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Author Topic: Team Tamper Resistant  (Read 1858 times)

echin

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Re: Team Tamper Resistant
« Reply #15 on: December 23, 2016, 11:50:59 am »
Thanks for the suggestion. I was already considering using planer blades, but didn't think to get them used. That should be much cheaper.

-Eric

BranYoung

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Re: Team Tamper Resistant
« Reply #16 on: December 27, 2016, 06:07:13 pm »
Brushless motors are definitely a huge benefit for drive. For flashing, I would recommend Rapid Flash as a quick and direct way to flash or the KK Flash Tool for more advanced bits

echin

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Re: Team Tamper Resistant
« Reply #17 on: December 31, 2016, 11:56:35 am »
It looks like I might not need to flash the ESC's. I'm using RC car ESC's and they seem to perform fairly well in my testing so far.

Here's a video: https://youtu.be/1i76PK-Ctg0

It does stutter a little on startup, but I was intentionally trying to stall the motor out and it never completely failed to start.

Unfortunately, I damaged the other motor while pressing on the pinion, so it's just one side for now. Once I have everything on the bot and fix the second motor (or buy a new one), I'll see if the drive still works and alter the ESC's accordingly.

-Eric

echin

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Re: Team Tamper Resistant
« Reply #18 on: December 31, 2016, 08:47:57 pm »
I finally got EH's drum on: https://youtu.be/jZbK1LaO39U

Compared to the last version, there is much less friction. I guess buying nice bearings payed off  :)

The idler shaft seems to be a bit angled after the test. I'll need to look into a more robust mounting method for it. Perhaps I'll attach it to the output shaft of the motor.

-Eric

BranYoung

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Re: Team Tamper Resistant
« Reply #19 on: January 01, 2017, 02:12:21 am »
Looks like great speed on the drive, definitely a big plus when going against other bots to maneuver. I used Turinigy 35A ESCs leftover from another drum beetle I had as well in testing before I flashed the afro escs. If the drag brake is 0, brake is locked out, and full power is given to the reverse it works equally well. The benefit that flashed Afros have is that they are really good at saving weight and storage as they are far flatter and more compacted. If there isn't a problem with it in your bot and you feel more comfortable working with basic programming as opposed to flashing they could be acceptable options.

jamisong

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Re: Team Tamper Resistant
« Reply #20 on: January 02, 2017, 12:13:02 pm »
I actually stay away from afros these days. The thermal design is inferior to single-sided boards with heatsinks. I'm a firm believer in the ztw spider escs as a result. red brick escs are also great if you have space; tons of thermal mass.

loving the rebuild! especially the black frame. robustness with an in-motor drum is always an issue because there are so many parts which need to either not break or stay perfectly aligned. dominant mode eventually narrowed down to a single-piece drum body from hexagonal stock with all the bearing and can features turned in. The most important part however is the singular long shaft which went though all the bearings and motor to keep things concentric.

Hope to see you at MassD!

-Jamo

echin

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Re: Team Tamper Resistant
« Reply #21 on: June 09, 2017, 09:25:36 pm »
I've finally managed to motivate myself to do things again after the FRC season.

I am attending Georgia Tech next year and I need a project to start optimizing my design for the resources of the Invention Studio. I think I'll design an aluminum 1 lb. bot or maybe an all aluminum version of Event Horizon sometime in the next few months.

Currently, I'm working on fixing the drum shaft alignment issue on EH that I saw back in December along with a few other things that I decided I didn't like.

Does anyone have any experience using a hole in a UHMW frame member as a weapon bearing? I'm considering doing this, but I'm concerned that a slight deformation of the frame could completely lock the weapon.

Log of today's progress is here: http://ericwchin.blogspot.com/2017/06/finishing-event-horizon-v32.html

rcjunky

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Re: Team Tamper Resistant
« Reply #22 on: June 10, 2017, 04:56:21 pm »
Uhmw is too soft as a bearing.
Andrew Burghgraef
Canadian Carnage Robotics

Great Hobbies- Canada's leading retailer of radio controlled models and related hobby supplies

echin

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Re: Team Tamper Resistant
« Reply #23 on: July 26, 2017, 08:02:56 pm »
I'm still making progress on Event Horizon slowly (working full time until school starts, so not much free time). The goal is to get it done before Dragon Con.

I've been thinking about an interesting flywheel flipper mechanism for the last few weeks.

The mechanism uses a three piece linkage with linkage arms as follows: 1)arm connected to the flywheel 2) arm connected to the flipper 3) arm that goes between 1 and 2 and is the same length as 1. The mechanism has two stable trajectories. It can freewheel (1 and 3 spinning, 2 stationary), but it can also travel in a trajectory where 1 and 3 move independently to power 2. These trajectories only intersect in the two positions where all of the linkage members line up. This has some cool properties:
  • It can shift between the freewheel state and the powered state with very little force
  • The shifting will always occur in the same spot every time, and the mechanism is inherently locked from engaging in every other spot, which should make it fairly resistant to accidentally firing
  • The mechanism should lose very little energy on a dry fire
  • The flipping arm is powered up and down
  • The mechanism can be powered with the flywheel running in either direction

This may have been tried before, but I have not found any record of it. If anyone has seen one of these mechanisms, let me know. I'd be curious to see how it worked (or failed to).

I'm currently working on a prototype 12 lb. bot to see how high the shock loads associated with engaging the linkage are. My calculations of the input/ output torque ratio show that there is a nearly instantaneous jump in torque when the mechanism first engages, but that the torque ramps up gradually after that. This does not seem right to me, but I can't find any errors in my math, so maybe it's right. If there really is a jump in torque when the mechanism shifts, I am concerned that everything might self destruct upon engagement without a large amount of structure or shock mounting.

Pictures of the two states:




-Eric
« Last Edit: July 26, 2017, 08:07:12 pm by echin »

jamisong

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Re: Team Tamper Resistant
« Reply #24 on: July 26, 2017, 09:25:13 pm »
woohoo Georgia Tech! Congrats! Yes, please do use the hell out of the free waterjet :)