Grade of alu for axe?

**Graw** · 6th August 2016, 17:46

Hey lads,

Basically im putting together a new feather and was looking around at my options for the arm and head of my axe/hammer. Ti is a bit out of my price range so the next best thing for me would be aluminum, currently I've got most of my parts sourced but im a bit unsure what grade of alu to use for the arm and head of my weapon. I assume theres not alot of difference between them but I thought I'd get some opinions from people who'd know lol.

For what I have in mind im going for around a 1.5kg hammer head machined from a solid block of alu and a nice machined arm to keep the weight down where I can, so I guess im looking for one of the easily machined grades? I know the energy transferred through a pneumatic axe is far lower than what goes through some of these spinners nowadays so I'd assume the strength of each grade shouldnt be a issue and the finish isnt really important im more worried about the ease of working with the stuff.

Thanks in advance

**Eventorizon** · 6th August 2016, 18:05

6082-T6 is easy to get hold of, easy to machine but a little on the soft side. 7075-T6 is stronger, harder but is harder to machine. I'd go 7075 for the arm, 6082 for the head.

Avoid 1050 and 5021/5083, those are cheese grade, and 2014 is more for cold forming as its pretty malleable. There is also 'Eco' aluminium out there. Great for the environment... not so good for robots.

**Graw** · 6th August 2016, 18:29

So the strength does tend to vary quite a bit then? I did do a quick google search earlier and read that some grades are 20% or more stronger than others which suprised me. I'll look into those 2 you suggested, are there any particular suppliers that you guys use?

**mrsam** · 7th August 2016, 08:53

Why not go for a full hardox axe arm? I'm doing something similar, a one piece axe watercut from 8mm hardox with cutouts in the arm to keep the weight down and a solid head. Nice and cheap if you know where to go.

Screenshot 2016-07-18 15.41.14.png

**Graw** · 7th August 2016, 10:36

That looks good mate. I was going for alu mainly because of weight, the hammer head is basically going to be a solid block of alu with a pyramid shape at the top (wish I was decent with CAD so I could put pics up) and im planning for the base of the head the be level with the floor of the arena. I thought since im going to need alu for the size of the head (hardox would be way too heavy) I might as well use alu for the arm as well.

I will have a look around from some prices of hardox though, maybe if it works out cheaper than the alu would be I might go for it.

**Eventorizon** · 7th August 2016, 11:15

It depends what you want, both will work just fine. Hardox is the easier and probably cheaper option in the long run and will be more durable. but the Alu weapon would look cooler. Its up to you. The Alu wont be able to puncture any armour but it will allow you to bludgeon repeatedly, where as you can get a sharp Hardox weapon and look to be making holes in your opponent.

While this is more based on the power of the weapons it will give you an idea - Killer joule has an Alu arm and Alu head and hits like a beast, so much so it was able to OOTA itself! Hatchet has a Hardox axe and is able to make dents in Titanium. Our own axe, Mattock, has a 3Lb mattock mini pick axe and that will go through 10mm of HDPE and crack Ti.

**Graw** · 7th August 2016, 11:56

I was considering interchangable heads, so I could have the bludgeoning hammer made up from alu and a more THZ shaped axe head made up from hardox (I could use a nice thick piece of hardox since the alu head will weigh around 1.5kg I'll have that much weight to play with). It would be decent that I could change them around as per which is more suitable for who im up against.

You're right about the alu looking cooler, I've seen killer joule and tbh its one of my main inspirations behind my build - such a cool machine. Does the pick axe shape end up getting stuck in armour alot? Going through 10mm of HDPE is pretty impressive, got any pics of the robot?

Edit : http://www.ebay.co.uk/itm/10mm-RAEX-...5a1e-NLMfLDPNA

Good grade for what I need?

**Andy** · 7th August 2016, 12:11

Instead of buying the material then sending it off to be cut, a lot of people use a place called Kcut which will supply and watercut the material to your designs, i reckon it'll definitely be cheaper this way.