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Micro Magnum, Team Magnum, NSW
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maddox



Joined: 21 Dec 2006
Posts: 786
Location: Belgium


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As far as I know, the Equinoc drum uses bolts and pins, where the pins take the strain, no threads to shear off then.

Also, with the motor in the drum it doesn't have any exposed belts or such.

Post Fri Sep 01, 2017 2:38 pm 
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Nick
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Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW


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I was just thinking about how to protect the screw heads - The larger diameter on this drum has more room for pins
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Post Fri Sep 01, 2017 3:20 pm 
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MoonSet416



Joined: 25 Sep 2016
Posts: 436
Location: Sydney


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Good points... I will definitely look into having pins to secure the spinner.

Some update: Did a few changes to the spinner, now it does not have a tooth on the middle section, which is now made out of ali due to weight issues. The bolts are now countersunk screws. Good news is that it now has 1.5cm bite. Will be adding pins to it as well.

Due to the larger bite, the MOI to weight ratio is much lower now, but seeing other designs I found I needed more bite.

Post Sat Sep 02, 2017 4:53 pm 
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MoonSet416



Joined: 25 Sep 2016
Posts: 436
Location: Sydney


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I also plan to change my weapon belt to something else... Any ideas?

I saw Vanguard's smooth output pulley, which works great, but without a working tensioning device, I don't know if that will work for me... I then recall seeing Poorly Designed's two tiny V-belts... I wonder if those will work without tensioning...

Post Sun Sep 03, 2017 5:41 pm 
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Nick
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Location: Sydney, NSW


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V belts work better with loose tension than timing belt on a smooth pulley. All types of belt need some tension though and if you don't have a tensioning device, you will probably have to adjust the pulley diameter. That's what I do with Mr Mangle, but its only possible if you have access to a lathe.
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Post Sun Sep 03, 2017 6:19 pm 
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MoonSet416



Joined: 25 Sep 2016
Posts: 436
Location: Sydney


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Thanks for the info.

The more I think about it... The timing belt I'm using now has no problems spinning up, but it transfers impacts back to the motor, which is bad. However, I could potentially solve that by modifying my Tx so that my weapon is off when I don't hold the throttle, which protects the motor.

I guess I need to look into this issue further...

Post Sun Sep 03, 2017 7:12 pm 
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MoonSet416



Joined: 25 Sep 2016
Posts: 436
Location: Sydney


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Another thing... I've been looking for fight videos ever since the end of the nats, but I still couldn't find all the fights so far (especially the early ones on Day1). Does anyone happen to find those on Youtube?

Update on Contraption other than the weapon:

The side panels are now much lighter, leaving more weight for the weapon. (Most of the parts were designed to be made by a laser cutter, while in reality they are made by CNC, which opens up the possibility for lightening pockets.)

Post Sun Sep 03, 2017 8:18 pm 
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Valen
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Joined: 07 Jul 2004
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Location: Sydney


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It's not the motor driving that's the problem its the sudden stop. All the spinning stuff stops in an instant. So the motor can is spinning and then the belt stops dead.
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Post Sun Sep 03, 2017 9:57 pm 
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MoonSet416



Joined: 25 Sep 2016
Posts: 436
Location: Sydney


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Sorry I didn't make myself clear... I meant that when the weapon was stopped/decelerated, the motor also had to stop because of the amount of grip the timing belt has. So yes you're right the sudden stop caused some problems.

I didn't quite get the motor can spinning part you talked about though... The stator couldn't really spin... (If it were to spin it should have ripped all the wires.)

I just watched the only fight video I could find again (vs Insanity) and I had some new findings. The weapon actually restarted twice during the match, of which the second one was very slow compared to a normal one. The weapon then died completely. But in the last two seconds of the video I saw the weapon twitching back and forth. The video ended there but I recall the weapon starting again with the ESC burning after where the video ended.

This is weird... The motor can still spin after the fight, and the ESC lasted longer than I thought it did. It seems more like the ESC failing when ever something touches the spinner.

Post Sun Sep 03, 2017 10:33 pm 
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MoonSet416



Joined: 25 Sep 2016
Posts: 436
Location: Sydney


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Update:

Switched to v belts after realizing that they are narrower than timing belts, thus giving space for tensioning devices. With V belts I had a lot more freedom on what shape the pulleys should be, so I designed a pulley with a recess for the thrust bearings, reducing weight and space needed.

With the extra weight I was able to increase the MOI of the weapon to a decent level. (about 40& more than current weapon)



However, that does mean that I had to do crazy things to the cylinder... (assuming it's made from steel)



I will try to make an ali version of the cylinder tomorrow, and I hope the new one will not need to be skeletonized. (It's gonna be thicker, so a bit less MOI for the same weight)

Post Fri Sep 08, 2017 1:58 am 
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maddox



Joined: 21 Dec 2006
Posts: 786
Location: Belgium


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How wide is that drumisk? And how big is the internal diameter?

Post Fri Sep 08, 2017 5:49 am 
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MoonSet416



Joined: 25 Sep 2016
Posts: 436
Location: Sydney


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The two disks on the side are 16mm each. The central cylinder part is 40mm. (I'm still confirming with the CNC guy if he could do this.) internal diameter is around 120mm.

Post Fri Sep 08, 2017 12:03 pm 
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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Is somebody thinking about a hub motor, Mario? Wink
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Post Fri Sep 08, 2017 3:32 pm 
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maddox



Joined: 21 Dec 2006
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Location: Belgium


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With 120mm internal, why not?

Post Fri Sep 08, 2017 3:48 pm 
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MoonSet416



Joined: 25 Sep 2016
Posts: 436
Location: Sydney


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LOL hub motor does sound like an interesting idea... A hub motor would also directly add some extra MOI to the weapon beyond powering it. Not sure if it would work with this bot but definitely something I will consider for future builds.

Any recommendations of hub motor of this approx. size?

Post Fri Sep 08, 2017 6:01 pm 
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