Andrew,
Have you considered the Zeobot motors that they have at technobots. You can get these with gearboxes already fitted. They work well with the electronizes. I have just finished a 4 wheel drive bot that uses two electronizes (one each side powering two motors each)
Have a look at http://www.technobots.co.uk/en-gb/dept_528.html on the Technobots site or give Paul at Technobots a ring/email.
Ian
yeah i had a look at them, but there nothing like as powerful as the Gold motors are they ?
they arent as powerfull, but they are an easier option and you can always run multiples of them. The max current a 24v gold will pull is 25amps, a 12v one in theory will pull 50amps. You can buy controllers with current limiting but it starts to get expensive then, the easiest way of stopping them stalling is to have it so your wheels spin just before they stall.
are you sure a 12V would pull 50, i though it would be 12.5 coz otherwise a 12v has a heap more resistance than a 24v one and i dont see why that would be.
if it can pull 50Amps doesnt that mean that neither of the h bridges on http://www.technobots.co.uk/en-gb/dept_518.htmlhttp://www.technobots.co.uk/en-gb/dept_518.html would be able to cope with it ?
No, power (W) is equal to the voltage (V) multipled by current (A). If you halve the voltage, you have to double the current to get the same output power. The 12V version of the motor will have a lower resistance to allow more current to flow through it.
In most cases its best to go for the highest voltage you can as its easier to deal with higher voltages than higher currents - up to a point. Over 36V is dangerous and would not comply with the FRA rules.
ah ok i understand now.
so will the h bridges cope with that or will it fry them, i thought they were only rated to around 30 Amps
Just a point on lower power motors. I am more interested in manouverability than pushing power. If you have an effective weapon like Vortexs spinner or a good flipper, the pushing ability is less important.
Do you plan to have a weapon?
Ian
Ian,
I know a couple of girls who would take issue with you about the importance of pushing power!
But seriously Andrew, Ian makes a very valid point regarding the required balance between drive power and manoeuvrability. Also Jim is right when he says its easier to deal with higher voltages than higher currents My personal preference would be to use the 24v gold motor @24v with a reduction of 6:1 and a 100mm dia. wheel.
This would give you a speed of around 12mph with a reasonable amount of torque. As for speed controllers, with this set up you could get away with a pair of Electonize 30A units and a mixer you can get details of these from http://www.technobots.co.uk/http://www.technobots.co.uk/
It may be helpful to you to try to get to one of the many live events held around the country. Make yourself known to the roboteers and Im sure they would be more than happy to show you their machines, you will see most types of drive systems, everything from the Zeobot motors through gold motors right up to 750w Astroflight cobalt magnet drive units. You would probably also be offered more advice that you would know what to do with.
Check out the live events section of this forum and also http://www.roamingrobots.co.ukhttp://www.roamingrobots.co.uk
I hope this is of some help.
Good luck with your robot.
Geoff.
Hey Andrew, why not use standard drill motors for the moment? they are very cheap and easy to use and you get batteries that you can test it on with the drill. Also for the price you would save on buying gold motors and seperate batteries, you could afford four motors!
If you need ANY help with building or designing then Rc Wars/Robo-Challenge will be able to give you help and advise. We build many robots (6kg to 12kg) and have a fleet of just over 15 at the moment and so we would be able to build any components for you if you do not have the facilities. Where abouts do you live? we have facilities for testing your robot aswell if needs be, and supply electronics if you are uncertain of where to get things.
Grant
Andrew, we have got 2 of those 5Amp (without heatsinks) H-Bridge controllers and have fitted them to 2 of our featherweights. They dont have failsafes, but I dont see why as its only a simple change to the software, I did concider re-programming them but found an easier way, but as it stands you would need failsafes, a PCM type Tx & Rx would do but they are more expensive than the standard ones.
As for the Heatsink, my brother came up with the Idea of using a standard PCs CPU heatsink and cutting it in half and bolting them threw the MOSFETS, these heatsinks are very cheep and on one of them he added a small fan too.
We altered them to work with a 0V-2.5V-5V signal to control the motor speed as they were slightly jumpy with the RC servo signal and the steering reverses going backwards, but so far we are happy with them and will test them out in combat at Sheffield.
One is running on 33.6V with 30V drill motors and the other is running on 19.2V with 12V drill motors, both have a 30Amp fuse on the batteries and has not blown them as of yet.
Current rating is a little difficult to figure out, If you have a 200W motor and your Gear ratio and traction can only deliver 100W before the wheels start spinning then it wont use any more then the rest is wastefull. But if it needs 300W of power to start the wheels spinning then your motor will try and deliver 300W and start to overheat, in time it would burn out if overstressed for too long. So its better to have an overrated motor and not use the power to be on the safe side but at the expense of wasted weight.
The lower the voltage you use the higher current needed for the same power output, also high voltage motors are more effeicnt and as they use less current they also generate less heat.
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