DIY Linear Actuator design

Well done @baykah the fun will really start when the motor is added .. Glad we could help

YEEEEEE HAAAAA BABY lol :- well guys happy to report another milestone seems to have been cracked , I now have shaking and baking going on with my sim platform ,, the elusive heave rumble and road surface feed back seems to have come at last now im not so sure my floor will take the strain .....

OK tech details seems my PID settings were way off ( I did mention I had not changed the defaults ) anyways with my new pid settings and some minor tweaks to my BFF setting file Courtesy of @SeatTime once again ( mate Thanks for that ) the bastard rig goes like the clappers if anything I need to dial back the settings ..

I will post my AMC settings and BFF config for any one interested . but have to say had to get down here and post this great news well for me anyways ) I will make a quickie video as well so show you guys that these actuator will work .

Ok clamp meter measured max 99 amps at the supply output ( measured across the +12 V lead)
im guessing that ball park figure means <20 amps per motor going at full tilt..
I initially had PCars running in simulated driver mode then stopped sim and put my fat arse in the cockpit ( my driving is still crap so this way I figure I exercise the sim and STAY on the track LOL)

Actuators were not screaming in pain and did not seem stressed ., were cool to the touch and the 2x32 controller were still luke warm, no burning smells of any element being cooked, and took the heavy breaking with me in the cockpit with no trouble..

I will admit these tests are only 5 -10 minutes duration so will give update when i'm capable of wringing the neck outta this platform

hey my man @SilentChill this will work mate no bullshit , you will not be disappointed ( no im not a salesman for Dimension engineering ) LOL

yeah guys you know I waffle a lot but im buzzing at the moment CV1 coming after xmas will be icing on cake

This is a Yahoooo sign off im going back to write down the settings

I will have an update later I have my rig moving and even with the 2x60's its sucking all the power out of the PSU's. I am going to wire my battery up tonight and just test to see how far this thing needs to go lol

These motors are too poweful lol I looked at the specs again and I now I know why







Starting current = approx 3 times the full load current which is 39.5amps so I can see when at full power going from full forward to full reverse we are gulping these amps up, especially with load on the motors aswell.

Had settings on PWMmax 200 and it worked ok for 1 long stage of Dirt Rally . Cranked power up to 220 and it started stalling again and threw an error on my 2x60. Perhaps some 200w motors would be better as these are heavy heavy duty beasts

Reducing PWMmax is effectively the same as using a lower wattage motor.

hey good buddy @SilentChill there is some craziness going on either that or im kin lucky , I admit one actuator seems slower than the other 5 ( not checked this since the PID update though ) and whether start up or running im def not yet ( emphasis on the yet bit ) seeing individual actuator currents exceeding > 25 amps ...something is crazy not right somehow...

Even now with your 2 x 60's giving more or less same issues as the 32'2 i'm scratching, my already bald head, as to why your having this grief mate...

I will print out my describe settings if they can be of any help good buddy I want to see you back in this game with loads of new ideas for us if I remember correctly they are set to mostly defaults with only the Regen Resistors activated , Current limit set to 32Amps etc no exponential setup . and I swear unless im totally wrong in how im measuring this setup , I in the systems comfort zone ???? oh oh better add they are still only 5 - 15 minute test ( Numbergring GP circuit and F1 car in auto drive mode)

Gonna go see if I can video the latest platform speed and movements as promised ..

Still gonna say HANG IN THERE your closer than you think mate . NN

Thanks matey

I am hanging in there and doing lots of testing

Hi Guys quickie clip showing the new PID settings ,

also trying different seating positions to move the COG a Bit Forward ..

Happy with the Speed of the actuators and just need to understand how to Get The PID right to maximise the motion

Highlighted a few niggles :- one Actuators is slighty slower than the rest so need to be stripped out ( luckly I have now built a spare for Encoder trials so that easy swap out)

2 im still getting what I call Phantom drop out where the during a race simulation the Platform see's a go'to hold position signal ???? Annoying at this stage so still need to track down why .. mind you a quick press of the drive button on the steering wheel and it performing again

current still seems low Compared to Craig's setup but then he is Pushing his more than I am at the moment

I have noticed a slight lag when the drive button is pressed so it takes a few seconds for the motion to ramp up to full simulation speed ??

still lots to understand and Dial in but getting there

a few Seat position changes to be made and move pedals forward so that's this week end sorted LOL

Looking good you are getting there slowly driving is improving too

Totally sheared a coupler in half on my rig lol so gotta wait for China to post new ones.

Driving driving what driving lol im still in autopilot mode lol ,,, mate thats the only way I can stay on the tarmac for any length of time ... yeah yeah high wuss factor I admit it ?


finally got dirt up and running and yep you guessed disqualified after 5 corners lol ... now im nit saying im a crap driver but er yes that may not far from it .. main thing the sim works with dirt so another round of tweaking once I understand this round of tweaking . Cheers guys

less waffle more tech info I promise guys

Hi @wannabeaflyer2 , the sims moving allot better - I did notice that you legs were not on the pedals . Time to take the floaties off, you have built a good performing sim, use it - it is what they were are designed to do - training people to fly/drive in a safe environment. Just take it easy for starters and slowly build up speed - like you would if you were actually driving a real car - especially on Dirt Rally . Most importantly have fun.

