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#### s80ts0465

• Jr. Member
• Posts: 28
##### Gear Head Motor 380K75 Tamiya
« on: November 29, 2007, 08:26:59 AM »
I've found this kit:
http://www.tamiya.com/english/products/72101motor_tire/index.htm
at
http://www.superdroidrobots.com/shop/item.asp?itemid=675&catid=7

What about it? Is its a good choice?

I've used the RMF calculator and i've found this values:

Desired Robot Inputs:
Mass       2Kg
Desired Velocity    2m/s
Desired Acceleration    0.3 m/s^2
Expected Efficiency    75   %
Incline Angle    0   degrees
Wheel Diameter       4''
# of Powered Wheels       4 wheels

RMF Results:  0.348 Kg*m*rps
RMF       4.00   Kg*m*s
Momentum Motor Rotation Speed       376rpm

Motor Characteristics:
Torque       0.3617 lb*ft
Speed       242rpm
Motor RMF    0.202

So comparing the two RMF these motors should be ok for my project.
Do you suggest me some other product? why?
or do youadvise against there motor??

For a robot which is the velocity and the accelerator do you think it's more correct to use?? My robot will not be used for car race or combat, simply go around and pick u some radiation measure.

Still one question. This motor has a current consumption at no load of 0.67A. is it a lot??? This mean that if i have 4 motor, totally i should have more than 2A current consuption?

bye Ste
« Last Edit: November 29, 2007, 08:59:45 AM by s80ts0465 »

• Supreme Robot
• Posts: 11,653
##### Re: Gear Head Motor 380K75 Tamiya
« Reply #1 on: November 29, 2007, 12:05:50 PM »
Hmmm according to your numbers your robot needs RMF of .348 per motor, but your motor only does RMF .202 . . .

Quote
For a robot which is the velocity and the accelerator do you think it's more correct to use?? My robot will not be used for car race or combat, simply go around and pick u some radiation measure.
for a small autonomous robot you don't want more than ~1 m/s, and even that is a bit too fast.

I'd do acceleration of .3 m/s^2 and velocity of maybe .8 m/s

Quote
Still one question. This motor has a current consumption at no load of 0.67A. is it a lot??? This mean that if i have 4 motor, totally i should have more than 2A current consuption?
For a motor, that isn't that much. Stay under 2A per motor and it will be really easy/cheap to find motor drivers you like.

#### s80ts0465

• Jr. Member
• Posts: 28
##### Re: Gear Head Motor 380K75 Tamiya
« Reply #2 on: November 29, 2007, 12:55:46 PM »
Hmmm according to your numbers your robot needs RMF of .348 per motor, but your motor only does RMF .202 . . .

Yes i've reportedit wrong  later i'll update it.

For a motor, that isn't that much. Stay under 2A per motor and it will be really easy/cheap to find motor drivers you like.

about the motor controller do you suggest me to choose a PWM controller considering the lower consumption or also the other are ok?
i think this is ok: http://www.superdroidrobots.com/shop/item.asp?itemid=583

bye

• Supreme Robot
• Posts: 11,653
##### Re: Gear Head Motor 380K75 Tamiya
« Reply #3 on: November 30, 2007, 05:27:38 PM »
Hmmmm figure out your current and voltage first before choosing a driver . . . if you get a driver that is overkill, its just a waste of money . . .

#### s80ts0465

• Jr. Member
• Posts: 28
##### Re: Gear Head Motor 380K75 Tamiya
« Reply #4 on: December 01, 2007, 01:29:24 AM »
current and voltage of the motorr ?!?!

As you suggest me i've decide to choose a motor with 12V or less (as tamida 7.5V) and about the current, i don't want to go higher than 1A for motor due to consumption.

At the moment i can choose between:
at
http://www.superdroidrobots.com/shop/item.asp?itemid=721&catid=7  (12V   0.15A no load , 0.9 on nominal)

so which motor controller is better for me about you???
pwm http://www.superdroidrobots.com/shop/item.asp?itemid=583 (12-55V input and can manage 3A output, so enough for two motor)
or
http://www.superdroidrobots.com/shop/item.asp?itemid=345&catid=5 (5V input and can handle 5A outpu)

isn't the pwm better for lower power consumption??

• Supreme Robot
• Posts: 11,653
##### Re: Gear Head Motor 380K75 Tamiya
« Reply #5 on: December 01, 2007, 09:11:51 AM »
Hmmmm given your two listed options, I would suggest getting either a 7.2V or 8.4V battery. Higher voltages require larger and more expensive batteries, so its best to use the smallest option you can.

The superdriod one says 900mA. So power is 12V*.9A= 10.8W. You can use either motor driver with this motor.

And amazingly the tamiya one actually gives a useful torque chart (very bottom)!!! Use it to match the torque you expect to the output current. For example, if you will have 1.2Nm torque, then current is ~5A. I wished more motors have published charts like this, you are lucky. Power will be 7.2V*5A = 36W (if you used a 7.2V battery). The devantech motor driver doesn't list maximum power, but I think it can handle this. The other driver cannot.

