4488 Off-season Gearbox
 

So last year our drive train had some issues with a center chain in a WCD, so we decided this was finally going to be the year we actually made a direct drive gearbox in order to fix these problems. This is what we came up with. Its a direct drive single speed gearbox with toughbox spacing except for 12 tooth pinions instead of 14 tooth pinions. The only question I have is if the material surrounding the bearings is enough. Right now they are between .2 and .3 inches. Should I make them thicker, or is that good enough? Also do you think there is anything I can do to make it better.

Ok got the correct pictures.

Re: 4488 Off-season Gearbox
 

1. It's probably thick enough. I think the standard is .25".

2. This looks pretty similar to WestCoast Products' shifting gearbox. So similar, in fact, that I question the need for you guys to fabricate your own. I doubt you can do much better than their price of $250 per gearbox, and you'll save a lot of time. Of course, if the goal is to get experience in design and machining, by all means go ahead.

Re: 4488 Off-season Gearbox
 

I looked at the WCP gearboxes, but we dont have the money for the dual-speeds, and I really dislike the ratios on the Single speed. The ratios this can get are much better for our needs

Re: 4488 Off-season Gearbox
 

I'll echo what T^2 had to say, and suggest you take a serious look at the WCP SSes. I'm not sure when you last checked, but they've updated their product line since the season. You can get a reasonable ratio on basically any FRC diameter wheel out there, and I'm fairly sure that you can get a similar gearing to what you're getting with the Toughbox. They're really awesome products for the money, and we've been very satisfied with out DSes.

Re: 4488 Off-season Gearbox
 

For 6 inch wheels they jump from 7.9FPS to 16.5FPS. There is no in between with the WCP ones. That is tough, because in most games 7.9 is too slow, and 16.5 is too fast for a single speed. Plus at $150 a piece, we have bought all the gears, shafts and materials for about $100, which is much cheaper. If they could get a 10FPS option with 6 inch wheels, that would make them look better, but they would still be too expensive.

Re: 4488 Off-season Gearbox
 

It looks good, nice work. If you're not content with existing gearboxes then you got yourself a good solution.

As for the thickness, it should do, but you should always run simulations to make sure.

Re: 4488 Off-season Gearbox
 

You're forgetting to factor in time. By buying the gearboxes you save time, and that can be worth $50 extra per gearbox.

Re: 4488 Off-season Gearbox
 

$50/gearbox is well worth the cost if it saves us from designing, fixturing, machining and troubleshooting the gearbox plates, spacers and shafts.

-Brando

Re: 4488 Off-season Gearbox
 

Also keep in mind that 6" wheels are a bit big. For ground clearance they are ok but in most games you can go with smaller wheels.

Re: 4488 Off-season Gearbox
 

I know 6 inches are big, and we plan on using 4s, but I like contigencies. Also, can you fit an AM Kit wheel or a VexPro VersaWheel onto the 1.25 inch output shaft? Everytime I look those wheels are wider, and I don't even know how you would mount those to a 1.25 inch long output shaft.


Also its about ~$100 extra per gearbox, not $50.

Re: 4488 Off-season Gearbox
 

WCP sells theirs single speed for $150, are you saying you can make the above single speed for $50? I'd love to get your suppliers :rolleyes:

Not trying to pick on you, it's just I'm not buying the cost argument.

Making your own box for people to learn, so it's yours, so it's cool, etc... are all valid reasons, but I don't see this saving appreciable amounts of money (and it saves that money at appreciable amounts of time).

EDIT: On some more thought, $50 per gearbox isn't implausible. It's a little lower than what we spent, but not impossible.

Re: 4488 Off-season Gearbox
 

Someone somewhere may have told me prices will be going down sometime.

Just don't knock out WCP's gearbox. I'm holding some in my hand right now and it's a beautiful thing with perfect ratios. Like you mentioned it is for a WCD which is designed for 4" wheels. If you're making a WCD you should have no need for anything larger than 4" wheels.

Re: 4488 Off-season Gearbox
 

Contingencies are always a good thing, but remember 'jack of all trades, master of none'. You often are making sacrifices to be able to account for large varieties of wheels, etc. While this time of year is absolutely the best time of year to explore those options, when its time to start spending money and cutting metal on a build-season robot, the best bang for your buck may be a very focused design.

-Brando

Re: 4488 Off-season Gearbox
 

For shaft mounting the width of the wheels is not what matters, the length of the hub is what matters. A hub does not necessarily need to span the entire width of the wheel. A 1.5" wide wheel may operate perfectly fine with a 1" long hub, and still leave space for a .25" spacer between the hub and bearing on a 1.25" output shaft.

Re: 4488 Off-season Gearbox
 

Total cost not including the metal for the plates, is $101.8 all from Vex. Thats enough for 2 gearboxes. The only thing that doesnt include is the sprockets, which the WCP doesnt include either so its moot.

As for machining, at our school we have 9 lathes, 3 mills, a CNC, and students who know how to use all of them. During week 1, we have kids that are much more interested in machining then designing, so we can make these during down time, when we don't have a full robot designed yet.

I'm not writing them out, and if we run into trouble that will be option 1. But I think we could do it more efficiently, cheaper and more focused to our needs by doing it manually. Plus it will keep the students occupied week 1.

Also what 4 inch wheels actually fit the 1.25 inch output shaft? I'd love to know, so we could make ours even shorter if needed.