here it is!









i guess the more pictures, the better
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The day I stop giving 100%, is the day I stop competing

Last edited by shreddy on Sat Apr 04, 2009 11:31 pm; edited 2 times in total

considering i have a whole lotta free time due to it being school holidays, i guess i had better start back on my robot

here is an overview of the design


here shows the internal bracing


5mm grond clearance this time with the new wheels


i still don't know whether the motor mounts should be made out of uhmw or Ali
and i still don't know what sort of of batteries i'll be dealing with yet, hence the box-section lengthening
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The day I stop giving 100%, is the day I stop competing

hopefully this will be my last version as i have now added everything but uhmw mounts for like everything, a 1mm steel plate on top to keep the wires in and the shell + pulleys and schtuff









it all now fits within 30cm and I have a shell!
not good pic coz it was dark and the camera could'nt focus :S
tis black!
any ideas on gettin the tyre off


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The day I stop giving 100%, is the day I stop competing

burn the tyre off...

with a car

I like your thinking
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http://au.youtube.com/user/crustydemonsully

The day I stop giving 100%, is the day I stop competing

I can never find where i put the car in my tool box - how about a jigsaw with a metal cutting blade?

clamp one side of the tire in a vice and crush it down and lever the bastard off

How about taking it to a Tyre place and paying them a few $ to do it in 5 seconds safely and easily on their machine ??
If they charge you more than $10 I'd be surprised..
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Angle grinder and cutting disc cut cross one side and itle fall off.
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Tim Team Reaper.

I'd go with Brett's idea on this. If you plead povity as a school student, they might even do it for nothin.
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well i have been thouroughly thinking this through and I think that a 3:1 reduction should be okay

based on team Run Amoks Weapon calculator and comparing it to mike calculations I should have approximately 1260 rpm, 5818 Joules and a spinup time of about 2-3 seconds. does that seem normal? the 5000+ Joules seems a little too high
btw, it is with a 7.5kg shell

http://members.toast.net/joerger/AskAaron/faq.html
bout 20 posts down you will see the link
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The day I stop giving 100%, is the day I stop competing

alright
there is a change in shaft setup now
ill be using a trailer wheel hub attached to the rim and it will have a pulley bolted onto it
hopefully someone can help me out there
the hub sould look somehing like this:


and here is a rough sctech of how the pulley should be attached with bolts to the bottom of the plate:

please excuse the roughness as i do not have the parts currently and therefore cannot cad them

p.s.the box-section will also be changed from 61x61x2mm to 65x65x4mm and the shaft will be welded into this at the bottom
p.p.s I GOT THE TYRE OFF!!! YAY!!!
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i think ill just bolt the pulley straight to the rim now and run a bushing in the middle of it

im so confused
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The day I stop giving 100%, is the day I stop competing

Have you been weighing the parts? That hub must weight several Kg and with all the other parts it looks like the bot would be over weight. If you drop the hub, you still need to keep it's function with the bearings and retaining the wheel on the axle. In the hub, notice that the bearings are Choices are:

Ball bearings: They are strong but heavy and they have a large OD i.e for a 1" shaft, they have about a 2.5" diameter. That means boring out a large hole in your pulley and making a large bearing block to go on the top of the wheel.

Needle roller bearings: As used by Glen, they have much smaller diameter and weigh far less than ball bearings. They have two problems; their outer shells are quite weak & need good support b) they don't take axial forces very well, so you will need to include a thrust bearing on either side of the hub. the bottom bearing should be a roller type, while the top one could be just a bronze disk as it won't be used much apart from during impacts. Needle bearings need to run on a smooth surface. For long life they should run on precision polished and hardened shafts, but for bots, just a machined smooth shaft will do.

Bronze bearings: even cheaper than needle roller bearings and about the same weight. They need to be lubricated regularly and need a polished shaft to run on. They can be as strong as roller bearings, but people have been noticing they have much higher friction. They also need thrust bearings.

What sort of axle are you planning to use? if its a smaller diameter solid shaft, I would think about ball bearings, if its 1" or larger, Bronze or needle bearings will keep the size & weight down. Personally, I would go for alarge diameter tube for the axle with needle rollers for bearings.

Because he only really has access to cbc for easy acquisition of parts I was suggesting last night he used a 30mm hardened shaft with the center drill out about 10mm, and a bushing on the outside. The shaft would be about $12 or so from cbc, and rapture never had any issues using a thick, chunky bushing. This way, you'd also be able to tap a big bolt into the top and bottom to make sure the shaft and shell stayed in place.
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YEAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAH