View Full Version : pic: New gearbox CAD
CraigHickman
11-05-2008, 19:08
[cdm-description=photo]31504[/cdm-description]
sdcantrell56
11-05-2008, 19:10
That is quite beautiful. However, I have one question...how are you mounting the cims to the plate. It doesn't look like you have any corresponding holes for it.
CraigHickman
11-05-2008, 19:13
That is quite beautiful. However, I have one question...how are you mounting the cims to the plate. It doesn't look like you have any corresponding holes for it.
CIM's have 4 holes, two filled with bolts that hold the housing together. That's what you're seeing. The other two are used to hold the gearbox together and to the frame of the bot.
sdcantrell56
11-05-2008, 19:18
I still don't understand though. Are you running extra long bolts through the transmission and into the CIM? If so aren't they really small bolts?
Pretty sweet. I love elaborate cutouts. (IN CAD)
sdcantrell56
11-05-2008, 19:20
Pretty sweet. I love elaborate cutouts. (IN CAD)
Well if you get it cut on a waterjet or laser its not too bad in real life either:D
CraigHickman
11-05-2008, 19:21
I still don't understand though. Are you running extra long bolts through the transmission and into the CIM? If so aren't they really small bolts?
They're #10-32 bolts. Four of them will be more than strong enough to support the gearbox. If my stress tests indicate otherwise, I may add another set of standoffs. We shall see.
sdcantrell56
11-05-2008, 19:29
So the holes on a cim are threaded for 10-32? That certainly changes things for the better.
CraigHickman
11-05-2008, 19:32
So the holes on a cim are threaded for 10-32? That certainly changes things for the better.
Yep. I remember one year we accidentally used #10-24 on our gearboxes... And I kept wondering why it stripped out all the time.
sdcantrell56
11-05-2008, 19:38
HAHA thats never good. Maybe I'll have to integrate that into one of my transmissions.
Kyle Love
11-05-2008, 20:12
Whats the estimated output speed of the output shaft?
CraigHickman
11-05-2008, 20:40
Whats the estimated output speed of the output shaft?
Under load, it's calculated to be around 550rpm. When put to a 4 inch wheel, top speed is calculated at 9.67. I'm assuming 2 inch wide roughtop wheels for this system, but this gearbox could be mated to quite a few different systems.
By the way, if anyone wants the CAD for this, feel free to PM me. It wasn't too difficult to make, so I'd have no problems handing the CAD out.
sanddrag
11-05-2008, 20:47
I'd bet you could get another pound out of it in those gears if you wanted to, but overall, nice work.
=Martin=Taylor=
11-05-2008, 21:46
What is the advantage over the toughbox?
I like the CIM mounts. That's a very compact way to do it.
AdamHeard
11-05-2008, 21:54
What is the advantage over the toughbox?
I like the CIM mounts. That's a very compact way to do it.
I guess It would be the weight savings.
I'm not really a fan of the same 4 bolts holding the gearbox together, the motors on and the gearbox to whatever structure it is mounted to. No matter what, that is going to make assembly and mounting a much bigger pain that it needs to be. I'll agree it cuts down on parts and weight, but I don't think it's worth it.
CraigHickman
11-05-2008, 23:08
I'd bet you could get another pound out of it in those gears if you wanted to, but overall, nice work.
No, actually. The gears are heavily "dished" out on the other side, in order to keep those components to a single lathe process. There's practically no weight I can save by removing materials, only adding material.
What is the advantage over the toughbox?
I like the CIM mounts. That's a very compact way to do it.
The advantage it has over the toughbox is custom ratio, massively lighter, more stylish, more precise, and better bragging rights.
I guess It would be the weight savings.
I'm not really a fan of the same 4 bolts holding the gearbox together, the motors on and the gearbox to whatever structure it is mounted to. No matter what, that is going to make assembly and mounting a much bigger pain that it needs to be. I'll agree it cuts down on parts and weight, but I don't think it's worth it.
It would be a bit of a pain to assemble. However, depending on what kind of drive system that it would mate to, two of the mounting bolts may be countersunk. That would aid a bit in assembly.
