New 15lb Bot

Ok. This is my first actual complete design and I need input from everyone.

Right now I am doing rough concept work, so I have no Solidworks or CAD done yet.

Basic principle is a ground up reworking of Dethinator(probably even renaming it).

It will be a full body spinner, only instead of using a cylinder, the shell would be frustum(truncated cone). The principle behind this would be the added defense against the numerous drum spinners populating the Lightweight class right now.

Using 3/16" or 5/32" 6-4 Ti, we would make a 14" diameter frustum with the angle on the sides at 45 degrees.

I was thinking of having it about 3.5" tall.

Now, for the things I need input on.

To spin the shell, I was thinking about using two Axi 2826/8 Brushless Motors. These would direct drive two 1.5"/1.75" Colson wheels that would contact a track on the inside of the shell. My question was, would those motors have enough torque to spin the shell up quickly? Their website calls them high torque motors, but I am uncertain. I can probably fit a 4120/14, but I want assume that I will, so my plans will mostly be with the 2826/8 in mind.

Also, in regard to the ESCs, will I want the ESC with the BEC or should I got with their "opto" line of ESCs?

Finally, I was thinking of going Li-Poly or A123 and wanted input and explanation of what exactly I needed.
Their website says that the motors use 2-3s Li-Poly/Li-Ion cells. This is 11.1VDC Li-Poly/9.9VDC A123 correct? Can you point me to the battery that I will want to use?

Thanks, Alan.

PS - Will try to get more detailed plans up by the end of the month

You shouldnt have any problem at all using the 2826, thats what matt and senai eash use and i think matt said on the RFL forum his shell weighed over 7 pounds.
As for and ESC i would recomend the jeti opto if your going to be using A123 or lipo batterys, i think we used a 77 amp when we used 2826's

Cody Harris wrote:

You shouldnt have any problem at all using the 2826, thats what matt and senai eash use and i think matt said on the RFL forum his shell weighed over 7 pounds.
As for and ESC i would recomend the jeti opto if your going to be using A123 or lipo batterys, i think we used a 77 amp when we used 2826's

If I am using the Opto, will I need anything else to make sure it runs properly?

Also, 77 amp? According to Model Motors, the 2826/8 has a max current of 55A/60s

Also, why the Opto rather than the other kind? Is the BEC useless given the setup that I will be running(2 motors, 2 ESCs), and therefore by choosing the Opto I am saving weight, or is there another reason?

Thanks.

ok so those were numbers completly off of my head hahaha i was a little wrong
Axi for 4 lbs
Thats for a 4 pound shell
I would actually recomend you use the 2826/12 if you have the room
You could use a 40 amp controler with i think but id recomend a little higher rating

Cody Harris wrote:

ok so those were numbers completly off of my head hahaha i was a little wrong
Axi for 4 lbs
Thats for a 4 pound shell
I would actually recomend you use the 2826/12 if you have the room
You could use a 40 amp controler with i think but id recomend a little higher rating

I am unfamiliar with Brushless motors, so what does the /?? mean exactly?

I see it is lower Kv, but does it also imply a higher torque?

Also, here is my modified plan for the shell.
Shell Option 1:
Diameter of the Shell - 16"
Height - 2.25"
Angle - 30 Degrees
Diameter of the Wheel Path Along Inside of Shell - 8"
Shell Thickness - 3/16"
Weight- 6.8094 lbs

Shell Option 2:
Diameter of the Shell - 14"
Height - 2.5"
Angle - 45 Degrees
Diameter of the Wheel Path Along Inside of Shell - 9"
Shell Thickness - 3/16"
Weight - 6.086 lbs

I think the 30 degree option is better for a couple reasons... Defensively, a 30 degree angle on the shell would be better. I also think that making it shorter is a good idea. The weight is also better. I can always take some weight out if I need to.

Input?

I will get to work on CAD sketches and Solidworks models soon to give a better idea of what I have in mind.

Thanks

the /# refers to the can length, the longer the can the more torque
I think i like option one better actually
As for the whole opto BEC thing im really not the one to ask thats why i sorta avoided it lol

you need a BEC somewhere. It's what powers the RC chip. If you're gonna use the sabertooth dual drive one again, that has a BEC, so you don't need one in the weapon escs. you can opt for no built-in bec in anything and add a separate one (like we did with copperhead) but that's just extra weight...

Dan Curhan wrote:

you need a BEC somewhere. It's what powers the RC chip. If you're gonna use the sabertooth dual drive one again, that has a BEC, so you don't need one in the weapon escs. you can opt for no built-in bec in anything and add a separate one (like we did with copperhead) but that's just extra weight...

Ok.

Anyone have any suggestions for what I should use for drive?

It is such a cramped bot that my options are limited.

the banebot ESC are really light and have them built in also

Cody Harris wrote:

the /# refers to the can length, the longer the can the more torque
I think i like option one better actually
As for the whole opto BEC thing im really not the one to ask thats why i sorta avoided it lol

I did a little bit of looking on my own.

ModelMotors.cz wrote:

Electric motors manufactured by Modelmotors are marked with name and numbers with slash. Name means type of motor (eg.: AXI - brushless 14-pole outrunner, MiniAC - brushless two-pole inrunner). First two numbers mean diameter of stator and next two numbers lenght of stator in mm. Simplified the bigger diameter and lenght the bigger power of motor. The number behind the slash is winding number. The lower winding number the higher RPM and current capacity.

