My hammer bot.

Hello all. After the question about the bar or disc I decided to go off and build a hammer bot:). I have already started. I have a lot of questions for people. The first one. I plan to make it a full pressure cylindar on co2. Is this a good idea for a FW. Also I plan to use the rack and cog system in which the cylindar is attached to a rack and that is lined up with the cog which has the axe welded to it. My measurements say that will offer 1.32 times the velocity and it will get up to speed faster. Again: is this a good idea? Thirdly I plan for the hammer to only be drawn back about 100 degrees from the ground. Is this a good idea or shall I pull it all the way back. Last question. Hammer or sharp thingy.

Thanks all:)

Rob

Well the more axe robots the better :). The rack & pinion is exactly what we use, got the idea from THz (copying is the best form of flattery), Think Basher uses the same. The main difference from yours is that the rack is cut directly into piston of the ram saving weight and space. Ours swings 180 degrees but the draw back was when fighting a spinner and it caused the axe head to go flying when it hit, its up to you really to what fits your design best.

A sharpe round point is never a good idea as it easily gets stuck into things. Ours is a sharpe wedge shape.

We use low pressure (around 100psi) and basher is full pressure so both work fine.

axes rule

trying to get my dad to build one

we need more

A F.P. Double acting cylinder is an ambitious project and finding suitable valving is going to be difficult.

The reason Im not using a 180 degree arc is because I want to substitute a bit of power for high strike rate (a bit like deadblow).
If I use a low pressure cylindar will I lose any power (because LP is definately cheaper).

Thanks guys,

Rob

These pneumatic equations might help.

Energy = Force x Distance
Force = Pressure x Area
Distance = Volume / Area
Energy = Pressure x Volume
( psig x cu-in = in-lbs )

Power = Energy / Time
Power = Pressure x Volume / Time
( Units = in-lbs )
Flow rate = Volume / Time
Power = Pressure x Flow rate
( Psig x cu-in/sec = in-lbs/sec )

Probably the easiest method for your first axe bot is to copy an existing succesfull system.

Thanks mate

Rob

Basher is also Low pressure (runs around 12Bar), just with very high flow rate. If you can get enough flow rate into your axe to give it a good speed before it hits your oponent then only returning to 100degrees would be better as you wont get the initail jumping effect that basher gets at the moment.

Thanks for the advice. Is basher competing in any of the major events yet? And also do you think I should use high pressure or low pressure?

(Message edited by touchwood on February 10, 2008)

i think basher competed in euro champs last year

A low pressure system for an axe is simpler to work out and an can be improved by increasing the flow rate at a later date as Grant pointed out. It can be done but a HP axe would require heavier valves, so in a feather would be much harder.

KK maybe ill swith to LP

thanks

Rob

Hi, i agree with sticking to LP. Its hard enough keeping Basher! on the ground running at 12bar and FP would be too heavy. BTW getting the rack cut in to the piston is definately the lightest way

O.K. Do you know where I can buy LP reasonably cheap? And do I want to be looking for 50*50? or smaller? ANd how do I cut a rack into the piston? Do you anyone who could do it for me cheap?

Sorry to bombard you with questions!

Thanks

Rob

Buying new LP for cheap, forget it, unless its ancient cast iron Sovjet stuff.
Ebay is one option.

Some roboteers have/had a small supply of lp stuff. But nine is really gone now? I maybe have a valve or 2 left, and a tiny piston somewere. But thats about it.

A 50*50 ram is way to small. A 50*100 is usefull.

Cutting a round rack involves a precision mill, the right cutter and a lathe to finish it off. Meaning an experienced machinist and machine shop. At this time, machine shops dont come cheap. They all have enough work.

I solved the rack for the FP heavy axe I did build by buying a mod 3 round rack and build the ram around that part.

If I would do a rebuild of a 50*100 ram I would buy a mod 2 rack and replace the original rod with that. ( mod 2 because the rod is 20mm, and that wont be to far off for a 50mm bore lp ram)

O.K thanks very much.

Rob

Im doing what Mario suggests, only MOD 1.5 ram as my seals are 16mm not 20mm, again it is a 50*100 ram.

16mm, strange, my 40mm ram has a rod of 16mm. I would have expected a 20mm on the 50mm bore version. But its perfectly possible that a 20 or 25mm rod is used on the next size of rams above 50mm, the 63mm bore.

But then, I dont have any problems adapting that.

i built an axe robot out of ply wood as a template to make a stronger one at a later date and here it is
http://uk.youtube.com/watch?v=qWF-iHJ8u2Aaxe

robot- looks good

mario - eds not using a normal shape piston i dont think, but why would u want to adapt it?

I ment that I dont have any problems adapting the rack to the ram or visa versa. Just that I have to buy the rack to fit the piston or visa versa

What gearing are you using between the motor and the axe? How heavy will the axe be when its finished?