Yeah I'd highly recommend getting a charger that can charge at an amp or two. It will become invaluable during events.
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Yeah I'd highly recommend getting a charger that can charge at an amp or two. It will become invaluable during events.
Just the problem that i'd need 4/6 chargers depending how many battery packs i need >< which im guessing would be £100 atleast
What do you think to these http://cgi.ebay.co.uk/Intelligent-1-...item1c0b5a5722
Managed to do a bit of building today, had a few problems... made a test rig for the axe and it just destroyed itself without the full axe even attached, wood ripped of the base... might have to learn to work with metal sooner then i was planning lol
Second problem I'm running a victor 883 as the speed controller for the axe it works fine off 21.6V (3x7.2V) but if i try to run it off 28.8V (4x7.2V) it doesnt come on. The victor is rated up to 30V so I thought 28.8V would be ok but prehaps not?
Try checking the current drawn when the axe fires
For the voltage problem, 28.8V is the nominal voltage of having four 7.2V packs connected up (1.2V per individual cell). When a battery cell is freshly charged though, it can be up to 1.5V so multiplying that by 24 (total number of cells in four 7.2V packs) gives 36V. Even if they only charge to 1.4V each, that's still 33.6V so the chance is that it is too much for the controller.
I assume it goes back to working again if you revert to 21.6V after trying the 28.8V setup? If so, then the controller's probably got an excessive voltage cut-out circuit in it to protect the unit.
Cheers for the tips, I think you are right as the batteries were fully charged. I dont think it was anything to do with current draw as it just didnt come on atall. Think I might just run it off three packs anyway seeing as thats powerfull enough to destroy the rig I made. Would HDPE or Nylon 6 be stronger then wood when the axe tries to rip the screws out as the wood just splits along the grain line, or am i going have to go straight to metal?
Nylon would be able to take it if thick enough but to be honest I much prefer metal and aluminium really isn't that hard to work with. Some basic tools and you're away! I also gotta say if you're gonna have that axe swinging around I think you really should go for metal!
Yeah oki think it might have to be metal then, btw before my rig destroyed it self it swang the full length axe at some fair power, made large hole in some chipboard. What thickness alliminum would you recomend and where am i looking to buy it from?
Anyone any idea how to limit the return speed of return using a DX6 and victor 883 to say 20%?
Sorry to still be boring you all with all my questions but I really do apprieciate all the help you give me. I've remade my little rig for my axe out of slightly stronger wood while i learn how to work with metal and ive notice the gear reduction through just the chain and sprocket that I have on it is really not enough and I some how need to gear it down further to produce more torque. How would I go about making a gear box to go this? Thanks again Matt
to make a gear box you would need gears instead of the chain and sprocket approach (can be done but will be quite large)
usually you would need a 2 stage reduction gear box in order to get to the desired torque or speed
any parameters we can look at as to current spec and the desired figures??
Anyone know what size box section is good for making a frame and where I can get some?
For a featherweight look at 10mm by 10mm or 15mm by 15mm and a mm or two thick steel box section. You can roughly calculate what weight your chassis will be by working out the weight per mm length of box section and then total it up based on how much box section you would use. For a supplier best to look locally. Look in the yellow pages for a steel or metal supplier.
and with regards to gearing your axe down, calculate the gearing that you need and then we can better advise on what would be the best method for gearing.
will 10mm be thick enough sounds very thing to me?
id go for some of the stuff i have on offer to you that way you will make sure there will be no problems
For a featherweight 15mm wide box section is fine if you go for a 2mm wall thickness, 10mm may be a bit thin yeah. If you are planning on taking on spinners then I wouldn't look to use a box section chassis but for non spinner fights it will be more than enough.
Hi again not got anything really done over the last few weeks am busy with university exams... my finals :( but am just having a bit of a break.
Ive come to a bit of a dilema with my robot as in I want to start making it out of metal but have a few dilemas. Main dilema is that I need a welder and dont know wether to go for something like a cheap and chearful arc welder that will probably set me back £80ish pound after all gear is brought or wether to go for a DIY mig something like the clarke 90 with gear and gas would probably be around £300.
Also is a box frame the way to go or is there a better way to do it?
a box frame is a great cheap and easy way to learn welding etc
you can also make it all out of bulkheads, i.e sheets put together like a jigsaw puzzle then weld or bolt
might be easier to advise if you post a picture of the frame you wish to make
alex
sorry to hijack your thread, but where did you find the wheels that you used for the axe? ive look everywhere and cant find ones made from metal.
Team xtreme sorted me out with a couple from a job he was doing not sure he will have any more though im affriad ><
Ill see what I can find for you.
If not these might do?
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
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
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.
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?
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)
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?
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.
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?
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 :rofl:
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.
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!Quote:
Originally Posted by zoll
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 :lol:
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.
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?
Kenny at ALK Engineering - look in the commercial section, or email him at kennyrobotics@hotmail.com - is the go-to guy for robot builders round here; he does top quality work for a pretty reasonable price.Quote:
Originally Posted by zoll
Design something, draw it up accurately (CAD or otherwise), and have a word with him :)
Im rubbish in CAD so going have to attempt to do it by hand I think, Not quite sure how to attach the axe to the final gear, wither to attach it directly to the side like I have done with the spocket, or whether to try and get something like this done. Before I put too much more thought into it does £200 sound about the right ball park?
In the process of contacting kenny, had a first respone back but since that nothing for a while. Hopefully ive not put him off with my lack of design speaking of which anyone fancy designing it?
Depends what your after i could have ago if you wanted
kenny might be away on holiday ???
hes usually on msn be easier to talk to him that way
Its been a while so I thought I'd update, I'm starting my first real job next monday so hopefully will have a bit more then my students pennies to spend. (Have also just moved to farnborough for my job, anyone in the area?)
No luck with the gearbox from kenny think he must still be making 180 ( which looks amazing).
So i thought I'd move onto another bit that I want to upgrade... batteries, think I want to go with some a123s how many would I need and in what configuration would I need to power a 24v scooter motor and two 18v drill motors. Also anyone making a suitable pack that I can buy lol. Also also recommendations for a suitable charger?
Finally I think farnborough college does night welding classes which I think might be useful so I can start to work with metal
As always thanks in advance