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Misfortune - Barton Robotics - NSW
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Dylon



Joined: 09 Nov 2006
Posts: 631
Location: Newcastle, NSW


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Misfortune - Barton Robotics - NSW

Name: Supernatural
Class: Featherweight
Weapon Type: Spinner
Drive: Cordless Drill, micro-switches
Weapon Drive: Fan motor and pulleys
Batterys: 18v 1800mAH Nicads
Armour: 3mm - 5mm Steel



Last edited by Dylon on Sun Jun 29, 2008 1:01 pm; edited 2 times in total

Post Mon Jan 08, 2007 11:12 pm 
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Spockie-Tech
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Joined: 31 May 2004
Posts: 3160
Location: Melbourne, Australia


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Nice concept CAD work, but lacking in a few practical design details.

E.G.

you cannot support drill motors by the motor only and expect them to stay together

A KE Bar spinner will put huge shock loads back through its mounting point. a single base-plate supported bearing will bend the plate in nothing flat, you need to extend that bolt to the top of the frame

you might as well move those top batteries, lower the lid so the wheels can stick out the top and gain the ability to drive inverted

anyone else spot any glaring errors there ?
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Post Mon Jan 08, 2007 11:17 pm 
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Dylon



Joined: 09 Nov 2006
Posts: 631
Location: Newcastle, NSW


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is that better anything else i have left out or need to do(this is my second bot never made one like this before so any help would be grateful)

can get it to invert because of the fan motor

Post Tue Jan 09, 2007 12:10 am 
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Ajax
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Joined: 17 Jun 2004
Posts: 298
Location: Sydney


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That is a good concept drawing. but as Spockie said there are problems.

1/ Make the main suport blocks for the gear box close the the wheels.
Have a suport block for the motor, but doesn't need to be as big as the gearbox one.

Have a look at my cad for Little brute http://www.robowars.org/wikka/LittleBrute

I also have a support for the output shaft. you shouldnet need that.

2/ For the weapon I would recomend a 1" (25mm) shaft with two bearings in a bearring block then drive the blade from that.
Ref:- http://www.robowars.org/forum/album_pic.php?pic_id=1361

In the pic there is a single bearing block with two bearings and a two bearing block with single bearing arrangment.

Both of these setups will work well.

3/ the weapon motor will need a much stronger mount.
Recomend to make a frame for the weapon motor to be bolted to.

4/ have a look at making it invertable.
Larger wheels, slight configuration change, etc
It will be a down fall in battle.


Also have a look at some other Build threads to see how other roboteers are mounting motors.
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Post Tue Jan 09, 2007 1:06 am 
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Dylon



Joined: 09 Nov 2006
Posts: 631
Location: Newcastle, NSW


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thats the best i can do without going up a wheel size

Post Tue Jan 09, 2007 2:35 am 
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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I don't think that will drive very well inverted, plus the weapon will be angled up so much that it would never hit anything - you might have to weight invertibility against effectiveness (never easy).

Engineering-wise, it might be easier to mount the motor facing up, which lets you bolt directly to the bottom plate with just some small spacers under the motor mounts. The weapon shaft would have to be longer but you need some room for a bigger bearing anyway. I dissagree with Ajax on the weapon shaft size: the weapon bar and the support bearing are close together and you could get away with a 3/4" or 20mm shaft to save weight. It looks like the weapon shaft is made from a large bolt - we have found that bolts really suck for this as the steel is quite soft - it might not seem that way but it's been proven time & again that they bend.

In the CAD, you have small pulleys that look like they use a round belt. Be aware that small pulleys can transmit less power before slipping compared to larger pulleys and that round belts really suck for robot use. If you really have to use smaller pulleys, timing belts work well. Larger pulleys weigh more and the aluminium Stenco pulleys can help you there.

I don't see any way in the drawing to tension the pulley. belts come in standard sizes and they never fit just right. you could make slots in the base plate for the 3 motor mounting bolts so the motor can slide back a little.
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Post Tue Jan 09, 2007 6:51 am 
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Daniel
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Joined: 30 Aug 2005
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Location: Gold Coast


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Keep the inverted design. You've removed quite a bit of material to get the slopped back which will make it lighter. And it looks a lot better too. Just needs a skid block at the front so it'll drive well upside down without rocking onto its nose.

The cutting tips on the bar are too aggressive. They'll blunten down quickly and you'll loose a lot of material if you try to resharpen them. Also spinning bars have a lot less momentum then a disk, so if an aggressive edge like that digs into some soft armour the weapon won't have the momentum to push itself out the other side and your weapon will get stuck. Try drawing a line from the leading tip of the bar back to the center axial and then add an extra 10 degrees onto that. Then it'll have a good hitting edge that shouldn't dig in too much.

