Questions - Help - 3DOF AC Platform IT Begins -

Hello gentlemen,
Been a busy day for me...work work work - and just getting back to my thread and more education.
First and foremost, ALL of you have great ideas that come from actual builds / or / backgrounds in fabrication / electronics / engineering...
Now I really know why there are so many diy's out there that don't work to expectations.

Here's "my" plan & assumptions : compiled from ALL of your great ideas, facts, calculations. Hopefully the majority of you folks will give me the OK and acceptance to move forward??
Please respond if I am going to make a big error!

1. Tomorrow, I will attach casters to frame that is finally painted and attach the MDF surface to the frame.

2. Sunday after Church - I will put gearheads in their respective positions - I will arrange so they ALL are 16" from centerline of u-joint/spline - this will give me +- 14.3 degrees of movement w/4" up/down/ movement from lever arms, AND all will work together as an exacting unit.

3. With my identical 1hp motors and identical gearheads at 117lbs of torque each - they will more than handle my 350 lbs. of top platform weight (includes rider)

4. Build my top frame in the next 10 days.

5. Attach 12" x 4" od x 3/16" thick pipe to accommodate Spline Hub and Spline - Weld pipe to 9x9x1/4" bottom plate, insert spline & u-joint.

6. Attach top platform to u-joint -

7. NOW - to earobbie's suggestion and compression spring -
A. Measure distance from base of spline, being all the way down on the 4" lever travel, to the top of u-joint. (Measurement 1)
B. Raise the top platform to upper most position, or 8" from base, measure distance to top of u-joint. (Measurement 2)
C. Pipe that holds spline is 4" od (Measurement 3)
D. Top platform Weight is 350# (Measurement 4)

Give measurements 1 - 4 to Spring Manufacturer - and advise I want 1/2 to 1/3 Compression at bottom of travel.

ALL of my build will have pictures and updates that I will submit to my original build thread.

Guys, just FYI - All my life I've had to have a game plan written down to follow. I do appreciate all of you humoring me and most of all the patience. You ALL have been so instrumental
in my learning process and moving forward in my build. I assure you that I will work hard, ask questions, and I am always open to hear if I'm getting ready to crash & burn.

Thanks so much and I'll be watching for your replies.

Have a most blessed one.

Tom

I agree with eaorobbie that for a spring to work correctly it must be the right spring. Ideally a spring would always exert the same counter pressure regardless of its compression. But that's not how springs work. As they compress the pressure increases. Since a longer spring takes longer to compress, it variance in pressure will not change as fast as with a smaller one. So the longer the better. The problem is that with the spring directly under the seat, you don't have a lot of room to work with unless you don't mind your head being at ceiling height at its highest point. I would think your spring length should be at least double what your throw of 8 inches is but I'm just guessing. I have no experience using springs myself. But yes, fighting the wrong spring could be worse than using none at all.

I think I have deduced that Terry's answer to the angle question is the correct one and why. As the motor increases the platform angle, if you were to measure directly between the pivot and the pushrod, the distance will become shorter. The less distance there is between the pivot and pushrod, the speed and distance traveled will increase. Trigonometry doesn't account for this but geometry does. That is why I came up with 14 but Terry's is a little bit more at 14.3.

Hello BlazinH,
Been out with my 3 year-old grandson having dinner.....what a kid, WOW!
??? Hopefully, my plan and actions were agreeable???

FYI to all - Over the past three years of reading /searching/ etc., I've seen several AC platforms (Not CKAS) - that use a coil spring under u-joint to base. They "appear" to be about 6 to 8" in diameter, and about 10 - 12" in length. You can see a LOT of space between each coil of the spring. Most of these are European Countries - and by the same token, I've also seen some without springs - go figure.

My ONLY thoughts, and not based on anything relative, just thoughts - IS that a correctly made coil spring would "assist" and help the motors/gearheads a long time - NO, I do not want to severely sacrifice motion. Now if I don't use a spring, which eaorobbie says he fills is not necessary (and he's probable 100% correct), then will the wear and tear on the motor/gearheads mean that I'll have to change those out every year.......IF so, then it's way too expensive to have to do that............see the dilemma of "MY Thoughts"????

My rough measurements for a coil spring (rough but close)

Platform completely DOWN - lowest point - from base to bottom of u-joint - 13"
Platform completely UP - highest point - from base to bottom of u-joint - 21"
Spring Height would have to be 21", compressing down to 13" - or 8" compression
The inside diameter of spring MUST be a minimum of 4.5" to accommodate the 4" steel tube that the spline shaft rides in.
The outside diameter of spring CANNOT exceed 8".

I really am concerned that I'm going to speed good money for the wrong spring. I know, with luck, I may hit the "right" representative from the Spring Manufacturer and that they will really know their stuff
and I'll get it made correctly - but I do know the odd's are not in my favor.

