pic: what is cooking

[sanddrag]

Originally Posted by Hachiban VIII

Why not spare your machinist a tremendous amount of trouble and cut all those holes yourself with a hand drill?

Are you joking? It would take way more effort to hand drill a bunch of round holes than to throw the drawing in a CAM program and throw a plate in a CNC. I like it hoe it is and it the plates appear to be sufficiently strong (might be worried about the later stage gears though).

[Drew Hopman]

Thanks to ASRC Aerospace we can get this cut out on the wire edm that they have, either that or the water jet.... The machining ability that we have gained is amazing! I have looked over some of the stress factors and I think it should work because it is ¼” thick plate for the sidewalls. I would like to commend Jeffery on his skills considering he is only in 8th grade but has mastered inventor and has the ability to think in a mechanical nature will be a great asset to the team.

[Nikhil Bajaj]

I'd be more concerned about the strength of the gear teeth, especially in the later stages...if you take a CIM down to 2.2 rpm...you're going to be multiplying the max torque you can exert (it'll be around 90-100 oz-in when you trip the 40 A breaker) and if your free rpm is 2.2 rpm...then your gear ratio is somewhere around 2400...

240000 oz-in is a LOT of torque. be absolutely sure your gears can take it...you may have to step up the pitch a bit

but i totally agree...that amount of engineering proficiency and gumption in an 8th grader has the potential to be amazing...i look forward to future work.

[Karthik]

Originally Posted by Drew Hopman

I would like to commend Jeffery on his skills considering he is only in 8th grade but has mastered inventor and has the ability to think in a mechanical nature will be a great asset to the team.

An 8th grader designed this?!?! I'm floored. This is cool on so many different levels. Jeffrey, your design skills are phenomenal for someone your age. Secondly, it's great to see FIRST inspiring someone so young to tackle such big challenges in their spare time. This is what it's all about. Kudos.

[Rohith Surampudi]

wait...8th grader...thats amazing wow thats really food, i was thinking you were a veteran senior...Your team is really lucky to have you

Keep up the good work

[Not2B]

Originally Posted by Nitroxextreme

I agree with the torque concerns...

But how can you test something like that...

There are lots of different CAE / FEA type packages to do the testing. Of course, you could also do it old-school. Do it by hand. I don't do this very often, but... I'd check the hub, the spokes, and the teeth in different calulations. Have to estimate the forces - remember that start and stop are very much higher than forces during drive.

I know there are people out here that would do a much better job of explaining this than I would, but rest assured, you can do a good job by hand calcs. One of those things you learn in school.

[Jeff 801]

Originally Posted by nikkibajbaj

I'd be more concerned about the strength of the gear teeth, especially in the later stages...if you take a CIM down to 2.2 rpm...you're going to be multiplying the max torque you can exert (it'll be around 90-100 oz-in when you trip the 40 A breaker) and if your free rpm is 2.2 rpm...then your gear ratio is somewhere around 2400...

240000 oz-in is a LOT of torque. be absolutely sure your gears can take it...you may have to step up the pitch a bit

but i totally agree...that amount of engineering proficiency and gumption in an 8th grader has the potential to be amazing...i look forward to future work.

it is not the small CIM but the large CIM to be clear.

[Nikhil Bajaj]

Originally Posted by Jeff 888

it is not the small CIM but the large CIM to be clear.

ah, well then...

free speed of around 2500 rpm down to 2.2...gear ratio of 1136...at your max current of 40 A, then that's 1136*240 oz-in = 272700ish oz-in, and then considering dynamic loading you need to multiply that by at least a factor of 2 for safety one would think. 550000 oz-in is a pretty hefty requirement. Although, to be honest you will probably never ever ever see anything in FIRST that requires that sort of reduction to do something. Unless next year's game is pick up an elephant and hang your robot on the bar carrying the elephant...which WOULD be pretty sweet to see aside from animal rights issues...

Also consider that every mesh you make decreases efficiency by a few percent.

Just things to keep in mind. Keep up the good work.

[Jeff 801]

Originally Posted by nikkibajbaj

ah, well then...

free speed of around 2500 rpm down to 2.2...gear ratio of 1136...at your max current of 40 A, then that's 1136*240 oz-in = 272700ish oz-in, and then considering dynamic loading you need to multiply that by at least a factor of 2 for safety one would think. 550000 oz-in is a pretty hefty requirement. Although, to be honest you will probably never ever ever see anything in FIRST that requires that sort of reduction to do something. Unless next year's game is pick up an elephant and hang your robot on the bar carrying the elephant...which WOULD be pretty sweet to see aside from animal rights issues...

Also consider that every mesh you make decreases efficiency by a few percent.

Just things to keep in mind. Keep up the good work.

the large gear reduction is for the speed that the arm gos up

if it has that much strength than i need # 35 chain instead of # 25

[Nikhil Bajaj]

Originally Posted by Jeff 888

the large gear reduction is for the speed that the arm gos up

if it has that much strength than i need # 35 chain instead of # 25

So are you just trying to reduce the speed of the motor? IE, is maximizing torque the concern or do you just want it to move slower?

[Jeff 801]

Originally Posted by nikkibajbaj

So are you just trying to reduce the speed of the motor? IE, is maximizing torque the concern or do you just want it to move slower?

both