Pulverizer Build Diary

[Mega Masher]

Btw, Monster Shred!!!!!!!!!!!
http://i1280.photobucket.com/albums/...ps24ca3bbd.jpg

[Mega Masher]

Max, I'm not getting those as I'm going to make my own using pulleys-see my post of the parts list a few hours ago. Max, we've already discussed this earlier in the thread. I do actually do research myself you know!
Ellis, good idea, will have a think about that. I think that triangulation would help loads, but wind resistance is very important, and may slow the bot down. I only chose the rectangular shape for it's compactness and the fact that it would be easier to make.

[Eventorizon]

I don't like to do this but this will not work.

Those motors do 21'000 rpm ungeared. with the 14T and 36T pulley reduction the drive shafts are doing 8166RPM. With your 73mm wheels your robots top speed is 69.8mph... that is stupidly fast. That is uncontrollable to the extreme. And that isn't taking into account the speed when spinning. Most machines don't go over 10 or 12mph.

I have used that accelerometer in university projects and you will require custom programming to make it work with your set up. That in itself may be months of work to make sure it is safe and reliable. You will need an on board processor as well. If that gets damaged your machine will be useless.

Finally, going by the name you have found the US bot 'Death by translation'. That machine took 3 years to build by 2 very experienced engineers and a dedicated software programmer. And after all that it wasn't very effective, even in a large arena. In the Robochallenge arena you will never get it up to speed before you are hit by another robot.

Full marks for trying to be different but there are a whole bunch of reasons why no one has bothered.

[RogueTwoRobots]

Also, the shafts on the motors look very short and no bigger than 3-4mm in diameter. Getting a timing pulley to fit on that securely will be extremely difficult. If you do manage to do it (say it's a 10-tooth pulley) you'd need a corresponding pulley with 210 teeth to bring the wheel rpm down to 1000rpm (random figure assumed for melty brain spinner). A 44-tooth pulley of 5mm pitch is usually about 75mm in diameter, so that's already larger than the 73mm wheels you plan on using. Suffice to say a pulley with five times the amount of teeth will be around the 375mm diameter mark, so your wheels would need to be ridiculously big to fit the pulleys in, and your robot would become very unstable and/or overweight as a result.

[Mega Masher]

So what do you suggest for a reduction system then
DBT had no reduction system and that worked pretty well

[Max]

The motor used in NBT had 50% more power and rotated at 6000rpm rather than 21000 (3.5 times less).
But you are using 2 motors where it only used one, if I was you I would use mod 1 steel gears, with a 10 tooth on each gear and a 60 tooth on the wheels giving a 6:1 ratio which should make it just about manageable with your design. A lower gear ratio like 6:1 will probably be faster than a high one like 3:1 as the motors are under much less load so can use their power, this will also make it accelerate faster so you can get to your max. speed faster.
From what I understand you don't need an H-bridge as the motors only need to rotate in one direction at full speed every time, so a simple solid state relay for each one (rated at 100A continuous from RS components) will work great and be very simple. Remeber KISS.
You have to make the body and tooth very strong, I'd make it circular using a bit of large diamter thick wall steel tube (5mm) with supports on the inside (like DBT), if you don't have the equipment to weld or cut material this thick I would get it made by someone like Mario having first made a simple wood/plastic model to check everything fits. The tooth will have to be hardox or tool steel so will need to be waterjet cut.
I'd contact the guys who made DBT and ask if you can use their code and use the exact same components as they did, if this is not possible you will have to write it yourself. You can always use their's to begin with then modify it or re-write it at a later date but it would help if you had their's as a starting point as you know it works.

[Mega Masher]

Thanks for that Max

[Mega Masher]

Btw, Merry Christmas everyone!!!!