Starting Point

[zoll]

Re: Starting Point

Team xtreme sorted me out with a couple from a job he was doing not sure he will have any more though im affriad ><

[xtreme]

Re: Starting Point

Ill see what I can find for you.

[zoll]

Re: Starting Point

If not these might do?

[elobire]

Re: Starting Point

ok thanks.
i was thinking about using the centre of a bike wheel, the only concern i had about that is that i would need to weld a plate to it to bolt the axe on too.
EDIT: searched around, and found someone who sold some cheaper ones.
http://shop.ebay.co.uk/webtradersonline ... 581&_pgn=2

[zoll]

Re: Starting Point

elobire, can I ask what welder you have and how your getting on with it as I'm looking to buy one. Think ive decided on a mig not sure what model though

[elobire]

Re: Starting Point

i have a gassless mig welder, it was about £120. i dont really know the make/model, but i can find out tommorow.
im not doing too well with it anyway, all i can produce at the moment are messly welds which cant hold together well. im still getting used to it though, as i havnt used a welder before.

[zoll]

Re: Starting Point

Exams finally out the way back on with some building...

Dont like the chain setup so am going for a gear reduction using the following parts from technobots
Steel Spur Gear MOD 1.5 12 Tooth - Part No: 4715-012
Tbot Steel Spur Gear MOD 1.5 60 Tooth - Part No: 4715-060
Tbot Steel Spur Gear MOD 1.5 12 Tooth - Part No: 4715-012
Steel Spur Gear MOD 1.5 36 Tooth - Part No: 4715-036
which i believe will give me a 15:1 reduction?

How easy would it be attach this motor to this gear? I think the shaft diameter is 8mm as is the bore in the gear so would i just be able to screw it straight on or is it not that simple?

[RogueTwoRobots]

Re: Starting Point

In theory, it should be that simple. With an 8mm shaft and an 8mm bore, you could just slide it onto the shaft of the motor and secure it using a couple of grub screws drilled and tapped through the boss so that they're pressing onto the shaft of the motor when tightened.

That would hold it on but whether it would be enough to keep it there, with the forces that would be going through the axe mechanism, I cannot say (although hopefully someone else can)

[zoll]

Re: Starting Point

Yeah was thinking that also thought about getting someone to put a touch of weld on the end.

Also can anyone see any problems with that combination of gears?

[Metal Demons]

Re: Starting Point

You might want to think about some bigger gears - mod 2 or 2.5, ideally the biggest you can fit in within reason. 1.5 isn't terribly strong when you're considering that you'll be violently stalling the system, possibly reversing direction while moving the axe at high speed if you mess up a bit with the timing, that kind of thing. You might end up breaking a tooth.

On an 8mm shaft, you may get away with grubscrews and red (the strongest) loctite, but you'd be better off with a keyway in the shaft and gear (might be a bit small for that) and a machine key, shaft and gear with a flat side to the hole / hex shaft and hub / whatever, or another method of torque transfer. Grubscrews shouldn't be used to transfer significant torque, that's not their job.

[zoll]

Re: Starting Point

Thanks where can I find mod2.5 they only go up to mod 2 on technobots?

Edit: or do you think mod 2 is sufficient?

[Metal Demons]

Re: Starting Point

To work this out properly I'd need proper specs on the motor concerned, a scale drawing of the whole system, and to do the maths properly, which honestly I can't be bothered to do

Rule of thumbing it, mod2 would easily work if the gears aren't pot-metal, I have no idea on the specs of these so can't say but they probably are fine and if they don't you can get some better gears from somewhere like ondrives.com (expensive though!).

Best bet though is to go for the chain drive! The reason why is that to get gearing to work properly you need to work fairly accurately, significantly better than +/-1mm, whereas you have a bit more leeway with chains - as (I'm assuming given that you're using wood and such like) you don't have access to accurate machine tools it'll be a bit of a pain to do the mechanism right. A chain drive reduction is a lot less finicky about clearances and everything being dead straight. In addition, unless your structure is extremely rigid (and therefore heavy and/or hard to make; a milled aluminium gearbox setup would be your best bet here), if it gets tweaked during a fight, say if you get hit hard, your gears will probably bind up.

Alternatively, there's the expensive way of doing things, which is designing the mechanism, accurately drawing it up (CAD is an option here), and getting it made at a machine shop.

[zoll]

Re: Starting Point

Cool, I currently have it runing on chain and sprocket at the moment, was looking for a little bit more of a reduction then i can get with this and also, this may sound silly but a more refined sophisticated way of doing it.

If I was going to do it this way I would look to mount it between two Nylon 6 bulk heads, so hopefully a bit more of a refined method than wood!

[Metal Demons]

Re: Starting Point

Cool, I currently have it runing on chain and sprocket at the moment, was looking for a little bit more of a reduction then i can get with this and also, this may sound silly but a more refined sophisticated way of doing it.

If I was going to do it this way I would look to mount it between two Nylon 6 bulk heads, so hopefully a bit more of a refined method than wood!

Just choose different sized sprockets to get your reduction the way you want it!

As for refined methods, for now I'd recommend getting something working reliably. Nylon is a good material, but really not stiff enough to hold a gear train in alignment - you'd be wanting to make the structure for that by milling it out of aluminium most likely. Save that kind of thing till you have access to decent machine tools, or the money to get parts made, or both

Just trying to save you some trouble, that's all Pretty engineering is all very well, but if you end up with a mechanism that jams up or doesn't mesh properly the effort is rather wasted.

[zoll]

Re: Starting Point

Ok thanks for the advice . I may post this in the wanted section but is there anyone out there who could mill me some kinda gear box for my creation for around the £200 mark or is this way too little?