New Build/CAD Advice request.

[maddox10]

Stall , not happening a lot as long the drive stays whole. (and is geared sensibly)
You can't get that power to the floor with the weight and tyres we use.

[BrentwoodSchoolRoboteers]

As a school we have a tight budget - Expulsion was built with £1000 but then we were given the £500 by the BBC. It was difficult. Our steel was cut for a fraction of the cost it should have been (£320). Two main things that stand out.

Don't underestimate the cost of little things. Heavy duty cables, crimps, fuses, nuts, bolts, removable link, chains, gears, sprockets. All adds up.

Put it this way. This is £100 worth of stuff: 2 Chains, 2 Sprockets, fuses and fuse holder, 1m Cable red and black, nuts and bolts, Cable ties, Bearings.

Then factor in the fact you need spares of every component. I would go on eBay and add every single little component to your basket then look at the figure.

[Lostdreamer]

Stall , not happening a lot as long the drive stays whole. (and is geared sensibly)
You can't get that power to the floor with the weight and tyres we use.

Ahha.

That makes some sense.

Hence seeing people swapping out so many fried motors etc on TV. It's not just people running them overvoltage and outside spec. If a wheel jams then you DO get stall currents, which DO fry the electrics.

Would I be correct in assuming people deliberately don't insert a big fuse to protect the motors in the event of a jam because then you are actually introducing failure mechanisms?

But it also means that I don't necessarily need to find 300A worth of control hardware, batteries etc for something like a cordless drill motor.

And yup, lot's of window shopping ebay doing a back-of-an-envelope pricing etc. I'm building a rapidly growing spreadsheet with lists of how much all sorts of things cost. I think it is possible, but I also think that typhoon_driver was bang on the money when he said right at the start it would be borderline competetive. That cost constraint means I can't bring the same levels of performance / power to the party that a lot of other people do. I would be basically building a target.

It's nice to know that Explulsion was built for a similar budget. And it's nice to know that £1.5k target budget actually does include a lot of the little stuff like fixings and wiring that it's so easy to cost at nothing because 'I just had it laying about'.

If I am creative in my sourcing of parts and start shopping at my local scrapyard rather than ebay, it should be possible. Canibalising mobility scooters seems to be popular for example. I'd be be making way more work for myself than I would like and in danger of missing my 'KISS and use off the shelf bits' objective but I guess that is secondary to the 'can I do it at all?' issue.

So now I have another silly question. Said spreadsheet is giving me an idea of how much some of my costs will add up. It's also making it clear how quickly weight is going to add up. So, err, exactly how big length/width/height are many of the robots? How much can I realistically expect the shell to weigh?