motor gear ratio questions

Hello everybody,
I have been reading and looking at pictures for a few years now and finally started my project this past weekend. Slight problem, when i get in my sim the motors spin all the way to the bottom. I have not put power to it yet as the feedback resistors were just purchased today. My questions are these...
1) What gear ratios are the wiper motors that are preferred?
2) What approximate distance from the universal joint should the droplink to the motor be?

I know I have to adjust the swivel plate under my seat forward on the u joint to get the center of gravity where it will be less pressure on the motors. What I am attempting to use are NPC robotics T64 wheelchair motors. They currently have 14:1 gears in them for reduction. I will be putting the 20:1 set in. I will try to get more information and pictures together when I get a moment but any preliminary information would be appreciated.

Hello, there is probably no set answer to the questions.

1) motor gearing - depends on what motor you intend to use. Most wipers run at 50 -65 rpm, some larger worm gear motors run at 100-180 rpm. Winch motors about the same I think 100rpm plus? No set gearing. Just the right speed at the shaft - lever
2 Approximate distance for drop link - depends on the build an configuration of the sim. Motors at the shoulders would have links of about 600-700mm long. Under a frame would be about 100-200mm long. No set length.

Maybe put some stoppers under the frame so it does not hit rock bottom, even though , once the feedback pots are in place and this will stop the motors, it pays to have a fail-safe for smashing motors/pots.

The motors you have, what is the current speed on the shaft now?

OK, Here are some pictures.....






Specs of the motor with 20:1 Gear ratio at 24VDC is 230 RPM I am guessing ALOT of trial and error is going to be involved in this project LOL. Currently trying to figure out where to mount the linear pot. Link to motor Dyno test http://www.robotmarketplace.com/products/NPC-T64.html

I moved the seat forward on the swivel plate, moved the bearing backward. That should help, but with 14:1 gears, I can turn the output shaft by hand with the 3 1/2 inch hub on the motor. If you are saying wiper motors worm drive is approximately 100:1 I may have to do some crafty gearing but would like to avoid it for simplicity's sake LOL.

Thank you for the quick reply. Limit switches will certainly be installed. I think I may even have some wired up at work for parking gates HAHAHA

Depending on what control boards you use, you may be able to slow the motor speed with PID.

I have a Velleman 8055 in the garage that I bought and assembled 4 years ago. Last spring I did up a little test board with BigTallTim's dual relay setup. However, last weekend I ordered some Sabertooth controllers so I am thinking 8055 to Sabertooth like the wiper motor setup I was looking at last weekend on this forum. I would prefer to know more about how different products can be interfaced but this message board is so huge. For example, I have an IFI Robotics Transmitter
http://www.ifirobotics.com/isaac32-oi.shtml
and receiver
http://www.ifirobotics.com/isaac16-mboard.shtml
and a half dozen Victor 883 Speed controls http://content.vexrobotics.com/docs/ifi ... -25-06.pdf

And I would really like to figure out how to interface them. I think the speed controls are PWM like RC cars.....

After 16 hours of profiler fidgeting, I have decided to take a break. I can not seem to get the motors to stop without doing all sorts of jittery reactions. Using the test tablet, the motors do a rock back and forth while never finding their home position. Could be due to the lack of proper gearing. 20:1 is pretty low. The best thing I was able to acheive was setting the speed of the motors so slow that they were always behind the sine wave in the profiler but that will not perform well in the rFactor simulators I am working on. Good thing I saw advice on using linear potentiometers because I would have broken several by now hahaha. I am missing a small piece to this puzzle. I think I should have bought 2 JRKs instead of the Sabertooth units I have been messing with. Tomorow I am taking the feedback pots off the Velleman board and hooking them up to the Bodnar BU0836-LC I have for my DIY CST pedals. Hopefully that will resolve some of my feedback problems.

As I only have used and abused JRK's I can only advise on them. The PID settings seem to be the key to stopping fidgetiness I found, especially in regards to finding home position and overshoot.
I use big worm gear motors, and I have used wipers.
Eaorobbie has used wipers and now uses winch motors.
Aldoz uses winch motors.
We all have motors with different gearing, so it may be more PID related than gearing. I went from 50 rpm to 180 rpm motors, it took PID adjusting to settle them.
We all use JRKS for simplicity. Shout for help if you need help setting up them, thats if you get them.
Are the pots linear? They are better than logarithmic pots for feedback I have found.
Cheers, David.

Yes, I have linear, linear pots... HAHAHA.. From my pictures above, you can see what I started with, I simply drilled a hole in the aluminum and mounted a radio control car ball joint to the output of the wheelchair motor Wheel Hub adapter. .75 from center which gives me 1.5 of travel on the linear pot. Where is this PID setting and where can I find posts or info on it? I would like very much not to spend any more money on my trial and error method. I may decide to go with JRKs for their simplicity, however, I already have the stuff from robot projects and such....

