pic: Team 30 Dual-Motor Transmission

[CD47-Bot]

[cdm-description=photo]16757[/cdm-description]

[Rickertsen2]

<sarcasm>I don't think it's beefy enough. It looks rather fragile, almost as it it might spontaneously fall apart at any second.</sarcasm>
Really though, good job. Looks great!

The only problems as far as i can see are:
1.)a bit heavy

[Veselin Kolev]

Wowie.
Hey, one question.. where did you get the .7 mod gears to match with the drill? And.. how fast did you get them? Thanks

[Elgin Clock]

Let me guess, they each weigh approximately 7-8 lbs each? :D

[Ryan Curry]

We didn't use the .7mod gears, the gear on the drill is a 20 DP that we put on it. As for the weight im not sure how heavy it is, but it is sturdy to say the least. Not too expensive to make either, ~$100 per side.

-Rc

[sanddrag]

A few Questions:
What is the 20P gear on the drill, how did you put it on, how did you get the old one off, and where did the new one come from? Thanks.

EDIT: I see some potential problems, you have a shaft collar riding right up against the Oillight bushing, and it looks like you may have gears with the same problem. Also, I assume you are supporting the end of that output shaft, if you weren't planning on it, please do.

[Cory]

Sanddrag: you can get the new gear from pretty much anywhere. I ordered oen from Motion Industries yesterday. Im guessing they press fitted it onto the shaft of the drill motor. As to how they got it off, search. I remember Paul Copioli posting a neat little machined piece that you made, then screwed an M5 screw through, eventually popping the pinion off the shaft.

Cory

[Rob Colatutto]

What speed did you calculate that to drive your robot at with the 12.5 inch wheels your using? I looked and took some educated guessed and calculated it to be about 15.8ft/s. Did you run any numbers on that to obtain your current draw at that speed? How about how well the robot will turn with 4 pneumatic wheels? Also from the drawings it doesn't appear like the bosch is held into the gearbox with anything, is it connected at the bottom in an unseen way? I also share the concern about that output shaft, I would not recommend to have something that long as a cantilever shaft. It also looks like you are planning to have the gearbox slide into the chassis and be bolted in. I have had experiance with mounting gearboxes like that and I would suggest against it, espescially with a more than 2 wheel drive robot. Under the highest stress situations, the gearbox will be sliding around on you and the bolts will try to loosen.

[AlexR]

You can take the gear off the drill motor with a good old fashioned dremel. Just don't let shavings get in the motor. It's good fun, really.

[Ryan Curry]

I'm not sure what speed the wheels will be turning, becuase we can adjust what sizze sprockets we have the chains going to. If we want more speed we can lower the ratio. As for turning we were concerned that it might have the "jumping" problem but we ran it and had no issues, turned just fine. We never cantilever drive shafts, there is a pillowblock that the output shaft goes into already on the frames. I'm not sure how they bolted it on however becuase I'm at college ~100+ miles away.

The gear that is on the drill we ordered through motion industries, it is made by boston gear. It was press fit on. The drill motor is held in place by the giant shaft collar that was machined for it, it was run for about 20min at full speed with no slipping.

-Rc

[Rob Colatutto]

The calculation I did was with a 12:60 sprocket reduction and thats the biggest possible with ordering from mcmaster and such. What are those gear reductions in there? From observation it appears you might have the numbers wrong with your bosch motor, but knowing the actual teeth numbers would be nice.

[SarahB]

You can take the gear off the drill motor with a good old fashioned dremel. Just don't let shavings get in the motor. It's good fun, really.

We’ve been through this many (http://www.chiefdelphi.com/forums/showthread.php?t=24518) times (http://www.chiefdelphi.com/forums/showthread.php?t=22933) before. Do NOT Dremel off the drill pinion, and if you do, don’t encourage others to repeat your mistake. This can cause many problems including: damaging the output shaft, getting shavings in the motor, damage the motor in other ways, and just generally cause problems. Besides, if you’re removing the pinion, you’re going to need a press to put on the new gear anyway so why not just do the right thing from the beginning. If you don’t have access to a press, you can always use the mod 7 gears from PIC, as long as you order far enough in advance.

[Landon]

How many of those are you using?

[AlexR]

We’ve been through this many (http://www.chiefdelphi.com/forums/showthread.php?t=24518) times (http://www.chiefdelphi.com/forums/showthread.php?t=22933) before. Do NOT Dremel off the drill pinion, and if you do, don’t encourage others to repeat your mistake. This can cause many problems including: damaging the output shaft, getting shavings in the motor, damage the motor in other ways, and just generally cause problems. Besides, if you’re removing the pinion, you’re going to need a press to put on the new gear anyway so why not just do the right thing from the beginning. If you don’t have access to a press, you can always use the mod 7 gears from PIC, as long as you order far enough in advance.


