same and the gave good speed on a 7.2v nicad so 11.1v lipo will be interesting
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same and the gave good speed on a 7.2v nicad so 11.1v lipo will be interesting
Lots has happened here today on the robot front. I'd like to say there's been a lot of progress but it feels like its been one step forward one step back all day.
Initially it was going quite well, with the first motor mount made:
http://lh5.ggpht.com/_Z1kYQvize5o/TO...125_103908.jpg
All good so far :) Next I started making the other three motor mounts. After the second one the blade started melting the polycarbonate rather than cutting it. I didn't notice until I'd got to the last one :-( I've no idea what had changed; maybe the blade just started heating up. I'd been using my Dremel with a sanding drum to clean up the inside of the holes so I didn't think it would be too much of a hassle to sand away the molten plastic as the part still looked intact. Unfortunately my only sanding drum ripped as soon as I started sanding it :-(
Taking a break from the cutting and sanding, I next started modifying the motors. I knew I didn't want to use the standard mounts they came with so I took one apart to see if they'd work without the mounts. From a quick inspection of the 250:! gearbox it looked like they would work fine :) but I'd have to add some washers.to keep the correct motor/gearbox spacing and stop the gears from binding. I then spent ages looking for suitable washers before deciding to make my own. It was only later that I noticed that the 15:1 gearboxes for the drive didn't need washers as the gear spacing was different. Here's a modified gearbox with M3 nuts used as spacers and the micro deans connector soldered on:
http://lh6.ggpht.com/_Z1kYQvize5o/TO...125_224046.jpg
So after the first one worked :) I disassembled, removed the mount and reassembled the other drive motors. That went ok except I found that afterwards one of the motors didn't spin freely. nothing looks bent but it doesn't turn when I apply 12 volts to it :-(. It was also at this point that I realised that whilst I'd bought spare motors, they didn't come with pinions and I haven't got a gear puller :(
Can anyone recommend a suitable gear puller for removing the pinions off 280 size motors?
After numerous other attempts at making a decent round hole, I finally figured out I could use my router to make the holes, eliminating the sanding. Here's the result:
http://lh6.ggpht.com/_Z1kYQvize5o/TO...125_182219.jpg
:) Nice.
I thought I'd mount the frame rails to the armour (one piece wrap around 3mm polycarbonate according to the design) before deciding how to arrange the wiring. I cut the armour out with scissors and noticed it was probably a little too thick to just bend around the frame rails cold, so I started heating it up whilst bent:
http://lh3.ggpht.com/_Z1kYQvize5o/TO...125_193103.jpg
It was going ok until I got a little lazy, didn't keep the heat gun moving enough and overheated it, causing lots of little, weakening, bubbles :( It'll do for now but I've since decided that it would be a lot easier to work on if the armour was in four pieces anyway.
Here's the assemble:
http://lh6.ggpht.com/_Z1kYQvize5o/TO...125_223657.jpg
Not too bad but the armour's a bit of a mess and the wheels don't all point forwards :?
With it assembled I then started soldering the wiring harness:
http://lh6.ggpht.com/_Z1kYQvize5o/TO...125_223802.jpg
Again, not perfect but everything's insulated and secure, or so I thought...
I connected it up to the motors and twiddled with the receiver. Everything worked! :) Ok the channels were the wrong way round but that was an easy fix. But after I crammed the electronics into the armour, I heard that dreadful sparking noise and a slight smell of magic smoke when I plugged the battery in, plus the blue light of the speed controller went out :cry:
I removed everything from the bot, laid it out and checked for shorts. Nothing I could see. So I plugged the battery in again. This time the blue light came on and one motor started moving, but almost immediately there was another noise, the light went out and the motor stopped. Even when I disconnected all the motors the speed controller's light still won't come on when powered up :-(
On the plus side, I weighed everything I've got so far, and, according to my crappy scales, It's 50grams lighter than the cad model predicts :proud:
Not sure what to do tomorrow though....
Wow, you're right. For every good thing that happened, there was a setback hiding round the corner to kick you in the nuts.
If it's any consolation though, what you've made so far looks great. It hopefully won't be too far off before we have the first beetle battles :)
Progress!
Things seemed to go much better today. Here's the robot as it stands:
http://lh4.ggpht.com/_Z1kYQvize5o/TP...126_234557.jpg
Total weight 940grams.
Still to do:
* Side armour
* Side pods to support the weapon motors and mount the side armour to
* Get the bloody electronics into the body without blowing them up
* Replace the aluminium test scoop with a steel one
* Centre section top and bottom armour
* Wire in a removable link
* Decide on a name
Weight is still looking good so I might remake the armour so that its a bit bigger to aid getting the wiring in. Making the armour in four pieces is definitely the way to go - its much easier to work on the robot with just the front and back armour on and its easier to make.
