www.robowars.org

RoboWars Australia Forum Index -> Builders Reports

Micro Magnum, Team Magnum, NSW
Goto page Previous  1, 2, 3 ... 44, 45, 46

Post new topic   Reply to topic
  Author    Thread
Eidg



Joined: 27 Nov 2015
Posts: 10
Location: Switzerland


 Reply with quote  

Nice Design, which is different to the usually seen spinner, so i like it.
But there is one thing you might consider: Your upper Wheel mounting looks fragile.
So i suggest to support the wheel on both side or to use a really solid axle.
For example, i use a toolsteel axle with nearly 12mm Ø, which is supported on both ends in my feather.
The second point, it seems you have a slotted hole for the upper tire axle, what is the function?
It is good to use a lot screws, but don`t you think the wall thickness between the srew holes is at certain points a little bit to thin?

Post Fri Mar 30, 2018 8:00 am 
 View user's profile Send private message
MoonSet416



Joined: 25 Sep 2016
Posts: 432
Location: Sydney


 Reply with quote  

Thx.
Yeah mounting on both sides would be stronger.

The slot serves two purposes. One is to adjust the pressure between the upper wheel and the main wheel. The other is that when the upper wheel is under pressure, it will have a tendency to press up against the main wheel so it will have even more contact. Also, a part of the upper wheel's load is actually taken by the main wheel.

The big amount of screws are actually there to compensate the lack of connecting lugs in the chassis (my early designs actually had lugs, but the machinist said those would be hard to manufacture even with rounded corners.). The actual strength of the parts is something I still haven't tested or simulated. Backup plan is to either switch to fewer bigger (probably m8) bolts or to add lugs to the design.

Post Fri Mar 30, 2018 4:21 pm 
 View user's profile Send private message
MoonSet416



Joined: 25 Sep 2016
Posts: 432
Location: Sydney


 Reply with quote  

Update:

Updated top wheel design.



Ran a few simulations in SW. For all the aluminum pieces the bolt holes didn't seem to be a problem maybe because of the pocketing in the plates weakening the rest of the plate down.

However it's a bit different for the steel parts (wedges), which have no pocketing. Now I have an F1 front spoiler.

Post Sat Mar 31, 2018 7:21 pm 
 View user's profile Send private message
Eidg



Joined: 27 Nov 2015
Posts: 10
Location: Switzerland


 Reply with quote  

Well the forces which actualy lead to tensile forces on the screws are mostly not the biggest challenge.
In your case the walls arround the screws are thin an if you simulate lateral forces, there will be a complete different result.

Post Sun Apr 01, 2018 2:23 am 
 View user's profile Send private message
MoonSet416



Joined: 25 Sep 2016
Posts: 432
Location: Sydney


 Reply with quote  

Sorry not so sure what you meant by lateral forces... Did you mean these?





In these cases the screw holes do seem to have very high stress concentration.

I then experimented with fewer, larger screw holes, but that created even higher stresses.

Post Sun Apr 01, 2018 12:31 pm 
 View user's profile Send private message
Eidg



Joined: 27 Nov 2015
Posts: 10
Location: Switzerland


 Reply with quote  

Well it`s not easy to communicate about such things only with writing, but i think you made it.
Your first simulation looks pretty close to what i was thinking about.
Can you simulate the forces ont the small top surface instead of the front wedge?

Post Wed Apr 04, 2018 7:41 am 
 View user's profile Send private message
MoonSet416



Joined: 25 Sep 2016
Posts: 432
Location: Sydney


 Reply with quote  

Well the deformation looks... umm... postmodern





With deformed result off the red is a bit concerning even at 1000N.

How do you reckon can this stress concentration be reliefed?

EDIT: btw I do also have a question about fixturing: should the tapered portion of a countersunk hole also be a part of the fixture? (the sims were done without those as fixtures)

Post Wed Apr 04, 2018 11:36 pm 
 View user's profile Send private message
Eidg



Joined: 27 Nov 2015
Posts: 10
Location: Switzerland


 Reply with quote  

Hello

The most important thing about FEM-Simulation is, it only works if you stay under the yield strenght from the used material.
It is also Important to select a appropriate mesh size, due the fact it will affect your simulation.
And of corse the forces and the fix point has to be set accurately.
So without nowing the used material and the picture diagramm, it`s, as my engineering teacher says, producing colroed pictures Wink

To answer your question, i would use the countersunk area only.

Post Sun Apr 08, 2018 12:00 am 
 View user's profile Send private message
MoonSet416



Joined: 25 Sep 2016
Posts: 432
Location: Sydney


 Reply with quote  

Thx for the advice.

Post Wed Apr 11, 2018 12:05 pm 
 View user's profile Send private message
MoonSet416



Joined: 25 Sep 2016
Posts: 432
Location: Sydney


 Reply with quote  

Update on Abomination:

In the previous version of Abomination I left an error in the design. One of the threaded holes for motor mounting was just next to a near vertical feature, making it impossible to actually drill or tap that hole.



The makeshift solution is to make the top half of the weapon mount a separate part so that there's nothing protruding where the mounting hole is. However this does bring new problems: keeping the weight more or less constant I only have 3mm Ti for the top half.




The bot after stripping off the weapon and wedge (still working on those, coming later)

Post Wed May 02, 2018 10:30 am 
 View user's profile Send private message
MoonSet416



Joined: 25 Sep 2016
Posts: 432
Location: Sydney


 Reply with quote  

Update on Abomination:

Moved the weapon motors way back. Now my weapon won't hit my own weapon motors. Yay!



Designed a new inverted wheel. The caster wheels I'm currently using are too wide and heavy. The new wheel is also slightly larger at 5.5cm.



PU tread (to be lathed from a PU round bar)


One half of the printed core

Post Fri Jun 22, 2018 11:46 am 
 View user's profile Send private message
MoonSet416



Joined: 25 Sep 2016
Posts: 432
Location: Sydney


 Reply with quote  

A weird time to write a builder report isn't it...

It has been a busy and somewhat unfortunate week for my robot. The way I mounted the weapon motors onto Contraption prevented me from using the right sized belt. Currently the motor goes straight into the hole in the weapon mount, and the ribs of the belts just won't clear the pulley. I tried a longer belt with some 3D printed tensioning idlers with ball bearings in the middle but those exploded under high speeds.

Going into this year's Nationals I don't think I will have a weapon unless some miracle happens. Lessons were learned about how poly-V belts behave (when they don't work) and hopefully Abomination would be a better bot.

But for now, I'll just be a W E D G E

Post Tue Sep 25, 2018 6:33 pm 
 View user's profile Send private message
  Display posts from previous:      

Forum Jump:
Jump to:  

Post new topic   Reply to topic
Page 46 of 46

Goto page Previous  1, 2, 3 ... 44, 45, 46

Forum Rules:
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

 

Last Thread | Next Thread  >
Powered by phpBB: © 2001 phpBB Group
millenniumFalcon Template By Vereor.