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-   -   pic: 3 Hour Chassis + 2 Hours (http://www.chiefdelphi.com/forums/showthread.php?t=85759)

sgreco 11-05-2010 18:57
Re: pic: 3 Hour Chassis + 2 Hours
 
Quote:
Originally Posted by 548swimmer (Post 961684)
The only potential issue with that is 80/20 in comparison to hollow tube, it's very heavy. For an off-season drive train, that would be an excellent idea, though I would recommend against it for a competition bot.
Yes this is true...to be honest I'm not a fan of 80/20 for its weight reasons(even though my team used it with out problems this year. We didn't make our whole frame out of it though, we only used it for crosses)...

80/20 is unneccessary if your team CADs well, because you can plan all of your cuts ahead of time. 80/20 can be nice if your team likes to make it up as you go and constantly be taking off and adding parts. (not that you can't do it with other materials, just 80/20 makes it easy).

I would still recommend it for a prototype though.

Ty Tremblay 11-05-2010 19:05
Re: pic: 3 Hour Chassis + 2 Hours
 
Quote:
Originally Posted by Jeff 801 (Post 961667)
From the looks of it the small sprocket on the toughbox looks to be about 16 tooth and the sprockets on the wheels look around 48 (Very ROUGH numbers) and assuming its a standard toughbox the overall reduction is 28.3:1 and those look to be 6" wheels so the top speed would be 3.05ft/s

Or on the back side of that wheel the sprocket is smaller than all the others and after looking at the AndyMark website the smallest sprocket (#25 I am assuming) is 32 tooth and the sprocket on the toughbox output shaft is still 16 that means the overall reduction is 25.5:1 and the top speed is 4.57ft/s

From what I know your average single speed robot is ~9ft/s which would cause me to thing there is some sort of difference in the toughbox or the extra chain reduction can be removed and supplemented with one of the many gearing options AndyMark has for sale.

After going back to the old thread I see that your wanting to get ~12ft/s which you can do by using the Toughbox with the optional 9.87:1 and direct drive which would give you ~11.82 ft/s
I've done no calculations regarding gear ratios, chain reductions, or overall speeds yet. I felt that there were more pressing structural concerns in my design that I needed to adress before conquering the gearing.

That 9.87:1 Toughbox seems interesting, but if we're going to buy more Toughboxes, we might as well just make our own (lighter) gearboxes. I just threw the Toughboxes in the CAD in the event that the team wanted to save money and use the Toughboxes we already have.

sgreco 11-05-2010 19:10
Re: pic: 3 Hour Chassis + 2 Hours
 
Quote:
Originally Posted by Ty Tremblay (Post 961690)
I've done no calculations regarding gear ratios, chain reductions, or overall speeds yet. I felt that there were more pressing structural concerns in my design that I needed to adress before conquering the gearing.

That 9.87:1 Toughbox seems interesting, but if we're going to buy more Toughboxes, we might as well just make our own (lighter) gearboxes. I just threw the Toughboxes in the CAD in the event that the team wanted to save money and use the Toughboxes we already have.
If you like the gearing in the Toughbox, there are lot of weighs to reduce weight. You can mill out some of the material in the side plates, get aluminum gears instead of steel, or just cut out material in the gear sand sprockets like this http://www.chiefdelphi.com/media/photos/30614

I'm all for custom gearboxes, but if you want to keep it simple, you have a lot of options.

Chris is me 11-05-2010 19:33
Re: pic: 3 Hour Chassis + 2 Hours
 
Quote:
Originally Posted by 548swimmer (Post 961684)
The only potential issue with that is 80/20 in comparison to hollow tube, it's very heavy. For an off-season drive train, that would be an excellent idea, though I would recommend against it for a competition bot.
Not really, 80/20 weighs almost exactly the same as 1/8" wall 1" square tubing.

EricH 11-05-2010 19:37
Re: pic: 3 Hour Chassis + 2 Hours
 
Quote:
Originally Posted by Chris is me (Post 961695)
Not really, 80/20 weighs almost exactly the same as 1/8" wall 1" square tubing.
And 1/16" wall 1" square tubing is called for.

For the hollow tube in general, you're right. But for the specific hollow tube called for, 80/20 will be heavier.

Comment on the cross-braces: I'm not quite sure I'd trust a 1/16" wall for that application in that pattern. Change the pattern, and you'll probably be fine--but run the analysis just to make sure.

sgreco 11-05-2010 19:40
Re: pic: 3 Hour Chassis + 2 Hours
 
Quote:
Originally Posted by Chris is me (Post 961695)
Not really, 80/20 weighs almost exactly the same as 1/8" wall 1" square tubing.
It's close, a foot of 1x1 80/20 weighs .53 pounds and a foot of 1x1 1/8 wall weighs about .512 pounds. This is assuming 6061. They're so close its negligible.

(These numbers are what SolidWorks is telling me).

You can pocket 1x1 tubing, but you can't pocket 80/20 so that could be included in the weight tradeoff.

Chris is me 11-05-2010 19:41
Re: pic: 3 Hour Chassis + 2 Hours
 
Quote:
Originally Posted by Jeff 801 (Post 961667)
After going back to the old thread I see that your wanting to get ~12ft/s which you can do by using the Toughbox with the optional 9.87:1 and direct drive which would give you ~11.82 ft/s
Running 12fps without shifting and using roughtop tread will lead to a lot of current issues as well as iffy acceleration.

Hawiian Cadder 11-05-2010 21:35
Re: pic: 3 Hour Chassis + 2 Hours
 
i would recommend the use of C channel instead of square pipe, it can be just as strong if oriented correctly, and it is lighter as well as easier to attached.


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