Direct motor drive

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Andrew Cowan (Cowana)
Member
Username: Cowana

Post Number: 3
Registered: 5-2008
Posted on Thursday, May 15, 2008 - 10:52 am:    Edit Post    Move Post (Moderator/Admin Only)

Forget that - I've decided direct drive won't work. (Can an admin delete that above message?

New question:

I want to build a robot weighing about 30lbs. I want to use your 100mm tyres, but I have no idea on what power to use. 24V would be good - but what motors? I think a chain drive sounds easiest. Also, does 40x40cm seem a good size for a robot carrying 2 motors and two batteries? The front wheel will be a ball or castor. I would make the chassis out of your 3mm aluminium sheet. Also, I want it to go as fast as possible. 15mph minimum, but the faster the better. Would 25mph be possible?

Thanks for your help,

Andrew Cowan

email: cowanaATgmail.com (remove the AT)
Admin (Admin)
Board Administrator
Username: Admin

Post Number: 790
Registered: 10-2004
Posted on Saturday, May 17, 2008 - 12:38 pm:    Edit Post    Move Post (Moderator/Admin Only)

Andrew,

You did not mention what the application is and whether you need torque for pushing or hill climbing / rough terrain. Speed is not too much of a problem but the power also depends on the acceleration required. A rule of thumb is 15W / kg but this can be increased or decreased depending on the robot duty. This would work out at a pair of 100W motors for your 30lb robot. As for physical size, again what is the application?
Andrew Cowan (Cowana)
Member
Username: Cowana

Post Number: 5
Registered: 5-2008
Posted on Saturday, May 17, 2008 - 2:13 pm:    Edit Post    Move Post (Moderator/Admin Only)

Thanks for the information you gave me over the phone. I am now looking at using:

24V 200W motor
1.6 : 1 gearing
100mm wheels

(For flat ground, no pushing). The calculator gives a speed of about 25mph. What is the shaft diameter on the 24V 200W MY6812L - Part No: 1470-014 motor? Do you think this idea should work?

I am not quite sure of the weight of the robot yet, but it will be between 10 and 20 kg.

Andrew
Andrew Cowan (Cowana)
Member
Username: Cowana

Post Number: 6
Registered: 5-2008
Posted on Sunday, May 18, 2008 - 12:19 pm:    Edit Post    Move Post (Moderator/Admin Only)

Also, can the hole on the 100mm EMG30 wheel be enlarged to 8mm? What is the diameter of the hole in the plastic rim if the aluminum hub is removed? Lastly, how can I fix a 16 tooth 6mm sprocket to a shaft? With a grub screw?

Thanks again,

Andrew
Admin (Admin)
Board Administrator
Username: Admin

Post Number: 794
Registered: 10-2004
Posted on Monday, May 19, 2008 - 9:35 pm:    Edit Post    Move Post (Moderator/Admin Only)

Andrew,

In summary, you intend to use a pair of 200W motors giving 20W/kg worse case. It is very likely your idea will work.

The EMG30 cannot be enlarged, not even 0.5mm which is a shame as we would like to offer them for 6mm bore as well. We do not have the dimensions of the hole but would guess it is 6 or maybe 7mm.

Most of our customers drill and tap a hole for a grub screw fixing.

Regards

Paul