Tormenta 2 - Build Diary

It has been forever!

We had intended to start getting back into gear before Christmas. Unfortunately Dad has been occupied with work, so things haven't moved. Until today, a little bit.

I took T2 out to the workshop after having had it sitting under the coffee table for several months, and started looking at the immediate issues left after MMM and Maidstone.

The main forks could move independently by about 5cm at the tips, and the sprocket seemed to have a similar amount of play in it. The result was huge looseness in the setup; the shaft could do, I'd say, an 8th of the full motion, without the forks even moving.

Happily it wasn't that the shaft (just a mild steel 20mm threaded rod) had been worn away by the M6 cotterpins we used, or God forbid twisted, it was just general looseness, so I tightened everything up. Also the little M6 bolts we used like setscrews to hold the sprocket to the shaft had worn away where they tighten to it, so the sprocket's play was from there. I replaced them with some stainless bolts that will hopefully last longer. It's all still a bit rickety but I'm happy.

Not really a lot to report, but it's significant because we (hopefully) won't have to do any major rebuild work to T2 before we move on to robot nºmero 3. Especially since April is suddenly just around the corner and we have yet to go beyond CAD with our concepts. I feared this shaft looseness was something much more sinister.

Other issues with the robot are a bit of the left bulkhead cracked off (odd for HDPE?) at MMM, which we will attempt to weld back on. We still need to sort the gearbox reliability, not sure how yet. There is sometimes a slight lag when going full forward/backwards then suddenly slamming into a turn. It lasts a few seconds, like the link between the tx and rx is delayed, then clears again. We think it's the rx aerial, so it should be simple to fix. I think that is pretty much it. I doubt there will be many additions before April, though I'd love to make the weapon act like a servo.

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Christ did I just write all that?!^ All I did was tighten some stuff!

Thats looking good, its a nice bot. And I was looking into a system (which is completely different but uses a similar set up with the shaft) but feared it would have bad twisting, which would be a problem with our design would jam if it twisted. So if your having twisting issues im gonna have to have a re think about how Im gonna do it. yours looks cool, would be cool to see how it preforms in battle first hand.

Ah well, we haven't had any twist issues. No signs of it, either. We will be taking T2 to the UK for the champs, which will put it through its paces, but I am confident the weapon setup will last. My biggest fear is horizontals (with our luck we'll have NST from the get-go again) completely removing it...

Better drive now though, the get in before they can spin up tactic is a little more plausible, I guess.

Look forward to seeing what you build!

With the drive you have now you should beat just about everyone from a standing start, so getting in before spin up with most should be possible. [Not Conker though, did a quick test a few weeks back and it gets up to the full 4500 rpm in less than a second, and is at 6000 in under 3.]

Side question: When you ordered your 85A ESCs from Botbitz, how long did it take for them to arrive?

Argh crap! Upload videos do want do want! And yeah the thing launches into speed, the problem will be aiming it before going full throttle fast enough to make it count.

The ESCs took quite a while. I think it was just under 3 weeks. There were several bank holidays at the time, though, and postage to Spain is always a bit interesting. Botbitz say there postage generally takes from 8-12 days, so we were a special case.

Hi guys, we're going to make our own wheels, and before I buy the wrong things, can I buy any 3/8UNF size nut? It would seem there are loads of slight variations, am I safe with anything labelled 3/8UNF?

I am looking at these (or similar) in particular: http://www.ebay.co.uk/itm/3-8-UNF-25mm- ... 5891b47a4b

Thanks.

lol they look familiar

i was using these
http://www.ebay.co.uk/itm/3-8-UNF-Femal ... 3cc8b87228

but im now using these

http://www.ebay.co.uk/itm/5-X-3-8-UNF-B ... 415b3c8afa

and this lot work out cheaper
http://www.ebay.co.uk/itm/3-8-UNF-x-24- ... 27c7eb7d75


but i found you either need to drill the wheel bore to 13mm to hammer them in or heat it up first and force it in or it will split the wheel

heat up the nut, I used a 150w soldering iron for the job and left the nut on the end for 5min or so, then press it into the middle of a wheel that has been drilled out. 13mm should do the job fine.

The thing you have to watch is that you get the nut in straight. If it's even slightly off then your wheel will wobble.

Once pressed in, I'd use the iron to cover over the nut to keep it captive within the wheel.

Yes, we're going to make up a jig with the drill press, which should hopefully keep things straight. Or straight enough, anyway. We have a heatgun, which should be easily powerful enough.

The bore of the hubs we have is 12mm already, if we can manage to get the nut in without having to drill out to 13mm (happens to be a size I know we don't have) then that should further maintain alignment.

My question was just to ask if any old 3/8 nut will do.

Thanks for the links, Peter.

as long as its a right hand thread and it says 3/8 unf then it should be