Questions - Help - 3DOF AC Platform IT Begins -

eaorobbie,
Thanks for your input -
Looking at mine, it appears to be about 20 degrees. I will measure and compute - looking at the uni, I can grind out some relief area to get more movement, without compromising u-joint integrity.
Uni will be centered to comply with pitch and roll of sim.

It's real easy to get caught up in a "future" build. When I found this u-joint, at a good price, I never once thought about the total travel - From my car mechanic days it was never an issue. Now that
I am building, "it's an important issue". Just goes to show that ALL u-joints are not created equal, even though they appear to be equal.

Thanks sir for your valuable info. I will continue on.

Have a blessed one.

Tom

Hello folks,
Will post more pics this coming week... u-Joint, Spline Shaft, plates are all welded up, needing grinding...

I'm sitting here in a "stupor" with a question I need answered, regardless of how elementary.
I have ordered my 3 pots, contactless, 1 turn - 180 degrees. -

??? - Facing the motor shafts, 2 of the three will be turning from 0 degrees to 180 degrees, Clockwise, which is the 0 to 180 on the pot.

NOW, the elementary ? - my third motor (same scenario as above) - will be turning from 0 degrees to 180 degrees - Counterclockwise - just the opposite. To "me",
that means this third motor at the bottom most position or 0 degrees, will be 180 degrees on the pot.

PLEASE - it's fine to call me a dummy (this time) or whatever, but not knowing electronics, and enough about pots as to have smoked a few in college days, What???
will have to be done or how do you guru's deal with this?

Thanks so much for your patience and help...

Tom

PS - Oh' - those college days were good to me....LOL

Hello!
It is not a problem: just invert 0V and 5V wires of your third pot ;-)
Or you can deal with it in the code you will use.
Mat

RacingMat is correct when you are using standard pots. But with the hall effect pots you ordered you will only be able to reverse them with code. The power leads on digital pots are not reversible.

ps I hope you had good luck this weekend in your hunting!

Thanks BlazinH
Maybe one day, I'll use it

Hello fellows,

RacingMat - Thank you for your information - Now I've learned again.

BlazinH - Thank you for your continued education - "Reversing Pot with Code" - is that something you folks can show me how to do when the time comes???

FYI - Trip to HD was pretty good - about two hours of "looking and "looking". Found an item - 1/4" id collar with set screw - 5/16" deep - I can glue this to center of
shaft (have made a template to centering the collar). From there, of course attach the pot shaft - I'm working on a bracket to accommodate the pot body, that will be
flexible for any "out of round" issues. These collars are $0.91 ea. So, with your previous information, "me thinks" I have a workable plan.

Thanks again gentlemen for your reply and information. Have a most blessed day!

Tom

I forgot to mention don't be concerned about the code changes. No matter the controller you use, it is usually a simple fix by just switching a few lines of it. You will have no problem getting help here from someone as you know.

Your plan looks good. Not only is it a good practice to minimize stresses on the pots shaft to reduce fatigue at the joint, it should also help the shafts bearings last to their fullest!

BlazinH,
Thanks so much for the info on code changes. Sure is relief for me - and of course, all the guys here are so giving - just great.

Tom

Hi folks,
Chapter Whatever - continuing questions.
I'm just about ready to "mount the positions" of my motors on the base platform.

"Me" is thinking of my crankarm to give +4" -4" lift - Don't KNOW if this is too much, too little with a platform.

What is the formula for figuring degrees??
My Platform is 4' long with ujoint dead center - The height of my spline and spline coupler - I'm not sure at the moment - depends on the height of motors and u-joint etc.

Your continued help and educations is highly appreciated.

Have a most blessed day!

Tom

From my experience + - 25 to 30 degrees per axis is usually sufficient for adequate movement. To calculate the maximum angles you can achieve take the total length of movement of the levers on your gearboxes and divide that by the length between your pivot point and the levers for each one. The arctan of those numbers will be your maximum angles. Divide that by two to get +- degrees. On windows 7 scientific calculator you must press the inv button before pushing tan. On xp click the inv checkbox. The actual maximum angles for pitch and roll will be less than calculated if you are combining axis on the rear motors. But with 8 inches lever movement you will need to be about 13 inches from pivot to achieve 30 degrees and 17 inches for 25 if I calculated correctly.

Hello BlazinH,
Thanks so much....see if "I" am correct here.
My length from center point of u-joint TO upper frame connection of rod-end = 22" - My total travel on gearhead shaft lever is a 4" movement Up & Down or = 8".
Dividing 8 by 22 =0.36, divided by 2 = 18 degrees (IS that 9degrees up, 9 degrees down) OR (IS that 18 degrees up, 18 degrees down) ????

IF I am correct - THEN if my total gearhead shaft lever movement is 3" movement Up & Down or = 6", dividing by center of u-joint to upper frame connection is 22",
My Movement is 0.27, divided by 2 = 13.5 degrees ????

Let me know on my math and if my assumptions are correct.

Thanks so much friend....Have a most blessed day.

Tom

You must apply some trigonometry. ArcTan of .36 is 19.8 total. ArcTan of .27 is 15.1 total degrees

BlazingH,
Heck man, it's been over 50 years since I had a trig class..........

