Help with Axles and where I could find such a thing please?

[Outlaw]

Hello all, might as well throw myself out there.

Been a long time Robot Wars/Battlebots fan, watched it since I was young as heck, and was absolutely bummed when I heard that there wasn't going to be an 8th series of RW... Until now, haha!

Me and my friend have been planning on building a heavyweight robot, just to see where it gets us if anywhere. Before you ask "Why not start with a smaller robot?" We'd just find it way too fiddily to work with, especially where the space is really confined.

So, to the question at hand. We plan on making a four wheeled pushing robot, that can be invertable and take hits on the front from spinning discs, bars, etc etc. We have the motors, bearings, bushings, R/C controller, the speed controller and batteries all thought out, written down, planned out and such... but now the problem is that we have no idea what material the wheel axles, the motor axle and the idler axles should be made out of or where to find such axles, so a nudge in the right direction would be fantastic, along with any other advice. We plan on using 3/8" pitch pilot bore sprockets from the BearingShopUK along with some shaft collars too.

Bonus points if we could possibly source it from the UK as well, because with the most expensive part being form the US, it'd be a major pain in the buttcheeks to get more items shipped over from there.

Thanks and much love.
DJ.

PS.: We don't have any access to anything to do with CNC or digital designs to get the axles, unfortunately. Just a couple of drills, a hammer here and there and the local garage to see if they could help us with the welding. :P

[typhoon_driver]

For cheap easy to get material for axles you should probably look at silver steel. Many suppliers of it all over the place and it's not expensive. A quick ebay search,

http://www.ebay.co.uk/sch/i.html?_fr...steel&_sacat=0

I would recommend increasing the bore of the sprockets as a 3/8" axle would bend very quickly in the heavyweights.

[craig_colliass]

Hi and welcome
I don't use CNC or CAD either and still have fun making robots.

If you haven't made anything like this before then I would advise going to a live show, and get to talk to people in the pits and look at what people are doing with the current robot designs, there are shows on in Reading this weekend
A lot of questions you have could be answered there, also it may motivate you to finish the project once started when you see the other robots in action.

[Mouldy]

picture's speak 1000 words- post images of what you have so people can help you.

Also, i learnt mostly by reading others build diary's... a great one to start with for you would be the tornado page;

http://www.teamtornado.co.uk/

[Outlaw]

Hello everyone, DJ again.

Thanks for the help. Hopefully some of the advice on here would help.

As for the size of the axle, I'm thinking about (quite possibly overkill here...) going for 7/8" axle thickness. But if this proves to be a little overkill, we may tone it down to 1/2" or 3/4".
The sprockets will probably stay at a 3/8" chain pitch, but we may go for duplex sprockets to see if that'd help for reliability purposes. My mind says it might do, but my gut says it might not...

Speaking of which, I have little to zero idea on how to mount said sprockets and wheels to the axles, especially if I want the robot to be primarily a push-bot/spinner killer. Which means power and armour first, weapon as an afterthought, but I digress. As said before, I have no access to CNC or CAD, or any drilling/proper cutting platforms so to speak, so any way apart from the key and keyway technique would be fantastic. I looked up something called "Trantorque" via the RioBotz combot tutorial pdf, but I'm not exactly sure how this'd work seeming as I haven't seen any tutorials that show people mounting a wheel or a sprocket to said axle. I'm also not sure how much they'd cost either...

I also have a couple more questions to ask but it'd probably be better if I start working on a prototype, and ask then. I've got wood and MDF in the shed to start off with (and a hot glue gun and nails), especially with the chassis, but the MDF will most likely be used to get a general shape for the drivetrain protection/makeshift gearbox/gearing... I'm not exactly sure what to call it to be honest. Once I get that down, with all the markings, I'll either take pictures and post them up on a blog, say... tumblr, so that I don't swamp this place with unnecessary twaddle, or I'll attempt to get my camera to film what I've done that day, almost like a diary, so to speak.

