Anyone have problems with the Extreme V-wheels cracking? I didnt think i had applied too much pressure to the wheels in adjusting the eccentric spacers, but maybe i had. Anyone experienced a bad batch of wheels that were more prone to break than others?
Could you elaborate ? Your ox design ? How many wheels are cracking , all or specific ? Could you have under torqued the wheels creating side play ? I will be following this thread .
I have at least four wheels cracked, including one that cracked so bad a chunk of the wheel fell off. They are on all 3 axis with no pattern to the failures. I did not have any issues during the build, the bearings all fit snugly but properly (hand press fit) and they are not under intense pressure as-is (can be rotated by hand). I've attached a few photos to show the failures. I just ordered a handful of new wheels from the OpenBuilds store today. Not sure what to do if this happens again.
I would be inclined to contact the seller and have them examine all the parts that comprise your set up , Make arrangements to send them the entire parts list that is hold the wheel on . That way they should be able to determine the root cause of failure . My guess is that if it was a bad batch all would be failing . Richard
Interesting fault - I will be most interested to learn the possible cause of this failure (my money is on incorrect thickness of the internal spacer ?). Tweakie.
@Dekes1, can you give us an approximate shipping date? (So others who purchased around the same time can take a closer look) Also, have they been exposed to any temperature extremes? (Just trying look at this from every possible angle)
These were purchased from SMW3D, who i understand to be an authorized OpenBuilds distributor. They were ordered on the 9th of Feb, but i don't know how long SMW3D may have had them in stock. To Tweakie's point, i did have two of the wheels where the internal spacer was indeed too thin and the wheels wouldn't turn when tightened. I had to swap out for thicker shims, but those two wheels are not in the count of ones that have cracked. However, if those two were too thin, could other slightly too thin shims cause the cracking? Are the tolerances that tight? Regarding temps, these were delivered during the core of the record breaking winter and were most certainly well below freezing during delivery, but they sat in my house and became acclimated to indoor temps long before they were installed. Thanks for everyone's feedback!
May I also suggest that you send one, maybe the worst one, for the attention of Mark at OpenBuilds Part Store. Irrespective of who sold it to you, Mark is the guy who went with these wheels, and he really is the one guy who will want to see the faulty wheel, and get an answer for us all. Gray
to quote Gray , I would also suggest you send all the parts that you used in the failing wheel's assembly . This will provide Mark the best chance for a full and complete analysis .
For those of you interested, I contacted the seller (SMW3D) and they confirmed a mistake in shipping. They had been experimenting with various hardness compounds in wheels and I unluckily got a set of experiemental wheels. They very gratiously shipped a new set of wheels at no charge and so far the new wheels are perfect. I must commend their customer service and recommend them for future purchases.
Any idea were one could find these wheels other than the open build? I am working on something that would require a lot bigger wheel than what these appear to be. Thanks Bill
I am pleased you got it sorted with a successful outcome - thanks for reporting back with the explanation to the problem. Tweakie.
Darrell, I understand your confusion with the SKU 900 Extreme V Wheels. Most of the pictures shown on that page are of the Solid V Wheel. This is the one that is correct: The deep v-groove in the center of the wheel is for use with the OpenRail system as it rides along the tip of a pointed rail rather than in the slot of the v-slot rail. And while these wheels can also ride in the slot of the v-slot extrusions, it is best to use the Solid V-wheel as there will be less flex due to the groove being filled. As for which size of wheel to use, if you are using plates from the Openbuilds store, the hole spacing is set for one size or the other and thus they are not interchangeable. Regarding the logic of optimizing for cost and mixing and matching delrin and polycarbonate wheels in a project, I doubt most users put that much thought into it. Most just go with a matched set, a decision which is generally based on either extreme budget constraints or sufficient funding to create a well crafted machine that is also a work of art. And while I will always use the polycarbonate wheels when the need is there, I will also use them at times when appearance counts. Delrin is generally relegated to utility pieces. Edit: The photos for the Extreme V-wheels have been corrected.
Thanks Rick, I appreciate your reply. I am preparing to build an Ox of sorts, but do not intend to use the standard plates. I realize the standard plates are preped for the regular wheels. I am going to use one of the new C-channel V-slots for the X-axis bolted to another piece of 20x80. Using acme screws all around. I gather you are saying, unless cost is a big issue just use all Extreme Solid Wheels everywhere vs the Delrin. So, concerning the mini-wheels, (just trying to understand) if I had say 60mm of space in one area for wheels, with the regular extreme solid being 24.39 OD and the mini extreme solid being 15.23 OD, I could use two regular or three mini, which would be better in your opinion?
Darrell, it all depends on the nature of the system and the forces applied. It might even work with just 4 of the small wheels. I did a mock-up of what an OX might look like with C-beams (found here) and I arbitrarily dropped 8 of the mini wheels on both sides. For anyone using the OX mainly for lightweight work, 4 would be more than sufficient. It truly all comes down to the forces, both in magnitude and direction. But all this is a subject for another thread. Let's try to keep this one focused.
Hello Joe, They are machined and have to be proven to be a good choice over the Delrin wheels. -Ronald
