2007 Motor Specs

[Madison]

Originally Posted by Kit Gerhart

Are we going to get power/rpm/ current information on these RS-540 motors as we have in the past with new motors in the kit, or do we have to estimate it ourselves?

I think the information you're looking for is available on the Banebots website.

The gearmotors specs. can be found here: http://www.banebots.com/pc/MP-36XXX-540/MP-36064-540

The motor specs. without the gearbox are here:
http://www.banebots.com/p/M2-RS540-120

They don't have the curves themselves, but there's at least some information available.

[Kit Gerhart]

Originally Posted by M. Krass

I think the information you're looking for is available on the Banebots website.

The gearmotors specs. can be found here: http://www.banebots.com/pc/MP-36XXX-540/MP-36064-540

The motor specs. without the gearbox are here:
http://www.banebots.com/p/M2-RS540-120

They don't have the curves themselves, but there's at least some information available.

There is some info on the banebots site, but not the actual power information I'd like. Of course, if I get a little more ambitious, I can calculate a good approximation of what I'm looking for. I'd like to know the maximum power in watts or horsepower that the motor produces.

[Kevin Sevcik]

Power (output) it torque times speed. Well... Watts = N-m * radians/sec. or = N-m * RPM/60*2*pi.

RPM decreases linearly from no load speed at ... no load, to zero at stall. Thus, max power is always at half the no load speed.

Thus, Max power for the RS540 is ~122W.
The RS 545 is 108W.

This is, of course, highly approximate. But you really should be designing below Max power anyways, right?

[Kit Gerhart]

Originally Posted by Kevin Sevcik

Power (output) it torque times speed. Well... Watts = N-m * radians/sec. or = N-m * RPM/60*2*pi.

RPM decreases linearly from no load speed at ... no load, to zero at stall. Thus, max power is always at half the no load speed.

Thus, Max power for the RS540 is ~122W.
The RS 545 is 108W.

This is, of course, highly approximate. But you really should be designing below Max power anyways, right?

Thanks for doing the calculation for me. Yes, we design for well below peak power (motor running maybe 75-80 % of no-load rpm) except for an occasional few seconds of "extreme" operation near its power peak. Most of our motors will have a very short service life if run at their power peak.

[Arkorobotics]

Would it be legal to buy 2 extra 56mm Planetary Gearbox, 12:1? The same one included in the KOP?


Also, how much do these gearboxes weigh?

[Kevin Sevcik]

Perfectly legal. It's COTS item offered by BaneBots and it costs less than $400. Well. Perfectly legal as long as you still stay under your $3500 limit.

EDIT: I weighed them in at around 2.5 lbs apiece last night. The only scale I had was a bit nutty, so YMMV by +/- .25 lbs.

[Arkorobotics]

Originally Posted by Kevin Sevcik

Perfectly legal. It's COTS item offered by BaneBots and it costs less than $400. Well. Perfectly legal as long as you still stay under your $3500 limit.

EDIT: I weighed them in at around 2.5 lbs apiece last night. The only scale I had was a bit nutty, so YMMV by +/- .25 lbs.

Thanks! Does that weight include the CIM? If not what is the mass of the CIM motors?

[Madison]

Originally Posted by Arkorobotics

Thanks! Does that weight include the CIM? If not what is the mass of the CIM motors?

They're about 2.5 lbs. without the motors. The motors themselves are about another 2.5 lbs. each, as I recall.

[Arkorobotics]

Originally Posted by M. Krass

They're about 2.5 lbs. without the motors. The motors themselves are about another 2.5 lbs. each, as I recall.

Thanks! I am just surprised they didn't give the dimensions and weight of the gearbox.

[Rickertsen2]

I calculated the theoretical speed/torque/power curve for the RS-540. I would post a graph here, but right now all i have available is open office.org which isn't very good at drawing the graph scales the way i want it to. I can export it to xls or csv or something though.

It may not be exact but should be pretty close.

