Building first FW - Drive system

Hello there. I am new to building featherweight robots.

I have decided to go for the GR02 18V gear motor (http://www.gimsonrobotics.co.uk/GR02...gearmotor.html) to drive my robot.

What I would like to know if there is a better motor choice other than using a cordless drill motor.

The reason I am not using a drill motor is to keep things simple by reducing the number of parts I need to order.

Also in terms of using speed controllers, I was considering using a sabretooth 2x12 but not sure if this is suitable for the motors I have in mind, and I am reluctant to get the 2x25 due to its price tag. So is the ST 2X12 good enough or is there a more suitable speed controller I am not aware of.

Thank you for your help.

Matthew

The GR02 is a good choice - simple to use and full metal gears

Personally I use TZ85a that I hack myself http://www.hobbyking.com/hobbyking/s...arehouse_.html

but you can buy them pre-hacked

http://www.botbitz.com/index.php?rou...&product_id=59

Hiya, as far as I know Gimson's start life as drill motors. I have two of the older GR01's running on a 2x12 Sabertooth and it's been bashing round the house great for 6 months :)

The main gist is that there are ESC's for each motor and you sort mixing out externally, or you can get something that does it all in one box like the Sabertooth. Different setups work better for different people.

I have seen those speed controllers before, however from my understanding I would need two of those as it dose not support mixing.

I know Robo challenge supplies the pre-hacked drill motors, perhaps I might use them as this is my first build, it just means I would have to sort out a bracket for them, since I don't feel the need to speed about £20 on something I can make myself.

Thank you for your help.

You need 2 TZ85A as they only drive a single motor each

The alternative to the GR02's is some cheap and cheerful drill motors from Argos or B&Q
http://www.argos.co.uk/static/Produc...er/7112946.htm
http://www.diy.com/nav/fix/power-too...skuId=11448297

There are a number of posts on the site relating to different mounting methods for drill motors

I run two drill motors in my machine, as do many roboteers. Whilst I have no battle experience (thank you, cheap ebay speed controllers) they seem to run perfectly fine. Team Expat (who are behind the Tormenta series of robots) use 4 drill motors in their robots, they've got a few guides on their Youtube channel (TeamExpat) on how to hack the drill motors yourself - really only takes a screwdriver and some m5 grub screws, then obviously your mounts. You might also need to get some replacement gears as a lot of these come with plastic gears, which obviously aren't the greatest of things and shred quite quickly, but they're easy enough to get a hold of I believe.
The gimsons are great if you want something that's all ready to bolt in, which is definitely what I'll be doing for my next robot because I have no workshop other than the kitchen worktop itself - they are however, more expensive than simply modifying the drills yourself... All depends on your budget, really. There's also ones that you can buy from BaneBots too that have various different ratios for speed/torque or whatever.

I've heard many good things about the TZ85As, too - if you've got the money for them, I really don't think you could go far wrong - I'm fairly sure they're pretty widely used. Again, you can buy the brushless ESCs and hack them yourself if you have the kit to do it and know what you're doing which is a lot cheaper than buying them from BotBitz but it's also more difficult as you could imagine. I've bought some '320A' ones off eBay that are significantly cheaper (mine cost about £26 total compared to nearly £100 it'd cost to get some of the BotBitz ones) and are similar ones to those used in Scruffy and Night Fury, but I think I may have got a different model as mine have a brake function in, and naturally isn't the sort of thing that's preferable in this kind of application...

Long story short, look for something that's forward/reverse, or is programmable to get rid of any brake function- you don't want only forward, and you don't want forward/brake/reverse either because that can be a bit of a pain.

Finally, for batteries, most people run LiPo, I believe, up to about 6s (24V, there abouts) which the BotBitz ones will definitely handle. Motors can definitely be run about the rated voltage, but the general rule is about 1.5x, so if you had the 18v Gimsons, you'd be able to get away with 5s or 6s LiPos, but of course if you had the B&Q/Argos drills then you'd only be able to go for 5s (about 18v) at most, again depending on the speed controllers you go for.

If budgets weren't an issue, I'd personally go for 5s/6s LiPos, some of those BotBitz hacked TZ85As and some 18v Gimson motors, then some of those BaneBots or RoboChallenge wheels too, but there are alternatives.

