www.robowars.org

RoboWars Australia Forum Index -> Builders Reports

Windhammer - WA
Goto page 1, 2, 3  Next

Post new topic   Reply to topic
  Author    Thread
Windhammer



Joined: 19 Jun 2004
Posts: 338
Location: Roleystone WA


 Reply with quote  
Windhammer - WA

Hey Guys n Gals,

It's been a good 7 years since I've been on this forum and it's nice to see robot combat is still popular and the quality of bots is awesome.

I woke up the other day with the desire to build and I've come up with this today.

[/URL]

As you can see, 2 x 18v Grinders as drive powered by 2 x 18v 2.0ah Li-ion.

Weapon will be a 4kg hammer flail type weapon powered by a 18v grinder also hooked up to a hobby king style 18v 5ah.

I've ordered 2 x 85amp botbitz for the drive and plan on using a servo activated relay for the weapon motor.

The base is 10mm chopping board with 3mm steel sides and weapon mount. The grinders are simply mounted directly to the base using bolts into the thread in which the handle would normally be.

I'm far from the most technical guy so please suggestion advice would be appreciated, issues I expect will be the flail being to heavy/long, breaking gearboxes and smashing my own bot.

More to follow in the coming days Smile

Post Mon Aug 17, 2015 11:47 pm 
 View user's profile Send private message Send e-mail MSN Messenger
haz



Joined: 15 Aug 2011
Posts: 169


 Reply with quote  

I think you need to rethink your drive. Those motors will be way too fast for drive on such large wheels.

The weapon is going to be pretty bad, as in it will mostl likely break the first time it hits something. Get a biz bar watercut, it seems to be cheap as piss for most of the other australian spinners. Also consider mounting it in a different way, belt drive it from a brushless motor and controller, or at least put a belt drive in from your grinder (maybes take it out of the case also)

I wouldn't bother using the grinder batteries either, go on hobbyking and grab some cheap 5s packs.

Yes the length of the robot will mean it will be a nightmare for it to drive

Look up how other spinners and other robots are put together and take some notes. Its a very neat idea but I seriously cannot see anything good coming from this
_________________
For my stuff
http://bodgeitandhope.blogspot.co.uk/

Post Tue Aug 18, 2015 12:05 am 
 View user's profile Send private message Send e-mail
maddox



Joined: 21 Dec 2006
Posts: 779
Location: Belgium


 Reply with quote  

A few small remarks.

A normal 4.5" anglegrinder runs around 7Krpm. Those wheels look like 125mm.
But we'll calculate with 100mm wheels.

.1m x 3.14 x 7000=2198m/minute. That's 131kph

If you want to use the thin ali cast gearbox housing with only 1 bolt, I garanty that it will crack.

3mm steel.... if it's hardox, bissalloy or something simular, than it's ok.

Chopping board. Nope, you'll have to change to real HDPE.

Post Tue Aug 18, 2015 1:33 am 
 View user's profile Send private message Send e-mail Visit poster's website MSN Messenger
Windhammer



Joined: 19 Jun 2004
Posts: 338
Location: Roleystone WA


 Reply with quote  

Thanks for input guys, I needed a reality check.

In reference to the drive, the maths shows 131km/hr.. But when you consider friction drag, weight and acceleration I'm thinking it'll travel at a much lower speed. Am I wrong?

Haha, I expected a negative comment towards the chopping board, weight considered it'll be a temporary base during the build process before I transfer the outline and drill holes into a steel or Ali plate.

The hammer flail is going to have to stay for the time being as I've already bought them and it goes with the team name Wink After testing IF it's truely crap I'll swap to a disk.

You're right about the length of the bot, I've swapped it sideways now.

The gearboxes will have 3 mount points; from the base, top and L bracket attaching to the top of the unit.

Plenty left to do, waiting by the mailbox for my ESC.

