Big Black Motors

[Kit Gerhart]

Is there any torque/rpm/current draw data on the new big black motors? There didn't seem to be anything about them in our initial package of info. Also, does anyone know the normal use of these motors?

[ggoldman]

There is information on the motors on page G-25, they are easily confused with the bosch drill motor, so watch out.

[TF8]

that info is for the little mabuchi not the big chuachi or what ever its called

tyler forbes

[Joe Johnson]

They are made by Chiaphua. They are used in Atwood Mobile Power Jacks. All models of power jacks use the same motor and the same gear cluster mating with the motor (the very one in the kit -- thanks to Atwood -- this makes a very nice addition to the kit just a bit easier to use). The jacks are available at most RV centers, in stock. Cost is $150-200 or so based on the model and the markup of the dealer.

Atwood Mobile Power Jack



Specs should be out soon but as I recall, the numbers are 2.2N-m stall torque. 107Amp stall current, 5500RPM free speed, ~2 Amps free current (all @ 12V).

The output gear is VERY non-standard. It is a 36 Diametral Pitch, 9 tooth, enlarged, 25 degree pressure angle gear. Actual data should be out soon.

The gear that mate with it is a 44T gear (4.888:1 ratio). The center distance will have to be slightly enlarged from nominal I think, though I am not sure of the exact value -- it should not be too fussy. The smaller gear clustered with this gear is a standard 32 D.P. gear

By the way, it was touch and go getting these beauties in the kit. I have been working with Chiaphua for months to get these babies in the kit, it almost didn't happen. In the end, Chiaphua gave us a good price, I BEGGED my management for some funding to cover most of the price and then I BEGGED FIRST to kick in the balance of the funds to seal the deal.

I am very happy that we ended up getting these in the kit. I hope that they work out well for all teams.

Joe J.

[Andy Baker]

Joe,

This motor is drop dead gorgeous!

Thanks for your efforts. Teams will definitely appreciate this new "big kid on the block". Now... back to the drawing board.

Andy B.

[Kit Gerhart]

Thanks for the tech info, and for your effort in getting these motors in the kit. I suspect that there will be some 'mean machines' this year. It looks like we have a lot of available horsepower for our robots. Those 60A breakers may be more of a problem than in the past, though. Does Small Parts sell dry ice?

[Paul Copioli]

Thanks Joe for the info.

I came in to work today, just to check the forum, because I knew you would have the info.

For our team's sanity, we are calling the motor the "Chalupa".
(Chicken Chalupa)

-Paul

[Joe Johnson]

The company pronounces their name l"Chip-ee-wah" (like the Native American tribe) at least in English speaking countries.

The company has engineering in Toronto (among other places)and manufacturing in China. I suspect that the name sounds more like "Chee-a Poo-a" in Chinese (neglecting the all important tones that are an integral part of the language).

One more thing that folks should know about heat and motors and scaling of sizes:

Roughly speaking, the heat dissipation rate (heat power) is proportional to the area times the delta in temperature.

If you double the size of the motor, you quadruple the surface area of the motor. So... If you have the same about of heat generated per second inside your motor windings but the motor is twice as large, you will only generate 1/4 the delta in temperature that the smaller motor would generate.

Note, to first order, the drill motors and the Chiaphua motors are the same power ratings, given approprate gearing, they will do the same job in the same time generating the same electrical losses (i.e. heat).

Bottom line: If your drill motors were hot enough to boil spit (the true measure of all hot things by the way), the Chiaphua motors (geared appropriately) will only be warm to the touch*.
Think Cool Thoughts...

Joe J.

*for the purposes of the explanation boiling spit was taken to be 212 degrees F and room temp was taken to be 75 degrees F. In this case, "warm to the touch" works out to be about 110 degrees F (75 + (212-75)/4) Very nice indeed...

[Tom Fairchild]

We really appreciate the info on the motors, Joe. Any idea if you can get us a curve for it?

~Tom Fairchild~, who's loving these things.

[Marc P.]

I like these big suckers, but how many are we supposed to have in the kit, and how many are we allowed to use? I think the list of parts for the kit says 1, but when we opened our kit we found 2. Is this allowed or is it a mistake?

[Katie Reynolds]

Originally Posted by Marc P:
I like these big suckers, but how many are we supposed to have in the kit, and how many are we allowed to use? I think the list of parts for the kit says 1, but when we opened our kit we found 2. Is this allowed or is it a mistake?

If you look at the Kit of Parts checklist it says that 2 Chiphua motors should be included. But there is also other documentation that says we should only recieve one. I asked one of my advisors that was at the Kokomo kick off and he said that it was said that we should all be recieving two Chiphua motors so I am guessing that this is perfectly legal. I believe that everyone got two Chiphua motors in their kit so... I hope this helps!

- Katie

[Kit Gerhart]

[i]

If you double the size of the motor, you quadruple the surface area of the motor. So... If you have the same about of heat generated per second inside your motor windings but the motor is twice as large, you will only generate 1/4 the delta in temperature that the smaller motor would generate.

[/b]

Doesn't this assume that temperature rise is only a function of the thermal mass of the motor and that cooling is only a function of 'radiation' from the outside of the motor? This is probably a good model for what might happen with drive train motors in a two minute match, but for lighter loads, when allowed to 'spin,' the drill motors can have a fairly low equilibrium temperature because of the cooling from the little fans that pull air over the armature and commutator. We can run our robot indefinitely in low gear without the motors getting very hot. Of course, when running for a long time in high gear, more heat is generated and the fans don't move as much air, so occasionally the smoke leaks out of the motors.

[Anton Abaya]

these are motors? i thought they were pencil sharpeners.

-antoninny

[Joe Johnson]

As to Temperature effects...

Thermal mass helps the things stay cool in the short run but not in the long run because eventually the mass is the temp of the windings.

My first order analysis does not take the airflow into account which can be a big effect (as you will find out if your motor mounting design blocks the holes on the drill motor -- they run MUCH hotter with the holes blocked.

But, my basic point is still valid. Doubling the motor size more than halves the temperature rise inside a motor for a given amount of heat per second generated by the I^2R losses of the motor windings.

As to speed torque curves...
Download the FIRST MOTOR CALC spreadsheet from the whitepapers section of this website and you can plot them yourself -- all the data you need is the 4 numbers I gave you.

Joe J.

[ggoldman]

Joe....


The motors in question....(big Black ones)....

A couple questions about them

1) What is their function in the real world...do they turn a lead screw which in turn jacks up RV's or what not?
2) Are the mainly speed or torque?


Also, we have read the manual over and over again but have not found any rule limiting the quantity of motors allowed on the robot. I know this doesnt sound right. Can you straighten this out for me

THanks

Gabe G.