elobire's build thread

[RogueTwoRobots]

Re: elobire's build thread

That's a ratio of 5.6:1
Quite low I would have thought for an axe but it depends on what you've got to work with sprocket-wise I guess. Depending on sizes etc you could get quite a ratio increase by changing the 12 tooth sprocket to a 10 tooth (6.8:1) or 8 tooth (8.5:1) but that's just me thinking out loud really. If you're happy with how it performs though with the lighter head (by what you've said, the batteries seemed fine) then that's okay.
Don't worry too much about what I said regarding levers. Again that was me mainly thinking out loud; I'm not even sure if what I said was 100% right

[elobire]

Re: elobire's build thread

That's a ratio of 5.6:1
Quite low I would have thought for an axe but it depends on what you've got to work with sprocket-wise I guess. Depending on sizes etc you could get quite a ratio increase by changing the 12 tooth sprocket to a 10 tooth (6.8:1) or 8 tooth (8.5:1) but that's just me thinking out loud really. If you're happy with how it performs though with the lighter head (by what you've said, the batteries seemed fine) then that's okay.
Don't worry too much about what I said regarding levers. Again that was me mainly thinking out loud; I'm not even sure if what I said was 100% right

what you said helped me understand what im doing a bit more actually.
im quite happy how it performs at the moment, although the chain keeps coming off, but i think thats because my brother sprayed WD40 on the chain and sprocket, along with the chain being loose.

also im going to have to redesign my robot slightly and have the wheels on the outside. i think some of my designs where a bit hard to built anyway.

[joey_picus]

Re: elobire's build thread

You definitely want to make sure the chain is properly tensioned - what sprang to mind when reading that was ORAC, which had either no tensioners at all or improperly tensioned chains, with the result that they both fell off against Killertron (and then a certain amount of fire ensued)

I think people have used skateboard wheels as tensioners before, or failing that just a small sprocket on a sprung arm would work.

[elobire]

Re: elobire's build thread

got some images of the robot so far.




will post a video of the new axe when i upload it.

also their is a problem with the chain, for some reason the sprocket isnt straight, this is causing the chain to jam and be looser when the axe is back.
the chain has only came of once, but i think thats because its hitting the motor mount and knocking the chain off. the drive sprocket also came off so had to refix it.
also the motor doesnt seem to be able to lift enough to flip my robot if its flipped. so il eventually buy a new motor and axe (think the handles causing the problem). il also be able to get a motor with the sprocket on it, i think that may be causing a few problems.

[elobire]

Re: elobire's build thread

just uploaded the video.
you can see how the chain has some problems, i think it may be caused by the axe handle which the sprocket is mounted to being thicker at one end than the other.
im considering changing the axe for a axe with just a spike at the end, anyone know if this would be better?
http://www.youtube.com/watch?v=rBIKSG9YY1M


EDIT:
was thinking of something like this for the axe:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... ink:top:en

[RogueTwoRobots]

Re: elobire's build thread

That second video is very impressive Ayrton.
Is the handle being wider at one end the reason for the squint sprocket? If so, try putting a spacer (a couple of washers or a piece of material with a suitably sized hole in it) between the sprocket and the narrower part of the handle to fill up the space. This should make your sprocket straighter and hopefully reduce the chance of the chain jamming and/or coming off.

[widow_twanky]

Re: elobire's build thread

I'd suggest you try taking some links out of that chain before anything else. It seems to 'droop' when it's sat in place. Fine for bikes but all the chains we have (hydras and SMIDSY's drive) have chain tensioners and guides.

A chain tensioner is either an idler sprocket which you fix onto an adjustable arm to push the chain tight or you can use a piece of HDPE/nylon 6 bolted to an angle where you can move the HDPE up and down.

The chain doesn't need to be mega tight but does need to avoid the amount of slack you can see in the video whilst it operates.

Guides on the sprocket may also help. Nothing special but you can cut a piece of 3mm ali and bolt it to the sprocket on a spacer which will help the chain 'feed' onto it.

[Metal Demons]

Re: elobire's build thread

Your chain is way, way too loose!

[rallikas]

Re: elobire's build thread

You can try a spring loaded chain tensioner. Im using this kind of setup in my buggy, and its the best choice, in my opinion.


Something like this:

[elobire]

Re: elobire's build thread

i think it is the handle making the procket out of place, but i cant seem to get it go straight if i add washers to it. going to take a better look at it tommorow.

also whats the best way to remove links from a chain?

[daliad100]

Re: elobire's build thread

A chain breaker and master link (?) to push out the pins and then reattach it.

I would still go with a tensioner because it's easier and probably faster to adjust tension.

Edit: if there are two bolts connecting the handle and sprocket, try different amounts of washers on each or cut some stand offs from some tube that can fit over the bolt flat at one the sprocket end and handle shaped at the other.

[elobire]

Re: elobire's build thread

A chain breaker and master link (?) to push out the pins and then reattach it.

I would still go with a tensioner because it's easier and probably faster to adjust tension.

Edit: if there are two bolts connecting the handle and sprocket, try different amounts of washers on each or cut some stand offs from some tube that can fit over the bolt flat at one the sprocket end and handle shaped at the other.

thanks,
the problem with a tensioner might be that the chain seems to be tighter at certian points because of the sprocket. i think il sort it out and see what its like.

[RogueTwoRobots]

Re: elobire's build thread

If the chain is tight at some points and loose at others, it sounds like your sprocket is not concentric. In other words, the hole in the middle of the sprocket that the shaft goes through is off-centre. The best solution without re-making/re-drilling/re-whatever the sprocket would be the spring-loaded tensioner idea mentioned above. That way, the tensioner can move to take into account a variation between slackness and tightness while still keeping the chain tensioned.

[elobire]

Re: elobire's build thread

i will probably fit a sprung chain tensioner to stop the chain coming off.

also i doubt i will get much work done within the next 2 weeks or so because iv started sixth form and its going to be caotic for a while.
oh and i sent my receiver/transmitter away for repairs and i havnt even received an email from them yet, odd perhaps they will repair it before emailing me

[elobire]

Re: elobire's build thread

little update.
i just got the reciever back, it workes perfically.

also the one wheel seems to be wobbling, going to take it off and see if its the motor or the wheel.