For those of you that use the other notation (like me), these are speed reducing, torque increasing gearboxes designed to make the motors “match” a CIM motor both physically and speed characteristics.
Can we sandwich a 4" VersaWheel between two HTD pulleys set up for 15mm belts, similar to what is done with the center wheel in the KOP drivetrain?
Essentially it will be pulley-wheel-pulley.
We don’t need a versahub in between, correct? Also, what size of #8 bolts do we need? The max on the Vexpro site is 2". This looks like it would be longer.
Thanks.
Paul, is the option of getting the cylinders still open? My team ordered a pair of 2-CIM ball shifters back in December when the website still said they came with cylinders, by the time they got to us though, the website had changed to say they did not, so we figured it had been a typo and did not pursue it further at the time.
Now, getting back to the subject of this thread, I will add a few thoughts…
This is our first year buying VEXPro products (aside from speed controllers); we started with a pair of 2 CIM Ball Shifters we ordered in December, and after being impressed with their quality and ease of assembly, we went on to purchase a pair of 3-CIM Ball shifters, 14 4" Traction Wheels, 24 50-tooth Gears and some Hex Shaft (all of which we plan to use to drive this). Here’s my personal opinions on each:
3-CIM Ball Shifters
Pros:
- Lighter than alternative gearboxes
- Seems to drive smoother than gearboxes we’ve used in the past
- Small profile, given the whats in them.
Cons:
- The assembly instructions were a little more confusing than the 2-CIM Ball Shifters.
- The gearboxes seemed to have been shipped with the wrong size (too long) screws, which stick out through the hex (spacers?) too far and prevents the faceplate from being screwed on tightly. In our case our mounting system worked around this issue so its not a problem for us on our robot this year.
- It would be nice if the 3rd stage versions came with an extra set of hex shaft spacers to allow for face mounting the gearbox while being supported from all 4 corners (We ended up making our own spacers out of AM Churro tube, which works fairly well).
- It was not immediately clear how to properly mount the CIM gears to the motors and the instructions did not cover this step, the gears also appeared to not come with all the hardware to do so (of course this is based on how we’re used to mounting motors on AM gearboxes, so we could just be doing it wrong).
4" Traction Wheels
Pros:
- Super Light, less than half of the weight of our previous custom aluminum gears of the same size.
- Very easy to assemble.
Cons:
- Mounting tread with rivets was a bit tricky since you have to use long rivets that also have wide enough heads to hold the tread on. We ended up having to use long rivets with small heads and using washers to keep the tread on. Some instructions on recommended tread installation methods and rivet sizes would be helpful in the future.
50-Tooth Gears w/ VersaKeys
Pros:
- They’re so freaking light!
- The versa keys were great for mounting the gears onto the wheels (using VersaHubs). The alignment looks great.
Cons:
- A few of the gears had a hard time fitting onto the VersaHubs (not sure if this was a problem with the hubs or the gears though).
- I’m not sure if they just weren’t available yet when we ordered the gears or if we were just looking in the wrong place, but in retrospect it would have been better if we had ordered some of the gears with 1.125" bearing holes instead of hex.
Hex Shaft
Pros:
- Smooth fit onto our hex gears, works much better than hex stock we’ve gotten elsewhere
Cons:
- It would have been nice if the longer length options were available (in stock).
It wasn’t clear at all. We ordered 2-CIM shifters on January 7. The bold, red text that you see now was not there. The description of the “pneumatic hardware kit” listed in the kit contents was not very descriptive at all and as a team that had never used shifting gearboxes before, we assumed the cylinders were included. The webpage has since been corrected, obviously.
We ordered early enough that we were able to place an additional order for the cylinders and had no problems getting the shifters or cylinders in a timely fashion.
I mentioned in my previous post that 558 is using a modified 2014 Drive in a Day chassis, attached is a picture of our practice chassis. We added the ability to run an un-equal spaced 8wd and bolted in some of the single reduction single speed gearboxes. We are very happy with how this chassis is performing. Please excuse the quality of the image.