Note: Calculated @12V

Speed(rpm)	Torque (mNm)	Power(watts)
0		277.20000	0
100		275.55000	2.89
200		273.90000	5.74
300		272.25000	8.55
400		270.60000	11.33
500		268.95000	14.08
600		267.30000	16.79
700		265.65000	19.47
800		264.00000	22.12
900		262.35000	24.73
1000		260.70000	27.3
1100		259.05000	29.84
1200		257.40000	32.35
1300		255.75000	34.82
1400		254.10000	37.25
1500		252.45000	39.65
1600		250.80000	42.02
1700		249.15000	44.35
1800		247.50000	46.65
1900		245.85000	48.92
2000		244.20000	51.15
2100		242.55000	53.34
2200		240.90000	55.5
2300		239.25000	57.62
2400		237.60000	59.72
2500		235.95000	61.77
2600		234.30000	63.79
2700		232.65000	65.78
2800		231.00000	67.73
2900		229.35000	69.65
3000		227.70000	71.53
3100		226.05000	73.38
3200		224.40000	75.2
3300		222.75000	76.98
3400		221.10000	78.72
3500		219.45000	80.43
3600		217.80000	82.11
3700		216.15000	83.75
3800		214.50000	85.36
3900		212.85000	86.93
4000		211.20000	88.47
4100		209.55000	89.97
4200		207.90000	91.44
4300		206.25000	92.87
4400		204.60000	94.27
4500		202.95000	95.64
4600		201.30000	96.97
4700		199.65000	98.26
4800		198.00000	99.53
4900		196.35000	100.75
5000		194.70000	101.94
5100		193.05000	103.1
5200		191.40000	104.23
5300		189.75000	105.31
5400		188.10000	106.37
5500		186.45000	107.39
5600		184.80000	108.37
5700		183.15000	109.32
5800		181.50000	110.24
5900		179.85000	111.12
6000		178.20000	111.97
6100		176.55000	112.78
6200		174.90000	113.56
6300		173.25000	114.3
6400		171.60000	115.01
6500		169.95000	115.68
6600		168.30000	116.32
6700		166.65000	116.93
6800		165.00000	117.5
6900		163.35000	118.03
7000		161.70000	118.53
7100		160.05000	119
7200		158.40000	119.43
7300		156.75000	119.83
7400		155.10000	120.19
7500		153.45000	120.52
7600		151.80000	120.81
7700		150.15000	121.07
7800		148.50000	121.3
7900		146.85000	121.49
8000		145.20000	121.64
8100		143.55000	121.76
8200		141.90000	121.85
8300		140.25000	121.9
8400		138.60000	121.92
8500		136.95000	121.9
8600		135.30000	121.85
8700		133.65000	121.76
8800		132.00000	121.64
8900		130.35000	121.49
9000		128.70000	121.3
9100		127.05000	121.07
9200		125.40000	120.81
9300		123.75000	120.52
9400		122.10000	120.19
9500		120.45000	119.83
9600		118.80000	119.43
9700		117.15000	119
9800		115.50000	118.53
9900		113.85000	118.03
10000		112.20000	117.5
10100		110.55000	116.93
10200		108.90000	116.32
10300		107.25000	115.68
10400		105.60000	115.01
10500		103.95000	114.3
10600		102.30000	113.56
10700		100.65000	112.78
10800		99.00000	111.97
10900		97.35000	111.12
11000		95.70000	110.24
11100		94.05000	109.32
11200		92.40000	108.37
11300		90.75000	107.39
11400		89.10000	106.37
11500		87.45000	105.31
11600		85.80000	104.23
11700		84.15000	103.1
11800		82.50000	101.94
11900		80.85000	100.75
12000		79.20000	99.53
12100		77.55000	98.26
12200		75.90000	96.97
12300		74.25000	95.64
12400		72.60000	94.27
12500		70.95000	92.87
12600		69.30000	91.44
12700		67.65000	89.97
12800		66.00000	88.47
12900		64.35000	86.93
13000		62.70000	85.36
13100		61.05000	83.75
13200		59.40000	82.11
13300		57.75000	80.43
13400		56.10000	78.72
13500		54.45000	76.98
13600		52.80000	75.2
13700		51.15000	73.38
13800		49.50000	71.53
13900		47.85000	69.65
14000		46.20000	67.73
14100		44.55000	65.78
14200		42.90000	63.79
14300		41.25000	61.77
14400		39.60000	59.72
14500		37.95000	57.62
14600		36.30000	55.5
14700		34.65000	53.34
14800		33.00000	51.15
14900		31.35000	48.92
15000		29.70000	46.65
15100		28.05000	44.35
15200		26.40000	42.02
15300		24.75000	39.65
15400		23.10000	37.25
15500		21.45000	34.82
15600		19.80000	32.35
15700		18.15000	29.84
15800		16.50000	27.3
15900		14.85000	24.73
16000		13.20000	22.12
16100		11.55000	19.47
16200		9.90000		16.79
16300		8.25000		14.08
16400		6.60000		11.33
16500		4.95000		8.55
16600		3.30000		5.74
16700		1.65000		2.89
16800		0.00000		0

[Joel J]

Where did you get these numbers? You tested the motor?

[Rickertsen2]

Originally Posted by Joel J.

Where did you get these numbers? You tested the motor?

No, they are a purely theoretical APPROXIMATION based on the Kt, Kv and stall current posted on the bane-bots website.

They are based on a model which works pretty well for DC motors in which torque is porportional to current and back emf is porportional to motor rpm. This model does not take into account inductive effects or internal bearing resistance of the motor.

Kt is a constant of porportionality relating motor output torque to electrical current input.
Kv is a constant which relates the rotational speed of the shaft to the voltage generated by the motor.

torque = I*Kt
Induced back emf(voltage created by the motor) = shaft speed * Kv
r= internal resistance of the motor = supply voltage/stall current.

combine these three and you get
torque = Kt*(Vin-Kv*rpm)/r

then for mechanical power in a rotating system we have
power = speed * torque
so
power = rpm*Kt(Vin-Kv*rpm)/r

sorry ,that was a Terrible explanation, but its 3:29 am and i'm tired.

[GramNegative]

Earlier, Rickertsen2 posted a formula for motor output torque using these calculated values:

torque = Kt*(Vin-Kv*rpm)/r

Does anyone know if there is there an advantage to using this formula over:

Torque = (-T0/Wf)*W+T0, Where T0 is torque at stall and Wf is free speed

If so, is there more documentation somewhere that explains how/why this works better?

Thank you,
Chris

[Paul Copioli]

Earlier, Rickertsen2 posted a formula for motor output torque using these calculated values:

torque = Kt*(Vin-Kv*rpm)/r

Does anyone know if there is there an advantage to using this formula over:

Torque = (-T0/Wf)*W+T0, Where T0 is torque at stall and Wf is free speed

If so, is there more documentation somewhere that explains how/why this works better?

Thank you,
Chris

The equation using torque constant (Kt) and back EMF constant (Kv) is the theoretically pure way to calculate motor performance. However, most motor manufacturers will not give you all of these numbers. All motor manufacturers will give you stall T, free speed, Stall current, and free current (no load current) and it is all you need to size motors and gearboxes for the job.

[GramNegative]

Thank you for the help. Now that my curiousity is satisfied, I think it's time for bed.