So, what you said is actually not correct?
It implies that the winding number has nothing to do with the power of the motor, only the Kv and current capacity.

The less windings the more amps it can hold and the more speed. But less torque. And the opposite for more windings.

BUT

Since in a brushless motor the torque vs rpm per volt is a constant it does not matter what motor winding you get. You can get a very high winding motor and get close to a 1:1 ratio. Or get a low winding and use a big gear ratio to convert the speed into a usable torque. A motor that puts out 1000rpm/volt at a 1:1 will move your weapon with the same amount of power as a 3000rpm/volt motor with a 3:1 gear reduction. The latter is better as you are letting the gear ratio do the work of getting you the start up and constant torque.

Other factors go into this, such as battery voltage.

Josh Raichel wrote:

The less windings the more amps it can hold and the more speed. But less torque. And the opposite for more windings.

BUT

Since in a brushless motor the torque vs rpm per volt is a constant it does not matter what motor winding you get. You can get a very high winding motor and get close to a 1:1 ratio. Or get a low winding and use a big gear ratio to convert the speed into a usable torque. A motor that puts out 1000rpm/volt at a 1:1 will move your weapon with the same amount of power as a 3000rpm/volt motor with a 3:1 gear reduction. The latter is better as you are letting the gear ratio do the work of getting you the start up and constant torque.

Other factors go into this, such as battery voltage.

Thank you.

We totally had that conversation at Century III haha

Hahaha, i wondered why i got Deja vu when i posted that...

Alan Dreher wrote:

Cody Harris wrote:

You shouldnt have any problem at all using the 2826, thats what matt and senai eash use and i think matt said on the RFL forum his shell weighed over 7 pounds.
As for and ESC i would recomend the jeti opto if your going to be using A123 or lipo batterys, i think we used a 77 amp when we used 2826's

If I am using the Opto, will I need anything else to make sure it runs properly?

Also, 77 amp? According to Model Motors, the 2826/8 has a max current of 55A/60s

Also, why the Opto rather than the other kind? Is the BEC useless given the setup that I will be running(2 motors, 2 ESCs), and therefore by choosing the Opto I am saving weight, or is there another reason?

Thanks.

As for this. We had a Castle Creations 80amp (125amp max) ESC (and our mamba) we used with our Scorpion 1100kv (100amp) at nationals. During testing at school we found out that we peaked when hammering on the throttle at 170amps. So a 70amp with a 2826 is quite perfect. The motor will pull what it needs to get up to the power level the controller (you) is wanting. Its the motor/weapon which dictates what amperages get drawn. Most ESC's have a continious, and max amp rating. Such as 50amps continuious, and 80amp for 30secs. That doesn't mean you can't go above the 80amp. You are severely risking frying something, but you can run higher than that for a second or two.

Now its not good to take a 50amp motor up to 100amp either. Its fine for a few seconds. Which is how long our 170amp peak was running. Only a second or two while the motor got the beater up to speed.

There is a model of the shell that I had in mind. Took me 3 hours to make that in AutoCAD 2010(I got the trial version).

I probably won't really invest much more time beyond that because I will need to redo it in Solidworks anyway, but I had time...

ShamWOW! you....


That looks like my FBS shell i was designing....


You can describe it by taking Ziggo and smashing him down.

Yeah. 2.25" tall, 3/16" Ti Shell, 16" Diameter plus teeth, 30 degree angled sides. Would be pretty sick. But really expensive.

I like it

Beats our wok or frying pan idea...but like you say....not cheap....

rjw wrote:

I like it

Beats our wok or frying pan idea...but like you say....not cheap....

I have fundraising ideas.
We will see how it goes. Hopefully I can make this because it should be a very good 15 lb FBS.

Alan Dreher wrote:

rjw wrote:

I like it

Beats our wok or frying pan idea...but like you say....not cheap....

I have fundraising ideas.
We will see how it goes. Hopefully I can make this because it should be a very good 15 lb FBS.

Do it....it would be a nice bot

God damnit! Solidworks Student Edition doesn't work in Vista 64-Bit.
Which means I will either need to dual boot or not use Solidworks....

fluffing bullshit.

im still trying to decide wether i want to install it on my laptop or not :/
pain in the booty

Cody Harris wrote:

im still trying to decide wether i want to install it on my laptop or not :/
pain in the booty

I am actually considering purchasing a student license of AutoCAD 2010. I have been using the trial version and like it.
And since Solidworks is useless to me, I may as well.

Alan Dreher wrote:

Cody Harris wrote:

im still trying to decide wether i want to install it on my laptop or not :/
pain in the booty

I am actually considering purchasing a student license of AutoCAD 2010. I have been using the trial version and like it.
And since Solidworks is useless to me, I may as well.

As far as I know, you don't have to purchase AutoCAD to use it (if you're a student). All you need is a .edu email address to register with and they'll let you download a lot of their stuff.

Jeff L wrote:

Alan Dreher wrote:

Cody Harris wrote:

im still trying to decide wether i want to install it on my laptop or not :/
pain in the booty

I am actually considering purchasing a student license of AutoCAD 2010. I have been using the trial version and like it.
And since Solidworks is useless to me, I may as well.

As far as I know, you don't have to purchase AutoCAD to use it (if you're a student). All you need is a .edu email address to register with and they'll let you download a lot of their stuff.

Ok. I will look into that.