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| As Murphy as my witness, things happen and will continue to happen. - Pavan Dave [more] |
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#1
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pic: Another stripped VexPro gear
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#2
29-04-2016, 14:07
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Re: pic: Another stripped VexPro gear
For other teams to identify potential failures before they happen, would you mind expanding on the circumstances that led to the failure?
Specifically:
We noticed a similar failure (but in a 14 tooth), that can probably be attributed to sudden impact combined with materials that don't have impact resistance as a strong point. There's quite a lot of good learning (and fun!) to be had going down the failure root cause analysis road. Last edited by Mechvet : 29-04-2016 at 14:09. Reason: formatting
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#4
29-04-2016, 15:55
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Re: pic: Another stripped VexPro gear
Hey FRCGuy are you sure you don't want my 2 lightly used 24 tooth Vex gears?
Cause...  It's probably too late for me to broach you steel gears. I also don't have 24 tooth steel gears to start with and I doubt I can get them fast enough. Going to put these on my list of 'coming soon'...
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#5
29-04-2016, 16:15
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Re: pic: Another stripped VexPro gear
Just in case it hasn't happened yet ...
I'll bet the VEX folks would like to hear from you. I'm guessing that they will want to know if A) they need to either include a caution with their parts to help users avoid exceeding the loads the parts are designed to sustain, or B) they need to investigate a batch of parts that might have been manufactured badly, or C) they perhaps need to tweak their product's design. If you are at the championship, I'll bet they are there too. Blake
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#6
02-05-2016, 10:27
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Re: pic: Another stripped VexPro gear
Quote:
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#7
02-05-2016, 10:39
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Re: pic: Another stripped VexPro gear
Quote:
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#8
02-05-2016, 11:23
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Re: pic: Another stripped VexPro gear
Quote:
The push broach looks like this (this one is from Dumont): http://www.andymark.com/product-p/am-2204.htm It fits in either a hydraulic or arbor press. The 20 tooth steel gear I did for other teams look like this before I broach them: http://www.andymark.com/Gear-p/am-0186.htm You know that intelligence test where you put the round peg, in the round hole and the square peg, in the square hole? In this case you push with about 1,100lbs of force until the round hole chisels out to a hexagon  Proving once and for all - brute force can solve problems. Last edited by techhelpbb : 02-05-2016 at 11:29.
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#9
02-05-2016, 12:16
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Re: pic: Another stripped VexPro gear
Is the output direct driving a wheel (ie output shaft going through a rigid frame)? Look into the possibility for relative motion between the output gear and its driving gear. This could be caused by loose transmission mounting or flexing of the plastic case. With extra load/impacts on the gears being part of this game and improper gear mesh (caused by relative motion between gears) I imagine this could easily happen.
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#10
02-05-2016, 12:18
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Re: pic: Another stripped VexPro gear
That exact thing happened to us (3230) at the Idaho Regional!
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#11
29-04-2016, 19:12
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Quote:
Ok, I'll provide the details in order. Wheels are 8" AndyMark pneumatics. Overall reduction is the standard 2-CIM ball shifter from Vexpro with the 60:24 3rd stage. We're pretty sure it happened while being pushed by other robots and hitting defenses. Thankfully, the guys from 254 came through with some extra gears for this. I'll try to find Vexpro tomorrow to talk to them about it. Also, if you think that's crazy, I'll post a picture of one of that we stripped today that only has three teeth left  .
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#12
29-04-2016, 20:11
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Re: pic: Another stripped VexPro gear
Quote:
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#13
29-04-2016, 20:16
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Re: pic: Another stripped VexPro gear
Steel final gears should be adequate to sort the issue.
Course they are heavier. Every year I try to avoid broaching stuff but I finally got fed up and bought a #5 5 ton ratcheting arbor press and Dumont push broach. Built a nice stand out of 2x4 with caster's for that 365lb monster. I also bought a rotary broach and holder but I am sorting issues out on that. I had 20 and 24 tooth Vex gears because I bought 2 dual CIM Vex ball shifters lightly used from an FRC team on eBay. So I actually have something to test with. Personally I just usually use AndyMark boxes. If figure as CSA sooner or later I am going to run into these Vex products. Last edited by techhelpbb : 29-04-2016 at 20:23.
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#14
29-04-2016, 20:21
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Re: pic: Another stripped VexPro gear
We had the same problem at waterloo, We sheared 3 Gears in 7 Matches, its the gears because we used two different gear boxes and they sheared on both
Congrats on making it to Worlds
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#15
29-04-2016, 20:53
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Re: pic: Another stripped VexPro gear
Quote:
More stress than the part was designed to withstand = It breaks. How do you know that you aren't exceeding their advertised ability to withstand static or dynamic loads? Instead of writing "it's the gears", you might need to write "it's our robot"? Blake Last edited by gblake : 29-04-2016 at 20:59.
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