Ok, lets think about this for a second. How many times have you tried to dremel the pinion off the drill motor and failed personally. 0. In fact, how many times have you actually tried to dremel the pinion off of a drill motor? 0. So, you have no right to say it shouldn't be done. If you do it carefully and cover the motor, you will have no problems. It's really very simple. You are basing your opinion off of zero evidence. So please stop talking.

[RobDeCotiis]

sarahb,
dremeling off the gear only poses a threat to the motor of you're lazy. Make sure you don't get shavings inside the motor and i see no reason dremeling the gear off would cause harm. Cutting into the drill motor shaft slightly won't cause problems, unless you hack it to bits. Some people don't have presses, and honestly, you don't need one. The dremel works fine for removing the gear, and simple expansion/contraction properties of the metals will allow you to put the gear on. freeze the motor(or just the shaft, assuming you have liquid nitrogen in your chem lab ;) ) and heat up the gear with a blowtorch and you'll be able to get it on, and when it cools down, good luck getting it off. Try to think a little more about reasoning before you post. You yourself have seen the motor ryan put the gear onto, you know it works fine, the motor isn't damaged, i don't really see what the problem is. anyway. beautiful looking gearbox, ryan. nice job ;)

Team 30 forever
Rob DeCotiis

[Rob Colatutto]

sarahb,
dremeling off the gear only poses a threat to the motor of you're lazy. Make sure you don't get shavings inside the motor and i see no reason dremeling the gear off would cause harm. Cutting into the drill motor shaft slightly won't cause problems, unless you hack it to bits. Some people don't have presses, and honestly, you don't need one. The dremel works fine for removing the gear, and simple expansion/contraction properties of the metals will allow you to put the gear on. freeze the motor(or just the shaft, assuming you have liquid nitrogen in your chem lab ;) ) and heat up the gear with a blowtorch and you'll be able to get it on, and when it cools down, good luck getting it off. Try to think a little more about reasoning before you post. You yourself have seen the motor ryan put the gear onto, you know it works fine, the motor isn't damaged, i don't really see what the problem is. anyway. beautiful looking gearbox, ryan. nice job ;)

Team 30 forever
Rob DeCotiis
I'm no electrician here... but I would take a guess and say putting your motor in liquid nitrogen is probably not a very good practice if you want to have a working motor... Taking a blow torch to the gear could also severly weaken it. There is nothing wrong with having concern and giving advice against doing something that you know isn't the correct method doing the job. We are trying to learn about engineering and teaching others in FIRST, not about cobbing up a job that is easily done correctly.

Ryan, could you post up or pm me the gear ratios in there? It appears that you have the bosch motor pulling up atwood above its free speed. (also not a very good thing to do)

[RobDeCotiis]

I'm no electrician here... but I would take a guess and say putting your motor in liquid nitrogen is probably not a very good practice if you want to have a working motor... Taking a blow torch to the gear could also severly weaken it. There is nothing wrong with having concern and giving advice against doing something that you know isn't the correct method doing the job. We are trying to learn about engineering and teaching others in FIRST, not about cobbing up a job that is easily done correctly.


dipping the shaft in liquid nitrogen won't cause any problems to the motor. using a blowtorch on the gear won't either. both of these are common practices in the engineering world. When fittings are needed that are extremely tight, to the extent that the shaft diameter is greater than the hole diameter by very large amounts, these practices are used along with a press fitting. The end result is an EXTREMELY tight interference fitting. If a team doesn't have a press, these practices are accepted in the engineering field, and because, as you say, we should be teaching engineering, i figured i'd throw a little bit more engineering knowledge into the mix, being that nobody's posted that as a way to fit the gear on. again, please look into what you're talking about before making blind assumptions

[SarahB]

sarahb,
dremeling off the gear only poses a threat to the motor of you're lazy. Make sure you don't get shavings inside the motor and i see no reason dremeling the gear off would cause harm. Cutting into the drill motor shaft slightly won't cause problems, unless you hack it to bits. Some people don't have presses, and honestly, you don't need one. The dremel works fine for removing the gear, and simple expansion/contraction properties of the metals will allow you to put the gear on. freeze the motor(or just the shaft, assuming you have liquid nitrogen in your chem lab ;) ) and heat up the gear with a blowtorch and you'll be able to get it on, and when it cools down, good luck getting it off. Try to think a little more about reasoning before you post. You yourself have seen the motor ryan put the gear onto, you know it works fine, the motor isn't damaged, i don't really see what the problem is. anyway. beautiful looking gearbox, ryan. nice job ;)


As Rob said before, using liquid nitrogen on a motor is a really bad idea. It could damage many parts of the motor, including the cracking the cooling fans or the bush assembly. I would listen to him, considering he knows enough to be a technical moderator of these forums.

