroke.  Additionally there is a spring around the center column that acts like, well, a spring!  Springs seem simple but are in fact quite complicated in their own right and I won't know the required spec's until I'm further down the road.  The spring is not used to add "springingness" (sp) to the platform but rather as a energy storage device.  I'll have one custom made when the time comes which should cost around $400-$600.

I'm loosely planning my cockpit around a Lear 45.  I think it's straight-forward enough for me to implement plus I like flying the 45.  I'm not sure yet what the actual cockpit will look like.  It needs to be as light as possible and I'll just deal with each step as it comes up.

As with all things it's just talk until the work is done!

[binto100]

As an industrial mechanic, I'll say those are some very nicely engineered joints...with an amazing range for sure.

Thanks very much!  The first night I brought it home I put it on the family room table and just stared at; my wife has to put up with a lot.

I have collected enough parts to make the conventional design you spoke of, with the slip joint to a U-Joint, and heavy center spring, with telescoping center post, to make a 6 DOF Base, but have not found any actuators yet.

I've never seen a 6dof platform that employs a center column and spring but you may be onto something.  It seems you need several actuators located "around a circle" and at an angle to get the added yaw, sway, and surge.  It's a much more complicated setup mechanically and system wise (software etc).

Your choice looks very capable. What else goes into the power train, do you use motor controllers? What are your position sensors? Have you chosen a software yet?

The system is a closed loop servo system (I barely know what I'm talking about here).  One of the (many) reasons I bought the Tritex actuators are that the power controller and position encoder are built into the unit itself so I didn't need to worry about frequency drives (to convert single phase to three phase) or external encoders; "all" I need to do is hookup single phase residential 240v.  FSX puts out a constant stream of serial data that includes position, attitude, acceleration, deceleration etc etc and there are several programs available to capture that data.  I purchased a relatively inexpensive program and modeling package from Ian's BBF at this location: http://buggies.builtforfun.co.uk/Sim/software.html

I've corresponded off and on with Ian and can tell you he's a pretty fascinating guy.  His system seems robust (has lots of adjustments) but I won't know until I actually start to test it; I've "flown" it quite a bit and observed the output.  There is a lot of tuning involved with actuators to get them to respond properly and that will be a challenging trial and error phase.  There is a lot to learn, setup, and mange.  I will initially set the actuator fault conditions to be very sensitive (e.g. turn yourself off if a certain state happens).  If Ian's software works well then I will consider it to be a gift from him to the flightsim community because it is not overly expensive.  If it doesn't work (or I can't make it work) then I will look to other alternatives one of whom is Mark Barry at Inmotionsimulation.  We've talked a few times and he's got a very good system but he ain't cheap.

Ian's software is designed to output movement information to a Galil controller (among others) so I purchased this Galil controller and 24v power supply (I got the controller that is packaged in a metal enclosure):   http://www.galilmc.com/products/dmc-21x3.php 

The Galil controller takes this information and sends + and - voltage signals to the actuators.  The voltage signals it sends are small (5-10) because the 240v power line is hooked up directly to the actuator.  The actuator goes about it's business the best it can and the encoders constantly send information back to to Galil controller about what the actuator is doing.  The Galil controller then makes the necessary voltages adjustments to achieve the desired actuator activity including in/out extension, speed, acceleration etc.  This is the closed loop part of the system.

Hopefully they all get along and I have a smooth ride.

[jackpilot]

Guys the whole thing goes way over my head but I am glad to see such ingenuityand mechanical savy.
Bravo..!



As for the smooth ride ! who knows....lol

[fsaviator]

Guys the whole thing goes way over my head but I am glad to see such ingenuityand mechanical savy.
Bravo..!

I have to second Jack's statement, but like him, I am SO happy to see someone tackle this.  Please keep us informed of your progress and don't hesitate to ask if I can help with anything!

Warren

[binto100]

I have to second Jack's statement, but like him, I am SO happy to see someone tackle this.  Please keep us informed of your progress and don't hesitate to ask if I can help with anything!
Warren

Thanks all for the encouragement; I will keep you duly updated.  The work begins again this weekend and I can't wait to get started!  The eBay purchased Taskmaster Rexroth air cylinder just walked in the door and will be used temporarily as the center column (the u-joint will mount on top of the cylinder) for the next phase which is a base and plaform constructed of wood with the actuators mounted and energized for slow movement so I can finalize their placement.  This is a 3.25 x 12 cylinder but I'm planning to purchase a 4 x 14 for the finishsed system.