M. Mellott
12-05-2008, 02:11
A straight-forward single-speed gearbox--simple in its mechanical design, but the weight savings and sideplate design make it very elegant...something defintely to brag about if this is on your robot!
And yes, "elegant" can be used to describe a gearbox...ask the Germans!!
Triple B
12-05-2008, 06:56
Craig,
I like it.
mike d
that is going to make assembly and mounting a much bigger pain that it needs to be. I'll agree it cuts down on parts and weight, but I don't think it's worth it.
It does look like much more of a hassle to mount, but thinking of the end product with those gearboxes mounted nicely would make it worth it. Pain for Beauty. :P
two of the mounting bolts may be countersunk. That would aid a bit in assembly.
Countersinking would aid in assembly but it still would be more complicated to assemble than needed. Very interesting design though, kudos.
Kyle Love
12-05-2008, 11:44
What is the advantage over the toughbox?
I like the CIM mounts. That's a very compact way to do it.
The weight savings and more custom ratios.
A big difference is one is made for mass production and one is made to build a few of. The cost to mass produce something like this would be quite a bit greater then the price of the Toughbox (e.g. more machining).
Joe Ross
12-05-2008, 12:09
What did you use for the weight of the motors (ie what is the real weight of the gearbox).
Woody1458
12-05-2008, 14:24
while you are making your own gearbox you could take a hint from 968/254 and add a FP motor :).
AdamHeard
12-05-2008, 14:50
while you are making your own gearbox you could take a hint from 968/254 and add a FP motor :).
And then take another hint from 968/254 and take them out after the first regional ;).
They didn't even notice they were gone (I misheard something a while back, they noticed [like Cory says below]), and with the Big CIMs out of the kop, the FPs are better suited for a mechanism than added power in the drive (for most games)
And then take another hint from 968/254 and take them out after the first regional ;).
They didn't even notice they were gone, and with the Big CIMs out of the kop, the FPs are better suited for a mechanism than added power in the drive (for most games)
I wouldn't say that's entirely accurate--we were definitely noticeably less speedy. it took a bit longer to accelerate to top speed.
The benefit we got out of putting the FP's elsewhere more than made up for the slightly slower acceleration.
=Martin=Taylor=
12-05-2008, 18:16
What did you use for the weight of the motors (ie what is the real weight of the gearbox).
How much do the CIMs weigh anyways? I've always wanted to know that :o
According to the AM website the toughboxes weigh 2.5 lbs. without motors. The only reason they weigh more than the Craig's is b/c they don't have any lightening patters on the gears (which as Kyle pointed out would make them more expensive).
How much do the CIMs weigh anyways? I've always wanted to know that :o
2.75 lbs
=Martin=Taylor=
12-05-2008, 18:25
2.75 lbs
Really?
So the gearbox weighs 1.6 oz.!!!?? Screw the toughboxes :D I know what I'm using next year :D
Really?
So the gearbox weighs 1.6 oz.!!!?? Screw the toughboxes :D I know what I'm using next year :D
Just weighed one a little while ago to check and see.
David Guzman
12-05-2008, 19:18
Yeap.
I always set up my CIMs to be 2.8 lbs (each) in Inventor. He must be using the default material on inventor.
Looks good, I would also like to know how much it weights with out the motors.
israel354
12-05-2008, 19:54
dude thats freaking sweet!
CraigHickman
12-05-2008, 20:49
...Woah, I guess I've been using an incorrect model for my CIM's. Thanks for pointing that out! I'm at work right now, but I'll update the model and fill you all in on how much it ACTUALLY weighs when I get home.
EDIT: After a materials update, the gearbox comes out to 7 pounds even with motors.
A straight-forward single-speed gearbox--simple in its mechanical design, but the weight savings and sideplate design make it very elegant...something defintely to brag about if this is on your robot
I second that. Very elegant, very nice design. If you use this gearbox... you should make a couple extra side plates and chrome plate them for explanation-to-judges purposes at regionals. We had a really cool frame system on our 2006 robot and did something similar... we had extra aluminum frame components that we polished to a high gloss shine for explanation purposes.
Everybody likes bling... even FIRST judges. :D
Great job!
-q
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