Are you sure about this? The motors aren't turning when they are stalled, so you cant use RPM and stall torque together...?

Greg

If you check today's team update, it has something about reusing motors, so I take it as the motors you are allowed to reuse are essentially the same, while the motors you can't reuse are different.
You CAN reuse the Chalupa/Atwoods and Globes, so I'm guessing they're the same.
You CANNOT reuse the Fisher-Price, drill-motors and window motors, so I'm guessing that means they're different

Im going to have to agree with those that think the Chips are more powerful. My reasoning does have to do with the size of the motor, but of the windings. Since the Chip is bigger it MOST likely has a larger gauge wire for the windings and can draw more power without heating up as much and is less likely to blow the breakers. And even if the chip doesn't have larger gauge I'm pretty sure the its has more windings and probably more sections (I know theres a more technical term im trying to say the amount of coils on the armature itself) If someone is willing to take one apart to see whats really in there that would be great. I don't think my team would appreciate me taking it apart since i will most likly not be able to get it back together.

The number of turns is how many times the wire goes around the armature. Less turns means more power/rpm. The winding is the number of strands in the wrap. Usually between one and four. More strands will give you more torque at a higher RPM, less strands will give you more torque at a lower rpm for more "punch" As for why things work ou this way, I really don't know. This is just what an expert in the industry told me.

Running the numbers on the two through the Motor Calc spreadsheet from last year and using the drill specs found in this post:
I get a peak power of ~450W for the drills and ~300W for the Chiapuas.

Stall torque at our proposed gear ratios is 106N-m vs 80N-m

It is RIDICULOUS that we don't have spec sheets!!:ahh:

Absolutely Positive
 

GregT,

Believe me when I tell you that the calculation for DC motor max mechanical power is approximately:

PMax = (Tstall/2) * (FreeSpeed/2) *(2*PI/60)

The 2*PI/60 is the conversion from RPM to rad/sec which will give you power in Watts. This calculation is used to determine the peak motor mechanical power.

To those that agree with GregT: In this case size doesn't mean anything. The drill motors have more power than the Chiaphuas no doubt about it.

-Paul

Trust Paul on this one
 

I would go with Paul's calculations on pretty much anything,
any doubts go look in the white papers at the CCT!!!!!

Chalupas
 

NOTE: Chiapuha, Chippawa, Atwoods, etc. will henceforth be known as "Chalupas"

The difference between the Bosch and Chalupa motors is where they develop their power (torque) just like in automotive engines. Truck engines (Chalupas) develop huge amounts of low-end torque, but don't do too well at high speeds and need to be geared up substantially. An RX-7's rotary engine (Bosch) gets crappy low-end performance but does great at high speeds. I don't know how different the new drill motors are, but going by last years specs it comes out like this:

The Bosch motors (sans gearbox) have insanely high rpm but crappy torque. Also, the torque they do have is only developed when running full-bore.

The Chalupas have great low-end torque, with decent speed.

The advantage of the Bosch motors is that with the included gearbox, they can be slightly more powerful than the Chalupas (approx. 340 watts to 320 watts by last years specs)

The disadvantage is that their is an ever so slight lag from when the motor spins up to 20,000 rpm, to when the power comes out of the gearbox at 400-1500 rpm. With the Chalupa, you can use a simple 1:7 reduction, and have all of the power exactly when you need it.

Personally, I perfer the Chalupa's because I think they are easier to work with, and the difference between the two motors is negligible.

But if what everyone is saying is true, that the Bosch's this year are considerabley more powerful, then the drill motors may be the best bet.

Background for Paul's Calculations
 

Paul's calculations are correct. I threw together a quick explaination of the math behind it. I hope this helps anyone that still doubts his calculations.

-Chris

could you put that in a mac-compatable format please?

Stupid macs

PDF Version
 

I attached a PDF version to this. If you can't open this, let me know.

-Chris

Question about Paul's calculation
 

Just wondering. Since the circuit breaker on the drill motor is a 40 amp, are TStall/2 and FreeSpeed/2 really the correct operating points, since they imply a current draw of around 63 amps, which will blow the breaker? Seems like TStall/3 and and FreeSpeed/3 are more appropriate, or am I just confused? Or do people just hope the breaker takes longer than 2 minutes to blow? If this change is right, it reduces the effective power available by a factor of 4/9, or to about 44% of the absolute maximum power.

Thanks for letting me debug my meager motor knowledge here.


-- Jeff

You Got It!
 

You actually hit the nail right on the head! I was just demonstrating that the drill motor is more powerful than the Chiaphua. If you look at the following whitepaper, it will tell you all you need to know. It is my presentation at the Novi Kickoff in Michigan.

http://www.chiefdelphi.com/forums/pa... SC&sort=date

This should clear up a lot.

-Paul

Thanks
 

Thanks for the excellent upload. Really helpful stuff.


-- Jeff