Yes, I have seen the motors that Ryan modified. All of them have damaged shafts(lots of little cuts), at least one has shavings in it, and two have damaged bush assemblies. All three were replaced, and I believe the gears from the new ones were pressed off the right way.

Once again I will ask all of you to please stop encouraging other teams to damage their motors. If you don't trust my assessment that Dremeling off pinions is bad, please refer to the numerous other posts that agree, especially the ones by Paul Copioli (http://www.chiefdelphi.com/forums/showpost.php?p=216982&postcount=10), a well respected professional engineer and Unsung FIRST Hero.

[RobDeCotiis]

How exactly will cooling the motor damage it?

[sanddrag]

OMG, don't you all understand that they will not be dipping the whole motor in the LN. All they need to put in is like 1/2" for the shaft, not the whole motor can too. The only part in the LN should be the shaft.

[Venkatesh]

Each one of these has a weight of approximately 9 pounds. Fine devices, really. :]

[JVN]

sarahb,
dremeling off the gear only poses a threat to the motor of you're lazy. Make sure you don't get shavings inside the motor and i see no reason dremeling the gear off would cause harm.
Actually,
One of the best motor guys on these forums, a professional who does this thing for a living came on here and said NOT to dremel the drill pinion off as you will likely destroy your motor.

RobDeCotiis, please refrain from talking about things which you "know" unless you really know them.

Simply be searching these forums, you can find someone who's opinion really matters.

Team 30--
The gearbox looks good.
Unlike my teammate I won't try to count teeth and check your ratios. I just assume you would have done it right the first time. Good luck, and we'll see you in Long Island.

JVN

[Chris Fultz]

dipping the shaft in liquid nitrogen won't cause any problems to the motor. using a blowtorch on the gear won't either. both of these are common practices in the engineering world.

Cooling the shaft is probably OK. Blowtorching the gear probably is not. You can create huge stresses in the part, and you are chaning the material properties. The sudden change in temperature can be damaging. Parts are usually heted in a controlled process, like an oven that gradually increases the temperature.


When fittings are needed that are extremely tight, to the extent that the shaft diameter is greater than the hole diameter by very large amounts, these practices are used along with a press fitting. The end result is an EXTREMELY tight interference fitting.

Yes, the practice of creating interference fits is common and used in many engineering applications.

It is a very controlled process. Part diameters are defined, analysis is completed. An interference might be thousandths or ten-thousandths. When you create this tight fit, you add new stresses in the mating parts and if the fit is too tight, one or both parts can fail.

Do you know what kind of interference you are making? Did you measure the parts first?


and because, as you say, we should be teaching engineering, i figured i'd throw a little bit more engineering knowledge into the mix, ... again, please look into what you're talking about before making blind assumptions

No further comments.

[Mike Martus]

Caution to all reading this thread. Some of the processes expressed by some of the teams are very risky. Please use well thought out processes based upon "best practice" and above all practice safety at all levels.

Also consider advice from the persons that have expertise in the field of question as more reliable but not faliable. All are entitled to their opinion on how to best do something but again excercise caution.

[sanddrag]

We are broaching and milling keyways in all our gears this year to lock them to the shafts. While we have not run it under significant load yet, so far it appears to be functioning extremely well.

[Al Fielder]

In another post, I described how to remove the pinion from the Bosch motor. It really wasn't difficult. Taking a Dremel to remove the pinion seems to be alot of work, with risk, when a puller will work just fine. The press fit for a new gear should be in the .0003-.0005 range, specially if you are installing a gear with a P.D. of around .7-.8 so that you don't yield the new gear.
If the new gear yields, you lose the press.

[Dorsk65]

Well, on a completely different note, well done. This gearbox is vastly smaller and lighter than ours, mainly because our sprockets are 1:1, so we needed extra gears. We used the 20 Pitch gears also, and I hope to post pictures soon. The only problem we are having seems to be heat, so you might want to mount some fans on it.

Once again, very well done, paticularly on the weight and stability.

Robert Bloom

[Ryan Curry]

Well, on a completely different note, well done. This gearbox is vastly smaller and lighter than ours, mainly because our sprockets are 1:1, so we needed extra gears. We used the 20 Pitch gears also, and I hope to post pictures soon. The only problem we are having seems to be heat, so you might want to mount some fans on it.

Once again, very well done, paticularly on the weight and stability.

Robert Bloom

Thanks for the vote of confidence Robert, I hope to see pictures of your gearbox up here soon. Wish we were having your nice Hawaii weather here in the Northeast.

-Rc