Team Thunder- Theta (FW) 2WD rambot

[firefly1]

Got things together to build my second featherweight robot, the first i've built from scratch. I'm using a frame bought from @danjr1 a while ago.
Since this is for a school project and time is tight the robot will be a simple 2 wheel drive pushbot!
(all photos so far are here: http://imgur.com/a/bBCZv wasn't too sure how to post them straight to the forum)
Frame is of HDPE construction. Armour will be HDPE and mild steel for the front wedge.
The motors powering this robot will be speed 900 replicas with Botbitz 85A ESCs
Will be updating this thread over the next few weeks as progress is made!

[Maxamuslead]

Are you going to be fabricating the steel into shape as it a school project or is it supplied by school?

If not look at HARDOX as it costs about the same and it way tougher

[firefly1]

I have the steel alredy at home and I was going to get it bent into shape at a metalworkers, hardox would be a nice future upgrade though!

[firefly1]

Quick progress update:

Everything except the electronics is pretty much done now and so far it's gone surprisingly smoothly (not looking forward to wiring it up though).
Hopefully these images will give you an idea of how the robot will run along the ground

http://i.imgur.com/qtbUygH.jpg
http://i.imgur.com/rNrM5SR.jpg
http://i.imgur.com/3hjTmLl.jpg

Wiring shouldn't take too long as lf I don't run into any major problems, after that all that really needs doing is to buy some bike tyre for the wheels!

[R9000]

Looking good! Those steel brackets are especially tough-looking. Where did you go for the spur gears?

[RogueTwoRobots]

Looking good! Wiring should just be a straightforward affair on a robot like that. Even so, I find the best thing to do is prepare for it to take half a day, if not more, get some snacks and drinks to hand, put some music on and take your time. It'll be a lot less stressful and if you have good wiring, that's one major reliability hurdle overcome

[firefly1]

@r9000 Thanks! got my spur gears from: https://www.gearsandsprockets.co.uk/...ur-gears.html/ I used the 90 tooth mod 1 spur gears

[firefly1]

@RogueTwoRobots Thanks for the advice! Planning to spend the weekend on it so should have enough time to take it slow and not mess up

[firefly1]

Update time and a quick question:
The wiring is complete and it moves!! - Was kinda expecting nothing to work and then to spend days troubleshooting
Other than that I packed out the inside with some Plastazote foam to stop things rattling around and cut up a bike tyre for the wheels. What I need to do now is to get some spikes/bars for the side of the robot to stop it getting stuck (Was thinking some stunt scooter pegs would do the trick: https://www.amazon.co.uk/Scooter-Peg...ode=3734092031).
Anyway here are some pictures:
http://imgur.com/KnPjSmt
http://imgur.com/WZ1i1oI
http://imgur.com/Jw4v6p0
I was just wondering that if I ran LED strips around the inside of the wheel holes would that satisfy the active light rule or should I just poke a bright LED through the HDPE at the back of the robot?

[R9000]

Honestly, I think you'll see the LED strips through the HDPE, but in any case, as long as you can clearly see them through the wheel-holes, it should be sufficient.

[firefly1]

Okay thanks

[firefly1]

Questions
I'm having a lot of problems with the pinion gear welds on this robot breaking where if i go above about 50% motor power the welds just give up (pictures below). The first thing I tried was to drill out the grub screw and re weld it as a second point of contact which didn't help at all. I then realised my welds were probably really crappy and took the motors to get re welded professionally which again didn't help.
I was wondering if people have a different technique when attaching pinion gears?
or if the motors I'm using are purely just too powerful?
Thanks a bunch

[Outlaw]

It could be problems with the axle of the motors themselves, as they look a little mauled, if they're just breaking off. If I was to make a small suggestion, try getting them keyed, or replace the axles if that's even possible.

[RogueTwoRobots]

Those shafts are too small to be keyed, and the welds won't be holding because they probably won't be getting good enough penetration. Best bet would be to file (or angle grind, file could take a while!) a flat on each shaft so that the grub screw has a better surface to grab on to, but then also use some fast setting epoxy between the pinion and the shaft at the same time. With the flat on the shaft, there is a little more space for a bonding adhesive to contact both the shaft and the pinion, potentially leading to a stronger and suitable joint.

EDIT: misread that you drilled out the grub screw. If it's possible to tap the pinion for a bigger one, fine. If not, maybe not file a flat on the shafts, just rough them up a bit and use the epoxy. The rough surface will provide a better surface for bonding. The epoxy will also flow into the hole where the grub screw was so would give an extra contact point.

[firefly1]

okay thanks! will be definitely doing this asap @RogueTwoRobots and hopefully competing very soon