Post Tue Jan 09, 2007 8:18 am 
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dyrodium
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Joined: 24 Aug 2004
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If you wanted (after I get back from robowars) I could help you out in designing a blade that could be cut by oxy precision. They did my disks pretty well and it's cheap as for the weapon bar and a suitable material. It would limit it to a 2D line design but you can still put some funky teeth on teh end, and that way you can make them protrude out of the bar, not recessed like you've got now, as highlighted that will blunten fast and you'll be stuck with no material left to sharpen again. Smile
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Post Tue Jan 09, 2007 8:38 am 
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Valen
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Joined: 07 Jul 2004
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you want it to dig in.
the goal of a high KE spinner is to transfer all your energy into the other bot in the shortest time possible. If you just grind away at them then they arent going to take much damage.
Its the difference between 15 hits with a normal claw hammer and one hit with a sledge, same energy, different impulse.
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Post Tue Jan 09, 2007 8:59 am 
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Daniel
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quote:
Originally posted by Valen:
you want it to dig in.
the goal of a high KE spinner is to transfer all your energy into the other bot in the shortest time possible. If you just grind away at them then they arent going to take much damage.
Its the difference between 15 hits with a normal claw hammer and one hit with a sledge, same energy, different impulse.


Impulse? Are you sure your using the right terms? You can't add impluses from seperate hits together to compare claw hammers with sledge hammers. Impluse is used for comparing the momentum of different objects within a single system. Such as comparing the momentum of the motors to the momentum of the speedos when the robot hits a wall.
I also now that if I wanted to disable my opponent I would hit them with one seldge hammer rather then 15 claw hammers. Does more damge to the internals rather then pecking at the armour.

Post Tue Jan 09, 2007 9:22 am 
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Dylon



Joined: 09 Nov 2006
Posts: 631
Location: Newcastle, NSW


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if i run the fan motor upside down the front end of the robot will be really high

Post Tue Jan 09, 2007 11:28 am 
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Nick
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Joined: 16 Jun 2004
Posts: 11802
Location: Sydney, NSW


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Just a suggestion - from the one view I can see, you would only lose the sloped front but it should be possible to make the total hight the same or less. A trick is to cut a hole in the base so the centre of the motor sticks through slightly, saving 5 to 10 mm. you will also find that having the belt on top makes it easier to service, which you will really appreciate after a few events!

It's all up to you - we are just throwing suggestions to see what sticks. It's already a very worthy first effort - most builders are hard pressed to make a good wedge Laughing

Perhaps I missed the info - what will the base be made of and how is the shell and the base held together?
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Post Tue Jan 09, 2007 12:24 pm 
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Dylon



Joined: 09 Nov 2006
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Location: Newcastle, NSW


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the base will be made of steel not sure what type, probly about 2 to 4mm thick depends on wat the max thickness is for the gullotine, i want the sides of the shell to be welded to the base and i want the top of the shell to be removable so i can get inside, i gotta give my uncle a call to see what metals he can pick me up for nothing

Post Tue Jan 09, 2007 12:34 pm 
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Dylon



Joined: 09 Nov 2006
Posts: 631
Location: Newcastle, NSW


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this is with the motor upside down may look different to the others because i had to redo it on rhino 2 cause i ran out of saves on rhino 3

Post Tue Jan 09, 2007 2:06 pm 
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Nick
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Joined: 16 Jun 2004
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Well, its not as pretty as the first version, but the weapon end looks stronger to me. Its just an educated guess, but if the whole thing is 4mm steel, its likely to be overweight with a reasonably heavy weapon bar. 2mm steel is likely to flex too much (I know 1.5mm definitely does!) You might want to look at making a flat 5mm aluminium base and a one piece steel shell.

About the weapon bearing block: I checked out my catalogues and assuming a 20mm shaft, a reasonably stong bearing has an OD of 47mm. If the block is aluminium, you would want the block to be about 70mm square. The height of most 47mm bearings is 14mm, so the minimum height of the block would be 28mm for two bearing plus 3mm for a retainer lip. If you can spare the extra weight, spacing the bearings apart will make the assembly far stronger. You can also make the assembly stonger by using a roller bearing at the bottom. they take extremely high side loads compared to roller bearings and will last longer in this application.
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Post Tue Jan 09, 2007 7:30 pm 
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