Guys one and all just taking the oppertuinity to say Thanks for inspiring me to get this far, lots of work still to do and now its getting better some bits to be remade ,but all in all im loving this whole breaking the bank bending the plastic deal lol ...Which reminds me better get card unblocked its Xmas and nearly Occulus time LOL

Haha I know how you feel this upgrade seems to of become and endless money pit lol It doesnt help me having to buy everything twice

We are getting there and think we are the only 2 people in the UK with these kinda rigs pretty exclusive club TBH Lots of inspiration from each other that's what makes these forums so good, so much knowledge and sharing its brilliant never known anything like it.

Even with all the 'tinkering' still way cheaper than buying a commercial 6DOF. They may be out there, but I know of no other DIY DC 6DOFs in OZ.

Hi @wannabeaflyer2 , maybe all your driving issues are due to the tiny screen at the end of the room that you are trying to use (I would also struggle trying to drive off that ) - Believe me, the CV1 will be a revelation .

Hi @wannabeaflyer2
You asked this question in September

i read everything in your thread but couldn’t find someone to answer this. And since i had similar questions, there could be some more guys out there who would be happy about an explanation^^
The simple answer is: NO. There is absolutely no difference, if you fix your actuators the same way. The only difference will be, that your motors will consump more power due to the higher weight of he bigger top platform.

I’ll try to explain what changes influence the rotational and translational movement of he upper platform.
First we need to difine a coordinate system. In this case a cylindrical would be the best:

You have the axis z. The radius r and the angle phi.

For all examples we have have identical actuators with a defined lengths and the same lift.
Also it’s good to know, that sway and surge are influenced together as well as pitch and roll.

Lets start with 2 platforms with identical radii. The fixing points of the actuators can now only be moved with the angle phi on the bottom and the top platform. If you choose the same angles phi (difference 0°) for both you will have:
- actuators parallel to the z.axis
- the most heave possible
- a good pitch&roll
- no sway, surge and yaw
So this would be olny a 3DoF rig although you use 6 actuators. And if you don’t fix it in y- and x- direction you’ll soon have a 0DoF rig, due to the fact that i will collapse
If you raise the angle phi or the radius r you will decrease the possible heave!!

Next step is maximize the pitch/roll. The actuators are still fixed with the same angle phi 0°. If you reduce the radius of the upper platform you will increase the pitch/roll. You could say, you reduce the CTC length. With this you also introduce sway and surge to your platform, so we have now a 5DoF rig. Raising the radius r and the angle phi will result in a lower roll/pitch movement.

How to influence sway and surge? If you look from the top to the rig it's the easiest way to imagine. You'll have the maximal surge and sway if your upper platform lies IN the bottom platform in the x-y-plane. The radii have to be chosen depending to the length of the actuators. You won't be able to heave and roll and pitch your platform, since you work in two dimensions. (I know, if all actuators will move out, it will heave, but maybe downwards ) If you now raise the radius r of the upper platform, your upper platform will be higher and you'll reduce the possible sway and surge. You also can influence sway and surge with the angle phi. If you still look from the top on your rig you can estimate the possible sway/surge through the length of your actuators. You also can go to the spherical coordinate system of the actuators and simply calculate it with the angle theta:

The higher the angle theta is, the more sway and surge you'll have, BUT it'll reduce the heave.

Let's introduce the 6th DoF, yay traction loss. Since we didn't use the angle phi yet, this is the one we need to rotate our platform. The higher the angle phi, the higher the rotation yaw of the upper platform, easily said.

This is what i came up with after racking my brain for some days. So, no guarantee that anything is correct if someone knows more, please feel free to correct me. I would have been happy if i'd found something like this some days ago

And sorry for spamming with such a long post^^

I have some questions @wannabeaflyer2
You said that you'll upload your full 16 pages drawings. Did i miss them somewhere? Or are you still up to upload them?
Why didn't you build your frame like you designed it? It looked so cool. But your actual rig is also really a great piece!

@SilentChill I don't know it the explanation above could be a reason for your power consumption. Since your angle theta of your actuators is bigger than wannabes and seat times your motors will need way more power to achieve the same change in height. And according to your videos you love heave the most I know, in your 1,9 m hobbit basement is no more place

Ermm what does that mean in lehmann terms ?

I tried to explain it as easy as possible and as technical as needed. i think some more pics would help to understand it. but not today now it's time to sleep

I was only joking

I have been dealing for the last couple of years with Germany Engineers/Managers in regard to my current work project - they also often don't understand our sense of humor .