[URL=http://s521.photobucket.com/user/mrdoug1/media/Mobile%20Uploads/image_zps7a4gxsbu.jpg.html] [/URL]

Post Tue Aug 18, 2015 5:08 pm 
 View user's profile Send private message Send e-mail MSN Messenger
maddox



Joined: 21 Dec 2006
Posts: 779
Location: Belgium


 Reply with quote  

Yes, you're right. The top speed will be a lot lower. But even on 30% you're talking 40kph+.
A motor running on 30% of the rated RPM, isn't an efficient motor, but a good heating element.

10mm thick HDPE will outperform swisscheesed ali or even steel plate any day of the week, even if the weight of the foamed steel or ali sheet is lower.

More mounting points is a good thing.

Post Tue Aug 18, 2015 6:13 pm 
 View user's profile Send private message Send e-mail Visit poster's website MSN Messenger
Eventorizon-GB



Joined: 15 Nov 2013
Posts: 111
Location: Ripon, United Kingdom


 Reply with quote  

Most FW's are geared to travel at around the 11-12mph mark, some faster, some slower depending on the robots design and its weapon intent.
As an example, my robot Conker only manages 10mph but the 4WD means it gets there very quickly.
A robot called 720 can theoretically do over 15mph, allowing it to make high speed attacks with its spinning drum giving it great engagement, but it used to wheel spin a lot, burning up its tyres.
A robot called Satanix is a 13kg rambot, and can probably do close to 18mph (thats a guess but... its very quick!)
So, as you can see its design dependant. You don't really want to be doing less than 8mph I would say, else you will be out manoeuvred by other machines.

Post Wed Aug 19, 2015 1:30 am 
 View user's profile Send private message
Valen
Experienced Roboteer


Joined: 07 Jul 2004
Posts: 4433
Location: Sydney


 Reply with quote  

it's kind of akin to this, if we assume everybody has the same motors (which to a first order they do) your gearbox setup is like being in 5th gear. All the time.

Imagine trying to leave the lights in your car in 5th gear. It's not going to work so well, and if you try and do it fast you are going to burn something out.

Everybody else is in 1st gear, so they may not have the ultimate top speed, but they can get off the line well.


I think the average gear ratio people are using is ~16:1 or perhaps more, average output RPM is ~600. Your grinder is probably going to be ~2:1.
_________________
Mechanical engineers build weapons, civil engineers build targets

Post Wed Aug 19, 2015 7:27 am 
 View user's profile Send private message Visit poster's website AIM Address Yahoo Messenger MSN Messenger ICQ Number
Windhammer



Joined: 19 Jun 2004
Posts: 338
Location: Roleystone WA


 Reply with quote  

Thanks for your replies.

I've taken your points onboard and I'm going to try my best to save this build from failure. I'm thinking the only way to make the drive effective is by lowering the weight significantly so the grinders with get up to speed faster.

The hammer flail is going to have to go, and is replaced with a undercutter style setup.

This will bring the bot down to borderline hobby weight, fingers crossed this works..

Maddox mate do you have a recommended source of HDPE?

Post Wed Aug 19, 2015 2:44 pm 
 View user's profile Send private message Send e-mail MSN Messenger
Spockie-Tech
Site Admin


Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia


 Reply with quote  

Replace the back end of the grinders with drill motors and just use the grinder gearbox as a right angle drive with a bit of reduction. with those big wheels, it wont hurt to reduce the ratio a bit. Use a rubber uni-coupling of some sort between the drill and the gearbox to take reversing shock.

You will need an metal arm from the center (make a tapped metal insert) out to the edge of the wheel hub to move the drive point out from the hub, or you will just rip the plastic center of the wheel to bits with the thread.

Dont bother with abrasive discs on the weapon, they will shatter first hit, and dont have any reach anyway.

a lightweight large diameter saw blade (I plasma cut circles out of IGs saws to reduce the weight) will make nice sparks, but probably wont do a lot of serious damage unless you do manage to get their wheels (rare).