As for going to a live show, I went to one a few years back, and it was awesome. I believe it was a bunch of either lightweights or featherweights, and one bot stood out from the crowd, as it looked like an I shape with a spinning bar underneath it. I believe it was from the creator of Scorpion but I genuinely can't remember, so I might as well be talking out of my backside. But as I said, it was a few years back.

Once again, any input, feedback, etc. would be extremely appreciated. Fingers crossed I can get the pictures/video out sooner rather than later.

[typhoon_driver]

KEEP THE PICTURES AND BUILD DIARY HERE! Inevitably, there will be someone else in your position in a year or two asking the same questions and it's always more helpful to have a lot of build diaries to refer them to.

7/8" axle is about right. You wouldn't want to go much smaller anyway. As to connecting the two there are a number of options, some people weld sprockets and gears straight onto shafts, you can drill straight through the sprocket and shaft and put a pin or bolt through, there are various clamping systems available or keyways as you mentioned.

I remember the feather you mentioned and it was built by John from Scorpion. Had a perm 080 motor if I remember right.

[Outlaw]

Hello again everyone. Had to do some remeasuring (just only for the sprockets and this "gear-rectangle" I guess you could call it, haha.), and tomorrow I should be heading over to my grandparents, to work more on the prototyping of said rectangle. So that should come along more swimmingly, as my grandfather used to be a woodturner/woodworker, and now does woodturning for a hobby/side job.

As for mounting the sprockets to the axles, I turn to what Gary said, with drilling holes into both the sprockets and axle...

7/8" axle is about right. You wouldn't want to go much smaller anyway. As to connecting the two there are a number of options, some people weld sprockets and gears straight onto shafts, you can drill straight through the sprocket and shaft and put a pin or bolt through, there are various clamping systems available or keyways as you mentioned.

Turns out the keyless bushes were way too expensive... But I had read in the Riobotz pdf somewhere that screwing in the sprockets into the axle with screws is a bit of a no no... is that only with the grub screws that bearingshopuk supplies? Or does it apply with all the screws? Because from what I could understand is that it could act as a mechanical fuse of sorts without the need for CNC. A downside is that it could end up breaking inside the shaft and making it a huge pain to get out of the shaft itself?

Any insight would be phenomenal.

DJ.

[harry hills]

Set screws suck is a bit of a universal. However you can make them suck less. Flats on the shaft and large grubscrews relative to shaft size will help them be adequate.Its sub optimal but it does work. Look at keyways. Much better. Then just use grubscrews to retain. You can even weld if thats on the table.

Im not sure what you are on about trying to CNC a shaft. You're not trying to do anything you cant do by hand from what I can make out?

[Outlaw]

Hello again everyone.

To answer your question Harry, I have no access to CNC at all, so cutting out a keyway accurately is practically a no go for me, unless I can find a service near me (Sheffield... funnily enough, should be easy considering that it used to be the city of steel... still is but I don't know...) that can make them for cheap (yes I know, cheap and robot doesn't exactly go well together, but 101 only cost a pound and a penny... probably coz Mike Franklin had some CNC stuff with him, but I digress once again.). As for welding them on, I would like to be able to remove and replace sprockets and/or axles if things go awry, so welding them is also a no go.

Unless there's a way for me to accurately make a keyway and key by hand, then more than likely it'd end up with me using screws.

NEW QUESTION, and it's back to the shaft so to speak... jesus I need to really think my words out when typing this up...

So I've been hunting around on bearingshopuk for the silver steel axle, flanged oilite bushes and the sprockets, the sprockets I've already made my mind up about, along with the bushes. The question is, will a flanged oilite bush to this size (7/8 inch bore) accommodate a silver steel axle (22 mm diameter) this size without it all shaking too much, and will it be able to keep the bush in place so that it doesn't come out in the middle of testing/battle? Or will I have to find another silver steel supplier that does it in metric instead of imperial?

Don't worry, both links go straight to bearingshopuk. Should do at least anyway.

Thanks again.

DJ.

[maddox10]

22mm silversteel is a standard size.