How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

I still can't figure out how those super fast robots are doing it. The rules give you 3 alum. gears but none of them look big enough to have the 120t gear in use. There is some talk of bypassing 2 gears in the motor gearbox but that sure looks questionably legal.

Also, what are they using for traction material on the output shafts (like 118) ? (Electrical) Heat Shrink ? Surely there is no "hard" surgical tubing ?

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

Removing/modifying the attached gearbox is perfectly legal. When removed, the motors spin far too fast to allow "normal" wheels. But with small diameter shafts used to climb the post, torque output is dramatically increased. Most of these smaller shafts seem covered in heat-shrink tubing, or surgical tubing.

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

Try this: Remove the gearbox entirely. Drill a tetrix shaft with a #40 drill (0.098) in exactly the center and press it on to the motor shaft. Cover the tetrix shaft with latex tubing (hint: rubbing alcohol makes a fine lubricant to slide it on). Support the far end of the shaft (tetrix bronze bushing).

Two of these motor/shafts, a battery, 2 switches, and a clip or magnet to hold it on and up you go in (how many?) seconds.

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

If you don't have any rubbing alcohol on hand, warm water works just as well.

Where the experimentation and design comes in is where to put the motors:

I've seen ones with two motors on one shaft, two motors clamping onto the pole, and one with one motor on top and bottom.

I'm not going to tell you which was fastest :P

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

That is more or less what we did. It is super light and very fast.

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

Tetrix shafts are too small, go bigger.

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

whatever you say chris :p , depends on the surgical tubing size and the minibot weight

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

less is more when it comes to output diameter and force.

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

Now this is where it confuses me, we purposely left our modified motors at our shop and used our unmodified minibot (got us really far) but apparently we had to sign a paper that stated we would not modify the gearbox. What was with that? I asked th inspectors, they said it was not allowed and said gracious professionalism should be kept. The inspectors never checked the minbots for modified gearboxes.

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

This is blatantly incorrect. You are allowed to modify the gearboxes but not the motors. Anyone who said otherwise just doesn't know the rules.

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

Thank God. I don't know, our mentor, team captain and anyone with "authority" blantantly said "no David, no". Now for LA we are just making our MB super fast. Honestly though, we had a very very reliable deployment and minibot. (11:15 made to attempted ratio) It was slow, but that got us to Semi Finals and apparently we ended the competition at rank #4. I am impressed.

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

A slow minibot that makes it every match made our #6 spot on our pick list (maybe a little lower, I don't have it). It's all about consistency.

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

Is very, very reliable 11:15? Less than half?

We haven't gone to an actual competition yet, but we've never failed in deploying - obviously, it will be different with all of the other robots flying everywhere, but still. What was yours like during testing?

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

Honestly, it was fail proof, but not human proof. It is programmed that the robot backs up into the pole as it deploys so it is guarantee that it deploys. The 4 were human errors such as forgetting to put the deadman switch on or driving away from the pole as it deployed or going to the pole too late(we just get pushed around) But it makes it every single time as long as we set up around 25 sec. But we did not choose to use the arm (we zip tied it to the robot), so we went defensive (because of our design flaw, that was our down fall) then deploy every match.

Edit: that was not the gear ratio, I am saying reliability > speed. We had a 4 second minibot


Edit: that minibot alone got us to the #3 spot (we dropped down to #4 when we DQed for getting pushed into the scoring zone by the other robots several times at the semis)

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

You can always modify any gearbox unless the rules (or Q&A) specifically states you cannot modify it because it is integral. Currently, the only legal modification you can make to the Denso window motor gearbox/motor is removing the pins (all other mods illegal, however you can do this). All other gear boxes are fair game for mods.

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

Speed does play a huge factor once eliminations hit. We were on the number 5 alliance going against the number 1 alliance. We had one minibot, they had 2. The only way we could win was to get our minibot up first and let them score 2 and 3. We also had to outscore them on tubes. We beat them. While reliability is what gets you picked. Fast minibots get you a win.

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

No, you cannot do that with a desno motor,
http://forums.usfirst.org/showthread.php?t=17054

however, the motor/gearbox combo photo is still legal due to this.

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

Thanks for the great insights.

I thought surgical tubing was rubber but maybe its latex ? Where do you find latex tubing with such a small inside hole diameter ?

What's the easiest way to provide enough pressure on the drive axles to get good contact with the pole. Is that where the magnets are used (presumidly close to but not contacting the pole) ? We used rubber band pressure on our traditional MB but it would be nice to simplify things.

Or is the magnet used on the perpendicular side of the minibot to hold it to the pole (again very close but not touching, perhaps held off by a roller beside it ?

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

The lesson to be learned here is that if you're doing anything that relies on interpretation of the rules or a Q&A clarification, make sure you do your homework, and bring a printout of the relevant rules / Q&A to show the inspector. In fact, make yourself familiar with all the rules. Be prepared to present the facts to the inspector; but don't try to argue with them - that will generally work against you. Remember gracious professionalism.

I recently had such a conversation with an inspector regarding the playing configuration size. He claimed that it included bumpers, which would not have worked for us. Fortunately, I was able to point out the rule section that clearly stated bumpers are not included in playing configuration size, and all was well.

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

Hello sir, we will see you at Long Beach. Good luck to you guys and be prepared. We will be prepared to dominate the West Coast.

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

And I'm pretty sure that the GDC knows the rules

http://forums.usfirst.org/showthread.php?t=16779

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

Can someone post a picture of a modified gearbox? Thanks!

Re: How are <1.5 sec Minibots doing it ? Gearbox mods allowed ?
 

Here is a pic of un-modified transmission.


The way you modify it to become a 10.4 to 1 can be achieved in a couple of ways. All of them involve removing the 30:15 and 25:10 gears and mating the 26:10 to the 40t output gear.

The way we did it was to machine a spacer that fits around the output shaft and raises it to the proper position to engage the 10t on the 26:10 gear. Then we machined the end of the output shaft you can see in the pic the same amount so the end plate fits back on with the proper end play.

A team we gave our spare minibot pieces to in Seattle knurled the output shaft so the 40t gear could be pressed up the corresponding amount. In the picture you can barely see the knurling on the output shaft where the 40t gear is pressed on.

I have also read on here of 2 other ways. #1 removing the gear and staking it around it's ID to reduce that diameter, then pressing it back on with thread locker as a little extra insurance. #2 shorten the case, and swap the existing spacers around, use the one that is under the 25:10 under the 26:10 and the one that came off the top of the 26:10 on top. This method also requires shortening the output shaft so the case fit's back together. This method is the most complex.

So there are a number of ways to skin this cat depending on the tooling and skills your team has.