Back in August Team 1114 was asked to construct a 6 wheel chassis to test out the latest version of the IFI traction wheels. Our testing featured six 4” x 2” Traction wheels with 3/8” id ball bearings. Our testing included many repetitions of heavy driving, impacts, quick starts and stops, and jumping the robot off a ramp.
Having not previously used the IFI traction wheels, I did some research into the problems that teams encountered with the first version of the wheels. Here were the major concerns:
“The treads come off too easily”
The new wheels come with large headed 1/8” aluminum pop rivets as opposed to the original standard headed rivets to help ensure the tread stays attached. We had no problems with treads detaching over the course of our testing.
“The rim of the wheel bends inwards, causing a structural failure”
The new wheels feature interlocking tabs between the rim portion of the wheel, and the side plates. These interlocking tabs are to alleviate the problems some teams encountered resulting from the rim portion bending in following a sharp blow to the perimeter of the wheel. Throughout our testing, we experienced no bending in this fashion despite repeated attempts to produce it.
“The fasteners came loose”
Last year, some teams complained about the flathead Phillips fasteners repeatedly coming loose between the side plate, and the rim portion of the wheel. The wheels now feature stainless steel button head screws with an Allen drive. The PEM (rivet nut) fasteners in the rim portion were also swapped out in favor of ones with nylock inserts. Throughout our testing, we experienced no loosening of these bolts. Teams must, of course, ensure that these bolts are tight on assembly.
Another nice new feature is the new bearing retainers, which are a welcome improvement over old bulky ones.
Our only real grievance about these wheels was on assembly. As mentioned previously, the wheels feature interlocking tabs to help prevent the rim portion from bending in. These interlocking tabs over-constrain the rim portion to the side plate making the bolt holes difficult to line up at times. This is due to the bend tolerance on the rim portion of the wheel. On assembly, we drilled these holes out to a loose clearance on the bolt. I am told by a representative from IFI, that this revision will be made to the production models.
All in all, we were very impressed with these wheels. We had no problems at all during the testing phase with these wheels. After going through our rigorous testing process, Team 1114 is fully confident that wheels can withstand the rigors of a full FIRST season. If the game calls for a wheeled robot, there is little doubt in our mind that these would be the wheels of our choice. The strength to weight ratio is exception, and the cost is not prohibitive. In short, these new wheels are a great improvement to an already top of the line product.
These v2 wheels worked out great for us, but I’ve also, just this morning, learned that there is a v3 design in the works. I’m confident that regardless of the further developments IFI takes, the new wheels released in 2007 will fully address the problems voiced last year. Remember, design is an iterative process.
A problem our team encountered was the PEM nuts actually completely separating from the rim parts. This was a huge problem with the screws also coming loose or if you wanted to change a tread. I suppose if the screws never come loose, it’s not as likely to be a problem, but I’m curious if it’s still happening. You could pretty easily tell by taking a wheel or two apart and seeing if any of the PEMs fall off.
Since the teeth don’t appear to be side chamfered, I am guessing that 1114 or one of their sponsors custom cut those, probably on a water jet or plasma cutter. (I have been experimenting with custom cutting steel sprockets on a laser table, to obtain precise shaft fit features such as the double-d found on the Globe shaft.)
Back on topic: this is a great drive train study and very useful info for any of us who are considering the new IFI wheels.
Very interesting. We suffered a plethora of problems with the v1 IFI wheels, but according to 1114’s data, most of them seem to be mitigated, if not resolved entirely. We may conduct a trial of our own on the v2 wheels, but up until this point, I don’t even think we were seriously considering using them at all. Thanks 1114 for the data!
And on another note, I’m also quite interested in the sprokets, but even more so on that transmission…
There was a thread a few months ago about aluminum sprockets, in which Tyler described how 1114 cut their sprockets on their CNC mill (Infact, I believe the example he showed was this exact sprocket :))
As to the wheels themselves, the rookie team we mentored last year used them, and their problems stemmed from the wheels loosening themselves unless you use loctite. The problem is when you use loctite, you break the press fit of the PEM nut into the side plate, and you have a useless wheel. Having a locknut now should resolve that issue nicely.
If the screws loosen up, then the torque on the wheels will cause the screws to tilt, which will then cause the PEM nuts to pop out. The screw acts as a lever to pry out the PEM. What you saw was a symptom of the screws loosening. I’ll double check our test models when I get home from school this weekend, and get back to you, but as long as the bolts are tight, this shouldn’t be a problem.
We’re in the process of prototyping with the IFI’s for the first time, and hadn’t been aware of the issues. I’m really glad to hear it sounds like they’ve got the kinks worked out.
I know I can ask IFI the following, but since you’re so close to this, perhaps you know:
1: Where there any outside dimensional changes, as we’re using the step file from the web site
2: When the V2 wheel would be ready (as we’re looking to order this week, and would obviously like to get the new wheels).
In case anyone else was wondering, the following is the status from IFI as of today:
“Keep an eye on the wheel page on the forums. We do not have any spec
released from engineering at this time. The forums will be posted to
when
new information comes available. the wheel should be available to
purchase
in late November or Early December.”
It is in my experience with these wheels that many of the more pressing issues took place with the larger diameter wheels. I had witnessed many of smaller thicker diameter wheels going through competition unharmed.
However use of the larger wheels such as 8"x1" wheels were not able to hold up. Keeping the wheels concentric ( mainly due to the retainer which has apparently changed ) and if the wheels experienced any side loading from robot impact or field element nasty things seemed to happen.
One of our main problems is that as the tabs bent inward due to stressing levers as you claim our plates began to bend outward. Using our large diameter sprocket that we had used catastrophic failure accured in such a manor that half of plate peeled away from the wheel. Before the match the screws had been tightened and tho the tabs weren’t in perfect condition but not terrible, it seemed as the screw had literally been ripped from the wheels.
Sounds like you are making changes to this so thats good. My question is tho look at your chasis and your initial support where the wheels tested under full load? It doesn’t seem that your chasis is the typical weight of a robot. Just a curiousity, was weight added before conducting your testing.
Also where the wheels put any side loading such that it would emulate impact from a robot? Our wheels performed perfect when in straight lines, its when we were hit or turned did problems occur. ( Mainly the hitting part )
Also will testing occur on the larger diameter wheels?
I enjoy the benefits of the wheels i.e. Size options, ease of assembly and use in application, weight ratio, but still concerned as the structural integrity. Maybe not of the smaller wheels, but of some of the larger wheels.
This week team 1114 received their V3 IFI Traction wheels. Earlier we addressed some of the improvements over the V1 wheels. While we thought that the V2 wheels were a large improvement over the V1, the V3’s are even better.
This 3rd revision is even lighter, and easier to assemble. The new rim portion uses more interlocking tabs and eliminates the PEM nuts all together. While we have still to test them in competition, our experiences in assembly have been better than the V2’s.
We used the IFI wheels last year. I was not happy with them. We completely destroyed one, although it was a direct hit with no protection. I’ll give them that, it was more our fault. But the treads came off 4 times in normal match play. One time the tread came off it caught in the chain which put us out of commission for one match. Finally we had to rivet the treads down to the wheel to keep them from coming off…
Good idea but needed work…we’ll keep it simple and grippy with the AndyMark KOP wheels, which are nice this year.
Uhh, I believe that is why the treads come with rivets in the first place? IFI even tells us how to do it properly. We used the IFI wheels last year and had no issues. We lost one tread in one practice round on Thursday because we didn’t rivet it properly but after we properly replaced it we had absolutely no problems. I am looking forward to the new and improved versions this year.
