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It may be better with a end support, can you get a bearing which the bolt head will fit into and drill a piece of aluminium and mount to the base, i think the problem you have is the sprocket drive is trying to pull the smaller sprocket, support it so it can't get stress on sideways movement should solve it
It has had a support on the other side of the sprocket since we started. That picture from a few posts ago is old, and doesn't show it. We have been super careful with the bearing, knowing the stresses involved could quite easily destroy it.
I'm off to once again dismantle the side of the robot (at least it's fast and simple, might take 5 minutes if I take it easy), as apparently dad has just bought goodies from one of the B&Q-type places down here that may help this.
We're not back to square one, quite, half way back perhaps but not all the way. I'm going to think about ways to avoid cottering (that should be a word, along with cottered!) all the way through the material and instead a little way from each side. Twice the failure point has been (as you'd expect) where we have drilled all the way through.
As well as that, we're going to turn the torque required to activate the limiter down.
I'll keep this updated throughout the day. Thanks for the comments and help.
Edit: and incidentally, the rest of the machine is working nicely. Famous last words, perhaps, but the drive rig as a whole, batteries-thru-speedos-thru-motors, is showing positive signs. The previous machine didn't get this amount of drive testing.
Any luck with the repairs?
As a last resort I'd suggest you ditch the reverse thread screw you're using, its too small at 1/4 diameter. A bigger diameter bolt will be much stronger. All you have to do is drill the sprocket, and drill shaft to a bigger diameter, say 5/16 (or 8mm) Buy an M8 or 5/16 24UNF taps and cut a thread in the drill shaft. Then lock all together using an M8 or 5/16 high tensile bolt. Then use a 3mm roll pin to cotter all together.
Can you post a pic of the problem area and the parts in question?
The reverse thread bolt we have is no longer in use due to a slight technical issue, by which I mean it's in two pieces. :P
And, we can't use a bigger bolt because the bore of the sprocket can't be any bigger!
We're really stuck. We're rebuilding it as we had it last night, and we'll set the torque limiter low. We don't have time for anything else. At least, we hope, it will work visually, it just won't be able to lift much before the limiter kicks in.
I'll post pics of the final setup tonight, assuming it doesn't break for a 4th time. We have decided to try and fill any gaps that will allow slippage (and thus enough momentum to break again) with solder. The alternative would be glue, so this works.
the amount of torque going through that sprocket, glue and solder wont do anything. I would really try and get it welded, its the easiest way without having access to a full machine shop.
We know, yeah. :|
Well, we'll build it so that it works nicely below major stress, and leave it. Discussing the potential of Mario welding it for us at MMM.
May just move the weak point to the next thing (gearbox?) which will probably be more expensive!
Agree...solder not going to help much, adhesives - depends, I've used adhesives which stick to metal like welding, but I doubt you have any access to those...I'd go with welding as said above. if you don't have access to welding I cant see any way out if not by up sizing the sprocket hole ( looking at the photo below you have more than enough space for that)
http://i1088.photobucket.com/albums/...2062012427.jpg
We could potentially up-size the hole by a mm or two (has been drilled out since that picture) but we're reluctant having experienced the power involved.
Well, Mario has extremely kindly offered to help. We think making it to the House of Chaos shouldn't be too difficult, in which case we'll have at least one skilled person leaning over the thing who will guide us. If he thinks a bigger hole is necessary, may a bigger hole be drilled!
I have a feeling he intends to just weld the buggery out of it, though. :P
We'll build this, avoid breaking it, be happy, and let Mario do the thinking if we can stop by. :lol:
good to know you found someone to help you out, it would have been a pity if it didn't work 100% after all the effort put in this build!
Have fun :wink: