FeatherWeight on a budget.

[Metal Demons]

Re: FeatherWeight on a budget.

Rule of thumb for overvolting a fairly hot wound dc motor like a drill is 1.5x rated voltage so you'd be looking at 18v.

[typhoon_driver]

Re: FeatherWeight on a budget.

the travel won't be much however that's irrelevant. It's all down to the current that the motor will draw. As you will have a lot of start and stops, the motors are in essence stalled for a fair bit of time, hence drawing large currents. 1.5 times the voltage will leave your drill motors too warm to touch after a battle. Believe me, I've touched them

No it's not ok to use a 12v drill battery charger to charge an 18v pack. Buy a decent and scrap the drill one. It's junk

[PJ-27]

Re: FeatherWeight on a budget.

ok, we plan on getting some decent cells at some point, 2-3 charge isn't going to be manageable! Are chargers voltage dependent? Would I need an 18v charger specifically? Just thinking the voltage of the packs may get modified at some point until we find whats best.

[typhoon_driver]

Re: FeatherWeight on a budget.

As you will see with the example here

http://www.technobotsonline.com/pro-pea ... arger.html

All decent chargers will tell you that they can charge up to a certain number of cells. Basically they are intelligent chargers, able to tell the number of cells being charged and hence they are able to charge and then automatically stop. You will find a lot of intelligent chargers require the use of a 12v power supply input. You will therefore require an external power supply to plug the charger into. There are some that plug straight into the wall but I'm not familiar with those specifically (been a while since i've had to buy a new charger!).

[PJ-27]

Re: FeatherWeight on a budget.

There a little pricey, what about just for testing? And then in the future we will look to buy new cells and chargers. The chargers for the drills would effectively being charging 7-8 cells instead of the 10 they were before. Just want to get some juice in them.

[typhoon_driver]

Re: FeatherWeight on a budget.

why bother shelling out twice then? Buy a decent charger now and you save yourself the hastle of spending more cash in the long run. Don't get me wrong, I realise you are trying to build on a budget, but if you are planning to be building bots for the long run then I'd highly recommend buying a decent charger and power supply.

A quick search on ebay threw up this

http://cgi.ebay.co.uk/iMAX-B6-Lipo-NiMH ... 27acfe62c0

Should be able to do the job you're after. When building bots, ebay is your friend!

[PJ-27]

Re: FeatherWeight on a budget.

Thanks for having a search!

Yeh eBay is a great place to fin what you need! May just get that very charger.

Cheers,

[PJ-27]

Re: FeatherWeight on a budget.

Turns out we each have an old Ni-Cad charger each that will charge up to 8.4v, so I'm going to just make up 2 packs and charge them individually.

[psycho_fling]

Re: FeatherWeight on a budget.

Hi

i've got an old charger i no longer need its an intelligent charger with built in wall plug much easier than a power supply

interested >??

[PJ-27]

Re: FeatherWeight on a budget.

PM'ed

[PJ-27]

Re: FeatherWeight on a budget.

I think we are going to muddle on with what we have.

Anyone know what sort of gauge wire I should be using? Should I account for peaks in current?

I don't actually know what sort of wattage I'm looking at for the drill motors.

[Metal Demons]

Re: FeatherWeight on a budget.

Overkill can't hurt, 10 or 12 gauge will be fine.

[PJ-27]

Re: FeatherWeight on a budget.

Is that AWG?

Cheers,

[jonophilpott]

Re: FeatherWeight on a budget.

yes awg

Halfords subwoofer power cable would be sufficient and its very well insulated

[RogueTwoRobots]

Re: FeatherWeight on a budget.

[quote=k_c_r]

What is your preferred way of mounting them? If you don't mind my asking...

It is similar to the Robo Challenge mounts in the sense that I support the motor at the gearbox end. Basically, I tend to use a bulkhead design in my robots so I cut the back-to-back-D shape of the front of the gearbox out of whatever material I'm using for my bulkheads (usually some form of plastic). Usually the depth of the gearbox at that part is 20mm so my bulkhead material either has to be 20mm thick, or if it is thinner, I have to cut the same shape out of a thinner piece of material and use it as a spacer. I then bolt the whole motor in place using the mounting plate supplied with the drill (this is a round black plate, maybe around the 50mm diameter mark with two holes in it that you will see when you remove the chuck from the drill. It holds on the torque ring and you need to unscrew it in order to remove the torque assembly)

I should probably get some decent pictures up of what I mean because I feel I don't quite explain it as clearly as it could be. Essentially though, it is a pretty quick process and I've never had a problem with drill motors mounted in this fashion.[/quote:1ldlr8r3]
Photo time

This is the cutout I make in my chassis bulkhead to accommodate the front end of the drill gearbox. I used to make the back-to-back D shape as mentioned, but now I don't bother. Instead I just cut a rectangle, usually around 30mm x 25mm in size:



This allows the drill motor to slide through the hole and have the shaft protruding on the other side. You can either have it as a tight fit or it can sit loose in it; I usually try to go for a bit of snugness (sorry for the blurry pic):



The depth of the gearbox is roughly 20mm, so spacers may be necessary for thinner bulkheads. For example, here my bulkhead is 15mm thick so I've used a spacer made of 8mm HDPE to take the depth to 22mm. All I did was use a hole saw to cut the spacer out, and then cut the 30mm x 25mm rectangle in that too:



I then put the black metal plate from the drill torque assembly over the spacer and screw it into the holes in the front of the gearbox using the same screws used in the torque assembly. Job done!