Slickest drive transmission yet...

[Manoel]

Originally Posted by JVN

Jim,
Funny you mention this.
Heat treating came up the other day in a 229 design discussion.

If you (or anyone else) knows more about this process.
Please share!

I have the vaguest understanding.
I'm especially interested in "home" heat treating. I think it is possible to temper a shaft using only a torch and a coffee can of oil. Is this true?

John

Not sure if you already seen it, but Dave wrote one of his memorable posts about it a while ago. Here it is.

[JVN]

Originally Posted by Manoel

Not sure if you already seen it, but Dave wrote one of his memorable posts about it a while ago. Here it is.

Manoel,
I had seen that before, but obviously forgot COMPLETELY about it.
Thank you for bringing it to my attention.

Remember folks, don't be like JVN -- search before you post.

John

[dlavery]

Originally Posted by Manoel

Not sure if you already seen it, but Dave wrote one of his memorable posts about it a while ago. Here it is.

Thanks for remembering the post, hopefully you will find it useful. Here is a little additional information -

If you do a water (instead of oil) quench for the hardening/tempering steps, you can improve the results and consistency of the hardening by using an appropriate surfactant in the water. As you quench the part, bubbles form in the liquid at the interface between the hot part and the quenching fluid. You want to move the bubbles away from the hot metal as quickly as possible, and and keep a solid surface of quenching fluid against the metal. The surfactant will break the surface tension around the bubbles, and allow them to quickly seperate from the metal and float free in the fluid. This will allow the fluid to restore contact with the metal, and lets it do its work cooling off the part. The "magic mix" that I use is 1/4 cup of Cascade dishwasher powder per gallon of water. DO NOT use a liquid dish soap or laundry detergent! You want something with a low "suds content" that will not foam up when you stir it around (remember, we are trying to avoid bubbles here!).

If you are using a low-carbon or mild steel, you will want an alternative to the quench-and-temper process (which is really only effective on high-carbon steels like tool steel). For low-carbon steel you can do small-job case hardening (which will basically add carbon to the surface of the metal and increase its ability to be temperature hardened). Heat up the part until it is cherry red, bury it in a surface hardening compound, reheat it and cool by quenching. The compound (I use Kasenit, available from MSC, and there are others) will provide a surface case hardening a few tens of mils deep, which should be good for most applications that we will run across. The case hardening will give you a harder surface, but the effect will not penetrate as deeply into the metal as the quenching/tempering process. You will have to figure out where you want to be in the hardness/depth trade space based on your application.

(note: there has been a lot of discussion recently in the hobby machinist community on this topic recently - if you can grab a few of the recent issues of the Home Shop Machinist, there are some good articles that will provide additional information)

-dave

[ChuckDickerson]

Jim,

Thanks for the additional information. That's what I was assuming on 1, 2, & 3 but just wanted to make sure. I don't know anything about hardening/heat treating either but if you can relay the info from your folks I'll pass it on to our folks.

Thanks,
Chuck

[Eric Yahrmatter]

Hey, if u have any questions about our trannys or how they were built ask me because I built them!

Have fun @ all ur regionals.
-Eric Y

P.S. Killa Bees in da club!!!

[Sam J.]

I saw the robot in competition, and it was great. I was really impressed with how you were able to speed accross the field at high speed, then push the mobile goal with little effort. I am guessing that this is a shift on-the-fly transmission. Could someone tell me how some teams have transmissions that cannot be shifted while driving, and others can? How are they diffrent? Sorry if these sound like stupid questions to you but, I do not know that much about drive systems.

[Salik Syed]

They are all different........most of the shifting ones i've seen have 2 sets of gears and a pneumatic slides an input gear into one gear and out of the other, one that we built a while ago based on Technokats had dogs which catch on to the gears and engage them...the gears are on bearings so they don't do anything without a dog...
its kinda hard 2 explain...check out some pics and you will understand

[Paul H]

Sam, I know that some teams shift the drill transmission with servos, and to the best of my knowledge, these cannot be shifted on the fly.

[Dima]

Very Nice, Very simple. The best part is definaly making it automatic. It is something new and refreshing so to speak. Very cool that you guys actually took time to calculate the power curves and shift at the right points, props to you guys!

Originally Posted by Paul H

Sam, I know that some teams shift the drill transmission with servos, and to the best of my knowledge, these cannot be shifted on the fly.

Except for Chief Delphi this year apperantly

[FotoPlasma]

I really must say that this is an awesome system. Congrats to team 33.

I've thought of automatic transmissions for a couple seasons now, and I never thought of monitoring output RPM. In my theoretical designs for an automatic transmission, I would have monitored current to the motor, and shift based on that information. At different gear ratios, the stall current of the motor is constant, and if you set upper and lower thresholds, you can shift up or down, depending completely on whether you need less or more pushing power, respectively. I'm sure it's more complicated than I'm making it sound, but as I said, I'm stuck in the realm of theory, here.

Just my take on the theory of an automatic transmission. With all of the talk of constructive vs. destructive criticism that went on recently, I want to say that I'm very impressed by this system. Again, many congratulations to 33.

[matt111]

well our team, 1024, design a CVT VST (continious velocity, torque, variable speed transmission). it uses bevel gears and three planetary gear systems. then we ran into the problem: it was gonna weigh around 30 lbs!!! so i was told to design a casing to replace the alumnium box it was going in (around half the weighht). well we ran out of time, but i did get a nifty looking case made from a FDM prototyping machine. Hopefully (crosses fingers) we will have it done at IRI. we had two allision transmission engineers helping us design, so hopefully we can have something to show for my 10+ straight weeks of doing CAD for this. and yes i did start in the offseason..and yes it is still not done

[Ryan F.]

I was wondering if I could get some peoples opinion over weather a variable speed/torque transmission is a big advantage, or a lot of work for nothing. Our team has a CIM/Drill motor combo for our drivetrain, with no special shifting gearbox, and we seem to have pleanty of speed and torque.

[tkwetzel]

I'm sure it's more complicated than I'm making it sound, but as I said, I'm stuck in the realm of theory, here.

Programming the robot to shift really shouldn't be too complicated, with encoders measuring the speed of the output shaft or the axles. Especially since they calculated the power curves and everything. With the power curves, they can determine the best shift point to gain the most power. Finding the shift points is the hard part. Then you prgram it to shift when the encoders measure a certain speed determined by you to be your shift point. You can also calculate downshift points as well the same way.

[jimfortytwo]

rforystek:
That might be a debate for a different thread. To answer your question, though this thread from last summer contained some good debate on that topic (4 motor vs. shifters). The fourth page of replies in particular is well worth a look.

http://chiefdelphi.com/forums/showth...g+motor+debate

[Greg Perkins]

team 151's drive this year was awesome as well... they designed the system with simplicity in mind, as well as sleek and compactness as well..
a far shot, but their tranny are smaller than the aluminum tubing

they made a new gearbox for the drills using the previous planetary gears, and made a new housing...it was gorgeous...they also implemented the pneumatic shifting, and ran the pneumatic shifter inside the drive shafts to save space...tthis thing was gorgeous...