From The Ground Up (Advice Thread)

[Roland]

Re: From The Ground Up (Advice Thread)

Sorry for the bump.
Finished the workshop today, got my vice in, drill press and wall grinder, not too shabby!
I can't seem to find any hardox sellers on ebay or commercially, where ought I be looking, or should I just use mild steel?

I'm going to go right out there and say I don't understand motors, I can't find a decent resource to teach me about them either.
All I think I know is that the higher the current on a motor the quicker it runs down a battery. Other than that I know nothing.
Learning process I suppose, so if any of you could give me a quick lesson on working out torque, the benefits for gearboxes on motors and voltage's effect on batteries I'd be in debt to you, if not that if any of you know some resources I could use that would be brilliant. I have looked at the riobotz tutorial extensively but some of it's extremely advanced for me. Even so it has been ridiculously helpful, thanks for posting that!

Thanks again! Sorry for all the trouble.

[jonny]

Re: From The Ground Up (Advice Thread)

for hardox you can get it from jl steel, mtl steel, direct from ssab or from a private seller ie someone on the forum. i've bought some hardox off gary recently, not sure if he still has any though.

[woody]

Re: From The Ground Up (Advice Thread)

http://www.societyofrobots.com/actuators_dcmotors.shtml
http://www.micromo.com/dc-motor-tutorials.aspx


http://architeuthis-dux.org/torquecalc.asp

[Roland]

Re: From The Ground Up (Advice Thread)

Wow! You're very quick, thanks a bunch to both of you. I'm rather ill today so I'll get reading right away!

[Roland]

Re: From The Ground Up (Advice Thread)

I've been doing some cad work using google sketchup, and my design so far looks like this:

http://img854.imageshack.us/img854/7513/picture1lt.png

It looks rather sparse, simply because I have two problems, assuming I use graupner speed 900s I'm not sure what batteries would be the most efficient to use, plus that and the set up, parallel or series?

My other idea was to attach a belt to the front and back wheels so that if a motor died out the remaining motor would still run both wheels. This came from the idea of having only two motors to save cost and weight but I'm not sure if that would really benefit my rammer design. Any advice would be brilliant. Sorry I'm such a bug.

[Roland]

Re: From The Ground Up (Advice Thread)

Sorry for the bump but I can no longer edit my post, I don't think I'll use Speed 900s because I can't find any info on operating and stall torque and I don't want to buy something that expensive not knowing what it'll do. Hmm.

My main dilemma really is that I'm new, but I don't want to design a bot that chundles around the arena and just stops when it hits stuff. But I can't over complicate this thing because I have absolutely no robot building know how.

How do drill motors compare to the motors manufactured for model boats etc? I'm not even sure what motor I want because the only ones I can find don't tell me what there operational torque and stall torque are, and places like technobots I don't even know what I should be looking at.
The tutorials are helpful, but without certain background knowledge on things like motors batteries, what sort of esc I'd need and what sort of speed controller I'd need I'm dead in the water. And it's annoying because I've only just realised. It's probably down to that I'm not looking hard enough but I don't even know where to start since half of this stuff makes no sense to me at all.

[Anttazz]

Re: From The Ground Up (Advice Thread)

If its your first robot why not just use the nice simple drill motors and gearboxes? 6 of them will give you a fair bit of power with less hastle and also will be a lot cheaper than buying speed 900's. 4 speed 900's would cost something like £120-160 (not having looked at prices recently) whereas 6 Argos drills will cost you £60 and you wouldn't need to worry about adding in extra gears or anything like that, just whack them on to a set of Robochallenge wheels and you're away.

