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Total Recoil - Chunkulator - NSW
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chunkulator



Joined: 27 Jul 2016
Posts: 219


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What those? Those are only the small test springs.

I looked at snail cams during initial design but came to the conclusion there would be too much friction for the sorts of opponent-into-the-roof forces I had in mind. The forces involved require ball bearings to tension and release and i didn't find a nice way to do it with snail cams where the bearing rides the cam and provides constant force during the tensioning stroke. I've already shown that my leadscrew system can do the tensioning, so the last question mark is the quick release.

Post Mon Mar 13, 2017 7:37 am 
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Nick
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Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW


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Can't wait for the first spring VS CO2 flipper match Very Happy.
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Post Mon Mar 13, 2017 7:47 am 
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chunkulator



Joined: 27 Jul 2016
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Indeed. If I can get it all to work reliably it should be lots of fun.

Post Mon Mar 13, 2017 7:53 am 
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Knightrous
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Joined: 15 Jun 2004
Posts: 8511
Location: NSW


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You can mitigate the majority of the friction using a roller bearing on the follower.
For this kind of design, I always look at the snail cam design because you can make it compact, changing gear ratios and springs can give you variable force and reload times and you can use a powerful brushless motor that only needs single direction control to both reload and trigger.
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Post Mon Mar 13, 2017 8:28 am 
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chunkulator



Joined: 27 Jul 2016
Posts: 219


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All good points. I suspect the chassis I have built is fundamentally the wrong shape for a snail cam, so I don't think I can easily try it out. I optimised the hinge geometry fairly hard for the leadscrew. However for V2 it's probably worth serious consideration. I suspect a different shaped bot entirely would be the way to go with a hinge point in front of the snail cam or a 4 bar arrangement.

Post Mon Mar 13, 2017 5:28 pm 
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Cpnwolfe



Joined: 29 May 2012
Posts: 454
Location: Rockhampton/qld


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I am working on a snail cam bot we can compare in june Razz
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Post Mon Mar 13, 2017 6:29 pm 
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chunkulator



Joined: 27 Jul 2016
Posts: 219


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Seems there will be quite a few flippers at vivid. Maybe I should also get my shaker bot Mr Tickles together to give them all a run for their money.

Post Mon Mar 13, 2017 7:52 pm 
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chunkulator



Joined: 27 Jul 2016
Posts: 219


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Successful test fire of the quick release mechanism today. Possibly a little underwhelming on a housebrick and a half (around 6 kilos). At least the dog was scared of it.

Here's the vid:
https://youtu.be/lmiS455yzN8

Post Sun Mar 26, 2017 6:58 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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Was that using the larger springs?
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Post Sun Mar 26, 2017 7:18 pm 
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chunkulator



Joined: 27 Jul 2016
Posts: 219


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Unfortunately yes. Maybe I need to stretch them more to make them really sing.

Post Sun Mar 26, 2017 7:29 pm 
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Nick
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Location: Sydney, NSW


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Yeah - I was just thinking pre-tensioning might help
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Post Sun Mar 26, 2017 7:39 pm 
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chunkulator



Joined: 27 Jul 2016
Posts: 219


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I bought some bigger springs off Ebay and test fired 6 kg of housebricks about 1.5m into the air. Ok, so it's no Citizen Flips but this is starting to look like a somewhat dangerous bot.

I now have a big brushless motor mounted on a homemade gearbox to tension the springs. I'm pretty proud of this gearbox given that it's built by hand out of 3mm steel only using a jigsaw, angle grinder, drill press and crappy gasless MIG welder:


Next I need to cut some holes in the sides of the SHS for the leadscrew lugs and fine tune some of the gear meshing. Then I'll be ready to test tensioning the big springs in situ in the bot.

Post Wed Apr 05, 2017 10:33 pm 
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chunkulator



Joined: 27 Jul 2016
Posts: 219


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I got the gearbox installed and rigged up to the quick release mechanism today:
https://youtu.be/mXKSp_NBTy4

I tried tensioning up it with one spring in it but it got jammed because the frame got pulled out of shape. I'm going to need to spend some time making the frame more rigid before I can reliably flip I think.

Post Sun Apr 09, 2017 7:29 pm 
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chunkulator



Joined: 27 Jul 2016
Posts: 219


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I welded cross members in place on the frame and it's nice and rigid now. Once I stripped down, realigned, and thoroughly greased the mechanism I got it reliably tensioning the big springs:

https://youtu.be/NMdsIIChilM

At some point I trimmed too much off the catch arm so it doesn't hold anymore. I'll need to make another before I can properly test fire it.

Post Sun Apr 16, 2017 9:13 pm 
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Cpnwolfe



Joined: 29 May 2012
Posts: 454
Location: Rockhampton/qld


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this is looking badass!
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Post Mon Apr 17, 2017 11:35 am 
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