"Cheap" Robot parts

[Gary Dillard]

Gotta caution you though - I tried to use the part you have pictured in zone zeal as the pivot for our 2 arms (you'll see them in early pictures of Fluffy but not in the version that made it to nationals). We had flat run out of manufacturing resources and time to make the original bearing and support, so I did a quick redesign to use these off the shelf parts from McMaster Carr. They may take 300 pounds of load, but they have no stiffness or strength in off-axis torque. They actually performed better than I expected - the formed sheet metal managed to stay just close enough to keep the ball bearings from departing - but the lack of stiffness caused problems in the drive system (couldn't keep tension).

My favorite activity during week 1 is to go to home depot and stare at stuff for ideas, and to see what I could cluge together for a mechanism. Parts that already have integral hinges or bearings can save you a bunch of time and money. At worst you get a quick prototype; at best you get a functioning component.

[Raul]

An alternative to ball bearings: Just use bronze bushing.

Before assembly, be careful to make sure the mating interface to the bushing is very clean to avoid friction. And of course add some oil.

Raul

[jrgrim12]

The best way to keep things cheap is to keep them simple. Don't let your design get out of hand. If you catch yourself adding parts here and there just to try and make a design work then maybe it's not a good design. I guess what I'm saying is don't try and design a hand when a claw will work.

[Adam Y.]

An alternative to ball bearings: Just use bronze bushing.

Before assembly, be careful to make sure the mating interface to the bushing is very clean to avoid friction. And of course add some oil.

Actually bronze bushings should be all ready lubricatd. They cotain little pores of oil that come out when the shaft moves fast enough.

[Tytus Gerrish]

Originally Posted by Raul

An alternative to ball bearings: Just use bronze bushing.

Before assembly, be careful to make sure the mating interface to the bushing is very clean to avoid friction. And of course add some oil.

Raul

if you have a shaft runing fast enough the juberactioj is gonna disapper prety fast with that little setup

but i guess its good for slower-moving parts

[Adam Y.]

if you have a shaft runing fast enough the juberactioj is gonna disapper prety fast with that little setup

Errr I hope you mean lubercation. Anyway oil impregnated bushings do not have that problem since the oil is all ready in the bushing. (Note: I do not know if impregnated is the right word)

[Tytus Gerrish]

OMG! wheens spell check coming back and the orange?
Please everyone out there Dont give me anymore negative rep points for my spelling, i know im working on it

[Tristan Lall]

Originally Posted by Tytus Gerrish

if you have a shaft runing fast enough the juberactioj is gonna disapper prety fast with that little setup

Originally Posted by Adam Y.

Errr I hope you mean lubercation. Anyway oil impregnated bushings do not have that problem since the oil is all ready in the bushing. (Note: I do not know if impregnated is the right word)

Are either of you sure what you mean? (i.e. lubrication )

And yes, impregnated is the right word.

[Andy Baker]

Guys...

When an oil impregnated bearing (otherwise known as a bronze bushing) gets hot, then the oil starts to exit from the bearing. This hottness could be caused from an overloaded bearing (very high rpm and load) or something next to it getting very hot.

Andy B.

[generalbrando]

My advice on cheap parts is to remember that you don't have to order from MSC McMaster and 80/20. We were stuck in that track last year, wondering how we could lost weight and cost. For those 5 ft long wings you might have noticed we used some cheap conduit (sp? sorry, I don't have time to run Word). My advice is to take a trip to Lowes or something like that when you need ideas for parts. You can use so many different materials that they have there and they tend to be cheaper than ordering from these other companies.

P.S. If you get your stuff locally that also means that you can run out and get an extra one when you need it the day before shipping!

[Adam Y.]

Originally Posted by Andy Baker

Guys...

When an oil impregnated bearing (otherwise known as a bronze bushing) gets hot, then the oil starts to exit from the bearing. This hottness could be caused from an overloaded bearing (very high rpm and load) or something next to it getting very hot.

Andy B.

Is that good or bad? Should the lubrication stay inside it or outside it?

[Andy Baker]

Originally Posted by Adam Y.

Is that good or bad? Should the lubrication stay inside it or outside it?

Once an oil impregnated bearing gets too hot, the oil sorta "boils out" of the bearing, then the bearing dries up and it does not work as well. The hole gets a bit bigger and the bearing is shot. It is definitely not a good thing... you want the oil to stay inside the bearing material.

Andy B.

[Raul]

I guess I should have elaborated a little more on my suggestion to use a bronze bushing. You may get away with not using oil for some time when a bronze bushing is used for a steel (or maybe some other hard metal) shaft. But I know from experience that you must use additional oil if used for an aluminum shaft. And if you use an aluminum shaft with a bushing, you should try to stay away from using it for high RPM applications.

Raul

[Sachiel7]

Ok, here's a quick question guys. We took our pre-season vote to go ahead with my "standard" drive design (yay!)
But it was brought up that the idle shaft's bearings could be replaced with bronze bushings, at a cheaper cost.
I'll be honest here, I've never used bushings before. What's involved with them? From what I understand you need a housing block of sorts for them.
Anyway, I have 2 idle shafts. They dont spin, they provide support for the wheels and chassis. Would it be better to replace the bearings they are on with bushings?
Also, where can you find good, cheap bushings? I checked MSC and had trouble finding some.
I need 4 (one for each support point) and they need to be for 5/8 shaft (I think it's steel) and need an outside diameter no larger than 1 inch.
If someone could help me out, that'd be great. Currently, we have several 4-bolt flange bearings we're using, and they're around $26 each. So, having some of those trimmed off for bushings should help a bit, i'd suspect.
But I don't want to deal with this thing falling apart at competition. We want it to last.

[Matt Adams]

Originally Posted by Sachiel7

Ok, here's a quick question guys. We took our pre-season vote to go ahead with my "standard" drive design (yay!)

Originally Posted by Sachiel7

But it was brought up that the idle shaft's bearings could be replaced with bronze bushings, at a cheaper cost. I'll be honest here, I've never used bushings before. What's involved with them? From what I understand you need a housing block of sorts for them. Anyway, I have 2 idle shafts. They dont spin, they provide support for the wheels and chassis. Would it be better to replace the bearings they are on with bushings?

If they're not spinning at all... sure bushings... actually, you could probably just have them rest on whatever metal they're in between. However, I'd like to see a picture or a sketch (if possible) so see how these are "supporting" the wheels and chassis. Are they just spacers?

Originally Posted by Sachiel7

Also, where can you find good, cheap bushings? I checked MSC and had trouble finding some. I need 4 (one for each support point) and they need to be for 5/8 shaft (I think it's steel) and need an outside diameter no larger than 1 inch. If someone could help me out, that'd be great. Currently, we have several 4-bolt flange bearings we're using, and they're around $26 each. So, having some of those trimmed off for bushings should help a bit, i'd suspect. But I don't want to deal with this thing falling apart at competition. We want it to last.

Well, I think that your best bet for cheap bushings are McMaster-Carr or Endco. Here's a link for the exact bushings you're looking for.

Thrust Bushings:
http://www.mcmaster.com/asp/loadpage...995&catnum=109
Flanged Bushings:
http://www.mcmaster.com/asp/loadpage...996&catnum=109

Also, sometimes companies use bushing and bearing synonymously, so searching for bronze bearings can sometimes get you what you're looking for.

Let me know if you need anything else.


Matt