Those are some beefy motors! Your problem is that you have all the power and torque but no control.

93 Newtons for stall torque is a lot and power output is around 1HP (~750w, if I converted correctly...) you don't need more gearing nor more power but what you need is as BSFT said is to set the PID-parameters, there's some lower and higher level PID explanations on the net and basicly PID is just the control part. You have so much power on your motors that the control overshoots and tries to correct and then undershoots and so on and so on.

Thank you for the information, I have gotten it to work! I am pretty excited, and knew it had to be something simple that I had missed, and libary explained what needed to be done! Here is a test video with the motors running at 12 volts. Now I am wondering if I want to put 24 volts to them as they seem slow....

http://www.youtube.com/watch?v=2WCj2Vvh_xg

Hi supermodfan.... happy to see it worked to you too the dynamic speed trick very nice rig.

Try fiddling with PID first, you may get the result needed, If that doesnt work, then move to 24 volts.
Just a suggestion.

New problem.... I have been trying to get Tronics simple solution to stop a runaway motor, being that of 2 normally closed limit switches with a diode to allow current to pass through when the controller reverses polarity, however, due to the low gear ratio and large rotational mass of the armature , the motor spins right past the limit switch. I am toying with the idea of having the limit switch throw a double pole double throw relay or a quad relay and put perhaps a 1ohm 1 watt resistor to provide a brake on the power leads. Is there a simpler idea? The idea is I would like for the safety stop to be completely isolated from the other boards as a security step.... Since the Sabertooth goes full reverse with 0 volts applied, I think it should be seperate. Any ideas on that one????

Let me show you what I have done, I have taken a cutting board and used a couple of hole saws to make a half of a hub that the limit switches will be activated by. And with a bunch of junk, mounted the switches for testing. The white piece spaced off of the back of the aluminum wheel hub adapter WAS the cutting board.

AAAAhhhhh Mecano,
I love the stuff perhaps anyone messing with mecano back in the day and is a gamer today all have a desire to now build simulators.

Rock on Mecano, my son will certainly be playing with this stuff in the future.

BTW I built a suspended car camera mount with my 20 year old loft bound mecano kit a couple years back, it totally eliminated all shock effects from my filming, great stuff, its useful no mater what age your at. What memoriesssss.

Sorry my post hasn't helped but couldnt help posting when I saw your mecano extensions.

1ohm and 1w resistor is nowhere near sufficient for a braking resistor, it will burn out. Safety switches are most commonly used to disable power from the actuator, of course the load would then try to move under gravity, most often a N.C electric brake is used in industry that way when the power is removed the brake would come on.

i would hook the limit switches to directly control power to the sabertooth, pure on/off to me this would work as a fail safe, but yes the moment of the motion and gravity will continue the turn. Not sure on the brake side but I think this was originally setup with a schotty diode around 15v 1w accross the poles of the limit switch to allow reversing back when signal recieved. Correct me if wrong as i dont have this problem with the Jrk's. Maybe a pull up resistor on signal circuit to stop the 0V signal? not sure on that one.
Memory serves me well this has been fixed before but cant remember, must be the old age setting in.

Well, I have gotten some limit switches installed, taken care of my runaway problem, can get the test tablet working from the game pc to the profiler pc. Installed the rFactor plugin, read the manual, tested, no data being transmitted, read the manual again, looked at several posts, tried again, no data... I am going to bed LOL Headache....

an easy one mate can be found here:
http://www.x-simulator.de/wiki/RFactor

An exert of doc:

HowTo: Install plugin

Go to the other Stuff directory of x-sim
Find the rFactor directory
Copy xsimplugin.dll file in the /Plugin directory of r-Factor
If you migrate to a newer x-sim version, repeat this steps !!!

once rfactor is running, just go into a race or practice as soon as ya in the vechicle data is transmitted, i set a trigger to start the profiler, could be ya issue by alt tabing ya will see if the profiler has started, plus sometime i notice that the sender is not working correctly and have to stop data and resend normally fixes the problem.
If not catch us on msn or something happy to guide ya through that one, Rfactor2 is working too with a different plugin, but has a timer fault not sure if its the plugin or rfactor2 which is in beta.

Hope that fixes ya headache.

Thank you so much!!! So simple, put the rfactor plugin in the plugin folder, not the root.... HUH!!! I had an AI car running laps while I adjusted the profile and checked out how adjustments changed the motion. I can't wait to get the profile right for the mod we have, and share it with you guys. Again, many many thanks to everybody for the help. I kept getting stuck in the simplest places HAHAHA

http://www.youtube.com/watch?v=tZ_MoK3U ... jYxfT-A9s=

It's alive!!!!! Thanks again to everybody here!