Prodigy's 2DOF Sim V4 - JRK's & Big 12v DC's

Finally I'm gonna start with this again.

I'm leaving this first post reserved for complete project details once everything is finished.

What I have in mind is a seat mover, I got 2 JRK's, 2x ZYT90-155 12V DC Motors, 2x 12v 600w 45A power supplies, pots.
I've already built few motion rigs, some successfully, some not, and for this one I want to start from beginning. I don't want to cut and combine old rig cause I've already did that and it would be the third time of cutting and putting together same thing, it would look like Frankenstein's monster

I'm gonna start off with some rough sketch I did in google to present what I have in mind:






Sketch is rough, dimensions not completely accurate.
For the bottom base I want it to be rock solid and steady, I would like to use 40mmx40mm profiles.

Now, I need help with dimensions. As I saw somewhere before, the line from the joint to the each motor must create an triangle, is that right? Like perfect triangle? And what about height from motors to the shoulders, is there also some formula for that distance?

Robbie, Dave, it's your time to shine

Since I'm really short with the time, I can't do a lot of research so I appreciate the inputs very much.

No worries mate, does look good the layout you are using a perfect triangle is not really needed as long as the motors are evenly spaced from the centre of the unit and both are the same distance as each other from the centre, this two measurement dont need to be the same,
I like to rack my rods back at about 60 deg, nice for holding the heavier driver, and splay them out at about 10 deg depending on the rod end you use, too far out from centre and the rod ends will lock up on the bolts holding them to the lever and chair, resulting in some squeaking or even breaking of the heads of the rod ends. The minuium angle to rack back at would be 10 deg any less the sim can move in a bad way.

There is no magic formula that I use I have found over many sims that as long as the priciples above are used the motion is better specially the further you go back from the centres with the motors except past 45 deg to flat doesnt help any more hence I found 60 deg to be real nice, specially once using 65mm centres for a lever and a Max of 100mm of movement the sim reacts very very quickly and sharply, it tosses me like salad in a bowl, dont hang on and ya in trouble for sure.

As per sketch above I would move pivot forwards a bit, you will find if you take the seat base and and seat and sit on it with a broom stick underneath it and move it back and forth you will find the right balance point and for a seat mover I like to mark that point and go 15-20mm forward of that point and thats exactly where I place my pivot under the chair. For a Seat Mover I found that loading the motors just that little helps in giving a nice solid motion, the total opposite for a full 2dof the centre need to be the balance point perfectly.

Anymore question mate fire away.

I do like the design too, nice and solid adjustable pedal distance is a nice touch too.

Ive had my big motors at 15 deg back and 15 deg angle out to the sides, it tossed around a 130 kg bloke easy.
Welcome back dude by the way.

Thanks for the answers guys.
I am a bigger guy, 110kg - hopefully making it to 100 before the wedding so if this could work with 130kg easy, that's exactly what I need.

I've saw your sketch @bsft and @eaorobbie 's too, and there are some differences indeed, mostly in position and degrees, but it seems that both works fine so I guess I will need to choose which way to go, or maybe make something in between from both.

As for start, I moved the pivot a bit to the front as suggested by Robbie.
Doing that, there is no more perfect (60° x 3) triangle, now there are some angle differences, but distance from pivot to both motors are the same, only the distance from one motor to another is now something narrower.



Moving the pivot and the seat to front created also some other differences in degrees, Dave you've said that you have about 15° angle to the motor and now I have about 30°, if I understood what you mean correctly, take a look at he sketch. You're talking about upper degree, from shoulder to motor?



Does this seems right?
Robbie you're talking about 60° being fine, are you talking about bottom degree from my sketch?

Thats spot on , just remeasured the angle with my phone app and it was 60deg.
And they lean in about 7-10 deg to the centre, depending on rod end but needs to be min 5 deg.
But thats not to centre of shaft, I have a 65 mm centre to centre lever on the shaft so my motors would be closer to the back of the chair, the arm connecting from the end of the lever to the mounts on the back of the chair is at 60 deg and leans in about 7-10 deg.
As for an example, please excuse my sketch in your post.

