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Micro Magnum, Team Magnum, NSW
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MoonSet416



Joined: 25 Sep 2016
Posts: 431
Location: Sydney


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quote:
Originally posted by Glen:
Thinnest hardox is 3mm (3.3mm actual). Is this for an antweight? It's probably easier to get it made from titanium Smile Can have it CNC'd easily then.


The idea of changing the material sounds great. Any steels that come at 2mm thickness? (Ti would also be ok but it is more expensive and would make the robot underweight.)

Last edited by MoonSet416 on Fri Feb 09, 2018 9:49 pm; edited 1 time in total

Post Fri Feb 09, 2018 9:47 pm 
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MoonSet416



Joined: 25 Sep 2016
Posts: 431
Location: Sydney


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quote:
Originally posted by Dylon:
sounds like a cheap drill press would solve a lot of these hole related problems you are having Wink


Just had a look on Ebay... Never realized they were so cheap. Thx.

Post Fri Feb 09, 2018 9:48 pm 
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MoonSet416



Joined: 25 Sep 2016
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Location: Sydney


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Update: So it seems like that getting 2mm 304 stainless steel sheets is quite easy, but I do have concerns regarding its hardness. From you guys' past experience is 304 "combat effective"?

Post Fri Feb 09, 2018 10:25 pm 
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MoonSet416



Joined: 25 Sep 2016
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Location: Sydney


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Update:

As I wasn't able to compete at the recent FMB event, I have done a few weapon tests. And I have had some problems with the weapon system on Contraption.

The first test was done a while back and it was just a regular spin up and spin down thing. The weapon was fairly quick to spin up thanks to the dual motors, but problem occurred when I decided it's time to spin down and end the test. As soon as I pulled the stick down the belts came off the pulleys and flopped around. Luckily aside from the belts getting slightly damaged by rubbing against the spinner, no further damage was sustained.

After that test I thought that the problem was caused by me forgetting to turn off the brakes of the weapon ESCs, so as soon as I pulled the stick down the brakes were engaged and the sudden deceleration might have destabilized the belts. So I turned the brakes off while the ESCs were attached to a Y-splitter.

Just now I did a second test. The weapon spun up just fine, and after it was at full speed I tried hitting a piece of wood. and then I spun down. After this test I found that the left side belt was off again, but the other belt seemed fine. See pic below.



So I'm trying to figure out what happened, and I have a few guesses. First, when I programmed the ESCs, I actually just turned the brakes off on one of the ESCs due to the Y-splitter. (electronics is still a big puzzle for me) Second, the idlers, which are now just ball bearings, are too narrow for the belt (belts are about 10mm wide but the bearings are only 6mm). As a result, if the belt is slightly off to one side, the tension in the belt will let it slip off to that side even further.

Which one do you guys think is more likely? Or did I miss something?

Post Sat Feb 10, 2018 10:21 pm 
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Nick
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Joined: 16 Jun 2004
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My guess is the idler wheel being too narrow and not having cheeks to keep the belt in place.
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Post Sat Feb 10, 2018 11:04 pm 
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MoonSet416



Joined: 25 Sep 2016
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Location: Sydney


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Yeah that's probably a big part of the problem.

Just now I found out that the motor mounts (basically hose clamps) might also be responsible as the motors are not exactly horizontal.

Post Sun Feb 11, 2018 12:31 am 
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Nick
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that could also be an issue - does the motor pulley have side cheeks?
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Post Sun Feb 11, 2018 7:50 am 
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MoonSet416



Joined: 25 Sep 2016
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Location: Sydney


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No they are just plain pulleys with grooves cut into them.

Post Sun Feb 11, 2018 12:12 pm 
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maddox



Joined: 21 Dec 2006
Posts: 779
Location: Belgium


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Stainless 304 is only a tad better than C52 mild steel. IMO, not worth the effort/pricetag.

I rather would look for titanium, and as you write, with 2mm it's lighter than steel, so, buy a bit thicker then.
2mm 304 stainless steel equals 3.65mm grade 5 Ti.

Post Sun Feb 11, 2018 11:31 pm 
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MoonSet416



Joined: 25 Sep 2016
Posts: 431
Location: Sydney


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My motor shaft is only 3mm long and I need at least 1mm of ground clearance so that's where the 2mm thickness came from.

But you are right about 304. It's soft.

I guess one option is to have a wider bar made out of Ti so that it weighs the same.

Post Mon Feb 12, 2018 1:06 am 
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MoonSet416



Joined: 25 Sep 2016
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Location: Sydney


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Update:

Claymore with experimental Ti weapon. The amount of weight I was trying to get and the low density of Ti meant I had to use more of a disk design, so here goes my bite depth.

Post Sat Feb 17, 2018 4:27 pm 
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Nick
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You can't use thicker Ti to get the right weight in a bar? I could probably find you a suitable piece.
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Post Sat Feb 17, 2018 4:37 pm 
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MoonSet416



Joined: 25 Sep 2016
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Location: Sydney


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My motor shaft is only 3mm long so even with the current 2mm disk I have 1mm ground clearance.

EDIT: ah just realized... I didn't have the weapon in the right direction, the actual bite isn't as bad as in the pic but still it's less than the steel bar.

Post Sat Feb 17, 2018 4:40 pm 
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Nick
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How is the disk fixed on to the short shaft? I think its going to come off after a couple of impacts if it is only pressed on.
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Post Sat Feb 17, 2018 4:43 pm 
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MoonSet416



Joined: 25 Sep 2016
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Location: Sydney


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There is a 4*M2 bolt pattern on the motor can so I'm using that to mount the blade.

Post Sat Feb 17, 2018 7:46 pm 
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