Hopefully, eaorobbie or someone here has a lot of familiarity and can help me out - or at least let me "know" the lingo to do it right when I talk with these folks...................and CRAP, I may NOT even need
one??

Thanks folks - I highly appreciate all of you!

Tom

PS - BlazinH - I've seen quite a few of the platform builds that must be 4.5' tall - need a step ladder to get into them............even seen one where the builder found an old front spring from a motorcycle in a
junk yard (think he paid 4.00 for it) - He said it worked great....which I'm not too sure about.....ME does not want to replicate that - I'll go back to 2 DOF before I build a stepladder platform. Hopefully mine
will be 26" in height..........at least I'm shooting for that. Thanks

Sorry just one note , the centre slip joint under the uni must not be able to rotate at all or the resulting motion will yaw unpredictably not a nice feeling.
Talk to a spring manufacture, they can custom roll a spring to do what you need, and normally know what they are talking about too. All it is doing is to take up the extra force caused by the inertia of the possible fast movements. Needs to support the weight of the sim but be weak enough so not to dampen the movements, I know @AldoZ did a lot of research on his unit before getting it right, pretty sure he wrote a lot of information in his post. I will do a search later and link it here for you to read.
My preference is not to have one at all on a sim.

Hello eaorobbie,
I have a 1 1/4" diameter spline unit and spline coupler so there will be zero yaw.

Thank you for your time to search out a link for AldoZ and his overview - no doubt this will be helpful.

Re: eaorobbie - thread #64 - Talk to a spring manufacture, they can custom roll a spring to do what you need, and normally know what they are talking about too. All it is doing is to take up the extra force caused by the inertia of the possible fast movements. Needs to support the weight of the sim but be weak enough so not to dampen the movements. YOUR statement is exactly what I will need and will be saying to a spring manufacturer.

My intentions are to try it without the spring and see what happens.

Appreciate all of your help, thought processes, and information.

Tom

Hello every one ... My big friend Tom ... sorry I was out if town for a while ... I have something to add to this fantastic thread .

To be specific in choosing/manufacturing the spring to be used ... I've been previously searching about springs spics/force curves for @prilad to make his simulator ... and found that a Compression spring with constant pitch closed and ground end type is what commonly used for this case .

In Wikipedia it states many kinds of various materials of it and states the conditions for each use ...
here is another Spring-I-pedia for calculating any spring parameters .



My special note is as per the spring should be Holding Equally the total platform wight all the traveling 8" distance from the highest point to the lowest ... So basically it "the spring" will be a little bit longer in it's free condition not only 21" ... and 8" outer diameter is more than enough but "to be short in words" bigger diameter gives more load support in the working constant-force area [ the above middle figure] ... No doubt that the motors will encounter little extra "off balance " up force in the lowest point or when you're off the chair ... so review/enforce your motors chases mounting points/bolts with heavy washers according to that so no frame bending should happen .

So I guess if you can't find something on eBay ready made like that ... you just have to provide your manufacturer with the load actual traveling distance ,minimum and maximum fit in coil dimension ... and of course the total wight you're dealing with plus the future expected add on wights which may vary after finishing your moving base "you may add more speakers, decoration plates, additional supporting /decoration steel pipes, head lights, ... etc " + you may have a growing up 3 years grandson Air-force fighter playing with you ...
so they do there best choosing the right shape and spring coil pitch that best serve you and don't forget to ask for the spring washers that will house the spring ...

============================================================
BTW ... About calculating the Roll and Pitch angles I guess you'll have more ... since you have a free up and down u-joint and with the Sim tools program you can combine and invert the game forces for each Axis so the side motors can give you pitch too ... I mean you can have all the 8" pitch deference up or down ... not only +-4" .
I know what you're going to say ... keep the side motors where they are

FYI - To all - above are some of the examples only of what I've seen in platforms and the ones that use springs for extra support -
The first pic to the left - to me, it looks like the frame is bent and distorted ??? - the center pic is a professional one.

Hello friend Speedy,
WOW - what information - and I'm so happy to know you're working and searching for prilad and it just ties in with my help and needs.

I do KNOW that had I not received the wonderful help of all of you folks - and done this on my own - Well, let's just say it would have been an albatross!!!!

I finished my base frame and platform yesterday - going to try and send pics tomorrow to the BUILD Thread that I started - am really "under the weather and feel like crap" today.
Love my grandkids, but when you keep them when they're "sick", your going to become sick yourself.....still love them dearly, but geeze.....what a bug I have!

Speedy,eaorobbie, BlazinH, Terry, and ALL anyone I may have missed, thanks again for your help and continued support.

