Re: Rhino track failier?
 

It seems like you're misinterpreting the suggestion of reaming. The suggestion was to use a reamer on the plastic molded part after it ejects from the mold, not on the injection mold itself. This would allow the manufacturer to hit tighter tolerances on the hole diameter than can be achieved through molding alone, and without any risk to the mold. This is called "rework" and is often avoided in the real world because it is time-consuming and potentially labor intensive at high volumes (higher cost). It's not desirable, but if a manufacturer is in a position where it is the only way good parts can be sent out the door it is sometimes a reasonable course of action. However, Andy stated it is not clear whether this tighter tolerance would even make much of a difference.

I would say "a reamer? oh that's easy enough to test on a few parts", but it sounds like AndyMark is unable to reproduce the problem on more recently molded parts (actually a good thing, but frustrating if you're troubleshooting the issue...). So it would be difficult to evaluate the effect of reaming without a failing baseline for comparison.

Re: Rhino track failier?
 

Going one step further, I'd like to point out that you can't ream a hole in the injection tool, because the tool has a positive feature to create a hole :)

-Brando

Re: Rhino track failier?
 

Just as a quick solution for any tram with a 3d printer, I would suggest printed pulleys out of abs plastic, we are running printed pulleys because we used different treads and have had no shattering problems. Our design is based on Andy's however it is longer to accommodate our longer tracks.

Re: Rhino track failier?
 

I know you meant on the Part itself, not the mold, but I'm concerned about shattering since although reaming is a light process, the injected plastic is very brittle and could snap or fracture under very light stress. Again, my team is modifying the 3D part to increase structural integrity before printing. If someone could try reaming and see how goes that would be great.

However, I do not think the problem lies in the tightness of the bearing recess, but in the thickness of it's walls. The recess has very little support along the edge of the bearing, and when it is under a shock load such as after crossing the rock wall, it shatters. This is what our 3D model adresses, by filling in the large gaps around the recess, we add extra, and constant support throughout the arc of the pulley's rotation. If anyone has thoughts on this I'd love to hear.

-Jacob

Re: Rhino track failier?
 

Also, beside the Pulley cracking issue, has anyone noticed any other problems?
Our tracks, which admittedly have not been run very much, have displayed no problems whatsoever as of yet, but we did get one of the first sets, so problems are bound to arise.

-Jacob

Re: Rhino track failier?
 

Another update:

Here is a picture showing our pulley improvements for Rev4. The guys working on mold said that they were working on adding the ribs yesterday, so this change is progressing well. We should see new parts in a couple of days.



Also, we are keeping a log and summary of what all is happening on this web page.

At this time, we have contacted (emailed) all of the customers who have contacted us regarding this issue. So, if your team has not heard from us about this and you think that you should have, please send an email to sales@andymark.com.

Sincerely,
Andy

Re: Rhino track failier?
 

Thanks Andy. I think that addresses the problem our modified 3D model fixed. It's nice to see you guys paying such close attention to this issue.

Re: Rhino track failier?
 

Another update for today:

We've got good news and bad news.

The GOOD NEWS is that the pulley mold modification is done and we have some first run pulleys. They look good so far, and we are testing them now.

The BAD NEWS is that there was much sinking around the inner bore when we reduced that bore to 0.754". So, we won't have Improvement #5 as I mentioned earlier today. We will have Improvements #1-4.

Our mold tool has is a two cavity mold. The tool makers changed the inner bore to 0.754" on one of them, but they left the second one at the original size. They are changing the one back today and tomorrow so that they are both at the original bore size. This eliminates the change which helped users add in a bushing if they wished to do so. With these new Improvements (1-4), I don't think that this bushing addition is needed. It would have been nice to have it, but since it caused sinking trouble with the material, we quickly gave up on that feature.

Sincerely,
Andy B.

Re: Rhino track failier?
 

Has anyone added a bogie wheel to help maintain a little more constant tension:eek: in the front of the rhino drive? We've got ours completed and I got a little nervous in the service when I only saw a turnbuckle tensioner. I'm just an old tanker and frankly don't care for having track casualties in the middle of competition. I'm sure I'm going over the top but...if it can crap out it will for our team. haha

Re: Rhino track failier?
 

This won't add anything to the solution of the problem with the plastic pulleys but I figured I would ask to see if it is an option. What would the cost look like if these were machined from aluminum instead of plastic injection molded and is it cost prohibitive? Some teams including mine would probably pay extra for metal rhino pulleys. The performance wheels run more than the plaction wheel products so is that a similar parallel?

Obviously it is a little late in the season for a new run of products but is that option on the table or is it just too expensive in this case?

Re: Rhino track failier?
 

No, we are not going to offer aluminum versions of this pulley.

We strongly believe that our Rev4 pulley is very strong and will handle the application well. We have ran our first tests today using these pulleys and beat up our test mule like crazy. We will post a video shortly.

We are now running production of the Rev4 pulley and will have them available to ship out early next week (2/15-2/17).

Sincerely,
Andy B.

Re: Rhino track failier?
 

Here is a video showing the testing we have done to the Rhino Track Drive drive base during the past two days. The first half of the video is with the old pulleys (Rev3). The second half of the video used the new pulleys (Rev4).

The pulleys, both Rev3 and Rev4 held up very well during these tests. The only break we had was on a Rev3 pulley after the 2.5 foot drop during the first portion of the video.

Andy B.

Re: Rhino track failier?
 

Thanks Andy for doing all this testing and communicating with all of us on CD. It was interesting seeing how you did your testing and the level that you went to in doing bad things to the Rhino track. This kind of public transparency is really amazing.

The ultimate survival test would be to take the battery and cRio off and put the mule into a cardboard box and ship it via UPS to the East or West Coasts. :rolleyes:

(UPS does a great job on packages under 30 lbs, but anything heavier, like the mule is problematic. I've received my fair share of heavy damaged stuff via UPS)

Re: Rhino track failier?
 

We just received a box of Rev4 pulleys. The parts are still slightly hot, as they literally just came off of the mold machine.

If you have sent us an email claiming cracked or fractured pulleys, then we are sending Rev4 replacements out today via Ground delivery. If you have sent us an email wanting replacements but don't have cracked Rev3 pulleys, then we are shipping those out on Monday.

Andy B.

Re: Rhino track failier?
 

Andy,

This is awesome! I love that FRC Suppliers solve problems like FRC Teams. Quick iteration and quick implementation!

I may have missed it from earlier in the thread, but have you emailed all the teams that ordered Rhino tracks with Rev 3 pulleys? I just ask because I'm sure there will be teams that ordered the Rhino system without realizing a cracked pulley until it's too late (aka at competition). These are the types of teams that wouldn't be checking CD or Lunch with Andy (which I watch religiously!)

Thanks for all your work on this and keeping all of FRC "rolling"!

-Mike