I'm definitely not an experienced roboteer, but I hope that helps you out a little bit!
And when in doubt, always have a look at the build diaries section, always some great tips to be found there, helped me when designing HardWired!

If you buy stuff pre-done (gimsons/robochallenge and which ever speedo) it goes together like lego. Later on you could mess around with getting argos drills and tapping them etc>?

Thanks for the help. I've been looking up the LiPo batteries to get a better understanding of the esc I may be able to use. I think two of those 320a esc's would be best as I would be running high amps, way higher that the Sabretooth is rated for. Know where I can find and esc without a break, so far I can't seem to find one still looking though.

If they are the ones from eBay, then I doubt that you can run 320 amps through them.

Heavyweight controllers are 120a, those give very false information

2 basic electronize 15a esc's will do drill motors on 12v, I have even ran those controllers on 18v with 25a fuse in place of the stock 15a ones and they ran fine.

There is someone on the forum selling the 30a versions second hand and will do you for 4wd if you decided to go down that route

Well I'm not planning to run 320a through them, just since the rating is high enough so the power I'm running through wont blow it up. The problem I'm finding with these is that I can't find ones without a brake or a feature to turn it off. Also I try to avoid ebay when it comes to electronic devices.

as far as i can tell they dont seem to do the version that doesn't have braking any more, im looking into 2 other suppliers at the moment but will have to wait till i can test them to make sure their the good 1s

They will not be able to handle 320a I can promise you that

i no that but the 1s in night fury handled 2 drills per esc and didn't get warm so they are capable its just the new versions breaking issue that's being a pain

I know, just making new people aware of how some parts can be over spec'd :)

Just a quick update, I have decided to go for the pre-hacked drill motors from the robochallenge store. So right now I just need a speed controller. I am seriously considering the sabretooth 2x12.

For starters it has a mixer built in, so it saves me getting 2 separate speed controllers, and the voltages range input is around
6-24V. So it sounds suitable, given it would only cost me about £50, but if anyone has a more suitable suggestion at around a similar price then please do let me know.

Thank you guys for your input so far.

Unless you have purchased them already, I'd try doing the drills yourself. It's simple. I made a how-to, you can watch that here: http://www.youtube.com/watch?v=OJMoh2C2Hdo

You'll learn a lot, and there is no way to make your next machine better than learning how the insides of your first robot work!

Also, and this is the main reason, RoboChallenge are very busy at the moment, doing TV work. There shop is probably not high on their priority list. I'll let them comment here if this isn't true but I don't think you'll be able to get the drills through them, or at least not quickly.

And considering how much you'll learn with nothing but a screwdriver and some grubscrews I'd say it's worth trying them yourself anyway!

Good luck either way.

Regarding speedos, two of these would cost the same: http://www.botbitz.com/index.php?rou...&product_id=74

I don't know how they do in combat as they're a fairly new product, but their larger cousin, the Botbitz 85a speed controllers, are gems. Cheap, solid, and quite good control. Whilst the Sabertooth will give you good control on two drills, it will never be far from its limits. If I were you I'd go for the 30a Botbitz, but if you can scrape up the cash now you'll save in the long run by getting tz85s. There are few if any featherweight drive systems that they can't handle, whereas the 12a Sabertooth is already struggling at the bottom end of two drills. Unless you get a dud ESC or wire them incorrectly or something the tz85s will last you multiple projects, the 12a Sabertooth most likely won't.

Thank you for the video, I have already seen it before though, personally I would like to get them pre-hacked to save the hassle of getting the separate parts.

But if need be I'll hack them myself. Problem I found is that there is a site which sells the steel gears needed, but I'm not so sure about the number teeth the gears have, is it 15 or 18? The grub screws should be easy enough to find.

Thank you for the advice on the sabretooth, I think I will get those 30A ones since I don't want to be spending about £100 and blowing my budget on the 85A ones. or blowing £50 on a dud.

Thank you for the help, once I get these parts together I can begin to focus on the design.

There is only (apparently) one drill motor/ gearbox left in stock.

Thank you all for your help. I have now decided on what I'm going to use. I've decided to just buy a cheap pair of drills and 30A speedo's from botbitz. Was a bit pricey but not as much as the 85A ones.

Once again thank you all for your help