Have a blessed one,
Tom

Hello Folks,
Hopefully, the attached thumbnail shows the final measurements and information to build my spline shaft pipe, spline collar, etc., with the measurements required for an assist spring.

You will notice the space with platform 100% down = 11" and with the platform 100% up = 19" - Total up down movement +- 4".
I have revised the total platform weight, with rider and rSeat, speakers, etc. My first computation was 350-375 lbs., but "me" forgot to add the top steel platform and platform MDF weight...

(eaorobbie - I know you feel a spring is not necessary with my 117 ft.lbs ea x 3 gearheads - but with the "extra weight" - do you still feel the same way?)

Fellows, you've kept me on track so far and at this point of the build, I think you all would be proud of what "we" have accomplished.

Please look at the pic and see if I'm OK / or / about to crash and burn!

Have a blessed one my friends,

Tom

Hi Tom. Just thought I’d throw in my two cents even though I haven’t experimented using springs myself. There are two reasons to use springs. One is that you don’t have the required power without it and you must have the boost. Two is a spring helps provide a more equal force in going up and down. When I said earlier that the PID must work harder without a spring, I was saying that the motors have to work harder (PID timing actually always stays the same regardless of the load). The harder the motors are working to keep up, the worse the motion will be compared to the actual data.

Since you have the power you need already, you don’t really need a spring for this purpose. This spring would have to be made just right for your rigs weight and throw. But any spring that you add that can remove even some of the weight off of the motors, the faster they should react unless your spring reaches full compression before the levers full throw finishes. So this spring should not need to be near as critical in its specifications. Again, a long as it doesn’t ever reach full compression with your load and throw, you should never be fighting a static spring pressure. I hope this makes some since. You should then be able to ease back on your PID settings. This should take some wear and tear off of the motors and gearboxes as you desire also!

BlazinH,
YOUR 2cents is always worth "much more" and always welcome friend.

?? For you - and based on your last thread:
1. Even with my more accurate top platform weight, loaded, of 425 lbs. - my motors/gearheads can still more than handle the weight??
2. To "me" - It makes sense to ease the burden and weight on motors/gearheads, longer lasting and quicker response?
3. My motors/gearheads can take it, but the spring will help ease burden and make response faster?
4. Speedys' thread from yesterday states I would need a : constant pitch closed and ground end type spring.
5. DOES my diagram of spine, spline shaft, etc., look to be acceptable in your eyes??

If ALL looks well to you and the others, then I'll build my spline assembly to my diagram specs. After that, it's to ask the spring manufacturer the RIGHT questions, give them the RIGHT data,
and go from there?"

Thanks for your continued responses and information. As stated earlier, and with the bug grandkids passed on - I have felt like a semi-truck has hit me - just lousy, but this thread sure is up-lifting. Thanks.

Have a most blessed one,

Tom

The spring speedy recommends would be your ideal spring (requires no power when at center position). But again, probably very difficult to get one that’s tuned in just right unless you get lucky. And while the numbers still say you have enough power I am skeptical about math when it comes to motors. And if you end up only running at 70% efficiency, you are already below 500 lbs. What I would do is not sweat attempting to get the perfect spring just yet. I would look around for a salvage spring (cheap) that would compress to your bottom position of your platform under its own weight with a driver on it and that will still have some decompression left at the top position hopefully. This spring is not attempting to be in balance when the platform is at its center position. It is simply assisting in lifting the weight. It probably wont be of much help as the platform nears its top position, but it can’t be worse than no spring at all the way I see it. And the tuned spring would only be in tune for a narrow range of driver weight. If you weight 25-30 lbs more than your grandsons, you would probably need to add additional weight to the platform when they are on it. But if it doesn’t work out in the end, you can go ahead a try a custom spring. Put me down for 2 more cents.

Hi Tom,

If you don't mind me asking. What motor / gearbox are you using for your platform?

The only thing holding me back is finding the correct motor / gearbox. I'm looking to build a flight sim and racing sim combo also.

I see options in Australia and Canada but having a hard time finding something in the US and notice you are in LA

Regards

Brian

BlazinH,
I'll put you down for 8.31 more - your thread makes a lot of sense to me - and that's what I will do. Thank you so much. I highly appreciate your help, thoughts, and overviews. I'm learning so
much from you and all the guys here. Just Super! Stay in touch.

Brian,
Good to hear from you and ask away...I promise to never tell you anything that I'm not sure about.
A very quick review - been a flight simmer for 8 plus years. 3 years ago, happened to see a youtube video on a platform sim - The CKAS - after contacting them, to get it here in Alabama, 8000.00 plus.
Well, I knew I could build the thing a lot cheaper (at least that's what I told myself).............a full year of reading everything I could get my hands on, looking at manufacturers' of platform sims, most are
European, and here I am today. In the last year of watching the "other forum", and joining here a while back, I finally am in the process of building and having a great time. THIS is my one and only
Sim Forum.

