Setting feedback on 50:1 / 60:1 boxes.

Hi Everyone,

TLDR; This is for JRK controllers and 50:1/60:1 boxes. YMMV

I thought I'd share my experience in setting feedback on these "impossible to back drive" gearboxes.

I tried a few suggestion on the FAQ, and could not see anything that matched what I ended up doing , and I found this method really easy, but your setup may be different. I apologise if this has been covered by someone else.

Basically, my gearboxes are mounted in the normal way, with a flex coupler holding the feedback pot, which is, in turn, mounted on a 90-degree angle "holder"

What I found was really easy to do, was this:

1. Mount your motors, feedback pot, couplers and gearboxes in their final position.
2. Remove the motor, but leave one-half of the spider coupler in the gearbox. (remove the rubber part)
3. Move the gearbox to centre by using the spider coupler. Really easy to turn by hand. (be sure to turn the coupler, you won't be able to move the lever / shaft still)
4. Once the gearbox is centered (I use a spirit level), plug your JRK in and reset the feedback to full range.
5. Save the settings back to the JRK. Don't "learn" yet.
6. Using an open spanner, loosen the nut that mounts your feedback pot to its mount.
7. Slowly rotate the pot rear until your feedback reads close to "2048" (Middle on a JRK)
8. Tighten up the pot in its current location. (you will move off 2048 while tightening, but a little is fine)
9. Set your motor speeds to 100 Duty and 100 accel (for now)
10. Go through the learning process on the JRK Feedback to set MAX and MIN, save the settings. (Again using the coupler to rotate to MAX and MIX) Go back to "Centre" by hand once your done.
11. Place your motor back in the gearbox (holding by hand is fine, as you may need to remove it again - Not having the rubber insert in place helps here)
12. Tick the "Auto target" (or whatever it's called) tick box and slowly move the slider and check the direction of the gearbox matches. You may need to reverse the motor direction.
13. Once happy, set your Motor speeds back to what you prefer. Be sure to put the rubber part back in the coupler and re-mount the motors.

And that is pretty much it.

This may be of no use to anyone depending on your setup, but thought I'd share just in case it helps someone.

Essentially the secret is the ability to rotate the POT while it's in place. Makes it sooo much easier.

Hi @Archie, I have a question about these gearboxes. Can you feel any slop/backlash at all in these gearboxes?

The reason I ask is it's the biggest complaint about the 25:1 gearboxes, the slight slop generates a fair amount of noise as the motor changes direction all the time.

I assume yours are the ones from motiondynamics?

@RufusDufus - As @noorbeast says, you do get just tiniest amount of slop in the gears. I'm talking 1-2mm maybe.

My advice? Get them. I've gone to a "thigh mount" sim now (3rd iteration of my sim) and BOY do these 50:1's throw you around!
I had to dial down the Pitch as I my head was hitting the back of the seat, just a tad too hard, when I pitched down.

I also don't get any Motor Driver errors now as my bodyweight is not driving back the motors all the time, which really seemed to make the JRK whig out a lot.

EDIT: My CTC is 50mm

Thanks @noorbeast and @Archie, given the feedback you've saved me some money and i'll stick with the 25:1 for now.

Least they are consistent @noorbeast - My motors have exactly the same amount of play. Given the nature of worm drives with the toothed cog mesh against a spiral screw, I'd expect some slop to be honest just because of the angle of the spiral screw.

For me, the ability to get into my Sim while it's still off and not have the thing move around was enough to warrant the purchase.
Going off the Linear Motion Calc FAQ, I am getting almost 1000 newtons at 50mm CTC compared to 300 newtons on the 25:1. DiRT Rally is "violent" on the 50:1's and is a different beast. When my co-driver says "Line over Big jump" in my head I say "Sh1t"

@noorbeast - I'll take a video when it's more refined. So powerful are the 50:1 they actually sheared my lever, the welds gave way, and I hammered the levers good before I installed them to check for strength.

I laugh now when I look back at my sim build, its' gone from taking up 3/4 of my room to sitting neatly in the corner now. Trouble is when it's built and working my "Tinkerer" nature wants to take it apart and modify something. It's never ending!

In my simulator geared motors are mounted in such a way that it is not possible for me to disconnect the engine from the gearbox.
I thought this solution without the need to disconnect the engine from the gearbox: Disconnect power to the jrk card comes to the motor. and feed the same with a 12v battery to which I connect a dimmer like this: http://www.ebay.it / itm / 12V-24V-30A-controller-of-the-Brightness-LED-Dimmer-to-Single-color-lights-d- / 182356478062? hash = item2a754b086e: g: WBgAAOSwImRYLNVN
The dimmer allows me to very slowly move the motor and can thus setting the Max and Min.
When I setup Max and Min disconnect the battery and then reconect the motor to the jrk
What do you think?

even I have experience with dimmer. I know them only because at home I have a lamp with a dimmer that is to increase or decrease the intensity of the light. My motors works at 23A nominal and the problem was find a dimmer that support high A. This dimmer support 30A so the problem should be solved. With it we can move the motor so slowly to let easy set Max Min ad middle position without disconnect motors from gearbox.
I'll buy it and let you know if really works

Another use of these dimmer....
I will use ZYT90-155-12 motors and I would like control them with Jrk 12V12. These motors have 23A continuos current and a peak current of 40A.... highter than 30A that Jrk can support. Do you think that if I install this dimmer from Jrk to motor and I reduce the Volts (example from 12v to 10V) I obtain a reduction of Ah? It's a stupid idea?

I've got the same motors and controlling them with JRKs (as I'm doing now) is a bad idea IMHO. In order to make them work and not to have jrk stopping them you have to reduce power to almost half in the pololu utility (600 is 100% and I'm running them at 250/300 and still have some problems on fast change of directions)
If I keep the rig I'll switch to sabertooth

Hello Blame!,
It is in fact while I wrote I realized that my idea is not correct.
My problem is that I am very well with JRK. These cards are really easy to configure any even for someone like me that has absolutely no knowledge of electronics. I know you even despite many attempts Attempts are thinking of replacing them with sabertooth. right?
My problem with the sabertooth is that despite the tutorial I would not know how to set them up and set them ... .... I repeat my skills in this field are zero.
So before taking the sabertooth I would be sure that it is really impossible to manage our engines with jrk

@gigi: If I understand you correctly, then this is what I did when I made some experiments with a DIY linear actuator.
I could switch between "JRK mode" and "manual mode". Manual mode was meant for moving the motor manually via a potentiometer (similar to your dimmer) with the purpose of setting the max/min values.
For details, please see this post within my build thread: https://www.xsimulator.net/communit...at-fans-and-vibration.7684/page-2#post-105159

yes correct. As with my motors is impossible to move manually the levers I disconnect them (disconnect motors from jrk not pots from jrk) and for setting the range and middle position I use a car battery or a psu with a dimmer 12v 30A that let me move the motor very very slow.

To set the range just remove the motor from the gearbox (4 screws) then you can set it by just turning with a finger where it connects to the gearbox

In my simulator project I can't remove the motor from the gearbox so to set it connct the motor to 12v battery and a dimmer could be the solution

Dimmer just bought and just tested he works perfect and let us set feedback position of the big motors levers