2583 Off-Season Drivetrain Help

[ferrari77]

I have included a link for the .step file of the chassis now

I included a lot of the changes you guys suggested

I still have to include the rest of the electronics and figure out a tensioning design but that will come later

The red things on the wheels are the colson live axle hubs
http://wcproducts.net/wcp-00053/

The blue things on the aluminum channel (seen from the bottom of the robot) are AndyMark hex bearings with flanges
http://www.andymark.com/product-p/am-0279.htm

The hole in the aluminum channel is slightly smaller than the OD of the bearing so they will be pressed in and there is a small flange on the bearing which will keep it from going too far.

Also the axle is now hex and the pulley has a hex bore so they are connected

Do you guys have any more comments or suggestions?
Your help has been very useful so far, im learning a lot

Download Link:
http://www.2shared.com/file/kdrucknG/chassis1.html

[Garret]

I think this is much better.

However a few things I notice:

• Is there a reason you have the large plate on top of the frame rather than below it? If there isn't a reason, you could probably move it below and protect the electronics a little easier.

• I would recommend that you try to support the gear box output shaft on the end.

• I would also only make the shafts 1/2" hex at the wheel. By turning it down to regular 1/2" you save yourself the need to purchase a broach. Additionally you can save money by purchasing regular 1/2" bearings ($7 vs $9.50) rather than hex bearings.

Again, this design is much better now, good job.

[ferrari77]

Originally Posted by Garret

I think this is much better.

However a few things I notice:

• Is there a reason you have the large plate on top of the frame rather than below it? If there isn't a reason, you could probably move it below and protect the electronics a little easier.

• I would recommend that you try to support the gear box output shaft on the end.

• I would also only make the shafts 1/2" hex at the wheel. By turning it down to regular 1/2" you save yourself the need to by a broach. Additionally you can save money by purchasing regular 1/2" bearings ($7 vs $9.50) rather than hex bearings.

Again, this design is much better now, good job.

Would it make it the structure stronger if I put the board below or is just for the sake of protection? I could definitely put it below if its better

I thought about doing this for the axles but we only have a lathe and I dont think we have any tools to turn a round axle to a hex axle
Mcmaster sells hex axles which are long enough but the hole axle is hex

Is there a way for us to make the part of the axle hex without buying anything?

[Garret]

You can buy 1/2" hex shaft and turn it down to just regular round 1/2" shaft with a lathe its a pretty standard operation. You would then just use either set screws or cotter pins for the sprockets.

Putting the plate on the bottom of the frame is what is normally done. In my opinion it looks cleaner, helps lower the Center of Gravity, and allows you to attach a superstructure easier.

[Mk.32]

Originally Posted by ferrari77

Would it make it the structure stronger if I put the board below or is just for the sake of protection? I could definitely put it below if its better

I thought about doing this for the axles but we only have a lathe and I dont think we have any tools to turn a round axle to a hex axle
Mcmaster sells hex axles which are long enough but the hole axle is hex

Is there a way for us to make the part of the axle hex without buying anything?

A. WCP is selling hex bearings for $7.5.
B. You can turn hex into round shaft with a standard lathe that has a 3 jaw check and just HSS tool. Also the hex pushing up against the bearing would help retain the shaft in place

[z_beeblebrox]

I'm not really a drivetrain expert, but maybe you could save some weight by cutting a lightening pattern into the electronics board.

[ferrari77]

Originally Posted by z_beeblebrox

I'm not really a drivetrain expert, but maybe you could save some weight by cutting a lightening pattern into the electronics board.

I've been waiting to do this because our team does not know if we will have access to a laser cutter
If we do I can do a cool looking lightening pattern with diamonds and triangles
If not I will do what we have done in the past with just rows or circles

[MichaelBick]

I also recommend a garolite bellypan if you aren't able to get a bellypan lasered.

[Madison]

If you've never designed a drive before, use dead axles everywhere -- even if your team has done it before, tackling a drive with live axles the first time out is a lot to handle. It seems like you don't have a lot of machining resources and that you're relying on off-the-shelf parts; that's a good decision. Using live axles with cantilevered wheels offer you ZERO benefit and will make your life miserable.

Why are you using timing belt instead of chain? The timing belt pulleys will require work to adapt them for use in all cases -- a set screw isn't good enough to drive a live axle in FRC applications and they're not easy to bolt onto a wheel for a dead axle. In some models, you show a hex-bored timing pulley; can you broach the hex bore? You won't find a timing pulley with a hex bore available commercially. There are lots of existing options for chain sprockets that fill those roles, however.

If you decide to use timing belt; do you have a belt length in mind? Make sure a commercially available belt can fit the distance between those pulleys or you'll spend a small fortune for custom lengths.

If you insist on using live axles (you shouldn't; it's a terrible idea at this stage), you have to give a lot more thought to retaining your power transmission components axially. What stops things from sliding along the axle? What stops the axle from sliding out of the bearings? What stops the bearings from popping out of the channel? How much did you undersize the holes in the aluminum tube? How are you going to accurately make holes of that size? If you can't key a shaft, you probably can't make press-fit bearing holes.

Check out your gear ratios. The Toughbox Mini's standard 12.75:1 reduction with what appear to be 4" wheels is probably too much. Consider getting a different gearset for a lower ratio.

Start simple. After you succeed, try something more challenging. It is unwise to try to mimic 254 et al on your first go around.

[ferrari77]

http://www.youtube.com/watch?v=njHa7...ature=youtu.be

First video shot at a late night meeting of this drivetrain, finally built and running

[karomata]

I would use chain instead of pulley belts, they don't slip as much and are more reliable.

[Gregor]

Originally Posted by karomata

I would use chain instead of pulley belts, they don't slip as much and are more reliable.

Really? How do you know? What do you mean by "don't slip as much," and why are they "more reliable?"

There is no defined better in terms of chains or belts.