Hatchet 2

[mrsam]

I couldn't be bothered to trawl back through to find the original thread for hatchet so here's a brand new spiffy one for you. Decided i may as well build a new hatchet and at least try and get it to the champs this year if it gets picked, with that in mind i've taken a good month or so of design time trying to keep what was good and discard the rest. The only real thing that i've kept the same is the axe and scoop set up, the shape is roughly the same with a few improvements (nicer looking bulkheads, better weight distribution/wheel placement and a slightly bigger chassis). the new body is now 20mm thick Hdpe with a 10mm base seeing as i got a really good deal on some offcuts that i just couldn't say no to. I don't want to overload you all with information at this point so here's a couple of teaser pics to make the reading worthwhile.
and yes.......it's white now... big whoop you want a fight about it?

[mrsam]

Cut all of the panels out for the new Hatchet this morning, i still have to do the baseplate but i've had enough of getting covered in swarf for today. I quite like it in white although i'm not sure i'll keep the pointy bits at the top of the bulkheads.

[daveimi]

Where did you find chopping boards that thick lol

Looks good

[mrsam]

Cheers David, it's not chopping boards it's proper hdpe from direct plastics. Chopping boards tend to be ldpe which shatters when it gets impacted.

[mrsam]

Cut out the baseplate for Hatchet today, by hand...which sucked, it's 10mm Hdpe this year instead of the 10mm Polycarb which, well let's say it didn't work and leave it at that shall we? (Mr mangle come at me bro). If you noticed the gaping ground cleance around the sides and front it's supposed to be like that..honest, the front part will be covered by the scoop and around the sides i'm hoping that if one side gets lifted up the wheel stays on the ground, that's the plan anyway. Also ditching the chain and sprockets for T10 timing pulleys and belts, the theory being that the belts are stronger and less stretchy/likely to jump off, i'm hoping by using such a large tooth pitch that there isn't a whole lot of slip.

[daveimi]

I was only kidding about the chopping board, and this is really impressive, I keep checking back to see if you've done any more. Electric axes are the most interesting robots to me as the pneumatic stuff goes over my head so it's nice seeing lecky stuff as it's within reach lol.

[mrsam]

Ah okay lol wasn't sure, cheers too, it's certainly not the most advanced robot around but it should be a massive improvement on last years Hatchet. I like to think I've ironed out most of the flaws and should end up with a machine that is at least slightly competitive.

[grant_ploughbot]

What are the full specs of the axe? Length, head weight, motor, ratio etc?

Would be interesting to see what it's like in comparison to others

[mrsam]

Alex still has the original but from memory the axe was around 400mm and weighed around 1.5kg, the head is 6mm Hardox 450. As for the power specs it's going to be run by a 300w scooter motor at 6s on a 3.3:1 reduction. Last year it was a 3.5:1 reduction on 16.8v NIMH so it should pack a much bigger punch this time around.

[daveimi]

Did you find it hard to get a timing pulley setup that worked with your existing motor output and axe drive shaft and stuff? Oh...sorry for being a pain...which esc are you using for the scooter motor?

[mrsam]

No need to apologise, you learn by asking. The big pulley I got from Harry at the champs last year, it needs modding to make it fit a 20mm shaft but that won't take too long. The pulley for the scooter motor i'm getting from http://www.beltingonline.com/ and I'll get them to bore out the centre hole to 8mm to fit the output shaft of the motor. I'll be using the same 30a Electronize I used for the axe last year, although I have a 60a victor as a spare.

[mrsam]

Got the drill motors for the drive yesterday and set about hacking them into usable drive motors, I'll include the link for anybody who wants it because they were a great little find. They're bosch psr 18v drills which are usually around £60 brand new and i got them for £12.50 each, granted there's no battery included but if you're only after the motor and gearbox it's no problem. A couple of things i've discovered about them, firstly they don't have all metal gears which although annoying isn't too much of a problem, they are really compact..like stupidly compact and the output shaft is tiny which means it's very unlikely to bend. The motors are 600 sized Johnsons rather than your standard cheapo chinese 550 which considering the price is even better, also the build quality seems pretty solid, better than standard drills anyway. Some bad points though, the GB and motor are not attached yet the holes to mount the motors are there, it's like they forgot to put the screws in.....weird right? Also the chucks are on TIGHT, after some advice and a fair bit of head scratching i figured out a pretty fool proof way of removing them, you take the gearbox apart and get a round piece of steel in some pliers and wedge that in between the pins on the carrier plate, then you put a fairly big allen key in the chuck and twist the two in opposite directions, takes a fair bit of force but it does get the chucks off. Wow i just wrote a whole essay on my drive motors, anyway for any that are interested here's the link http://www.ebay.co.uk/itm/331196477100

And some pictures

[Shakey]

Those look pretty good for drive! I'll be interested to see how they run.

[mrsam]

Starting bolting the body together today, i forgot how much tapping into Hdpe sucks. I managed to duff up on of the holes for one side panel so i'll have to remake that. Other than that everything is straight and the whole chassis just seems so much stronger this time around, I've also brought a piece of 5mm 6082 Alu to brace the rear corners with seeing as how the 3mm cheese grade i used last year held up so well. If all goes to plan i should have a completed chassis by early next week.

[daveimi]

That looks really neat and tidy, almost machined. I have aspergers with duff motor skills so shake like hell doing anything like this, being that neat is only something i can dream of.