I’d like to experiment with the linear motion parts but its not clear to me what components are required to build what I am seeing in the pictures on the website.
Can someone provide me with an orderable parts list for what I am seeing there? I see the motor (plus motor controller I presume), the linear motion kit, the advanced gear kit I guess? And then some other mounting hardware?
Can you guys really not come up with a parts list for this?
Capstan,
Sorry for the delay - it’s a very busy time of year for VEX!
To build the kit you’ll need the following items:
(1X) 2-Wire Motor 393 w/ Motor Controller 29 (Motor Controller 29 can be omitted if you use ports 1 or 10 on your Cortex) - http://www.vexrobotics.com/vex/products/accessories/motion/276-1668.html
(1X) Linear Motion Kit - http://www.vexrobotics.com/276-1926.html
(1X) Advanced Gear Kit - http://www.vexrobotics.com/276-2184.html
(1X) Shaft Collar (16-pack) - http://www.vexrobotics.com/276-2010.html
(1X) Bearing Flat (10-pack) - http://www.vexrobotics.com/276-1209.html
(1X) Screw 6-32 x 0.250" Silver (50-Pack) http://www.vexrobotics.com/screws-6-32.html
(1X) (1X) Screw 6-32 x 0.500" Silver (50-Pack) http://www.vexrobotics.com/screws-6-32.html
(1X) Screw 8-32 x 0.500" (100-pack) - http://www.vexrobotics.com/screws-8-32.html
(1X) Nut 8-32 Nylock (100-pack) - http://www.vexrobotics.com/nuts-8-32.html
(1X) Drive Shaft 2" & 3" Pack - [Drive Shafts - VEX Robotics
Good luck with your project!](Drive Shafts - VEX Robotics)
Thanks for the parts list. It comes to more than $100, which seems a little steep for what this thing is don’t you think? Also I would be buying 50-100 screws in some cases and only be using a couple of them. And noticing that some of the hardware is not in stock, I would have to source it from elsewhere.
It would be great if you guys sold this as an actual kit with all parts included plus a few spare screws and nuts.
Capstan, thanks for your interest in VEX and we apologize if the original list of materials didn’t meet your needs.
Our goal is to maintain accessible price points that are reasonable for an educational or hobbyist budget. Carrying small hardware such as screws or nuts in bulk quantities is the most economical way to ensure fair prices for all users. This is standard practice for online hardware vendors. That said, the screws and nuts required are standard 6-32 and/or 8-32 thread size - if you find similar screws from another vendor that better fit your purposes, then they should have no problems working with the VEX EDR system. If you are using this on a VEX Robotics Competition robot, please keep rule <R7> in mind regarding what parts are legal for VRC use: “c. Any commercially available #4, #6, #8, M2, M2.5, M3 or M4 screw up to 2” long, and any commercially available nut to fit these screws."
While items do occasionally go in and out of stock, all materials linked above are in stock on all regions of our website (US, Canada, etc) as of this posting. If any part is temporarily out of stock on the VEX website, we also have a number of resellers worldwide who carry official components.
We always appreciate product suggestions that will help to improve the VEX user experience, and will keep this kit option in mind for future developments.
Thanks for your helpful comments.
I ordered the parts and they arrived a couple of days ago. I was able to assemble one of the possible configurations of the actuator today, and when I get time I will apply some DC to the motor and see if it turns and runs the slide. Assuming that works I will program something that drives the motor controller with PWM.
For the benefit of any readers who do want to build this, I found that the “6-32 x 0.250” screws mentioned in the parts list were unnecessary. Apparently they were intended to attach the motor to the rack-and-pinion bracket (though the flat plastic bracket), but the motor comes with a little package of those screws and they worked fine. The 6-32 x 0.500 screws are needed to attach the rack gears to the metal slide.
A “linear slide block” has to be bolted to the bracket as well. This is a plastic bearing that you insert into the metal slide to couple it to the bracket. It requires 8-32 screws but the 1/2" ones in the parts list (out of stock but I was able to find them at Loew’s) were too long and they went through the block far enough to hit the slide. I had to go back and get some 3/8" and even they were slightly too long, I had to use washers to shim them.
I am seeing that there isn’t anything inherent in the components I bought that will act as a stopper in either direction. The motor would just turn until it runs the slide completely out of the bracket. So I guess I will buy a couple of microswitches and try to mount them on either end of the bracket in such a way that they will hit something on the slide when it comes to an end so I can detect it and stop the motor.
I’m not planning to use this for any kind of competition, merely needed a linear actuator and light-duty ones are hard to find.
I realized that I had 5V DC right here at hand on a breadboard so I hooked it up just now. The motor does turn the pinion gear and the “rack” slides through the bracket. There is a fair amount of mechanical noise, I guess this is coming from the reduction gears in the motor assembly. It isn’t just a “motor” per se, it appears to be what most people call a gearmotor. But I am seeing some really troubling behavior with the rack and pinion.
The “rack” is a series of plastic gear segments that are screwed to the metal slide. When the pinion gear rolls along to a place where these segments join end to end it appears to be hitting the top of the gear tooth on the next rack segment instead of meshing correctly. Sometimes it actually jams and stops. In the best case it makes a sharp sound, jumps and manages to continue. Apparently the rack segments don’t mate up close enough? There is a visible gap between them and no play for adjustment. Its very clunky.
Any suggestions? Am I going to have to file down the gear teeth some at those places?
Capstan,
We’re sorry you are not happy with the rack gears. The problem that you are describing can be caused by mounting misalignment. Each rack gear has (3X) brass bosses that stick out of the “bottom”. These help align the gear with the linear slide for proper tooth engagement with the pinion gear during transition between rack gears. We suggest checking that each of these bosses are properly seated in the linear slide. If this does not solve your problem, try loosening each of the #6 screws that retain the rack gears and re-positioning them before re-tightening the screws to ensure that the rack gears are properly spaced.
If you continue having problems, please contact our customer support team at 1-903-453-0802.
Thanks for the suggestions. I did make sure the bosses are seated in the slide. They are a tight fit, and once they are seated there is no way to move the rack gears laterally. Here’s a photo, you can see that the gears line up but there is an obvious gap between each of the segments. I am thinking that the gap is too large, there appears to be slightly more space between the teeth there. I’ll call the customer support number.
I talked to customer support on the phone, very helpful. They sent me a different pinion gear and it is all working much better. The slide runs along reasonably smoothly through the drive mechanism now and I can move forward with my project.
Capstan,
We’re glad to hear that your problem was solved. Please let us know if you have any further questions or concerns.
-VEX Support Team