OK, I went to add and adjust some details on my model based on your advices and your sketches.
I tried to do some precise modelling with SketchUp, it is a bit harder but I got the very close result to proper measures.
There are some bits of small things to edit but this is the model I will go with, pretty much based on @eaorobbie model with some twist of my own



After I've followed the measurement from Robbie's sketches, everything pretty much went to it's place so I've ended up with rod angle from 60° at side view and from back view they are leaning in about 7° to the shoulders.



I need to re-measure all the frame steel and I think I'm ready for building.

From electronics I got pretty much everything but I would like to change the cheap pots with some good hall effect pots, preferably the ones which cannot brake if the motor goes turning wild. Before I used a 'lever' system for connecting the pot with motor so there was no fear of breaking the pot because motors could turn but feedback range was low. Now I would connect the pot directly to motor shaft so I would like to avoid breaking of expensive hall pots. As I understood I would need 360° pot?

Nice layout, it really look good.

I have a question on the pots in relation to your worry about damaging the hall effect sensors:

The motor has dual output shafts correct? In other words the shaft comes out both sides? Why not mount a small cube magnet to the end of of the off side (not mounted to the lever) shaft with epoxy and then use a small angle bracket to mount a hall effect sensor that is positioned pointing at the end of the shaft near the magnet. The sensor has three contacts which are connected exactly like a standard pot. This would allow free movement in case your motors rotate too far without damaging the hall effect sensors. I did something very similar when I built a DIY joystick. It works very well.

or just drill a hole in the back of the motor shaft and use a bracket to hold a hall effect pot like a normal pot. With the shaft of the pot into the back of the motor shaft

The drawback to that is that if the pot is turned too far it would break the internals. But that depends on the type of hall effect potentiometer you have. Not all of them are free turning.

Like this , elcheapo single turn for illustration purposes

but with this pot http://au.element14.com/bi-technolo...ll-0-2v-20v-to-10v-pin/dp/2319662?Ntt=2319662
Ive already done this on a mates big worm gears, Rob has put them on his and they are also on my actuators, and I am going to fit them to my desk racer once they arrive from UK.

They are a 360 deg turn pot and cannot be broken.

Looking good @prodigy.

I have my pots directly connected into the shaft, but only using 90 deg of the 180, can turn it up but 90 deg equals about a 10deg roll and pitch in the chair, anymore and you physically can not hang onto the steering wheel, motion is wicked but you just cant drive the car, bummer, so I set about 90 deg and resulting motion is very snappy indeed.

What would be better if for example I have 180° pot:
1. Use whole 180° angle of pot but limiting the movement to 90° in the profile - 50% axis
2. Use 90° of the pot and not limiting anything in the profile - using 100% movement - axis

I use option 1, you get full resolution from the pot and limit the range of travel.

For outright speed you can adjust the min max values in the tuning centre to lower values which will result in a more dynamic ride.

The rest of it comes down to personal preference. For me I pick up the additional detail with base transducers.

OK, I am reviving this project in hope to make it finished. I would love from you people to check my latest sketches in this thread once more and give your feedback if it looks good regarding dimensions and angles. This was done based on @bsft and @eaorobbie 's blueprints so their feedback is well appreciated too. The levers were designed as 65mm CTC for using 25:1 gearboxes.

And I am missing only the pots, so if anyone has a good source for hall pots, please give me some links, Europe preferably because of shipping and customs, but I'll take all advices in consideration.

Then I would be ready to start building, cutting, welding etc..

The above sketch look good, 60/30 is about the best spot for them and 7 deg in should be right just need to check how much the rod ends will allow, rule of thumb I use if they have 15deg of movement , I use half of it so that when a lever is at its max and the other is at its min the rods ends still have a little angle left in them. Better than letting them bind up.