I am slightly unclear on how VPs should be assembled given there is still documentation about the metal plate on your website. (In particular, the user guide which students used to assemble the motors makes no mention of the plastic plates)
Our gearboxes came with the metal and plastic motor mounting plates, they were assembled with the metal motor mounting plates. Is this a satisfactory motor mounting scheme with the absence of the bearing, or should they be swapped out for the plastic mounting plates.
Trent,
I updated the user guide but forgot about the quick start guide.
Please refer to This Guide for motor mounting.
With a BAG or 775 you should be fine with the metal plate, 550 or AM9015 you should replace to the plastic plate.
-Aren
It has a BAG motor so we should be fine.
Thanks
Did something change with the VersaPlanetaries or were they always so easy to mate together with a BAG motor? We assembled them with RS-775 & RS-550 motors last year and still had some minor binding after several attempts from 4 different individuals. Both VersaPlanetaries went together very smoothly this year on the first try with BAG motors.
The new bearing gussets are very nice. The ‘end’ gusset is very easy to bend at the same point with imprecise equipment, allowing us to add a long roller intake on top of a plate.
We were happy to find the 7:1 VP ratio. It matched our intake roller speed to our drive train speed very nicely.
One product I’d like to see in the future is a 1/2" hex-hex shaft coupler. We’re getting away with a beefy 3D printed Nylon coupler on a low-torque application for now, but an Aluminum coupler with built-in shaft collars would be nice for high-powered applications. The printed coupler went through many iterations for tolerance, strength & brittleness before the final iteration, which works like a champ.
On another note, I’m surprised the teams surrounding the IFI warehouse aren’t screaming ‘free USPS shipping on a single low-value item if you send us team t-shirts or 3D print us something’. I wanted to order a 10:1 gear kit by itself and the shipping was more than the part. It wasn’t a huge deal - we tacked it onto a larger order a week later, but it also meant we got our production ratios a week later than desired.
Now that I’ve stopped in with a team that has some more vex parts, I thought I’d post my opinions.
Overall, the quality of the parts/packaging/documentation is very, very good. The ball shifter is small, light, and functional. It does a good job of shifting on the fly, and spends almost no time in the neutral position. Many of the products have very neat features, like the two sets of holes for the CIM’s to go with different pinions, and the really neat profile shift gears with different teeth and same pitch diameter. These are really neat parts to use in FRC.
There are two parts that I’m not a big fan of, and these are the 40 tooth dog gear, and some of the pinions. The bearings (which come pressed/locktited into the gear) stick out the end, which is a little weird. Once you pop the bearing out to replace it with one that actually fits, you’ll notice that the hole is oversize, and you’ll need to get some locktite. The dog pockets are also way bigger than they need to be. It would also be nice to see fillets on the 40 tooth gear like there are on the 44. I don’t have a vex dog with me, but the CAD model shows no fillets there either, unlike the AM ones. We’ve found that these fillets make a lot of difference. Those right angles are huge places for stress to concentrate.
The issue with the pinions has no easy solution and isn’t a vex problem, but the retaining clip for the CIM shaft has too big of an OD, so it catches on whatever gear the CIM motor is driving. This makes swapping out a CIM pretty tricky.
Saw this today. Anyone else have issues with the VEX mecanum wheels? I saw earlier reports of issues with the 6" wheels.
http://blog.spectrum3847.org/2014/02/day-29-mama-said-thered-be-days-like.html I hear 4265 had similar issues.
I agree with the mecanum wheel issue. There’s two ways these things fail. The rollers come loose, and the plastic wheel itself shatters. I broke a 6 inch one dropping it on the floor.
One more question for the vex guys, why is the slot in the dog shifting shaft so long? It’s significantly longer than the travel of the cylinder.
You’ll find that’s the case for most dog shifting gearboxes you can buy. I would assume it just makes the whole setup more tolerant inaccurate cylinder placement. Although I’d be curious to hear what the reasoning is from vex.
The total width of the vex slot is 0.821 inches. AndyMark uses 0.48", which in my opinion is reasonable. We’ve used 0.275" in the past. Vex’s ball shifter requires perfect cylinder alignment, but it works because they have a nifty coupling, the same that’s used here.