The CKAS type platform uses SewEurodrive motor/gearheads - rated at 3/4 hp. Don't know what the torque is, but they are a 60:1 - or 30 rpm. I checked and no-one in the US handles OR services the SewEurodrive and I found a Chinese distributor for the US - EACH motor/gearhead was going to cost me almost 900.00 (shipping was 300.00 each) - Well, that stopped that.

Started researching for a high torque gear drive and settled on the Boston Gear - retail, they are about 600.00 each / and the MicroMax 1hp Motors (3 phase 230v INVERTER DUTY, 1800rpm) go for a list
of 270.00 ea - NO - I'm not going to to that - I would be back up to 900.00 / motor/gearhead and I needed 3. NOPE, not going to do that...........

So, for almost a solid year, I bought "new" Boston Gears - 72660B5J - 1 hp rated, torque 117 ft. lbs, 60:1 - Found NEW on eBay for just a little over 500.00 for ALL 3. (They are built like a tank and HEAVY)
In the same year, I bought all 3 of my Marathon MicroMax 1hp motors (2 New at one time for 200.00 Delivered) and 1 for 150.00, new. SO, ME DID GOOD.
It just takes some time and diligence to find these at a good price, BUT, they do exist.

Now, todays' date: Since being a member of this forum, most of the folks use other types of motion sims for primarily racing, with a few doing flight sim......as I said, over the past year, I've also have been bitten
by sim racing - Have many software programs, T500R Wheel, Ferarri Wheel, shifter - JUST WAITING for me too finish this platform.

So Here I am, STUCK with all my motors/gearheads for a platform that most people wouldn't even get on.......BUT, I can't throw the good money away - So I am going to do both flight sim and racing...

The final straw - our guru "yobuddy", in a conversation about VFD's etc. told me that they could be increased in frequency and that a platform could shake the crap out of you and would probably suffice for racing -
not the perfect racing unit, but very good. Our friend Speedy, also added to the overview with his knowledge and help in the AC and VFD arena.......

When I get this rascal finished, it's going to look good, and perform very well - It will not be "mine", but to all who have helped me....

Finally (yes, finally), don't put it off. Go for it....I wasted a lot of time.

Good luck and have a blessed one,

Tom

sounds good

Thanks so much bsft - appreciate it!

yobuddy - hi friend - that's an interesting idea - and a good one - IF I use the springs that speedy and blazinh have suggested (constant pitch), it would be a nightmare to put a spacer "under the cup" at bottom -
with the filled weight of the top platform (of course, less rider) - at this point I don't know how I would raise the bottom spring cup???? Any ideas....

I tell you what, IF they still make an air-bladder for springs, like in the old days before air shocks, it would fit around spline pipe and inside of coil spring - they have an air valve just like a car tire and
you could adjust for weaker or stronger spring.....geeze - I'm going to go and see if they still exist.

The ideas are just getting better and better - Guys, don't let this go until we've reached a perfect solution - yobuddy - see what you started with another good thought!

Thanks so much friends,

Tom

Hello yobuddy,

The ol' "Keep it Simple, Stupid" sure applies here. To me, this is a perfect solution. I can spot weld 4 bolts, one in each corner, using 1/2" threaded rod, put a nut "below" the base plate of spring for lifting - put 2 nuts on each rod, with lock washer, above spring base plate and I'm home free. Will use 3" long threaded rod.

Thanks so very much for a very simple solution.

Tom

Hi guys ... So far so good Tom ... Yes @yobuddy it's nice and very simple solution but hard to tune every time you switch players ... I may suggest that the simplest solution for this is to add a balancing weight "sandbags like in the big air balloons" in the platform center under the kid's feet [BTW ... what is his name Tom ? ] equal to the deference between players weight adult/kids ... so when Tom's grand kid grow up sandbags will not be needed any more ... correct me if I'm wrong or use other solution if you're not familiar with this Tom .

What do you say about Elevators which uses fixed counter weights to balance the passengers load which is considered a load fraction to motors and VFD's ... the hardest part is where the elevator is empty moving .





We had a small problem facing the long term wear and tear for the gearboxes and motors coefficient that is solved simply by adding this custom made spring ... "the blue curve " not the negative purple nor the positive green ... that spring may/not cost Tom some more in fabrication but a lot easier and perfect solution ...

I guess Tom should share this experience/resources for who wants to do the same ... as I can't just read , search and buy a spring ... and to test it's performance How ? and with what ? ... that's why errors for some other sim builders came from ... and for not using a spring at all a Big mistake choice .