Chassis - Team 772 2011 off-season (update)

[akoscielski3]

I finished updating the chassis.

Old thread is : http://www.chiefdelphi.com/forums/sh...ad.php?t=97193d

Gen2 Andymark transmissions
6WD (IFI 6" diameter 1.5" wide)
1/8" sheet metal
0.75" flanges for structural support
Direct drive to middle wheel

Changes:
Sheet metal to 1/8" from 0/09"
Put supports across transmissions
Moved Back/Front plates to outside
Put Belt pulleys onto wheels
inserted Hub onto middle wheel for direct drive
Made a few more flanges for structural support (note: could not put too many on bottom because the belts would rub against them)

Frame weighs 9.27 pounds without motors or transmission.
Chassis total weight is 27.35 pounds

Any more questions or Tips for improvement are appreciated.

[Chris is me]

I don't understand the point of the material below each wheel.

[Colin P]

Originally Posted by Chris is me

I don't understand the point of the material below each wheel.

Style points

[akoscielski3]

Originally Posted by Chris is me

I don't understand the point of the material below each wheel.

Bumper support? Your not the first person to ask me this, but yes it mainly is just for looks. They dont add alot of weight, but i may remove them.

Edit: I just remembered the real reason. They are supporting the transmissions on the inside

[Madison]

Originally Posted by akoscielski3

Bumper support? Your not the first person to ask me this, but yes it mainly is just for looks. They dont add alot of weight, but i may remove them.

Edit: I just remembered the real reason. They are supporting the transmissions on the inside

The transmissions are too low to the ground to allow you easily and legally mount bumpers to the side plates. I'd still recommend raising everything up to reduce your ground clearance.

Additionally, by removing the trapezoids from the side plates, you can add another flange along the length of their lower edge and make everything stiffer. Right now, the trapezoids do nothing but hurt you.

[akoscielski3]

Originally Posted by Madison

The transmissions are too low to the ground to allow you easily and legally mount bumpers to the side plates. I'd still recommend raising everything up to reduce your ground clearance.

Additionally, by removing the trapezoids from the side plates, you can add another flange along the length of their lower edge and make everything stiffer. Right now, the trapezoids do nothing but hurt you.

The picture shows how the transmission is mounted to the side plate. If i remove the trapezoids, the bottom two supports will not be held on by anything. However, by moving the transmissions further up and removing the trapezoids, the two Top supports now would have nothing to hold onto, unless i change the sheet metal design (also changing wheel height). I could change how close the trapezoids extend to the floor (shorten them by 0.5"), make some flanges on the bottoms of the trapezoids and then the floor clearance would be about 1" (currently .5"). Would this be a better alternative?

[Madison]

Originally Posted by akoscielski3

The picture shows how the transmission is mounted to the side plate. If i remove the trapezoids, the bottom two supports will not be held on by anything. However, by moving the transmissions further up and removing the trapezoids, the two Top supports now would have nothing to hold onto, unless i change the sheet metal design (also changing wheel height). I could change how close the trapezoids extend to the floor (shorten them by 0.5"), make some flanges on the bottoms of the trapezoids and then the floor clearance would be about 1" (currently .5"). Would this be a better alternative?

You want to change the sheet metal design -- by moving the gearbox up and changing the wheel, you'll lower the entire frame neared to the ground. Since a typically legal bumper height is between 1-7" or so from the ground, that puts the frame in the sweet spot.

Flanges on the bottom of the trapezoid won't really do anything useful to make the frame stiffer. A flange that runs, uninterrupted, along the entire bottom length -- just like you have on top -- is the most rigid solution.

[akoscielski3]

Originally Posted by Madison

You want to change the sheet metal design -- by moving the gearbox up and changing the wheel, you'll lower the entire frame neared to the ground. Since a typically legal bumper height is between 1-7" or so from the ground, that puts the frame in the sweet spot.

Flanges on the bottom of the trapezoid won't really do anything useful to make the frame stiffer. A flange that runs, uninterrupted, along the entire bottom length -- just like you have on top -- is the most rigid solution.

I'll have the design changes up by tomorrow hopefully.

How much ground clearance should I make it? Im thnking 1 inch so the bumbers are even with bottom or robot. Should it be loweror higher?

[Madison]

Originally Posted by akoscielski3

I'll have the design changes up by tomorrow hopefully.

How much ground clearance should I make it? Im thnking 1 inch so the bumbers are even with bottom or robot. Should it be loweror higher?

1" is probably fine. The bumper rules will usually reflect the sort of field the game is played on -- so if the field is largely flat or if it has only gentle inclines, the typical 1"-7" bumper zone will work fine. If robots are expected to navigate steeper ramps, additional ground clearance is required and the bumper zone will reflect that.

[akoscielski3]

I finished faster than i thought. The new chassis is actually heavier than the old one. The new weight is about 0.5lbs more.

[Akash Rastogi]

Originally Posted by akoscielski3

I finished faster than i thought. The new chassis is actually heavier than the old one. The new weight is about 0.5lbs more.

Looking good! Now you'll need to add some material to that center wheel's mounting hole and add a bearing so it can be direct driven.

[akoscielski3]

Looking good! Now you'll need to add some material to that center wheel's mounting hole and add a bearing so it can be direct driven.

Here is how i did the direct drive to the middle wheel.

Basically, the output shaft is connected to the hub (keyway) which is inside the wheel and bolted on. I put a support axle on the other side which is inside the bearing on the wheel.

Will it work? Or is this a bad idea?

[Akash Rastogi]

No, this is probably a bad idea. You want support through all the material of the wheel to the end of the gearbox output shaft on a bearing. It is definitely much easier to use a wheel or attach a hub that allows the output to go through the wheel and rest of a bearing.

[akoscielski3]

Originally Posted by Akash Rastogi

No, this is probably a bad idea. You want support through all the material of the wheel to the end of the gearbox output shaft on a bearing. It is definitely much easier to use a wheel or attach a hub that allows the output to go through the wheel and rest of a bearing.

I cant find a bigger shaft than this one. I already have the biggest from andymark. How can i find a bigger one? I can try to make it smaller inbetween the wheel and frame too, but i dont think it will be long enough.

EDIT: It will fit but it will be extremely close. About 0.03" clearance

[Akash Rastogi]

Originally Posted by akoscielski3

I cant find a bigger shaft than this one. I already have the biggest from andymark. How can i find a bigger one? I can try to make it smaller inbetween the wheel and frame too, but i dont think it will be long enough.

Someone with more knowledge can probably let you know if its a good idea or not, I'm far from an expert. I'm just basing that off what I know about driveshaft support in direct drive systems.

If anything, just machine your own output shaft. Its a pretty simple lathe op.