Cim Mounting

[Thunder360]

I know there has been alot discusion about the right way to mount the Cim's. I was just taking a look at some nice ways to mount them. I was thinking 2 car exhaust U claps would work just fine, so what I want to know is if any team has a better way to mount them?

[Bill Gold]

When we used the Atwoods last year in our drive system, we just mounted them by using the tapped holes near the output shaft.

http://www.seadawgs.com/Pictures/200.../newdrive2.JPG

http://www.seadawgs.com/Pictures/200...newdrive1s.JPG

I'll try to look for better pictures if you want.

[Thunder360]

Any pictures would be great, I just dont like the tap type set-up it seems a lil weak for the type of torque we will be putting on them. I mean 2 small screws wont last your forever with a crap load of torque, and weight shift......will it?

P.S. if any one has pictures of Cim set-ups from last year of any kind that would be great thanks!

[Bill Gold]

Throughout the 2002 season (Silicon Valley Regional, The Championship Event, and the California Robot Games) we used only the atwoods as our motors. That sprocketbox in the links I pasted earlier has two reductions, 10:1 (~11 ft/sec) and 100:1(~1 ft/sec while lifting up on one goal). We never had a problem with the screws loosening or shearing. I trust that mounting setup.

[Thunder360]

I dunno I feel alot better using car exhaust C clamps.

Anyone know the # of magnets and windings in the Cim's?

[dlavery]

Try a little math....

The mounting holes on the face plate of the Chiaphua motors are 1.002" from the line of rotation of the rotor, and tapped for 10-32 machine screws.

The minor diameter of a 10-32 screw is 0.1840 inches (ref: Machinery's Handbook 26). This yields a minimum cross section for the screw of 0.0266 square inches. Let's go with the worst case, and assume you are using a low-end SAE Grade 1 screw, made of low carbon steel. Material yield strength is 36,000 psi. Cross section times strength equals a shear strength of 957 pounds. At a one inch standoff distance, the screw is capable of withstanding 79.77 foot-pounds of torque.

Multiply that times two (you are using two screws to mount the motor), and you will see that this simple mounting method can withstand 159.4 foot pounds of torque. And remember, this is worst case, using a low-strength material and calculating yield strength instead of true shear strength. Try a medium or high-quality fastener with a decent yield strength (say ASTM A490, with 130,000 lbs yield), and you will get a much better result.

The Chiaphua motor at full stall exerts 276 oz-in, or 1.4375 ft-lbs, of torque (ref: CCL Industrial Motor Limited spec sheet).

Mounting with two screws would be more than adequate (by a factor of over 100). U-clamps are unnecessary, and just add extra weight to your robot.

-dave

----------------------

Y = AX^2 + B.... ehhh, whatever

[Thunder360]

Thanks, But whats wrong with using U clamps there strong, and are ease to install and take out if need be. Also my trannys pneumaticly shifted and 2 cylinders run perpendicular ot the Cim and they do exert a lil force on the mounted motor. Im im scared the jaring from the pneumatics may bust those screws, Thus me using 2 or 3 Exhaust claps per moror with a thin steal plate holding it in one place. I just need to know if the U clamps will hold under a beating.

[Andy Baker]

There is nothing wrong with using u-clamps, and they will hold the motor very securely... but I agree with those above that they are overkill and the #10-32 tapped holes are good enough to hold the motor.

We had a very robust drive train last year with a shift-on-the-fly transmission and we mounted the CIM motor with only 2 #10-32 FHSCS's.

See the attached picture.

Andy B.

[Katie Reynolds]

Yeah, that's pretty much what ours motor 'mounts' looked like last year ... I'll get a picture up as soon as I can.

- Katie