OK - in your first reply to this question - you stated 25 to 30 degrees per axis is sufficient - so, in using the 4" gearshaft arms for 8" total travel, I will be getting, (rounded off) 20 degrees, 10 degrees UP and 10 degrees down motion? I cannot go any longer on the crankarm levers - 4" max.

I know for flightsim, this amount is probably ok, but for racing ??? - do I have the ability to make this 20 degrees as radical as I can through software SimTools ???

Thanks BlazinH - I'm just trying to get my head around all of this stuff - "me" thinks I'm trying to assimilate too much, too quick.

Tom

Its been over 30 years since I had trig too so I used the internet to find the correct formula.

"Radical", as you call it, is more a matter of actuator speed than anything else. Some may refer to the d-box as radical too even though its actuators move less than 1 1/2 inches. So any motion that closely matches the screens image is better than none imo. The more movement the better though! At least up to a point. At much over 30 degrees your really trying to keep from falling out of the seat though which is more than I like myself.

Maybe I missed it but what kind of 3dof are you building anyway? Pitch, roll, and heave? Pitch, roll, and yaw? other? Are you combining pitch and roll on the rear actuators or will you have a dedicated motor for each axis? Also you mentioned your gearbox is 117 ft. lbs. I think. Is that the maximum rating on the gearbox? It will probably do a bit more than its rating but you need to have enough hp out of your motor to go along with it to reach that. What is your gearbox's hp rating? What are your motors hp or wattage and what maximum rpm's will you be getting out of your gearbox? If you don't know your gearbox's rpm's then what is your motors rpm's and what is your gearboxes reduction? This is necessary to calculate how fast your system can be although I don't have a baseline of how fast it actually needs to be.

Hi @cthiggin ...

I guess this is good for racing too ... considering your 3 motors are doing this kind of motion as they are all on the same 22" distance from the u-joint center point ...

Hello BlazinH and Speedy,
Thanks BlazinH for your additional info.

I'll bring to up to date and try to answer your questions so you can make a better overview.

First, when I say "radical", I guess I mean "quicker response" - I'm not wanting to have my anus in my throat, but quicker. Flight sim is much more docile? Hope this makes sense??

1. Platform: 3' long x 4' long with u-joint dead center of these measurements.
2. The "rear" motor gear lever will be 22" from dead center of u-joint - THIS motor will drive PITCH
3. The 2 additional motors will be placed equally on each side of the u-joint - Either can can be for ROLL - All 3 motors used for HEAVE.

NOTE: The 2 "side" motors are 16" from dead center of u-joint, with 8" total crank lever movement.
Me does not know how these two side motors having a 6" shorter distance will affect the overall scheme of things / of course this is due to a 3' x 4' platform dimension.

4. EACH identical gearhead is a 60:1 - Motors are 1hp at 1800 rpm - gives me 30 full rotations / minute.
5. Rating for gearheads is 1 hp. I do know I can increase the gearhead speed by increasing the frequency on the VFD's.
(PS - I changed one gearheads' output shaft from "left to right" and this gearhead is built "like a tank inside". Was impressed.

Hopefully, this info will help you guys give me a good assessment / and/or/ your blessings. I can move the "rear pitch motor" in to 16", like the other side motors IF this would help.

Thanks again for you patience, knowledge, AND most of all, staying by my side through the areas I am NOT comfortable with.

I'll be checking back - Have a most blessed day!

Tom

Hi
Using sketchup for 22" pivot x 4" crank radius works out +10 -10

regards Terry

Hi Terry,
THANK you for your information - I am aware that the CKAS had +4 -4 - so I'm 12 degrees better off.
As you read in my above and last thread - the two side motors are 16" pivot x 4" crank radius - What does that work out too?
And as I asked BlazinH and Speedy, I really don't know IF one motor having a 22" pivot and the other two having 16" pivots - IF that makes a difference in performance.
I CAN move the rear motor in to be at 16" pivot if you folks think I should.

Thanks again Terry,
Have a blessed one,
Tom

Thanks @telfel was going to my suggestion I always do some simple sketches to work my angles and placement out, ie having the cg supported by the pivot and the motor in the optimim place for lift and degree's of movement, beware over the years I found too much angle really dampens the interia of racing, like dbox do , with only using 40mm ie 20mm up 20mm down they are only really moving roughly 5-7deg, but with great speed. So depending on the sim use will really depend on how it all reacts.

The beauty of @yobuddy 's SimAxe is that you will be able to have up to 3 different firmwares loaded and with a flick on a switch be able to 1. have the 20 deg or more with more of a fluid motion, really suited to flight , 2. flick a switch, reset the picaxe and now a shorten range of movement with quicker and sharper responses for racing, third one never know whats next.

The beauty of open source , really love it when people open up and share things like this and not just take and run. Make a lot of dreams come true for a lot of people who thought they could never do it, I know Im one thats been helped and passes it forward.

Hello friend eaorobbie,
WOW - SimAxe sure fits my needs to a "t". Just great info to know and timing is perfect.
When you mention "flick a switch", will that be a dip switch on the SimAxe board, or/ software?
Thanks so much for the great info.

Tom