We are proud to announce our Drive Rail product line to the FRC community here on CD. We have designed a lightweight drivetrain system that allows teams to mount almost anything to it. There are three types of Drive Rails, the DR-2, DR-3, and DR-4. The DR-2, perfect for mecanum, is a compact solution for independently driving 2 wheels on each side of the robot. The DR-3 and DR-4, perfect for a tank style robot, are both designed to accept a gearbox input and distribute power to 3 or 4 wheels using a belt system within the tube. Each system comes with everything you need to assemble one side of the robot drive base between the motors and the wheels. All Drive Rails are made of 1.5 x 3 inch 6061-T6 extrusion and come in 3 lengths to make integration into your robot easier. With as many .201 holes on 1 inch centers as we could fit, mounting brackets and other aluminum extrusions is simple.
We also offer single speed, double reduction gearboxes that accept three 775 pros or two CIMs and bolt to our drive rails. We have designed custom adapter plates for other commonly available gearboxes.
For more information about us or our products you can visit plummerindustries.com/robotics or follow us on social media @plummerind
Our website is constantly being updated. If you see an error or want more information email- [email protected] or fill out our contact form.
We are creating this post to provide information to the FRC community about an innovative product/new company. So please ask as many questions as you want and we will happily respond.
Maybe I am missing somethings on the website, but I have a few questions. Are we able to use any kind of wheel on these rails? Also, is this using chain/chain in tube?
Edit: I now see the pullies in the picture. Can you explain those further, specs, recommend belts/usage, etc.
The drive rails are specifically designed for a certain size wheel. We did this to allow for the maximum amount of ground clearance with each size of wheel and to have the right pulley diameters so the forces on the belts don’t get too high. All of the DR-3 and DR-4 are belt in tube.
Reply to edit: They come with the pulleys and belts required to put them together so you won’t have to spec them yourself. Everything is the standard 5mm HTD profile used throughout FRC.
Interesting products. The drive rails seem to be a replacement for the now discontinued nanotube line from AndyMark. My team used them for a number of years and in general we were pretty happy with them. I’m not really sure why they were discontinued, but you may find that you’ll have whatever problems may have AM had with them.
Have the rail systems been tested yet? If so, can you provide some details and reports. I don’t like using untested mechanisms that I’ve designed myself, let alone something someone else designed. It’s nothing against your product, but I think a lot of potential buyers will want to see proof that the product will hold up before they risk their season on it.
I’m interested in how you packaged the belts inside the tube. By my crude ruler-against-monitor measuring, the rails are made of 1x2x1/8" tube. That just barely leaves enough room for two 9mm belts side-by-side (assuming the bearings don’t protrude in at all). When all of the drivetrain power is going through belts, that doesn’t seem like it leaves a large factor of safety.Edit: apparently the tubes are 1.5x3x1/8" which should be just big enough for 15mm wide belts. Still with a broken belt being as difficult as is it to replace with belt-in-tube, I would want an especially high factor of safety to make sure I don’t break a belt in F2 because there’s no chance I can replace it before F3.
What was the reason for designing a 3x 775pro gearbox? From what I’ve seen, most teams that ran 775pro drive gearboxes used four of them. Is there a reason to think that three is enough without burning out a significant number. And with the new more powerful, efficient, and light brushless motors becoming popular for driving, do you think many teams will choose to go with a 775 in future years?
It’s a bit unclear whether the drive rail kits come with a gearbox. I would assume that they don’t, but the assembly instructions say “Kit comes with all needed to assemble except wheels, hubs, and motors” which would point to them being included. Additionally, do top spacer bolts in the gearboxes attach to the drive rail or are they only connected with the bottom two bolts? From the renders, it looks like they should be sitting right above the top of the profile. Obviously I don’t know all of the constraints in the design, but if you can connect the gearbox in four points instead of two is will be connected much more solidly.
The Drive Rail 2’s are similar in concept to the Andymark Nano Tubes however there is quite a few differences. The tubes are longer that the edge of the wheel by at least an inch so that mounting to them on the outboard side of your robot is a lot easier. All of the gears are Aluminum so the entire system is considerably lighter as well as the assembly is simpler due to using only 1/2 hex shafts and bearings. There will be a assembly video coming soon of the DR-2 that will show this in more detail.
The DR-2 was run all last season by my local FRC team with no problems and it jumped off hab 2 every match. All of the DR-3 and 4 have been driven around our shop during the summer and fall of this year weighed down to ~150 lbs with no issues. I’m making some videos now with some driving footage to post this week.
They use 9mm wide belts and all the belts are actually designed to jump teeth before breaking. To get this to happen we locked one shaft of the drive rail and used a breaker bar to jump some teeth and even after jumping some teeth they still drive fine however they are still fairly fast to replace due to the way they are assembled. However this is the reason for the wheel sizes on the drive rails when they don’t include wheels. The pulleys increase in diameter to deal with the forces of increased wheel size.
The reason for 3 775s is to reduce the number of PDP ports used as well the size of the gearbox and while i am a (More HP = Better) kind of person during our testing we have not had any problems with them. The gearboxes are geared pretty low and for our low ratios the robots are traction limited which prevents the 775s from being stalled for any extended period of time. Even with the new BLDC motors that are comparable in power and weight the 775 is still smaller and easier to fit in tight places.
I’m going to fix that sentence now, that is a bit confusing. They do not include the gearboxes.
The Gearboxes actually attach with a Square 1.75" x 1.75" bolt pattern around the output shaft and we don’t thread into the gearbox spacers so teams can assemble the gearboxes and Drive Rails Separate. The reason you can see the hardware over the Drive Rail is so that teams can tighten them if they come loose during comp. Over the years I have assembled a few drive trains that attach gearboxes with only 2 bolts like you mentioned and have had some issues with that method which is why i designed for the 4 Bolt.
CAD models for all of our Drive Rails and gearboxes are now available on our website for teams to download and use. We also just added assembly videos to our resources page to help with assembly. Stay tuned for video of our Drive Rails running over the boundary.