Bars are more destructive, but will munch up the grinder gearbox unless you put a loose slipping-disc drive to stop shock
_________________
Great minds discuss ideas. Average minds discuss events. Small minds discuss people

Post Wed Aug 19, 2015 3:31 pm 
 View user's profile Send private message Send e-mail Visit poster's website MSN Messenger
maddox



Joined: 21 Dec 2006
Posts: 779
Location: Belgium


 Reply with quote  

quote:
Originally posted by Windhammer:
Maddox mate do you have a recommended source of HDPE?



I have my prefered source. Unfortunatly, it won't do you a lot of good.

I live in Belgium.

Post Wed Aug 19, 2015 4:09 pm 
 View user's profile Send private message Send e-mail Visit poster's website MSN Messenger
Rotwang
Experienced Roboteer


Joined: 15 Jun 2004
Posts: 1586
Location: Vic


 Reply with quote  

We used right angle battery drills in Bender.
That’s a long time ago but I think they are still viable.

We never hurt a motor or a gearbox except one gearbox that took a big hit on the wheel from Demon.

More info on Benders build thread.

I do like the packaging combinations the right angle drives make posable.

http://robowars.org/forum/viewtopic.php?t=373&postdays=0&postorder=asc&start=30
_________________
Satisfaction is proportional to effort and results.

Post Wed Aug 19, 2015 4:37 pm 
 View user's profile Send private message
miles&Jules
Experienced Roboteer


Joined: 19 May 2010
Posts: 3969
Location: ipswich QLD


 Reply with quote  

i want to see this thing go mental….what if you swap the wheels for saw blades? it will defiantly leave its mark on the arena floor? Very Happy
_________________
Miles Blow - Julie Pitts
www.mulesfilm.com.au
www.wombokforest.com.au

-Pickasso- Vivid Sportsman champion 2015

Post Wed Aug 19, 2015 8:15 pm 
 View user's profile Send private message Send e-mail Visit poster's website
Windhammer



Joined: 19 Jun 2004
Posts: 338
Location: Roleystone WA


 Reply with quote  



Hey guys - I would mate but I'm hesitant to pull the grinder apart as having it as a whole complete unit with casing is convenient for mounting. A disk any larger than shown in the picture above will be touching the base of the robot, it's a design I'll be changing in the future though Smile


Saw blades as wheels!! Why didn't I think of that earlier
Laughing

Just waiting for the controllers to arrive..

Planning on using a pitchfork as a wedge on the rear.

Currently weighing in at 8.2kg

Post Wed Aug 19, 2015 8:50 pm 
 View user's profile Send private message Send e-mail MSN Messenger
Valen
Experienced Roboteer


Joined: 07 Jul 2004
Posts: 4433
Location: Sydney


 Reply with quote  

suggestion for you, what you have there is enough to drive around, perhaps get the ESC and radio up and running and drive the box around for a bit and see how it goes before you finish building stuff.
_________________
Mechanical engineers build weapons, civil engineers build targets

Post Thu Aug 20, 2015 8:31 am 
 View user's profile Send private message Visit poster's website AIM Address Yahoo Messenger MSN Messenger ICQ Number
Daniel
Experienced Roboteer


Joined: 30 Aug 2005
Posts: 2729
Location: Gold Coast


 Reply with quote  

Yeah, test it and see what happens. Best way to learn.
My guess is that with high speed gear motors, not very grippy wheels and not much weight over the wheels, it's going to be a real bugger to control. Lots of wheel spin and spinning in circles instead of driving forward.

And MPH and Kilometers per hour is a silly way of measuring speed for us. Our robots never travel a mile and most barely survive an hour. Meters per second works best. How many seconds does it take to reach the other side of the arena. I mean Maddox quoted 131mph, that's 36.6m/s second. Or as like to call it, hitting the opposite side of the arena in 0.131 seconds.
Or probably wheel spinning in circles for 5 seconds first. Very Happy

Post Thu Aug 20, 2015 10:38 am 
 View user's profile Send private message Send e-mail
  Display posts from previous:      

Forum Jump:
Jump to:  

Post new topic   Reply to topic
Page 1 of 3

Goto page 1, 2, 3  Next

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.