The Dethinator

I went ahead and did the Kinetic Energy calculations for the bot.

edit - will fix when I have accurate dimensions of the bot.

Dan Curhan wrote:

ummm.... welll.... uhhh.... we haven't had to yet lol. Miami will be its debut performance. But if we had to, everything does come apart... And we have lots of spare motors and they're all interchangeable...
and no, it's not ABS. in fact, I had to google ABS cause i'd never heard of it before...

Legos are ABS. thats all you need to know

Back from final build, and this bot is whatever it is now...

Fought us EVERY SINGLE STEP OF THE WAY.

3 redesigns, 12 different part layouts, thousands of wasted parts(most of which had to be hand-made by us), hundreds of hours, and 3 different motor types. Jeff deserves a medal for his time because he hasn't slept in the past month...

If it doesn't do well, you can't say that we didn't TRY to get it working right, because we did... It just refused to cooperate at any point...

Hope it does well... Not quite as fast as we had hoped, but it is pretty fast...... We shall ultimately see how things go on Sunday. High hopes.

Do you know what the gear reduction is? With the two in wheels on the outside of the shell i have to figure its atleast 5:1, the shell might not spin as fast as you wanted but im sure it spins up quick and has alot of torque.

it's a 1.34 to 1 pulley ratio from 17k RPM drive motor to drive wheel on shell. The drive wheel radius from the center is about 5 inches, so it's a little more than 5:1. We clocked over 1500 RPM with a tachometer... it's not impressing us cause we saw it spin at least double that with the old motor setup, but it's still not too bad. I'm editing a video covering the whole build-->competition process which I will post shortly...

Dan Curhan wrote:

it's a 1.34 to 1 pulley ratio from 17k RPM drive motor to drive wheel on shell. The drive wheel radius from the center is about 5 inches, so it's a little more than 5:1. We clocked over 1500 RPM with a tachometer... it's not impressing us cause we saw it spin at least double that with the old motor setup, but it's still not too bad. I'm editing a video covering the whole build-->competition process which I will post shortly...

I wouldn't be so anxious for a high RPM, if I were you. Higher RPM does mean a higher speed but it also means less torque. The faster you can get to your top speed the better. In my opinion anyway.

I've also noticed that the spinners with a high RPM are usually less stable than those with a lower, but still fast, spinning shell.

If you think about it like a fly cutter or an end mill, the harder the material is, eg. steel, you'd want to go slower than you would with aluminum. If you go too fast, you'd probably break your cutter.

SenaiERI

I'm actually not very worried about stability - everything is impeccably concentric and very well balanced, so it spins super smoothly.

BUT. it looks like we have sort of a clone type thing...


does that spinner look familiar?

Does the drum look familiar?!!!!!!

lol they competed in the friday group so i couldnt tell you much more about the shell spinner tho
Although its 4wd and they prob use banebots, we recomend them at the training session so of course everyone uses them lol

you mean shockwave2 lol
I cant wait to see it, i wanna know why they have holes in the drum, i guess they just arent as good as you alex lol, and then get to own them haha

Got back from latest build.
Things are finally working out....

Latest tweaks really helped.

Spins at 2250 RPM, motors no longer overheat, battery isn't getting killed as bad...

Current draw is probably a bit lower now(Blue LED now simply dims rather than shutting off when weapon is active).

Spins up really fast. Spins incredibly smooth now... Even more so than in Miami(if you can believe that).

Latest weight was 14.90 lbs

I am getting used to driving it. Tommorrow will probably consist mostly of Dan and Jeff working on Copperhead, while I learn how to really control Dethinator.

Dan will probably have a good video to post.

What did you do to fix the problem???

rjw wrote:

What did you do to fix the problem???

Not sure about all the details, but one thing that was done was putting the Steel Motor Shield, that had been around the motor when we got it, back on, because apparently it increases torque, reduces heat, and reduces current draw(or something like that).

Dan had assumed that it was useless before so he simply removed it for weight reasons, but we have no placed it back on the motors.

We also changed the idler to a thin Delrin wheel, which appears to be working better. Dan should be able to give you a much more detailed answer later tonight(they are still at the build and will be for a while).

In any case, that's great news...not sure about the spinup time, but if motors / battery don't overheat that that part is good!!

good luck at nat's

rjw wrote:

In any case, that's great news...not sure about the spinup time, but if motors / battery don't overheat that that part is good!!

good luck at nat's

I don't know if that is the actual spin-up to max, but it was definitely above 1500 RPM within 5 seconds.

Sure didn't take long to get to 2200.

When I was driving around, I decided to run into some cardboard boxes. Anyway, I just tapped the weapon switch for about 1/2 second to get it spinning, and run into the cardboard, flings it across the room and makes a decent hole in the cardboard(no videos of that though. Not that impressive to do that to cardboard anyway... but the speed it got within such a short time was definitely impressive.). It spins up really fast with those relays... Which is good.

Yeahhhhh those shields are motor heat sinks lol they only pull heat from the internals of the motor

Be honest,
Did my Blender Mini's shell influence you any?

MattTavares wrote:

Be honest,
Did my Blender Mini's shell influence you any?

maybe... Seems like a Dan question. I also think it had a lot to do with us being extremely overweight and needing to lose weight rapidly....

Your shell probably influenced the USF Team's Quasar a lot... Eddie spent several hours today milling triangles in his steel shell....

haha yeah it influenced eddie's bot more than ours lol. We didn't mill anything on it - we used a drill press and a hole pattern just figured out in CAD then scribed on the shell and center punched... then it still wasn't light enough so we milled into the corners of the shell... it was a long process all done by hand... we have no CNC stuff or anything like that

For anyone who is interested, my documentation is done for Dethinator - you have to dig to find the CAD drawings... they start on like page 40 or something... but here. My documentation. All of it. All 70 pages of it. All put together in the last two days. I like auto document feeders.... ;P

Dan Curhan wrote:

For anyone who is interested, my documentation is done for Dethinator - you have to dig to find the CAD drawings... they start on like page 40 or something... but here. My documentation. All of it. All 70 pages of it. All put together in the last two days. I like auto document feeders.... ;P

Nice. The only problem I spotted was missing dimensions from several of the CAD drawings (big no-no in college, but they'll definitely let it slide for the competition). Other than that, it's pretty verbose for the amount of time you took to put it together.

Jeff L wrote:

Dan Curhan wrote:

For anyone who is interested, my documentation is done for Dethinator - you have to dig to find the CAD drawings... they start on like page 40 or something... but here. My documentation. All of it. All 70 pages of it. All put together in the last two days. I like auto document feeders.... ;P

Nice. The only problem I spotted was missing dimensions from several of the CAD drawings (big no-no in college, but they'll definitely let it slide for the competition). Other than that, it's pretty verbose for the amount of time you took to put it together.

And make sure that there the right distance from the drawing too!!!!

How fast was this supposed to go?

What are YOU up to, Will?

Quote :

How fast was this supposed to go?