[harry hills]

Re: From The Ground Up (Advice Thread)

and that esc and speed controler are the same thing :P

[Roland]

Re: From The Ground Up (Advice Thread)

I see your point, like I have said, money isn't a problem and going simple to start is advised (4 graupners = around 170 assuming vat hasn't been added to the 36.99 current price) , but I'd rather make something worthwhile, something that does it's job. After watching a lot of videos online I've noticed how robots tend to sacrifice one thing for a strength in another. The idea with mine was since I'm only doing a rammer, the motors needed to be powerful but I don't need to worry about weapons and I'm a perfectionist, I hate doing things and finding out they don't work, so I never do anything without guidance first. Which probably isn't very good, but there you go!

Did I write that twice? Urghh... It's 10 to 9 and I'm extremely ill, it's there fault, blame it on the illness. :shock:

And would 6 drill motors end up costing quite a bit since I'd need an extra esc plus fan?

[gizz]

Re: From The Ground Up (Advice Thread)

I'd have a go with the 6 drill motors in this case and the 100£ ur saving compared to graupners would come in handy when it comes to buying the ESC

[Anttazz]

Re: From The Ground Up (Advice Thread)

Drill motors I reckon are fairly well proven, i'll be using them in a rambot at the UK champs and i'm sure i'm not the only one. The likes of Drumroll I know for certain is using drill motors too and there are many, many others. It doesn't seem like you would be making the machine much better for the hours of work that you would have to do compared to just sticking in a drill motor. Even finding somewhere that sells 18V drill motors or higher would be a more expensive option, but would give you the option of using voltages maybe as high as 25-30V? You would possibly need an extra esc, depending on the esc you are using now. But you would save on have to get hold of gears etc as the gearboxes will be included. If you definitely want it to work, do what has been proven to work

[jonny]

Re: From The Ground Up (Advice Thread)

http://www.clifford-james.co.uk/online. ... iate=8,381

the cheapest 18v drills i could find

[Anttazz]

Re: From The Ground Up (Advice Thread)

Ohh, never noticed that before, that will be a good source of motors for me in the future too, cheers Jonny

[Roland]

Re: From The Ground Up (Advice Thread)

Hmm, I see I understand that many robots do have drill motors, but then drumroll isn't a rammer, it's main weapon is a teethed drum, so pushing power isn't as important.
Is Tiny Toon not a rammer? What motors does it run on? Do the majority of the successful rammers work on drill motors? Hmm. I've also heard that with a six wheeled bot you getter better performance from leaving the middle wheel free rolling, is this true? Thanks for all your help so far guys. Sorry I can be such a stubborn toad.

Those drills come with a carrying case, what would I do with 6 carrying cases! Answer me that and you'll have changed my mind about drill motors.

[RogueTwoRobots]

Re: From The Ground Up (Advice Thread)

Hey Roland,

A lot of comments supporting the use of drill motors instead, and I agree that for a first robot, they are a very good and proven way to go. However Speed 900s are also very good motors and if money isn't a problem and you can go for a decent set of machined gearboxes and transmission, then they will also serve you well.

You talk about having four motors and connecting all the wheels so that if one motor fails the other one can still drive all the wheels. In my opinion, that's a bit overkill. Yes it provides a level of back-up/redundancy and therefore improves reliability, but it's a bit of a waste of weight in a featherweight. Speed 900s weigh roughly 650g so 1.35kg for two, plus extra weight in gears and gearbox housings (could be almost 20% of the max weight); it's a lot of unnecessary weight that could be used to beef up the chassis or armour of your robot. Speed 900s are also incredibly reliable motors from my experience so there shouldn't be much to worry about in terms of motor failure (famous last words though )

If you go for them, I'd recommend a Speed 900/gearbox combo directly driving one wheel on each side, and then slave the other four wheels with timing belts and pulleys. A drill motor pusher is a perfectly fine robot, but you will get a much better, faster, more powerful performance from the Speed 900 arrangement.

I'm a perfectionist, I hate doing things and finding out they don't work

I consider myself a bit of a perfectionist too, but in this hobby, you'll find yourself doing a lot of things that end up not working. Learning from them and improving upon them is part of the fun and part of the challenge