I didn't spot anything that could have caused the speed controller to blow up yesterday. Further testing today confirmed its definitely dead. Is there anywhere I can send it to get it fixed? Its a Dimension Engineering 2x10. Luckily the one I ordered as a spare turned up today so I could carry on building and testing.
The only hiccup today was when I tried to get the Pololu Simple High-Power Motor Controller (weapon ESC) working. Despite it being called Simple it's the most complicated speed controller I've ever used! I had to install drivers on my PC, plug a usb in and then configure it before I could get it to do anything. The configuration utility is actually very good. You can set the zero point, dead band, etc and see what RC pulses it's seeing. There are also various fault states that will cause it to shut down to protect itself, and you can monitor them and set the fault trigger level. It turned out that my original issue was that it was set to serial mode.
Anyway, here's the test video:
http://www.youtube.com/watch?v=7ESMD-ta21s
The lifter's really fast and the nippy drive train makes it a blast to drive! I've really enjoyed pushing cardboard boxes around and chasing the cats.
I'm now feeling more confident that I CAN get it in an arena. The question is: Is there an arena for it to play in? What's the current plan with the beetles?
ok, it's now 16 years.... I've not giving up though.
I'm still working on the same basic beetle design. here's where I've got to:
http://youtu.be/IFppiqhwzJ0
(the bot weighs 900g as it is, the box weighs ~1.7kg)
http://youtu.be/cTKPTED1fo0
I've now got access to a 3D printer, and occasional access to a mill and CNC router, so I'm prototyping with the printer, then will remake in polycarbonate/titanium. So far the 3D printed parts have fit together well and I think the basic design is sound, but there's a few things I need to fix:
*The belt drive for the lifter slips too much and is too stretchy. I need to change it to a reinforced belt, or a small timing belt or chain. Any suggestions?
* the press fit pulleys/wheel hubs keep slipping. I guess I need to add a grub screw or glue them
* the trims seem to drift with time. I couldn't get Elevon mixing on my DX6i to give me full speed forwards, so I'm now using an onboard mixer. With both setups though, the trims seem to move over time. I got the trims set up before the above video, but by the end it was creeping backwards when it should have been stationary. I've never seen this before. The receiver is an orange r400 and the ESCs are botbitz 10A.
* The only bit of the bot that gets hot is the ESCs. The motors are the ebay 1000rpm gearmotors with one 10A ESC per side. Do people use one ESC per motor or is one per side normally ok? I'm worried that arenas might be grippier than my kitchen floor, increasing the load on the motors and ESCs.
When's the next beetle event?
At this point I'm tempted to just put the 3D printed version in the arena, just to get experience and see what breaks!
Neat design. Polycarb might not be the greatest idea. Maybes look at nylon, UHMWPE or HDPE.
HTD 3 timing belts are nice things. You can get them from belting online. If you need any 225 belts let me know I have more than I can ever use. Or the green belting stuff seems pretty decent.
For a hardcore driven bot, I'd go for 2 30a botbitz or one 10a per motor. Some people use 10a for 4 or more motors but they aren't driven in anger. Or just heatsink the shit out of them and keep fingers crossed. You running 4s?
If you put the printed version in the arena... I think the printing will break and you will have an exploded robot. Won't tell you very much about the designs strengths.
Thanks.
I need to look into those other plastics. I just happen to have a load of polycarbonate, but I am worried it will be brittle after machining.
What sizes of timing belt do you have? I'd like to keep some slip in the design, so I'll have a look at the green belting. I'm not sure how stretchy that is though. I might have to do a Gene and use a v groove on one part and timing teeth on the other pulley to still allow some slip.
I'm currently running 3s, so not even overvolting the motors. I thought I'd heard about people running one 10A per side, and the motors should only be ~6A stall, so I thought I'd be ok. I'm just looking now if I can squeeze 2 more ESCs in there. I think they'll fit, but wiring will be tight.
Hdpe is what I'd go for. I don't really trust Polycarbonate unless it's for shock mounted armour panels - maybe that's just me, but it does seem to crack unlike HDPE or nylon which just chips or bends a little. Also I recall HDPE being a tiny little bit lighter than polycarbonate too so that's a thing that might be useful.
Avoid using polycarb if you can it's not really up to the task anymore, i used a piece that was 10mm thick for the baseplate of my Feather and one relatively low speed hit from a spinner shattered it into 3 pieces. I'd go with Hdpe for sure, nylon if you can afford it but it is by far the more expensive option.