You might also like these motor drivers:
http://www.dimensionengineering.com/Sabertooth2X5.htm
http://www.dimensionengineering.com/Sabertooth2X10.htm

Quote
isn't the pwm better for lower power consumption??

all motor drivers use PWM - it doesnt improve efficiency, its a method for speed control

#### s80ts0465

• Jr. Member
• Posts: 28
##### Re: Gear Head Motor 380K75 Tamiya
« Reply #6 on: December 01, 2007, 12:13:33 PM »
But reading the graph it really seems that this motor has a high current consumption! at no load it need 0.7A!! isn't toooo  much, above all the other motors, expecially the type i linked before?? comparing the other motor solution (linked before) at the same torque level of 0.46Nm (that i don't think too bad...or am i wrong?) the tamiya needs ~2A besides the IG32 only 0.9A !!!!
It sound stange...a lot of difference and a high current needs!

Is it correct??  or your experience tell you that this tamiya motors are really good as current consumption??

Which could be a good torque level for your experience???

• Supreme Robot
• Posts: 11,653
##### Re: Gear Head Motor 380K75 Tamiya
« Reply #7 on: December 01, 2007, 02:19:53 PM »
Just for reference to put things in perspective . . .
A typical medium size battle bot will draw from 20A-80A of current per motor. A full size battle bot will draw 100A plus! A typical servo draws from .5A to 2A.

Quote
Which could be a good torque level for your experience???

you must calculate it
http://www.societyofrobots.com/mechanics_dynamics.shtml#wheeldiameter

#### s80ts0465

• Jr. Member
• Posts: 28
##### Re: Gear Head Motor 380K75 Tamiya
« Reply #8 on: December 01, 2007, 04:51:45 PM »
Just for reference to put things in perspective . . .
A typical medium size battle bot will draw from 20A-80A of current per motor. A full size battle bot will draw 100A plus!

and which type of batteries do they have ?!?!!?!?!?!??!

Anyway i guess i've to start to think to spend a lot of money for the batteries. Considering that in my project the motors draws most of the current, the ig32 ~4A and the tamiya ~8A, and that i should use the motor in  continuos way for at least 1 hour,    i've to buy at least a battery of ~4000-~8000mAh only for the motors
« Last Edit: December 01, 2007, 05:03:09 PM by s80ts0465 »

#### maverick monk

• Robot Overlord
• Posts: 204
##### Re: Gear Head Motor 380K75 Tamiya
« Reply #9 on: December 01, 2007, 06:14:57 PM »
id build a 6 cell subc pack. preferably about 3000mah, so you can have some sort of runtime. go to
www.cheapbatterypacks.com and build one. its not that expencive, and they will custom make you any pack you want!

#### s80ts0465

• Jr. Member
• Posts: 28
##### Re: Gear Head Motor 380K75 Tamiya
« Reply #10 on: December 02, 2007, 06:46:15 AM »
great website. I've made my own battery pack and i should pay 68\$ for a 12V 4500mAh battery pack. pretty well.

#### airman00

• Contest Winner
• Supreme Robot
• Posts: 3,653
• narobo.com
##### Re: Gear Head Motor 380K75 Tamiya
« Reply #11 on: December 02, 2007, 06:59:41 AM »
Why not just get lead rechargeable batteries for half the price on ebay?

A 12V 5ah lead battery costs very little - you should probably even get a 10ah one

for example heres one
http://www.altex.com/product_info.php?products_id=6964

But i would suggest buying it on ebay - much much cheaper - remember to get a charger
Check out the Roboduino, Arduino-compatible board!

www.Narobo.com

• Supreme Robot
• Posts: 11,653
##### Re: Gear Head Motor 380K75 Tamiya
« Reply #12 on: December 02, 2007, 09:52:20 AM »
Quote
and which type of batteries do they have ?!?!!?!?!?!??!

Brand new 10Ah NiMH for under \$62:
http://www.onlybatterypacks.com/showitem.asp?ItemID=10954.8

#### s80ts0465

• Jr. Member
• Posts: 28
##### Re: Gear Head Motor 380K75 Tamiya
« Reply #13 on: December 02, 2007, 02:35:29 PM »
isn't the NiMh better than the NicaD due to the memory issue??
anyway i've finally decide fot the IG32 motor, considering the lower current consumption so i need a 12V battery pack.

For the site you (Admin) suggested me i've found this great battery pack:
12V 10000mAh for only 110\$ http://www.onlybatterypacks.com/showitem.asp?ItemID=11074.37

x airman00:
I also thought about the lead acid battery, but i forgot about them due to the not enought high nomial current that they can release.

• Supreme Robot
• Posts: 11,653
##### Re: Gear Head Motor 380K75 Tamiya
« Reply #14 on: December 02, 2007, 03:12:48 PM »
Quote
isn't the NiMh better than the NicaD due to the memory issue??
battlebots don't survive long enough to care about memory issues . . . plus, the batteries only need to last for maybe 20 minutes. its easy to drain the batteries fully before recharge to avoid the memory issue.

• Jr. Member
• Posts: 28