The three CIM DS gearbox confuses me. There is 1.316" between the plate and the gear closest to the plate, and there is nothing in this space. I understand why this room is useful if you’re looking to add a PTO with a pulley, but I don’t see why that extra space is there in the normal model. The could probably sell spacers that are 1.25" shorter, and have shorter shafts.
Sprockets go in that gap (for a WCD team).
There are valid reasons for all the points you’re raising, and your assumption that because you do not immediately understand them they must be silly/wrong is unfair.
These are all super trivial complaints and have no bearing on the functionality of the product. Why would you expect anything other than the bearing that is currently in the gear to fit perfectly (for the record, we loctite every bearing we press)? Why would you want the dog pockets smaller? What if you were going to use this gear for a larger gearbox, say to disengage a winch? Would you want a larger dog?
Have you really seen a dog fail because the teeth didn’t have radiused corners? I haven’t. The weakest portion of a dog is the threaded hole. If anything the corner that you want radiused is at the base of the tooth, not the vertical edges. We have run unradiused edge dogs with zero issue.
Perhaps you should consider applying to VEX and then you can design their products?
How much clearance do you run for a 1.125 flanged bearing? Did this change with the loctite? I seem to recall you using some small fasteners to retain bearings as well. Any insight would be appreciated.
You’re right. These vex people are pretty darn smart, and I’m not saying I think their designs are silly, I just don’t understand them. So, I’ve reworded my thoughts as questions.
1.) We are doing a drive system where the wheels are driven, by chains, so that the sprockets run through the gearbox. We are using #25 chain and we have about 0.75" extra room. I think the extra space is for a team who wants to use a WCD with two 15 mm belts, as the space is slightly bigger than 30 mm.
2.) Why is the shifting slot longer than the travel of the cylinder? Does anybody know the advantage to having this be around 2x longer than a traditional setup?
3.) The traditional dog gear enters into the gear 0.125", so that you can have a 0.125" pocket in a 0.375" gear while keeping 0.25" remaining for a normal sized bearing. The vex dog gear has the bearing sticking out the back a little bit so that there is more engagement between the dog and the gear. When doing this, you loose the advantage of having the flange on the bearing. Does anybody know why this is?
4.) Why aren’t there fillets on the dog/dog gear? I’m not talking about the ones on the outline of the dog pocket, but between the face of the gear and the vertical face of the pocket. A while ago, I made some of these dogs out of steel. Switching to a ball nose endmill and getting even a small radius on all the corners fixed our shattering dog problem.
These are all super trivial complaints and have no bearing on the functionality of the product.
Yes, they do. Having to remove the plate to remove a shaft to remove a CIM motor is a little silly, just because the retaining ring is a little big, but I don’t really see how this can be fixed.
Why would you expect anything other than the bearing that is currently in the gear to fit perfectly (for the record, we loctite every bearing we press)?
Because it’s advertised with a 1.125" bearing bore, not with a hex bearing pressed in with locktite. And besides, having a flanged bearing with the flange just sitting out in the middle of nowhere isn’t “fitting perfectly” to begin with.
When we bought our gear, it said nowhere that a bearing would come with it. I’m not complaining about our free hex bearing, but we planned on putting a not-hex bearing in the gear.
Normally we use 1.1245 holes, because at that size, there isn’t much slop in the fit. The vex bearing bore on one gear was 1.13.
Have you really seen a dog fail because the teeth didn’t have radiused corners? I haven’t. The weakest portion of a dog is the threaded hole. If anything the corner that you want radiused is at the base of the tooth, not the vertical edges. We have run unradiused edge dogs with zero issue.
I’m not sure my first post was clear. I’m talking about a radius between the horizontal surface of the dog, and the vertical surface used to transfer torque to the gear.
Yes, our kicker in 2010. The problem went away after using a ball nose endmill.
Do you really use an endmill with no radius to cut your dog gears?
Again-I think vex products are among the best we’ve seen from an FRC supplier, but I’m just curious as to why some parts are the way they are.